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What is carbon capture and storage?

April 9, 2024

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Carbon Capture and Storage (CCS) is a pivotal technology designed to combat climate change by reducing the amount of carbon dioxide (CO2) that is emitted into the atmosphere from industrial and power generation activities. It encompasses three main stages: capturing CO2 from emission sources, transporting this CO2, and then storing it underground in geological formations to prevent it from contributing to atmospheric greenhouse gas levels.

The process involves several techniques for capturing CO2, including post-combustion capture, pre-combustion capture, oxyfuel combustion, and direct air capture. Post-combustion capture involves using solvents to separate CO2 from flue gases after fossil fuels have been burned. Pre-combustion capture involves processing fuels before burning them to separate CO2. Oxyfuel combustion involves burning fossil fuels in pure oxygen instead of air, resulting in a flue gas composed primarily of CO2 and water vapor, which is easier to separate. Direct air capture, while not directly related to preventing emissions at their source, involves removing CO2 directly from the atmosphere.

After capture, CO2 is compressed and transported, usually via pipelines, to storage sites. These sites can include depleted oil and gas fields or deep saline aquifers, where the CO2 can be stored safely and permanently.

There’s also an aspect of carbon capture known as Carbon Capture, Utilization, and Storage (CCUS), which goes a step further by finding ways to use the captured CO2, for example, in enhanced oil recovery, producing chemicals, or making building materials like concrete.

CCS is recognized for its potential to significantly reduce greenhouse gas emissions, especially from large stationary sources like power plants and industrial facilities. As of the reports, CCS projects are storing nearly 45 million tons of CO2 annually, equating to the emissions from about 10 million passenger cars. However, widespread adoption faces challenges, including high costs and technological complexities (Britannica) (MIT Climate Portal).

Table of Contents

What is CCS?

Carbon Capture and Storage (CCS) is a technology aimed at reducing global carbon dioxide (CO2) emissions, which are a major contributor to climate change. CCS involves three key steps:

Capture: This first step involves capturing CO2 produced by large sources, such as power plants or industrial processes, before it’s released into the atmosphere. Various technologies can be used for capturing CO2, including post-combustion, pre-combustion, and oxy-fuel combustion methods.
Transport: Once captured, the CO2 needs to be transported to a storage site. This is typically done via pipelines, although it can also be transported in liquid form using ships or trucks, especially over longer distances or to locations where pipelines are not feasible.
Storage: The final step involves storing the captured CO2 securely so that it doesn’t enter the atmosphere. The most common method is to inject it deep underground into geological formations, such as depleted oil and gas fields or deep saline aquifers, where it is safely and permanently stored.

CCS is considered a critical technology for achieving global climate goals, as it allows for the reduction of CO2 emissions from the use of fossil fuels in energy generation and industrial processes. It also holds potential for use in conjunction with biomass energy production, creating negative emissions by removing CO2 from the atmosphere.

The technology is already being used in several locations around the world, but its widespread deployment faces challenges, including high costs, technological complexities, and the need for significant infrastructure development【16†source】【16†source】.

How can CCS help prevent global warming?

Carbon Capture and Storage (CCS) can play a significant role in preventing global warming by addressing CO2 emissions in sectors where reduction is challenging and by removing carbon from the atmosphere. It’s essential for achieving net-zero emissions, particularly in the energy sector, where it can:

Reduce Emissions from Existing Energy Assets: CCS can capture CO2 emissions from existing power plants and industrial processes, significantly reducing the immediate impact of these sources on global warming.
Abate Hard-to-Reduce Emissions: Certain industries like cement and steel production have emissions that are difficult or currently impossible to eliminate through other means. CCS offers a solution for capturing these emissions before they reach the atmosphere.
Enable Clean Hydrogen Production: Hydrogen is seen as a clean energy carrier for the future, but its production from fossil fuels emits CO2. CCS can capture these emissions, allowing for the expansion of hydrogen energy in a more sustainable manner.
Remove Atmospheric CO2: Technologies like Direct Air Capture (DAC) can remove CO2 directly from the atmosphere. When combined with CCS, this can help offset emissions from sectors outside the energy system that are difficult to abate.

By 2070, in a scenario aiming for net-zero emissions, CCS is projected to capture significant amounts of CO2 from fossil fuels, industrial processes, bioenergy, and directly from the air. This includes capturing CO2 for clean hydrogen production, which is essential for decarbonizing transport, industry, and buildings, and for producing synthetic aviation fuels. The International Energy Agency (IEA) highlights that CCS, including Bioenergy with Carbon Capture and Storage (BECCS) and DAC, will be crucial in balancing emissions in the energy system and contributing to the global goal of limiting temperature rises, as outlined in the Paris Agreement goals【24†source】【25†source】.

How does CCS actually work?

