Open-field Burning Research Articles

Valorization of xylose-rich hydrolysate from rice straw, an agroresidue, through biosurfactant production by the soil bacterium Serratia nematodiphila

Biosurfactants, amphiphilic compounds that reduce interfacial tension in oil-aqueous mixtures, are used in the petroleum, pharmaceutical, food, and agriculture industries. Fermentative production of biosurfactants requires expensive sugar or lipid substrates. Lignocellulosic biomass is a relatively cheap and abundant agricultural residue that can be used as an alternative substrate. Currently, several million tonnes of rice and wheat straw are generated globally as agricultural residues, most of which is disposed by open-field burning thereby leading to severe environmental pollution. This study aimed to produce biosurfactants in xylose-rich hydrolysates generated from rice straw. The hydrolysate is also a byproduct of 2G biofuel processes that often goes underutilized. A soil bacterium capable of growing and producing biosurfactants in rice straw hydrolysates, which typically contain growth-inhibitory compounds such as furfural and hydroxymethyl furfural, was isolated. Interestingly, the organism, identified as Serratia nematodiphila, exhibited higher glycolipid formation (4.5 ± 0.6 gL−1) in xylose-rich hydrolysate than in glucose-rich enzymatic hydrolysate (3.1 ± 0.2 gL−1) despite the higher bacterial cell density observed with the latter. The biosurfactants were thermostable and possessed promising emulsifying property and anti-microbial activity against bacteria and yeast. Further optimization of C:N resulted in a 2.8-fold increase in glycolipid production from xylose-rich hydrolysates. This study demonstrates the production of glycolipid biosurfactants from lignocellulosic biomass, a low-cost substrate and offers a plausible strategy for the management of these residues. Further, it also provides insights into the generation of additional high-value compounds in a bioethanol biorefinery to improve its commercial feasibility.

Energy use efficiency of crop residue management for sustainable energy and agriculture conservation in NW India

In the Indo-Gangetic plains of South Asia, the triple challenges of diminishing farm profitability, deteriorating natural resources and energy deficits threaten conventional agricultural sustainability. This threat is intensified by the open field burning of crop residues that not only squander an indirect renewable source of energy but also impair the soil and environment quality. The crop residues can be used as organic manure by retaining the residues as mulch in the field. After a long term (5-yrs) study, it was concluded that crop residues biomass contributed maximum (∼79%) in total input energy (1,68,556 MJ ha−1) in conservation agriculture (CA) based systems, however fertilizer application (non-renewable energy source) contributed maximum (∼50%) to the total energy (40,636 MJ ha−1) in conventional tillage (CT) based maize-wheat cropping system.CA based maize systems recorded higher input energy and energy intensiveness by 23 and 57% respectively, and recorded almost 44% lower energy use efficiency and energy productivity compared to CT based maize systems. On 5 years average basis, Zero tillage based maize-wheat-mungbean with nutrient expert cropping system(ZT/MWMb + NE) utilized 351% more input energy, which resulted in25%higher output energy and 363% higher EI compared to CT/MW (40,636 MJ ha−1, 4,20,197 MJ ha−1, 39.60 MJ USD−1).

A Review on the Fate of Nutrients and Enhancement of Energy Recovery from Rice Straw through Anaerobic Digestion

Open field burning and tilling the rice straw (RS) back into the fields causes environmental threats by contributing to the increased greenhouse gas emissions. Energy and nutrient recovery from RS through anaerobic digestion (AD) is an effective solution for its utilization. Although RS has good methane potential, its characteristics make it a difficult substrate for AD. This paper reviews the characteristics of RS, mass balance, and distribution of nutrients into liquid and solid digestate in the AD. The present review also discusses the effect of temperature, co-digestion, mixing, inoculum, organic loading rate, recycling liquid digestate, the addition of trace elements, and their bioavailability on the enhancement of biogas/methane yield in the AD of RS. In addition, the digestion of RS at various scales is also covered in the review.

