5 Carbon Removal Technologies Explained
Carbon removal technologies include; direct air capture, bioremedial technology, induced absorption/adsorption, bioenergy with carbon capture and storage, and enhanced weathering.
This article discusses carbon removal technologies, as follows;
1). Direct Air Capture (as one of the Carbon Removal Technologies)
Direct air capture (DAC) is a mechanical engineering and chemical isolation technology that involves the use of active gas suction and element extraction to remove carbon dioxide from the air.
A direct air capture machine works by pulling streams of air through a reactive or absorbent medium that removes carbon from the air by physicochemical interaction with the air gases [7].
Based on the nature of the reactive medium, direct air capture can be classified into two types; which are liquid and solid direct air capture.
Liquid capture uses a liquid-phase chemical to react with, and isolate carbon dioxide, while solid capture uses solid-state filter membranes made from reactive materials, for carbon removal.
In direct air capture, efforts are usually made to ensure that low-carbon energy sources are used to power the equipment. Common options include renewable energy such as solar [3].
Waste energy can also be captured from cogeneration facilities and used.
The end-product of direct air capture is usually a concentrated stream of carbon [5], which can either be stored in geologic formations and other natural carbon sinks, or used as a raw material for industrial purposes.
Direct air capture is one of the most effective carbon removal technologies, as well as a highly recommendable component of any large-scale decarbonization strategy. It is however also energy-intensive and costly, compared to other carbon removal technologies.
2). Bioremedial Technology
Bioremedial technology covers all tools and techniques of bioremediation that are useful for carbon removal.
Two prominent bioremedial technologies are automated reforestation and ocean fertilization.
Automated reforestation is the use of artificial intelligence and automechanical engineering to plant trees. It is a highly-versatile, scalable, relatively-simple and inexpensive technique.
The advantage of automated reforestation can be attributed to the fact that it is effective for reversing or mitigating a broad range of environmental degradation cases, including climate change, desertification, deforestation, and pollution.
As a carbon removal technology, automated reforestation uses the efficiency and speed of drones to plant trees and establish artificial forests or other plant-dominated ecosystems [4].
These ecosystems once established, help to improve air quality by removing pollutants and greenhouse gases (including carbon dioxide); by exploiting the natural role of trees in establishing ecologic sustainability through photosynthesis, biodegradation, pollutant interception, nutrient cycling, and energy pyramid optimization.
Ocean fertilization (OF) is a combination of biotechnology and geological engineering, whereby large amounts of nutrients are introduced into the upper regions of the ocean, to increase the growth and photosynthetic activity of phytoplankton [8].
It may also be described as induced marine carbon sequestration, because the activities of these phytoplankton lead to the sequestration of atmospheric carbon dioxide, and its storage in the ocean.
3). Induced Absorption/Adsorption (as one of the Carbon Removal Technologies)
Induced absorption/adsorption is one of the most innovative and important carbon removal technologies.
It involves the use of physicochemical processes and reactions to isolate carbon dioxide from flue gas streams and other sources.
Adsorption itself makes use of a solid adsorbent, such as activated carbon, to isolate carbon dioxide which is drawn and adheres to the adsorbent. A common form of activated carbon used is biochar, whose effectiveness may be optimized using a catalyst like amine compounds [1].
Absorption usually involves a reactive liquid-phase chemical, or a filter layer, which actively extracts and absorbs carbon in gaseous streams.
Induced absorption/adsorption technology is usually categorized together with direct air capture. However the two technologies are different and only operate co-dependently.
4). Bioenergy with Carbon Capture and Storage
Bioenergy with carbon capture and storage (BECC or BECCUS), is a geological engineering technique which involves the isolation or capture, and storage, of carbon dioxide that is emitted in the process of harnessing bioenergy or producing biofuel.
BECC is commonly carried out in the process of biomass conversion, using carbon capture equipment that have been integrated into biorefineries or other similar systems [6].
The effectiveness of BECC technology depends on the design and components of the capture system, and the compatibility of these with the available bioenergy production feedstock, equipment and process.
