The decomposition of organic matter by heating without oxygen or other agents, except for steam–which is sometimes used. Pyrolysis is involved when biomass or waste is converted into synthetic gas. Hydrous pyrolysis takes place with the use of water and is the type of pyrolysis that can transform waste matter into a liquid similar to light crude oil. Pyrolysis technologies are being developed as it can be used create biodiesel fuel which reduces reliance on fossil fuels.