Carbon Capture Storage (CCS) involves capturing CO2 emissions at large power plants and industrial sites before they enter the atmosphere. It can be performed pre-combustion or post-combustion, using oxy-fuel or absorption technology.
The captured CO2 is then inserted underground for permanent storage. Inserted sites typically use depleted oil and gas reservoirs or saline aquifers.
What is Carbon Capture Storage?
Carbon Capture Storage (CCS) involves removing CO2 emissions from power plants or industrial facilities before they are released into the atmosphere.
This can be done using a number of different techniques, including absorption, adsorption, chemical looping and gas hydrate technologies. Once captured, the CO2 is transported and stored underground.
It can also be re-used in industrial processes such as making plastics or concrete. In some cases, CO2 is also injected into depleted oil or gas reservoirs in a process known as enhanced oil recovery (EOR).
The most common method of CCS involves capturing the CO2 from flue gasses at power stations and other industrial facilities. This is known as point-source CCS.
However, it is also possible to remove existing CO2 emissions from the atmosphere, which is known as direct air capture and storage or bio-energy with carbon capture and storage (BECCS).
In general, the CO2 is captured by a process called flue gas desulphurisation, where it is pumped through a series of membranes and traps before being cooled. This can be combined with other processes such as oxy fuel or post combustion to make the process more efficient.
After the CO2 is removed from the flue gas, it is transported underground by pipelines. Typically, it is buried in saline or depleted oil or gas fields at depths of 1 kilometer or more.
Alternatively, the CO2 can be injected into saline aquifers, which are underground rock formations similar to those that have held oil and natural gas deposits for millions of years.
This is often the option chosen for newer projects such as Zero Carbon Humber in the UK, which will store CO2 in a depleted oil field named ‘Endurance’, which is located around 0.62 miles (1 km) under the seabed.
Advantages of Using Carbon Capture Storage
Carbon Capture Storage (CCS) technologies keep carbon dioxide emissions from power plants and factories from reaching the atmosphere, where they contribute to global warming. This is one way in which the Paris Agreement’s goal of limiting global greenhouse gas levels can be achieved.
CCS uses a variety of methods to separate CO2 from other gasses produced during industrial processes such as coal, oil and gas power generation and steel or cement production.
It can be done either pre-combustion (carbon capture from solid fossil fuels), post-combustion (separating carbon dioxide from the flue gasses generated when solid fossil fuels are burned) or oxy fuel technology (converting solid fossil fuels into a mixture of hydrogen and carbon under heat pressure).
Once captured, the CO2 is transported to a storage site where it is permanently stored in underground geological formations, such as depleted oil and gas reservoirs and deep saline aquifers.
This process, which is also known as mineral storage, prevents the CO2 from entering the atmosphere and mitigating against climate change effects such as ocean acidification and rising temperatures.
While CCS is an essential component of a low carbon energy economy, it does not represent a complete solution to the climate crisis.
To truly limit CO2 emissions, more renewable energy sources need to be employed, such as wind and solar power, which are becoming increasingly cheaper each year.
Alternatively, some of the captured CO2 can be used for other purposes such as enhanced oil recovery or producing chemicals.
However, using CO2 for this purpose does not reduce overall emissions or deliver a net climate benefit, once indirect and other impacts are taken into account. Therefore, storing it instead of using it is the best option.
Challenges Faced with Carbon Capture Storage
Despite the promise of carbon capture storage, the technology remains very much a work in progress. One of the major challenges is the scalability of the process.
The cost of capturing CO2 has to be reduced significantly if the world is going to turn to CCS for its energy needs. Companies like Noya Labs are working to cut costs by turning existing infrastructure such as cooling towers into CO2 sucking devices.
Another challenge with CCS is that it will not be a true climate solution as long as it is attached to fossil fuel power plants. This is because the technology will only reduce the direct emissions from the power plant by 80-90%.
The rest of the emissions will come from other industrial processes such as cement and steel production. Using CCS in conjunction with renewable energy sources would give the technology its full climate benefits.
Carbon Capture Storage also has to be paired with some sort of use for the CO2. The most popular utilization so far is the injection of CO2 into oil wells for enhanced oil recovery.
While this may help to increase the amount of oil that can be extracted from a well, it does not reduce emissions or deliver a net climate benefit once indirect and other effects are taken into account.
The liquefaction and transportation of CO2 for storage requires the expending of more energy.
There is also the risk of leakage from artificial underground reservoirs. The recent leaking of CO2 in Mammoth Mountain, California provides some perspective on the potential environmental impact of this risk. This could result in acidification of soils, increased mobility of heavy metals, and potentially more carbon dioxide entering the atmosphere.
Practical Uses of Carbon Capture Storage
The system can be used to prevent future CO2 emissions, or remove carbon dioxide from the atmosphere that has already accumulated as part of industrial processes like power generation and bioenergy production.
The capture process consists of three major steps: capturing, transportation and storage.
The first step, capture, involves separating out carbon dioxide from other gasses and particles at the source of the emission using a variety of techniques including absorption, adsorption, chemical looping, gas hydrate technologies and membrane gas separation. The captured CO2 can then be compressed and transported to a site for permanent storage.
Various methods are available for storing the carbon dioxide, with most options involving injecting it underground.
Many different geological formations are suitable for this, including saline formations, depleted oil and gas fields, unmineable coal areas and basalt rock formations.
Saline formations are particularly promising because they can be capped with concrete and have a high enough porosity to allow for efficient and safe storage.
In some cases, the CO2 is injected underground to be used in a process called enhanced oil recovery (EOR). Other uses include making plastics and chemicals, growing greenhouse plants or even carbonating fizzy drinks.
However, the quantity of carbon dioxide gas needed to make these products would be too small to have any significant impact on global GHG emissions. For that reason, it’s essential to focus on securing permanent storage for the rest of the captured CO2.
Future Outlook for Carbon Capture Storage Technology
The CO2 that is released by burning fossil fuels enters the atmosphere, causing global warming. This has many negative effects, including temperature and sea-level rise, melting ice caps, changes in precipitation patterns, ocean acidification, and more.
Carbon capture and storage (CCS) is an important technology that can mitigate these issues by removing CO2 from the air before it can reach the atmosphere.
There are about 20 CCS projects operating globally, but they are not yet enough to make a significant dent in the global emissions that are currently threatening our planet. This is why BNEF has identified CCS as one of the key technologies that will be required to achieve our climate goals. The technology can reduce power plant emissions as well as those from hard-to-abate industries like petrochemicals and cement.
Once captured, the CO2 can be transported to a site where it will be stored underground for permanent disposal. This can be done via pipelines, rail or tanker trucks, but pipelines are generally considered the cheapest option. Pipelines need to be specially designed since they must be able to hold large amounts of pressurized CO2 at very cold temperatures.
Despite the challenges, the future looks bright for CCS technology. More plants are being built that can rely on the technology, and investors are starting to see its value.
Governments are offering incentives for companies to develop and deploy the technology. The United States is increasing its tax credits for CCS, while Canada and Australia are establishing grant schemes to advance the technology.
As a result, carbon capture technology is on track to become a viable alternative to renewable energy sources for the generation of clean and affordable power.