This invention is a reactor and a process for the conversion of organic waste material such as municipal trash, sewage, post-consumer refuse, and biomass to commercially salable materials.The invention produces the following: 1. Maximum energy conversion from the organic material 2. High volume consumption of the organic feed material 3. Less pollution of gaseous products than prior art systems 4. Solid residuals for disposal are minimal and non-hazardous. The conversion is accomplished by combining anaerobic gasification and pyrolysis of the feed organic material and making it into synthetic gas. The synthetic gas is a mixture of hydrocarbons (C.sub.xH.sub.y), hydrogen, and carbon monoxide with small amounts of carbon dioxide and nitrogen. An essential feature of the invention is a hot driver gas, devoid of free oxygen and rich in water, which supplies the entire thermal and chemical energy needed for the reactions. This hot driver gas is produced by complete sub-stoichiometric combustion of the fuel (C.sub.xH.sub.y) before it enters the reactor.