Agricultural waste mass balance: Opportunities for recycling and producing energy from waste technologies

Transcription

1 Agricultural waste mass balance: Opportunities for recycling and producing energy from waste technologies

2 Biffaward Programme on Sustainable Resource Use Objectives This report forms part of the Biffaward Programme on Sustainable Resource Use. The programme aims to provide accessible, well-researched information about the flows of different resources through the UK economy, based either singly, or on a combination of regions, material streams or industry sectors. Background Information about material resource flows through the UK economy is of fundamental importance to the cost-effective management of resource flows, especially at the stage when the resources become waste. In order to maximise the programme s full potential, data will be generated and classified in ways that are consistent with each other and with the methodologies of the other generators of resource flow/waste management data. In addition to the projects having their own means of dissemination to their own constituencies, their data and information will be gathered together in a common format to facilitate policy making at corporate, regional and national levels. Care has been taken in the preparation of this report, but all advice, analysis, calculations, information, forecasts and recommendations are supplied for the assistance of the relevant client and are not to be relied on as authoritative or as in substitution for the exercise of judgement by that client or any other reader. Neither C-Tech Innovation Ltd nor any of its personnel engaged in the preparation of this report shall have any liability whatsoever for any direct or consequential loss arising from use of this report or its contents and give no warranty or representation (express or implied) as to the quality or fitness for the purpose of any process, material, product or system referred to in the report. All rights reserved. No part of this report may be reproduced or transmitted in any form or by any means electronic, mechanical, photocopied, recorded or otherwise, or stored in any retrieval system of any nature without the written permission of the copyright holder. Credits C-Tech Innovation Ltd wishes to acknowledge the contribution made by FEC Services Ltd in the compilation of this report. For further information about the work of FEC Services, visit their website at or contact: FEC Services Ltd NAC Stoneleigh Park Kenilworth Warwickshire CV8 2LS Tel: Fax:

3 Contents 01 Introduction Key issues 06 Policies and legislation The legal definition of waste 1.2 EU and UK Government policies 6.2 The position of agriculture 1.3 Energy use 6.3 European Union policy and legislation 1.4 Report objectives 6.4 National policy and legislation 1.5 Benefits of recycling and energy from waste 1.6 Legislation 1.7 The European approach 07 Mass balances The inputs The cyclical nature of agricultural production 08 Waste treatment strategies Relevant recyclable wastes 8.2 Single farms 03 Major waste arisings Deriving waste figures 8.3 Village schemes 8.4 Parish group or county schemes 3.2 Typical farm waste profiles 8.5 Regional strategy development 3.3 The geographical distribution of agricultural business and its relevance to waste 3.4 Major waste sources and production seasonality 09 Conclusions Recycling 9.2 Energy recovery 04 Focus on enterprise energy Main energy usage 4.2 On-farm energy-from-waste options 9.3 On-farm processing 9.4 Centralised processing 9.5 The future Improving efficiency Techniques for waste recycling and energy recovery Reuse, recycling and reprocessing 10 References Energy recovery from farm waste 5.3 Conclusions 5

4 Foreword Mass balances in agriculture, what next? For the past 200 years, society has become used to quantifying and understanding efficiency in two broad dimensions: efficiency related to labour or people input efficiency related to cost. Few have paused to think about the inherent efficiency of the way we deliver goods and services in terms of total resource inputs. Historically this was not worth bothering with anyway the environment is free is what we think. We can use air or relatively low-cost raw material inputs such as minerals, carbon or foodstuffs, but it is the application and conversion of those resources that is the expensive bit. We are now coming to terms with reality that profligate use of low-cost resource inputs has resulted in the introduction of large quantities of liquid, gaseous or solid waste into the world at a rate faster than the ecosystem can return it all to its original states. Consequently particularly in the case of carbon as carbon dioxide the ecosystem is using its own mechanisms to cope with waste output burdens. The consequences of this may not necessarily be cheap, as we are yet to count the cost. As a company at the heart of resource management in the back end of the economy, Biffa is well aware of the sheer volume of waste outputs in the economy particularly in solid form. This is at the heart of our business. Seven years ago, in an effort to predict and determine factors that may influence future trends for tonnage and composition of waste outputs, Biffa decided to start taking serious stock of how resource flows might shift in years to come. Studying resource flows is important to developing an understanding of the future transport and process technology implications. Equally, it is likely that, in the future, resource flows from particular regions or industry sectors might be mixed and processed alongside each other to produce new raw material inputs most commonly in the form of energy or recyclate feedstock. Such systems cannot operate on a small scale in a fragmented fashion as the true costs of handling society s pollution burden emerge, then the investment and substantial scale infrastructure to deal with it will be needed. In 1998, the government introduced the means by which we could fund our ambitious ideas in this area the Landfill Tax Credit Scheme. As a result, Biffa has been able to commit 8 million over the past four years to more than 40 sector studies that look at the dynamic within which different product supply chains handle raw resources and their waste outputs. Governments worldwide are taking more and more interest in utilising tax and other fiscal instruments to modify resource consumption or disposal patterns. It is important, however, that policies are developed within a framework where the facts are known and industry sectors feel comfortable with the timing, pace and focus of how taxes might be applied to modify supply chain behaviour. Nowhere is that more important than in agriculture, where such issues have never surfaced on the daily agenda. Most of us, for example, do not know that five kilograms of assorted resource, energy inputs and waste outputs go into every half kilogram of food we eat. Agriculture, therefore, can no longer regard resource impacts in quite the way that prevailed between 1950 and Funding this resource flow of the agricultural sector has enabled Biffa to help the industry understand and possibly anticipate future opportunities for competitive advantage as well as improved sustainability. As part of the mass balance suite of projects, it will inform a wider debate as to how society as a whole can reduce the overwhelming burdens our single species is placing on the biosphere. We hope you enjoy the journey! Peter Jones Director Development and External Relations Biffa Limited 6

5 Executive summary The agricultural sector is the UK s largest producer of waste materials. Compared with many other sectors, however, little study has been made of these wastes. This report is a comprehensive assessment of all waste arisings in the UK agricultural sector, and contains critical evaluations of energy-efficient processing techniques and technologies for recycling and energy-fromwaste applications. The writers intend to raise awareness amongst farmers, local councils and government officers of the issues involved in recycling and the energy-from-waste potential for the UK agricultural sector particularly as waste is often related to pollution. Moreover, they describe how proper use of agricultural waste will show substantial benefit in reducing pollution and the overall use of fossil fuels and could provide new jobs in the rapidly changing rural economy. Key objectives of the report are to identify and quantify the major wastes arising by region and type of business identify and quantify the major energy sinks analyse energy efficiency. A simple mass balance describing the inputs and outputs for each type of agricultural business is included in the report. Data on agricultural wastes are presented in more detail, listing each of the wastes produced by type of business. Organic waste, which is the major waste produced by agriculture, is also presented regionally and seasonally. Furthermore, this report identifies how recycling and energy-from-waste techniques can be used to benefit farmers and local communities, and describes opportunities for centralised recycling and energy-from-waste plants. Recycling and energy-recovery techniques applicable to the various wastes generated by agriculture are included. Some techniques are improved versions of traditional waste management processes (such as the composting of organic waste), while others are processes transferred from other industries and adapted for use with agricultural waste. Energy recovery is becoming increasingly important for agricultural wastes. Energy can be recovered directly through burning agricultural waste products, or indirectly through the collection of by-products (for example, methane from anaerobic digestion). Several options presented in the report show potential for commercial operation, some techniques in particular show great promise. Poultry-litter and straw burning technology is well advanced, and a small number of units are in operation in the UK, mainly in the east of the country. The preferred use for surplus straw is to fuel on-farm boilers for heating water and buildings, also for grain drying and other operations, thus cutting energy bills and avoiding ploughing in costs. This technology is viable even for standard-sized farming enterprises producing about 30 tonnes of straw per year. Anaerobic digestion is very attractive, but a concerted strategy is required for its introduction. Policy in the UK favours anaerobic digestion on environmental and energy grounds. However, the cost of anaerobic-digestion technologies restricts widespread implementation. For large farms, or for farms where disposal of livestock waste is a serious problem (for example, pig farms without sufficient associated land for spreading), anaerobic digestion is an excellent solution. If possible, the heat and power generated should be used on-farm, with any surplus electricity generated sold to the National Grid. Many county councils have recognised that renewable energy can begin to displace fossil fuels, which helps to reduce acid rain and climate change. These forward-looking local authorities now wish to encourage the development of renewable energy sources in their regions. This document sets out some options for county councils, including a methodology for establishing a regional strategy for anaerobic digestion. Denmark s experience suggests that to stimulate the sensible use of anaerobic digestion, legislation would be required to restrict or prohibit the spreading of agricultural waste on land, and that funding assistance would need to be made available for environmental protection and/or sustainable energy projects. No account has been taken of the large number of animals culled during the recent foot-and-mouth disease epidemic and the influence that this will have on waste production. Once restocking is complete, it is assumed that waste production figures will return to normal levels. Beef cattle have not been considered as major potential contributors to the waste resource, as they tend to be kept outside for a greater part of the year and are usually bedded on straw, which is not ideal for anaerobic digestion because it requires chopping before use. Similarly, sheep have not been considered in this study. 7

6 Supported by C-Tech Innovation advantage through technology FEC Services Ltd C-Tech Innovation Ltd, Capenhurst Technology Park, Chester, CH1 6ES Tel: Fax: Website: Registered in England number C-Tech Innovation Ltd, 2002

7 01 Introduction When waste is useful The agricultural industry produces many different kinds of waste. Some of this waste can be used to produce energy for the farm and enough surplus electricity to export to the National Grid. Other waste can be recycled. Cost-effective methods exist that enable waste to be put to good use with the added benefit of improving our environment, locally, nationally and as part of the EU. In other words, waste can be useful. It is widely recognised that UK waste management methods need to change to ensure that the environment is better protected both now and for future generations. In its Waste Strategy 2000, the UK Government states that one of its key objectives is to maximise the value recovered from waste through increased recycling, composting and energy recovery, and by developing new and stronger markets for recycled materials. 1 UK agriculture is a major producer of waste. Recent figures show that, overall, about 40% of industrial and commercial waste is recovered (35% being recycled) (Figure 1). 2 Figures 2 7, however, show that most agricultural waste materials are not recycled. Later sections of this report discuss the present commercial realities of waste recycling in the UK in more detail. Compared with many other sectors, little study has been made of agricultural wastes. This report addresses this lack of information. The aim is to assess all waste arisings in the UK agricultural sector and to critically evaluate energy-efficient processing techniques and existing/emerging recycling and energy-from-waste technologies, which facilitate more beneficial use of waste at source. Key objectives are to identify and quantify the major wastes arising by region and sector, to identify and quantify the major energy-using practices, and to analyse energy efficiency. A simple mass balance is presented for each agricultural sector, showing the inputs and outputs for each. Data for agricultural wastes Silage plastic (25,500t/yr) Veterinary waste (775t/yr) Scrap metal (23,000t/yr) Recycling Figure 1: Disposal of industrial and commercial waste. Energy recovery Other recovery Landfill Other disposal Landfill Burned Recycled Dustbin Reused Stockpiled Buried Returned to vet Figure 2: Disposal of silage plastic waste. Landfill Burned Recycled Dustbin Reused Stockpiled Buried Returned to vet Figure 3: Disposal of veterinary waste. Landfill Recycled Reused Stockpiled Figure 4: Disposal of scrap metal waste. are presented in more detail, listing each of the wastes produced by sector. Organic waste, which is the main waste produced by agriculture, is also presented by region and by season. As part of the Biffaward Programme on Sustainable Resource Use, this report identifies how recycling and waste-to-energy techniques can be used to benefit farmers and local communities, and shows opportunities for recycling at centralised energy-from-waste plants. Other relevant reports in this programme include Towards Sustainable Agricultural Waste Management 3 and Carbon UK. 82 Oil (27,000t/yr) Figure 5: Disposal of waste oil. Tyres (47,000t/yr) Figure 6: Disposal of waste tyres. Plastic packaging (33,000t/yr) Landfill Burned Recycled Stockpiled Reused Landfill Burned Recycled Dustbin Reused Stockpiled Buried Landfill Burned Recycled Dustbin Reused Stockpiled Buried Figure 7: Disposal of plastic packaging waste. 8

8 1.1 Key issues Table 1: Net value added by agriculture by region at factor cost. At the moment there are more than 200,000 registered UK farm holdings working in seven defined business sectors: dairy cattle pigs poultry layers meat birds arable and horticulture sheep beef cattle. In 1998, the net value added by agriculture in the UK was 5208 million (see Table 1), representing 1% of the total UK value-added figure. The percentage contribution to net value added in each of the UK regions is shown in Figure 8. England North East North West and Merseyside Yorkshire and Humberside East Midlands West Midlands Eastern South East and London South West Wales Scotland Northern Ireland Total UK 1998, million , million , million Over 2.0% % % % Under 0.5% Sector Table 2: Agricultural income by sector million 1999 million Milk Pigs Poultry Eggs Arable Total , ,231 Figure 8: Percentage contribution by region of agriculture to value-added figure. The total incomes produced by the main waste producing agricultural sectors in 1998 and 1999 are shown in Table 2. The general trends in farm income for the sectors are shown in Figure 9. 9

9 300 Dairy Pigs and poultry Arable At current prices In real terms Index 89/90 91/92 = Index 150 Index 150 Index /92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 (prov.) Figure 9: Trends in net farm income in the United Kingdom /92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 (prov.) Year /92 92/93 93/94 94/95 95/96 96/97 97/98 98/99 99/00 (prov.) Agriculture is responsible for a number of environmental issues that increasingly need to be addressed, including organic and inorganic wastes, and chemicals. Much of the waste and by-products arising on farms consists of organic matter, such as manure, slurry, silage effluent and crop residues. The Department for Environment, Food and Rural Affairs (DEFRA formerly Ministry of Agriculture, Fisheries and Food [MAFF]) quotes figures from 1991 that estimate present waste arisings to be 80 million tonnes of waste produced by housed livestock. Figure 10 shows that waste from agriculture accounts for 20% of the total waste arisings in the UK. 2 Other issues, such as the disposal of plastics and chemicals (especially sheep dip), are also high on the environmental agenda. The levels of plastic packaging waste generated on farms (estimated at ~33,000 t/yr) are small in comparison with the 11.7 million tonnes of packaging produced throughout the whole country. Sheep dip is a hazardous substance and has to be disposed of in appropriate and approved ways. Many of the wastes arising in agriculture are bulky and difficult to handle, for example plastic farm films and containers, which means that special vehicles and equipment are needed for recycling. 3 Agriculture Minerals Figure 10: Total UK waste arisings. Municipal waste Commercial Industrial Construction Other Foot and mouth disease No account has been taken of the large number of animals culled during the 2001 foot and mouth disease epidemic and the influence that this has had on waste production. Once restocking is complete, it is assumed that waste production figures will return to normal levels. 10

10 1.2 EU and UK Government policies Any future strategy for agricultural waste management cannot ignore the significant changes taking place in the agricultural sector, many driven by developments in European Union (EU) and UK agricultural and rural policy. The UK Government s seven-year plan to implement EU EC Rural Development Regulations (1999) has three priorities: the creation of a productive and sustainable rural economy the protection and enhancement of the rural environment the maintenance of thriving rural communities. 4 Sustainable waste management for agriculture is subject to a number of potential difficulties. This is due to its geographically dispersed nature, its seasonality, and to the fact that, to date, agriculture has been excluded from controlled-waste legislation. The Environment Agency is already helping to support farmers in some parts of the country in drawing up Whole farm plans ; bringing waste management, pollution prevention and biodiversity to the centre of their business planning. UK policy favours anaerobic digestion (AD) on environmental and energy grounds. The Department for Trade and Industry (DTI) paper, New and Renewable Energy, Prospects for the 21st Century, reviews the possible ways forward for implementing the government s targets on renewables. 5 To assist the deployment of AD, legislation providing greater controls for the spreading of wastes on land and emissions is required, together with a comprehensive support programme. In the UK, however, this does not seem to be a high priority for the regulatory body. The Environment Agency s Agriculture and the Environment document includes the view that capital grants should be available to farmers to assist with the financing of improvements to protect the environment and that strategy should be targeted according to environmental risk so that it is cost effective and the demands on farmers are proportionate to the potential environmental harm Soil strategy Organic farm wastes can provide valuable nutrients that allow farmers to reduce the amount of inorganic fertiliser applied and can lead to improvements in soil structure. The government proposes consultation on a draft soil strategy for England in the near future. In Wales, the National Assembly is considering how a similar plan should be developed. This is a response to the leading recommendation in the Nineteenth Report of the Royal Commission on Environmental Pollution, Sustainable Uses of Soil that describes soil as a resource that is often taken for granted. 80 The strategy will bring together the many individual policies and activities that contribute to soil protection and improvement. It will be one of the follow-up documents to the Sustainable Development Strategy, with the overall aim of promoting the sustainable use of soil Waste control Although agricultural waste is not classified currently as a controlled waste, increasing costs for disposal and tightening environmental legislation, such as Integrated Pollution Prevention and Control (IPPC) that will apply to pig farming, will necessitate improved waste control. 21 Under IPPC regulations there is a requirement to use the best-available techniques for pollution prevention and control, as well as for energy efficiency. There is evidence to show that many current practices used in agriculture are out of step with similar industrial requirements and therefore techniques will have to be developed and implemented to tackle these problems. 1.3 Energy use Agriculture is also a significant user of energy. The total energy use for agriculture is of the order of 10 TWh/yr, and covers a wide range of applications from motive power to environmental and process load. In contrast, by using appropriate recycling technologies, many waste streams can yield significant quantities of energy. It has been calculated that if all of the livestock wastes produced in the UK were to be treated using AD techniques, the quantity of energy produced would easily exceed the annual consumption of the entire agricultural industry. Energy, TWh/yr Total Livestock Crops Available Required Figure 11: Energy requirement and theoretical energy availability for the agricultural sector. This report identifies the most suitable wasteto-energy techniques and how the energy outputs may be integrated into existing businesses to benefit both the environment and individual business performance. 11

11 1.4 Report objectives Farmers, local councils and government officers need to be more aware of the issues involved in recycling and energy from waste, particularly as they are often related to pollution. Proper reuse of agricultural waste will show substantial benefit in reducing pollution, the amount of landfill and the overall use of fossil fuels, and could provide new jobs in rural areas. The government has shown its commitment to renewable energy, including energy from waste, in its paper New and Renewable Energy Prospects for the 21st Century. 5 For a significant level of energy recovery from agricultural waste to be achieved, particularly on-farm energy, some grant aid from the government may be needed. Often, organic waste streams are not regarded as valuable products because in their raw form they are not ready for reuse or sale, and are inconvenient and difficult to store and preserve. Therefore, without the proper means to refine and utilise the nutrients, many useful materials are disposed of as waste. County councils have recognised that renewable energy can begin to displace fossil fuels and help reduce risks to the environment from acid rain and climate change, and they wish to encourage the development of renewable energy sources in their regions. This report sets out some options for county councils, including a methodology for establishing a regional strategy for AD. 6 This report follows Towards Sustainable Agricultural Waste Management by Marcus Hodges Environment Ltd for Biffaward, which provides excellent data for management of non-natural and natural agricultural waste. 3 As well as readdressing some aspects of non-natural wastes, more detailed data on natural agricultural waste are included. Estimates of organic materials relate to the total quantities arising on farms, and do not distinguish between what can and what cannot be put to beneficial use what is by-product and what is waste. Whereas the Marcus Hodges report focuses on waste disposal strategy, this report attempts to show which wastes can be reused or recycled or generate useful energy. 1.5 Benefits of recycling and energy from waste Recycling and energy recovery will benefit the country in many ways, including reduced use of fossil fuels, reduction of methane emissions, reduced landfill disposal and reduced pollution Pollution reduction Nitrates and phosphates Animal manures and urine are responsible for about 80% of the UK s ammonia emissions, which contribute to acidification and eutrophication. 8,9 Leaching from farm manure and inorganic fertilisers is the main source of nitrate addition to water. In nitrate-vulnerable zones (NVZ), action plans to control nitrate losses from farms will need defining and implementing (see Section 6). Similarly, phosphates also leach from soil containing manure and fertilisers. In the UK, about 40% of the total phosphorus input to agricultural land is from livestock manures. Estimates suggest that there is a surplus of phosphorus of ~16 kg/ha/yr in the UK; organic farming methods produce less surplus. 10 There is evidence that when soil phosphorus exceeds that necessary for crop growth, mobilisation takes place in the soil solution and leaching begins, threatening water quality. 11 Thus, farm nutrient plans are required to minimise the pollution risks from both phosphates and nitrates. The most economical and environmentally safe way of managing manures and slurry is to obtain value from them through proper application to land (see Section 5). Properly controlled land spreading of livestock manure provides beneficial nutrients and organic matter to soils, but poor management and excessive application contribute to contamination of rivers. 6 DEFRA has identified the need for better management of animal housing, slurry storage and land spreading to reduce ammonia emissions Greenhouse gases Animal digestive processes and manures release about 40% of the UK s emissions of methane. 12 Methane from livestock digestion and manures, and nitrous oxide from fertilised land account for about 10% of UK greenhouse gas emissions Dark smoke There are approximately 3000 small, on-farm incinerators that are used for disposal of animal remains and other wastes. 6 Currently, the burning of plastics and other waste materials on-farm is permissible, but farm plastics are likely to become a controlled waste in the near future. However, the environmental standards relating to most agricultural activities are voluntary and are covered by codes of good practice. 14 If used incorrectly, incineration can lead to the generation of dark smoke. This is illegal under the Clean Air Act

