Evaluating the Scale of Natural and Mechanical Airflows for Surface-Based Atmospheric Pollutant Removal.

Removal strategies for atmospheric pollutants are increasingly being considered to mitigate global warming and improve public health. However, the global potential of surface-based removal techniques has not yet been quantified under atmospheric transport. We evaluate the atmospheric pollutant transport to surfaces and assess the potential of surface-based removal technologies across infrastructure. Cities provide the highest transport-limited removal potential, with median annual atmospheric flow rates of 30 GtCO2, 0.06 GtCH4, 0.007 GtNOx, and 0.0001 GtPM2.5 to their total surface area. Cities and HVAC systems have flow rates large enough to potentially remove more than 1 GtCO2/y (1 GtCO2e/y for CH4, 20-year GWP), if laboratory-scale removal efficiencies are achieved under current atmospheric concentrations. HVAC filters have the potential to achieve costs as low as $600 per tCO2 removed ($2000 per tCO2e) if CO2-sorption (CH4-catalyst) technologies are incorporated into their surfaces and maintained through replacement, compared with $3000 per tCO2 ($10,000 per tCO2e) for cities, using literature material and application costs. These estimates exclude regeneration energy, associated electricity use, and downstream processing. These findings suggest that integrating surface-based pollutant removal technologies into infrastructure could support climate mitigation, although further work is needed to assess feasibility, deployment, and cost in application.