Implications of Ammonia Emissions from Post-Combustion Carbon Capture for Airborne Particulate Matter

Abstract

Amine scrubbing, a mature post-combustion carbon capture and storage (CCS) technology, could increase ambient concentrations of fine particulate matter (PM2.5) due to its ammonia emissions. To capture 2.0 Gt CO2/year, for example, it could emit 32 Gg NH3/year in the United States given current design targets or 15 times higher (480 Gg NH3/year) at rates typical of current pilot plants. Employing a chemical transport model, we found that the latter emission rate would cause an increase of 2.0 μg PM2.5/m(3) in nonattainment areas during wintertime, which would be troublesome for PM2.5-burdened areas, and much lower increases during other seasons. Wintertime PM2.5 increases in nonattainment areas were fairly linear at a rate of 3.4 μg PM2.5/m(3) per 1 Tg NH3, allowing these results to be applied to other CCS emissions scenarios. The PM2.5 impacts are modestly uncertain (±20%) depending on future emissions of SO2, NOx, and NH3. The public health costs of CCS NH3 emissions were valued at $31-68 per tonne CO2 captured, comparable to the social cost of carbon itself. Because the costs of solvent loss to CCS operators are lower than the social costs of CCS ammonia, there is a regulatory interest to limit ammonia emissions from CCS.