12 Other hazards Pollution by heavy metals, organic chemicals and pathogens from manure and sewage sludge is also of concern. The risks must be controlled by considering the quality of the waste and by use of good practice in application techniques. 1.6 Legislation According to the Waste Management Licensing Regulations 1998, the land spreading of certain wastes is exempted, as a waste-recovery operation, from waste management licensing controls if it complies with certain rules. 18 The exemption applies if land spreading of waste will benefit agriculture or ecological improvement no more than a specified amount of the particular waste is applied to each hectare of land the Environmental Agency is informed in advance of the proposed land spreading. The main environment regulations applicable to agriculture include general pollution offences and abstraction licensing under the Water Resources Act ; the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations that were introduced to address serious polluting discharges arising from the livestock sector; and other environmental legislation introduced to implement EC directives, including NVZ and groundwater regulations. 20 The legislation affecting agriculture in the UK is described in greater depth in Section 6. DEFRA and the Welsh Office have both issued codes of good practice for the protection of air, soil and water. 14,15,16 DEFRA has also undertaken a number of initiatives that include demonstration farms, and the provision of free advice on farm-waste management plans that covers the storage of slurry, the management of manures, and the disposal of wastes and plastics. Under the IPPC directive, the Environment Agency estimates it will regulate 1400 poultry and 430 pig holdings by (Outdoor pigs, and the dairy and beef sectors are not included in the scope of the directive, although they have similar potential to cause pollution.) Nitrate-vulnerable zones The EC document Nitrate from Agricultural Sources was devised to reduce or prevent the pollution of water caused by the application and storage of inorganic fertiliser and manure on farmland. 23 Formal compliance with this directive by the UK falls under a staggered timetable, at present a limited number of NVZs are designated. This differs from the approach of other EU countries, for example Denmark and the Netherlands, who have chosen to implement the provisions of the directive across their entire territory. However, the European Court of Justice ruled in 2001 that the UK had failed to implement the Directive (Case C 1999/069) properly and that the same measures must be implemented across the whole or most of the UK by the end of

13 1.7 The European approach Various European countries have different approaches to agricultural waste recycling due to geographical influences and different agricultural practices. Some of the issues involved can be seen in relation to the use of AD across Europe Denmark Denmark is seen as the market leader in centralised anaerobic digestion (CAD) of agricultural wastes. Agriculture and energy policies have been proactive in the development of AD, and Danish developers and farmers cooperatives have constructed approximately 20 CAD plants and 20 farmscale digesters. The major driving forces behind Danish implementation are production of electricity and heat reduction of organic waste spread to land. Strict regulations and substantial funding assistance have aided this implementation. Farmers in Denmark are forced by law to provide nine-months storage capacity for manure. However, during the early stages of the implementation of legislation, up to 40% grant assistance was made available to improve slurry storage facilities. This could be used towards the development of AD facilities. There are also extensive district heating networks in place throughout the country, enabling fairly easy access to heat markets. Other driving forces include Denmark s lack of natural resources and widespread intensive farming The Netherlands In the Netherlands, a few pilot/demonstration plants were constructed and then operated for a number of years, but these have all closed down due to poor economics. 22 The main parameters affecting the feasibility of biogas plants in the Netherlands are legislation covering the introduction of minerals into the soil is strict and the value of digested manure is low legislation prescribes a high quality level for compost and implies import restrictions on bringing digested manure to the market the main focus for manure policy is ammonia reduction co-digestion of manure with other organic wastes is not allowed the values of biogas and heat are low Germany Germany has more than 400 farm-scale AD plants and a few large CAD plants. The larger plants tend to be in the former East Germany, with its large intensive farms The rest of Europe Throughout the rest of Europe there has been limited implementation of large-scale AD facilities, although there is interest in many countries in the development of such projects. This is reflected in their energy, environmental and waste management policies. 14

14 02 The inputs Keeping the balance For every desired agricultural output milk, meat, eggs or vegetables there has to be an input feed, energy, packaging, water, fuel, etc. These inputs themselves create additional waste. Some of this waste is readily degradable and some is not for example, plastic, chemicals, engine oil and needs specialist methods for recycling or safe disposal. The ideal outcome would be to ensure that all these different kinds of waste become useful commodities. To perform a mass balance on UK agricultural practices, the inputs, outputs and recycling options need to be correlated in relation to products. Table 3a: Inputs for 1000 l of milk. Material Input per 1000 l Input per l Comments Feed Water Drugs Rainwater Plastics Fertiliser Fuel (diesel) Energy 300kg 3000kg 615mg 1.3kg 100kg 10kg 60kWh 0.3kg 3kg 0.6mg 800m 3 0.8m 3 1.3µg 0.1kg 10g 220kJ Table 3b: Total UK inputs for dairy cow production. Does not include follower/heifer feed For drinking, cleaning Grassland water requirement Containers, feed/fertiliser bags, silage wrap, baler twine For production of grass Mainly for field work For milk cooling, water heating, lighting, pumping Details of the waste products generated by the various categories of agriculture are covered in Section 3, and recycling options are discussed in Sections 5 and 7. For completeness, inputs in relation to product output also need to be considered. Tables 3 9 set out inputs for a range of common products based on typical unit output, and inputs for the whole UK industry. They are intended to be broadly informative without being exhaustive in their analysis. Material England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West Wales Feed kt Water kt 34, , Rainwater Mt 13, Fertiliser kt Plastics t 15, Diesel t 116,142 25, , ,272 19,503 Drugs kg 23, Energy GWh Scotland , Northern Ireland , Total UK ,509 21, , ,398 35, The labour requirement for 1000 l of milk is 3 h, equivalent to 10 s per litre of milk. Also required is grass consumed in the field at 0.1 ha of grassland per 1000 l or 1 m 2 per litre. 15

15 Table 4a: Inputs for 72kg 'pork' pig. Material Input per pig Input per kg Comments Feed 205kg 2.8kg Includes feed for parent stock Water 480kg 6.6kg For drinking, cleaning Drugs 3.2g 0.65g Antimicrobial drugs Plastics 50g 0.7 g Containers, bags Glass Paper products 30g 0.5g 22g 0.3g Lights, pig lamps, medicine bottles Containers, bags, sanitary wear Energy 35kWh 0.5kWh Ventilation, lighting, heating, feeding, waste handling The labour requirement per pig is 0.5 h, equivalent to 0.5 min per kg of pork. Table 4b: Total UK inputs for pork production. Material Feed kt Water kt Paper t Plastic t Glass t Drugs kg Energy GWh England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West , Wales Scotland Northern Ireland Total UK ,

16 Table 5a: Inputs for 2.3kg of meat bird (broiler). Material Input per bird Input per kg Comments Feed 4.7kg 2kg Water 5kg 2kg For drinking, cleaning Bedding 2kg 1kg Wood shavings, paper waste, processed straw, etc. Paper products 8g 3g Feed trays for young birds Plastics 250mg 108mg Containers, bags Energy 1.5kWh 0.65kWh Ventilation, lighting, heating The labour requirement per chicken is 1.5 min, equivalent to 0.5 min per kg of chicken. Table 5b: Total UK inputs for meat bird (broiler) production. Material Feed kt Water kt Paper t Plastic t Bedding kt Drugs kg Energy GWh England North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West Wales Scotland Northern Ireland Total UK ,

17 Feed Water Drugs Table 6a: Inputs for 12 eggs. Material Input per 12 eggs Input per kg Comments Paper products Plastics Energy 1.8kg 4kg 1mg 30g 250mg 0.2kWh 3kg 6.6kg 1.6mg 50g 108mg 0.3kWh For drinking, cleaning Egg trays, egg boxes Containers, bags Ventilation, lighting, materials handling The labour requirement per dozen eggs is 1.3 min, equivalent to 2 min per kg of eggs. 2.1 The cyclical nature of agricultural production Agricultural production invariably requires a degree of self renewal in the form of breeding stock or seed. This is common to both animal and vegetable production businesses; the production of pigs, cattle and poultry requires parent stock and the production of grain and vegetables needs seed. Sometimes the parent stock/seed is kept within the farm and is an intrinsic part of the production system. In other cases, parent (and grandparent) stock is a totally outsourced element and, as such, becomes an external input. Table 6b: Total UK inputs for egg (layer) production. Material England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West Wales Scotland Northern Ireland Total UK Feed kt Water kt Paper t 22, ,692 Plastic t Drugs kg Energy GWh Therefore, it is important when defining the nature of an enterprise to also define the source of the parent stock/seed. Where parent stock/seed is produced on farm, then the inputs and outputs associated with them have to be apportioned to the production output of the system. Another issue is the recycling of wastes between different types of agricultural enterprise. An example is mixed farming enterprises where the output and waste of the arable component of production is linked to the output and waste of the livestock component. For example, grain can be milled to produce animal feed and then used onfarm. Similarly, waste straw can be used for animal bedding, and then the soiled bedding can be reused to fertilise land and hence produce the cereal crop. Transport in and out In the supply chain, the transport of materials in and of products out needs to be considered. These transport components have not been included for the purposes of this report and analysis. 18

18 Table 7a: Inputs for 1t of grain. Material Input per t Input per kg Comments Seed 30kg 30g Usually bought in Fertiliser 80kg 80g Rainwater Plastics 928m 3 1m 3 290g 0.3g Grassland water requirement Containers, feed/fertiliser bags, silage wrap, baler twine Oil 95g 95mg For machinery Chemical spray 400g 0.4g Pesticide, herbicide (average 6.5 applications/year) Fuel (diesel) 9kg 9g Mainly for field work Energy 60kWh 220kJ For drying The labour requirement per tonne of grain is 1.4 h, equivalent to 5 s per kg of grain. The land required is 0.14 ha per tonne of grain, 1.4 m 2 per kg. Table 7b: Total UK inputs for cereal production. Material Seed kt Rainwater Mt Fertiliser kt Plastics t Chemical spray, t Diesel t Waste oil t Energy GWh England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West 114, ,676 16,710 18,919 28,281 12,352 17, ,750 18, ,136 44,560 50,451 75,416 32,939 46, , Wales 11, , Scotland , Northern Ireland 13, , Total UK 150, , ,

19 Table 8a: Inputs for 38.5kg lamb. Material Input per lamb Input per kg Comments Feed compound 44kg 1.4kg Includes feed for ewes Water 0.46m 3 11l Including water for ewes Rainwater 685m m 3 Based on stocking of 16 lambs per hectare Medicine 16mg 0.42mg Fertiliser 115kg 2.99kg Fuel (diesel) 13kg 338g Electricity 10kWh 261Wh Some lighting and heating at lambing times Plastics 336g 9g Mainly bags Paper products 179g 4g Mainly bags Sheep dip 5l 126ml Diluted The labour requirement per lamb is 5 h, equivalent to 8 min per kg live weight. Table 8b: Total UK inputs for lamb production. Material Feed kt Water kt Rainwater Mt Fertiliser kt Plastics t Diesel t Drugs kg Energy GWh England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West ,333 29,428 17,866 19,337 12,148 22, ,188 33, Wales , Scotland , Northern Ireland , Total UK ,156 18, ,

20 Table 9a: Inputs for 520kg beef animal. Material Input per cow Input per kg Comments Feed compound 1200kg 2.22kg Wide range depending on intensification Water 6.2m 3 11l Drinking water Rainwater 4614m m 3 Based on stocking of 3.25 animals per hectatre Slaughter age up to 1.5 years Medicine 3.0g 5.8mg Fertiliser 848kg 1.63kg Fuel (diesel) 72kg 138g Plastics 14kg 28g Silage wrap, bale netting, fertiliser bags Electricity 27kWh 51Wh Paper products 2.13g 4.1g Mainly bags The labour requirement per animal is 12 h equivalent to 1.5 min per kg live weight. Table 9b: Total UK inputs for beef production. Material Feed kt Water kt Rainwater Fertiliser Mt kt Plastics t Diesel t Drugs kg Energy GWh England (total) North West North East Yorkshire and Humberside East Midlands West Midlands Eastern South East South West Wales , , , 10, Scotland ,981 47, Northern Ireland , Total UK ,112 10, , ,

21 03 Major waste arisings What rubbish? The amount of organic farm waste produced each year is considerable. But other kinds of waste have an environmental impact, too. Such minor waste arisings paper and board, plastics, chemicals, batteries, waste oil, tyres, scrap metal and miscellaneous packaging vary from farm to farm, and this has significance for recycling services and facilities and where they operate. Agriculture produces a wide range of organic (animal and vegetables residues) and inorganic (packing, plastics and chemicals) waste materials. The organic waste load from agriculture is particularly significant. Animal excrement wastes, for example, account for a greater total biological load on the environment than the total sewage waste derived from the human population. It is notable that traditional methods of disposal of organic wastes to land have served the agricultural industry well over the years. These have led to an inherent degree of natural recycling, with organic wastes being returned to soil and hence to plant growth. However, land disposal has not been without its problems. With the intensive nature of UK agricultural production, waste streams have outstripped the capacity of the land to make good use of them in many areas, and disposal is now monitored and controlled to avoid watercourse pollution from nitrates and oxygen-consuming bacteria. Targets set by the Environment Agency for the nitrate loading on land mean that many farmers have to consider alternative methods of disposal or recycling. For the purposes of this study, agricultural wastes are categorised as organic waste plastics paper/cardboard chemical and veterinary waste machines other. 3.1 Deriving waste figures The nature and output of agriculture in the UK are well documented, largely because of the need to track production in connection with EU financial support systems. Therefore the associated waste output can be extrapolated fairly easily. Some data have already been produced for Biffaward in the Marcus Hodges report, and these have been used as a starting point to which data have been added for this work. 3 As with all studies of this nature, the figures presented are estimates and are limited by the accuracy of the original data. The sensitivity of agriculture to weather influences means that year-to-year variations in production are very significant. Where possible, the results of consultations and practical experience of farming methods have been applied to produce a realistic overview. The total waste production reported by Marcus Hodges for each agricultural sector has been apportioned on a regional basis, according to agricultural census figures for each enterprise category (as published by the statistical departments of DEFRA, Department of Agriculture and Rural Development (DARD) [formerly DANI Department for Agriculture Northern Ireland], the Scottish Executive and the National Assembly for Wales). The agricultural census data are from the 1999 production year. Typical farm waste profiles were prepared in a similar way. Economic enterprise sizes were defined and waste amounts from the Marcus Hodges figures were apportioned according to animal numbers/crop production. This report explores waste production further by considering regional densities and seasonality. Both these issues are of primary importance if the practicality of waste recycling is to be addressed adequately. In extending the availability of data, it has been necessary to obtain more detail from DEFRA/DARD production figures and to make detailed assessments of typical farming practices. There has been extensive consultation with suppliers, trade associations, advisory bodies and individual farmers in making these assessments. Beef cattle have not been considered as major potential contributors to the waste resource as they tend to be kept outside for a great part of the year, and are often bedded on straw, which is not ideal for AD as it requires chopping prior to use. Similarly, sheep have been excluded from this study. All poultry waste has been considered as a potential contributor Agricultural business categories Table 10 helps clarify the way in which agricultural businesses are categorised for sizing purposes. This report uses these sizing criteria when referring to the various key business areas. 22

22 Table 10: Agricultural business categories. Business type Sizing criteria Comments Dairy Pig Poultry layers Meat birds Arable Horticulture Sheep Beef Milking cows Breeding sow places Hen places Bird capacity Hectares Hectares of protected crop Ewe numbers Beef head The dairy business is driven by the number of cows in milk. Clearly there are other associated stock such as calves and heifers (young female stock also referred to as followers), there may be beef animals being raised on an enterprise (the bull calves of the milking cows). One milking cow will normally produce one calf per year Breeding sows produce piglets that are grown for about six months before slaughter. A sow produces about 22 piglets per year, so a 100-sow breeding and finishing unit will have a population at any one time of about 1100 pigs Hens are brought on to the site at about 18 weeks of age (point of lay) and normally lay for one year before removal All birds are brought on to a meat-bird site as chicks in one flock and remain there until slaughter. The period of occupancy depends on the species and weight requirement, but will vary from six or seven weeks (chickens) to 16 weeks (turkeys). So for a 100,000-place chicken site, the total bird throughput might be 700,000 birds Arable area is the main criteria used for sizing these enterprises. Cereal crops are the backbone of arable production, with some oil seeds and vegetable production. Wheat is the main crop with average output of 7t/ha This is the area of glass or polythene structure. Output varies massively with the type of crop, which can be anything from cucumbers to bedding plants Ewes produce from one to four lambs in the late winter or spring each year (average 1.45 surviving) Most beef cattle are a by-product of the dairy industry. Systems vary in intensification, with animals being slaughtered at between one and two years old. Dedicated beef enterprises are rare. They are mostly integrated with another enterprise type, typically dairy 3.2 Typical farm waste profiles Tables indicate the amounts of waste generated by typical UK farming enterprises. These figures are only a rough guide, as many farms have secondary enterprises running in conjunction with, and often supplementing, the main business. Seasonal effects are also very significant. It is important to consider wastes at enterprise level as this can quickly give an indication of the economic and physical practicability of recycling wastes. Total waste figures for the industry may look high when viewed at a macroscopic level, but it is only when the waste produced is viewed at enterprise level that the true picture is revealed. The figures show that the largest quantities are slurry and farmyard manure. However, farmers do not classify these materials as waste, but as a valuable recyclable commodity. Recycling is generally by return to the land to enhance fertility. Recycling efficiency is considerably lower than the ideal, mostly because of leaching and volatilisation of the useful nutrients. The problematic wastes encountered on farms include the inorganic consumable materials. Farmers in England and Wales produce about ~59,000 t of waste plastic a year. 24 These materials, such as plastic containers, silage film and liquid chemical waste, often have a low recycling value in their off-farm form or are difficult to dispose of on-farm, given the limited facilities available. Silage liquor is produced as a result of ensiling grass and is a concentrated, acidic, high biological oxygen demand (BOD) pollutant. It is usually disposed of by land spreading. Plastics represent the next most significant pollutant in terms of weight. 23