Crop straw utilization and field burning in Northern region of Ghana

Efficient utilization of crop straw is a determining factor for cleaner production and sustainable development in Ghana’s agricultural sector. However, extensive field burning of crops straw is hampering the effective utilization of straw resources in the Northern region of Ghana. The aim of this research was to identify rural households’ crops straw utilization methods and investigate the occurrence as well as effects of crops straw burning. Cross-sectional data collected from 384 farmer households’ in Yendi municipality, Saboba and Tatale-Sanguli districts in the Northern region of Ghana were analyzed with Statistical Package of Social Sciences (SPSS). The total crop yield for major cereals and legumes produced was 1.29 kton with a total crop straw yield of 3.05 kton. Cereals straw contributed the highest yield percentage of 56.4% while legume straw contribution was 43.6%. About 1.23kton (40.3%) of straws from major cereals and legumes were utilized for different purposes such as returning to the field to enrich the soil, fodder for livestock, cooking fuel, sale and other traditional purposes. The remaining 1.82kton (59.7%) of crop straws were burnt on the field. The percentages of straw burnt on the field for each crop were 77.6% for maize, 58.6% for sorghum, 56.5% groundnut, 49.7% for millet, 47.4% cowpea, 42.2% for rice and 41.4% for soybean. Farming and farm size are the key influencing factors that affect straw burning. Open field burning of straws caused a decline in yield for about 65.7% of respondents. The present findings indicates that utilization of crop straw in the Northern region of Ghana is poorly practiced and needs to be encouraged because of its associated benefits. Government of Ghana needs to develop appropriate policies and legislative measures to encourage effective utilization of straw and prohibit field burning of straws.

Identifying determinants of straw open field burning in northeast China: Toward greening agriculture base in newly industrializing countries

Abstract Soil depletion caused by SB and its negative repercussions on food safety and the sustainable development of agriculture are essential concerns in newly industrializing countries. Understanding and curtailing SB in specific regions is related to the analysis of its structural characteristics and justice transition. Due to the banning policy in China, the large-scale interview of farmers' motivations and behavior regarding SB is impracticable. As such, we attempted to improve the understanding of the influencing factors of SB in northeast China (a commodity grain base) by applying the up-scaling method, by using MODIS fire data on cropland, statistical socioeconomic data, and resource and environment data as well as factor analysis and multiple linear regression analysis. We found that bio-physical factors, agricultural input-output, economic development, and crop types are significant determinants of the intensity of SB. In the end, we asserted policy implications for addressing SB in northeast China.

The Determinants of the Crop Residue Management in Pakistan: An Environmental Appraisal

This study highlights an important environmental problem of crop residue burning in open fields and investigates the main ‘cost-push’ factors of rice and wheat crop residue management in the district Gujranwala of Punjab, Pakistan. Burning of residue, is the second largest contributor to global warming after carbon dioxide, and it disturbs the key components of the agricultural ecosystem. Burning of residue is a quick way of clearing the field for the next crop. It also aids in controlling various pests, weeds, and diseases. The majority of the farmers are inclined to burn residue completely, followed by its complete removal in the study region because of the aforementioned benefits. This paper is based on a survey of 200 farmers interviewed from 28 villages of four Tehsils of the district Gujranwala, with a maximum number of 7 farmers from each village. A multinomial logit model technique is adopted to analyze the problem. Size of farm, length of straw, cattle ownership, avoiding late plantation of next crop and distance of the field from farmers’ homes were found significantly affecting farmers’ decision of following a particular residue management practice for rice crop. The use of wheat chopper machine, reading habits of agricultural publications and combine harvester were found main determinants for wheat residue management practices. Based on the results, we suggest a compensation mechanism to the farmers, similar to Payment for Ecosystem (PES) for the complete removal or incorporation of residue as it is an expensive solution. We also recommend an awareness-raising campaign regarding the use of wheat chopper machine and Kubota harvester to reduce open field burning of residue and the use of crop residue for bio-energy consumption.

