Direct Air Capture (Climeworks, Carbon Engineering, Heirloom)

Physics / mechanism

Direct Air Capture (DAC) pulls CO₂ from ambient air (~420 ppm) using either liquid solvent systems (Carbon Engineering / Oxy: aqueous KOH contact towers → CaCO₃ calcination, ~300–500 USD/tonne CO₂ today) or solid sorbent systems (Climeworks: amine-functionalised filters, temperature-vacuum swing desorption, ~1,000 USD/tonne at Mammoth plant, 36,000 tonne/yr nameplate). Heirloom uses accelerated mineral carbonation (limestone cycling) targeting lower capex. Energy intensity is the binding constraint: ~1,500–2,000 kWh/tonne CO₂ for thermal+electrical loads. Learning-curve targets aim for sub-200 USD/tonne by 2035, contingent on cheap low-carbon heat and scale.

Competitive landscape

Competing removal pathways: BECCS (bioenergy + CCS, land-constrained), enhanced weathering (olivine/basalt, slower but cheap at scale), ocean alkalinity enhancement (early-stage), reforestation (non-permanent). Within engineered DAC, liquid vs. solid sorbent is the main fork. Point-source industrial capture (~50–100 USD/tonne) undercuts DAC on cost but requires co-location with emitters.

Companies using

Connected ideas

Sources

Frontier (open questions)

• To be added.