Large-Scale Removal of Atmospheric CO2 through Biomass Chemical Looping Combustion

Combustion of fossil fuels such as coal, oil and natural gas has been identified as the key contributor to
increasing concentrations of atmospheric CO2 and associated problems of global climate change. When
fossil fuels are used, carbon is removed from the earth and is converted to CO2, resulting in a subsurfaceto-atmosphere movement of carbon. Millions of R&D dollars are being spent to make fossil fuel combustion carbon-neutral by isolating CO2 resulting from combustion, compressing it, then returning it underground (carbon capture and sequestration, or CCS). Biomass, on the other hand, is considered naturally carbon-neutral; although CO2 is emitted during biomass combustion, that same amount of CO2 is required to re-grow the plant, so that in the long run there is no net increase of CO2. Applying the CCS technologies being developed for fossil fuels to biomass presents an interesting and compelling opportunity for carbon-negative energy production. Instead of taking carbon out of the ground and moving it to the atmosphere, bio-CCS would take carbon out of the atmosphere and store it below the surface of the earth. In order to do this economically, one must use the least expensive, most efficient processes to generate energy and capture CO2. Of the many different carbon capture technology alternatives, including absorption of CO2 from combustion flue gas by e.g. MEA or chilled ammonia, oxy-firing and gasification, the simplest and lowest-cost technology is chemical looping combustion, or CLC. In CLC, a solid metal-based material consumes oxygen as it is oxidized in an air-fed reactor. The oxidized metal is transferred to another reactor in which it reacts with a fuel through “indirect combustion” to form primarily CO2 and H2O. The H2O can be removed by condensation, leaving nearly pure CO2 suitable for compression and sequestration with only minimal cleaning required. This seminar introduces chemical looping combustion and the opportunity for large-scale removal of atmospheric CO2 through bio-CLC, as well as research in this area being carried out at the University of Utah.