CO2 Removal and Carbon Capture & Storage Technologies: A Comprehensive Overview

The Carbon Capture and Removal Landscape

Carbon Capture & Storage (CCS) and Carbon Dioxide (CO₂ )Removal (CDR) share the goal of slowing the increase in atmospheric CO₂ levels and in the long term even begin to lower them, but they represent two quite different approaches:

CCS prevents new emissions of CO₂ from entering the atmosphere, particularly from hard-to-abate industries where CO₂ emissions are inherent to the manufacturing process rather than just from burning fossil fuels to generate energy.
CDR extracts CO₂ already in the atmosphere to compensate for both unavoidable future emissions and to address legacy emissions - the CO₂ previously put into the air and which will persist for centuries as it cycles slowly between atmosphere, oceans, and biosphere rather than breaking down like other pollutants.
Both technologies are meant to complement, not substitute for, the urgent need to drastically reduce emissions across power generation, industry, and transport.

While we have the technology to capture CO2 from industrial sources and remove it from the air, scaling all of these solutions to meaningfully impact climate change will be about more than just technological advancements. Success will require massive coordination efforts, such as building extensive pipeline networks to transport captured CO2, creating reliable carbon markets based on accurate measurements of what's actually being captured or removed, and finding new ways to fund these long-term infrastructure projects.

Click on any element for more information

Overview: Forestation includes afforestation (planting trees in new areas), reforestation (restoring deforested areas), and forest conservation. These approaches use trees to remove CO₂ from the atmosphere, storing carbon in biomass and soil while supporting biodiversity.
Potential: Forests are complex carbon managers:
Beyond carbon sequestration, forests:
Challenges and Future Research:
Key considerations for expanding forestation:
Research needs:

Overview:Transporting large volumes of CO₂ from capture sites, typically located in industrial areas, to distant geological storage locations will require access to infrastructure such as pipelines, shipping routes, or rail networks.

Pipelines are the most efficient and cost-effective method for large-scale, long-distance CO₂ transport. They can move large volumes continuously with low operating costs. However, pipelines require major upfront capital investments and a guaranteed long-term CO₂ supply to be economical. They also face potential conflicts with landowners over rights-of-way.
Ships offer more flexibility and can be economical for offshore transport over long distances. They have lower initial costs than pipelines but higher operating costs. Ships enable point-to-point transport without fixed infrastructure.
Road and rail transportation are suitable for small-scale, short-distance CO₂ transport. They have low capital costs and offer flexibility but become uneconomical at large scales due to high operating costs and emissions.

Challenges and Areas for Future Research: Improving the safety and reliability of CO₂ transportation systems will be key. Research will potentially enhance pipeline materials and design for greater durability, minimize the risks of leakage, and lower operational costs. Additionally, optimizing the logistics of CO₂ shipping and investigating the potential for offshore storage solutions can expand the reach of CCS networks.

Challenges and Areas for Future Research: Improving the safety and reliability of CO₂ transportation systems will be key. Research will potentially enhance pipeline materials and design for greater durability, minimize the risks of leakage, and lower operational costs. Additionally, optimizing the logistics of CO₂ shipping and investigating the potential for offshore storage solutions can expand the reach of CCS networks.

CDR - Carbon Dioxide Removal

Carbon Dioxide Removal (CDR) aims to remove CO₂ that's already present in the atmosphere (as opposed to Carbon Capture and Storage (CCS) which focuses on capturing carbon dioxide directly from industrial sources before it's released into the atmosphere).
CDR methods vary, including both natural and engineered solutions.
Natural approaches include afforestation and enhanced rock weathering, which aim to accelerate elements of the Earth's natural carbon cycles.
Engineered methods, like Direct Air Capture, use technology to extract CO₂ from the atmosphere and then store it deep underground.

Biochar

Overview: Biochar is a type of charcoal created through pyrolysis, a process that heats organic materials like wood or agricultural waste in a low-oxygen environment. This prevents the material from burning completely but drives off other compounds. The result is a carbon-rich material with an extensive network of tiny pores, giving biochar a very large internal surface area. These pores help biochar retain water, nutrients, and beneficial microbes, potentially improving soil health. Its stable structure allows it to lock carbon away for long periods, acting as a carbon sink.
Potential: Biochar can significantly improve soil fertility, especially in degraded or nutrient-poor soils, potentially reducing the need for chemical fertilizers and irrigation. It can sequester carbon for hundreds or even thousands of years. Beyond carbon storage, biochar has many benefits, such as better water retention, healthier soils, and increased agricultural productivity.
Challenges and Areas for Future Research: Optimizing biochar use requires exploration of how different materials (feedstocks) and production conditions affect its properties and performance. Further research is needed to understand how biochar interacts with different soil types over the long term, particularly regarding its impact on soil health and crop yields. Investigation into how much carbon biochar can actually store in various environments and ways to make its production more efficient and environmentally friendly is also necessary. Additionally, research on proper 'aging' or conditioning of biochar is crucial, as fresh biochar can initially absorb nutrients and potentially reduce their availability to plants.

