Agricultural Landbank, Organic Waste, A National Capacity Estimator (ALOWANCE)

Transcription

1 Agricultural Landbank, Organic Waste, A National Capacity Estimator (ALOWANCE) Steven Humphries a, Brian Chambers b, Fiona Nicholson b, Steven Anthony a and Chris Procter a a ADAS Wolverhampton, Woodthorne, Wergs Road. Wolverhampton, WV6 8TQ. Steven.Humphries@adas.co.uk b ADAS Gleadthorpe, Meden Vale, Mansfield. Nottinghamshire. NG20 9PF. Brian.Chambers@adas.co.uk Abstract Around 100 million tonnes (fresh weight) of organic materials (farm manures, biosolids, industrial wastes and municipal green-waste compost etc.) are currently applied annually to agricultural land in the UK. As a result of the need to meet UK recycling targets and the European Union Landfill Directive, a significant increase is anticipated in both the short- to medium-term in the amounts of industrial waste materials (e.g. paper waste, drink and food processing wastes etc.) and the production of composts from green waste and other organic materials (municipal solid waste-msw, food waste, animal by-products etc.) that would otherwise have gone to landfill. The availability of a suitable landbank, at both a national and local level, will be a key factor in deciding to what extent this is feasible and practical. The ALOWANCE (Agricultural Land and Organic Waste - A National Capacity Estimator) tool described here quantifies and locates, temporally and spatially, the national capacity of agricultural land to accept organic waste streams such as farm manures, biosolids (sewage sludge), industrial wastes and municipal composts. We describe the structure and functionality of this strategic management tool and its role in the assessment of the potential agricultural landbank available for recycling organic materials, which takes account of land use and physical constraints (e.g. crop type, soil type, location and topography) and competition between different organic materials. ALOWANCE provides a high level assessment of the impact that regulatory measures such as the Nitrate Vulnerable Zones (NVZs) and other land management agreements (e.g. Sites of Special Scientific Interest (SSSIs), Environmentally Sensitive Areas (ESAs), National Nature Reserves, organically managed farmland etc.) have on landbank availability, and offers a scenario testing capability so that the effects of policy and guidance changes on the landbank can be assessed. Key words: landbank, organic materials, organic manures, software, recycling 1 Introduction ALOWANCE provides a mechanism to assess the potential for the agricultural landbank in England and Wales to accept organic material from both farm and non-farm sources and is designed to calculate the available capacity or landbank remaining, after farm use, for non-farm derived organic materials, such as bio-solids (sewage sludge), municipal composts, industrial wastes (e.g. paper crumble, textile and tannery waste) and material generated through food processing, animal by-product treatment processes and other related activities. The 9.1 million hectares of agricultural land that could potentially be available in England and Wales for the spreading of organic materials are composed of approximately half arable and half lowland grassland, but clearly not all soils or land uses are suitable for the recycling of organic materials. Although organic materials provide a valuable source of nutrients for crop growth and organic matter that can maintain and

