Gas treatment WASTE of a process fischer-Tropsch

The invention relates to a hydrocarbon gas conversion process hydrocarbon liquid wherein the Fischer-Tropsch process is implemented, said Fischer-Tropsch hydrocarbon liquid and producing a waste gas comprising at least hydrogen, carbon monoxide of carbon, carbon dioxide and hydrocarbons having a carbon number of at most 6, wherein the waste gas is subjected to a separation process producing: - at least one gas stream mainly comprising hydrogen, - at least a stream comprising predominantly methane, - at least one gas stream mainly comprising inert (carbon dioxide, nitrogen, argon) and hydrocarbons having a carbon number of at least 2.