Current Research on Atmospheric and Captured CO2 Utilization
Although large scale efforts to control carbon emissions are still in the future, there are currently several major research programs in the U.S. aimed at improving technologies for both recycling atmospheric carbon via biofuels and artificial photosynthesis, and for use of captured CO2 for engineering of geothermal systems, grid scale energy storage, and for enhanced hydrocarbon recovery. In this presentation I will review progress being made on these approaches and briefly discuss certain policy and implementation issues that are critical but still unresolved.
A critical issue for CO2 utilization is scale. With carbon being emitted at the rate of about 36 Gton/year CO2 equivalent, there are few ways to utilize CO2 that will offset much of this large flux. Recycling with biofuels and direct abiotic solar-to-fuel conversion constitute important potential pathways for significant emission reduction, and are attractive because they address the transportation fuels part of carbon use. Both approaches are still far from being economical, but advances are occurring at a substantial rate in the U.S., due partly to extensive investments made by the U.S. Department of Energy in large- and medium-scale research programs. Enhanced hydrocarbon recovery using captured anthropogenic CO2 can also be done at scale, and can produce a significant reduction in emissions/bbl of petroleum. This may not be an especially inspirational route to emissions reductions, but may be significant because of the scale. Other options still in an early stage of development are the use of CO2 as a working fluid in engineered geothermal systems, and as a cushion gas for compressed air energy storage. Research continues on these options, although more extensive field tests will be necessary to advance the technology.