Carbon capture is the process of absorbing CO2 either from the source of point like power plants’ smoke stacks or from ambient air instead of emitting it into the atmosphere. The carbon capture technologies include a variety of technologies designed to prevent the release of CO2 in the air that is generated through conventional power generation or industrial production.
Carbon capture technologies can take various forms and have a variety of approaches. Direct air capture (DAC) is one approach that uses a technology to extract CO2 directly from the atmosphere. The carbon dioxide could then be used as a resource from the industry in the making of different products – a climate change mitigation process called carbon capture utilization and storage. Alternatively, the extracted CO2 could be stored underground for permanent geological storage in suitable locations.
Other carbon removal approaches using carbon capture technologies are artificial trees that also absorb CO2 directly from the atmosphere and are considered an example for DAC. There are numerous devices like trees, artificial mountains or air capture balloons, developed by scientists who are looking for a way to tackle the excess levels of GHG emissions that have been accumulating in the atmosphere for the past decades.
Why Do We Need Carbon Capture Technologies?
Currently, economies and countries around the world rely heavily on fossil fuel commodities. 84% of the global power generation still comes from fossil fuels which release a significant amount of CO2 directly into the atmosphere. The world emits around 40 gigatons of GHG emissions every year which are the cause of climate change.
A drastic substitution of fossil fuels with an alternative energy source that emits no emissions is practically impossible to happen in the near future. Therefore the science community and the industry is researching the adoption of carbon capture technologies as an effective approach for limiting the impact of those emissions.
Even if the world stops releasing CO2, we still need to take out massive amounts that have piled up already in the atmosphere since the Industrial Revolution. The scale of this task is overwhelming, as the amount the world needs to pull out from the atmosphere is around 800 gigatons. That requires serious ambition from governments to invest on a large-scale deployment of carbon capture combined with other climate mitigation technologies and people’s willingness to change their behaviour.
The International Panel on Climate Change (IPCC) has also estimated that approximately 10 gigatons of net CO2 removal per year by the year 2050 needs to be accomplished in order to keep global temperatures below a 1.5 or 2C increase. As governments, companies, investors, and entrepreneurs have already started developing solutions to raise up to this challenge, it is clear that the world will need a range of carbon capture technologies to complement the work of removing CO2 from air that is already underway.
Deployment Needed Around The World
So far, a large carbon capture plant can take away and sequester around 1 million ton of CO2 per year each. Around 40000 CCS plants in total could be needed to capture the extra emissions that are generated annually. In comparison, there are currently about 62,500 power plants operating around the world. Included are coal-fired plants, hydroelectric dams and wind farms. The task seems less overwhelming as the number of CCS facilities that would need to be built to offset all man-made emissions is still less than the power plants built worldwide.
Carbon capture technologies help in reducing carbon dioxide in the atmosphere. As industrial processes emit tons of CO2 per year, CO2 capturing systems have been designed to help in the elimination of pollutants. The overall aim of the carbon capture systems is to take out carbon dioxide that could be sequestered in geologic formations or used as an ingredient in a variety of industries.
Pre-Combustion Carbon Capture Process
Today’s power plants function through a combustion process of the fossil fuel to generate electricity or heat. The capture processes of the CCS technologies are named depending on the time when CO2 is eliminated from the combustion of fossil fuels or in the industrial production process. They can be grouped in three categories and the suitability of their application depends on the type of industrial process or power plant.
The first carbon capture approach is called pre-combustion. It refers to removing carbon dioxide from fossil fuels before their combustion is carried on. The process starts with primary fuel reacting with steam and air or oxygen. It then gets converted to a mix of carbon monoxide and hydrogen, often called a ‘syngas’. The syngas can then undergo a water-gas shift reaction to convert CO and water (H2O) to H2 and CO2, producing a gas mixture rich of H2 and CO2.
The CO2 concentration in the mix can range from 15 – 50%. The CO2 can then be separated and captured, transported, or ultimately sequestered underground for storage. The resultant hydrogen could also be used to generate power or heat. The pre-combustion technology is particularly suitable to be applied to integrated gasification combined cycle (IGCC) power plants.
Post-Combustion
The next carbon capture process is called post-combustion. Several post-combustion methods can be used but they involve the use of a solvent to capture the CO2. The most common one includes passing the CO2-laden flue gas through a solvent in an absorption column, followed by desorption or stripping column. The absorber captures around 85% to 90% of the CO2 produced. In the stripping column, a change in temperature and/or pressure will then release the carbon dioxide.
Another process in development is called calcium cycle capture where lime is used to take out CO2 to produce limestone, which can then be heated to remove the CO2. The post-combustion technology is applicable for carbon capture at pulverized coal (PC) plants, and natural gas combined cycle plants (NGCC).
Oxy-Combustion
The third carbon capture approach is an option to the post-combustion process and is called oxy-combustion. The method has recently been developed as a CO2 capturing technology. The process uses pure oxygen in the combustion process which results in flue gas only made up of CO2 and water droplets as well as some impurities like sulfur dioxide. Compression and reducing the temperature of the flue gas is used in the removal of the water vapor.
