Carbon capture and storage (CCS) has mostly received attention as a way to limit the impact of burning coal, which emits the most CO2 of all fossil fuels. Using this approach, CO2 would be captured from the exhaust stream of a power plant and pumped into a geological formation that would store it for centuries, preventing it from influencing the climate or ocean chemistry. As emissions continue to rise, CCS has attracted attention as a way to emit now and fix the problem later. The same technology that isolates CO2 from the exhaust stream of a power plant could also conceivably pull it right out of the atmosphere.
But how much does it cost? Some initial estimates put the cost of CCS from the atmosphere at under $200 per ton. But a new analysis in PNAS suggests these estimates are misguided—we already know how much it costs to obtain trace chemicals from a mixture, and it's a whole lot more expensive than that.
The PNAS authors focus on two things: a thermodynamic analysis of CCS, and an empirical evaluation based on our experience with industrial processes for isolating trace gasses.