From smokestacks to sky: Technology from capturing industrial emissions may reduce DAC costs
A new review in the journal Current Opinion in Chemical Engineering argues that direct air capture (DAC) using liquid solutions could benefit from the decades of experience in post-combustion carbon capture (PCC) — but only if the technology is redesigned for air’s far lower CO2 concentrations.
The central challenge for DAC is physics: air contains just 0.04% CO2, roughly 100 to 500 times less than industrial flue gas, which sharply reduces DAC's absorber productivity and cyclic capacity. As a result, DAC CO2 absorbers must be far larger, energy demands significantly higher, and water losses potentially substantial in dry climates.
Authors Paul Feron and Ali Kiani note that DAC has so far been led by solid amine-based sorbents (e.g., Climeworks) and liquid alkaline hydroxide-based solvent systems (e.g., Carbon Engineering/1Pointfive STRATOS), despite the industrial maturity of liquid amine processes used in flue-gas capture at power plants (PCC).
Process modeling cited in the review suggests thermal energy requirements for amine-based liquid solvent DAC would be roughly three times higher than for PCC, while electricity use — mainly for industrial fans moving vast volumes of air — can be up to two orders of magnitude greater. Early techno-economic assessments place costs above $1,000 per ton of CO2 for amine-based systems.
Still, the authors argue that adaptation of existing PCC technology — rather than a complete reinvention of liquid amine for DAC — may lead to significant progress. They highlight several design priorities, including: low-cost air–liquid contactors such as modified cooling towers, nonvolatile absorbents like amino acid salts to reduce solvent losses, highly reactive capture agents to shrink absorber size, and more energy-efficient sorbent regeneration pathways. Amino acid salts in particular show promise, with modeling indicating potential cost reductions of roughly 25% compared with conventional amines.
The review also stresses that emissions management — amine degradation products, ammonia release, and water losses — must be addressed before large-scale deployment. Ultimately, the authors conclude that combining mature PCC equipment with improved solvents and regeneration strategies could meaningfully lower DAC’s cost and energy burden, but pilot-scale validation and careful environmental assessment remain essential.
