Popularizing household-scale biogas digesters for rural sustainable energy development and greenhouse gas mitigation

Biogas utilization has undergone great development in rural China since the government systematically popularized household-scale biogas digesters for meeting the rural energy needs in the 1970s. In order to comprehensively estimate the significance of biogas utilization on rural energy development and greenhouse gas emission reduction, all types of energy sources, including straw, fuelwood, coal, refined oil, electricity, LPG, natural gas, and coal gas, which were substituted by biogas, were analyzed based on the amount of consumption for the years from 1991 to 2005. It was found that biogas provided 832749.13 TJ of energy for millions of households. By the employment of biogas digesters, reduction of greenhouse gases (GHG) was estimated to be 73157.59 Gg CO2 equivalents (CO2-eq), and the emission by the biogas combustion was only 36372.75 Gg CO2-eq of GHG. Energy substitution and manure management, working in combination, had reduced the GHG emission efficiently. The majority of the emission reduction was achieved by energy substitution that reduced 84243.94 Gg CO2, 3560.01 Gg CO2-eq of CH4 and 260.08 Gg CO2-eq of N2O emission. It was also predicted that the total production of biogas would reach to 15.6 billion m3 in the year 2010 and 38.5 billion m3 in the year 2020, respectively. As a result, the GHG emission reductions are expected to reach 28991.04 and 46794.90 Gg CO2-eq, respectively.