What Is Carbon Capture and Storage?

Carbon capture and storage, or CCS, is a set of technologies that capture carbon dioxide emissions from industrial facilities or power plants, transport the captured CO2, and inject it into deep geological formations for permanent storage. The goal is to prevent large quantities of carbon dioxide from entering the atmosphere while allowing continued use of fossil fuels or industrial processes that inherently produce CO2.

CCS is distinct from carbon dioxide removal, which pulls CO2 directly from the ambient atmosphere. CCS targets point sources where CO2 concentrations are high, making capture more technically straightforward and less energy-intensive than direct air capture.

The Three Steps of CCS

The capture step separates CO2 from the other gases produced by industrial processes or power generation. Three main approaches exist. Post-combustion capture uses chemical solvents to absorb CO2 from flue gas after fuel is burned. Pre-combustion capture converts fuel into hydrogen and CO2 before combustion, capturing the CO2 and burning the hydrogen. Oxy-fuel combustion burns fuel in pure oxygen rather than air, producing a flue gas that is almost entirely CO2 and water vapor, making separation straightforward.

Transport moves the captured CO2 from the capture facility to the storage site. Pipelines are the primary transport method for large volumes. The United States already has over 5,000 miles of CO2 pipelines, primarily serving enhanced oil recovery operations in Texas and the Permian Basin. For smaller volumes or locations far from pipeline infrastructure, CO2 can be transported by truck, rail, or ship.

Storage involves injecting CO2 into deep geological formations where it is trapped permanently. The most common storage formations are deep saline aquifers, porous rock formations saturated with brine that lie more than 800 meters below the surface. At these depths, pressure keeps the CO2 in a dense, liquid-like state. Depleted oil and gas reservoirs are also used, with the advantage that their geological properties are already well characterized from decades of hydrocarbon extraction.

Current CCS Projects and Scale

Global operational CCS capacity is approximately 50 million tonnes of CO2 per year, a figure that represents less than 0.15% of annual global emissions. The largest operating CCS projects include the Quest project in Alberta, which captures CO2 from oil sands processing, and the Gorgon project in Australia, which captures CO2 from natural gas production.

In the United States, the 45Q tax credit provides up to $85 per tonne of CO2 permanently stored in geological formations, making it one of the most generous CCS incentives in the world. This credit has spurred a wave of new project announcements, particularly in the Gulf Coast region where geological storage capacity is abundant and existing pipeline infrastructure can be leveraged.

Costs and Economic Challenges

The cost of CCS varies widely depending on the CO2 source. Capture from high-concentration industrial sources like ethanol production or natural gas processing can cost as little as $15 to $30 per tonne. Capture from power plant flue gas, where CO2 concentrations are lower, costs $40 to $120 per tonne. Direct air capture, which must extract CO2 from ambient air at a concentration of only 420 parts per million, costs $250 to $600 per tonne.

The energy penalty is another challenge. Running a carbon capture system on a power plant typically consumes 15% to 30% of the plant’s output, reducing its net electricity production and increasing the effective cost of generation.

The Debate Around CCS

CCS occupies a contentious position in energy policy. Proponents argue that certain industrial emissions, such as those from cement and steel production, cannot be eliminated through electrification or fuel switching alone, making CCS essential for deep decarbonization. They also point to the role CCS can play in producing blue hydrogen from natural gas.

Critics contend that CCS extends the life of fossil fuel infrastructure, diverts investment from renewable energy, and has a poor track record of delivering projects on time and on budget. Environmental groups have raised concerns about the safety and permanence of geological CO2 storage and the environmental justice implications of building new pipeline infrastructure through communities.