Forestation

Overview: Forestation includes afforestation (planting trees in new areas), reforestation (restoring deforested areas), and forest conservation. These approaches use trees to remove CO₂ from the atmosphere, storing carbon in biomass and soil while supporting biodiversity.
Potential: Forests are complex carbon managers:
Beyond carbon sequestration, forests:
Challenges and Future Research:
Key considerations for expanding forestation:
Research needs:

Enhanced Rock Weathering (ERW)

Overview: ERW accelerates the natural process of rock weathering where water containing dissolved CO2 forms a weak acid that reacts with silicate rocks, leading to the formation of stable carbonate minerals and locking carbon away for millions of years. This process also releases elements vital to plant growth. By grinding rocks such as basalt into fine particles and dispersing them across land, the natural process of rock weathering is accelerated, speeding it up by tens of thousands of times.
Potential: As well as removing significant amounts of CO₂ from the atmosphere, storing it long-term as carbonate minerals, the release of elements such as potassium and magnesium that can improve soil quality. The process also generates alkaline compounds that may help counteract ocean acidification.
Challenges and Research Areas: Key research focuses include optimizing rock selection, developing efficient methods for large-scale grinding and distribution, and evaluating the effects on soil and water ecosystems, such as the potential release of heavy metals and the effects of soil alkalinization on biodiversity. Priorities also involve improving techniques for measuring amounts of CO₂ removed, and determining ERW's effectiveness in different climates.

Oceanic CO₂ Removal

Overview: Oceanic CO₂ removal techniques aim to enhance the ocean's natural ability to absorb and store CO₂. This includes methods like ocean alkalinization, which adds minerals to increase seawater's capacity to store CO₂, and iron fertilization, which promotes the growth of phytoplankton that absorb CO₂ through photosynthesis.
Potential: The oceans already serve as the planet’s largest carbon sink, absorbing about a quarter of all human-generated CO₂ emissions. By enhancing this process, oceanic CO₂ removal methods could significantly scale up carbon sequestration. Additionally, improving ocean health can enhance marine biodiversity and support ecosystem services like fisheries.
Challenges and Areas for Future Research: Research is needed to better understand the long-term ecological impacts of oceanic CO₂ removal, including potential effects on marine ecosystems and ocean chemistry. Additionally, improving techniques for monitoring and verifying CO₂ sequestration in ocean environments is critical. Regulatory frameworks and public perception also need to be addressed to enable large-scale deployment.

Direct Air Capture (DAC)

Overview: Direct Air Capture (DAC) technology removes CO₂ directly from the atmosphere using large fans that push air through chemical absorbers. These chemicals selectively capture the CO₂ , which is then released through heating, allowing it to be compressed and stored deep underground. DAC’s flexibility comes from its ability to operate independently of specific emission sources, making it a versatile and scalable solution for atmospheric CO₂ removal.
Potential: DAC plants can be located near renewable energy sources and suitable geological storage sites, reducing the need for long-distance CO₂ transport and ensuring a sustainable energy supply. The precise measurement of the CO₂ captured makes DAC highly attractive for carbon markets and offsetting programs. Additionally, DAC requires minimal land space and poses a lower risk of environmental impact compared to some other carbon removal methods.
Challenges and Areas for Future Research: With CO₂ levels in the atmosphere at around just 0.04%, compared to concentrations of up to 30% in industrial flue gases, separating CO₂ in DAC systems is extremely energy-intensive. Enhancing the efficiency of CO₂ capture technology will be key to reducing costs. Identifying optimal locations—especially those with suitable geological storage and abundant renewable energy that isn’t needed to replace fossil fuel usage elsewhere—will also be critical to making DAC commercially viable.

