Atmospheric Detox through Carbon Capture
What a benediction to society it would be to arrest the delinquents of this world and convert them to philanthropists?! The Avengers of the energy world have done just that – it is now possible to arrest pollutants from industrial chimneys, and what more – you can put them to good use.
Carbon Capture and Storage / Sequestration (CCS) is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting and storing it for future use. Usually, the CO2 is captured from large point sources, which are nothing but large sources of pollution, such as, chemical / power plants, and stored underground in geological formations, which are also known to enhance recovery in oil fields. Although the sequestration process helps stowing away the harmful CO2 to aid in the oil industry, it is still expensive in terms of the cost involved in the sequestration process in comparison to the yield of oil it could aid in. Hence, the more popular sequence to Carbon Capture is Utilization, by which the CO2 captured can be used to produce high-value chemicals that can effectively offset the high cost of capturing. (Link)
Capture
There are many ways to capture CO2 from industrial sources: Absorption, Adsorption, Chemical looping, Membrane gas separation, Gas hydration, etc. Capturing CO2 is most cost-effective at point sources, such as, cement / steel production, natural gas processing, synthetic fuel plants, fossil fuel-based hydrogen production plants, etc. Extracting CO2 from air is also possible, although the low percentage of CO2 in air makes it expensive to engineer a solution, and therefore, heavy industrial pollutants, such as the above mentioned sources are ideal to capture CO2 from. Usually, a scrubbing mechanism is employed to remove impurities from captured CO2, which yields upto 65% CO2 that can be sequestered in gaseous / solid form. Broadly, three different capture technologies exist: post-combustion, pre-combustion, and oxyfuel combustion, the difference being in the stage and adaptation of the process when CO2 is captured.
Sequestration
After capture, a transportation mechanism is needed to move the CO2 to suitable storage locations, for which pipelines are the cheapest form. Various approaches have been conceived for permanent storage of CO2. While solid storage by reaction of CO2 with metal oxides to form stable carbonates is one possibility, another is Geo-sequestration, which involves injecting CO2 into underground geological formations, such as, oil fields, gas fields, saline formations, and unmendable coal seams. Physical and geochemical trapping mechanisms prevent the CO2 gas from escaping to the surface of the Earth.
Utilization
Carbon Capture and Utilization (CCU) is the process of recycling the captured carbon for further usage. The CO2 captured can be converted to variable substances or products, such as, plastics, concrete or methanol, thereby avoiding storage, and the perils of leakage thereof. Although the processes to utilize CO2 to produce certain products are deemed expensive due to the external energy required, the hazard of releasing the CO2 into the atmosphere outweighs the costs involved. However, it makes absolute sense to employ external energy to convert CO2 to substances / products only if that energy is from a clean, and renewable source, since otherwise, there’s risk of releasing more CO2 into the atmosphere than originally intended.
Looking ahead
Although the technologies seem fancy and appear to solve the problem of climate change, retro-fitting the CCUS solutions to existing point sources is complex, with each project being unique in design, size and installed equipment, not to mention the requirement of supplementary energy to power the capture process. (Link) However, as of 2020, only about a thousandth of global CO2 emissions are captured by CCS. Hence, it’s plain to see that to achieve a ‘net-zero’ future, Carbon Capture plays a key role. In the UK, the government has included CCUS in its Green 10-point plan and has stated its aims to have at least one power CCUS project by 2030. In the US, Elon Musk recently launched a $100 million competition to find the best carbon capture technology. With heavy push-back from the environmental community due to the heavy energy and carbon penalties imposed by existing CCUS approaches, it can safely be stated that CCUS technologies are constantly evolving. (Link) Distant and elusive as it may seem, the dream for clean living shall manifest only through endeavours such as these. O Energy, green is thy colour.