Key Takeaways
- Carbon capture and storage takes carbon emissions and stores them deep underground.
- Carbon dioxide (CO2) can also be extracted from the air to help reduce greenhouse gas emissions.
- Large-scale CO2 capture can offset fossil-fuel use in heavy industry and power plants.
- Carbon capture is a relatively small part of the potential solution to the climate crisis.
Carbon capture and storage (CCS) is one of many ways governments and industry are trying to reduce global greenhouse gas emissions.
However, carbon capture technology may help tackle global warming without necessarily reducing the use of existing energy sources, particularly fossil fuels.
Every tool is welcome, especially considering that the International Energy Agency (IEA) sees an ever-increasing worldwide demand for energy from a growing global population.
The current growth scenario could mean even more emissions, warming the Earth rapidly and accelerating the climate crisis, whether we utilize CCS or not.
What Is Carbon Capture and Storage (CCS)?
Carbon capture and storage (CCS) involves removing carbon dioxide created by industrial facilities and power generation and putting the CO2 into permanent storage underground.
There are three stages to CCS:
- Capture carbon dioxide spewing from power plants and industrial processes.
- Compress and transport the captured CO 2 to suitable sites.
- Store CO 2 in deep underground geological formations or onshore sites.
Carbon capture and storage aim to mitigate, not stop, the emissions from fossil-fuel power generation and industrial processes like cement, steel, and chemical factories.
Why Do We Need to Capture CO2 Emissions?
Carbon dioxide is a greenhouse gas that absorbs the Earth’s heat and spreads it in all directions. The more CO2 in the Earth’s atmosphere, the warmer our planet becomes. This particular gas is responsible for around two-thirds of all the extra heat caused by all greenhouse gases.
CO2 also dissipates in seas and oceans, raising their acidity levels. This “osteoporosis of the sea” means weaker skeletons and bones for shellfish, damage to coral reefs, and even the creation of toxic fish. The loss of these ecosystems could have enormous ripple effects on the entire planet’s marine life.
Failure to capture carbon dioxide emissions could make the planet warmer and its oceans more acidic, kickstarting climate change disasters.
How Does Carbon Capture and Storage Work?
Power generation, particularly from fossil fuels, releases polluting emissions into the Earth’s atmosphere.
Carbon capture and storage technology scrubs out CO2 emissions before they seep into the sky. It is usually installed at stationary industrial sites where the carbon dioxide is generated.
Pre-combustion CCS removes CO2 before burning oil or natural gas at power plants. A gasification process separates the CO2, methane, and hydrogen—all of which can be used later as fuels—before the original fossil fuel is burned.
Post-combustion CCS uses solvents like ammonia to scrub the CO2 from power plants or industrial gas flues.
Oxyfuel combustion capture is an energy-intensive process in which fossil fuels burn in an almost pure oxygen environment. This O2-rich condition produces only carbon dioxide and water as byproducts but is expensive.
Direct Air Capture (DAC) requires machines to extract CO2 directly from the air anywhere in the world. CO2 concentration levels in the air are much lower than in power plants.
The carbon dioxide captured from these processes is kept in a liquid state and transported to storage sites.
How Does CCS Compare to Direct Air Capture (DAC)?
Direct air capture (DAC) removes carbon dioxide already in the atmosphere. It is energy-intensive as it filters out relatively small amounts of CO2 from the enormous amount of surrounding air.
In contrast, CCS prevents CO2 from being added to the atmosphere. CCS takes the carbon dioxide directly at the source in much denser quantities. So, while CCS also requires energy and adds to an industry’s energy needs, it can extract CO2 more efficiently.
Money-wise, DAC costs about $400-$700 for each tonne of CO 2 removed from the atmosphere. CCS costs $50-$250 for each tonne of CO 2 it prevents from reaching the atmosphere.
Environmentalists may point out that planting more trees instead of deforestation is a natural form of DAC that requires little energy or complex storage issues.
Where Can Carbon Dioxide Be Safely Stored?
Liquid carbon dioxide is transported to storage sites through pipelines, ships, and, occasionally, trucks. The U.S., Europe, the U.K., and Canada have CCS pipeline networks.
The favored storage sites are these typical deep geological formations:
- Old natural gas reservoirs or oil fields
- Saline formations: rocks with porous spaces surrounded by salty water
- Unmineable coal beds, often deep in the ground
- Mineral storage means mixing captured CO2 with iron, magnesium, or calcium to trap the carbon monoxide in stable rocks for centuries
Many subsurface sites are deep underground, where the high pressure and temperature keep the CO2 in a liquid state. The U.S. Gulf Coast and the North Sea between the U.K. and Norway have been touted as having ample storage space for CO2.
How Can CCS Processes Maximize Energy Use?
Carbon capture and storage technologies present opportunities to energy players. Adopting CCS allows fossil fuel power plants to claim a low-carbon footprint.
Carbon dioxide is valuable for enhanced oil recovery (EOR). CO2 pumped into oil wells helps companies extract hard-to-reach oil. However, the emissions from burning oil soon offset those saved by using CCS.
The CO2 injected into unmineable coal releases usable methane, called coal-bed methane. As with EOR, burning this methane offsets the benefit of storing the carbon dioxide in the first place.
CCS vs. CCUS: What Is Carbon Capture, Utilization and Storage?
Carbon Capture Utilization and Storage/Sequestration (CCUS) sees captured carbon re-used in industrial processes.
Scientists are trying to convert CO2 into helpful industrial materials like concrete, plastics, or even baking soda. Carbon dioxide could grow algae or bacteria, which, in turn, can become biofuels, animal feeds, or fertilizers.
