Carbon Capture Technology
Today we are going to talk about carbon capture technology. Mainly we will have a discussion on the CCS which means Carbon capture and storage, CCU which is carbon capture and utilization, and try to see where carbon capture technology is standing at present.
Carbon capture is the process of capturing carbon dioxide and placing it into a storage device in such a way that it cannot further enter into the atmosphere.
There are a lot of industries or plants around us that emit a lot of carbon dioxide. By using carbon capture technology, we can prevent the emission of carbon dioxide from these sources into the atmosphere and hence can mitigate its contribution to global warming.
Carbon dioxide can directly be captured from the air. In addition, it can be captured from industrial sources with the help of technologies that are developed using simple methods like absorption or adsorption, gas separation method, etc.
It is surprisingly true that, by using carbon capture technologies, it is believed to be possible to reduce the emission of carbon dioxide up to 80% of what is generally emitted from an industry.
A recent trial of bio-energy with carbon capture and storage at a wood-fired unit in the UK started its run in 2019 which is capable of removing one thousand kilograms of carbon dioxide from the atmosphere.
The capturing of carbon dioxide is most readily possible at point sources like large fossil fuel plants, biomass energy plants, power generation plants, industries, gas processing plants, etc.
As we mentioned earlier, extracting carbon dioxide from the air is also possible. However, there is always a much lower concentration of carbon dioxide present in the air compared to the ones mentioned previously, which makes this extraction a much difficult task.
There are three different configurations of technologies for carbon dioxide capture. They are-
- pre-combustion and
- oxyfuel combustion
In post-combustion capture,
carbon dioxide produced from the burning of fossil fuels is removed.
pre-combustion capture is applied popularly in gaseous fuel and power production.
In this case, the fossil fuel is partially oxidized in a gasifier or something like that. The carbon monoxide from the syngas produced reacts with steam added and is converted into carbon dioxide and hydrogen. The hydrogen is used as fuel and the carbon dioxide is removed before combustion takes place.
Under the oxy-fuel combustion technology, the fuel is burned in oxygen instead of air. To control the temperatures of the produced flames, cooled flue gas is injected into the combustion chamber. The flue gas is mainly a mixture of carbon dioxide and water vapor. Water vapor is condensed through cooling and thus a nearly pure carbon dioxide stream can be stored.
Once the capturing is done, this carbon dioxide would have to be transported to a suitable storage site. This is how the idea of CCS (Carbon Capture and Storage) comes into being. This can be done using pipelines. But ships can also be used for transportation purposes. For long-distance transportation, ships would be more feasible than using pipelines.
Many forms have been brought about for storing carbon dioxide. Some of them are-
Gaseous storage in deep geological formations.
Solid storage where metal oxides react with carbon dioxide.
Storage that involves CO2- degrading algae or bacteria, etc.
Previously, it was thought that carbon dioxide can also be stored in the ocean, which is now no more under consideration as there remains a risk for ocean water to get acidified.
Geological formations are at present believed to be the most effective sequestration sites. Geo sequestration involves the injection of supercritical carbon dioxide into underground geological formations where the geochemical trapping mechanism plays the role of preventing carbon dioxide escape through the surface.
Again, as the carbon dioxide molecules can be absorbed in the surface of coal, coal seams can be used for storing carbon dioxide as well. However, anyone can raise questions over its feasibility and efficiency.
Carbon dioxide can physically be stored in containers with bacteria that can degrade carbon dioxide.
Crops and trees capable of absorbing carbon dioxide from the atmosphere can be grown. These crops might then be burnt inside a system from where gases produced due to burning would not come out.
Trees and plants use the energy of sunlight and through photosynthesis, they capture carbon dioxide from the air and release oxygen into the air. In addition to the carbon dioxide that trees capture, they can also help soil capture a mentionable amount of carbon.
In case of solid storage where metal oxides react with carbon dioxide, carbon dioxide exothermically reacts with metal oxides and ends up producing stable carbonates. This process requires a long period of time. However, the reaction rate can be made faster in various ways such as by using catalysts.
Now let us see what Carbon capture and utilization (CCU) is. It is the process of the captured carbon dioxide to be recycled for further usage. CCU aims to convert the captured carbon dioxide into more valuable substances or products, such as plastics, biofuel, etc. Converting the captured carbon dioxide into useful commercial products could make carbon capture financially significant. CCU can also play a vital role in reducing greenhouse gas emissions from major emitters.
Last but not least,
we must mention that figuring out how to adapt carbon capture technology is complicated. Building up such power stations or plants is very expensive. Building up such stations often needs a large donation from the governments of the countries or from the rich people all over the world. During the last few years, there have been quite a lot of investments in this sector. But it still remains a question whether we can come out with one such magical technology which is worth the investment.
Curtains down. Thank you.
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- Janine on Atomic Structure: Relation to Nucleon numbers । Isotopes and Isotopic Notation