2 enhance soil physical conditions, which is a key component of the management of soils to sustain Good Agricultural and Environmental Condition (RPA & Defra, 2004) their application is restricted both in time and space by a number of physical and practical constraints and policy measures. These constraints, include: soil type and soil moisture deficit affecting trafficability, damage to soil structure and run-off risks, topography and proximity to water courses (surface and ground), heavy metal build-up, risks of pathogen transfer to food crops and water bodies, crop nutrient requirements, restrictions on total nitrogen loading rates within Nitrate Vulnerable Zones (NVZs) (MAFF, 2001), conditions of the EU Sewage Sludge Directive (SI, 1990) and land management agreements in Environmentally Sensitive Areas (ESAs), under Countryside Stewardship (CS) and as part of the rules for the management of organically farmed land. In the future there may be further restrictions to meet the requirements of the Water Framework Directive (WFD) (CEC, 2000). With around 90 million tonnes of farm manures (Williams et al., 2000), three to four million tonnes of biosolids and six to seven million tonnes of industrial wastes applied (on a fresh weight basis) annually to agricultural land in the UK (Table 1) there is clearly a need to understand the size and distribution of the available landbank, at both a national and local level. This paper describes the ALOWANCE software tool that has been designed to address this by calculating the national landbank for organic materials from farm and non farm sources based on N (nitrogen) production loading, the physical characteristics of the landscape and legislative limitations. ALOWANCE is a strategic management tool that has an embedded methodology for calculating 1) the landbank capacity 2) existing farm manure production 3) the proportion of the landbank already taken by farm manures and 4) how much will remain for non-farm derived organic materials. Its purpose is to provide an overview to guide policy development by identifying areas in England and Wales where there is a potential shortage or surplus of available land for recycling organic materials. ALOWANCE provides scenario testing capabilities enabling calculation of future landbank capacity in light of changes in land use and legislation, for example, as a result of CAP reform on livestock numbers or changes in NVZ regulations. The tool allows new waste streams to be added and the landbank capacity to be calculated interactively. 2 Approach 2.1 Algorithm and data The ALOWANCE system contains a 10km 2 spatial representation of the Agricultural Census data in England and Wales from June 2000 (i.e. livestock numbers, types and crop areas), which ADAS has already compiled as part of nutrient pollution policy support work for Defra within the MAGPIE database and model framework (Lord and Anthony, 2000). This grid forms the basis of data management and modelling within ALOWANCE. The June 2000 census data was selected as the benchmark year as it represented the most up to date dataset that was available within the MAGPIE database that has been fully validated at a 10km 2 grid square level, so that we could confidently quantify and locate the agricultural land area potentially available for the application of organic materials. We also included 2004 livestock numbers to provide a more up to date assessment of present day nitrogen loadings from farm manures, after the foot and mouth perturbations in livestock numbers between 2001 and These livestock numbers are combined with N production (expressed in terms of kg N animal -1 year -1 ) for each animal type to calculate a total N loading from farm based manures at a 10km 2 grid cell resolution that covers England and Wales. This N loading is subdivided into excretal N deposited directly to the field and manure N handled as FYM (farm yard manure), slurry, poultry litter or poultry manure, according to typical farm practice, to accommodate the different legislative and practical constraints on spreading of these materials. All poultry litter N production within 80 km of a power station was assumed to be burned for energy recovery and this N removed from the poultry litter stream. We have included within ALOWANCE data layers for the location of sewage sludge treatment works and sludge production centres, composting sites, paper crumble sites and food production centres and this information is combined with typical production quantities and N content information (Table 2) for these point sources to calculate likely N loadings for each 10km 2 grid cell. The position, size and N content of point source N can be edited within the ALOWANCE system to account for improved knowledge or changes in industry practice. All point sources have an associated transport distance for the organic material produced (which is largely determined by economics). This distance represents the average