Connecting Crop Productivity, Residue Fires, and Air Quality over Northern India

Northwestern India is known as the “breadbasket” of the country producing two-thirds of food grains, with wheat and rice as the principal crops grown under the crop rotation system. Agricultural data from India indicates a 25% increase in the post-monsoon rice crop production in Punjab during 2002–2016. NASA’s A-train satellite sensors detect a consistent increase in the vegetation index (net 21%) and post-harvest agricultural fire activity (net ~60%) leading to nearly 43% increase in aerosol loading over the populous Indo-Gangetic Plain in northern India. The ground-level particulate matter (PM2.5) downwind over New Delhi shows a concurrent uptrend of net 60%. The effectiveness of a robust satellite-based relationship between vegetation index—a proxy for crop amounts, and post-harvest fires—a precursor of extreme air pollution events, has been further demonstrated in predicting the seasonal agricultural burning. An efficient crop residue management system is critically needed towards eliminating open field burning to mitigate episodic hazardous air quality over northern India.

Optimization of a downdraft furnace for rice straw-based heat generation

Open-field burning, a widely used treatment and disposal method for rice straw, poses severe health and environmental problems due to the release of toxic gases and loss of significant soil nutrients. Hence, alternative techniques must be explored. In this study, the use of rice straw as feedstock for a downdraft small-scale furnace to produce heated air for paddy drying was investigated. A two-level factorial experiment was initially implemented using differently conditioned rice straw types, rice straw feed rates, and drying airflow rates. Optimization results using Response Surface Methodology (RSM) showed there is no significant difference in the drying air efficiency using either loose or baled straw. The optimum conditions found were at a rice straw feed rate of 20.67 kg h−1 and drying airflow rate of 3.03 m3 s−1, resulting in a drying air efficiency of 86.1%, and an increase in drying air temperature of 18.41 °C which was sufficient for paddy drying applications. At the optimum conditions, the average CO and NOx concentrations measured inside the dryer simulator were 76.57 and 2.93 ppm, respectively. The results of this research can be used for pilot studies in actual agricultural cooperatives, as well as provide inputs to life cycle analysis.

Spatiotemporal Variations of Fine Particulate Organic and Elemental Carbons in Greater Tokyo

Hourly concentrations of fine particulate OC and EC are monitored for more than one year by optical monitors at three sites in and out of Tokyo, Japan. Distances between the sites are 20 to 50 km. SOC concentrations are estimated from the OC and EC concentrations by an EC tracer method. Site A in an industrial site shows higher EC concentrations than site B in a residential area, but differences between the sites are much reduced for OC. Site C in a rural area, where measurements are available in colder months, shows pronounced seasonal variations with high peaks in October and December and characteristic diurnal variations in OC with the highest in the evening in October, due probably to open field burning. Photochemical formation of SOC is suggested but does not rise up so much OC concentrations in summer, which are quite lower than other seasons. A comparison between relative concentrations of EC among the sites and local emissions amounts indicates missing or considerable underestimation of EC emissions near the rural site C. Time lag correlations suggest transport of OC produced by open field burning around site C to site A. These findings would be useful for improving model performances in OC/EC predictions.

Potential emission reductions by converting agricultural residue biomass to synthetic fuels for vehicles and domestic cooking in China

Vehicle exhaust and transported biomass burning emissions are important air pollution sources in many urban areas, and domestic cooking with biomass fuels causes indoor air pollution in many rural areas. Using agricultural waste-generated synthetic fuels can reduce emissions both from vehicles and biomass burning. To estimate the potential benefits of synthetic diesel in Beijing, the emission factor model for the Beijing vehicle fleet was applied to estimate exhaust emissions for the 2015–2030 period. Compared with 100% petroleum diesel, a 20% synthetic diesel blend reduced diesel fleet emissions by 24% for carbon monoxide, 30% for total hydrocarbons, 5.5% for nitrogen oxides, and 19% for fine particulate matter with an aerodynamic diameter of ≤2.5μm (PM2.5) while using 100% synthetic diesel decreased emissions by 36% for carbon monoxide, 48% for total hydrocarbons, 10% for nitrogen oxides, and 34% for PM2.5. The use of biomass for producing synthetic fuels rather than burning in the field also reduces air pollution. Over 60g of PM2.5 agricultural open-field burning emissions are avoided per liter of synthetic fuel produced. Replacing solid crop residues with synthetic liquid fuels in household cooking would reduce PM2.5 emissions by more than 90%.