Another potential branch for CO2 is bioenergy, which creates a negative emissions circle. Natural materials like wood or grass are biomasses that remove CO2 from the atmosphere through photosynthesis. Once mature, they can be cut and then burned for power generation. The carbon from that burning can be stored. This is considered a negative emission because it takes CO2 from the atmosphere and stores it underground.
Carbon Capture Utilization and Storage/Sequestration (CCUS) technologies can also contribute to hydrogen production. Methane from unmineable coal beds is coupled with CCS carbon to create hydrogen that can power vehicles or create electricity.
Tests are also ongoing to turn CO2 into fuels that could be burned, like hydrogen or methane, for power generation or to power fuel cells. Feasibility studies continue.
Where Is Carbon Storage Being Used?
There are almost 200 large-scale CCS facilities worldwide, many of which are at different stages of development, from planned to working. In 2022, some 244 million tonnes of CO2 were captured by CCS facilities, a drop in the bucket compared to the world’s 37 billion tonnes of CO2 emissions in 2024.
Carbon storage started in earnest in 1972 in Val Verde, Texas. Natural gas processing plants used captured CO2 in enhanced oil recovery (EOR). The Regional Carbon Sequestration Partnership (RCSP) Initiative and the U.S. Department of Energy (DOE) have identified geologic storage sites nationwide.
Elsewhere, CCS projects are already in full swing. Norway has used commercial-scale carbon management tools since 1996 at Sleipner, injecting CO2 into porous sandstone after natural gas processing. Large amounts of CO2 are earmarked for the Humber Zero storage project in the U.K.’s North Sea, a large storage site a mile under the seabed.
What Industries Benefit Most From Carbon Capture and Storage?
Heavy industry and fossil-fuel-power plants benefit the most from carbon capture and storage.
Cement, steel, and chemical industries are energy-hungry and emissions-heavy. CCS and CCUS can help make them low-carbon by capturing carbon emissions, setting up hydrogen production alongside processes, and storing CO2 underground.
What Role Does CCS Play in Achieving Net-Zero Emissions Goals?
Reducing global carbon emissions is crucial to mitigating society’s worst climate change problems. Almost 200 countries have agreed to keep worldwide temperature rises to 2.7 degrees Fahrenheit (1.5 degrees Celsius) by 2050 by achieving net-zero emissions.
Commercial-scale carbon capture is one small way to reduce carbon emissions. CCS removes carbon at its source. Furthermore, direct air capture (DAC) can even remove carbon dioxide directly from the atmosphere.
Indeed, the Intergovernmental Panel on Climate Change (IPCC) claims properly maintained carbon storage sites could trap CO2 for millions of years, with 99% of all injected CO2 retained over the first 1,000 years.
However, environmental groups point out that CCS means a continued reliance on burning fossil fuels rather than moving to more environmentally sustainable fuel sources more quickly.
How Cost-Effective Is CCS Compared to Renewables and Energy Efficiency Measures?
Carbon capture and storage is difficult to compare to renewable energy and energy-efficiency measures.
Firstly, solar and wind power will soon be the cheapest source of electricity generation. Secondly, global energy-efficiency measures could reduce total power demand by 13%, equivalent to the emissions of 1,170 coal-fired power stations, and double the U.S. annual electricity usage. These are both part of an energy transition to cleaner and leaner energy production, moving from fossil fuels to renewables.
By contrast, carbon capture deals with emissions at the source, particularly for industrial processes that cannot avoid emissions. This includes sectors like cement. According to the IEA, cement production costs would rise 10% if CCS technology was incorporated at large-scale production sites.
To make an omelette, you have to break eggs. Some CCS projects require energy—often created from fossil fuels—to function. This means CCS creates two measurables:
- Captured CO2, which is the total CO2 emitted at a power plant and by the CCS project
- Avoided CO2 is the difference between the total CO2 emitted and saved. This avoided CO2 counts as emissions reductions.
Therefore, carbon capture and storage can be emissions- and cost-effective, but every project requires a feasibility study. Reforestation is a nature-led alternative to carbon storage.
What Are the Biggest Challenges Facing Carbon Capture and Storage?
The biggest challenges facing carbon capture and storage include:
- Requirement for more studies into its effectiveness and safety
- Leakage of carbon dioxide from storage sites into oceans and groundwater, contaminating them
- High cost, plus government subsidies to attract investment
- Scalability: Is there enough storage capacity?
- Safety and technical difficulties, particularly when transporting CO2 across large distances and integrating CCS with existing infrastructure
- CO2 mixed with water is corrosive, especially to pipelines
- Monitoring and controlling large amounts of CO2 once underground, including spotting leaks and reactions after local seismic activity
- Injecting carbon underground might increase the likelihood of localized tremors or earthquakes
What Next for Carbon Capture and Storage?
Carbon capture and storage (CCS) has existed since the 1970s, first used to extract extra oil from reservoirs. As technology, fossil fuel use, and climate change inexorably advanced, so did the possibilities for CCS.
Fortunately, carbon dioxide can be removed directly at source, such as a power plant, or taken directly from the air (DAC). We can then store this captured CO2 in deep underground geological formations, such as oil and natural gas reservoirs, including under the sea.
However, the process is costly. But with renewable energy sources due to become the most efficient way to produce electricity, CCS helps clean up the polluting industries before emissions hit the atmosphere.
Issues about leakage, safety, and long-term consequences abound. But we seem incapable of putting the horse before the cart, emissions-wise. So, faced with our inability to reduce greenhouse gas emissions, CCS may provide some mitigation to the climate crisis, and carbon capture and storage may step to the forefront of the global warming battle.
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