Evaluation of methane emission flux from a typical biogas fermentation ecosystem in China

Abstract

To reduce greenhouse gas emissions and promote sustainable agricultural practices in China, this study used conventional method to examine methane (CH4) production from hydraulic biogas digesters in Jiuxi Town, Yunnan Province, China. The static chamber technique was utilized to measure CH4 emission fluxes from the inlet and outlet of the biogas digesters. For the 100 m3 biogas digester, CH4 emission fluxes from the inlet, outlet, and the biogas digester were 1.043 g/(m2·h), 2.328 g/(m2·h), and 52.669 g/(m3·d); while those for the 8 m3 biogas digester were 0.156 g/(m2·h), 0.083 g/(m2·h), and 23.580 g/(m3·d), respectively. The diurnal and monthly variation of CH4 emission fluxes were further analyzed from the 100 m3 biogas digester. Among the environmental factors, the fermentation temperature and feeding quantity had significant effects on the CH4 emission fluxes. Especially, CH4 leakage from the digesters was evaluated, which would help identify and adjust the methane conversion factor for the typical biogas fermentation ecosystem used in China. For the hydraulic biogas digesters of 8 m3 and 100 m3, the respective leakage ratios were 3.01% and 14.56%. Therefore, it is very important for rural farmers in China to improve the management of household biogas digesters for reducing greenhouse gas emissions.