Environmental impact comparison of typical and resource-efficient biomass fast pyrolysis systems based on LCA and Aspen Plus simulation

Few studies on biomass utilization have focused on resource perspective, particularly for integrated utilization systems. Resource utilization of biomass shows great importance of environmental impact and has a good application prospect. Biomass can be converted to value-added fuels or chemicals via thermochemical method. Typical biomass utilization (TBU) system involves conventional pyrolysis and bio-oil upgrading processes, while resource-efficient biomass utilization (RBU) system is a synthetically way to save significant energy. We compared the environmental impact of a TBU system and a RBU system based on life cycle assessment (LCA) and Aspen Plus simulation in this study to explore the environmental impact of biomass utilization. The two systems were simulated using 72 model compounds in Aspen Plus V8.8, and environmental impacts were compared based on the LCA method. Results showed that compared with the TBU system, the RBU system, which was designed to produce multiple high added-value products based on fast pyrolysis and rectification, had lower environmental impacts. The greenhouse gas emissions of the RBU system reduced by 29%, and the impact factors of ADP, AP, EP, ODP, and HTP reduced by 64.3%, 69.6%, 26.8%, 10.8%, and 63.3%, respectively compared with those of the TBU system. Although two systems had higher impact in some categories than open-field burning, such as ADP, ODP, and HTP, they had considerably lower GWP and EP impacts compared with those of open-field burning. Therefore, the way of biomass resource processing and reuse should be advocated. From the perspective of comprehensive environmental impact, it is necessary to reduce the open burning. Biomass production and fast pyrolysis were identified as the key factors for reducing environmental impacts. We aimed to provide insights into efficient exploitation of biomass resources by comparing the environmental impacts of the two systems.

Effects of water and rice straw management practices on water savings and greenhouse gas emissions from a double-rice paddy field in the Central Plain of Thailand

Abstract Rice-rice (double-rice) cropping in the Central Plain region of Thailand relies heavily on irrigation water inputs for cultivation under flooded conditions, which is increasingly constrained by water scarcity. In this production system, farmers often burn or incorporate rice straw (RS) in the field. The effects of the combined use of water and RS management on irrigated lowland double-rice cropping, with respect to irrigation water savings, grain yields, and greenhouse gas (GHG) emissions, remain largely unknown. Field experiments of two consecutive rice-growing seasons in 2016–2017 were conducted at the Ayutthaya Rice Research Center in Ayutthaya, Thailand, to investigate the effects of different water and RS management practices on irrigation water savings, rice grain yields, and GHG emissions. The treatments consisted of two water regimes (continuous flooding [CF], alternate wetting and drying [AWD; 15 cm threshold water level below the soil surface for irrigation]) and three RS management practices (RS incorporation [RS-I], RS burning [RS-B], without RS incorporation and burning [WRS]). Parameters such as irrigation water inputs, soil characteristics (pH, temperature, water content), above-ground biomass, and grain yields were measured. The static vented flux chamber technique was used to measure GHG emissions (CH4 and N2O fluxes). AWD irrigation significantly reduced water inputs compared to CF in both growing seasons; however, there were more water savings in the dry season. AWD also resulted in higher grain yields compared to CF in both growing seasons. The average CH4 emissions from WRS plots were significantly lower compared to both RS-I and RS-B plots, regardless of the growing seasons. However, RS-I and RS-B plots under AWD had 39% and 63% lower CH4 emissions, respectively, in the wet season, while the corresponding values were 37% and 36%, respectively, in the dry season compared to the average CH4 emissions from these RS treatments under CF. Water and RS management did not significantly influence the average flux of N2O emissions from paddy fields in the wet season; however, CF had a lower average N2O flux than AWD in the dry season. The average flux of N2O emissions were very low compared to the CH4 emissions flux in both seasons. Averaged across two seasons, the yield-scaled global warming potential (GWP) under AWD was reduced by 34% compared to CF, and under WRS it was reduced by 36% and 29% compared to RS-I and RS-B, respectively. RS application, either as soil incorporation or open-field burning, had little or no effect on irrigation water savings and grain yields; however, the yield-scaled GWP was significantly higher from plots with RS-I or RS-B than WRS plots. Among the water regime and RS management practices tested, AWD irrigation without any RS application (soil incorporation or burning) can be employed for maintaining the yield-scaled GWP of irrigated lowland double-rice cropping at a low level.

