Carbon capture and storage: Technology, economics and climate role

Overview

Carbon capture and storage (CCS) is a process by which carbon dioxide (CO2) from industrial installations or natural sources is separated before it is released into the atmosphere, then transported to a long-term storage location. The CO2 is captured from a large point source, such as a natural gas processing plant and is typically stored in a deep geological formation. Around 80% of the CO2 captured annually is used for enhanced oil recovery (EOR), a process by which CO2 is injected into partially depleted oil reservoirs in order to extract more oil and then is largely left underground. Since EOR utilizes the CO2 in addition to storing it, CCS is also known as carbon capture, utilization, and storage (CCUS).

Distinction from Direct Air Capture

CCS primarily targets large point sources of emissions, such as natural gas processing plants, where the CO2 concentration is relatively high and the stream is easier to isolate compared to the ambient atmosphere. This contrasts with direct air capture (DAC), which extracts CO2 directly from the ambient air, a process that typically requires more energy due to the lower concentration of CO2 in the atmosphere. While both technologies aim to reduce atmospheric CO2 levels, CCS is currently the more established method for industrial-scale decarbonization, leveraging existing infrastructure for capture and transport.

Global Deployment Statistics

As of the latest data, there are 44 operational CCS plants globally, capturing approximately 0.1% of total global CO2 emissions. This deployment reflects the gradual integration of CCS into the energy sector, with a significant portion of captured CO2 being utilized for enhanced oil recovery (EOR). The widespread adoption of CCS is seen as a critical component in achieving global climate goals, particularly for hard-to-abate sectors such as cement production, steel manufacturing, and natural gas processing. The operational status of these plants indicates a growing commitment to scaling up CCS technology to meet future emission reduction targets.

How does carbon capture technology work?

Carbon capture technology separates carbon dioxide (CO2) from industrial emissions or natural sources before atmospheric release, enabling transport to deep geological formations for long-term storage. The process typically targets large point sources, such as natural gas processing plants, where CO2 is extracted and subsequently injected into partially depleted oil reservoirs for enhanced oil recovery (EOR). Approximately 80% of annually captured CO2 is utilized in this manner, a practice that has led to the broader terminology of carbon capture, utilization, and storage (CCUS).

Primary Capture Methods

Three principal technological approaches facilitate CO2 separation: post-combustion, pre-combustion, and oxy-fuel combustion. Each method differs in the timing of separation relative to fuel oxidation and the chemical mechanisms employed to isolate the gas stream.

Post-combustion capture is particularly relevant for retrofitting existing infrastructure, as it allows for the separation of CO2 from the nitrogen-dominated flue gas using amine-based solvents. Pre-combustion capture involves converting fuel into a hydrogen-rich synthesis gas, where carbon monoxide is shifted into CO2, resulting in a higher pressure and concentration of CO2, which simplifies separation. Oxy-fuel combustion isolates CO2 by removing nitrogen from the combustion air, yielding a flue gas that is primarily CO2 and water, which condenses to leave a nearly pure CO2 stream. These technologies enable the integration of CCS into diverse industrial installations, supporting the goal of reducing point-source emissions before they enter the atmosphere. The choice of method depends on the specific fuel type, plant configuration, and the desired purity of the captured CO2 stream for subsequent transport and storage.

Storage methods and enhanced oil recovery

Carbon dioxide captured from industrial point sources is typically transported to deep geological formations for long-term storage. These subsurface reservoirs provide the necessary pressure and temperature conditions to keep the CO2 in a dense phase, ensuring stability over extended periods. The integrity of these formations is critical to preventing the gas from migrating back to the surface or into adjacent layers.

Enhanced oil recovery dominance

A significant portion of the captured CO2 is utilized in the energy sector rather than being stored exclusively for sequestration. Around 80% of the CO2 captured annually is used for enhanced oil recovery (EOR). This process involves injecting CO2 into partially depleted oil reservoirs. The injected gas reduces the viscosity of the remaining crude oil and expands the volume of the fluid, allowing for the extraction of additional oil that would otherwise remain trapped underground. After facilitating oil extraction, the CO2 is largely left underground, effectively combining utilization with storage.

This dual benefit makes EOR a dominant driver in the current deployment of carbon capture technologies, linking fossil fuel production directly to carbon management strategies.

