Use of Biochar for enhancing soil quality in mountain agricultural lands of Nepal

Transcription

1 Use of Biochar for enhancing soil quality in mountain agricultural lands of Nepal Abstract Ngamindra Dahal and Roshan Man Bajracharya, Contact: Kathmandu University, Dhulikhel Nepal Biochar is a charcoal like residual mass usually prepared by pyrolising biomass in controlled temperature and minimum oxygen conditions. Biochar is often prepared from leafy biomass and agricultural wastes. It has recently regarded by the scientific community as a useful agent to enhance soil quality as it brings about desirable changes in chemical and physical properties for soil microorganisms and crops. Studies undertaken elsewhere in the world have recognized effectiveness of biochar in improving soil quality, thus, saving costs and time of farmers though there are hardly any studies to prove such effectiveness in Nepal. Biochar may be produced by using improved cook stove designed for dual purpose of cooking and producing biochar, and through industrial-scale retort process. In Nepal, high mountain farmers have an indigenous method of preparing and applying biochar in their agriculture lands mostly for preparing millet nurseries and potatoes. Availability of sufficient amount of feedstock for biochar production is a critical issue as biomass is already used for livestock feeding, preparing compost and energy purpose in most of rural households. A recent feedstock survey conducted among farmer households in organic coffee plantation areas of Thuladurlung of Lalitpur, Talamarang of Sindhupalchok and Panchkhal of Kavre districts of Nepal revealed that local farmers always have some quantity of 'unused' or 'underutilized' or 'waste' biomass at each household and community. However, none of the areas have large scale waste biomass available as feedstock for preparing biochar. Nevertheless, there is a good prospect of preparing and using biochar in a small quantities round the year without adding any significant costs and time for farmers other than their 'business as usual' level. Taking examples from Nepal and elsewhere in the worlds, this paper throws light on prospects of promoting biochar among mountain farmers using the 'additional' stock of biomass; and, addressing concerns associated with soil quality degradation and climate change. Key words: Climate change, mountain farmer, biomass feedstock, biochar stove, sustainability 1

2 Introduction In the past several decades, Nepal saw majority of farmers intensifying cropping systems with 3 or more crops per year with increased uses of chemical fertilizers (Dahal and Bajracharya, 2011). Intensified vegetable cropping systems with up to 4 crops grown in the annual cropping cycle became commonplace, especially in peri- and semi-urban areas close to highways and urban markets. Kaini (2004) observed that the production of major cereal crops has been virtually stagnant over the past 15 to 20 years and the national average yields of maize, wheat and rice are well below the attainable and experimental yields; and, the productivity of these crops are well below those reported in neighbouring countries. The main reasons for low yields are believed to be the lack of replenishment of soil organic matter and soil nutrients, and inadequate or inappropriate use of fertilizers (Bajracharya 2002, Regmi et al. 2005, Karki 2006). Over the past few decades, there has been a notable shift in cropping patterns due to increasing food and cash-crop demands along with availability of agro-chemicals though supplies are often interrupted. This has led to diminishing productivity and fertility of arable lands (Bajracharya 2002). Climate change has aggravated the situation as rainfalls are getting more erratic, and, temperatures are rising in Nepal at one of the highest rates in the world (MoE, 2010) farmers are under stresses of multiple challenges including soil fertility and soil moisture deficiency leading to steady decline of productivity. Several types of soil additives and fertilizers are used as a response to improve or maintain or improve structure and functions of soil. One that has re-emerged in recent years is biochar, a solid material obtained from the thermochemical conversion of biomass in an oxygen-limited environment which creates a fine-grained, highly porous charcoal. Interest in biochar has increased as farmers are looking for sustainable ways to improve soils and decrease their use of chemical fertilizers. Thus, biochar has become an emerging technique used to address growing concerns on declining soil fertility. Traditional biochar is widely used as a key additive for soil amendment in many parts of Asia particularly Japan, China and India. In recent decades, it is getting popular among commercial farmers in Australia, Europe and US. The thermal conversion of biomass, under the complete or partial exclusion of oxygen, results in the production of biochar and bio-energy or other bio-products such as syngases and oils. Biochar production processes can utilize any organic materials including a wide range of biomass including most urban, agricultural or forestry biomass residues, for instances coffee pulps and husks, wood dust, forest litters, weeds, rice husks, tree bark, paper mill sludge, and recycled organics. Fig 1: Freshly prepared biochar using a specially designed household cooking stove As a soil amendment, biochar helps to improve the Earth s soil resource by increasing crop yields and productivity, by reducing soil acidity, and by reducing the need for some chemical and fertilizer inputs (Glaser et al 2002 and Lehmann and Rondon 2006). According to Lehmann et al (2003), and Steiner et al (undated), water quality is 2

