In recent years, there has been a significant move towards supplying our energy by renewable energy. This looks set to continue to increase due to positive changes in government policies and legislation, including a growing number of countries making commitment to achieve net zero by 2050 or earlier.
However, presently in 2022, we are still heavily reliant on fossil fuels - 78% of the UK’s electrical power production was fossil-fuel based in 2019. As we are making the long-term transition to net zero carbon emissions solutions, we will continue to use fossils fuels as a significant source of our energy supply. Therefore, we need a way to minimise or eliminate the carbon emissions from these fuels. Carbon capture is a technology that allows us to burn fossils fuels but, prevents the release of CO2 into the atmosphere.
Why are carbon capture technologies being considered?
The aim of implementing CCS and CCU technologies is to prevent the release of CO2 to the atmosphere from large emitters such as heavy industry (steel, cement, power generation, refining and chemicals manufacturing). These industries require high temperatures and high intensity energy supply, which make electrification (from renewables) very difficult. Therefore, it is very probable that fossil-based energy is likely to remain in place for years to come in these sectors.
What are the different types of carbon capture technologies?
1. Pre-combustion:
The CO2 is removed from fossil fuels before combustion is completed. The fuel is partially oxidized in steam and oxygen/air at high temperature to form a mixture of hydrogen and carbon monoxide, known as syngas. The mixture is then reacted with water to form hydrogen and a highly concentrated carbon dioxide stream that can be re-used or stored. Today’s commercially available pre-combustion carbon capture technologies use physical or chemical absorption processes which cost around $60/tonne, for example, in an integrated gasification combined cycle power plant.
2. Post-combustion CO2 capture by Adsorption:
Adsorption is a reliable process technology that has been in use since the 1960s for gas separation applications. The combustion flue-gas is fed to an adsorber which produces a concentrated carbon dioxide stream that can be stored or reused. With developments and improvements made over time, there is now a 90%+ recovery rate and 95% purity levels are possible for post-combustion capture.
3. Oxyfuel combustion:
Pure oxygen is used to combust the fuel (instead of air) and the leftover exhaust gas has a very high concentration of carbon dioxide, which can then be reacted with a sorbent in the CCS process for separation, then transportation and storage.
4. Chemical looping:
A newer concept that is gaining more attention, and a variant similar to oxyfuel combustion. There has recently been the successful completion of chemical looping pilot plant trials in the USA. Chemical looping delivers only oxygen to the coal combustion process - excluding other gases such as nitrogen found in air. This enables an almost pure CO2 gas to be produced, which can then be stored without need for further processing. The oxygen is delivered via a metal oxide reaction. Due to the nature of the reduction reaction, the resulting metal particles can be recycled back to metal oxide (hence, the looping).
5. Membrane gas separation:
This is a physical separation process that passes flue gas across a porous membrane, enabling the segregation of the CO2 molecules from the other combustion products, such as water.
6. Pyrogenic carbon capture and storage:
This is a new technology that is currently under development.
Plants remove CO2 from the atmosphere using its growth via photosynthesis. The plants are harvested as biomass which is then pyrolyzed (thermal treatment of the biomass feedstock in an oxygen-deficient atmosphere). A portion of the carbon bound in the biomass is reduced to solid carbon and heavy, viscous compounds in the pyrolysis process. This carbon-rich material is used to improve soil fertility. The flammable gas (syngas-type) mixture that remains is collected and used as a fuel. The CO2 produced from the combustion of the pyrolysis gas can then be captured traditionally, using the other processes described previously.
The advantages of carbon capture technology:
Some of the advantages of carbon capture technology are that it is easier to remove the carbon dioxide at source before it is released. Once it is in the atmosphere, the concentration of the gas is low so requires much more energy to concentrate and remove.
Another advantage is that it is fortunately possible to remove other pollutants at the same time as capturing the carbon dioxide. During oxyfuel combustion, for example, high concentrations of oxygen are used for combustion which leads to a significant reduction in the levels of nitrogen oxide and sulphur dioxide gases (up to 50% decrease in some cases) compared to combustion with air. Particulates can also be more easily removed.
