Point Source Carbon Capture: Tackling Emissions

Key Points
Point Source Emissions
Integration of Capture Systems
When CO₂ is Captured – Different Combustion Strategies
Capture Technologies
What happens to the captured CO2?
Forming alliances to share transport and storage costs
Challenges ahead
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Key Points

In industries like cement, steel, and certain chemical manufacturing, CO₂ emissions result not only from burning fossil fuels to generate the high temperatures required, but also from the unavoidable chemical reactions that occur during production, making the complete elimination of CO₂ emissions from these sectors particularly challenging.
Industrial facilities produce what are known as point source emissions since the CO₂ originates from specific, fixed locations, unlike the more spread-out emissions from sectors such as like transportation or agriculture.
Since the concentration of CO₂ in flue gases from these point source emissions is relatively high—typically between 10–30%—they are well suited to carbon capture and storage (CCS). This involves separating CO₂ from other gases and transporting it to a site where it can be permanently stored deep underground.
While fossil fuel-burning power stations can potentially be replaced by renewable energy sources such as wind or solar, some 'hard-to-abate' industries—such as cement and steel manufacturing—are more difficult to decarbonize. This is because they produce CO₂ not only from combustion emissions (burning fuels for heat and power) but also from process emissions, which are released by the chemical reactions involved in production itself—for example, when limestone is converted to lime in cement making.
Once captured, CO₂ can be compressed into a liquid state for easy transportation, typically by pipeline or ship, to long-term underground storage sites, where it can be safely contained, preventing it from re-entering the atmosphere.
For sectors where no practical alternative currently exists to prevent CO₂ release, capturing and storing carbon is increasingly being explored as a possible solution.
Although various technolgies for separating CO₂ from the other gases present in industrial emissions are advanced and well understood, the processes are energy intensive and expensive, and the development of the infrastructure required for the transportation and permanent storage of CO₂ is in the extremely early stages worldwide.

Point Source Emissions

Point source emissions refer to the gases released from industrial facilities and power plants, in contrast with dispersed sources like transportation or agriculture. These point source emissions often contain high concentrations of the greenhouse gases, such as carbon dioxide (CO₂), responsible causing for global warming

What types of industries and processes produce significant point source emissions?
The main point source emitters include:

Power generation from fossil fuels (such as coal, oil, natural gas) or biomass combustion.
Cement production, which emits CO₂ both from burning fuel and from the chemical reaction that converts limestone to lime.
Steel manufacturing, particularly in blast furnaces using coke, a carbon-rich fuel.
Chemical production, such as ammonia and hydrogen synthesis, which involve processes that release CO₂ as a by-product.

Oil refining, where crude oil is processed into fuels and other products, generating CO₂ during both combustion and chemical processing.

What proportion of global emissions do point sources represent?

Point source emissions—those from large facilities like power plants and industrial sites—account for a significant share of global CO₂ emissions. According to the International Energy Agency, electricity and heat production contributed approximately 39% of global energy-related CO₂ emissions in 2022, while industrial processes, including cement, steel, and chemical manufacturing, accounted for around 25%. Combined, these point source sectors represent roughly 64% of global CO₂ emissions.

Why do these industries produce so much CO₂?
These industries tend to be energy-intensive and often rely on the combustion of fossil fuels to generate the high temperatures required. Additionally, some processes like cement and steel production release CO₂ as a result of the chemical reactions which take place during the manufacturing process, not just from energy use.
The CO₂ emitted from burning carbon-based fuels such as coal, natural gas or oil is referred to as combustion emissions.
CO₂ generated from chemical reactions during manufacturing is terme process emissions.

Examples of process emissions include:

In cement production, the CO₂ which is released when limestone (CaCO₃) is heated to produce lime (CaO).
In steel production, the CO₂ which is generated when coal is used as a chemical reducing agent, removing oxygen from iron ore (iron oxide) to produce pure iron, with CO₂ as a by-product.

Are there alternatives to these carbon-intensive industrial processes?

Renewable energy can replace fossil fuel power plants, although fluctuations in supply and energy storage remain issues for wind and solar.
The electrification of steel furnaces to generate the high temperatures required, and the use of green hydrogen—produced using renewable energy sources like wind or solar—to replace coal as the reducing agent for stripping oxygen from iron ore, are both technically feasible but currently significantly more expensive than conventional coal-based methods.
Replacing cement with lower-emission alternatives: Substituting traditional cement with materials that generate less CO₂—such as volcanic ash or industrial by-products like slag from steel production—can reduce the carbon footprint of concrete.
Carbon capture and storage (CCS): For industrial processes where emissions are difficult or costly to eliminate, CCS offers a potential pathway to reduce CO₂ at the source. By capturing emissions from smokestacks and transporting them for permanent underground storage, CCS can help mitigate the climate impact of sectors where other options remain limited or expensive.

Integration of Capture Systems

How advanced are CO₂ capture technologies for point sources?
CO₂ capture technologies are relatively mature, with some having been used commercially for decades in industries such as natural gas processing. However, applying them at the scale required to make a meaningful impact on reducing CO₂ emissions is still in the very early stages of development.

