Carbon capture technology encompasses a suite of methods designed to remove carbon dioxide from industrial emissions or directly from the atmosphere, then store it permanently or convert it into useful products. As the urgency of addressing climate change intensifies, these technologies have moved from laboratory curiosities to large-scale industrial deployments backed by billions in government incentives and private investment. Understanding how carbon capture works, from the molecular chemistry of CO2 absorption to the geology of underground storage, reveals both its promise and its limitations as a climate solution.
Point-Source Carbon Capture
The most mature application of carbon capture targets large industrial emission sources, power plants, cement factories, steel mills, and chemical facilities, where CO2 concentrations in flue gas range from 4-30%, far higher than the 0.04% in ambient air. This concentration advantage makes point-source capture significantly more energy-efficient and cost-effective than direct air capture.
Post-combustion capture using amine solvents remains the dominant technology. Flue gas is passed through an absorber column where it contacts a liquid amine solution, typically monoethanolamine (MEA) or advanced formulations like piperazine blends. The amine reacts with CO2 through a reversible chemical reaction, selectively binding it while allowing nitrogen, oxygen, and other gases to pass through. The CO2-rich solvent is then heated in a stripper column to approximately 120°C, releasing concentrated CO2 and regenerating the solvent for reuse.
The energy required for solvent regeneration, known as the regeneration penalty, is the primary cost driver, consuming 25-40% of a power plant’s output. Advanced solvents with lower regeneration energy requirements, including sterically hindered amines, ionic liquids, and aqueous ammonia, are being developed to reduce this penalty. Solid sorbent systems using metal-organic frameworks (MOFs), zeolites, or functionalized silica offer potential advantages including lower energy requirements and faster cycling.
Membrane-based separation offers a fundamentally different approach. Polymer or ceramic membranes selectively allow CO2 to permeate while retaining other gases, driven by pressure or concentration gradients. Membrane systems are compact, have no chemical consumption, and require less energy than solvent systems for moderate capture rates. Nanomaterial advances in membrane technology, including graphene oxide, carbon nanotubes, and mixed-matrix membranes, are dramatically improving selectivity and permeability.
Direct Air Capture (DAC)
Direct air capture technology removes CO2 directly from ambient air, regardless of where it was emitted. This flexibility enables DAC facilities to be sited near optimal storage locations or clean energy sources rather than at emission points. However, capturing CO2 at atmospheric concentrations (approximately 425 ppm) is thermodynamically far more challenging than capturing it from concentrated flue gas.
Two main DAC approaches have reached commercial demonstration. Solid sorbent systems, like those developed by Climeworks, pass air through solid filter materials that chemically bind CO2 at ambient temperatures. The filters are then heated to 80-120°C to release concentrated CO2. Liquid solvent systems, pioneered by Carbon Engineering (now part of Occidental Petroleum) in British Columbia, contact air with a potassium hydroxide solution in large contactor structures. The CO2-enriched solution undergoes a series of chemical transformations, causticization, calcination, and slaking, to produce concentrated CO2 and regenerate the capture solution.
Current DAC costs range from $250-600 per tonne of CO2, but are falling rapidly with technology improvements and manufacturing scale. The US Department of Energy’s Carbon Negative Shot initiative targets $100 per tonne, a level that would make DAC competitive with many emission reduction alternatives. Scaling DAC to climate-relevant levels, millions of tonnes per year, requires abundant clean energy, massive capital investment, and continued innovation in sorbent materials and process engineering.
Geological Carbon Storage
Once captured, CO2 must be permanently isolated from the atmosphere. Geological sequestration, injecting compressed CO2 into deep underground rock formations, is the most mature and scalable storage approach. At depths exceeding 800 meters, CO2 reaches a supercritical state where it is dense like a liquid but flows like a gas, enabling efficient injection and storage in pore spaces within sedimentary rock.
Four trapping mechanisms ensure long-term storage security. Structural trapping below impermeable caprock (like the seal above an oil reservoir) provides immediate containment. Residual trapping locks CO2 in pore spaces through capillary forces as it migrates through rock. Solubility trapping dissolves CO2 in formation water over centuries, forming a weak carbonic acid. Mineral trapping, the most permanent mechanism, converts dissolved CO2 into stable carbonate minerals through reaction with calcium and magnesium in the rock, essentially turning CO2 to stone over thousands of years.
