A thermodynamic analysis and related experimental studies indicate the technical feasibility of reducing CO2 emissions via combined processes based on the co-production of synthesis gas (CO+H-2) with iron or cement. These combined processes involve the reforming of methane to trap CO2 inherent in the carbothermic reduction of iron oxide and in the thermal decomposition of calcium carbonate. Replacing fossil fuels with solar energy as the source of process heat further reduces CO2 emission to zero and offers the technical possibility of reducing total global anthropogenic CO2 emissions by about 10%.