To reduce the amount of CO2 being generated, processes for recirculating carbon are needed, especially those that do not require excessive energy and have high efficiencies. Hydrothermal reactions play an important role in the formation of fossil fuels, e.g., the conversion of dissolved CO 2 into hydrocarbons abiotically in the Earth's crust, and have shown excellent potential for the rapid conversion of a wide variety of biomass into value-added products. Thus, if the geologic formation of fossil fuels in nature could be combined with the hydrothermal methods being studied for material conversions, an efficient scheme could be realized to recycle carbon and produce chemicals. In this paper, we present some recent advances in our research on the hydrothermal conversion of CO2 into chemicals with biomass or organic waste or metals as reductants. These results provide fundamental understanding that opens a new path for the use of CO2 as chemical feedstock, thus speeding up the global carbon cycle.