23 Type Table 11: Annual waste production of 80-cow dairy unit. Organic Slurry Farmyard manure Silage effluent Milk waste Animal carcasses Animal tissue Plastic Bags Packaging Fertiliser/seed bags Silage wrap Paper and board Bags Paper/card Machinery Batteries* Waste oil* Tyres* Other Glass* Rubber* Baler twine/net wrap Scrap metal* Miscellaneous packaging* Apportionment of minor wastes Output, t It has been necessary to apportion some of the minor wastes on a farm-by-farm basis. This does not take into account farm enterprise category, but classifies farms according to typical business size. This is not unreasonable as many of the waste streams (scrap metal, miscellaneous packaging, etc.) could be regarded as a general waste output. This is not likely to vary from enterprise type to enterprise type. These are marked with an asterisk on the tables Dairy Organic animal wastes represent the bulk of material to be dealt with by a typical dairy unit. Generally, slurry is stored for spreading on land in the drier months of the year. Treatment is not usually undertaken, although some farms use mechanical separation to aid handling of the waste. Farmyard manure (FYM) based systems are increasing in popularity because of the welfare drawbacks of all-slurry based housing. Although bulkier to handle, FYM is a less environmentally hazardous material. It is often stored on bare field land and left to digest slowly. Complete composting of FYM is problematic, as it is not easily aerated and settles into a anaerobic state quite quickly Pigs The issues affecting dairy farming are also apparent in pig farming. Slurry and FYM are the main wastes. Pig production differs because it is invariably more intensive than the dairy industry in terms of the housing density of the stock. Pig farming therefore needs much less land for production purposes. Waste disposal to land often relies on neighbouring arable enterprises to take the waste Poultry A typical broiler farm produces seven batches of birds per year. Bird excrement mixed with bedding material (litter) is the largest waste output. This waste is high in energy and relatively dry. It is generally returned to the land as a nutrient. However, some producers send their litter for incineration in specially built power stations Sheep There is a wide difference between upland and lowland sheep production. Breeds are selected for appropriate hardiness, with the upland breeds being virtually selfmaintaining. Most organic waste is therefore returned directly to the ground, and other waste is minimal Beef cattle Waste output depends upon the level of intensification. Extensive systems are based on minimal winter housing and, during most of the year, organic waste goes directly to ground. More intensive systems are based on slightly longer housing periods and leading to larger amounts for disposable organic waste. Straw bedding is widely used. Type Table 12: Annual waste production of a 400-sow unit. Organic Slurry Farmyard manure Animal carcasses/tissue Plastic Bags Packaging Paper and board Bags Paper/card Machinery Batteries* Waste oil* Tyres* Other Glass Rubber Scrap metal* Miscellaneous packaging* Output, t *Minor farm wastes 24

24 Table 13: Annual waste production of a 250,000-broiler unit. Type Output, t Organic Poultry litter Bird carcasses/tissue Plastic Bags* Packaging Paper and board Bags Paper/card Other Glass Miscellaneous packaging* Type Table 14: Annual waste production of a 20,000-layer unit. Organic Layer slurry Bird carcasses/tissue Plastic Packaging Paper and board Paper/card Other Glass Miscellaneous packaging* Output, t Arable Arable farms produce straw as a by-product of cereal production. Some straw is recycled as animal bedding but it is mostly regarded as a low-value waste. Banning straw burning has caused farmers to find other routes of disposal, the most common method is incorporation into the land ploughing in. Incorporation is regarded as of neutral benefit as straw has little nutrient value for growing crops Wastes arising from horticulture The variety of production systems and outputs from horticulture make it impossible to derive a meaningful typical waste output profile. However, the two major wastes are green-crop residues and used rock wool growing medium Rock wool Each year, UK horticulture uses approximately 35,000 m 3 of rock wool. This is used mainly for producing salad crops. When the crops are spent, the rock wool growing medium and plant waste are taken to landfill sites. Almost all used rock wool is removed from glasshouses in November, thus producing one large batch of waste per year Green-crop residue waste Green-crop residue waste comprises trimmings and spent plant material. This material is easily composted or returned to fields to rot and recycle. Field spreading is the normal route for disposal. Glasshouse sites suffer a similar problem to that often encountered by pig units little space for bulk wastes. Field spreading is the normal route for disposal. Type Table 15: Annual waste production of a 300-ewe sheep flock. Organic FYM Animal carcasses Animal tissue Plastic Bags Packaging Fertiliser/seed bags Paper and board Bags Paper/card Machinery Batteries Waste oil Tyres Other Sheep dip Glass* Rubber* Baler twine, net wrap Scrap metal* Miscellaneous packaging* Output, t

25 Table 16: Annual waste production from 80 head of beef cattle. Table 17: Annual waste production of a 150-ha arable unit. Type Output, t Type Output, t Organic FYM Silage effluent Animal carcasses Animal tissue Plastic Bags Packaging Fertiliser/seed bags Silage wrap Paper and board Bags Paper/card Machinery Batteries Waste oil Tyres Other Glass* Rubber* Baler twine, net wrap Scrap metal* Miscellaneous packaging* Organic Baled straw (removed) Vegetable/cereal residues Ploughed-in/cultivated straw Plastic Plastic agrochem packaging Plastic fertiliser/seed bags Paper and board Paper agrochem packaging Paper seed bags Chemicals Pesticide washings Machinery Batteries* Waste oil* Tyres* Other Scrap metal* Miscellaneous packaging* Table 18: Location of rock-wool waste in UK Location Percentage of total Jersey 10 (all goes to landfill) Isle of Wight Sussex Kent Lee Valley Humberside 35 Lancashire 20 26

26 3.3 Geographical distribution of agricultural business and its relevance to waste Production density affects waste density. Therefore, it is important to understand the geographical distribution of waste when considering recycling opportunities. Production density data for dairy, beef, sheep, pig, poultry and arable businesses are shown in Figures Regions with a high density of a particular activity are most likely to have localised waste hot spots. Identifying these can be useful in planning the location of waste handling facilities/services. High production densities in horticulture and field vegetables, however, are local rather than regional, so, a generalised regional analysis would not be useful for this UK macroscopic overview. 30,000 80,000 11,000 30, , Under 4000 Figure 13: Pig population (sows and gilts). 600,000 2,200, , , ,00 200,000 50, ,000 Under 50,000 Figure 15: Sheep population. 100, ,000 60, ,000 30,000 60,000 11,000 30,000 Under 11, ,000 1,000,000ha 300, ,000ha 200, ,000ha 100, ,000ha Under 100,000ha 75, ,000 35,000 75,000 20,000 35,000 15,000 20,000 Under 15,000 Figure 12: Dairy cow population. Figure 14: Arable and horticulture densities. Figure 16: Beef cattle population. 27

27 A glasshouse-based horticulture business is driven by local infrastructure availability rather than geo-climatic suitability. Because of such random development, regional analysis is unsuitable and a more localised view needs to be taken. The national production maps show that the ruminant animal population tends to dominate the western areas of the UK. Similarly, arable businesses are more plentiful in the east. This is a simple geo-climatic issue where the land and wetter climate of the west suits grass production, and the flatter, fertile and drier easterly areas favour the production of cereals. Pig and poultry production tend to be based in the east because of the local availability of cereal as a staple food. However, there are pockets of dense production in other areas Waste production densities Tables show that the highest volume waste materials are slurry, FYM and straw. Slurry and FYM have potential for processing in anaerobic digesters, and straw in powerproducing incinerators. The technical feasibility of utilising these wastes is covered in Section 5. It is only necessary to define the geographical areas where these wastes might be of such a concentration as to justify the investment in centralised utilisation facilities. Using the data on total waste production and regional concentrations of agricultural production from DEFRA, it has been possible to derive waste concentration maps for the UK. Figures show the amount of digestible waste from the livestock sector and of combustible straw in terms of energy potential. Over 10,000,0000t/yr 5,000,000 10,000,000t/yr 2,500,000 5,000,000t/yr 1,000,000 2,500,000t/yr Under 1,000,000t/yr Over 2,000,000t/yr 1,000,000 2,000,000t/yr 800, ,000t/yr 350, ,000t/yr Under 350,000t/yr 150, ,000t/yr 100, ,000t/yr 35, ,000t/yr 10,000 35,000t/yr Under 10,000t/yr Figure 17: Dairy slurry production density. Figure 18: Pig slurry production density. Figure 19: Layer slurry production density. 28

28 Over 7000TJ/yr TJ/yr TJ/yr TJ/yr Less than 2000TJ/yr Figure 20: Potential energy from animal waste by anaerobic digestion. Individual counties producing most straw 1,500,000 2,500,000t/yr 1,000,000 1,500,000t/yr 400,000 1,000,000t/yr 100, ,000t/yr Under 100,000t/yr 3.4 Major waste sources and production seasonality The production seasonality of waste is as important as regional concentration (see Figures 22 29). and is a key issue affecting the load factor for waste facilities Animal waste (slurry and farmyard manure) The largest tonnage of any single agricultural waste is animal excreta. Where animals are out to field it this laid directly to land, but for housed animals it has to be collected and disposed of. Slurry and FYM are generated by housed dairy and beef cattle through the winter period (about days). Some slurry is land spread during the winter months when weather and ground conditions allow. FYM is removed from cattle buildings in the late spring, stockpiled for composting and land spread later in the year. Pig and poultry manure is produced on a year-round basis. Although the largest volume of waste is dairy slurry, the need for land for grass production means there is always a natural area where it can be spread and where nutrients can be recycled back to the soil. Pig and poultry waste can be more problematic because animals are housed more intensively, often without an area of associated land Vegetable residues Vegetable residues are produced on a yearround basis from field vegetable production, cereals, sugar beet and horticultural crops. They are mostly returned to land but some composting is now evident Waste milk Most waste milk results from using antibiotics during calving and for treating mastitis infections. Waste milk is usually spread to land. It has an extremely high BOD and great care has to be taken during spreading to avoid watercourse pollution Straw Straw is a by-product of harvesting cereals and oil seeds in late summer. Since the ban on field burning in 1990, much of it (usually wheat straw) is now chopped and incorporated into the soil during tillage operations after harvest. Some straw (mainly high-quality barley straw) is baled and used for forage and for bedding of stock. 10,000,000 8,000,000 Waste, t 6,000,000 4,000,000 2,000,000 0 Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Pigs Cattle Poultry Figure 21: Straw production density. Figure 22: UK animal waste (slurry and FYM). 29

29 The amount of straw baled at harvest depends on winter stock requirements, or the opportunity for selling on to livestock farmers. Some straw is baled on contract for powerstation fuel. Haulage logistics currently limit this trade Silage effluent Ensiling grass is the most popular way of grass preservation for the winter. However, it produces a run-off liquor called silage effluent which has a high BOD. The amount of silage effluent produced depends on the timing of the cut and the weather conditions. Cuts are made from spring through till late summer. Very early or very late cuts of silage will contain more water and will therefore produce more effluent. Silage effluent can either be fed back to cattle or land spread without treatment. Waste, t 4,500,000 4,000,000 3,500,000 3,000,000 2,500,000 2,000,000 1,500,000 1,000, ,000 0 Jan Feb Straw (baled) Mar Apr Silage effluent May Figure 23: UK organic by-products and waste. 40,000 35,000 Jun July Aug Straw (ploughed in) Sept Oct Nov Vegetable residues Dec UK animal carcasses and tissue On some farms, for example, pig or poultry, livestock mortality occurs regularly throughout the year. This means an ongoing system for carcass disposal is necessary. For other livestock, the mortality rate is more seasonal and usually occurs during lambing or calving. Waste, t 30,000 25,000 20,000 15,000 10, Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec The 2001 foot and mouth epidemic and the ongoing efforts to eradicate bovine spongiform encephalopathy (BSE) have made the disposal of carcasses a highly regulated and complex matter. Pigs Cattle Poultry Figure 24: UK animal carcasses and tissue. Sheep Plastic waste Silage film Horticultural film Silage sheet, shrinkwrap, baler bags, baler twine and net wrap are used from May to September. These materials become waste after the silage is used for feeding cattle during winter. Horticultural film is used to protect early crops of field-scale vegetables. Once the risk of frost is past, the film is removed in early June. 30

30 Waste, t Paper packaging Paper and cardboard packaging may be used with plastic packaging, for example, boxes for plastic agrochemical containers. This is often burned immediately after use or stockpiled until field operations are over and then disposed of Liquid chemical waste 500 Pesticide washings 0 Jan Feb Silage wrap Mar Apr May Baler twine/net wrap Figure 25: UK non-packaging plastic waste. Jun July Aug Horticultural film Sept Oct Nov Dec Pesticide washings occur in two main periods, according to the Crop Protection Association; 40% of washings occur in the spring, with 60% being produced in the autumn. Sheep dip Waste, t Sheep are traditionally dipped shortly after they have been clipped in late spring through early summer. Spent dip is then usually diluted and land spread under licence from the Environment Agency Waste oil 0 Jan Feb Mar Fertiliser and seed bags Apr Figure 26: UK plastic packaging waste Packaging waste May Agrochemicals Agrochemical containers Agrochemical packaging waste is produced in spring and autumn. The containers are often stockpiled until field operations are complete and then disposed of. Fertiliser and seed bags Fertiliser and seed bags become waste in spring and autumn during and after drilling and fertiliser top-dressing operations. June July Aug Sept Animal health packaging Oct Nov Feed bags Animal health and miscellaneous packaging Dec Small quantities of animal health and miscellaneous packaging waste are produced year round. Feed bags Plastic feed bags are also produced as waste all year round. Production peaks during the winter livestock-housing period. Waste oil is produced all year round and is normally stockpiled for recycling by outside contractors protecting the wearing parts on farm machinery burning to heat farm buildings (typically the farm workshop) Miscellaneous waste Scrap metal, batteries, worn tyres, etc. have no seasonal link. Scrap iron is frequently stockpiled and disposed of at a convenient slack work time. Glass and rubber veterinary waste is produced all year round with no particular seasonal pattern. 31

31 Figure 27: UK paper packaging waste Waste, t Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Seed bags Agrochemicals Animal health packaging Feed bags Figure 28: UK liquid/chemical wastes. 40,000 35,000 30,000 Waste, t 25,000 20,000 15,000 10, Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Pesticide washings Sheep dip Waste oil/lubricants Figure 29: UK miscellaneous waste (veterinary waste glass, 762 t/yr, and rubber, t/yr, not included). Waste, t Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Scrap metal Tyres Batteries 32

32 04 Focus on enterprise energy Use it or lose it The most effective and efficient way to recycle energy is to do it as close as possible to the waste source. To find a fit between energy supply and energy demand we must understand how farms use energy. Where waste is recycled for energy production it is also useful to identify the corresponding nearby energy sinks. Clearly, the nearest energy sink will be the farm that produces the waste. Although not the only possible energy sink, using energy produced from on-farm recycling will always be a potential favourite: The source of waste energy and the sink for use are physically close, therefore the cost and logistics of waste handling will be low. The value of energy from waste is at its highest, as it will be used to displace bought-in energy. This is in contrast with situations where energy is sold to the general wholesale market, where selling values are lower. Enterprise energy use is supported by the UK Government s waste strategy, which states that it is desirable for the final disposal of wastes to take place as close as possible to the place where the materials first become wastes Main energy usage The following sections and tables show the main uses for energy in the major agricultural sectors. Energy demand figures are given, and the characteristics of use are described with respect to energy supplied from recycling. Neither beef nor sheep production is included in this section, as energy use connected with these production systems is generally very low. Table 19: Dairy industry primary energy use. Type Water heating Milk cooling Vacuum pump Udder washing Lighting/heating Description Water heating is carried out in wellinsulated, closed or lidded tanks. Thermostatically controlled electric elements are used to heat the water Milk is cooled in either an ice bank tank or by a direct-expansion tank Vacuum pumps are used to draw the milk through the pipe system Udder washing water at 40 C is required at a rate of 0.5l/cow and is normally delivered by a spray hose Good light levels are required in the milking parlour to aid stock tasks. Personnel and frost protection heating are also required Dairy industry On-site energy use in the dairy industry is dominated by the requirements for milking cows and cooling milk. Patterns of energy use vary little throughout the year, with most dairy farmers milking twice a day and cooling the milk with directly refrigerated or ice-jacketed tanks. Other main loads are water heating for cleaning purposes and lighting the stock shed and parlour Pig and poultry production It is notable that the energy demand in both intensive pig and poultry production is all year round and has a high load factor. In the pig industry, it is fairly constant and in the form of both heat and motive power. Likewise, in meat-bird production, heat and motive power Typical energy consumption per cow/year, MJ Load characteristics Water heating accounts for a third of daily energy, but this rises to half if acidified boiling water is used to clean the pipe work system and where water is needed for calf feeding. The water heater is normally on a time clock to use off-peak electricity Ice-bank tanks are cooled with near-freezing water from ice reserves built up using as much off-peak electricity as possible. Direct expansion uses a refrigeration system that cools milk on demand Pumps run to demand during milking operations Water demand is met by increasing the size of the main water heater or a specific heater dedicated to udder washing Waterproof fluorescent strip lighting is common. Parlour heating is often provided by quartz, linear heaters are required, but the pattern of usage is on a 7 to 12 week cycle with intensive use of heat in the first three weeks and increasing use of ventilation in the remainder. Heating is not widely used in egg production, although the motive and lighting energy demands are constant. Furthermore, replacement egg-laying birds are reared on separate sites. Therefore, the digestion of layer waste has no immediate attraction for reuse on a production site. 33

33 Table 20: Pig production primary energy use. Type Description Typical energy consumption per pig, MJ Load characteristics Ventilation Fans to cool buildings and to provide fresh air for the stock. Fans are controlled either by variable voltage to control the speed, or are switched in banks 25 Ventilation is required 24h/day, with maximum demand during periods of highest temperature, i.e. summer and mid-afternoon Creep heating Piglets require a local temperature of between 21 and 32ºC. Heating is commonly from bright emitter lamps (pig lamps), although underfloor heating is sometimes used. Control is either manual or thermostatic 36 Required for all piglets up to three weeks of age, 24h/day. Maximum demand occurs at coldest periods and when piglets are very young Weaner heating Pigs from five to seven weeks old are housed in rooms or kennels. Rooms are fan ventilated and have duct or radiant heating. Kennels are naturally ventilated and have underfloor or radiant heating 29 Heating demand is greatest when pigs are very young and in the wintertime. By five weeks of age, heating load is very low as the pigs generate enough heat Lighting Lighting is required for all buildings for stock inspection and for the pigs 15 As buildings are usually windowless, lighting is required 24h/day. Lights are often dimmed Feeding systems Feed is either supplied in dry meal form or mixed with water. Automatic conveying and mixing are common 6 Feeding is either ad-lib (available at any time), or carried out twice daily. There is some potential for load shifting Manure handling and removal A large proportion of the manure produced is in liquid form (slurry) and can be pumped. In some cases, slurry will pass over a mechanical separator that removes the larger solid particles, making it easier to handle. The slurry can be treated by aeration to reduce its smell and pollution potential 8 The large pump motors often require three-phase supplies. Although largely dictated by the ability of the system to cope with transient waste production, pumping, aeration and separation can most often be timed to occur in low-cost periods Feed preparation A small number of pig farms prepare their own feed from grain and bought-in ingredients. Preparation involves crushing the ingredients (mainly grain), weighing and mixing 6 Feed preparation or milling and mixing may be done on a daily or weekly basis. Some degree of automation allows manipulation of the load 34

34 Table 21: Meat-bird production primary energy use. Type Description Typical energy consumption per bird, MJ Load characteristics Ventilation Ventilation is normally by fans, although controlled natural ventilation is becoming more popular. Fan control is based on achieving a given temperature, with background ventilation to disperse carbon dioxide and other gases produced by the birds. This is achieved by variable voltage (speed control), or by stepped switching of banks of fans 0.7 Ventilation increases over the life (and the weight) of the birds. The requirement is also greater during summer Heating Virtually all heating is provided by gas or oil and is either space or radiant heating. Electric heating is used on some smaller units 3.5 The heating load has a high maximum demand and low load factor (7%). Most heating occurs in the first two weeks of housing Lighting It is common to provide light for up to 23.5 h/day. If locally heated areas are provided during the first few days, these tend to be lit at a level of about 100 lx. Thereafter lighting intensity will be around 5 lx 0.09 Lighting sources vary considerably. The most popular are GLS lamps, compact fluorescent lamps and fluorescent tubes Feeding systems Feed is either supplied in dry meal form. Automatic conveying is standard 0.01 Feed troughs are filled automatically on a demand basis 35