Carbon dioxide can be captured at different stages of industrial operations. In power generation, this typically means capturing emissions either before combustion (pre-combustion) or after combustion (post-combustion). In industries like steel and cement, it also includes capturing process emissions released during chemical reactions—such as converting limestone to lime or reducing iron ore. Regardless of the source, CO₂ must then be separated from other gases using a variety of capture technologies.

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When CO₂ is Captured – Different Combustion Strategies

These strategies describe when carbon dioxide is captured in relation to the combustion of fuel—either before it is burned (pre-combustion), after combustion (post-combustion), or by modifying the combustion environment itself (oxy-fuel combustion).

The main types of point source capture—defined by the stage of the combustion process at which CO₂ is removed—include:

Post-combustion capture
This is the most commonly used method and can be added to existing power plants and industrial sites. It captures CO₂ from flue gases after fuel is burned, usually by passing the gases through a chemical solvent such as amines that absorb the CO₂.
Advantages: Can be retrofitted to existing facilities; already in use in several industries.
Disadvantages: The CO₂ concentration in flue gases is relatively low—typically between 10–15%—which means separating it requires more energy compared to other methods.

Pre-combustion capture
In this method, fuel is chemically converted into a mix of hydrogen (H₂) and carbon dioxide (CO₂) before it is burned. The CO₂ at this stage is more concentrated and under higher pressure, which makes it easier and more efficient to separate. The hydrogen is then used as a low-emission fuel.
Advantages: More efficient CO₂ capture due to higher concentrations and pressures.
Disadvantages: Usually only suitable for new plants specifically designed for this process.

Oxy-fuel combustion
This method burns fuel in pure oxygen instead of air, creating a flue gas made up mainly of CO₂ and water vapor. After the water is removed, the remaining gas is almost pure CO₂, which makes it easier to separate.
Advantages: Produces a nearly pure CO₂ stream, simplifying capture.
Disadvantages: Producing the pure oxygen for combustion requires a lot of energy, increasing overall costs.

Capture Technologies

Once CO₂ is available for capture—whether from combustion gases or industrial processes—it must always be separated from other gases. This is achieved using various technologies that rely on chemical reactions, physical forces, or selective membranes. These methods vary in complexity, energy requirements, and suitability for different industrial applcations, but all serve the same purpose: isolating CO₂ for subsequent handling, transportation and storage.

Absorbent-Based Capture

This approach uses a liquid that chemically reacts with carbon dioxide (CO₂) in a gas stream. As the gas flows through the liquid, CO₂ is selectively removed and held within the liquid. To reuse the liquid, it is heated, which causes the CO₂ to be released. The CO₂ can then be compressed and stored or used, and the liquid is cycled back into the process. This method is mature and commonly used in power generation and industrial processes.

Sorbent-Based Capture

In this method, CO₂ is captured by solid materials designed to chemically bind with it. These materials are typically used in fixed systems where gases are passed over or through them. The captured CO₂ is later released by applying heat or changing pressure, and the solid can then be reused. This technique is well-suited for high-concentration CO₂ environments and for capturing CO₂ directly from ambient air.

Membrane-Based Capture (Selective Separation)

Membrane systems use specially engineered materials that allow certain gases to pass through more readily than others. In carbon capture, membranes are used to separate CO₂ from other components in a gas stream based on differences in their physical properties, such as size or solubility. Membranes do not involve chemical reactions and are advantageous where simplicity, compactness, or lower maintenance are priorities.

Adsorbent-Based Capture (Physical Surface Attachment)

This process captures CO₂ by attracting it to the surface of porous solid materials. Unlike sorbents that form chemical bonds, adsorbents use physical forces to trap CO₂ molecules on their surface. These materials can be regenerated by altering temperature or pressure conditions, releasing the CO₂ for further handling. This method is often used in pressure swing or temperature swing adsorption systems.

Mineralization of CO₂

Mineralization involves the direct reaction of CO₂ with minerals—either naturally occurring ones like olivine and serpentine, or industrial by-products such as steel slag, cement kiln dust, and fly ash—to form stable solid carbonates. This process transforms gaseous CO₂ into a permanently fixed solid, preventing its release back into the atmosphere. It can also be integrated into industrial processes like cement and steel production, where reactive mineral phases are already present.

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What happens to the captured CO₂?

Although there is a market for CO₂ in industrial processes, current and projected demand will likely be insufficient to accommodate the volume of CO₂ that would be captured if carbon capture technology is deployed at the scale needed to significantly reduce global emissions.

The only realistic option for the disposal of hundreds of millions, and possibly billions, of tonnes of captured CO₂ annually is geological sequestration, where compressed CO₂ is pumped deep underground into suitable rock formations to permanently prevent its release back into the atmosphere.

The most promising geological storage sites for CO₂ are:

Depleted oil and gas reservoirs: These have proven ability to trap fluids for millions of years and often have existing infrastructure that can be modified for CO₂ injection.
Deep saline aquifers: These are layers of porous rock filled with salt water, offering vast potential storage capacity.