The effectiveness of regulations and technologies on sustainable use of crop residue in Northeast China

Burning agricultural residue adversely affects air quality and results in a loss of valuable nutrients required to improve soil quality. Sustainable use of crop residue can reduce air pollution from open field burning. In addition to the mandatory regulation on burning crop residue, the Chinese government also promotes the sustainable use of crop residue by subsidizing residue chopper machines and establishing agricultural demonstration sites. This paper documents the trends of crop residue utilization and evaluates the effectiveness of different regulations and technology policies toward the sustainable use of crop residue in Northeast China. Using a unique household level panel dataset, our regression results show that the ban on burning crop residue does not reduce crop residue burning, while increased availability of residue choppers induces farmers to adopt residue retention. Establishing demonstration projects also helps promote the acceptance of residue retention. Given the low level of availability of residue choppers and demonstration projects and their effectiveness, our results recommend further supporting the spread of residue chopper machines through subsidization and establishing demonstration projects. This paper also lends experience to other developing countries that have similar issues.

Efficient Fractionation of Lignin- and Ash-Rich Agricultural Residues Following Treatment With a Low-Cost Protic Ionic Liquid.

Agricultural residues from rice, wheat and sugarcane production are annually available at the gigaton-scale worldwide, particularly in Asia. Due to their high sugar content and ash compositions, their conversion to bioethanol is an attractive alternative to their present disposal by open-field burning and landfilling. In this work, we demonstrate application of the low-cost protic ionic liquid triethylammonium hydrogen sulfate ([TEA][HSO4]) for pretreatment of rice straw, rice husk, wheat straw and sugarcane bagasse. The feedstocks had high ash (up to 13 wt%) and lignin content (up to 28 wt%). Pretreatment effectiveness was examined at 150 and 170°C and an optimal pretreatment time was identified and characterized by glucose release following enzymatic saccharification (i.e., hydrolysis), biomass delignification observed by compositional analysis, and lignin recovery. The isolated lignin fractions were analyzed by 2D HSQC NMR to obtain insights into the structural changes occurring following ionic liquid pretreatment. After treatment at 170°C for 30–45 min, enzymatic hydrolysis of three agroresidues gave near-quantitative glucose yields approaching 90% while rice husk gave 73% yield. Glucose release from the pulps was enhanced by saccharifying wet pulps without an air-drying step to reduce hornification. According to pulp compositional analysis, up to 82% of lignin was removed from biomass during pretreatment, producing highly digestible cellulose-rich pulps. HSQC NMR of the extracted lignins showed that delignification proceeded via extensive cleavage of β-O-4′ aryl ether linkages which was accompanied by condensation reactions in the isolated lignins. The high saccharification yields obtained indicate excellent potential for valorization of low-cost agroresidues in large volumes, which is promising for commercialization of biofuels production using the ionoSolv pretreatment technology.