3 improved by the use of biochar as a soil amendment, because biochar aids in soil retention of nutrients and agrochemicals for plant and crop utilization(lehmann, et al., 2003; and, Steiner, et al. undated), reducing leaching and run-off to ground and surface waters. Although, biochar particles resemble with charcoal, the process of preparing this differs from the formers; and, widely used as a useful ingredient with beneficial effect on soil fertility. According to the whitepaper on biochar by the International Biochar Initiative (IBI) entitled 'Biochar: A Soil Amendment that Combats Global Warming and Improves Agricultural Sustainability and Environmental Impacts', biochar systems can reverse soil degradation and create sustainable food and fuel production in areas with severely depleted soils, scarce organic resources, and inadequate water and chemical fertilizer supplies. Low-cost, small-scale biochar production units can produce biochar to build garden, agricultural, and forest productivity, and bioenergy for eating, cooking, drying and grinding grain, producing electricity and thermal energy, for instance. In Nepal, high mountain farmers have a tradition of on-farm biochar making practices for specific crops particularly of millet nursery, potato and seasonal vegetables (Josheph et al 2012). There is a clear lacking of scientific studies on practices of biochar productions and applications in agricultural systems in Nepal. In recent years, Nepal based various agencies including Asian Development Bank, Helvetas and Multi Stakeholder Forestry Program have launched pilot initiatives of biochar promotion. This paper attempts to analyse issues associated with prospects, challenges and implications of biochar promotion in Nepal's agricultural sector. Methods and materials This study is primarily based on review of a range of published literatures on biochar, and, observational visits of a few places in Dolakha District of Nepal where farmers traditionally use biochar for their valuable crops. Literatures available online such as journal articles, book chapters and newsletters mainly of the International Biochar Initiative (IBI) were consulted. Conversations with officials of Kathmandu based development agencies that are supporting farmers to prepare and apply biochar to their fields provided useful insights on prospects of biochar applications in Nepal. A set of general Special interests were Mountain farming practices and biochar Being an agriculture-dominated country, a significant number of mountain farmers in Nepal have used farm-yard manure (FYM) as the major source of plant nutrients based on traditional knowledge and techniques followed for generations. In the past, this contributed to the maintenance of a balanced input-output ratio of SOC. In Nepal, the majority of farmers (>85%) apply farmyard manure and/or compost in their fields (Maskey et al. 2002). However, a decline in the soil organic carbon pools is observed due to changes in land use, intensive cultivation, and poor organic manure management (Gami et al. 2001; Upadhyay et al. 2005). Traditionally, farmers rely upon compost or FYM, made of forest litter, crop residues as well as animal manure to replenish croplands, and followed a less intensive and more sustainable fallow farming system, producing only two crops in an annual cropping cycle. In recent years however, the majority of farmers have switched to conventional usage of chemical fertilizers and intensified cropping systems with 3 or more crops per year (Dahal and Bajracharya, 2011). 3

