A process for converting carbonaceous materials or light hydrocarbon gases into products comprising predominately C5+ hydrocarbons. The process converts the feedstock into synthesis gas comprising hydrogen and carbon monoxide and then uses the Fischer-Tropsch reaction to produce heavy hydrocarbons. A small excess of hydrogen is produced in the syngas generator or by water gas shift for use in product upgrading and for blending with Fischer-Tropsch tail gas for recycle back to syngas generation. A portion of the Fischer-Tropsch tail gas is used as fuel, thus purging combustible light gases and CO2 from the tail gas. Hydrogen rich purge gas is blended into the remaining tail gas resulting in a recycle stream that is returned to the syngas generator. The tail gas components are therefore efficiently used to produce more products.