Another advantage of carbon capture is that it allows us to continue to use fossil fuel resources without releasing more greenhouse gases into the atmosphere. This can help ensure energy security and can reduce the amount of energy that needs to be imported. Carbon capture helps to limit the impact we have on the environment for the time we still need to rely on fossil fuels.
One of the principal drawbacks of renewables is due to their variation in supply of energy. When there is limited solar or wind energy but, a high demand for power, fossil fuels are often used. Carbon capture allows us to still have this energy security without the fossil-fuel related damage. There are other technologies being developed to try and overcome this including green hydrogen but, one of the main disadvantages of hydrogen is the loss of energy when it is converted - burning fossil fuels does not have this issue.
The disadvantages of carbon capture technology:
Unfortunately, the cost of CCS right now is high. If subsidies were to be taken away, one report estimated a 50-80% increase in the cost of electricity in order to pay for the implementation of the CCS technology. In most locations globally, there are no regulations, policies or subsidies incentivising the implementation of the technology. Therefore, the cost of equipment, materials and infrastructure is just too high to justify most plants implementing it.
Another disadvantage is that carbon capture could potentially be used as a ‘get out of jail free card’ by the fossil fuel industry. By investing heavily in carbon-capture, it could be claimed that net zero is achieved without easing or diversifying operations.
One current use of the carbon dioxide captured during the CCS process is enhanced oil recovery. This process is when oil companies take the captured CO2 and inject it into depleted oil wells to recover otherwise inaccessible oil. When the captured CO2 is used in this way, it is adding more CO2 to the atmosphere via the combustion of the oil that was made available – which defeats the purpose.
Another drawback of carbon capture, specifically carbon capture and storage is that scientists are unsure if there is enough storage capacity to meet our needs. Globally, it is not certain how much CO2 storage capacity there is but, it is already evident that some countries physically do not have enough suitable storage locations. This could be overcome by shifting more towards carbon capture and utilisation.
Another concern and disadvantage of carbon capture is CO2 leakage. It is a real and possible issue when it comes to CO2 storage and transport. While accident rates during the transport of CO2 are relatively low, the potential for a dangerous leak still exists and according to the IPCC, if a CO2 leak was to occur, a concentration between 7% and 10% in the air could pose a threat to human life. It is also a possibility that CO2 could leak at the site of underground storage. This could put the health of surrounding people and animals at risk, but also could contaminate both the soil and groundwater in the area, as well as the loss of the CO2 to the atmosphere (meaning that the process of storing it was pointless).
One final issue that occasionally arises when it comes to CO2 storage is the NIMBY (Not in My Back Yard) effect. Whilst public awareness of CCS in most of the world is generally reasonably low, when CCS projects are going to be built nearby, people could reject them because of the perceived “risks” to health, local environment (plant visibility) and lifestyle.
As an example, what is the UK government’s strategy towards carbon capture?
In 2012 the UK government began to invest in Carbon Capture and Storage or Utilisation technology and later, in October 2017, the UK government announced its new approach to carbon capture, usage and storage in the Clean Growth Strategy. The aim of the approach is for the UK to become a global technology leader for CCUS and to ensure that the government has the option of deploying CCUS at scale during the 2030s.
The UK government are taking action in 3 areas:
· re-affirming commitment to deploying CCUS in the UK subject to cost reduction,
· international collaboration on CCUS, and
· CCUS innovation.
1. Cost reduction:
CCUS has the potential to decarbonise the UK’s economy and create economic (technology and skills export) opportunities for the UK. However, currently due to its expense, cost reductions and subsidies are necessary to be able to deploy CCUS in the UK. The UK government is claiming that they expect that this will provide value for money for both the taxpayer and consumer.