Leakage risks and groundwater contamination

Despite the effectiveness of geological storage, risks remain regarding the long-term integrity of the storage sites. One primary concern is the leakage of CO2 from the deep formation back to the surface. If the caprock or wellbores are not perfectly sealed, the gas can migrate through fractures or fault lines. Another significant risk involves groundwater contamination. When CO2 dissolves in the brine found in aquifers, it forms carbonic acid, which can alter the pH balance of the water. This acidity can leach heavy metals and other minerals from the surrounding rock, potentially affecting the quality of freshwater aquifers located above the storage formation. Monitoring systems are essential to detect these changes and ensure that the stored CO2 remains isolated from the biosphere and hydrological systems.

What are the costs and energy penalties of CCS?

The economic viability of carbon capture and storage (CCS) is heavily influenced by the specific industrial source and the chosen capture technology. According to the provided economic analysis, capture costs can range significantly, from 15to120 per tonne of CO2. This wide variance reflects the difference between point sources with high CO2 concentration, such as natural gas processing plants, and more diffuse sources like coal-fired power generation. The financial burden is not limited to direct capital expenditure; it also includes the operational energy required to separate, compress, and transport the gas.

Energy Penalties in Thermal Power

One of the most critical technical challenges for CCS is the "energy penalty" imposed on the host facility. For coal-fired power plants, integrating CCS systems can increase fuel consumption by 14% to 40%. This means that a significant portion of the energy generated by the plant is consumed by the capture process itself, effectively reducing the net electrical output. For a typical coal plant, this penalty translates to a need for substantially more coal to produce the same amount of net megawatt-hours, directly impacting both the fuel supply chain and the overall efficiency of the infrastructure. This energy overhead is a primary factor in the higher levelized cost of electricity for CCS-equipped plants compared to conventional counterparts.

Comparison with Renewable Energy Costs

When evaluating CCS within the broader energy mix, its costs are often compared against renewable energy sources. While renewables like wind and solar PV have seen dramatic cost reductions, CCS remains a capital-intensive solution, particularly for hard-to-abate sectors and existing thermal infrastructure. The comparison is not always direct, as CCS provides dispatchable power with a lower carbon footprint, whereas renewables are variable. However, the high end of the capture cost spectrum ($120/tonne) can make CCS less competitive than new-build renewable capacity in regions with abundant wind or solar resources, unless carbon pricing or subsidies are applied. The integration of CCS into natural gas processing for enhanced oil recovery (EOR) offers a different economic model, where the stored CO2 helps extract additional oil, partially offsetting the capture and transport expenses.

Role in climate change mitigation

Carbon capture and storage (CCS) is recognized by major international energy bodies as a critical technology for achieving global climate goals, particularly in sectors where direct electrification is challenging. The Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA) highlight the role of CCS in mitigating emissions from heavy industry, such as cement and steel production, and in the production of low-carbon hydrogen. These sectors often rely on process emissions that are difficult to abate solely through renewable energy integration, making CCS a complementary strategy to wind and solar power expansion.

Industrial Applications and Hydrogen Production

In heavy industry, CCS allows for the separation of carbon dioxide (CO2) from large point sources before release into the atmosphere. This capability is essential for decarbonizing industries where thermal energy and chemical processes generate significant CO2 outputs. The IEA emphasizes that without CCS, the cost of abating emissions in these sectors would be substantially higher, potentially hindering the transition to a net-zero economy. Similarly, CCS plays a pivotal role in hydrogen production, particularly for "blue hydrogen," where natural gas is reformed and the resulting CO2 is captured and stored, offering a bridge fuel option as renewable energy infrastructure scales up.

Bioenergy with Carbon Capture and Storage (BECCS)

Bioenergy with Carbon Capture and Storage (BECCS) is a specific application of CCS technology that combines bioenergy production with carbon capture. In this process, CO2 is captured from bioenergy sources, such as biomass power plants, and stored in deep geological formations. BECCS is notable for its potential to achieve negative emissions, meaning it can remove more CO2 from the atmosphere than it emits. This characteristic makes BECCS a valuable tool in climate mitigation strategies, as it can offset residual emissions from hard-to-abate sectors. The IPCC has identified BECCS as a key technology in many pathways to limit global warming to 1.5°C or 2°C above pre-industrial levels, underscoring its importance in the broader climate change mitigation portfolio.

