What is carbon capture and sequestration (CCS)?

What is carbon capture and sequestration (CCS)? 

CCS, or carbon capture, storage, and sequestration, is a carbon reduction method used to capture and store carbon dioxide after it enters the earth's atmosphere. Firstly, carbon dioxide is separated from industrial output before it's transported through pipelines to a site where it’s stored and then sequestered. Sequestering involves injecting the separated carbon dioxide deep underground where it can’t escape. This differs from carbon capture, utilisation, and storage (CCUS), which utilises the captured carbon dioxide into useful products.  

How does carbon capture work? 

CCS captures carbon dioxide at the source where the emissions occur. It is usually applied in industrial applications, where the source of emissions ranges from power plants to cement, steel, and chemical production. CCS is a key tool in carbon reduction because of the high emissions associated with these production processes. There are three different methods of capture: pre-combustion, post-combustion, and oxy-fuel combustion, which capture carbon dioxide at different release stages. 

Equipment and chemical processes involved in carbon carbon

What happens to captured carbon? 

Once the carbon dioxide has been captured at source, it’s then sequestered in a safe, long-term location.  

Geological sequestration: injecting CO₂ into underground formations 

One common location for storing carbon dioxide is deep underground in a geological location, including saline aquifers or retired oil and gas fields, where hydrogen is less likely to escape into the environment. The reason for storing it in a geological location is that it can often be trapped away from civilisation, which reduces the risk future of leaking hydrogen affecting humans. The location still needs to be monitored closely to ensure leaking hydrogen doesn’t affect the natural environment around the site.  

Carbon utilisation options: converting CO₂ into products 

Not just a capture and storage system, CCS can also be used to covert CO₂ into other products, by turning it into useful byproducts such as synthetic fuels or cement. It can also be used as part of enhanced oil recovery (EOR), which involves injecting CO₂ into depleted oil reserves in order to extract more oil. This secondary extraction method is still fairly controversial, as it encourages further fossil fuel consumption over green sources.  

Long-term monitoring and safety of storage sites 

While CCS offers a good alternative for carbon reduction, it still comes with challenges around safety. Ensuring the long-term safety of CCS sites can be expensive and time-consuming due to leakage risks and the requirement to monitor unexpected activity continuously. This is because of the risk of danger associated with volatile hydrogen. Maintaining the safety of sites is still a work in progress, as few long-term successful case studies currently exist, meaning the types of predictive maintenance based on historical data that exist for other energy sectors isn’t an option.  

Benefits of carbon capture and sequestration 

Reducing greenhouse gas emissions from hard-to-abate sectors is a key use case for CCS. Industrial activity is one of the sectors with the highest pollution, which is why CCS is such an important tool in global carbon reduction strategies. Heavy polluters include manufacturing and heavy industry, which are unable to switch to greener sources because renewable sources aren’t yet stable enough to power facilities such as manufacturing at the required level over a long period. CSS allows these heavy polluters to achieve carbon reduction goals and targets, making them greener and more compliant. 

CCS may also help to enhance the energy transition with lower-emission fossil fuel use. In an ideal energy transition model, all energy consumption would transition to green sources - unfortunately, our ageing grid and renewable technology generally aren’t yet ready to facilitate such a drastic transition. CCS is generally criticised for the fact that fossil fuels are still part of the energy consumption process and diverting funding from renewable projects. However, CCS allows the energy transition to take place while still utilising fossil fuels for the industries that need them.  

Challenges and limitations of CCS 

Public perception of CCS technology is still relatively low compared to other low-carbon solutions, partly due to a lack of understanding of the technology and the potential for hydrogen leak risks. 

This, coupled with the fact that many low-carbon methods are expensive, means that CCS is subject to high costs and energy requirements. This is partly due to the high set-up costs associated with CCS technology, with long-term cost savings not currently visible due to the lack of long-term case studies.  

The existing distribution network does not support the current infrastructure requirements for CCS, and serious upgrades would need to occur, including hydrogen pipelines, to avoid transport bottlenecks and incorporate the multitude of renewable technologies needed for a true energy transformation. Repurposing the existing infrastructure, for example, converting natural gas pipelines to hydrogen pipelines could aid the development of CCS, though this would still be an expensive task.  

The future of CCS in climate strategy 

CCS is still in the earlier stages of utilisation, which means that few successful examples of CCS currently exist. This makes cost-reduction measures more challenging. For innovation to take place within the sector, more research and development must occur in the field, which requires funding. For this funding to become available, it's important for government support and global policy support for the CCS sector, which would involve financial incentives for the technology, potential grants, and policies that specifically encourage the rollout of the technology. In the future, carbon pricing may also help steady this specific technology on the carbon market. 

CCS is also viewed as vital in the future of hydrogen production. Blue hydrogen requires the combination of natural gas and CCS in the production process.   

Carbon Capture and Sequestration (CCS) offers a practical solution for reducing emissions from hard-to-abate sectors and enabling blue hydrogen production. While it holds promise, its success relies on overcoming cost, infrastructure, and safety challenges. With strong policy support and innovation, CCS can play a key role in the transition to a low-carbon future.