Anaerobic Digestion in China

Anaerobic digestion is a scalable process, which is often overlooked in the United States and is frequently stated to be economically viable only for large farms. Dairy farms, for instance, are thought to be economical for ~500 cows or more. The scalability feature is particularly evident in China, where by 2005 more than 18 million household digesters have been installed providing 7 billion m3 of biogas per year (van Nes 2006). A common operating system is a small inground digester fed with swine waste from a few pigs and human waste. The gener­ated biogas is used in the household for cooking and lighting. The Ministry of Agriculture (MOA) aims to increase the number to 27 million household digesters by 2010. In addition to the household digesters, in 2005 there were almost 3500 medium — and large-scale biogas digesters at livestock and poultry farms (van Nes 2006; Figure 4.7).