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In China’s rural areas, most villages do not have electricity, and commercial fuels like kerosene and coal are expensive. Thus the rural population still relies heavily on biological sources of energy. Fuelwood and crop residues (mostly straw) account for 80% of rural household energy use and 54% of total rural energy use. The thermal efficiency (i.e., the amount of heat actually used) is only about 10% for traditional stoves, so a lot of fuel is required for such simple tasks as preparing food and tea (see Figure 1). This has serious environmental consequences, such as deforestation, reduced soil fertility, erosion, and even localized desertification.  It also causes severe indoor air pollution, with resultant health effects such as upper respiratory infections and eye problems.

By just adding one simple step in the fuel cycle, biogas can alleviate many of these problems, and provide many other benefits as well. It is particularly well suited to China, where recycling and pig-rearing have long been common household activities.