Crop residue open field burning in Pakistan; multi-year high spatial resolution emission inventory for 2000–2014

Over recent years, crop residue burning has become a widely practiced agricultural activity in developing countries due to varying economic and social reasons. To estimate current pollution generation from crop residue burning in Pakistan, an emission inventory was developed based on district level crop production data from 2000 to 2014. Spatial distribution of quantified emissions was achieved by using MODIS Active Fire Data (MOD/MYD14A1) at 1-day temporal and 1 × km spatial resolutions. The fire occurrences were extracted over agricultural land using land cover data provided by European Space Agency/Climate Change Initiative (ESA/CCI) at 300 m spatial resolution for 2000 to 2014. Results show that CO emissions have increased by 40% at an average annual rate of 2.7% from 1.16 Tg in 2000 to 1.63 Tg in 2014 and increase in emissions of CO2, CH4, NMVOCS, N2O, NH3, SO2, NOx, PM2.5, PM10, OC and BC ranged between 37%, to 63% during same period. Spatially, CO emissions were more significant in districts of Punjab and Sindh provinces with intensive agricultural activities as compared to other areas of Pakistan with highest emission grids located in Muzaffargarh, Jafferabad, and Noushahro Feroze districts. Crop residue burning exhibited similar trend with highest emissions in June followed by February and November over 15-year period. The emissions for most of the considered pollutants were comparable to the limited previous studies available. Finally, the study conducted provides better understanding regarding spatial and temporal patterns of crop residue burning across Pakistan and can be utilized for air quality modeling and management with higher accuracy.

Straw Utilization in China—Status and Recommendations

As the world’s largest grain producer, China’s straw yield was 700 million tonnes in 2014. With a national utilization rate of 80% in 2015, there is still a large amount of straw burned in open-field, resulting in air pollution and a reduction in the quantity available as a source of bioenergy. This paper conducts a literature review of success stories and major challenges in comprehensive straw utilization in and out of China. It is noted that nationwide long-term feasible and sustainable straw utilization at a high rate is a highly complex operation, involving most societal sectors, many people and facilities often at different regions. Scenarios were analyzed to estimate the energy potential and air emission reductions China would accomplish in 2020 by converting an additional 5 or 10% of straw-yield to biofuel. Currently, the approach to control straw burning in China is primarily administrative, relying heavily on prohibition and penalties, inconsistent across policy areas and geography, and lacking in long-term planning. Consequently, the effectiveness of the current approach is limited. The main cause of burning is a lack of infrastructure, effective preventive measures, and viable alternatives. Recommendations aimed at promoting a circular bio-economy around using crop straw as resources were provided, including improving straw utilization rates and reducing open-field burning.

Encapsulation of lead in rice phytoliths as a possible pollutant source in paddy soils

Due to its serious health risks, lead (Pb) in rice, specifically its uptake, translocation, and accumulation mechanisms and its toxic effects have been studied intensively in recent years. However, it remains unclear about the role of phytolith, a siliceous structure in rice plants, in the storage and release kinetics of Pb in rice. This study aims at elucidating a possible encapsulation of Pb in the phytolith structure (phytPb), and identifying whether or not phytPb provides a source of Pb in soil, when returned to the field with the rice straw or in a related processed product such as ash from on-site burning. To date there has not been any specific work targeted at the determination of phytolith-associated heavy metals in general and phytPb in particular, and therefore this possible source of Pb in soils may have been overlooked. Phytoliths were included in a study of rice paddy soil and rice straw to demonstrate accumulation of phytolith and its associated phytPb in agricultural soils of the Red River Delta (Vietnam). The total content of Pb in rice straw samples was found to be up to 118 mg kg−1, and this Pb sink can be cycled to serve as a new Pb source in soils. The fate of Pb in rice straw might be directly related to open burning activity (a common practice in the Red River Delta), in which volatilization or sub-compartmentation in slagged phytolith appeared as controlled factors. This is supported by the findings from batch experiments for rice straw ash samples, in which release of Pb was low and a portion of Pb in rice straw were found to associate with phytolith structural organic matter. We also observed the presence of phytPb in "aged" phytolith fragments which had accumulated in the paddy field soil. However this Pb pool was relatively low (from 7.8 to 34 kg ha−1) relative to other soil Pb fractions. As the thermal treatments of Pb-tainted rice straw resulted in losses of Pb via volatilization, open-field burning practices for Pb-contaminated rice straw is suggested as an environmental risk.