Global geological storage capacity is vast, estimated at 2,000-20,000 gigatonnes of CO2, sufficient for centuries of storage at any foreseeable capture rate. Deep saline aquifers provide the largest capacity, followed by depleted oil and gas reservoirs and unmineable coal seams. Canada’s Western Canadian Sedimentary Basin offers exceptional storage potential, with extensive geological characterization from decades of petroleum exploration providing detailed knowledge of subsurface conditions.
Carbon Utilization Pathways
Carbon capture and utilization (CCU) converts captured CO2 into commercially valuable products, potentially improving the economics of capture while sequestering carbon in long-lived products. Mineral carbonation reacts CO2 with calcium or magnesium silicates to form stable carbonates, essentially accelerating the natural weathering process that removes CO2 from the atmosphere over geological timescales.
CarbonCure Technologies, a Canadian company based in Halifax, Nova Scotia, injects captured CO2 into fresh concrete during mixing. The CO2 mineralizes into calcium carbonate nanoparticles that permanently sequester the carbon while actually strengthening the concrete, allowing cement content to be reduced. This dual benefit, carbon storage plus material efficiency, has made CarbonCure’s technology one of the most commercially successful carbon utilization approaches, deployed in hundreds of concrete plants across North America.
Synthetic fuels produced by combining captured CO2 with green hydrogen offer a pathway to decarbonize aviation, shipping, and other transportation modes that are difficult to electrify with batteries. While energy-intensive, these e-fuels are carbon-neutral in operation since the CO2 released during combustion was previously captured from the atmosphere.
Real-World Carbon Capture Projects
Several large-scale projects demonstrate carbon capture at commercial scale. The Sleipner project in Norway has safely stored over 20 million tonnes of CO2 in a subsea saline aquifer since 1996, the world’s first dedicated geological storage operation. The Quest project at Shell’s Scotford Upgrader near Edmonton, Alberta has captured and stored over 8 million tonnes of CO2 from hydrogen production since 2015.
SaskPower’s Boundary Dam facility in Saskatchewan was the world’s first coal-fired power plant equipped with post-combustion carbon capture, though it has struggled to meet capture targets and has faced scrutiny over cost overruns. The Alberta Carbon Trunk Line, a 240-kilometer pipeline connecting industrial emitters near Edmonton to depleted oil reservoirs in central Alberta, provides shared infrastructure that reduces costs for individual capture projects.
Iceland’s Orca and Mammoth DAC plants, operated by Climeworks, combine direct air capture with mineralization in basaltic rock, where CO2 reacts with minerals to form solid carbonates within approximately two years. This approach combines permanent storage with a geological setting that accelerates natural mineralization.
Economics and Policy Drivers
The economic viability of carbon capture depends heavily on policy support. Canada’s rising federal carbon price (reaching $170 per tonne by 2030) creates growing financial incentive for industrial emitters to capture CO2 rather than pay the carbon charge. The federal Investment Tax Credit for CCUS covers 37.5-60% of eligible capital costs, making major projects economically viable. Alberta’s Technology Innovation and Emissions Reduction (TIER) system provides additional incentive through compliance credit generation.
In the United States, the Inflation Reduction Act’s enhanced 45Q tax credits, $85 per tonne for geological storage, $180 per tonne for direct air capture with storage, have triggered a wave of project announcements. Global investment in carbon capture is projected to exceed $100 billion by 2030, driven by climate policy, corporate net-zero commitments, and growing recognition of carbon capture’s role in industrial decarbonization.
Where Carbon Capture Fits
Carbon capture is not a substitute for renewable energy deployment and energy efficiency, it is a complement for emissions that are difficult or impossible to eliminate through electrification alone. Cement production, steel manufacturing, chemical processes, and long-distance transportation all have emissions profiles that benefit from carbon capture. DAC addresses legacy emissions already in the atmosphere. Together with aggressive deployment of clean energy technologies, electrified transport, and AI-optimized industrial processes, carbon capture completes the toolkit for achieving net-zero emissions.
