Title: Biogas energy production from tropical biomass wastes by anaerobic digestion Authors
Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2014
Publication Date: N/A
Interpretive Summary: Anaerobic digestion (AD) occurs when microorganism breakdown organic matter in the absence of oxygen. The end product of this process is biogas which can be used to produce heat, electricity, compressed natural gas (CNG) and liquefied natural gas (LNG). The remaining product, which contains high levels of nitrogen and phosphorus, can be used as a soil amendment. Here we use anaerobic digestion on agricultural waste common to Hawaii including waste taro from a poi factory, cull papaya from a packing plant, and remnant sweet potato from a harvested field. Albizia is a fast growing weed tree in Hawaii’s forest. For albizia wood chips and leaves, a liquid form of anaerobic digestion system resulted in greater amount of biogas per weight of albizia while solid digestions systems produced larger amounts of biogas. Taro, papaya and sweet potato as a single source or in combinations produced high levels of biogas indicating these would be good sources for energy production.
Technical Abstract: Anaerobic digestion (AD) is an attractive technology in tropical regions for converting locally abundant biomass wastes into biogas which can be used to produce heat, electricity, and transportation fuels. However, investigations on AD of tropical forestry wastes, such as albizia biomass, and food wastes, such as taro, papaya, and sweet potato, are limited. In this study, these tropical biomass wastes were evaluated for biogas production by liquid AD (L-AD) and/or solid-state AD (SS-AD), depending on feedstock characteristics. When albizia leaves and chips were used as feedstocks, L-AD had greater methane yields (161 and 113 L kg-1 VS, respectively) than SS- AD (156.8 and 59.6 L kg-1 VS, respectively), while SS-AD achieved 5-fold higher volumetric methane productivity than L-AD. Mono-digestion and co-digestion of taro skin, taro flesh, papaya, and sweet potato achieved methane yields from 345 to 411 L kg-1 VS, indicating the robustness of AD technology.