Systems and methods for heating a non-combustion chemical reactor with thermal energy from a geothermal heat source are described. A working fluid is directed from the geothermal heat source to the chemical reactor to transfer heat. The working fluid can be circulated in a closed system so that it does not contact material at the geothermal heat source, or in an open system that allows the working fluid to intermix with material at the geothermal heat source. When intermixing with material at the geothermal heat source, the working fluid can transport donor substances at the geothermal heat source to the chemical reactor.