Air pollution impacts of amine scrubbing for CO2 capture

The current political discussion in the United States around carbon capture and storage includes statements that suggest a need for a technical review to clarify the expected air pollution impacts of amine scrubbing. The Center for International Law and 50 other organizations published an open letter claiming that “CCS is not consistent with the principles of environmental justice… CCS makes dirty energy even more dangerous for frontline communities. Facilities equipped with carbon capture technology have to burn more fossil fuel to get the same energy output, resulting in increased emissions of toxic and hazardous pollutants, like fine particulates (PM2.5).”

This paper reviews air pollutants produced by the use of amine scrubbing on coal- and gas-fired power plants in the U.S. and the process features and mitigation strategies that will minimize their impact on air quality. Even with atmospheric reactions, emissions of amine, nitrosamine, and other air toxics are likely to have insignificant environmental and health impacts. Stacks will disperse emissions with a dilution factor greater than 8000. Water wash with or without acid will reduce emissions of amine and nitrosamine that is produced from atmospheric reactions. Nitrosamine emissions will be managed with selective catalytic reduction (SCR) to reduce the NO/NO₂ and/or selection of primary or non-volatile amines. With coal-fired power plants, amine aerosols, Hg, SO₃, and fine particulate emissions will probably be managed by a fabric filter with alkali addition. Carbon capture by amine scrubbing will reduce significantly the effect of the power plant emissions on ambient levels of PM2.5. With coal-fired power plants, the application of amine scrubbing will significantly reduce SO₂ emissions. NO_x emissions will usually be minimized by selective catalytic reduction (SCR) in both gas- and coal-fired plants. Ammonia emissions will be minimized by managing amine oxidation, and if necessary, by adding an acid wash or other controls.