The government has established a CCUS Cost Challenge Taskforce to provide advice on the steps needed to reduce the cost of deploying CCUS in the UK, as well as setting out a programme of work that will be undertaken to establish the additional steps that are required to meet the ambition of having the option to deploy CCUS at scale during the 2030s. Following the advice of the CCUS Cost Challenge Taskforce the government published the “UK CCUS Deployment Pathway: An Action Plan”- which is setting out the next steps government and industry should take in partnership to achieve the ambition of having the option to deploy CCUS at scale during the 2030. In this plan there is an emphasis on how the private and public sectors can work together to deliver the government’s ambition for CCUS and how the barriers to cost effective deployment can be reduced.
2. International collaboration on CCUS:
In the Clean Growth Strategy, the UK government also committed to convene and lead a new international working group to drive down the cost and accelerate deployment of CCUS. They will be working closely with private sector led initiatives such as the Oil and Gas Climate Initiative as well as aiming to develop closer collaborative working with countries such as Norway, the USA, Canada and Australia to encourage joint working on innovation and CO2 transport and storage solutions.
The UK government will aim to continue to be a global leader in CCUS investments through the UK’s £60 million international CCS programme, by investing a further £10 million in the programme.
3. CCUS Innovation:
CCUS R&D and innovation will play an important role in reducing the costs of CCUS, by developing cheaper and more efficient technologies and components, exploring new applications and supporting innovations that reduce the cost of transporting and storing carbon dioxide.
The UK government has invested over £130 million since 2011 in R&D and innovations to support the development of CCUS in the UK and this support is continuing as the UK government is committing to spend up to £100 million from the BEIS Energy Innovation Programme to support industry and CCUS innovation and deployment in the UK.
The government have set up a Carbon Capture and Utilisation demonstration programme as well as supporting the development of next generation capture technologies. The main aim is to lower the cost of capture compared to the current best performing technologies.
The UK is one of nine European countries participating in the ERA-NET scheme to accelerate CCS technologies. Together these nine countries and the European commission have provided €36.6million to support a first call for collaborative projects to accelerate the deployment of CCUS in Europe.
The UK government are aiming to capture 10 Million tonnes of carbon dioxide a year by 2030.
Conclusion:
In conclusion, carbon capture offers a potentially feasible way to decarbonise fossil fuels and there are a variety of technologies available both pre- and post- combustion. It is a great tool to support our move towards net zero emissions, offering a zero carbon emission balance for the variability of renewable energy production. It has many great advantages:
· it allows us to remove carbon at the source, early in the process, rather than once it is diluted in the atmosphere,
· it allows us to remove other pollutants at the same time as removing the carbon.
· Carbon capture will support our move towards net zero in 2050 by helping remove the emissions from the fossil fuels we are so reliant upon at the moment and as we transition to becoming more reliant on other sources of energy.
· Carbon capture also offers a solution to counteract the drawbacks of some renewables, when energy demand is high but, renewable production is low, energy security can be ensured through utilising carbon capture when burning fossil fuels to meet the demand.
Carbon capture unfortunately has some drawbacks as well:
· we should be careful to ensure that the technology is not over relied upon or exploited and used as a ‘get out of jail free card’ to enable oil and gas companies to continue in their current ways.
· One of the main issues associated with carbon capture is the expense. The UK government, for example, have a number of impressive schemes and grants set up in order to further the evolution of CCUS, with the main aim being cost reduction.
· However, in order to have a full overhaul of industry, there will also have to be a considerable amount of progress in the private sector.
Reaching net zero by 2050 will be an extremely difficult feat, but using a variety of solutions, it is possible. Carbon capture is one tool in the toolbox that could assist us in our journey towards net zero but, it needs to be used in combination with other strategies – maximise electrification supplied from renewable energy, green hydrogen from renewables and electrolysis, re-use of carbon as green methanol to displace fossil fuels, etc.
If you are considering potential options for carbon capture on your site, FCW/CREAS can support you with conceptual studies, technical analysis, technology and vendor selection and commercial modelling.