Carbon dioxide which has been captured can be injected into subsurface geologic formations for storage.
5). Enhanced Weathering (as one of the Carbon Removal Technologies)
Enhanced weathering is a carbon capture method based on geological engineering, whereby large quantities of pulverized rock material are spread over extensive land surfaces or in oceans, in order to accelerate weathering rates and induce carbon sequestration [2].
Although effective, enhanced weathering is less-commonly utilized for decarbonization than other technologies like direct air capture.
The mechanism and principle behind enhanced weathering is acidification reversal/reduction. Namely, alkalinity is increased in natural carbon sinks like soil and oceans, by the introduction of fine rock particles into these media.
As a result, carbon affinity is also increased, while acidity is reduced, allowing more carbon to be captured and stored.
Conclusion
Carbon removal technologies are;
1. Direct Air Capture
2. Bioremedial Technology
3. Induced Absorption
4. Bioenergy with Carbon Capture and Storage
5. Enhanced Weathering
References
1). Alhassan, M.; Auta, M.; Sabo, J. K.; Musa, U.; Kovo, A. (2016). “CO2 Capture Using Amine-impregnated Activated Carbon from Jatropha curcas Shell.” Available at: 10.9734/BJAST/2016/24253. (Accessed 4 November 2022).
2). Bach, L. T.; Gill, S. J.; Rickaby, R.; Gore, S.; Renforth, P. (2019). “CO2 Removal With Enhanced Weathering and Ocean Alkalinity Enhancement: Potential Risks and Co-benefits for Marine Pelagic Ecosystems.” Frontiers in Climate 1:7. Available at: https://doi.org/10.3389/fclim.2019.00007. (Accessed 4 November 2022).
3). Breyer, C.; Fasihi, M.; Aghahosseini, A. (2020). “Carbon dioxide direct air capture for effective climate change mitigation based on renewable electricity: a new type of energy system sector coupling.” Mitigation and Adaptation Strategies for Global Change 25(7). Available at: https://doi.org/10.1007/s11027-019-9847-y. (Accessed 4 November 2022).
4). Elliott, S. (2016). “The potential for automating assisted natural regeneration of tropical forest ecosystems.” Biotropica 48(6):825-833. Available at: https://doi.org/10.1111/btp.12387. (Accessed 4 November 2022).
5). McQueen, N.; Gomes, K. V.; McCormick, C.; Blumanthal, K.; Pisciotta, M.; Wilcox, J. (2021). “A review of direct air capture (DAC): Scaling up commercial technologies and innovating for the future.” Progress in Energy 3(3). Available at: https://doi.org/10.1088/2516-1083/abf1ce. (Accessed 4 October 2022).
6). Michaga, M. F.; Michailos, S.; Akram, M.; Cardozo, E.; Hughes, K.; Ingham, D.; Pourkashanian, M. (2022). “Bioenergy with carbon capture and storage (BECCS) potential in jet fuel production from forestry residues: A combined Techno-Economic and Life Cycle Assessment approach.” Energy Conversion and Management 255(4):115346. Available at: https://doi.org/10.1016/j.enconman.2022.115346. (Accessed 4 November 2022).
7). Shi, X.; Xiao, H.; Azarabadi, H.; Song, J.; Wu, X.; Chen, X.; Lackner, K. S. (2019). “Sorbents for Direct Capture of CO2 from Ambient Air.” Angewandte Chemie International Edition 59(18). Available at: https://doi.org/10.1002/anie.201906756. (Accessed 4 November 2022).
8). Williamson, P.; Wallace, D. W.; Law, C. S.; Boyd, P. W.; Collos, Y.; Croot, P. L.; Denman, K. L.; Riebesell, U.; Takeda, S.; Vivian, C. (2012). “Ocean fertilization for geoengineering: A review of effectiveness, environmental impacts and emerging governance.” Process Safety and Environmental Protection 90(6):475-488. Available at: https://doi.org/10.1016/j.psep.2012.10.007. (Accessed 4 November 2022).