3 radial distance from production source to the point of recycling, based on industry information. Point source N production is assumed to be evenly distributed to neighbouring cells within the specified transport distance of a point source. The point source organic stream N production is added to farm N loading to calculate the total N loading for each 10km 2 cell. The baseline landbank potential, in the absence of N loadings, was then calculated by considering the proportion of each 10km 2 grid cell that was agricultural land and within this how much was constrained by legislative, physical or health considerations, with different constraints considered for slurry, FYM, poultry litter/manure and non farm organic materials (Table 3). The spatial location of key legislative areas that govern landscape N capacity - NVZs, SSSIs, National Parks, land likely to be under ESA, CS and organic farming agreements, urban areas, rivers, ditches and controlled waters (including groundwater protection zones and boreholes) have all been mapped, and included within ALOWANCE, and can be queried through the ALOWANCE interface. Nationally c. 0.1% of agricultural land is within 50m of a borehole, c. 1.3% is in a source protection zone 1, c. 1.8% in a SSSI, c. 6.7% in ESA with 3.4% under agreement. Steeply sloping land (>16º) occupies c. 0.5%, organically farmed land 1.9% and National Nature Reserves (NNR) a further 0.1% with NVZ regulations currently applying to c. 55% in England and 3% Wales. We used the constraint information outlined in Table 3 to create a dataset in which land area designations with the same constraints, or rules, applied were combined to produce a more manageable system with fewer categories. The resulting data layer, included in ALOWANCE, consists of five functional area designations 1) NVZ only, 2 ESA, NNR & SSSI only, 3) NVZ and ESA, 4) SPZ or within 10m of a water course and 5) baseline restrictions only. We assume that each of these areas may contain one or more of these landuses - arable, grassland, pea/beans, ready to eat or set-aside land which were chosen for their legislative importance in determining the N application rate (Table 4). The proportion of each designated area occupied by each landuse was calculated and stored within ALOWANCE with the theoretical maximum N loading for a given combination being a function of the N stream type (FYM, slurry etc.), the designated area type (NVZ etc.) and land use (arable etc.). ALOWANCE, by default, presents grid cell N capacity as a single value (as kg ha -1 or ha equivalents for each land use) but can be queried to retrieve the constituent area and N stream components. To represent physical and soil constraints on the landbank capacity we included spatial datasets for soil ph, heavy metal content and topography (slope). ALOWANCE assumes that all land with a slope of >16º is only available for animal grazing and resulting excreta N production no FYM, slurry or other organic material can be allocated to this land due to physical limitations in spreading. Data on the maximum permissible concentrations of heavy metals in soils (Table 5) has been included in ALOWANCE and are used to further constrain the land available for the allocation of non-farm organic materials with soils that have heavy metal contents in excess of legislative maximums assumed to be unavailable for recycling of this material. ALOWANCE uses a rules based algorithm for deciding how and where N production should be allocated to the available landbank capacity. In these rules we first consider excretal N, as it is not handled and therefore cannot be moved from one area to another. A record is kept of any excretal N which cannot be assigned within a given grid cell. Next the slurry N stream is examined, if this can be allocated to the NVZ designated area then it is and a record of any surplus capacity noted. If there is too much slurry N for the NVZ area alone the baseline restricted area is tried next. If this fails then a record is kept of the amount of slurry that cannot be allocated within the confines of the grid cell. This represents the slurry that must be transported out of the grid cell to retain compliance. Next FYM is examined, if this can be allocated to NVZ & ESA areas then it is and a record of any surplus capacity recorded. If there is too much FYM for the NVZ & ESA area alone then the ESSA_NNR_SSSI area is used next. If this fails to have enough capacity then the remaining material is allocated to NVZ area and if this fails to have enough capacity finally to the baseline restricted areas. If this fails the remaining FYM is assumed to be transported out of the grid cell to retain compliance. The poultry litter and manure stream is allocated first to the NVZ land and then the baseline restricted land. Non farm point source N is allocated first to NVZ land and then to no restriction land. Any surplus capacity for any of the N streams in any of the designated areas is recorded and forms the basis for the landbank capacity result. Grid cells with a surplus in any of the N streams are assumed to transport this material to neighbouring cells and there is an option in ALOWANCE to specify the average transport distance for each N stream in a similar way to non farm organic materials production discussed previously.

4 2.2 Software The ALOWANCE tool has been developed as a stand-alone software programme, incorporating a map interface (GIS) to visualise and query the data. The software uses Microsoft Visual Basic 6, using Microsoft ACCESS and ESRI MapObjects for data storage and mapping, respectively (Figure 1). The use of Microsoft ACCESS permits rapid data update and ease of sharing of baseline data with other projects. Figure 1 ALOWANCE application with 1) menu controls 2) toolbar for access to standard GIS map controls such as zoom, pan, show full map extent, data import/export, spatial & optimisation analysis and help system. 3) Tab access to key landbank parameters, livestock numbers, N production standards from livestock, point source N production and soil heavy metals values. 4) Editable worksheet for livestock N production standards showing census categories and N production broken down into slurry, FYM, poultry manure and litter. 5) Distance/value dialog showing relationship in this case between capacity and radial distance from a selected point on the map. 6) Spatial analysis and optimisation dialog showing the grid cells in a selectable area that have the minimum and maximum capacities allowing for maximum transport distance. ALOWANCE makes all of its spatial data available as a series of map layers that can be selectively viewed and queried. These layers include all of the land area/use information discussed previously, the distribution of livestock and point sources and all landbank capacity results all of which can be viewed directly in the map viewer (Figure 1(7)). ALOWANCE contains a distance/value dialog (Figure 1(5)) that allows the integrated total value of a requested parameter to be summed for all cells within a series of radial distances from a point that can be selected onscreen and for this to be graphed automatically. If the total N capacity after production layer is chosen the graph will therefore show the total capacity within a range of distances from a selected point, likewise if the animal numbers layer is chosen the result could be a graph of total dairy cows or other livestock by distance. ALOWANCE has scenario testing capabilities enabling predictions of the future agricultural landbank in