Carbon Capture and Storage (CCS) is a process designed to reduce carbon dioxide (CO2) emissions from sources like power plants and industrial facilities to combat climate change. Here’s a simplified overview of how CCS works, broken down into its three main components:

1. Capture

The capture phase involves separating CO2 from other gases produced during power generation or industrial processes. This can be achieved through several methods:

Post-Combustion Capture: CO2 is removed from flue gases after combustion. This method is versatile and can be retrofitted to existing facilities. It usually involves the use of solvents that absorb CO2.
Pre-Combustion Capture: In this method, fossil fuels are processed before combustion to produce a mixture of hydrogen and CO2. The CO2 is then separated out. This method is particularly suited for integrated gasification combined cycle (IGCC) plants.
Oxy-Fuel Combustion: This process involves burning fuel in pure oxygen instead of air, leading to flue gases that are primarily CO2 and water vapor, which can then be separated through condensation.

2. Transport

After capture, the CO2 needs to be transported to a storage site. This is most commonly done through pipelines, but it can also be transported in liquid form by ships or trucks for storage sites that are not accessible by pipeline.

3. Storage

The final step is the permanent storage of CO2, deep underground. Suitable locations include:

Depleted Oil and Gas Fields: These are well-understood geological formations that have already been drilled, making them prime candidates for CO2 storage.
Deep Saline Aquifers: These are porous rock formations filled with saltwater, which can absorb CO2. The CO2 is injected deep underground, where it is eventually mineralized, turning into rock.
Use in Enhanced Oil Recovery (EOR): While not a form of permanent storage, injecting CO2 into oil fields can help recover additional oil, after which the CO2 can be permanently stored underground.

The effectiveness of CCS as a climate change mitigation strategy hinges on its ability to capture a significant portion of CO2 emissions from large point sources and securely store them away from the atmosphere. While the technology is promising and operational at various sites worldwide, scaling it up to the level needed to make a substantial impact on global emissions poses economic, technical, and regulatory challenges. For more detailed information, the International Energy Agency (IEA) and the Intergovernmental Panel on Climate Change (IPCC) provide extensive resources and analyses on CCS technologies and their role in global carbon mitigation efforts.

Where are carbon emissions stored in CCS?

In Carbon Capture and Storage (CCS) processes, the captured carbon dioxide (CO2) emissions are stored in geological formations deep underground. These storage sites are selected based on their ability to securely contain the CO2 for long periods, preventing it from contributing to atmospheric greenhouse gas levels. The primary types of geological formations used for CO2 storage include:

Depleted Oil and Gas Reservoirs: These are layers of porous rock that have previously contained, and been depleted of, oil or gas. Their suitability for storing CO2 is well understood due to the geological knowledge gained from previous drilling operations. They are considered secure because they have naturally contained gas and oil for millions of years.
Deep Saline Formations: These are porous rock layers saturated with saltwater, located deep underground. They are widespread globally and have the potential to store large volumes of CO2. The saline water and overlying rock layers act as a natural seal, keeping the injected CO2 trapped.
Unminable Coal Seams: CO2 can be stored in coal beds that are too deep to be mined. The CO2 gets adsorbed onto the surface of the coal, displacing methane that can be collected and used as an energy source. This method, however, is less common than the others.
Basalt Formations: Basalts are a type of volcanic rock that can react with CO2 to form stable carbonate minerals. This mineralization process effectively locks the CO2 away in solid form, ensuring its permanent storage.

The choice of storage site depends on several factors, including the proximity to the source of CO2, the capacity of the site to hold the CO2, the security of containment, and the cost of transportation and injection. Successful CO2 storage also requires comprehensive monitoring to ensure the integrity of the storage site and the permanent containment of CO2.

By injecting CO2 into these underground geological formations, CCS technology aims to prevent significant amounts of CO2 from reaching the atmosphere, thereby contributing to the mitigation of climate change. The International Energy Agency (IEA) and various environmental research organizations provide extensive resources on the development and implementation of CCS technology, highlighting its importance in achieving global emissions reduction targets.

What is Carbon Capture, Utilisation and Storage (CCUS)? What is the difference between CCUS and CCS?

Carbon Capture, Utilisation and Storage (CCUS) refers to a set of technologies that capture carbon dioxide (CO2) emissions from sources like power plants and industrial processes, to prevent it from entering the atmosphere. Once captured, the CO2 can be either used for other applications or stored underground in geological formations. The utilization aspect of CCUS distinguishes it from CCS (Carbon Capture and Storage) by emphasizing the use of captured CO2 in various applications, such as in enhanced oil recovery (EOR) or the production of certain materials.

The main difference between CCUS and CCS is in the utilization component. While CCS focuses solely on the capture and storage of carbon to mitigate environmental impact, CCUS adds a dimension of using the captured carbon in a way that can generate economic value or further reduce emissions. For instance, captured CO2 can be used to produce synthetic fuels, chemicals, and in other industrial processes where CO2 serves as a raw material.

CCUS is increasingly recognized as a crucial technology in the transition to net-zero emissions. It not only addresses emissions from difficult-to-abate sectors but also plays a role in producing low-carbon hydrogen and removing carbon from the atmosphere. As the world aims for net-zero emissions, technologies that can remove CO2 from the cycle—either by storing it away or by utilizing it—are essential. CCUS’s flexibility and potential to contribute to various aspects of the energy and industrial sectors make it a key pillar in achieving global climate goals【35†source】【37†source】.

Is storing CO₂ as part of CCS safe?

