Determination of the potential energy contribution and green house gas mitigation of small and medium anaerobic digester systems in Bangladesh

This research is to determine the anaerobic digestion (AD) potential and green house gas mitigation of small and medium anaerobic digester systems in Bangladesh which could provide energy for the country's need. This was determined for two common feedstocks: cattle dung and poultry litter. A third potential feedstock is also investigated as a novel and significant new source: waste rice straw used in cattle markets. These three feedstocks were chosen because between them, they cover a large fraction of scenarios in the country where AD could be used. All of the data needed to determine the energy parameters of these three representative AD facility types were collected (i.e. biogas yield, biogas composition, life cycle data). Highest biogas yield of 0.099 m3/kg feedstock and methane percentage 74.4% were found from cattle market rice straw feedstock. The relative potential contributions to energy were then calculated. Where no reliable secondary data was available, primary data was obtained, through site visits and surveys. In order to determine the potential distribution of these representative AD facility types across the country, a survey of 125 smallholdings/farms in one district was carried out. This showed that 70% of the potential energy from AD would come from the cattle feedstock (87% of energy for the cattle feedstock would come from domestic plants). The poultry feedstock contributes 16% of the potential energy (63% of energy from poultry feedstock would come from medium sized plant) and the rice straw from the cattle markets is 14% (53% large and 47% very large). The energy capacity is presented in terms of the potential development of small, medium and large AD facilities. The total potential for biogas energy from cattle farms, poultry farms and cattle market rice straw in Bangladesh is 240 x106 MJ (240 TJ). This energy is equivalent to 66.7 x 106 kWh which can meet the cooking energy requirements of 30 million people in Bangladesh. This study also contains a Life Cycle Assessment (LCA) and the result showed that the lifetime Global Warming Potential (GWP) of a 3.2 m3 cow dung fed AD plant is 130 tonnes of CO2 equivalent. Biogas as cooking fuel can reduce the GWP by 109 tonnes of CO2 equivalent. It means the reduction of GWP of a domestic AD plant is of 84% to 21 tonnes CO2 equivalent.EThOS - Electronic Theses Online ServiceGBUnited Kingdo