The Potential of Rice Straw in Agricultural Activities in the MADA Region of Kedah, Malaysia

Ineffective straw management by open field burning, leaving it on the field, and dumping it in landfill causes serious environmental degradation and adversely affects public health. This study assesses the level of farmers’ knowledge on straw potential and the benefits of using straw in agricultural activities. Descriptive analysis was carried out on 160 farmers in the Muda Agricultural Development Authority (MADA) agricultural region in Kedah who manage straw in an environmentally-friendly manner. Results show that most of farmers lack knowledge in using straw in agricultural activities. The interviews revealed that the re-use of straw in the agricultural activities would enhance soil quality, improve the growth quality of plant, improve livestock and seedling germination, increase yield production; and reduce the cost of farm management. Given the economic value and high potential, straw could stimulate the wider rural economy through added-value as well as generally increase the socioeconomic class of farmers and improve the agricultural environment.

Addressing environmental implications of crop stubble burning in Pakistan: innovation platforms as an alternative approach

Pakistan's eastern provinces are very badly affected by haze and smog caused by burning of rice straw and stubbles after reaping season. This practice causes emission of greenhouse gases and pollutant materials which not only has severe health consequences but also the main source of traffic disturbance and accidents due to poor visibility. A ban on burning of crop residue deems to be ineffective without alternative means and consultation of farmers. Previous studies were aimed to figure out causes, contributing factors and impacts of stubble burning, but largely ignored farmers choices and market environment. In this study, a survey-based farmers' preference order was obtained through hybrid AHP-TOPSIS model. The analysis traces out why most of the farmers prefer open field burning. The present study proposes a national residue management service (NRMS) platform based on preferences of the alternatives and considering market externalities. This research provides an appropriate mechanism and policy suggestions to policy makers and practitioners that may help in minimising the environmental impacts due to improper management of the crop residue.

Agricultural Wastes – A Promising Source for Biogas Production in Developing Countries of the Tropical and Subtropical Regions

Most of the so called developing countries are located in tropical and/or sub-tropical regions whilst in contrast, most of the developed countries are in the temperate climate zones. It is expected that a huge increase in the future global energy consumption will be caused by the demand of the developing countries. Caused by the favourable climate conditions in tropical and/or sub-tropical regions the average productivity of biomass is 4 – 5 times higher than that of biomass grown in the temperate regions. Many of the developing countries today are agricultural and agro-industrial countries producing huge amounts of agricultural residues and wastes that can be used as source for energy generation. It is estimated that if only all process-based agricultural residues alone would be used, they could contribute between 25 % and 40 % of the total primary energy demand in such regions [1]. Until now, the huge amount of agricultural waste generated each year in developing countries is a headache for farmers, who are obliged to get rid of it. Open field burning and improper disposal are omnipresent in many regions and pollute the environment. Converting such waste into bioenergy such as biogas by using anaerobic digestion technologies represents an alternative treatment with a promising potential. Such treatment prevents pollution, is producing valuable and climate friendly energy and will contribute to nutrient recovery by using the digestate as fertilizer. The paper will introduce some of the most promising agricultural residues in tropical and subtropical regions which can be used as substrates or co-substrates for biogas production. Results of a research project carried out in Costa Rica will be used as a case study to show the potential of two of the major agricultural residues (pineapple and banana residues) as sources for biogas production. The opportunities and prospects for the dissemination and implementation of new and more developed technologies to improve the efficiency of the technologies will be shown.