A new process is proposed which converts CO2 and CH4 containing gas streams to synthesis gas, a mixture of CO and H-2 via the catalytic reaction scheme of steam-carbon dioxide reforming of methane or the respective one of only carbon dioxide reforming of methane, in permeable (membrane) reactors. The membrane reformer (permreactor) can be made by reactive or inert materials such as metal alloys, microporous ceramics, glasses and composites which all are hydrogen permseleclive. The rejected CO reacts with steam and converted catalytically to CO2 and H-2 via the water gas shift in a consecutive permreactor made by similar to the reformer materials and alternatively by high glass transition temperature polymers. Both permreactors can recover H-2 in permeate by using metal membranes, and H-2 rich mixtures by using ceramic, glass and composite type permselective membranes. H-2 and CO2 can be recovered simultaneously in water gas shift step after steam condensation by using organic polymer membranes. Product yields are increased through permreactor equilibrium shift and reaction separation process integration. CO and H-2 can be combined in first step to be used for chemical synthesis or as fuel in power generation cycles. Mixtures of CO2 and H-2 in second step can be used for synthesis as well (e.g., alternative methanol synthesis) and as direct feed in molten carbonate fuel cells. Pure H-2 from the above processes can be used also for synthesis or as fuel in power systems and fuel cells. The overall process can be considered environmentally benign because it offers an in-situ abatement of the greenhouse CO2 and CH4 gases and related hydrocarbon-CO2 feedstocks (e.g., coal, landfill, natural, flue gases), through chemical reactions, to the upgraded calorific value synthesis gas and H-2, H-2 mixture products.