35 Table 22: Egg production primary energy use. Type Description Typical energy consumption per 12 eggs, MJ Load characteristics Ventilation Ventilation is normally by fans, although controlled natural ventilation is becoming more popular. Fan control is based on achieving a given temperature, with background ventilation to disperse carbon dioxide and other gases produced by the birds. This is achieved by variable voltage (speed control), or by stepped switching of banks of fans 0.44 Ventilation is required 24 h/day with maximum demand during periods of highest temperature, i.e., summer and mid-afternoon Lighting The laying potential of the hen is very dependent on lighting intensity and period. Typically a lighting intensity of 5 15lx is used. Most buildings are windowless entirely artificially lit 0.12 When birds arrive, the lighting period is 11h/day and this is increased to 14h/day over a few weeks. Theoretically the lighting period could take place at any time during the day, but practical considerations egg collection, bird inspection, etc. mean that it occurs during normal working hours Feeding systems Feed is supplied in dry meal form on an ad-lib basis. Automatic conveying is standard 0.07 Feed conveyors work intermittently Manure removal Droppings fall onto a conveyor 0.03 The belt is usually operated twice each day, although more frequent operation may be used to reduce ammonia emissions. Manure removal tends to occur during the lighting period because it can disturb the birds if it is done during the unlit period Egg collection and packing Egg collection takes place almost continuously during the normal working day. Fractional-horse-power conveyers are used 0.07 Egg packing is almost continuous during normal working hours. On multi-building sites, the buildings are emptied sequentially 36

36 Table 23: Cereal crop drying and cooling primary energy use. Type Description Typical energy consumption 5% moisture removal/t, MJ Load characteristics Low-temperature, storage drying The crop is dried over a period of one to four weeks in a deep bed by means of a fan blowing ambient-temperature, slightly heated or dehumidified air through distributed air ducts Seasonal summer/autumn load. Typically 20 40kW fan motors on automatic relative humidity control, with propane gas burners to give a maximum 5 C lift High-temperature, continuous-flow drying Grain is either gravity fed through a drying tower or conveyed in thin layers over a perforated surface while hot air is blown through it at C * plus 18** Large gas or oil direct-acting burners heating air with multiple axial fans, 15 20kW, for air handling * oil/gas consumption, depending on dryer type ** electricity all dryer types Crop cooling (cereals) Small volumes of ambient air are blown through the crop to cool it 18 Low-power fans, W, controlled by a differential thermostat and/or time switch. More frequently manual control is used. Night use is common The nature of energy use in the intensive livestock area matches the output of energyfrom-waste sources, which is steady throughout the year. For example, energy from waste digestion would be ideal as it is available all year round. An attractive characteristic of the pig industry is the constant demand for both heat and power. This would mean that using digested waste to provide heat and power through a combined heat and power system could be considered Arable production issues Most energy in mainstream arable production is used for tractors and other field equipment. The usage profile is highly seasonal Cereals For cereal production, energy use is highest at harvest time for grain drying, which uses both heat and motive power. As the most significant source of waste from cereal production is straw, this presents an obvious recycling opportunity Field vegetables and potatoes In arable farming, after grain production, the next most intensive area of energy use is for grading, storing and cooling of vegetable crops. Apart from field operations, energy is used mainly in post-harvest operations such as grading and washing, and most importantly for cooling. Use varies widely with the perishability of the crop. Highly perishable crops have to be cooled quickly, but there is little need for long-term storage cooling. Less-perishable vegetables, such as potatoes and cabbage, are cooled over a longer period and held in cool storage, some for periods of up to a year. 37

37 Table 24: Field vegetable and potato production primary energy use. Type Description Typical energy consumption per t, MJ Load characteristics Ambienttemperature storage Refrigerated storage Crop cooled and condition maintained by blowing ambient air with a fan controlled by a differential thermostat Crop cooled and condition maintained by either a combination of ambient and refrigerated air or by a totally refrigerated system depending on system and storage time High initial energy demand once store is filled for pull-down of crop to storage temperature. Holding phase through winter period is low demand. It is possible to restrict cooling equipment run time to low-cost periods. Run time for refrigeration equipment increases as ambient temperatures increase Large gas or oil direct-acting burners heating air with multiple axial fans, 15 20kW, for air handling Post-harvest crop processing vegetable packing house with shortterm refrigerated storage Rapid cooling facility for removal of field heat from crop. Packing houses require a high level of lighting for processing/ grading of crops. Personnel heating, conveyors and packaging equipment make up additional loading 68 (average) High load factor for year round usage typical. Peaks in demand are often created in cooling facilities for field heat removal from crop in summer and at peak business times, i.e. immediately before Christmas 4.2 On-farm, energy-from-waste options Energy usage and waste production data from section 4.1 can be used to assess the options for using on-farm energy from waste Dairy Energy usage 1091 MJ/yr per cow = 303 kwh/yr per cow. Thus the energy requirement for a typical dairy unit of 80 cows can be up to 24,000 kwh/yr (the equivalent of 2.7 kw as a continuous load). Approximately 66% of this power (1.8 kwe) is required as electricity and 33% (0.9 kwh) as heat. The energy cost for such a dairy unit would be only ~ 1000 per year. Available energy A typical dairy unit produces ~1600 t/yr of organic waste. From the AD good practice guide, the biogas available from cattle = 25 m 3 /t at a calorific value of MJ/m t would give 40,000 m 3 of gas; an energy output of ~960,000 MJ, equivalent to ~260,000 kwh. Therefore, the available energy from a typical dairy unit could be approximately 10 times its requirement. From the good practice guide, 1 m 3 of gas can give 1.7 kwh electricity; or 2.5 kwh heat; or 1.7 kwh of electricity plus 2 kwh heat if using combined heat and power. 40,000 m 3 of biogas would give 64,000 kwh of electricity (four times the requirement) and 75,000 kwh of heat (nine times the requirement). An AD system on a typical farm of this sort would produce 64,000 kwh/yr (at 7 kw approximate continuous demand) of electricity Pigs Energy usage 125 MJ per pig = 35 kwh per pig. Thus the energy requirement for a typical pig unit of 400 sows can be up to 150,000 kwh/yr at 17 kw approximate continuous load. Approximately 50% of this power (8 kwe) is required as electricity and 50% (9 kwh) as heat (both electrical and hot water). The energy cost for such a pig unit would be ~ 5000 per year. 38

38 Available energy A typical pig unit produces ~9900 t/yr of organic waste. From the AD good practice guide, the biogas available from pigs = 26 m 3 /t at a calorific value of MJ/m t would give 250,000 m 3 of gas; an energy output of ~5,800,000 MJ, equivalent to ~1,600,000 kwh. So, the available energy from a typical pig unit could be approximately ten times its requirement. From the AD good practice guide, 1 m 3 of gas can give 1.7 kwh electricity; or 2.5 kwh heat; or 1.7 kwh electricity plus 2 kwh heat if using combined heat and power. 240,000 m 3 of biogas would give 400,000 kwh of electricity (three times the requirement) and 480,000 kwh of heat (three times the requirement). An AD system on a typical farm of this sort would produce 400,000 kwh/yr (46 kw approximate continuous load) of electricity Poultry Meat birds Energy usage 4.3 MJ per bird = 1.2 kwh per bird. Thus the energy requirement for a typical meat-bird unit of 250,000 birds could be up to 2,100,000 kwh/yr (equivalent to 238 kw continuous load). Approximately 20% of this power (50 kwe) is required as electricity and 80% (190 kwh) as heat. The energy cost for such a poultry unit would be ~ 40,000 per year. Available energy Typical meat bird unit produces ~4125 t/yr of organic waste. From the AD good practice guide, the biogas available from poultry = m 3 /t at a calorific value of MJ/m t would give 300,000 m 3 of gas; an energy output of ~6,700,000 MJ/yr, equivalent to ~1,800,000 kwh/yr. For poultry litter burning, a calorific value of 14 MJ/kg is typical. The available heat would be 58,000,000 MJ/yr, equivalent to ~16,000,000 kwh/yr. The available energy from a typical poultry unit could be approximately 50 times its requirement. A poultry litter burner on a typical farm of this sort could produce about 5,000,000 kwh/yr of electricity (600 kw approximate continuous load) Layers Energy usage 0.73 MJ per dozen eggs = 0.2 kwh per dozen eggs. Thus the energy requirement for a typical layer unit of 20,000 birds (5.8 million eggs) could be up to 100,000 kwh/yr at 11 kw approximate continuous electrical load. The energy cost for such a poultry unit would be ~ 5000 per year. Available energy A typical layer unit produces ~820 t/yr of organic waste. From the AD good practice guide, the biogas available from layer poultry = m 3 /t at a calorific value of MJ/m 3. Thus 820t would give 100,000 m 3 of gas; an energy output of ~2,500,000 MJ, equivalent to ~680,000 kwh. From the good practice guide, 1 m 3 of gas can give 1.7 kwh electricity; or 2.5 kwh heat; or 1.7 kwh plus 2 kwh heat if using combined heat and power. 100,000 m 3 of biogas would give 170,000 kwh of electricity (about twice the requirement) and 200,000 kwh of heat. An AD system on a typical farm of this sort would produce 200,000 kwh/yr (approximate 23 kw continuous load) of electricity. Therefore, the available energy from a typical poultry unit could be up to 30 times its requirement Arable (cereal) Energy usage (for crop drying) 36 MJ/t electrical, 300 MJ/t gas/oil. Thus the energy requirement for a typical arable unit of 150 ha (at 0.14 ha/t of grain) = 10,500 kwh/yr of electricity (equivalent to 1.2 kw as a continuous load although only used for four weeks each year) plus 90,000 kwh of gas (equivalent to 10 kw as a continuous load). Therefore the energy cost for such a unit would be < 2000 per year. Available energy A typical arable unit produces t/yr of organic waste (high seasonal variability). A calorific value of 13 MJ/kg is typical for straw burning, thus the available heat would be approximately 8,000,000 MJ/yr equivalent to ~2,200,000 kwh/yr. Therefore the available energy from a typical arable unit could be up to 20 times its requirement. A straw burner on a typical arable farm could produce about 800,000 kwh/yr of electricity (equivalent to ~80kW continuous load) of electricity. 39

39 Table 25: Energy saving technologies and potential dairy sector. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting Pre-cooling of milk with mains water Inverter control of milk pumps improved energy use during speed control High-efficiency motors various motor applications Refrigeration heat recovery for water heating Potential energy reduction, % Implied industry impact, MJ/1000l milk Improving efficiency The following sections breakdown the areas where energy conservation practices and equipment have an application. For each sector, the possible contribution of energy production from recycling is discussed. The role of energy conservation and recycling When considering the contribution that recycling can make to the energy input of an enterprise, it is important to put the role of energy conservation first. Employing waste to produce energy and then for the energy to be wasted in inefficient practices is not conducive to the spirit of recycling Methodology for identification and quantification of energy conservation technologies The relevant energy conservation applications have been broken down on a system-bysystem basis (Tables 25 30). This information has been derived from the authors intimate knowledge of on-farm systems and past monitoring data, including recent work carried out for the government in connection with the Climate Change Levy. Savings have been projected by multiplying specific per unit output savings by an assumed realistic scenario uptake. Part of the assumption underpinning the figures relates to the updating of systems over the next 10 years. It is assumed that the average working life of buildings and systems will be 30 years. So, in 10 years time onethird of the building and equipment stock will be renewed. In the intensive livestock sector it is also reasonable to assume that many building and energy system components will be renewed and replaced at least once in the life of the building; so here, two-thirds of systems are likely to be replaced in the 10-year period. 40

40 Table 26: Energy saving technologies and potential pig sector. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting Lighting controls switching using automatic systems Thermostatic creep heating control for control of heating for young pigs Creep floor heated pads floor heating systems for young pigs Fan and/or duct system cleaning maintenance of ventilation components Improvement in fan selection matching fans to use Pig creep construction better insulation and construction of creep heating system Inverter drives speed and energy control for motors on pumps and feeder High-efficiency motors Duct design ventilation duct improvement Ventilation control system improvement general improvement in fan control Inverter control and three-phase fans improved energy utilisation during speed control Insulation improvement on intensive housing buildings Potential energy reduction, % Implied industry impact, MJ/pig

41 Table 27: Energy saving technologies and potential meat-bird sector. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting Lighting layout improvement an even level of light is important in bird production terms Improvement in fan selection matching fans to use Interlocked heating and ventilation control prevention of simultaneous use of heating and ventilation Building sealing during heating draught proofing Fan and/or duct system cleaning maintenance of ventilation components Duct design ventilation duct improvement Ventilation control system improvement general improvement in fan control Inverter control and three-phase fans improved energy utilisation during speed control Insulation improvement on intensive housing buildings Radiant heating radiant rather than convection heating High-efficiency motors various motor applications Potential energy reduction, % Implied industry impact, MJ/bird Very small 42

42 Table 28: Energy saving technologies and potential egg production sector. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting Lighting layout improvement an even level of light is important in bird production terms Improvement in fan selection matching fans to use Fan and/or duct system cleaning maintenance of ventilation components Duct design ventilation duct improvement Ventilation control system improvement general improvement in fan control Inverter control and three-phase fans improved energy utilisation during speed control Insulation improvement on intensive housing buildings High-efficiency motors various motor applications Potential energy reduction, % Implied industry impact, MJ/dozen eggs Table 29: Energy saving technologies and potential cereal crop sector. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting Improved control of grain drying equipment Dehumidifiers for grain drying improved energy utilisation during speed control of fans Improved ducting and air handling for drying various motor applications High-efficiency motors various motor applications Potential energy reduction, % Implied industry impact, MJ/grain t

43 Table 30: Energy saving technologies and potential horticulture. Energy conservation measure Monitoring and targeting energy awareness training Efficient light sources discharge lights to replace general tungsten lighting and improve existing supplementary lighting sources High-efficiency motors various motor applications Variable-speed motor drives pumping and irrigation Improved greenhouse heating controls More efficient greenhouse design Boiler flue gas condensers Decentralised boiler plant Combined heat and power Thermal storage Heat pumps for heating Potential energy reduction, % 5 80 (for night break) plus 5 (for supplementary) Implied industry impact, MJ/m 2 /acre

44 05 Techniques for waste recycling and energy recovery from waste We have the technology Different recycling techniques and technologies are needed to manage the entire range of waste materials. Organic waste can be composted and reused as soil improver and while it is composting it can produce heat. Plastics, batteries, oil, paper, etc., can be treated and recycled, and materials unfit for recycling can be incinerated to produce electricity. Nothing has to go to waste in the traditional route of landfill. The hierarchy of waste management options ranges from waste reduction (most desirable) to waste disposal (least desirable). However, given that waste reduction can, at best, only form a part of a waste management strategy, other options, short of disposal, need to be considered. These are reuse, recycling and reprocessing energy recovery. 5.1 Reuse, recycling and reprocessing Reuse The reuse of agricultural waste includes packaging designed for reuse finding new uses for products and packaging finding uses for organic wastes. Farmers are very successful and innovative in finding new uses for products and packaging. Similarly the reuse of natural wastes is common, such as the use of crop and produce waste for animal feed Plastics and packaging Most people are familiar with conventional reuse, where a product is designed to be used a number of times before becoming obsolete, for example, reusable food and drink containers and the retreading of car tyres. Recently, there have been significant improvements in packaging design to allow reuse. With the introduction of the packaging regulations there is now an incentive for manufacturers and suppliers to introduce reusable packaging. 27 This will help them reduce their costs and achieve their obligations under the regulations. Of interest to the agricultural sector are reusable containers for a number of agrochemical products (e.g., Ecomatic and Linkpak containers). However, the range of products and packaging used in agriculture is very large, and refillable containers will only represent a very small percentage of the UK market. The further development and improvement of reusable containers should be encouraged to increase their use by the farming community. Some farm plastics are suitable for reuse. Film kept for reuse should be stored in containers to prevent further damage to it. Plastic film can be manufactured to be photodegradable. Such films degrade at a fairly reliable rate, despite the variable climatic conditions in the UK Organic waste The most common method of reusing the organic wastes produced on a farm (such as manure and slurry) is land spreading. When properly controlled, land spreading is an environmentally safe way to recover value from such wastes allows farmers to reduce the amount of inorganic fertiliser applied to the soil leads to improvements in soil structure. Most agricultural wastes are organic and land spreading is currently the accepted waste management option for these materials if sufficient land exists for such action. Sensible planning, testing the nutrient content of waste and matching application rates to field crop requirements, can improve the efficiency of their use. Recommendations for applying livestock waste can be sought from a person qualified under the Fertiliser Advisers Certificate and Training Scheme (FACTS). How, when and where it should be applied are major issues. Data are available to help determine crop requirements, and systems such as the software MANNER can help decide on timing of applications to grassland, cereals and oil-seed rape. 72 If undertaken inappropriately, land spreading can lead to water pollution, soil contamination and deterioration of soil structure. 15, Silage The type of crop, the silage conservation system and storage facilities will have an effect on the volume and nature of the effluent arising. Silage effluent can, if suitably diluted, be fed back to ruminant livestock. Very early and late cuts of silage are likely to be wetter and give rise to more effluent Tyres Worn tyres may be reused, for example, tractor tyres can be made into yard scrapers, used for weighing down the silage film, etc. Remoulding and/or retreading of tyres may be possible if the tyre case is still sound. Alternatively, most tyre dealers/fitters offer a controlled disposal service at a small charge. 45

45 5.1.2 Recycling and reprocessing Waste recycling and reprocessing techniques reduce the demand for raw materials and maximise the value that can be extracted from them. Furthermore, waste recycling leads to a reduction in emissions to air and water, and minimises waste disposal impacts. The UK Government is committed to a substantial increase in recycling rates. This can only be achieved if action is taken in parallel on all three sides of the waste management triangle: collection reprocessing markets and outlets. For successful collection of waste, comprehensive publicity and information campaigns are needed. The government is looking to the industries with the expertise and knowledge to take this forward. Recycling of agricultural waste is limited at present, due primarily to the lack of widespread collection systems and reprocessing facilities. However, recycling techniques such as composting organic wastes could have a major impact on the waste arising from the agricultural sector in the medium to long term. Recycling options also exist for other specific agriculture wastes, such as plastics, metal, paper, wood, construction waste, batteries and oil. Batteries and used engine oil are classed as special wastes, and thus, when waste management controls are extended to agriculture, will need to be disposed of and/or recycled by a licensed agent; on-farm disposal/recycling will not be allowed. Similarly some construction wastes, notably asbestos, are also classed as special wastes Composting of organic farm wastes Composting is an aerobic process in which biologically degradable wastes are broken down to form a stable, granular material. The process is a complex interaction between the waste and the microorganisms within the waste; moisture and oxygen concentration are important process parameters. Compost provides the humus and nutrients essential for a healthy soil. By returning compost to the soil, the soil is rebuilt and maintained for sustainable production. This is a particular focus of the recently issued draft communication on soil protection. 84 Soil has been a neglected area of EU environmental policy. The Commission s proposals for a sixth EU environment action programme, published in January 2002, promised to fill the void, with soil protection now being the subject of one of the thematic strategies under the programme. The new communication, due to be finalised early 2002, is the first step towards this strategy. Decline in organic matter, caused by the intensification and specialisation of farming practices, undermines soil fertility and resistance to erosion. In England and Wales, the proportion of soils with less than 3.6% organic matter increased from 35 to 42% between 1980 and Organic matter is also an important carbon reservoir and the report suggests it may play a central role in mitigating climate change. It observes that a 0.15% increase in the organic content of Italy s arable soils would lock away as much carbon as the country emits annually from the burning of fossil fuels. It has been calculated that, for fertilisation of energy forest (crops/trees grown for burning to provide energy), the energy efficiency obtained through composting is eight times that obtained through incineration. When a tonne of waste is incinerated, the energy obtained can be ~2 MWh, while the energy value of the added humus on fertilisation of energy forest is equivalent to ~16 MWh. Composting in the UK is a growing industry, and is acquiring greater significance as a waste management option. A key issue facing the industry over the next few years will be complying with Landfill Directive targets in providing an alternative to landfill. Key factors in composting The breakdown of organic material during composting depends on many factors, all of which must be manipulated to increase the activity of the primary agents bacteria (including actinomycetes), moulds, and a variety of worms and mites. Secondary and tertiary agents then consume the by-products lower down in the chain. Therefore, anything that aids the proliferation of the primary consumers will enhance composting. The waste material must provide suitable conditions (see Table 31): carbon nitrogen (C:N) ratio oxygen availability other nutrients particle size aeration moisture content temperature ph. Methods for controlling the composting process will aim to optimise the process. Various handling methods and equipment are available, all of which will offer different benefits. The general experience in composting is that oxygen availability is the most important factor, and therefore equipment design tends to concentrate on the efficient transfer of oxygen to all parts of the composting material. 46