Carbon Sequestration in Natural Sinks

CDR techniques that rely on natural processes lead to carbon being stored in natural sinks.
With forestation, the carbon is sequestered in the biomass of trees and other forest vegetation, as well as in the surrounding soil.
In enhanced rock weathering (ERW), carbon is stored in solid carbonate minerals formed when CO₂ chemically reacts with rocks.
The duration of carbon sequestration will differ greatly between these methods.
With forestation, carbon is stored for the lifespan of the trees, or for as long as it remains in the soil in the form of decaying plant matter.
ERW however results in the conversion of CO₂ into solid carbonate minerals which will be stable for potentially millions of years.

CCS - Carbon Capture and Storage

Carbon capture and storage (CCS) aims to reduce carbon emissions from major sources such as manufacturing facilities and power plants by capturing CO₂ before it enters the atmosphere.

How it works:

Capture: CO₂ is separated from other gases in emissions through methods such as post-combustion (capturing CO₂ from exhaust gases), pre-combustion (removing CO₂ from fuel before it is burned), or oxy-fuel combustion (burning fuel in pure oxygen to create a CO₂-rich gas).
Transportation: The captured CO₂ is transported, typically via pipelines or ships, to a storage site.
Storage: The CO₂ is injected deep underground into geological formations like depleted oil fields or saline aquifers, where it is securely trapped, preventing it from entering the atmosphere.

BECCS (Bioenergy with Carbon Capture and Storage)

Overview: BECCS combines biomass energy production with carbon capture and storage. In this process, biomass like wood or crops is burned for energy, and the resulting CO₂ emissions are captured and stored underground, effectively creating a carbon-negative energy source.
Potential: BECCS is one of the few technologies that can produce energy while actively removing CO₂ from the atmosphere, offering a unique contribution to decarbonization efforts. It provides a reliable source of renewable energy and can be integrated with existing biomass power plants to enhance their sustainability.
Challenges and Areas for Future Research: Key areas for improvement include reducing CO₂ emissions during biomass cultivation, harvesting, and transportation. More research is needed on sustainable land management practices to minimize competition with food production and protect biodiversity. Advancements in carbon capture technology and CO₂ transport infrastructure will also be necessary for large-scale implementation.

Industrial/Point Source Carbon Capture

Overview: Industrial carbon capture involves capturing CO₂ emissions from large point sources such as steel, cement, and chemical plants, as well as power stations. This is typically done by separating CO₂ from other gases in exhaust streams using chemical absorption methods.
Potential: Industrial carbon capture is critical for decarbonizing hard-to-abate sectors, where emissions reductions are otherwise difficult to achieve. It provides a viable solution for industries that rely on high-temperature processes or produce substantial CO₂ emissions.
Challenges and Areas for Future Research: Reducing the energy and cost requirements of capture technologies is a major focus. Additionally, improving the integration of capture systems with existing industrial processes and developing better CO₂ transport and storage infrastructure will help scale up the technology. Advances in retrofitting technologies and materials for capturing CO₂ more efficiently are needed.

Blue Hydrogen

Overview: Blue hydrogen is produced by converting natural gas into hydrogen, with the associated CO₂ emissions captured and stored using carbon capture and storage. It offers a lower-emission alternative to grey hydrogen, which is produced from natural gas without capturing the CO₂ emissions.
Potential: Blue hydrogen could play an important role in decarbonizing sectors like heavy industry and long-haul transport which are difficult to electrify. It is often seen as a transitional solution while green hydrogen, produced using renewable energy, scales up.
Challenges and Areas for Future Research: Challenges include reducing the cost of CCS and addressing methane emissions from natural gas production. Methane, a powerful greenhouse gas, frequently leaks during natural gas extraction and transportation, reducing the climate benefits of blue hydrogen. Research to improve carbon capture efficiency and lower methane emissions is essential to make blue hydrogen more sustainable.

Carbon Hubs and Clusters

Overview: Carbon hubs are the shared transportation and storage infrastructure for captured CO₂ emissions. Clusters refer to groups of industrial facilities located near each other which can share the facilities offered by carbon hubs. Adopting this shared approach will make the disposal of captured CO₂ economically feasible for individual emitters.
Potential: Beyond reducing costs for large-scale CO₂ transportation and storage, this collaborative approach can promote cooperation across all aspects of CCS, including coordination and sharing of expertise between emitters, attracting funding, campaigning for supportive regulations, and building public support.
Challenges and Areas for Future Research: Future improvements will require developing stronger models for industrial collaboration and ensuring reliable, long-term storage sites. Investments in shared infrastructure, such as pipelines and storage facilities, will be crucial for expanding the reach of CCS. Research into establishing the most efficient CO₂ transportation methods over long distances will also play a key role.

