8.1 Small-Scale Biomethanation

8.1.1. What are biomethane and biomethanation?

Biomethane (sometimes referred to as "Biogas) is generated from organic materials as they decay. The main component of biomethane is CH4 (55%-70%) and CO2 (25%-40%). Biomethane can be used for cooking, lighting, heating, generating electricity and so on.

Biomethanation is the process of conversion of organic matter in the waste (liquid or solid) to biomethane and manure by microbial action in the absence of air, known as "anaerobic digestion."

8.1.2. Situation of biomethane in China

The annual quantity of waste in China is more than 150 million tons. The production and disposal of large quantities of life and industrial waste without adequate or proper treatment result in widespread environmental pollution. While some of these wastes can be collected and biomethane is generated from anaerobic digesters where the manure decomposes. Especially in some far rural area where the transportation of electricity is expensive, biomethane is a good way to provide energy for cooking, lighting and heating, etc.

Since 1950s, Chinese governments encouraged small-scale biomethanation using animal and agricultural waste as feedstock. Table 1 shows the rural biomethane development in China. Till 2006, about 20 million families in rural area are using biomethane for cooking and lighting. Annual consumption reaches 5 million standard coal equivalent. Subsidy of 2.5 billion RMB from government is for small-scale biomethanation development, which means one small-scale biomethanation can get subsidy of 800-1200 RMB. China nation government plans to build 30 million biomethane digesters in 2010 and 45 million biomethane digesters in 2020.