46 Table 31: Optimum conditions for composting. Key factors C:N ratio Moisture content Air flow Temperature Heap size ph Natural ventilation The oldest and simplest method of producing compost is simply to heap up the material and leave it. The decomposition is slow and nutrient loss may occur, however, no supervision is required at any stage. Domestic garden waste composting works along these lines. Midden stores on farms are a naturally ventilated form of composting. Windrows Value 25:1 to 30:1 50 to 60% 0.6 to 1.8m 3 air/day/dry kg or oxygen level at 10 to 18% 55ºC 1.5m high, 2.5m wide for naturally aerated heaps 5.5 to 8.0 Windrows are a traditional form of composting in which the material forms long rows, typically between 2 3 m high and 3 4 m wide. Optimum moisture content is around 50%, therefore dry material needs water adding prior to composting. If different materials are to be decomposed, they need to be mixed thoroughly before composting begins. Aeration of the windrow is achieved by turning the material. Overall composting efficiency is improved by transferring the material that formed the interior of the windrow to the exterior and vice versa. The composting process occurs faster inside the windrow where temperatures are higher; therefore, by exchanging material from the inside to the outside, greater uniformity in the final material is achieved. Table 31 shows the advantages and disadvantages of windrows. Windrow compost will usually be ready in about 10 months. After this period, the compost will be moved to curing and storage piles for another 40 days or more. Enhanced aerobic composting There is a wide range of improved mechanical composting systems, which all aim to improve the method of aeration so as to maintain optimum conditions within a decomposing system. Table 33 shows the advantages and disadvantages of forced aeration. Forced aeration will normally use one or more of the following principles: forced aeration stirring tumbling. Table 32: Advantages and disadvantages of windrows. Advantages Little capital investment Even-textured compost produced Disadvantages High labour and thus operating costs No temperature control One example of forced aeration is the IPS Composting System, which uses a series of bins to automatically turn the compost, reducing the composting time to approximately three weeks. A similar composting time is achieved with the Biomax Robotcompost, which agitates the compost and uses forced aeration. 30 Another Biomax technique also uses forced aeration, but without the agitation. This produces a final product within four to eight weeks, but the company states that the piles should be mixed once or twice during this period. Table 33: Advantages and disadvantages of forced aeration. Advantages Good temperature control Low running costs and labour demand Off-farm composting Centralised composting facilities could be set up to treat both agricultural and domestic waste, but cross contamination might arise from this waste management strategy. However, providing composting is performed in a correctly designed and operated unit, the temperature generated will be high enough to pasteurise the waste. Some companies offer mobile composting systems. 74 Several companies offer services to industrial companies, where they remove organic waste from the site and treat the waste by composting (amongst other techniques). 31 Markets for compost Disadvantages High capital investment Possibility of uncomposted areas in the material Compost for growing food crops is a form of closed-loop recycling, and, if the compost is made to an appropriate standard, its use in agriculture will provide a reliable market for bulk quantities of processed organic wastes. It will also have a wide geographical spread that would encourage the establishment of local composting units. The government recently set up a group to look at the market for waste-derived compost. 70 The group concluded that the principal barrier to more widespread use of compost was the generally negative perception of it as a product. The fundamental problem is the absence of nationally agreed and accepted standards (both for the product and the process). 47

47 The May 1999 Composting Association survey of the UK showed that there were 197 composting facilities operating in 1999, mainly in England (Figure 30), composting approximately 900,000 t. 32 Most of this was produced by 80 central composting facilities, with 52 community operations and 65 on-farm facilities. Benefits of a well-managed compost: Pathogens are killed by pasteurisation Weed seeds are destroyed Volume of waste is reduced by up to 50% more economic storage, handling and transport Stable product is produced Bad odours are eliminated Unattractive to vermin Soil structure is created and improved Nutrients are released into soil slowly Saleable material is produced Farm plastics The main disposal route for waste plastics is presently through landfill, with only a small amount of incineration and recycling. Traditionally, plastics have often not been recycled as the cost of recycling and decontamination can be high. Plastics have been identified as one of the most significant wastes from agriculture. 3 The management of films, or non-packaging plastics, has been a particular agricultural waste problem, not least because they are bulky, often heavily contaminated with soil (two-thirds of the waste s weight can be soil) and expensive to dispose of off-farm. Therefore, farmers have tended to bury or burn these wastes. However, when the waste management controls are applied to farm waste, these options will not be possible. The potential for recycling farm film was first discussed in the late 1980s. Investigation showed that, despite the difficulties, the film could be cleaned and recycled at a cost that was worthwhile to the reprocessor. However, the same study indicated that the costs associated with collection and transport to the reprocessing plant could be prohibitive. Figure 30: UK composting sites. British Polythene Industries (BPI), a manufacturer of plastic film, recognised the marketing benefits of offering a plastics recovery scheme, and invested in a reprocessing plant in Scotland. They established the Second Life Plastics scheme in 1988 to reprocess film to make plastic wood. The scheme was a technical success, with over 15,000 telephone requests in 1992 to collect more than 4,000 t of film. However, the scheme collapsed in 1993 due to a slump in the plastics market. The plant has a capacity of 10,000 t/yr and to remain economic, it currently receives film from Ireland and several other European countries, as well as from the UK. The Farm Film Producers Group was set up by BPI in 1994 this time sharing the costs with other manufacturers, who charged a voluntary levy of 100/t. The resources were used to fund a nationwide collection system through local agents who were paid 80/t to collect plastics from farms and transport them to the reprocessing plant. In 1996, this group fell into difficulties, and collapsed in Since 1998, farm film collection schemes have operated in a small number of areas (all supported by external funds, and transporting plastic to BPI s plant in Scotland), but no nationally coordinated scheme exists. However, the national collection network of approximately 30 agents around the country still meets regularly. Of the schemes currently operating, the largest is in Wales Second Life Plastics Wales (launched October 1999) with 5000 participating farmers and managed by P&N Birch. The scheme is funded (as a three-year project) under the EU Objective 5b programme, with financial support from the Welsh Office, MAFF and the Environment Agency. Farmers pay an annual membership fee of 27.50, which includes collection of the first 700 kg of plastic, and then 40.50/t thereafter (this is a subsidised rate, and at the end of the project will need to be at least doubled). Two vehicles collect directly from farms and transport the plastic to a sorting/baling yard in South Wales and then to the BPI reprocessing plant in Dumfries, Scotland. The scheme has proved successful, with an anticipated 9,000 t of plastic from 18,000 farms in Wales over two and a half years. Key success factors seem to have been extensive advertising and activities to raise awareness. Other film collection schemes operating include two in Scotland and one in Cumbria. The schemes in Scotland include the collection of film from approximately 2500 farms in the Dumfries and Galway region. The scheme in Cumbria is funded with landfill tax money and contributions from several 48

48 other sponsors. The scheme was established in 1999 and is coordinated by a working group, including the NFU and FWAG (Farming and Wildlife Advisory Group). It includes more than 20 collection points around the region (mainly livestock markets) managed by volunteers. Collections occur two to three times a year (over a period of two days), and farmers are charged per load. A load can include plastic film and packaging. The plastic is then collected by a contractor based in Dumfries who transports it to a yard in Scotland for sorting/baling prior to transport to BPI s reprocessing plant. One of the main problems with these schemes is that typically more than half of the weight delivered to the reprocessing plant is soil, debris and water. The scheme in Wales has been reasonably successful in changing farmers practices by raising their awareness that the cleaner the film, the lower the cost of collection. There are problems associated with the recycling of plastics: The high volume-to-weight ratio makes collection and transport to centralised points uneconomic Plastic packaging is usually contaminated Segregation of compatible materials is a problem owing to the wide range of plastics in use. However, it is possible to utilise mixed plastic waste in a polymer cracking process. This results in a hydrocarbon product similar to the naphtha feedstock used in petrochemical plants for the manufacture of bulk plastics. Ideally the process should be sited adjacent to existing petrochemicals plant with bulk plastics waste being shipped in by rail. Such a process could contribute effectively to the plastics recovery rate and would be true closed-loop recycling Batteries Batteries are generally classified into two main types, automotive and consumer. Automotive lead acid batteries are usually recycled. The lead plates are re-smelted, the plastic cases recycled, and the sulphuric acid can be used as low-grade acid or regenerated. The value of the lead generally offers an economic incentive for the recycling of lead acid batteries. Automotive batteries from farms are classified as special waste because of their contents, and there is a duty-of-care requirement for the farmer to ensure that they are disposed of correctly. The annual quantity of waste batteries arising from agriculture is about 500 t. Occasionally old batteries can be reused for powering electric fencing Oil All waste mineral oils are classified as special waste, although small amounts (5 l for disposal, 20 l for recovery) can be moved without the provision of consignment notes. The annual production of waste oil from agriculture is about 25,000 t. Oil is a highly polluting substance and was responsible for more pollution incidents than any other group of substances, according to the Environment Agency s pollution incident database for To facilitate oil recovery, many vehicle maintenance companies offer machinery oil take-back schemes. Alternatively a number of local authorities operate collection recycling initiatives, for example the Oilcare scheme. There are three main management options for dealing with waste oils: regeneration combustion after treatment combustion without treatment. Article 3(1) of the Waste Oils Directive requires priority to be given to the regeneration of waste oil where technical, economic and organisational constraints allow Scrap metals Recycling is often the best practicable environmental option for waste metal. Scrap metals represent the largest volume of industrial material that is recycled. Recycling provides high-grade feedstock for refining processes, and reduces the use of raw materials, energy and the quantity of residues arising from the process. The cost of recovery, collection and sorting tends to be favourable compared with the higher costs of producing metal from metal ore. Scrap metal wastes are collected mostly through a well-established infrastructure, passing from the smaller scrap metal yards to the main dealers. Waste metal arising from farms is recycled through this infrastructure Paper Waste paper, which includes boards, boxes and cartons, can be categorised into groups according to recovery use. The main paper waste arising from farms falls into one of two groups: Kraft grades the largest single group and generally from brown, unbleached packaging materials, such as corrugated cartons. The strong fibres make kraft grades essential for recycling for new packaging. Low grades mixed papers that are uneconomical to sort, but are usable for packaging and speciality boards. The preferred waste management option for waste paper is recycling, although energy recovery through incineration and landfill are also used. Recycling of fibre is considered to be the priority and is the best practicable environmental option. 49

49 Pesticides and medicines The recent proposal by the government for a tax on the use of pesticides was dropped in favour of a voluntary stewardship package that is due to come into operation in the near future. Farmers need to dispose of pesticides and veterinary medicines correctly, and it is important to have a clear strategy for dealing with such wastes. It is the responsibility of the farmers under their impending duty of care to ensure correct disposal as they own the waste. Generally, pesticides (including sheep dips) are not recycled as they are hazardous substances. They should be disposed of in an appropriate and approved way. 5.2 Energy recovery from farm waste Energy can be recovered from waste in a number of ways. Clearly, incineration of the waste can provide a direct source of energy. Similarly, some waste (poultry litter and straw) can be used as a fuel substitute in conventional energy generation systems. More-indirect energy recovery techniques are those where the energy is released as a by-product of a recycling process (for example from anaerobic digestion). Energy recovery processes must be considered in the context of an integrated approach to waste management that encourages waste minimisation, and reuse and recycling. Whenever energy is recovered from waste, the potential for combined heat and power (CHP) technology should always be considered in order to maximise the amount that is recovered. We have the technology CHP is a highly fuel-efficient technology that produces electricity and heat from a single plant. When electricity is generated, only a small part of the input energy is converted into electricity (25 50%). The remainder of the energy consumed is dissipated through cooling systems as waste heat. If a suitable use can be found for this heat, for example, in nearby buildings, the heat can be recovered, raising the efficiency of the process to as much as 80 90% and saving up to 40% on fuel bills. The government is working with industry to promote the wider uptake of CHP because of its environmental and economic benefits. Every 1000 MW of CHP can reduce energy costs by 100 million and carbon emissions by around 1 million tonnes per year. CHP will be a key element in achieving the aims of the Kyoto Protocol, which requires the UK to reduce its greenhouse gas emissions by 12.5% by , and to move towards a domestic goal of reducing carbon dioxide emissions by 20% by The techniques for energy recovery from waste can be divided into two broad groups: Direct energy recovery, where the waste is burnt to provide heat Indirect energy recovery, where the waste is processed in some way to provide a fuel Direct energy recovery Incineration Waste incineration is probably the most technically advanced waste management option available at this time. There is a wide variety of combustion systems, some developed from boiler plant technology and more novel techniques such as molten-salt and fluidised-bed incinerators. It is also the most strictly regulated option, with European directives continually tightening the emission limits applied to waste incinerators. 48 Energy is recovered from waste in the form of heat and is used to generate the high-pressure steam necessary to power electricity generators. Typically, around 10% of the electrical energy produced is used on site, while the remainder is exported to the National Grid. With conventional power plant, the waste heat from the turbines is discarded. In CHP plants, this residual energy is recovered for use in district heating schemes. This improves the thermal efficiency of the process (from around 22% to as much as 75%) and provides a further source of revenue. Incineration facilities include mass-burn systems that process large waste streams (such as municipal waste) with very little pretreatment. These systems are usually large, processing more than 500 t of waste per day. There are also smaller modular-burn incinerators that are designed for use by local communities. These typically process between 50 and 250 t of waste per day, and require some waste sorting prior to incineration. Traditionally, farmers have used incineration as a waste disposal route without energy recovery. On-farm incineration will no longer be practical when agricultural waste becomes reclassified as controlled waste. Moreover, there are no single-farm-sized incinerators available that incorporate energy recovery Plasma arc destruction Incineration of municipal waste typically reduces its volume by around 90%. However, this volume reduction is compromised by the additional waste generated in cleaning the exhaust gases. This normally involves the addition of lime to neutralise acids and of 50

50 carbon to remove residual organic species such as dioxins. Filtration follows to remove any particulates (fly ash). Around 30% of the capital costs of a conventional incineration plant is attributable to the stack-gas clean-up system. This is likely to increase significantly as tighter discharge limits require the installation of additional treatments. Gas-treatment residues are treated as hazardous waste. Alternative, heat-based destruction systems for mixed wastes, such as municipal solid wastes, are being developed from processes already operating in the metal refining industry. These avoid the large volumes of air required to support combustion and typically use plasma-arc heating (the energy released by an electrical discharge in an inert atmosphere) to raise the temperature of the waste to anything between 3000 and 10,000 C. This converts organic material to a hydrogen-rich gas and noncombustibles to an inert, glassy residue. The gas produced (which is relatively uncontaminated) is suitable for generating electricity to support the process. The volume of gas discharged from these processes is generally less than 10% of that generated by incinerators using the same waste Substitute fuels Many wastes contain materials that have a high calorific value and are suitable for use as substitute fuels in industrial processes. 54 There are examples in common use in the UK, such as scrap tyres, plastic containers and solvent wastes for firing cement kilns, where up to 40% of carbon-based fuel can be substituted by waste Feedstock substitution Another potential application, not used in the UK, is the use of mixed plastic waste as a feedstock in blast furnaces producing pig iron. Coal, oil or natural gas (essentially a convenient source of carbon) act as a reagent to reduce the iron ore to metal. Mixed plastic waste can be used as a substitute source of carbon. The process has been adopted by the iron and steel industry in Germany, which used 100,000 t of waste plastic for this purpose in Electricity from poultry litter The UK poultry farming industry produces more than 1.5 million tonnes of litter per year from broiler poultry farms. This litter is a mixture of wood shavings, straw or other bedding material, as well as poultry droppings. It is an excellent fuel for electricity generation, having nearly half the calorific value of coal. There are four major poultrylitter-burning power stations projects in the UK (see Section 8). In an electricity generating plant, a furnace burns the litter at very high temperatures (typically 850 C) to heat water in a boiler to produce steam. The steam drives a turbine linked to an electricity generator. The electricity is exported into the local electricity grid, and the steam is condensed back into water by an air-cooled condenser before being recirculated to the boiler. A power station that burns poultry litter will collect the litter from surrounding companies and transport it to a specially designed storage facility that is maintained at negative pressure to prevent the escape of odours. 37 There is no solid waste from this process. The solid by-product is a valuable nitrogen-free ash, rich in potash and phosphate, which can be sold as a fertiliser. This ash is recovered both from the furnace and from the exhaust flue gases. The main constituents of the fertiliser produced are given in Table 34. These plants produce very low levels of gaseous emissions from the chimney because of the clean chemical make-up of the fuel. There are a number of environmental benefits to processing poultry litter in this way: pollution from conventional disposal methods is reduced bio-security is improved soil nutrients in the manure are reused gaseous emissions are cleaner than from traditional power stations. Energy recovery from poultry litter can, therefore, encourage improvements in poultry farming methods. Constituent Calcium (as CaO) Sulphur (as SO 3 ) Magnesium (as MgO) Sodium (as Na 2 O) Manganese Iron Boron Copper Molybdenum Zinc Table 34: Major constituents of fertiliser from burning of poultry litter. Amount 20% 10% 5% 0.6% 2500ppm 500ppm 150ppm 500ppm 140ppm 400ppm 51

51 Electricity from straw burning Some baled straw (about 200,000 t) is already recycled as fuel for a purpose-built power station. This is about 2% of total straw production. It is estimated that another two to three million tonnes of straw could be available to power stations without influencing supply or prices for livestock farmers who buy straw. On-farm, outside storage of straw to be used for power station fuel leads to a considerable amount of wastage. The BAGIT project aims to develop a technology that will optimise the co-firing of biomass with natural gas. 38 Work started in December 2000 and will continue until December The results from the project will provide an indication of the applicability of the project to installations in the range 5 to 30 MW with low emissions and good efficiency. The AD process reduces the volume of the solid organic matter by as much as 60%, leaving material that resembles peat. As AD requires the absence of air (more specifically oxygen), the process must take place within a closed vessel. Differentiation between anaerobic digesters can be made on the basis of the amount of solids present within them (Table 35). Before constructing an anaerobic digester, it is important to understand clearly what it is Table 35: Comparison of anaerobic digesters, based on solids content. Design Solids, % Low solids Several designs available, similar to existing technology 4 8 required to do, as this will affect the type of system needed and its associated costs. For example, a plant may be built to make landfill more acceptable, or to generate power and sell the digestate as a usable material. If the methane is to be used for energy generation (either heat and/or electricity) there will also be issues with the emission of nitrogen and sulphur oxides, and any particulates produced. Similarly, during the digestion stage, ammonia can be produced and this must be handled correctly. High solids Newer technology and less experience in handling high-solids-content material Indirect energy recovery Volume Large volume due to high water content Smaller volume for same organic loading Anaerobic digestion Gas production rate Up to two volumes per active reactor volume Up to six volumes per active reactor volume Anaerobic digestion (AD) is the biological degradation of organic compounds in the absence of oxygen. It produces methane gas and a residue (digestate) that can be used as a soil improver. Toxicity Leachate De-watering Dilution minimises toxicity impact High water content may cause problems Can be expensive and require large facilities Salts, heavy metals and ammonia can cause problems Generation of leachate reduced due to lower water content Simpler solutions at lower cost are viable Sewage sludges have been treated by AD for many years, with the methane gas being used to meet on-site power and process heating requirements. AD has also been used to treat cattle slurry on farms. It is possible that the process could treat the organic fraction of municipal waste, but there are reservations about the cost and the high degree of segregation required to produce a marketable digestate. 52