4 Intensified vegetable cropping systems with up to 4 crops grown in the annual cropping cycle have become commonplace, especially in peri- and semi-urban areas close to highways and urban markets. The production of major cereal crops has been virtually stagnant over the past 15 to 20 years and the national average yields of maize, wheat and rice are well below the attainable and experimental yields; and, the productivity of these crops are well below those reported in neighbouring countries (Kaini 2004). The main reasons for low yields are believed to be the lack of replenishment of soil organic matter and soil nutrients, and inadequate or inappropriate use of fertilizers (Bajracharya 2002, Regmi et al. 2005, Karki 2006). Over the past few decades, there has been a notable shift in cropping patterns due to increasing food and cash-crop demands along with availability of agro-chemicals though supplies are often interrupted. This has led to diminishing productivity and fertility of arable lands (Bajracharya 2002). In recent years biochar is being used increasingly as a remedy to address concern of declining soil fertility by enhancing moisture retention and manure absorption capacity of soil. Biochar is increasingly used as an agent for amendment of agricultural soils, and, produced from any organic materials through thermo-chemical conversion of biomass under controlled temperature and minimum oxygen. This helps making the biomass material free from volatile substances to avoid blocking of the cavities as these are important for storing moistures, microbes, fungi and mycorrhizae. The key function of the biochar in the soil is to help stabilize carbon, immobilize nitrogen, and, improve soil structure and texture (Sohi 2012). Biochar production and utilization systems differ from most biomass energy systems because the technology is carbonnegative as it removes net carbon dioxide from the atmosphere and stores it in stable soil carbon sinks" Fig.: 2 Testing of a household cooking stove used for biochar making. (Lehmann et al 2006). Other biomass energy systems are at best carbon-neutral, resulting in no net changes to atmospheric carbon dioxide. When biomass is pyrolysed, in the process it releases syngases and bio oils, finally retains biochar as the end product, having no or insignificant amount of flammable as well as degradable organic matter. Studies have shown that applications of biochar have significant improvement in the overall soil environment, crop yields, reducing leaches of organic and inorganic fertilizers. Consequently, biochar leads to increase global food production while enhancing soil health in a sustainable manner. 4

5 Effectiveness of biochar in soil amendment Biochar is added to soils to improve soil functions and reduce emissions from biomass that would otherwise naturally degrade to greenhouse gases. In the soil, biochar contributes to enhance habitat for soil organisms, but is not itself consumed by them to a great extent, and most of the applied biochar can remain in the soil for several hundreds to thousands of years (Lehmann et al, 2006, Pessenda et al 2001, Schmidt et al 2002) such as in the Terra Preta soils in the Amazon River Valley. The biochar does not disturb the carbon-nitrogen balance in the long-term, but holds and makes water and nutrients available to plants. When used as a soil amendment along with organic and inorganic fertilizers, biochar significantly improves soil tilth, productivity, and nutrient retention and availability to plants (Glaser et al 2002). Some mountain communities of Nepal have found using biochar prepared through their traditional technique in the field specifically for millet, potatoes and other vegetables and crops (Stephen, at al 2012). Locally, they called this practice 'bukma' or 'jhyas polne'. Efficiency of biochar production Biochar can be produced by pyrolysis or gasification systems. Pyrolysis systems produce biochar largely in the absence or minimum flow of oxygen and most often with an external heat source. Depending on the speed, the pyrolysing process may be categorised into two: fast pyrolysis and slow pyrolysis systems. Gasification systems produce smaller quantities of biochar in a directly-heated reaction vessel with air introduced. Also, the gasification and pyrolysis production systems can be developed as mobile or stationary units. Recently, Kathmandu University in partnership of Foundation of Sustainable Technology and HELVETAS Intercooperation has developed small scale gasification and pyrolysis systems that can be used on farm or by small industries are commercially available with biomass inputs of 10 kg/hr to 200 kg/hr. The bioenergy produced from these systems can be used for cooking or heating purposes. At the community and commercial levels, pyrolysis and gasification units can be operated by co-operatives or larger industries to produce large quantity of biochar for selling in the market. Thus, there are multiple ways of producing biochar depending upon needs and scales of production (e.g. household, community or industrial) or traditional knowledge and practices (e.g. high mountain farmers of Nepal). Table 1: Various types of household stove tested for dual purpose of cooking cum biochar production SN Type of stove Burner size Materials Capacity 1 Rocket stove 110 mm CRC sheet 2 kgs 2 Biochar stove 90 mm CRC sheet 2.5 kgs 3 Biochar stove 110 mm CRC sheet 2.5 kgs 4 Rocket model biochar stove 110 mm CRC sheet 2 kgs 5 Biochar stove 110 mm CRC sheet 2 kgs 6 Biochar stove 90 mm Stainless steel 2 kgs 5