Complementarity with Renewables

While renewable energy sources like wind and solar are central to the energy transition, they do not address all emission sources. CCS complements renewables by providing a solution for emissions that are less amenable to electrification. This synergy is crucial for a diversified and resilient energy system. The operational status of CCS, with projects commissioned as early as 1996, demonstrates its viability and ongoing development. As the global energy landscape evolves, the integration of CCS with renewable energy and other mitigation strategies will be essential for achieving long-term climate objectives.

Political debate and environmental justice

The integration of carbon capture and storage into global energy infrastructure is frequently contested within political and environmental justice frameworks. Critics argue that large-scale CCS deployment may entrench fossil fuel dependence, potentially delaying the transition to renewable energy sources by extending the operational lifespan of coal and natural gas plants. This perspective contrasts with proponents who view CCS as a necessary bridge technology, particularly for hard-to-abate industrial sectors. The debate is further complicated by regulatory definitions, such as those within the UNFCCC, which distinguish between 'abated' and 'unabated' emissions. These classifications influence how nations report their progress toward climate goals, often leading to political friction over what constitutes genuine decarbonization versus temporary mitigation.

Social Impacts and Environmental Justice

Beyond macroeconomic and regulatory debates, CCS projects face significant scrutiny regarding their social impacts on local communities. The storage phase typically involves injecting CO2 into deep geological formations, a process that can affect land use and local water resources. Communities situated near storage sites often raise concerns about potential leakage, land subsidence, and the long-term stewardship of the stored carbon. Environmental justice advocates emphasize that the burdens of CCS infrastructure—such as pipeline routes and storage reservoirs—are not always distributed equitably, sometimes disproportionately affecting indigenous or rural populations. These social dynamics are critical in determining the social license to operate for CCS facilities, as local opposition can delay or even halt projects that are technically viable. The balance between global climate benefits and local community impacts remains a central challenge in the political discourse surrounding CCS implementation.

Government programs and policy support

Government intervention is critical for scaling CCS, primarily through tax credits and regulatory frameworks. In the United States, the Inflation Reduction Act (IRA) significantly expanded the 45Q tax credit, providing incentives for both geological storage and utilization of CO2 (US Department of Energy). This policy aims to bridge the cost gap between conventional capture and market prices. Canada has implemented a federal carbon tax and established the Canada Carbon Capture and Storage Tax Credit to support projects in Alberta and Saskatchewan. Norway operates one of the world’s largest CCS initiatives, the Northern Lights project, supported by the Carbon Capture and Storage Fund and the CO2 tax, leveraging its North Sea geological formations. Denmark is advancing the Port of Aarhus CCS hub, supported by national legislation and public-private partnerships to decarbonize industrial clusters. The United Kingdom has launched the Great British Energy plan and Contracts for Difference (CfD) auctions to support CCUS clusters in the Humber and North West regions, aiming to integrate CCS into its net-zero pathway (UK Department for Business, Energy & Industrial Strategy).

These national programs reflect a global trend toward treating CO2 as a commodity requiring infrastructure investment. The US 45Q credit has been pivotal in attracting private capital, while European nations focus on hub-and-spoke models to aggregate emissions from multiple industrial sources. Norway’s approach emphasizes the use of depleted oil and gas fields, aligning with its energy sector expertise. Denmark’s strategy integrates CCS with port infrastructure, facilitating transport and storage. The UK’s CfD mechanism provides long-term revenue certainty for developers, mitigating financial risks. These diverse policy approaches highlight the need for tailored solutions based on regional geological and economic conditions. International cooperation and harmonized standards are emerging as key factors in accelerating global CCS deployment.

See also

• IPCC Sixth Assessment Report: Structure and scope
• Wave energy converter control by wave prediction and dynamic programming
• Nuclear reactor pressure vessel: Materials, radiation damage, and design
• Offshore wind farm layout optimization
• Landfill gas extraction system

References

1. "Carbon capture and storage" on English Wikipedia
2. Carbon Capture, Utilisation and Storage
3. IPCC Special Report on Carbon Dioxide Capture and Storage
4. Carbon Dioxide Capture and Storage
5. Global CCS Institute