52 There are two types of AD process: Mesophilic digestion The digester is heated to ~30 35 C, the feedstock remains in the digester for days. This process tends to be more robust and tolerant than the thermophilic process, but gas production is less, larger digestion tanks are required and sanitisation, if required, is a separate process. Thermophilic digestion The digester is heated to 55 C. Residence time is days. These systems result in higher methane production, faster throughput, and better pathogen and virus destruction than mesophilic digesters. However, the technology is more expensive, and requires greater energy input, and more operational input and monitoring. Whatever the process used, a considerable proportion of the digestible solids is converted into gas (biogas). This can be burned in a conventional gas boiler to supply heat to nearby buildings (including farmhouses), and to heat the digester. It can also be used to power machinery or vehicles. Alternatively, it can be burned in a gas engine to generate electricity, which can be used on-site or supplied to the local electricity network. When an anaerobic digester is used to supply electricity, it is usual for it to be part of a CHP system. The gases produced by anaerobic digesters are often corrosive. This has caused problems with the associated electrical generators. Some manufacturers claim that these problems have been much reduced, (for example, in CHP schemes using Stirling cycle engines). A number of technologies for cleaning the off-gases from AD are currently under investigation. These include membrane separation, molecular sieves, pressure swing adsorption and cryogenic systems. Such technologies may also be able to remove carbon dioxide, giving a more methane-rich gas, which can give better fuel efficiency. AD can be a continuous process. As fresh feedstock is added to the system, the digestate is pumped out of the digester to a storage tank (where biogas continues to be produced). After storage for an appropriate time, the residual digestate can be applied directly to the land, or further separated into fibre and liquor. The fibre can be used as a soil conditioner, and the liquor can be used as fertiliser as part of a crop nutrient management programme. AD products are, therefore, potentially very valuable to farmers reducing their energy bills and providing soil conditioner and fertiliser. Despite the clear benefits of such a system, only a few farmyard anaerobic digestion projects have been undertaken in the UK. Those that have been developed are mainly small-scale systems. Of the 20 or so units known to have been installed, only a few are still in operation. This is because most farmyard digesters used for treating manure and other high-solid-content wastes are converted liquid digesters based on technology designed to treat slurries and sewage, and, therefore, not really suitable. However, there are prospects for the further development of AD and the introduction of centralised digesters for organic waste treatment (in addition to localised units). These centralised digestion plants will take waste from a number of surrounding farms within a radius of about 10 km. A plant capable of generating 1 MW of electricity would require a digester of ~10,000 m 3 capacity and is likely to cost between 3 and 6 million. 26 The electricity produced would be supplied to the National Grid, and, if possible, the heat produced would be fed into district heating networks or to local industrial users. There is great potential to develop AD plants in the UK. British BioGen has proposed a programme to install 50 centralised AD plants, 100 on-site agri-industrial AD plants and 500 on-farm AD plants in the UK by The Portagester A recent AD development is the Portagester system, a low-cost, mobile, modular anaerobic digester that, like conventional AD, converts livestock manure (and household waste) into fibrous material and energy. 41 The system treats high-solid-content organic wastes and, if required, liquid organic wastes. The Portagester plant is clean and compact. The process is carried out in heated, sealed vessels, which prevents cross contamination and disease-spreading risk from birds, rodents and insects, and also eliminates pathogens, fungal spores and parasites. As the system uses more than one waste vessel, it has the advantages of true batch processing and traceability. It is possible to take feedstock from a number of different waste streams and treat it all within the same installation. Contaminants affecting the system could then be traced back to source. 39 The system is engineered to accommodate high-solid-content waste, so the process overcomes problems such as grit and solid waste accumulations in the liquid digester, thus alleviating blockages and maintaining digester capacity. 53

53 The system is operated as a batch system in two phases: 1) The solid-phase uses digester vessel(s) based on modified transportable waste skips, containers, wagons or trailers as anaerobic reactors. Once the contents are loaded and the container is sealed and positioned at the digestion site, liquor produced during the liquid phase is circulated through the contents during the digestion period. The solid phase has a 3 to 15 day retention time, depending on feedstock, temperature and operating methods. The contents of this phase are usually loaded into the digester at the waste-producing site. 2) The liquid-phase digester receives leached liquids produced by the solids digester and can also take liquid wastes directly. It is similar to a sewage treatment works sludge digester or conventional farm digester. One or both phases can be thermophilic in order to convert a greater proportion of the waste than with mesophilic digestion, to achieve a faster reaction rate or lower retention time, and to effect pathogen destruction. This means a comparatively smaller plant and corresponding cost economies. Biogas is derived from both phases, which, when used in combined heat and power units, can make the site self sufficient in heat and electricity and enable larger plants to export energy. The Portagester system offers a costeffective anaerobic treatment option for local communities and/or groups of farms, rather than the larger-scale centralised AD option in relation to transport costs and disease transmission. A prototype Portagester, a thermophilic, C, high-solids anaerobic digester, has been constructed for demonstration purposes and is currently treating farm waste in Hampshire Pyrolytic waste treatment In pyrolytic waste treatment, organic waste is heated in the absence of air to produce a mixture of gaseous and liquid fuels and an inert, solid residue (mainly carbon). Pyrolysis generally requires a consistent waste stream such as tyres or plastics to produce a usable fuel product. Currently, there is only one pilot plant in the UK; this uses old tyres. However, current work is looking at pyrolytic liquefaction of agricultural waste. The key feature of this is the total recycling of agricultural wastes and residues into a unique and valuable fertiliser that can be safely used in a range of agricultural and horticultural applications. This process produces no waste, as all the by-products are either used in the process as an energy source, or as essential components of the resultant liquid fertiliser Fermentation Fermentation converts the sugars in agricultural products to liquid fuels principally ethanol, but also some methanol. Whilst fermentation could be considered for waste treatment, it is only commercially viable where crops are specifically grown for the purpose of producing fuel. Since these energy crops are not waste, the process will not be discussed further Gasification Gasification heats carbon-based wastes in the presence of air (and sometimes steam) to produce fuel-rich gases. The technology is based on the reforming process used to produce town gas from coal, and requires industrial-scale plant. At the end of 1998, dumping sewage sludge at sea was stopped. In response to this Northumbrian Water has proposed gasification as a process for the treatment of its sewage sludge. 5.3 Conclusions Many recycling and energy recovery techniques have been developed that are applicable to the different forms of farm waste. While some techniques are improved versions of traditional waste management processes (such as the composting of organic waste), others are processes that have been transferred from other industries and adapted for use with farm waste (e.g., anaerobic digestion). To be commercially viable, some farm wastes (e.g., plastic films) have to be recycled at central reprocessing facilities, which may be dedicated to farm waste or may include farm waste with industrial and municipal waste streams. In addition to waste management through reuse, recycling and reprocessing, energy recovery is becoming increasingly important. This energy can either be recovered directly through burning of agricultural waste products, or indirectly through the collection of by-products (e.g., methane). Whatever the form of energy recovery used, systems that incorporate combined heat and power schemes should be used. This maximises the value that can be extracted from a particular waste product. In summary, the principal waste management techniques applicable to the processing of farm waste are recycling composting plastic film reprocessing energy recovery poultry litter burning straw burning anaerobic digestion. 54

54 06 Policies and legislation The law of the land As the UK becomes more aligned with EU policies, old legislation is changing to make way for harmonised directives. This is making waste recycling and energy production much more attractive and will help drive the take up of technology. Farms and local authorities will, however, need financial assistance to cope with so-called controlled waste edicts. Determining what constitutes waste is a complex issue. This section looks at the legal definitions of waste, and in particular how these definitions and exemptions affect agriculture. 6.1 The legal definition of waste The definition of waste in force in England and Wales is any substance or object which the holder discards or intends or is required to discard Controlled waste Controlled waste is waste that must be managed and disposed of in line with waste management and other waste-related regulations. It does not need to be toxic or hazardous to be a controlled waste. Certain animal wastes are specifically exempt from the duty-of-care requirements applied to other controlled wastes Special waste Special waste is hazardous waste that requires additional controls. A controlled waste is defined as special if it is on the EU s hazardous waste list and has one or more listed, hazardous characteristics. 40 A consignment note system must be followed for the transfer of special waste, including pre-notification to the UK Environment Agency Agricultural waste Agricultural waste is from a farm or market garden, and includes organic matter such as manure, slurry, silage effluent and crop residues. It also includes packaging and films, and animal treatment dips. 6.2 The position of agriculture At present, waste from agricultural premises is excluded from the definition of controlled waste, and hence is not subject to the waste management licensing regulations, or other waste controls such as the duty of care and registration of carriers. These controls are to be extended to agricultural waste. As a consequence of this, it will be necessary for farmers to apply to the Environment Agency for a waste management licence to carry out operations that are not exempt from licensing, such as disposal of plastics. The legal obligations and costs associated with holding such a licence are likely to mean that farmers will prefer to send some wastes to an authorised waste disposal company for recovery or disposal Legislation and regulations The main environment regulations applicable to agriculture include general pollution offences and abstraction licensing under the Water Resources Act The Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations were introduced to address serious polluting discharges arising from the livestock sector. 20 Other environmental regulations introduced to implement EC directives include the NVZs regulations and the groundwater regulations. 21,42 The main waste management legislation that applies to controlled waste, and that will be applicable to agricultural waste includes Environment Protection Act 1990, Section 33; which states that it is an offence to deposit controlled waste on land without a permit 43 Environment Protection Act 1990, Section 34; which imposes a duty of care on all those who produce or handle controlled waste. This duty is to keep waste safely, to transfer it only to authorised persons and to provide an appropriate transfer note 44 Environmental Protection (Duty of Care) Regulations 1991; which require all those subject to the duty of care to keep records of waste transferred and/or received 45 Waste Management Licensing Regulations 1994; which set out procedures for obtaining a waste management licence Obligations and decisions When agricultural wastes are classified as controlled waste, there will be an obligation on the part of the farmer to decide whether the waste should be treated as special waste under the Special Waste Regulations Some wastes from agriculture that may be classified as special waste, include asbestos cement from buildings, and oil and batteries from machinery. Where disposal is already subject to a permit under the groundwater regulations, dual control will not be applied. 42 The majority of non-natural materials generated on farms will fall under the definition of controlled waste. The extension of waste management controls to agriculture will effectively end on-farm disposal of plastics such as farm films. copies available from HM Stationary Office 55

55 However, organic materials that are put to beneficial use in a properly controlled manner (following the MAFF [now DEFRA] Codes of Good Practice), such as manures and slurry, will be classified as by-products, and thus waste management legislation will not apply. Organic materials in excess of beneficial use are considered wastes, so farms producing more manure than can be used on the available land in accordance with the guidelines are legally obliged to dispose of the excess. Table 36: Biowastes suitable for biological treatment or land spreading. Waste code Description EEC directive Agricultural waste Sludges from washing/cleaning Animal-tissue waste Plant-tissue waste 86/278/EEC 90/670/EEC 90/670/EEC Biowastes suitable for biological treatment Animal faeces, urine and manure 90/670/EEC The biowastes shown in Table 36 are, in principle, suitable for biological treatment and/or land spreading. A waste management licence is required by anyone who proposes to deposit, recover or dispose of waste. Licences are issued by the Environment Agency in England and Wales. However, small-scale composting sites, probably community groups and on-farm facilities, are likely to be exempt from waste management licensing. Under the Waste Management Licensing Regulations 1994, the land spreading of certain wastes is exempted, as a waste-recovery operation, from waste management licensing controls if it complies with certain rules. 18 The exemption applies if the land spreading of the waste will benefit agriculture or give ecological improvement; no more than a specified amount of the particular waste is applied to each hectare of land; and the Environment Agency is informed in advance about the proposed land spreading. A recent study by ADAS has shown that the biological process of composting inevitably gives rise to some degree of odour and the release of potentially health-threatening microorganisms into the atmosphere as bioaerosols. ADAS advises that each potential composting site is assessed for odour and bioaerosol nuisance, taking into account the composting process employed, the scale of the enterprise and the materials used. The EU is currently developing a directive on composting Energy from waste There is a wide range of international and national legislation that affects recycling and energy from waste. International, national and local policy are often major driving forces for any technological development, such as AD, which can be classed as near market. Certain policies and legislation may be proactive in implementation and cover a broad range of issues due to the multiple benefits from the anaerobic digestion of organic wastes. For example, carbon dioxide reduction, renewable energy generation, sustainable agriculture, or rural development Incineration Legislation covering incineration is contained in the EU directive on the incineration of waste, which covers incineration and coincineration plants. 48 However, plants that treat only vegetable waste from agriculture, and animal carcasses are exempt from the scope of the directive. 6.3 European Union policy and legislation EU policies, programmes and legislation have been identified in order to study their impact on the implementation of energy-from-waste technologies. Towards Sustainability 5th Environmental Action Programme This considers renewable energies, and proposes support measures, including fiscal incentives. It underlines that increasing the share of renewable energy sources will play a key role in meeting the EU s carbon dioxide 56

56 emission reduction objectives. Agriculture was selected as one of the target sectors of the Fifth Environmental Action Programme. European Programmes Supporting Renewables 50 Within the Energy, Environment and Sustainable Development Programme of the Fifth Framework Programme for Research and Technological Development ( ), key actions 19 and 20 relate to Cleaner Energy Systems Including Renewables and Economic and Efficient Energy for a Competitive Europe respectively. EU Commission White Paper Energy for the Future: Renewable Sources of Energy 51 This proposes a strategy and action plan for increasing the share of renewable energy sources in the energy balance of the EU. It describes a policy for the promotion of renewables requiring across-the-board initiatives that encompass a wide range of sectors: energy, environment, employment, taxation, competition, research, technological development and demonstration, agriculture, and regional and external relations policies. Agriculture is identified as a key sector for European strategy. With particular reference to biogas, the white paper estimates that the total energy content of landfill gas and digestible agricultural wastes in the EU exceeds 930 TWh. The contribution that can be made by biogas exploitation from livestock production, agri-industrial effluents, sewage treatment and landfill by 2010 is estimated at 180 TWh. A stronger exploitation of the biogas resource is in line with the strategy for reducing emissions. Biological Treatment of Biowaste Working Document (EU) 52 This states that member states should encourage on-site composting or anaerobic digestion whenever there are viable outlets for the resulting compost or digestate such as farmland. The requirement for biological treatment plants to possess a permit is highlighted, although for composting or anaerobic digestion plants producing less than 500 t of compost or digestate per year, exemptions apply. Less than 10 t/yr minimal permits are required Up to 100 t/yr the operator need only register with the competent authority Between 100 and 500 t/yr registration applies, the operator must sample once a year for heavy metals, and label the product. European Rural Development Policy The EU commitment to rural development is based on an increasing recognition and acceptance that, whilst farming remains a key economic activity in rural areas with major impacts on landscape and the fabric of the countryside, it is necessary to promote new economic activities and new sources of income in these areas. The successful diversification of rural economies requires the adoption of an integrated and multi-sectoral approach. The four main aims of the EU rural development policy, all of which can promote and support community integrated AD projects, are to promote economic and social cohesion, by maintaining and creating jobs to overcome barriers to development by encouraging diversification and improving infrastructures and giving facilitating access to new technologies to increase the quality of life (by preserving the environment, giving access to basic services) to maintain viable communities whilst preserving their culture and traditions. The Rural Enterprise Scheme operates in England outside Cornwall and the Isles of Scilly, Merseyside and South Yorkshire. Amongst the measures that it may fund are protection of the environment in connection with agriculture, forestry and landscape conservation as well as with the improvement of animal welfare. In Cornwall, the Isles of Scilly, Merseyside and South Yorkshire, equivalent schemes will operate under a different programme called Objective 1. The scheme s aim is to fund projects designed to revitalise the rural economy, which can include centralised AD and other energy waste plants. Another relevant programme is the Environmentally Sensitive Areas Scheme. There are currently 22 environmentally sensitive areas (ESA) in England covering over 1 million hectares of agricultural land (see Figure 32). In these areas, farmers are encouraged to adopt agricultural practices that will help to protect and enhance the environment. All farmers within the ESA s boundary are eligible to enter into 10-year management agreements with DEFRA, with an optional break clause after five years. Annual payments range from 8/ha to 500/ha, depending on the management practices adopted. In addition, payments are available for the provision of new public access and for a range of capital works that varies depending on the specific objective of the ESA. 57

57 The LEADER (Link Between Actions of the Rural Economy) community initiative was launched in The specific objectives of LEADER II ( ) are to support innovative, demonstrative and transferable measures that illustrate the new directions that rural development can take to increase exchanges of experiences and the transfer of know-how through a community rural development network to support transnational development projects. There is also a specific provision that permits the financing of pilot and demonstration projects, evaluation studies, information and dissemination exercises. EC directives with implications for AD From an agricultural perspective, the significant directives are those dealing with groundwater, drinking water and nitrates. While the drinking water directive does not concern agriculture directly, the groundwater directive addresses specific forms of agricultural pollution, while the nitrate directive focuses on farming practices. When considering water protection, one must also take into account the directive on marketing pesticides, which has clear implications for agriculture. Other relevant directives are those that relate to emissions, noise, storage, and the transport of waste. Groundwater 80/68/EEC seeks to control the direct and indirect discharge of certain substances into the groundwater. 42 It concentrates mainly on a list of prescribed substances, but also takes into account other substances or compounds formed that may have a deleterious effect on the taste and/or odour of groundwater and to render it unfit for human consumption. This may have implications if organic wastes are being spread in the vicinity of groundwater protection zones. Nitrate from Agricultural Sources 91/676/EEC was devised to reduce or prevent the Lake District Clun Exmoor Blackdown Hills West Penrith Dartmoor Cotswold Hills Pennines Yorkshire Dales North Peak District Southwest Peak Distict Norfolk Broads Shropshire Hills Breckland Upper Thames tributaries Somerset Levels and Hills Wessex Downs Essex coast North Kent Marshes South Downs Figure 31: Location of environmentally sensitive areas in England. Suffolk river valleys pollution of water caused by the application and storage of inorganic fertiliser and manure on farmland. 23 Formal compliance with this directive by the UK falls under a staggered timetable, designating, at present, a limited number of nitrate-vulnerable zones (NVZ). However, the European Court of Justice has ruled that the UK has failed to implement the directive properly and that the same measures must be implemented across the whole or most of the UK by the end of There are two options under consideration: countrywide application; or alternatively the directive allows the option of a more targeted approach on those areas where nitrate levels in water create particular environmental problems. Farmers will be required to comply with restrictions on the spreading of livestock manures on their land. The main financial burden will fall on dairy, pig and poultry farms. The main costs will be associated with installing extra manure-storage capacity and the higher cost of transporting manure for disposal on other land. Capital grants will be available to help farmers with the investments needed. Those farmers who need to upgrade their existing farm waste storage and handling facilities in order to comply with the restrictions, may be eligible for a grant of 25% of eligible expenditure (up to 85,000). 55 This funding may be used to help fund the installation of AD plant as an upgrade of a farm s manure storage capacity. The EC has also released codes of good practice with the objective of reducing pollution by nitrates and taking account of conditions in the different regions of the EU (Commission of the European Communities, 1998). Framework Directive on Waste 75/442/EEC provides a framework whereby the member states could control the disposal of wastes nationally, instead of locally, by the adoption of a common terminology and definitions of waste based on work carried out by the Organisation of Economic Cooperation and Development (OECD). 57 Member states must encourage the reduction of waste and its harmfulness by encouraging the development of clean technologies, technical product improvements, and disposal techniques. They must also encourage the recovery of waste and its use as a source of energy. Integrated Pollution Prevention and Control (IPPC) aims to provide measures and procedures to prevent whenever practicable or minimise emissions from industrial installations within the community, so as to achieve a high level of protection for the environment as a whole through an authorisation system based on the bestavailable technology. 21 This system will apply to new installations, while the existing ones have to comply within an eight-year period. Among the installations falling within the scope of the directive, are those for the intensive rearing of poultry (more than 40,000 places for poultry) and pigs (2,000 places for pigs in production (over 30 kg) or 750 places for sows). Those installations affected will have 58

