How Carbon Capture Works: Technology to Remove CO2

Capturing Carbon Before It Reaches the Atmosphere

Carbon capture and storage (CCS) encompasses technologies that capture carbon dioxide emissions from industrial sources or directly from the atmosphere, transport the CO2, and store it permanently underground in geological formations. As the world struggles to meet Paris Agreement targets of limiting warming to 1.5–2°C, CCS is increasingly recognized as a necessary component of decarbonization strategies — particularly for hard-to-abate sectors like cement, steel, and chemical manufacturing where emissions cannot easily be eliminated through electrification alone. The IPCC estimates that achieving net-zero by 2050 will require capturing 5–10 gigatons of CO2 annually.

Three Approaches to Carbon Capture

Post-Combustion Capture

The most mature and widely deployed method uses chemical solvents (typically amine-based solutions like MEA — monoethanolamine) to absorb CO2 from exhaust gases:

• Absorption — Flue gas passes through a tower where amines chemically bond with CO2
• Stripping — The CO2-rich solvent is heated to 120–150°C, releasing concentrated CO2
• Compression — Purified CO2 is compressed to supercritical state (>74 bar) for transport
• Solvent recycling — Regenerated amine returns to the absorber for reuse

This process captures 85–95% of CO2 but requires significant energy (15–30% of a power plant's output), known as the "energy penalty."

Direct Air Capture (DAC)

DAC is more challenging because atmospheric CO2 concentration (420 ppm) is 100–300 times lower than in flue gas, requiring processing enormous volumes of air:

• Solid sorbent systems — Air passes over solid materials that bind CO2 at ambient temperature; heat releases it (e.g., Climeworks technology)
• Liquid solvent systems — Air contacts a potassium hydroxide solution that absorbs CO2; high-temperature calcination releases concentrated CO2 (e.g., Carbon Engineering/Occidental)

Despite higher costs, DAC can be located anywhere and addresses legacy emissions already in the atmosphere. Climeworks' Orca plant in Iceland captures 4,000 tons/year; its Mammoth facility (2024) targets 36,000 tons/year.

CO2 Transport and Storage

Current Status and Challenges

As of 2024, approximately 40 commercial CCS facilities operate worldwide, capturing about 45 million tons of CO2 annually — less than 0.1% of global emissions. Key barriers include:

• High capital costs ($600M–$1B per large facility)
• Energy penalty reduces plant efficiency
• Limited CO2 transport infrastructure (pipelines)
• Public opposition to underground storage (leakage concerns)
• Policy uncertainty and insufficient carbon pricing

The Path Forward

Government policies are accelerating deployment. The U.S. Inflation Reduction Act (2022) increased the 45Q tax credit to $85/ton for geological storage and $180/ton for DAC. The EU Innovation Fund supports large-scale CCS projects. Costs are expected to fall 30–50% by 2030 as technology matures. Most credible net-zero pathways require CCS scaling to 6–10 Gt/year by mid-century — a 100-fold increase from current capacity that demands unprecedented investment and infrastructure buildout.