NOVELTY - Converting feed gas to liquid product involves partially oxidizing high-temperature gas containing oxygen, input gas containing carbonaceous fuel, and molten sulfur to generate sulfide gas containing hydrogen sulfide, carbon monoxide (CO), carbon dioxide (CO2) and hydrogen; mixing sulfide gas with feed gas to generate mixed gas having a predetermined hydrogen sulfide concentration; providing a portion of mixed gas to a production fermentor (40) containing microorganisms; and converting mixed gas to liquid product by contact with microorganisms.    USE - For converting feed gas comprising syngas to 1-4C oxygenated liquid product selected from ethanol, propanol and butanol (preferably ethanol) (claimed).    ADVANTAGE - The process can be inherently more efficient than the pretreatment/hydrolysis/fermentation process because the gasification step can convert all of the components to syngas with good efficiency (e.g. greater than 75%). The system for syngas fermentation is able to deliver the desired quantity of hydrogen sulfide gas at a controlled rate for safe and economical operation of a large scale syngas fermentation process without the need to maintain a large inventory of hydrogen sulfide gas, or inorganic sulfide salts. The microorganisms convert syngas to ethanol, propanol or n-butanol with high efficiency (e.g. greater than 90%).    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a system to convert feed gas to liquid product comprising a partial oxidation reformer (20) operable to partially oxidize high-temperature gas containing oxygen, input gas containing carbonaceous fuel, and molten sulfur to generate sulfide gas containing hydrogen sulfide, CO, CO2 and hydrogen; a mixer (30) connected to receive the sulfide gas from the partial oxidation reformer and operable to mix the sulfide gas with the feed gas to generate mixed gas having a predetermined hydrogen sulfide concentration; and a production fermentor containing microorganisms connected to receive a portion of the mixed gas and operable to convert the mixed gas to the liquid product by contact with microorganisms.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of a sulfide generation system to convert feed gas to liquid product.    Oxygen burner (10)    Burner gas stream (14)    Partial oxidation reformer (20)    Input gas stream (24)    Molten sulfur stream (26)    Sulfide gas stream (28)    Mixer (30)    Production fermentor (40)    Liquid product stream (44)    Sulfide generation system (100)