Carbon emission reduction potential of a typical household biogas system in rural China

Given the rising expectations for the substitution of fossil energy with renewable energy as one of the solutions to cope with climate change, the carbon emission reduction potential of possible solutions should be evaluated in a holistic and systematic way. In this paper, a systematic account of carbon emission reduction potential was conducted for a typical household biogas system with a digester volume of 8 m3, using a hybrid life-cycle assessment method. Using a 20 year operation scenario, the total life cycle CO2 emission of this family-size biogas utilization system is 2.60 tons, i.e., 0.02 kg CO2/MJ, of which 98.46% is attributed to indirect emissions from building materials and labor inputs. Considering the carbon emission savings due to energy and fertilizer substitution, the annual CO2 emission reduction potential is 1.25 tons for the biogas system that is under consideration. Consequently, such rural household biogas systems should be operated for at least 1.78 years to achieve a positive reduction benefit, i.e., cumulative CO2 emission savings could offset the life-cycle-related CO2 emissions. The results also indicate that long-term, stable running and maintenance are key points to maximize the benefits of household biogas as an effective approach for carbon emission abatement in the rural areas of China.