Anaerobic digestion (AD) is the biological decomposition of organic matter with little or no oxygen. The anaerobic digestion process occurs naturally in marshes and wetlands. There are a variety of controlled systems where anaerobic technology is currently utilized in the United States, including wastewater treatment facilities (also Public-Operated Treatment Works or POTWs), and dairy manure digesters. In other countries (primarily in Europe), anaerobic technology is utilized in municipal solid waste digesters to produce energy and to reduce the volume of solid waste that must be landfilled.
CalRecycle is encouraging the development of technologies that divert organic waste from landfills and comply with the Global Warming Solutions Act of 2006 (AB 32). AB 32 calls for the reduction of greenhouse gases and the use of low carbon fuels, and solid waste landfills are a significant source of greenhouse gases due to decomposition of organic material in landfills into methane. Anaerobic digesters are being considered for many projects to divert organic materials from landfills and produce low carbon fuels.