5 light of potential changes in land use, for example, as a result of CAP reform influencing livestock numbers (Figure 1, (4-livestock tab)), changes in regulations to meet Water Framework Directive needs etc. The N content data entry dialog Figure 1(4 N tab) allows us to vary the N content of organic materials and through this to examine the impact of changes in livestock diet and farm practice on farm produce N loadings. The point source editing dialog Figure 1(4 N point sources) allows us to add/edit and remove point sources and to simulate the effect of increasing amounts of organic materials being diverted away from landfill and the effect of this on the resulting landbank. ALOWANCE has a spatial analysis capability (Figure 2) that allows simple statistical summaries and more powerful optimisation analysis of ALOWANCE data. Areas may be selected manually using onscreen toolbar controls or by loading an external ESRI shapefile to specify the boundary to be selected. Figure 2 Example spatial analysis dialog with landbank N capacity after production layer selection shown. 1) Type of spatial analysis simple, find cells with min/max values in selected area, find cells with min/max values in selected area allowing for transport and transport with costs 2) data layer to query 3) field within layer to analyse 4) maximum transport distance from points that values should be summed over 5) feature selection mechanism 6) selected features/grid cells 7) results table 8) controls to export results to Excel or to have grid cells with min/max values flash in the main map panel for easy identification. 3 Results and Discussion The distance/value function (Figure 1 (5)) in ALOWANCE provides a valuable tool for assessing at a glance both capacity and demand information and with careful selection of the appropriate data layer and data item allows the user to ask and answer questions such as if I were to build an energy recovery facility at this point how much poultry litter is currently produced within 50km of my position? Or what is the landbank available for recycling of paper crumble within 30km of a selected position? The spatial analysis dialog allows the grid cells with the minimum and maximum integrated total value assuming a user specified maximum transport distance to be calculated for a requested data parameter. This makes it possible to answer questions such as - which location has the most dairy production (maximum) available for bio-digestion assuming a maximum transport distance of 50km? Or what area has the lowest (minimum) average soil heavy metals contents when combined with neighbouring cells within a specified distance.

6 Preliminary results from ALOWANCE indicate that the agricultural landbank theoretically available for recycling organic materials, in England and Wales, is c. 9.1 million hectares (Figure 3a). Taking into account land excluded by virtue of topography (steep slopes), proximity to water courses, springs and boreholes, outdoor pigs, organic farms and ready to eat crops reduces this to c. 8.6 million hectares (Figure 3b). The remaining headroom for other organic materials after farm manures have been applied is c. 6.2 million hectares (Figure 3c) Figure 3 Preliminary indication of a) theoretical maximum landbank b) landbank after exclusions for topography/proximity to water courses, outdoor pigs, organic farms and ready to eat crops c) landbank after exclusions and application of farm manures. In further development of ALOWANCE, we hope to incorporate the locations and availability of the restored/reclaimed landbank for recycling organic material, and to enhance the spatial coverage of organic material loadings from point sources (e.g. anaerobic biodigesters, biocomposts etc.) Acknowledgement Funding for the development of the ALOWANCE tool from the Department of the Environment, Food and Rural Affairs (Defra), is gratefully acknowledged. References CEC: Council of the European Communities (2000) Council Directive concerning integrated river management for Europe. 2000/60/EC. Official Journal of the European Communities No L327 Lord, E.I and Anthony, S.G. (2000). MAGPIE: A modelling framework for evaluating nitrate losses at national and catchment scales. Soil Use and Management, 16, MAFF (2001) Guidelines for Farmers in NVZs (PB5505), Defra Publications, Admail 6000, London SW1A 2XX. RPA and Defra (2004) Single Payment Scheme Cross Compliance Guidance for Soil Management (PB 10222B), Defra Publications, Admail 6000, London SW1A 2XX SI (1990) United Kingdom Statutory Instrument No 880 The Sludge (Use in Agriculture) (Amendment) Regulations HMSO, London. Williams, J.R., Chambers, B.J., Smith, K.A. and Ellis, S. (2000). Farm manure land application strategies to conserve nitrogen within farming systems. In: Agriculture and Waste Management for a Sustainable Future. (Eds. T. Petchey., B D Arcy and A Frost), The Scottish Agricultural College, pp

