The invention relates to a process for producing synthesis gas, in which carbon and hydrogen are obtained from hydrocarbon by thermal decomposition. At least a portion of the carbon obtained by the thermal decomposition is reacted, and at least a portion of the hydrogen obtained is reacted with carbon dioxide by a reverse water-gas shift reaction to give carbon monoxide and water. Carbon obtained by the thermal hydrocarbon decomposition is used as fuel in a power plant operation wherein the carbon is combusted to produce electrical power, and carbon dioxide formed in the combustion of the carbon is used in the reverse water-gas shift reaction.