Storing CO2 underground as part of Carbon Capture and Storage (CCS) processes is considered to be safe, assuming rigorous site selection, design, and management practices are adhered to. This assessment is backed by a significant body of research and real-world experience:

Historical Evidence of Natural Gas Storage: Geological formations have naturally trapped and stored natural gas and CO2 for millions of years. This demonstrates the potential for these formations to safely store CO2 over long periods. The United States has also safely injected natural gas into underground formations for storage, utilizing this geological and engineering experience for CO2 storage, a safer, non-combustible gas【45†source】.
Enhanced Oil Recovery (EOR) Practices: For over 40 years, CO2 has been injected underground as part of EOR processes to increase oil production, providing practical evidence that CO2 can be safely stored underground【45†source】.
Large-scale Commercial and Research Projects: Several large-scale commercial and research-related CO2 storage operations in the United States and around the world have demonstrated effective and safe CO2 storage. Notable examples include the Sleipner Project in the North Sea and the Weyburn Project in Saskatchewan, contributing to a wealth of evidence that CO2 storage, when well-managed, is safe【45†source】.
Risk Identification and Mitigation: Safe injection and storage require identifying and quantifying risks, such as CO2 migration out of storage complexes and the potential physical and chemical effects on the subsurface. Research, including the efforts by the National Risk Assessment Partnership (NRAP), is focused on developing technologies and procedures to reduce and mitigate these risks, ensuring the safety of CO2 storage operations【45†source】.
Monitoring and Verification: Continuous monitoring at several large-scale CCS injection projects around the world has shown that CO2 injection is expected to be safe, dispelling myths that CO2 injection is likely to be unsafe due to potential migration to the surface【45†source】.
Safety Demonstrations in Iceland: Projects like CarbFix2 in Iceland have demonstrated the entire CCS cycle, capturing, transporting, and storing CO2 as a mineral by dissolving it in water before injection into basaltic rock, which reacts with carbon to form calcite, significantly reducing the risk of leaks and addressing concerns about seismicity【44†source】.

While CCS presents a potentially major tool in the battle against climate change, public and scientific opinions remain divided, largely due to concerns about the continued use of fossil fuels and the scalability of CCS technologies. However, ongoing research aims to demonstrate the safety and viability of CCS, potentially making it an important part of our future climate strategy【44†source】.

Where is CCS being used already and what’s in development?

Carbon Capture and Storage (CCS) projects are witnessing significant growth and development across various regions, demonstrating the technology’s role in global efforts to mitigate climate change. The Global CCS Institute reported that in 2022, the CO2 capture capacity of all CCS facilities under development increased by 44%, bringing the total capacity of those projects to 244 million tons per annum (mtpa) of CO2. This acceleration is evident with 61 new facilities added to the project pipeline in 2022, culminating in 30 projects in operation, 11 under construction, and 153 in development. This growth is largely concentrated in the Americas, especially North America, buoyed by supportive governmental incentives in the United States and Canada.

In the United States, the Inflation Reduction Act of 2022 is enhancing CCS deployment through improvements to the Internal Revenue Service Section 45Q, along with $369 billion in funding for climate and energy projects. This Act extends the construction start timing to the end of 2032, lowers capture thresholds, and expands transferability, amongst other benefits. Additionally, the US Infrastructure Investment and Jobs Act includes over $12 billion for CCS over the next five years. Canada is also contributing to this momentum with its 2022 federal budget, which introduces an investment tax credit for direct air capture projects and other carbon capture endeavors.

One notable project involves ExxonMobil joining forces with CF Industries and EnLink in a blue ammonia project in Louisiana, aiming to capture and store 2 million metric tons of CO2 starting in 2025【52†source】.

Furthermore, the Global Status of CCS 2022 report highlights the increasing momentum behind CCS worldwide, emphasizing significant progress from countries and companies. The report urges for ambition to translate into urgent, broad, and large-scale action to maintain a livable climate, offering detailed analyses of the global project pipeline, international policy, carbon markets, carbon removals, and the evolution of storage. It also provides regional overviews showcasing the rapid development of CCS across North America, Asia Pacific, Europe, the UK, and the MENA region【53†source】.

These developments underscore the growing recognition of CCS as a critical tool in the fight against global warming, with increased investment and policy support driving its expansion globally.

Where was the first CCS facility?

The world’s first commercial Carbon Capture and Storage (CCS) project is the Sleipner CCS Project in the North Sea, operated by Equinor (formerly Statoil). Launched in 1996, the project captures CO2 from the natural gas produced at the Sleipner gas field and stores it in a deep saline aquifer some 800-1,000 meters below the seabed. Each year, Sleipner prevents approximately 1 million tonnes of CO2 from being released into the atmosphere by storing it underground【57:3†source】.

This pioneering project has been closely monitored and studied to ensure the safety and effectiveness of CO2 storage, providing valuable insights and confidence in the feasibility of CCS as a climate change mitigation technology. The success of Sleipner has paved the way for subsequent CCS projects worldwide, highlighting the potential of this technology to significantly reduce industrial CO2 emissions.

What is carbon capture and storage?

What is CCS?

How can CCS help prevent global warming?