Food for thought. And fuel – Your restaurant leftovers may be used to fuel your home soon. Experts at the AZTI-Tecnalia technological centre in Spain are looking at different methods to derive energy from waste from the food industry as well as agriculture. The main procedure being studied involves extracting a biogas from food by a process called anaerobic digestion. The digestion breaks down the food matter into a sludge, which can be used as fertilizer in agriculture, and a biogas that contains methane and carbon dioxide, which can be used as energy for fuel. The plant is available for use for government, food enterprises, and environmental institutions who are interested in developing energy from food products.
http://esciencenews.com/articles/2009/03/31/obtaining.biogas.food.industry.waste