The natural waste produced by animals in Greece is enough to run several power stations each year, researchers have discovered and have called for the wider use of biogas as a renewable source of energy. Christos Zafiris, the head of the project at the Center for Renewable Energy Sources, said that the study showed that some 17 million tons of organic waste which is discarded in Greece every year could be used to create enough biogas to power several 350 MW electricity plants. Biogas is usually produced by the anaerobic digestion or fermentation of organic matter, including manure, sewage sludge, animal waste or biodegradable feedstock. The biofuel is comprised mostly of methane (55 to 70 percent) and carbon dioxide (30 to 45 percent) and makes use of material that would normally be discarded. «Items from abattoirs, particularly animal fat, is like gold for energy production,» said Zafiris. He explained that the waste is stored in a special container with no oxygen for 20 to 30 days to produce biogas. Gas is produced in a similar manner at landfills as a side effect of the organic waste that collects at the garbage dumps. The waste is compressed under the pressure of the rubbish that is piled on top of it. Then, as the conditions become anaerobic, the organic waste is broken down and landfill gas is produced and released into the atmosphere, often causing fires or explosions. «The biogas produced by the organic waste and not the rest of the garbage is what burns at landfills,» said Zafiris. The remains of animals at abattoirs are usually buried – sometimes without having been through a process to make sure the waste cannot contaminate the water table. Currently, some 3,000 power stations in Europe are powered by biogas. It is also used to power trains and cars. Zafiris called for Greek authorities to consider using this environmentally friendly form of fuel, which is also cheaper than diesel and unleaded petrol.