58 to apply for a permit from the Environment Agency requiring them to use best-available techniques for the management of waste, air emissions, effluent, energy and soil and groundwater quality. Protection of the Environment, and in Particular of the Soil, when Sewage Sludge is Used in Agriculture 86/278/EEC (and 91/692/EEC) aim to control the use of sewage sludge in agriculture by establishing maximum limit values for concentrations of heavy metals in the soil and in the sludge, and maximum quantities of heavy metals (cadmium, copper, nickel, lead, zinc and mercury) that may be added to the soil. 58 There may be serious implications with regard to land spreading if sewage sludge is mixed with manure. For example, sewage sludge cannot be applied during the growing season for fruit and vegetable crops. In addition, waiting periods are sometimes required prior to harvesting or the grazing of land. 6.4 National policy and legislation Policy At present, the Department of Trade and Industry (DTI) has a policy of a watching brief on agricultural AD. However, support has been given to British Biogen for developing a market strategy for AD identifying and putting in place the structures necessary for market development. Help is also being provided to study environmental authorisation regarding the nutrient and fertiliser values of fibre and liquor respectively Legislation and planning Recently, the use of AD for the treatment of farm wastes in the UK has been given impetus. This was brought about by legislative pressures, such as the Environmental Protection Act 1990 and Water Act 1989, and by the government s renewable energy programme. Upon implementation of the EU nitrate directive, it is expected that legislation will be put in place regarding application rates and in identifying and extending NVZs. 23 Although there is no specific legislation on land spreading of animal manures, DEFRA has produced codes of good agricultural practice for soil, air and water, which provide guidelines for land spreading. 14,15,16 In 1994, the UK legislation regarding livestock waste emissions to air concentrated primarily on odour, whereas in the Netherlands and Denmark there has been an increased action to minimise ammonia and greenhouse gas emissions, arising from intensive livestock farming. Following the Danish example, the introduction of legislation requiring increased storage of slurry would provide greater incentives for developing AD. There are indications (Environment Committee, House of Commons) that UK policy has not provided adequate protection against potential infections from farm animals. 60 Increased controls on water pollution, including nitrogen and phosphorus release, will reduce the times and means by which animal wastes can be spread on land. It is reasonable to expect that such legislation may be implemented in the UK in the near future. Legislation relating to storage, the Control of Pollution (Silage, Slurry and Agricultural Fuel Oil) Regulations, specifies minimum standards relating to the design, construction and operation of certain agricultural storage systems. 20 The regulations require slurry stores to be sufficiently large for at least four months slurry production, unless a safe year-round disposal system is approved by the Environment Agency. The production of a farm waste management plan, which includes details of feedstock storage, digester operation and liquor spreading (including locations, rates and times), would normally be considered an acceptable alternative to the four-month rule. In order to assist planning, the UK Government has published a number of planning policy guidance notes (PPG). Those relevant to AD include PPG22, which advises on renewable energy, and PPG23, which advises on waste matters. The Waste Management Licensing Regulations 1994 regulate waste treatment and disposal activities so as to prevent harm to human health, pollution of the environment or serious detriment to local amenities. 18 A licence is required by anyone who treats, keeps or disposes of controlled waste. This includes household, commercial and industrial waste but not, at present, agricultural waste. Consequently, a centralised AD plant treating solely agricultural waste would not require licensing, whereas one utilising residues from, for example, food processing would. Furthermore, the inclusion of any controlled waste in the treatment process requires compliance with the pre-notification requirements of the regulations if the liquor is subsequently spread to land. 59

59 6.4.3 Programmes During the late 1980s and early 1990s, 50% investment subsidies were provided by MAFF (Farm and Conservation Grants) for the implementation of farm-scale AD plants. These have now ceased. There are currently no UK government programmes directly supporting AD, although the Renewables Obligation Order 2001, which came into force on 1 January 2002, gave the government the right to impose financial penalties on electricity suppliers who do not purchase sufficient electricity from renewable sources. 61 Renewables-generated electricity and heat will also be exempt from the Climate Change Levy. Thus, there is an onus on electricity suppliers to source increasing amounts of their supply from renewable sources. Market forces will dictate the price at which renewable energy can be sold. Many industry insiders feel that this strategy will not be enough to guarantee meeting the governments targets of 10% of UK electricity to be supplied from renewable sources by There are seven contracts involving AD of agricultural wastes awaiting development that were successful under the Non-Fossil Fuels Obligation, which proceeded The Renewables Obligation Order Conclusions There is a wide variety of international and national legislation and policy that could support the development of AD for agricultural wastes. EU policy is in favour of renewable energy generation and environmentally friendly waste disposal options, although this does not necessarily filter down to all the member states immediately. Although policy in the UK favours AD on environmental and energy grounds, extensive programmes and legislation to drive development forward are not in place. To assist the deployment of AD, legislation providing greater controls on the spreading of waste to land and emissions is required together with a comprehensive support programme. This programme could, for example, provide assistance for improving storage facilities, or the development of markets for products and by-products heat, liquor, fertiliser, etc. Widespread implementation of AD schemes, centralised or on-farm, is constrained by poor financial returns. Potential developers should seek guidance on local, national and European sources of funding. European Regional Development funds may be available to some regions. A list of the main UK national schemes and the grants available to farmers for conservation is given in Conservation Grants for Farmers

60 07 Mass balances Taking a further look at mass balances Farming is a diverse business. Cows, pigs, chickens, grain, all have different needs. Looking at how mass flows through the production cycle, it should be possible to identify the opportunities for better waste use and management. The classical mass balance concept (inputs and outputs in relation to products) can be applied to agriculture. However, it is important to recognise that the term agriculture represents a phenomenally diverse group of businesses, some of which have few similarities, and others that are intimately linked. The complete mapping of all resource flows to all sub-sectors of agriculture is outside the scope of this study. Sections 2 and 3 contain detailed information on the inputs and outputs of the various agricultural sectors. This section collates this information to give a clearer picture of the issues for each farming sector. The major focus of this report is recycling and energy from waste, it is useful, however, to undertake an overview of the elements of mass flow to get a feel for the relative components of important products, and also the particular nuances pertaining to agricultural products. This is the purpose of the mass balance as in the Biffaward programme. 63 Information on mass balance within each agricultural sector can be compared to the actual level of product consumption, and allows the relative impact of each business sector to be assessed. Figure 33 shows the relative UK consumption of agricultural food products. Figure 34 shows the relative feed/fertiliser inputs for each of the main agricultural sectors covered Input Domestic origin Materials used (and unused) Water Air Imports Indirect flows associated with exports Economy Material accumulation Material throughput (per year) Recycling Figure 32: The elements of mass balance. UK consumption kt/yr 12,000 10, Milk and milk products Pork Figure 33: Annual UK consumption by food type. Feed/fertiliser, kt/yr Milk and milk products Pork Figure 34: Annual UK inputs by food type. Poultry Poultry Output Air emissions Waste disposal Waste water Other Exports Indirect flows associated with imports Eggs Eggs Arable Arable 61

61 in this report. Figures 35 and 36 show annual organic and plastic waste production respectively. The mass balance for all food types is summarised in Table 37. The impact of each sector can be seen by looking at the waste output per kg of product (as shown in Figure 37 and Table 38). Organic waste t/yr 25,000 20,000 15,000 10, It can be seen that pork production has a high impact in terms of organic waste produced, and egg production results in the highest paper waste production. This identification allows the focus for recycling to be aligned on the most productive wastes in each sector. Another useful way of visualising the impact of each sector, is to perform specific mass balances for each one, so that the inputs and ouputs involved can be compared to the quantity of end product. Figure 38 shows the individual mass balances for a range of agricultural products. Plastic waste, t/yr 0 10, Milk and milk products Milk and milk products Pork Pork Poultry Figure 35: Annual organic waste production by food type. Poultry Figure 36: Annual plastic waste production by food type. Eggs Eggs Arable Arable 8 Organic Plastic Paper Organic waste, kg Milk and milk products Pork Poultry Eggs Arable Figure 37: Organic waste production per kg of product. 62

62 Table 37: Annual UK mass balance by food type. Inputs Outputs Sector UK consumption kt/yr Feed/fertiliser kt/yr Water kt/yr Plastic t/yr Paper t/yr Organic t/yr Plastic t/yr Paper t/yr Milk and milk products ,042 11,920 23, Pork Poultry Eggs , Arable 10, Table 38: Waste produced per kg of product. Organics waste, kg Plastic waste, kg Paper waste, kg Milk and milk products Pork Poultry Eggs Arable

63 Feed (4.7kg) Water (5kg) Paper (8g) Plastics (250mg) Bedding (2kg) Inputs Recycling opportunities Produce Waste Chicken (2.3kg) Organics (300g) Paper (25mg) Plastics (30g) Seed (30kg) Water (930kg) Fertiliser (80kg) Plastics (300g) Oil (95g) Chemical (0.4kg) Inputs Mass balance for the production of one 2.3kg chicken (taking 6.7 poultry crops per year). Mass balance for the production of one tonne of grain. Feed (205kg) Water (480kg) Plastics (50g) Glass (30g) Paper (22g) Inputs Recycling opportunities Organics Plastics Organics Paper Produce Waste Recycling opportunities Produce Waste Grain (1t) Organics (352kg) Plastics (0.3g) Oil (100g) Chemical/water mix (3kg) Pork (72kg) Organics (534kg) Plastics (50g) Glass (28g) Paper (22g) Feed (1.8kg) Water (4kg) Plastics (250mg) Paper (30g) Inputs Mass balance for the production of twelve eggs. Feed (300g) Grass Water (3kg) Fertiliser (100g) Fuel (10g) Plastics (2g) Inputs Recycling opportunities Organics Recycling opportunities Organics Plastics Oil Produce Waste Produce Waste Mass balance for the production of one litre of milk. Eggs and packaging (12) Organics (1.7kg) Plastics (1.6g) Glass (0.6g) Paper (2.3g) Milk (1l) Organics (3.3kg) Plastics (1.2g) Oil (0.2g) Tyres (0.4g) Organics Plastics Glass Mass balance for the production of one 72kg 'pork' pig. Figure 38: Mass balances for a range of agricultural products. 64

64 08 Waste treatment strategies Build a strategy Controlled waste directives will significantly reduce on-farm disposal or stockpiling. Now is the time to assess options and prepare the way for recycling and energy from waste schemes. Earlier sections have discussed the amount of waste produced from the various sectors of agriculture, and have examined available technologies for, and legislation governing, the treatment of this waste. This section examines which strategies are the most appropriate for treating the major agricultural waste arisings. DEFRA s Waste Strategy 2000 states that local authorities will need to make significant strides in recycling and composting, which the government intends to monitor. The main wastes generated by agriculture are organic, with more than 80 million tonnes produced per year. Plastics waste is the other main area worth consideration. As agricultural waste has always been excluded from the controlled waste definition, there has been little pressure or incentive for farmers to implement extensive waste control regimes other than those offering immediate cost savings. Very little infrastructure for collection of agricultural wastes exists. Consequently, wastes are usually disposed of on-farm or are stockpiled. The analysis of the appropriate treatment strategies is done on three scales: single, average-sized farm village/large farm/farm group county, parish/village group. This allows the opportunities for single farmers, villages, county councils or waste management companies to be assessed. 8.1 Relevant recyclable wastes The recyclability of wastes in agriculture has to be considered at two different levels; firstly, at the enterprise or individual business level, and, secondly, at the regional geographical level. If the recycling potential of a particular waste is commercially viable at enterprise level, then it is possible for a defined business to capitalise on that potential and to autonomously adopt the applicable recycling technique. If, however, the economic return on the recycling technique will not support the necessary investment by an individual business, then the other opportunity is to examine a shared approach with other businesses with a similar waste problem. In this way, capital requirement can be shared and advantage taken of the economies of scale. As few agricultural operations have the necessary waste throughput to warrant the independent adoption of recycling techniques, the suitability of shared resources has to be examined. Such initiatives often need to be driven externally, both technologically and financially, so that the necessary engineering and commercial expertise are brought to bear. There are many examples of this approach, see Figure 39 (e.g., the straw-burning power station at Ely (Cambridgeshire), and poultry litter burners at Eye (Suffolk), Thetford (Norfolk), Glanford (Lincolnshire) and Fife (Morayshire)). In developing a shared approach, it is necessary to look at both the net amount of waste available for recycling and the geographical concentration of that waste. Figure 39: UK biomass-fired electricity generating plants. 8.2 Single farms To assess the options for small-scale energy recovery, the options for the standard-sized farm units considered in Section 3 are looked at in the following categories: dairy pigs poultry layers meat birds arable (cereal) horticulture. These categories are also applied to the village/farm-group scale. 65

65 8.2.1 Dairy The major wastes in the dairy industry are organic, plastic, oil, and baler twine/net wrap. The dairy industry produces the largest amount of digestible organic waste in agriculture. However, as an industry, its energy use is not seen as generally high and is by no means steady throughout the day. A high proportion of the energy must be provided as electricity for cooling and pumping. There is only a limited requirement for heat Organic waste As dairy farming involves large land areas, sufficient land should be available for any organic wastes (FYM and slurry) produced on farm to be land spread (see Section 5). Any organic waste to be land spread should be aerobically composted before spreading. This is usually done in a midden store, although improved composting will give a better product with a number of beneficial qualities, but at extra cost. A second option is to use an AD system to treat the waste, giving an improved product for land spreading and generating gas, which can be used for heating and for generation of electricity on-farm, (see Section 4), or for sale through the National Grid. As shown in Section 4, the power available from a typical dairy farm unit is ~7 kw electricity and ~9 kw heat (as continuous load). On the same basis, the power required on such a farm would only be 1 kw of electricity and 2 kw heat (continuous load) (at less than 1000 per year). The figure for estimated energy costs for standard units is also given in Section 4, and can be used to estimate the payback period that may be expected for energy from a waste plant. Unless the plant is used to feed electricity to the National Grid, which involves additional cost and effort, then only the energy that can be used on site will have value. A detailed appraisal of the issues involved in connecting to the electricity distribution network can be found in Electricity Production Connected to the Local Network A Guide. 79 A typical cost for a small anaerobic digester would be tens of thousands of pounds, not including an electrical generation system. Thus, even on relatively large farms, the use of anaerobic digestion for single farm units is not economic. The smallest AD units commercially available operate at about 10,000 t/yr. 64 In the absence of any other costs to offset against the cost of AD, such as reduced disposal costs, reduced pollution risk or odour, the breakeven level for cattle farming (according to the Biogas Accountant program on the Enviro Berlin AG website, is about 3000 cows, i.e., about 40 average farms units. 67 Such a scheme is unlikely to be appropriate for a single farm without grant aid and or other income (and/or disposal costs to offset). If a grant of 50% towards the cost of installing such an AD unit was available, then studies from the 1980s indicate that the use of biogas for heat is the best option for most dairy farms of 200 or more cows, (assuming a market can be found for the separated fibre). An alternative way of utilising the benefits of AD on single farms, which reduces the capital outlay required and is thus more economically viable, is the Portagester system (see Section 5). The estimated treatment costs for the Portagester system are expected to be between 17 and 28 per tonne, compared to about 30 to 40 per tonne for landfill Flammable waste Dryer straw can be burned with other flammable waste, (see Section 5). The straw burned in such units should be clean, baled straw, however, use of slightly soiled straw might be possible. Heavily soiled straw could cause maintenance problems with the burner. A typical farm-size straw burner is 50 kw and burns ~30 t/year. The amount of flammable waste produced by a cattle farm unit alone is unlikely to be sufficient to warrant a strawfired boiler Plastics Traditionally farmers have used incineration for disposal of plastics. On-farm incineration will no longer be practical when agricultural waste becomes classified as a controlled waste. The only realistic way in which a small farm can dispose of plastic waste is to send it elsewhere for recovery or disposal. Recycling schemes for plastics exist in the UK, although usually for farm films not the plastic packaging most common in dairy farming (see Section 5). If available, takeback schemes run by suppliers will be the favoured option for plastics disposal Oil Waste oil can be recycled by burning for on-farm heat. Alternatively it can be used to protect over-wintered machinery or collected and recycled at a central location, for example the Oilcare scheme or similar local authority initiatives Pigs The major wastes in pig farming are organic, plastic, and glass. Energy use in pig production is maintained at a very high load factor throughout the year for heating, lighting and ventilation. Energy from waste options is therefore attractive as any energy produced will displace that bought in. 66

66 Organic waste As pig farming is more intensive than cattle farming in terms of number of animals per hectare, there is usually less land available for land spreading. If on-farm disposal is not possible, composting on-farm will only be worthwhile if the compost produced is of a suitable quality to sell or give away. Thus, natural-ventilation composting, as in a midden store, will not be adequate. A natural synergy exists between energy use and the potential for energy generation from AD of pig waste. A typical pig farm unit (400 sows) produces two to six times the amount of gas produced by a standard dairy unit (80 cows). In Section 4 the power available from a typical pig farm unit is given as ~46 kw electricity and ~56 kw heat (as continuous load). The power required on such a farm is given as 8 kw of electricity and 9 kw heat (continuous load) (at ~ 5000 per year). Thus, AD for a single pig farm unit is unlikely to be economic. In the absence of any other costs to offset against the cost of AD, the breakeven level for pig farming (according to is 3000 sows (about eight standard units). A lower figure than this is given by American workers, who report that more than about 830 pigs are required to achieve breakeven for the application of a swine waste treatment system. 65 A number of UK companies offer equipment and can give quotes. 34 Pig farmers should be aware of any local schemes or large centralised units that might be willing to take their organic waste. If a local water company has an AD unit that exports electricity to the grid, they might be willing to accept waste (see Figure 39). The Portagester system described earlier is also a viable option for pig farms, especially if a central collection depot unit exists in the vicinity Plastics The only realistic way in which a small farm can dispose of plastic waste is to send it elsewhere for recovery or disposal. Recycling schemes for plastics exist in some areas of the UK, though usually for farm films, and not the plastic packaging most common in pig farming, see Section 5. If available, take-back schemes run by suppliers will be the favoured option for plastics disposal Poultry The major wastes in poultry farming are organic. Although heating in meat bird production is the most significant load and may warrant energy-from-waste techniques, heating is not widely used in egg production. The digestion of layer waste has no immediate attraction for reuse on a production site. However, off-site digestion can be considered. The recycling of nutrients directly to arable land is particularly suitable as the nitrogen value of chicken droppings is high and they are uncontaminated by any added material Organic waste Poultry litter is an excellent fuel for electricity generation, with nearly half the calorific value of coal. There are no waste products from the process, as the ash produced is a nitrogen-free fertiliser, rich in potash and phosphate. Burning of poultry litter is becoming increasingly popular. It can also be composted or used in anaerobic digestion units. From Section 4, the power available from a typical poultry farm unit is 200 to 600 kw (equivalent continuous load). The power required on such farms would typically be only 200 kw (equivalent continuous load) (at 6000 per year). Although relatively large amounts of energy are available from standard poultry units, the cost of small AD units means that such technology is unlikely to be appropriate for all but the biggest poultry units. For incineration, although the energy available may be several hundred kilowatts for a standard unit, the cost of a farm-scale unit may makes it unattractive for all but the largest units. Export of electricity to the National Grid will be required to produce income. The associated costs might make such an enterprise unattractive at only a few hundred kilowatts output. The existing poultry litter burners have a generating capacity much larger than 1 MW. Poultry farmers should be aware of any local schemes or large centralised units that might be willing to take their waste Arable (cereal) The major wastes in cereal farming are organic, pesticide washings, and plastics. The largest recyclable organic residue is straw, which can be incinerated to produce heat or generate electricity. A natural synergy exists between the need for heat to dry grain and the supply of straw Organic waste Much of the straw produced in the UK, which could potentially be a waste product, is baled and put to agricultural use. However, there is still a surplus, which ETSU gives as 4.5 million tonnes per year; typically ~70 t/yr for a standard arable farm unit. Since the 1992 ban on in-field straw burning the major disposal route has been ploughing-in. The preferred use for surplus straw is as fuel in a suitable on-farm boiler (Figure 40), providing heat for hot water, buildings and grain drying and other operations, thus cutting energy bills and avoiding ploughing-in costs. The ash from the boilers can also be used as a fertiliser. Approximately 200,000 t of straw are burned in on-farm boilers every year. Suitable systems are available from companies such as Farm