7 Appendix Table 1. Estimated quantities of organic materials recycled to land in the UK. Manure type Fresh weight Dry solids (million tonnes) * Livestock manures Biosolids Green waste compost Paper crumble Industrial wastes Total Table 2. Typical N contents of point source organic materials used in ALOWANCE. Point Source description N Content * Dry Matter (%) kg t -1 Green waste compost 7 65 Paper crumble (biologically treated) Paper crumble (physical/chemical treated) 2 41 Biosolids 37 0

8 Table 3. Summary of restrictions to landbank available for spreading organic materials Factor or Designation Source of Restriction ALOWANCE Restrictions ESAs Environmentally Sensitive FYM only Areas (SI, 1993) SSSIs SSSI designation FYM only National Nature FYM only Reserves Organically managed farmland UKROFS Standards (2003) Maximum N loading rate (handled plus excreta deposited) 170 kg N ha -1 yr -1 (both inside and Topography Watercourses Soil ph Soil heavy metal content Ready to eat crops (RTE) NVZs Practical limitations of spreading The Water Code (MAFF, 1998). EA Groundwater Source Protection Zones NVZ legislation (Defra, 2002) Sludge Regulations (SI, 1990) and COP (DoE, 1996) Sludge Regulations (SI, 1990) and COP (DoE, 1996) Safe Sludge Matrix ( FSA Guidelines for Farmers - draft (FSA, 2002) NVZ legislation outside NVZs). No spreading if slope >16. This exclusion only applied to handled manures - excreta deposited during grazing is not affected. Slope from Ordnance Survey. No spreading within 10m of any watercourse (including. Ditches). Area/length of ditches calculated pro-rata on field size. No spreading within 50m radius of a spring, well or borehole used for human consumption or farm dairies. Exclusion only applied to handled manures - excreta deposited during grazing is not affected. Biosolids (and composts) not applied if soil ph<5 Biosolids (and composts) only applied if soil heavy metal concentrations are below the permitted maximum Conventionally treated biosolids cannot be applied within 30 months of harvest of ready to eat (RTE) crops and enhanced treated within 10 months of harvest. Treated (ie. batch stored or composted) solid farm manures can be applied before RTE crops, but not fresh solid manures or slurries within 12 months of harvesting and 6 months before drilling planting a RTE crop. ALOWANCE currently assumes that RTE areas have no capacity to receive organic materials. No organic material in front of legumes. ALOWANCE removes the area of peas/beans from the landbank area for all manures. In an NVZ, the maximum N loading rates (i.e. manure and excretal N) are 170 kg ha -1 for arable land and 250 kg ha -1 for grassland.

9 Table 4 Maximum N loadings by land type (from current NVZ legislation). * represents the baseline restrictions for maximum N loadings outside of NVZ/ESA/SSSI/NNR. Description Kg N ha -1 Grass inside an NVZ 250 * Grass outside an NVZ (handled manure only) 250 Organically farmed 170 * Arable outside an NVZ (handled manure only) 250 Arable inside an NVZ 170 Ready to eat 0 Table 5 Maximum permissible concentrations of potentially toxic elements in soils after application of sewage sludge (DoE, 1996). PTE Maximum permissible concentration in soil (mg kg -1 dry soil) Soil ph value >7.0 Zn Cu Ni For ph 5.0 and above Cd 3 Pb 300 Hg 1 Cr 400