6 7 100 litter biochar drum 8 Heavy biochar drum 9 Small prototype biochar stove 10 Handy size prototype stove Sources of feedstock for making biochar 110 mm Petrol drum 15 kgs 110/140 Stainless steel 10 mm 45 mm Aluminum 0.3 kg 75 mm Stainless steel 0.7 kg Source: Foundation of Sustainable Technologies (FoST) There are a range of issues related to biochar productions which include sources of feedstock, its accessibility and implications to existing uses, types of stove and use of additional fuel, scales of production and quality control. In order to avoid competitions over existing uses of feedstock, it is utmost important to identify underutilized and additional sources of feedstock for biochar productions. For example, a rapid household survey among coffee farmers in selected pockets of in Talamarang VDC of Sindhupalchok, Panchkhal VDC of Kavrepalanchok, and Chandanpur and Thula Durlung VDCs of Lalitpur between December 2012 and March 2013 revealed that they have variety of agricultural wastes at different seasons which they can readily use as biochar feedstock at household levels. They have not been able to utilize the coffee-pulps and husks. In this case, coffee pulps and husks found to be useful feedstock for biochar production. However, the coffee wastes alone are not enough to produce biochar sufficient to their farmlands. In some pockets, farmers found new reason to harvest underutilized forest litters which they have not collected in recent years due to labour shortage. Likewise, a major issue of applications is the limited evidence based information about the quantity and types of biochar to be used for healing specific soil types in different agricultural environment. The major feedstock available for biochar production includes: coffee pulps and husks, forest litters, agricultural residues such as weeds, invasive species, crop residues. industrial wastes such as paper mill and residues from sugar mills, and waste wood products. Particularly they mention of coffee pulps and husks during coffee harvesting and processing season between January and March each year. They also reported that they can use the forest litters, which is sufficiently available at their community forests during dry months. Considerations for Further Studies With rising in interest on biochar, there are a range of research questions coming up. For example how much and what types of biochar should be used in soils? How should we apply biochar more effectively? What types of biochar fit specific types of soils? How do we know if a particular biochar actually helps a particular soil retain nutrients and water? How do we know what is in the biochar? Depending on the interest and purpose of the product, answers can vary as biochar may be used as a product or as an ingredient within a blended product. In addition to this, biochar can be used for 6