Transportation of Captured CO₂

Overview:Transporting large volumes of CO₂ from capture sites, typically located in industrial areas, to distant geological storage locations will require access to infrastructure such as pipelines, shipping routes, or rail networks.

Pipelines are the most efficient and cost-effective method for large-scale, long-distance CO₂ transport. They can move large volumes continuously with low operating costs. However, pipelines require major upfront capital investments and a guaranteed long-term CO₂ supply to be economical. They also face potential conflicts with landowners over rights-of-way.
Ships offer more flexibility and can be economical for offshore transport over long distances. They have lower initial costs than pipelines but higher operating costs. Ships enable point-to-point transport without fixed infrastructure.
Road and rail transportation are suitable for small-scale, short-distance CO₂ transport. They have low capital costs and offer flexibility but become uneconomical at large scales due to high operating costs and emissions.

Challenges and Areas for Future Research: Improving the safety and reliability of CO₂ transportation systems will be key. Research will potentially enhance pipeline materials and design for greater durability, minimize the risks of leakage, and lower operational costs. Additionally, optimizing the logistics of CO₂ shipping and investigating the potential for offshore storage solutions can expand the reach of CCS networks.

Storage of Captured CO₂

Overview: CO₂ storage involves the long-term sequestration of captured CO₂ in underground formations like saline aquifers, which are rock layers filled with salt water, and depleted oil and gas reservoirs, where the oil and gas have already been extracted. These formations offer secure, stable environments for the permanent storage of CO₂.
Potential: Geological storage has the capacity to store vast amounts of CO₂, making it a cornerstone of long-term carbon management strategies. Utilizing existing oil and gas reservoirs can reduce costs and benefit from existing infrastructure and knowledge.
Challenges and Areas for Future Research: Ensuring the long-term stability of storage sites, improving monitoring technologies to detect leaks, and developing better models to predict site performance over time are critical areas for advancement. More research into identifying optimal storage locations and ensuring regulatory compliance will facilitate scaling.

Governance and Legislation

Strong, clear, and transparent legislation will be vital to building confidence in the growing CCS and CDR industries. Clear rules will give investors the certainty they need to assess risks and commit to funding, while effective oversight will ensure that the technologies are deployed safely and effectively.

For investors, a well-defined legal framework reduces uncertainty, making it easier to justify the long-term investments which will help to scale up the technologies and bring down costs.

For the public, strong legislation provides reassurance that CCS and CDR projects are properly regulated, safe, and genuinely worthwhile, while clear guidelines on monitoring, safety, and accountability will help to ease concerns about risks such as CO₂ leaks. Just as importantly, governments and developers must engage with communities and avoid riding roughshod over public opinion—especially when it comes to issues like land use and pipeline construction.

Since many CCS and CDR projects will involve cross-border transport and storage of CO₂., the harmonizing of regulations on safety, liability, monitoring, and verification will help to smooth the way to improved international cooperation.

Carbon Markets

Overview: Sequestered CO₂, whether stored in natural sinks like forests and oceans or injected underground through CCS, has no inherent economic value. Carbon markets give it value, driven by government policies that reward companies for avoiding emissions or extracting CO₂ from the air. One common mechanism is cap-and-trade, where a limit (or cap) is set on total emissions, and companies can buy or sell allowances based on how much CO₂ they emit. Another approach involves carbon credits, which represent a quantity of CO₂ either captured from industrial emissions or pulled from the atmosphere and stored. These credits can be traded, providing financial incentives to cut emissions and invest in carbon reduction technologies.
Potential: Carbon markets encourage innovation in low-carbon technologies and provide a revenue stream for companies that remove or capture CO₂ from the atmosphere. They help drive investments in carbon removal and renewable energy, supporting the global transition to a low-carbon economy.
Challenges and Areas for Future Research: Effective carbon markets will depend on accurate methods for measuring and verifying CO₂ removal to prevent greenwashing (where companies make misleading claims about their environmental efforts to appear more sustainable than they actually are). Further research is needed to improve monitoring systems for natural sinks like forests and oceans and to establish consistent, reliable standards for carbon credits. This will ensure that credits represent genuine CO₂ reductions. Additionally, enhancing market design and expanding international carbon trading systems will be crucial for ensuring strong participation and long-term success.