Carbon Capture

Carbon capture and storage (CCS) refers to a collection of technologies that can help address climate change by reducing carbon dioxide (CO₂) emissions. The idea behind CCS is to capture the climate-warming CO₂ generated by burning fossil fuels before it is released to the atmosphere. The question is then: What to do with the captured CO₂? Most CCS strategies call for the injection of CO₂ deep underground. This forms a “closed loop”, where the carbon is extracted from the Earth as fossil fuels and then is returned to the Earth as CO₂.

How does CCS work?

Today, CCS projects are storing over 50 million tons of CO₂ every year¹: about the amount emitted by a small country like Greece or Peru.² Capture generally takes place at large stationary sources of CO₂, like power plants. Most current carbon capture projects use a liquid to chemically remove the CO₂ before it goes out the smokestack, but several new capture processes are under development.

The captured CO₂ gas is then compressed so it becomes liquid-like and transported to a storage site, generally through a pipeline. Once at the storage site, the CO₂ is pumped more than 2,500 feet down wells into geological formations like used-up oil and gas reservoirs, as well as formations that contain unusable, salty water.

The storage challenge

Choosing the right place to store captured CO₂ is important. In the wrong geology, CO₂ could escape back to the surface, or the injection process could cause earthquakes. Geologists look for sites with porous rock that large quantities of CO₂ can seep into, with a solid “cap rock” above, and where there are no nearby fault lines.

There is no shortage of sites like this, even if we were to use vastly more CCS than we do today. But care must be taken in both injecting and transporting CO₂ to minimize risks.

Fortunately, we have a lot of experience with similar challenges. The oil and gas industry maintains millions of miles of pipelines and injects hundreds of billions of gallons of wastewater into the earth each year, a scale that dwarfs CCS today. And unlike oil and gas, CO₂ is not toxic or flammable.

Carbon capture economics

Carbon capture has been successfully demonstrated in many industries that produce CO₂, including coal power, steel and cement manufacturing, and production of ammonia, ethanol, and other chemicals.¹ But simple economics has kept CCS from widespread use. In any industry, adding CCS is an extra cost, and generally a substantial one: In a coal or gas power plant, it has been estimated to as much as double the cost of electricity. While costs may fall with experience, they will not fall to zero.

This means CCS can only compete with government intervention. That could take the form of subsidies for CCS, a carbon tax that charges polluters for the CO₂ they put into the atmosphere, or legal limits on how much CO₂ industries can emit. In effect, CCS will only be used to the extent we are willing to pay to prevent further climate change.

Where and how CCS might be most useful is hard to predict. In some industries, like cement, CCS is one of the only plausible options for dealing with CO₂ emissions. In other sectors, CCS must compete with other mature technologies. Solar and wind power, for example, are plainly cheaper sources of clean electricity than coal or gas with CCS. Yet even here, one can imagine CCS filling a crucial niche. Some other power source must pick up the slack when weather conditions are poor for solar and wind. In the United States today, that is typically gas; in the future, it may be gas with carbon capture.

Capturing CO₂ from the air

There has also been considerable interest in using CCS technologies to remove CO₂ from the atmosphere, reversing some of the damage we have done to the climate. One option is bioenergy with CCS (BECCS), where biomass (like wood or grasses) removes CO₂ from the air through photosynthesis as it grows. The biomass is then harvested and burned in a power plant to produce energy, with the CO₂ being captured and stored.

Another option is called direct air capture (DAC). In a typical DAC plant, huge fans funnel air into machines where CO₂ is removed using a chemical process. However, the concentration of CO₂ in the air is about 300 times less than in a smokestack, making it much less efficient to capture. Because of this, DAC uses a great deal of energy and is quite expensive today.

Our readers have sent in many questions about carbon capture and storage. You can read some of these questions and their answers below:

• How efficient is carbon capture?
• If a fossil fuel plant uses carbon capture, what percent of the energy it makes goes to the CCS equipment?
• What is the risk that captured CO₂ will escape again?
• Could pumping CO₂ underground have the same negative impacts as fracking?
• Are there risks to transporting CO₂ in pipelines?
• How much is captured CO₂ worth?

Updated August 8, 2025.