Abstract: The present invention relates to a process for generation of heat and/or power comprising a membrane reactor where a fuel is oxidized and further comprising an improved method for reducing emissions of carbon dioxide and emission of oxides of nitrogen from said process. There is applied a membrane reactor being a mixed oxygen ion and electron conducting membrane reactor comprising a first surface (feed side) capable of reducing oxygen to oxygen ions and a second surface (oxidation side) capable of reacting oxygen ions with a carbon containing fuel. The carbon containing fuel is mixed with recycled CO2 and H2O containing exhaust gas before being supplied to the oxidation side of the membrane reactor. The air is heated before being supplied to the feed side of the membrane reactor at about atmospheric pressure. The CO2 containing gas mixture from the process can be injected in an oil and gas reservoir for enhanced oil recovery or to a geological formation.