Cooking fuel is greatly needed in less industrialized nations, especially in rural areas. Several countries, such as India and Costa Rica, provide crucial government support for biodigester technology, but none more so than China. More than 30 million biodigesters have been built there, supplying renewable cooking and lighting gas for more than 100 million people.
Anaerobic composting and its biogas production have major advantages compared to traditional aerobic composting and burning biomass for cooking and lighting. These advantages are opening the door to a more sustainable rural economy in China, especially in Sichuan province, where the modern biogas movement began and government support and technical know-how is strongest.
Probably the greatest advantage with biodigesters is in their efficiency—biogas often achieves efficiencies of 60%, compared with about 10% for the typical homemade biomass-burning cook stove. Using less biomass means more living trees, less air pollution and greenhouse gas emissions, and a vast improvement in household air quality. Local water quality and sanitation is also greatly improved, as human and animal wastes can be composted in a sanitary manner. And lastly, the end product is a quality fertilizer, rich in nitrogen and free of pathogens. While there is much in China to bemoan on the environmental front, the more than 4 million biodigesters being built in rural China each year certainly provide one of the bright spots in a nation lurching toward industrialization.