Life cycle inventory assessment of a livestock waste treatment plant
2006
Muroyama, K.(Kansai Univ., Suita, Osaka (Japan). Faculty of Engineering) | ; Nakagawa, Y. | ; Hayashi, J. | ; Sakamoto, Y. | ; Hayashi, T. | ; Nakata, T.
Yagi Bio-Ecology Center (YBEC), Yagi Town, Kyoto, treats the wet-biomass wastes including livestock feces and urine collected from livestock farms and bean curd refuse from food factories in a mesophilic digestion tank to produce biogas which is then converted into electricity via a gas engine generator. The livestock waste treatment plant successfully achieves zero-emission because the dewatered sludge cake from the anaerobic digestion tank is aerobically fermented with the addition of fresh cattle feces and saw dust to produce compost products. In the present study, a life cycle inventory analysis was carried out on the YBEC livestock waste treatment process in terms of the cumulative CO2 emission unit as an environmental impact index, considering the CO2 emission by truck transportation for collecting the raw wet-biomass waste materials, the contributions of the utility inputs such as water, electricity and fuel oils required for the daily process operation and the initial construction of the process facilities. As a result, it was found that the YBEC livestock wastes treatment plant in the initial stage could achieve an energetically self-dependent system and could even function as a CO2 sink for a long-term operation exceeding 16 years, while self-generating excess electricity as noted in the specifications and demonstrating zero-emission. In addition, it is expected that the employment of a fuel cell generating system in place of the gas engine generator or the liquid fertilizer utilization of the liquid filtrate of the excess sludge from the digestion tank could markedly decrease the environmental impact and significantly enhance their role as a CO2 sink.
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