A gaseous mixture, comprising CO2, H2, H2S and optionally CO, is separated into an H2 or H2 and CO product stream (H2/CO product stream), and a CO2 enriched stream containing at least one combustible component selected from H2S, H2, CO and any additional combustible components present in the gaseous mixture. A support fuel stream, comprising one or more combustible components, is combusted to form a stable flame, and the CO2 enriched stream and flame are contacted in the presence of sufficient O2 to combust all or substantially all of the combustible component(s) present in said CO2 enriched stream. A CO2 product stream is formed from said combustion effluent. The support fuel stream may be generated from the process of generating or separating the gaseous mixture or from the H2/CO product stream. Where the CO2 enriched stream contains H2S, the support fuel stream may also be a stream obtained off-site that comprises H2S.