This process leaves behind pure CO2 which can be used by the industry or stored directly. One advantage of oxy-combustion over post-combustion is the avoidance of an expensive CO2 capture system for post-combustion. Instead, the oxy combustion uses an air separation unit (ASU) to produce clean oxygen with around 95% to 99% purity.
CO2 Removal Techniques
There are also different CO2 separation techniques used in the carbon capture processes. The most commonly used technology for low concentration CO2 capture is absorption with chemical solvents. This chemical absorption process is adapted from the gas processing industry. The currently preferred chemical solvent technology for carbon capture is amine-based chemical absorbent.
Adsorption is another separation technique which is slightly different from absorption because adsorption includes specific creation of physical and chemical connection between CO2 and the surface of the adsorbent. An advantage of physical adsorption methods is the possibility for low energy requirements.
The membrane technology separation systems include thin barriers that allow selective permeation of certain gases, allowing one component in a gas stream to pass through faster than the others. Membrane separation can be considered a combination of adsorption and absorption. CO2 dissolves in the membrane and diffuses via rate proportional to its partial pressure gradient. It is used in CO2 elimination from natural gas and capturing carbon from flue gas.
Leading Carbon Capture Companies
The carbon capture technology industry is still in its infant stage. As more and more carbon capture technology companies and governments are setting up aggressive decarbonization calls, the role of the technology and the processes associated with it is getting bigger as well. A growing number of startups and carbon capture companies are emerging to embrace, develop and scale the technology globally. They are working to make carbon capture achieve economies of scale and become more viable and profitable.
Some of these companies are Global Thermostat, Carbon Engineering, Climeworks, and oil and gas giants like Shell, Exxon, Equinor and Chevron that have invested in CCS projects around the world.
Global Thermostat is a New-York based company that uses direct air capture technology to reverse climate change. Its process removes 5 pounds of CO2 per kWh of electricity. It could be installed close to industrial facilities or fossil fuel power plants to reduce the impacts from their polluting operations. The company has two pilot facilities, each with the capacity to remove 3,000 to 4,000 metric tons of CO2 per year. ExxonMobil aims to help the company build bigger facilities in more places, until they can remove a gigaton of carbon dioxide every year.
Carbon Engineering is also a leader in direct air capture technologies, using a 100-year-old industrial process that is well-understood. It integrates an air contactor and a regeneration cycle for continuous capture of atmospheric carbon dioxide and production of pure carbon dioxide. The CO2 later can be either sequestered or used in various industrial applications. The company is also working on technology for using CO2 as one of the feedstocks for creating “clean” synthetic fuels.
Climeworks is a Swiss carbon capture company, focused on taking out CO2 directly from the air. Its technology is based on a cyclic adsorption and desorption process on a filter material, known as a “sorbent.” During adsorption, atmospheric CO2 is chemically bound to the sorbent’s surface. To be driven off the sorbent, the CO2 is heated to 100 C.
The process is relatively cheap and not much electricity is needed for pumping and control purposes. The company has a test facility in Iceland as part of a larger carbon capture project in partnership with Carbfix, established in 2017. Climeworks’ goal is to capture up to 1% of all global emissions by 2025.
Cost And Future Development Of Carbon Capture Technologies
Carbon capture technologies are one of the most feasible options for the reduction of emissions from industrial facilities. Right now the capture processes are expensive due to the high installation and energy costs involved. A plant with carbon capture technology installed requires between 25-40% more energy for the additional equipment used to capture and compress the CO2.
Looking solely at the capture process without storage, the carbon capture cost can vary from $15-$25 per ton of CO2 for industrial processes such as ethanol production or natural gas processing. From $40-$120/t CO2 is the cost for processes like cement production and power generation.
The direct air capture approach is currently the most expensive one, but still plays a critical role in carbon removal. The range of cost is between $200-$600 depending on the technology choice and the scale of the deployment. Some carbon capture technologies are commercially available now, while others are still in development, which explains the large range in costs. New carbon capture methods are currently being explored to drive down expenses down to $30-$60 and below.
The industry offers a great growth potential and unlimited opportunities. According to the 2021 Carbon Capture Market report, the carbon capture and storage (CCS) market was valued at $3.36 billion in 2019 and is expected to reach $6.15 billion by 2027. Exxon forecasts it to be a 2 trillion market by 2040. As certain sectors like aviation, shipping and heavy industry are difficult to decarbonize, carbon capture technologies are deemed to play a key role in offsetting those emissions and support a faster transition.
Conclusion
Carbon capture is an essential technology that can reduce man-made emissions globally. A much greater capacity is needed so the world can be on track to meet the Paris Agreement net zero goal by 2050. The industry is projected to rise exponentially in the next few decades as the technology is viable in reducing emissions of hard-to-decarbonize industries. A reduction of costs and energy consumption associated with the carbon capture processes need to be overcome to achieve large scale deployment of these systems.
