An integrated process for the gasification of coal alone or with other carbon-containing materials such as solid municipal wastes, biomass and sewage sludges, wherein the endothermic heat required by the gasification reaction is supplied at least in a significant part by the exothermic reaction of CaO in the form of calcined lime or dolomite with carbon dioxide. The CO.sub.2 is recycled to provide a high CO.sub.2 vapor pressure for the exothermic reaction. The calcium carbonate formed in the reaction is decomposed in a combustor to produce the CaO which is recycled to the gasification stage.