Harnessing 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 based on limits of pollutant transport and removal rates. We evaluate the atmospheric pollutant transport to surfaces and assess the potential of surface-based removal technologies for global-scale deployment across a variety of configurations, including air interaction with the built environment, mechanical ventilation and convection systems, and over the global transportation fleet. Cities provide the highest transport-limited removal potential, with median annual atmospheric flow rates of 30 GtCO$_2$, 0.06 GtCH$_4$, 0.007 GtNO$_\text{x}$ and 0.0001 GtPM$_{2.5}$ to their total surface area. Cities, solar farms and HVAC systems have flow rates large enough to potentially remove more than 1 GtCO$_2$/y (1 GtCO$_2$e/y for CH$_4$, 20-year GWP), if laboratory-scale removal efficiencies from the literature are applied to their total surface area, however, achieving this would require technological advances. Based on their transport-limited upper bounds, HVAC filters have the potential to achieve costs as low as \$600 per tCO$_2$ removed (\$2000 per tCO$_2$e) if CO$_2$-sorption (CH$_4$-catalyst) technologies are incorporated into their surfaces and performance is maintained through routine replacement, compared with \$3000 per tCO$_2$ (\$10000 per tCO$_2$e) for city surfaces, using literature values for these technologies' material and application costs. These findings demonstrate that integrating surface-based pollutant removal technologies into infrastructure may offer a pathway to advance climate objectives, though further studies are needed to assess their feasibility in application, and application-implementation rates and cost.