Abstract: Based on the model recently modified for accounting of carbon mitigation and the research achievements of the scientists in China as reference for values of some key parameters, Enshi Prefecture of Hubei Province was selected for case study to evaluate effects of the popularization of rural household biogas projects in 2000-2010 on carbon mitigation from the following 4 aspects, direct carbon emission reduction by use of methane, substitution of fossil energy reducing carbon emission, carbon emission through leakage, and carbon emission from methane combustion. Results show that carbon reduction per unit (per biogas digestor) varied in the range of 1.10-1.29 tons per year, depending on specification of a digestor (number of pigs in pen and type) and air temperature, and its indirect portion (1.07 t•a^-1) was 4.9 times as much as its direct portion (0.22 t•a^-1). The annual effect on carbon mitigation in the prefecture increased with the increasing number of biogas digestors in 2000 - 2010, and the reduction of carbon emission increased from 39 700 tons per year in 2000 to 709 300 tons per year in 2010. During this period, the use of biogas digestors treating livestock manures directly reduced carbon emission by 1.5744 million tons and the substitution of coal with biogas indirectly reduced carbon emission by 3.6182 million tons, while the carbon emission from the combustion of methane increased carbon emission by 0.1312 million tons and methane leakage by 0.8994 million tons. Balancing of the four factors shows that the total carbon mitigation benefit was 4.1620 million tons.

Key words: rural area, household biogas digester, carbon emission reduction, Enshi Prefecture, accounting