How will captured CO₂ be moved to these locations?
Since suitable geological storage sites are often located far from major industrial areas, captured CO₂ will need to be transported over potentially long distances of hundreds of kilometres.
This will require:

Pipelines: The preferred option for onshore transport over long distances. CO₂ pipelines already exist for use in enhanced oil recovery, a process where CO₂ is injected into oil fields to help extract more oil, but a much more extensive network will be needed to service the widespread adoption of CCS.
Ships: Useful for offshore storage sites or when pipelines are not feasible. CO₂ can be transported in specialized tanker ships, similar to those used for liquefied natural gas (LNG).
Trains: Practical for transporting moderate quantities of CO₂ over land when pipelines are not viable, though less suitable for the largest-scale CCS operations.

Forming alliances to share transport and storage costs

How can the enormous costs of carbon capture infrastructure be shared?
Developing extensive CO₂ transportation networks and storage facilities represents a significant financial challenge for individual companies. To ovecome this economic barrier, collaborative approaches are increasingly being explored:

To address this, two concepts are gaining traction:

Carbon Hubs: These are centralised facilities designed to collect and manage CO₂ emissions from multiple nearby sources. By bringing together CO₂ from various industrial emitters, carbon hubs allow companies to share the costs of expensive transportation and storage infrastructure. Acting as collection points, they gather CO₂ from different capture sites before it is transported to a storage location, helping to streamline the process and make it more affordable for all parties.
Industrial Clusters: These are groups of CO₂-emitting industries located near each other that can share infrastructure for transporting and storing captured CO₂. By forming regional partnerships, these industries can split the costs of pipelines, storage facilities, and other necessary infrastructure, making carbon capture and storage more efficient and cost-effective.

If separating CO₂ from industrial flue gases is so energy-intensive, why not just capture and store all of the flue gases?

While disposing of the entire flue gas mixture might seem like a simpler alternative to the costly process of separating CO₂, there are several compelling reasons for isolating CO₂ before storage:

Higher volumes: Managing and storing the entire gas mixture would require handling much larger volumes. Typical flue gas from a coal-fired power plant contains only about 10-15% CO₂, with the rest primarily composed of nitrogen, oxygen, and water vapor. For natural gas power plants, the CO₂ concentration is even lower, around ₃₊^-5%. Separating CO₂ significantly reduces the volume that needs to be transported and stored.
Different behaviours of gases: Transporting captured CO₂ and injecting it into underground rock formations requires first compressing it into a supercritical state—a phase where CO₂ has the density of a liquid but flows like a gas. Since CO₂ becomes supercritical under conditions where oxygen and nitrogen remain gases, handling and transporting a mixed stream would be significantly more complex and less efficient.
Storage security concerns: The underground behaviour of a gas mixture would be harder to predict, potentially compromising the security of long-term storage. Some CO₂ storage methods rely on the gas dissolving in concentrated salt water or reacting with silicate rocks to form carbonate minerals—processes that could be disrupted by the presence of other gases.
Infrastructure challenges: Water vapor and other impurities in flue gas can cause corrosion in pipelines and equipment.
Reusing captured CO₂: If the captured CO₂ is intended for industrial reuse, achieving a high level of purity is essential.

How much will point source carbon capture cost and how will it be financed?
The cost of point source carbon capture will vary significantly depending on factors such as the ease of retrofitting existing facilities and access to shared infrastructure like CO₂ pipelines or storage sites. Operational costs, such as energy consumption for capture processes and ongoing maintenance, will play a crucial role in long-term viability.

As carbon capture technology matures and becomes more efficient, operational costs are expected to decline, and economies of scale should influence the upfront cost of carbon capture and equipment.
Widespread adoption of carbon capture will almost certainly depend on a combination of private investment and public support. Private sector involvement will drive innovation and efficiency, with government backing helping to reduce financial risks and encourage early adoption.

Governments will be able to stimulate development through several mechanisms:

Establishing stable carbon markets to create long-term value for emissions reduction
Offering grants for research and pilot projects
Providing tax incentives to offset high initial costs

These measures, coupled with technological advancements, will be essential in making carbon capture economically feasible across various industries. As projects scale up and become more standardized, the cost per ton of CO₂ captured should decrease, potentially opening up new applications and markets.

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Challenges ahead

What key areas require further understanding before implementing CCS at the necessary scale?

Improving the energy efficiency of current carbon capture technologies will critical to reduce costs and make them more attractive to industries.
Knowing the environmental impacts of large-scale CCS
Optimizing the integration of capture systems with different industrial processes
Understanding how CO₂ behaves in long-term geological storage will be essential to ensure it stays securely contained underground. Monitoring and ensuring that captured CO₂ does not leak over time is a key aspect of making CCS a sustainable option."

Are there any ongoing pilot projects for point source carbon capture?

Boundary Dam (Canada): World's first commercial-scale CCS project on a coal power plant
Petra Nova (USA): Largest post-combustion capture project on a power plant (mothballed in 2020 due to low oil prices)
QUEST (Canada): Captures CO₂ from oil sands hydrogen production
Northern Lights (Norway): The Northern Lights project (Norway) is developing an integrated CCS system that covers all stages from capture to long-term storage, including CO₂ transport and injection into offshore geological formations.

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