7 the dual purposes of climate change adaptation and mitigation alike. In Nepali context, the following points are emerged as significant issues: Making an efficient biochar stove: Designing appropriate stove for meeting various cooking or heating needs of households is crucial to save energy. Preliminary study indicates Majority farmers find biochar stove more appropriate to prepare animal feeds or heating water during winter. They are hesitant using it for cooking regular food. Coffee processing households prefer a dedicated stove exclusively for preparing biochar out of coffee pulps and husks. Quality assurance: This is particularly important when people start preparing biochar without proper consideration of controlling temperatures and air. Also, there are issues of emitting hazardous gases and heavy metals. Linking feedstock type with soil conditions: Though biochar is considered generally good for the health of any types of soil, it is more beneficial if biochar is prepared with added ingredients for supplying deficient elements to the soil types. Sustainability of biomass resource for biochar: It is not recommended to produce biochar unless there is adequate biomass available. Sustainable use of biomass is critically important for preparing biochar. CONCLUSION Biochar is a re-emerging soil additive for the amendment of agriculture soil with marvelous benefits to address detrimental impacts of climate change on soil health. Biochar is not a substitute of manure but a catalyzing agent for enhancing soil health including fertility. This could be a useful for both rural and urban areas in terms of sustainable productivity of land to respond concerns of food security, environment conservation and employment opportunities among others. Any organic wastes can be the feedstock for making biochar. Mountain farmers of Nepal traditionally use underutilized biomass collected from the farmlands and nearby forest areas for preparing biochar in the farmlands, which they called 'bukma' system. Recent studies have indicated that the key benefits of biochar include reduced soil bulk density, increased nutrient and water retention, and decreased nutrient leaching. The most common source of biochar feedstock is the agricultural wastes and agro-forest litters. These include weeds, degraded shrubs and forest litters among others. In coffee pocket areas, coffee pulps and husks are identified as an attractive feedstock for biochar feedstock, which does not interfere with existing uses of biomass such as fodder and fuel. Farmers have reported that they can manage adequate biomass from waste agricultural sources and forest litters when they are satisfied with the beneficial effects of biochar. Efficient and economic gassifires are under evolution stages as they have to meet dual purposes of pyrolysing biomass to produce biochar while ensuring the optimum use of the heat produced there. These technologies include low-cost household stove with dual purposes of cooking and heating needs as well as producing biochar, medium scale stand- 7

8 alone type retort to produce biochar from the point sources of feedstock such as coffee pulping and husking centres, and, traditional ways of biochar making in the agricultural fields by pyrolysing locally collected biomass stock under a cover of soil. Acknowledgement The authors acknowledge the support provided by Juerg Merz of HELVETAS Intercooperation and Sanu Kaji Shrestha of Foundation of Sustainable Technologies for undertaking field studies and testing of biochar producing stoves. They also would like to thank Ms Hausala Shakya from KU for her useful support in designing the prototype of biochar stove. References Bajracharya, R.M. (2002). Fertility and Productivity Parameters for Soil from Five Mid-hill Districts of Central Nepal. Proceedings of International Seminar on Mountains (pp ). Kathmandu: Royal Nepal Academy of Science and Technology. Dahal, N. and Bajracharya, RM (2011): Prospects of soil organic sequestration: Implications for Nepal s Mountain Agriculture. Journal of Forest and Livelihood 9(1) February, Gami, S; Ladha, J; Pathak, H; Shah, M; Pasuquin, E; Pandey, S; Hobbs, P; Joshy, D; Mishra, R (2001) Long-term changes in yield and soil fertility in a twenty-year rice, wheat experiment in Nepal. Biology and Fertility of Soils 34: Glaser, B., Lehmann, J. and Zech, W., 2002, Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal --- a review, Biology and Fertility of Soils, 35: Glaser, B., Lehmann, J. and Zech, W., 2002, Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal --- a review, Biology and Fertility of Soils, 35: IBI [International Biochar Initiative] Biochar. Kaini BR (2004) IncreasingCrops Production in Nepal. In: Sherchan DP, Adhikari K, Batsa BK and Sharma D (eds.) Procs 24th National Summer Crops Research Workshop on Maize Research and Production in Nepal, June 28 to 30, 2004, NMRP and NARC, Kathmandu, Nepal. Pages Karki KB (2006) Impact of cropping intensification on nutritional balance in Nepalese soils. Procs. Int l. Seminar on Environmental and Social Impacts of Agricultural Intensification in Himalayan Watersheds. Held Oct , 2006, Kathmandu, Nepal. P Lehmann, J. and Rondon, M., 2006, Biochar soil management on highly weathered soils in the humid tropics. In Uphoff N (ed.), Biological Approaches to Sustainable Soil Systems, CRC Press, Boca Raton, FL, pp Lehmann, J., et al., 2003, Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments, Plant and Soil, 249: Lehmann, J., Gaunt, J., and Rondon, M., 2006, Bio-char sequestration in terrestrial ecosystems a review. Mitigation and Adaptation Strategies for Global Change, 11:

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