67 There are some problems with drying systems for the straw, control, and matching supply and demand. These are not insurmountable, and, with current developments in the hardware for drying, the use of straw as a boiler fuel could prove attractive in the future. A range of boiler sizes is available that can handle straw baled in a variety of manners, (large, round bales, small or large, square bales). Planning permission for such boilers is usually not required, and they can operate in smokeless zones. Typically, about 34 t of straw are required per year for a 50-kW boiler unit. An average-sized arable farm unit would be able to support such a boiler for heating a large farmhouse. If the heat produced from a straw burner is to be used for crop drying, for a typical 150-ha unit, 340 t/yr of straw are produced (see Section 4). This would give about 100 kw of thermal power as a continuous load, or 500 MWh of heat for crop drying, i.e., sufficient to dry ~5000 t of grain, (approximately 700 ha). In Example 1 (see box) approximately 15 to 20 t/yr of straw are used for crop-drying operations, with a peak thermal power of ~200 kw for short drying periods. The payback period for a straw burner will depend on circumstance, but may be from a few up to 15 years. In the examples given, typical payback periods of five to seven years were achieved. Example ha arable farm, with a five-bedroom farmhouse and a requirement for grain drying. 50 to 200-kW boiler with 9000-l accumulator. Fuelled by 200 to 250 large, round bales per year, (at 200kg straw per bale about 50 t/yr). 200-kW heat exchanger for grain drying operations. Capital cost: 17,000 for boiler, chimney, accumulator, heat exchanger, plumbing and electrics. Operating costs: ~ 450 per year plus labour (at 15 min/bale plus 1 h/month cleaning/ash removal). Benefits: ~ 3000/yr energy savings and no ploughing-in costs. Example 2 94-ha arable farm, with a three-bedroom farmhouse. 45-kW boiler fuelled by ~2000 small, square bales per year (three bales, two or three times a day, at ~15 kg per bale about 30 t/yr). Capital cost: 4,700 for boiler, chimney, heat exchanger, plumbing and electrics. Operating costs: ~ 150 per year plus labour (at 15 min/bale). Benefits: ~ 1200/year energy savings and no ploughing-in costs. The only realistic way to dispose of plastic waste is to send it elsewhere for recovery or disposal. Recycling schemes for farm films exist in various parts of the country (see Section 5). If available, take-back schemes run by suppliers will be the favoured option for plastics Pesticide washings Compatible spray tank washings can be added to the tank water for the next batch. Alternatively they can be disposed of by spraying out over the crop, subject to manufacturers recommendations Horticulture The two major waste areas in the horticultural industry are green-crop residue wastes and used rock wool growing medium. Farms near the straw-fired power station at Ely in Cambridgeshire should examine the possibility of selling straw there Plastics Traditionally farmers have used incineration for disposal of plastics, but on-farm incineration will no longer be practical when agricultural waste becomes classified as a controlled waste. Figure 40: Typical small-scale straw burner Green-crop residue waste Green-crop residue waste is the waste plant material from trimmings and spent plant material. This is easily composted or returned to fields to rot and recycle. Field spreading is the normal route for disposal. Glasshouse sites suffer a similar problem to that often encountered by pig units, i.e., in a built-up area with little space to accommodate or deal with the bulk wastes produced. 68

68 Rock wool Approximately 35,000 m 3 of rock wool growing medium are used annually in the UK. Almost all rock wool is removed from glasshouses in November, thus producing one large batch of waste per year. Disposal is usually to landfill. Some recycling is undertaken by reducing the rock wool to a granular form. This is then used in brick production to replace binding sand. Started as a trial in 2000, this recycling programme dealt with around 4550 m 3 and in 2001 was expected to increase to 12,500 m Impact of recycling on energy in horticulture Glasshouse heating dwarfs all other energy uses in horticulture. Any contribution recycling can make to reducing heating fuel requirements is bound to be significant. As the application of heat is at a high rate, with fossil-fuel-fired boilers feeding hot water to simple, piped systems, the use of incineration or AD to contribute to base load heating is probably the best example of recycling waste to produce energy. Generally, the mass of burnable waste produced will be small compared with the energy requirement of the glasshouse and a more logical waste source would be locally produced straw Exporting waste to centralised units The alternative to on-farm waste disposal for an individual farmer is a centralised treatment unit that will accept his waste products. Depending upon the nature of the waste, the farmer may be paid for the material or have to pay a gate fee, which may be from 15 to 40 per tonne depending upon the material and the means of disposal. DEFRA in the Waste Strategy 2000 proposes that local authorities and farmers operate in partnership with local businesses to create sufficient economies of scale, keeping transport costs to a minimum. Farmers seeking to diversify their operations may be able to host such schemes on their land. There are currently a number of centralised waste processing units that export electricity to the network. Figure 41 shows the locations of biomass, municipal and industrial waste, and sewage gas sites. Depending upon the nature of the waste, such sites may accept the farm waste and offer the farmer an acceptable deal. 8.3 Village schemes Energy from waste technologies is not likely to be cost effective on most standard-sized farm units in the UK due to the large capital outlay required. Government or EU funding may make such investment affordable, but such schemes are not widely available. If nearby farms can join together and install a large unit, which they all share, then the cost of energy from waste can be more affordable. AD in particular can use a variety of wastes from different farms to produce biogas. The same would be true of straw burners. The Portagester system is particularly suitable for a village-scale enterprise as it processes wastes from a variety of sources. Estimated treatment costs for the Portagester system are expected to be between 17 and 28 per tonne, compared to about 30 to 40 per tonne for landfill. Farmers who host such communal schemes on their land should generate income, and new jobs would be created for operating the equipment. The electricity produced could be sold to the National Grid. 8.4 Parish group or county schemes Cooperative ventures for exploiting farm wastes can be attractive, with their economies of scale, but there are likely to be considerable difficulties in initiating such schemes because of possible problems with transport, public perception, etc. County councils or groups of parish councils may wish to encourage the installation of centralised anaerobic digesters (CAD) units, or straw or poultry litter burners in order to provide a waste treatment route for producing income and providing employment. Currently, the only practical technologies for centralised energy from waste are CAD, and straw and poultry litter burning. Figure 41: Locations of centralised biomass, municipal and industrial waste, and sewage gas processing sites. 69

69 8.4.1 Centralised anaerobic digestion CAD facilities would be fed with farm waste, together with non-toxic, industrial organic wastes from the food production. CAD plants take waste from a number of farms, usually within a 10- to 30-km radius. A CAD plant with 1-MW electricity generation capacity (requiring a digester of 10,000-m 3 capacity is likely to cost between 3 and 6 million. 26 The electricity produced may be fed into the National Grid and, if possible, the heat produced fed into district heating networks or to local industrial users. The liquid-digestate fertiliser can be returned to the cooperative farms for land application, ensuring that the nutrients are reused and reducing inorganic fertiliser costs. Combined heat and power installations of from 0.1- to 1-MW electricity output are possible. A study for Shropshire County Council made recommendations on what could be achieved in the region under the present planning and legislative frameworks. 6 Within Shropshire and Herefordshire there are 0.45 million cattle, 0.2 million pigs and 9.8 million poultry producing about 8.4 million tonnes of waste. 2 The study showed that there is currently little utilisation of AD for the treatment and disposal of agricultural waste in the region. In Shropshire and Herefordshire, waste sources for AD are relatively unevenly dispersed, although five areas of resource concentration were identified. Analysis of the areas, based on pessimistic assumptions of waste availability (approximately 10%), suggests that each area could provide sufficient waste to run a electricity generator of 150 to 350 kw. The combined electricity generation capacity of the five areas is approximately 1 MW, compared to the total theoretical potential for electricity generation in the region of about 15 MW Poultry litter burners Centralised poultry litter burners are a relatively well-developed technology four power stations are currently in operation. Poultry litter is an excellent fuel for electricity generation, with nearly half the calorific value of coal. The heart of the poultry farming industry, Fife, has recently seen a dramatic rise in phosphate concentration in the watercourses, which is attributable in part to the widespread use of poultry litter as a fertiliser. A local biomass plant is using a fluidised-bed combustion system to convert the poultry litter into high-grade fertiliser, primarily for the horticultural market. The fertiliser is still rich in phosphates and potassium but it can be used in a more controlled manner. Three other poultry-litter-fired power stations are in operation. The world s first commercial power station to use poultry litter as fuel, at Eye in Suffolk, started operation in July 1992 and generates 12.7 MW. Eye is in the centre of one of the UK s largest poultry-producing areas. The plant consumes over 150,000 t of poultry litter per year. Glanford power station, in North Lincolnshire, started operation in November 1993, and generates 13.5 MW. North Lincolnshire South Humberside has a large poultry farming industry and the plant takes over 170,000 t/yr of poultry litter from surrounding farms. A third poultry-litter-fired power station at Thetford in Norfolk burns over 400,000 t of poultry litter per year, to produce 38.5 MW of electricity. The plant is Europe s largest producer of electricity from renewable sources. The total cost of the project was 70 million Straw-burning power stations The UK s first, and the world s largest, strawfired power station operates at Sutton, near Ely, Cambridgeshire. This 60-million, 36-MW facility generates GWh of electricity a year. The 200,000 t/year of straw for fuelling the facility is procured through long-term contracts with farmers and contractors within a 50-mile radius. Ten dedicated, covered heavy goods vehicles transport the straw to the power station, where it is stored in two enclosed barns with a total capacity of 2200 t (sufficient for over four days operation). The bales are shredded and then burned to raise superheated steam for electricity generation. It is planned to harness waste heat to supply local developments, (the site has planning permission for 20 acres of glasshouses). The combination of a lime scrubber and a baghouse filter system neutralises emissions. Ash is collected for use in agricultural fertiliser production. Most of the straw used so far has been from combinable crops, mainly cereals, but the plant is designed to take other biomass and up to 10% natural gas. 8.5 Regional strategy development Generalised regional maps (see Section 3) provide useful signposts for waste recycling developers. However, the final development of systems need closer geographical and infrastructure study. By extending the analysis used in Section 3 further, it is possible to drill down to useful local analysis. This is facilitated by DEFRA parish group agricultural production data. 68 The availability of up-to-date data at this level is limited. Some data date back to the late 1990s. However, older data are still relevant as the relative concentration of particular 70

70 agricultural business sectors tends to stay the same over many years, and sometimes over generations. The following section sets out a framework for the creation of strategies for UK counties. Firstly, the waste resource should be reviewed to determine whether a region exists that would provide a sufficiently high concentration of waste to make energy recovery possible. An indication of whether the county in question is likely to have sufficient agricultural waste can be obtained from Figures If it seems likely that a county might have sufficient organic waste then a more detailed breakdown, in terms of, for example, parish groups, should be performed. This analysis is useful for strategic planning and could be extended by local authorities for most regions Factors considered Such waste source analysis is not intended to identify specific sites, but to provide information that would help a potential developer to do so. In each case, the following should be examined: the potential resource availability and composition local authority structure plans with regard to transport issues, visual impacts and other planning permissions transport infrastructure the availability of suitable industrial land locations or areas with classification that would preclude the development of CAD on environmental or planning grounds the availability of a suitable electricity network the proximity and potential for the take up of low-grade heat the type of stakeholders and partners who might be involved Resource availability Suitable areas for energy recovery from organic waste will need to have a minimum electricity generation capacity of 1 MW at 100% waste resource availability. If an availability of only 10% is achieved, this would then lead to a potential of 100 kw of electricity, which is likely to be the smallest viable size of CAD scheme Transportation The AD good practice guidelines suggest that the viable transport distances for the various types of livestock waste are pigs 5 10 km dairy cattle km poultry up to 40 km. The guidelines suggest that a 1.5- to 2-MW e CAD plant will require around 20 large-vehicle movements per day, using either road tankers, covered trailers for dry poultry waste, or farm tractors and trailers for very short journeys. For a CAD scheme, tankers should be sufficiently large to collect from several farms before returning to the plant Location In principle, CAD plants should be located on or close to main roads, and preferably close to the intersection of two or more main roads able to support a concentration of heavy vehicle movements, rather than on secondary rural roads, which may become damaged and congested Planning permission To obtain planning permission, energy-fromwaste schemes will need to both comply with relevant planning policies and be acceptable in detailed, land-use planning terms Industrial development sites In some instances, particularly in very rural areas, even a modestly sized CAD plant would be a major new development. It is therefore imperative to select a location that is sympathetic to the local environment. Even in rural areas, it is often possible to find industrial estates with good road access, good infrastructure, and where disturbance and visual impact are less of a problem. Additionally, there may be the opportunity to sell heat to neighbouring businesses. In principle, these make ideal locations for CAD plants. The government s general policy, context and criteria for siting facilities are set out in the Department of the Environment, Transport and Regions Planning Policy Guidance Note East Yorkshire and North Lincolnshire an example of parish group analysis Figure 42 shows the anaerobic energy production potential of livestock waste in East Yorkshire and North Lincolnshire. This area Energy from farm slurry Less than 30TJ 30 50TJ 50 80TJ TJ TJ TJ Area A Figure 42: The anaerobic energy production potential of livestock waste in East Yorkshire and North Lincolnshire. 71

71 was chosen as it is recognised as being the home of a particularly large number of landlimited, intensive livestock production farms Resource availability From Figures 12 22, the available waste from the four major agricultural business categories in this region are cattle million t/yr pigs >2 million t/yr poultry 35, ,000 t/yr arable million t/yr. Figure 42 shows that one area (A) has the potential for TJ, (~4-5 MW continuous load) at 100% resource availability, or ~500 kw continuous load at 10% availability. Area A is about 20 km across, which matches well with the recommended distance for transport of waste in an area dominated by pig farms. Grouping together the six or seven regions with highest waste production, gives a region about 60 km long by 15 km wide. This would give rise to a possible 30-km journey, which is just about a feasible distance for an initial grouping. This grouping gives access to ~700 TJ, (~80 MW continuous load), at 100% resource availability, or 8 MW continuous load at 10% availability Resource summary Pig manure will form the primary feedstock for a CAD plant in this area. Because of the short viable transport distance for pig manure, a CAD plant will need to be positioned near to an area of major pig production. Pig waste is not generally seasonally variable. Cattle manure is the also plentiful, and availability is evenly distributed. However, cattle waste is seasonally variable, thus careful consideration must be given to its availability during the summer when the cows stay outside except for milking (see Figure 23). Although the availability of poultry litter in this area is relatively low, the long viable transport distance for poultry waste means that it would probably be practical for an energyfrom-waste scheme in the area Heat There are no direct data available for the heat demand or floor areas of domestic, commercial and industrial premises for the study areas assessed. Electricity consumption data are available by either parish ward or postcode areas for the domestic, commercial and industrial sectors, and an approximate assessment can be made by correlation with average consumption data for various premise types. It is likely that there might be a significant heat demand for domestic premises in the area, although the major heat demands may be in the commercial and industrial sectors. The region is not a nitrate-vulnerable zone and thus installations would not be suitable for funding by a DEFRA conservation grant, nor is the area one of those eligible for support under Objective 5a. Other funding may be available, however, and this should be fully investigated. The availability of industrial development sites would also need to be investigated, Costs The feasibility costs for developing a 500-kW plant area estimated to be in the region of 50,000. Capital costs, according to the AD good practice guide, will vary between 3000 and 7000 per kilowatt of electricity generating capacity. It is estimated that, assuming 10% availability of feedstock, the required capital investment would be between 2 to 3 million. Running costs, according to the guide, may be up to 1 million per year for a CAD project. Running costs will include staff costs, insurance, transport costs, annual fees for licences and pollution control measures, and maintenance and operating costs. The income from, based on ~3p/kWh and at 90% availability (at 8000 h), a 500-kW AD plant will be approximately 100,000 per year. Summary The most appropriate strategies for agricultural waste treatment at present are for dairy farms, the land spreading of organic waste (preferably after composting) for arable farms, straw burning on farm and in centralised units for poultry units (meat and egg production), litter burning in centralised units for all units, anaerobic digestion in regional units or on farm using a system such as the Portagester. If the high capital cost of anaerobic digestion units can be addressed by either expanding the market or providing subsidies, this technology could potentially be a major growth area. A good point of reference for those with futher interest in these forms of waste treatment strategies is British Biogen ( 72

72 09 Conclusions Last word This report shows that there really is no such thing as farm waste. Almost everything used and produced can be recycled in one form or another. The evidence will enable agriculture to literally clean up its act, but it will need help. As in many other areas, investment is necessary, but in some instances the benefits are immediate. Further benefits come later, but are guaranteed. This study shows that a large number of recycling and energy-recovery techniques are applicable to the various wastes generated by agriculture. While some techniques are improved versions of traditional waste management processes (such as the composting of organic waste), others are processes that have been transferred from other industries and adapted for use with farm waste. Some techniques show great promise, for example, anaerobic digestion (AD), but a concerted strategy is required for their introduction; this is discussed later in this section. It has been calculated that if all the livestock waste produced in the UK was treated using AD techniques, the energy produced would easily exceed the annual consumption of the entire agricultural industry. The principal waste management techniques applicable to the processing of farm waste are recycling composting plastic film reprocessing energy recovery poultry litter burning straw burning anaerobic digestion. 9.1 Recycling Composting is a growing industry in the UK, and is acquiring greater significance as a waste management option. It can be carried out using natural ventilation techniques (such as in midden stores), in windrows (with aeration achieved by turning), or using enhanced aerobic techniques (using forced aeration, stirring or tumbling to maintain optimum conditions within the system). To be commercially viable, some farm wastes (e.g., plastic films) need to be recycled at central reprocessing facilities, which may be dedicated to handling farm waste, or include farm waste with other industrial and municipal waste streams. Since 1998, farm film collection schemes have operated in a small number of areas (all supported by external funds, and all transporting plastic to BPI s plant in Scotland), but no nationally coordinated scheme exists. 9.2 Energy recovery Energy recovery is becoming increasingly important for agricultural wastes. Energy can be recovered directly through burning of agricultural waste products, or indirectly through the collection of by-products (e.g., methane from AD). Whatever the form of energy recovery used, systems that incorporate combined heat and power (CHP) schemes are recommended, as they maximise the value that can be extracted from a particular waste product. Poultry litter and straw burning technology are well advanced and a small number of units have recently started operation in the UK, mainly in the east. Widespread implementation of AD schemes in the UK, centralised or on farm scale, is constrained by poor financial returns. Experience in Denmark suggests that legislation would be required to restrict or prohibit the spreading of agricultural waste on land, and that funding would need to be available for environmental protection and/or sustainable energy projects. Potential developers should seek guidance on local, national and European sources of funding. European Regional Development funds may be available to some regions. 9.3 On-farm processing The most appropriate recycling and energyfrom-waste technologies for on-farm operation are land spreading, composting, straw burning and anaerobic digestion. Land spreading Land spreading is the most straight-forward and common method for reusing the organic wastes produced on a farm. When properly controlled, land spreading is an environmentally safe way to recover value from wastes allows farmers to reduce the amount of inorganic fertiliser applied to the soil leads to improvements in soil structure. However, if carried in an inappropriate manner, land spreading can lead to water pollution, soil contamination and deterioration of soil structure. 15,26 Composting Composting is generally carried out on-farm in midden stores, or using enhanced aerobic techniques to produce a saleable output. Straw burning The preferred use for surplus straw is to use it as a fuel in a suitable on-farm boiler, raising heat for hot water and buildings, and for grain drying and other operations. This cuts energy bills and avoiding ploughing-in costs. This technology is viable, even for standard-sized farming enterprises, if around 30 t of straw per year is available. 73