Jump to content

Direct air capture

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Janine Yao (talk | contribs) at 18:19, 2 October 2024 (→Methods of capture). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Flow diagram of direct air capture process using sodium hydroxide as the absorbent and including solvent regeneration.
Flow diagram of direct air capture process using sodium hydroxide as the absorbent and including solvent regeneration
An example of what Direct Air Capture could look like and how the process works.

Direct air capture (DAC) is the use of chemical or physical processes to extract carbon dioxide directly from the ambient air.[1] If the extracted CO2 is then sequestered in safe long-term storage (called direct air carbon capture and sequestration (DACCS), the overall process will achieve carbon dioxide removal and be a "negative emissions technology" (NET).

The carbon dioxide (CO2) is captured directly from the ambient air; this is contrast to carbon capture and storage (CCS) which captures CO2 from point sources, such as a cement factory or a bioenergy plant.[2] After the capture, DAC generates a concentrated stream of CO2 for sequestration or utilization. Carbon dioxide removal is achieved when ambient air makes contact with chemical media, typically an aqueous alkaline solvent[3] or sorbents.[4] These chemical media are subsequently stripped of CO2 through the application of energy (namely heat), resulting in a CO2 stream that can undergo dehydration and compression, while simultaneously regenerating the chemical media for reuse.

When combined with long-term storage of CO2, DAC is known as direct air carbon capture and storage (DACCS or DACS[5]). DACCS can function as both a carbon dioxide removal mechanism or a carbon negative technology. As of 2023, DACCS has yet to be integrated into emissions trading because, at over US$1000,[6] the cost per ton of carbon dioxide is many times the carbon price on those markets.[7] For the end-to-end process to remain net carbon negative, DAC machines must be powered by renewable energy sources, since the process can be quite energy expensive. Future innovations may reduce the energy intensity of this process.

DAC was suggested in 1999 and is still in development.[8][9] Several commercial plants are planned or in operation in Europe and the US. Large-scale DAC deployment may be accelerated when connected with economical applications or policy incentives.

In contrast to carbon capture and storage (CCS) which captures emissions from a point source such as a factory, DAC reduces the carbon dioxide concentration in the atmosphere as a whole. Thus, DAC can be used to capture emissions that originated in non-stationary sources such as airplanes.[2]

Methods of capture

The International Energy Agency reported growth in direct air capture global operating capacity.[10]

There are the three stages of CO2 capture in DAC: the contacting stage, the capture stage, and the separation stage. In the contacting stage, the DAC system transports atmospheric air containing CO2 to the equipment using large-scale fans. Subsequently, in the CO2 capture stage, CO2 rapidly and effectively binds with liquid solvents in chemical reactors or solid sorbents in filters, which must possess binding energies equivalent to that of CO2. Later, in the CO2separation stage, external energy sources facilitate the separation of CO2 from the solvents or sorbents, yielding pure CO2 and regenerated solvents or sorbents. Following the completion of these three stages, the separated pure CO2 is either utilized or stored, while the recovered solvents or sorbents are recycled for reuse in the CO2 capture process [11].

Currently, liquid DAC (L-DAC) and solid DAC (S-DAC) represent two mature technologies for industrial deployment. Additionally, several emerging DAC technologies, including electro-swing adsorption (ESA), moisture-swing adsorption (MSA) , and membrane-based DAC (m-DAC), are in different stages of development, testing, or limited practical application[11].

More recently, Ireland-based company Carbon Collect Limited[12] has developed the MechanicalTree™ which simply stands in the wind to capture CO2. The company claims this 'passive capture' of CO2 significantly reduces the energy cost of Direct Air Capture, and that its geometry lends itself to scaling for gigaton CO2 capture.

Most commercial techniques use a liquid solvent—usually amine-based or caustic—to absorb CO2 from a gas.[13] For example, a common caustic solvent: sodium hydroxide reacts with CO2 and precipitates a stable sodium carbonate. This carbonate is heated to produce a highly pure gaseous CO2 stream.[14][15] Sodium hydroxide can be recycled from sodium carbonate in a process of causticizing.[16] Alternatively, the CO2 binds to solid sorbent in the process of chemisorption.[13] Through heat and vacuum, the CO2 is then desorbed from the solid.[15][17]

Among the specific chemical processes that are being explored, three stand out: causticization with alkali and alkali-earth hydroxides, carbonation,[18] and organic−inorganic hybrid sorbents consisting of amines supported in porous adsorbents.[8]

Other explored methods

The idea of using many small dispersed DAC scrubbers—analogous to live plants—to create environmentally significant reduction in CO2 levels, has earned the technology a name of artificial trees in popular media.[19][20][21]

Moisture swing sorbent

In a cyclical process designed in 2012 by professor Klaus Lackner, the director of the Center for Negative Carbon Emissions (CNCE), dilute CO2 can be efficiently separated using an anionic exchange polymer resin called Marathon MSA, which absorbs air CO2 when dry, and releases it when exposed to moisture. A large part of the energy for the process is supplied by the latent heat of phase change of water.[22] The technology requires further research to determine its cost-effectiveness.[23][24][25]

Metal-organic frameworks

Main article: Carbon dioxide scrubber § Metal-organic frameworks (MOFs)

Other substances which can be used are metal–organic frameworks (MOFs).[26]

Membranes

Membrane separation of CO2 rely on semi-permeable membranes. This method requires little water and has a smaller footprint.[13] Typically polymeric membranes, either glassy or rubbery, are used for direct air capture. Glassy membranes typically exhibit high selectivity with respect to Carbon Dioxide; however, they also have low permeabilities. Membrane capture of carbon dioxide is still in development and needs further research before it can be implemented on a larger scale.[27]

Environmental impact

Proponents of DAC argue that it is an essential component of climate change mitigation.[1][17][25] Researchers posit that DAC could help contribute to the goals of the Paris Agreement (namely limiting the increase in global average temperature to well below 2 °C above pre-industrial levels). However, others claim that relying on this technology is risky and might postpone emission reduction under the notion that it will be possible to fix the problem later,[9][28] and suggest that reducing emissions may be a better solution.[14][29]

DAC relying on amine-based absorption demands significant water input. It was estimated, that to capture 3.3 gigatonnes of CO2 a year would require 300 km3 of water, or 4% of the water used for irrigation. On the other hand, using sodium hydroxide needs far less water, but the substance itself is highly caustic and dangerous.[9]

DAC also requires much greater energy input in comparison to traditional capture from point sources, like flue gas, due to the low concentration of CO2.[14][28] The theoretical minimum energy required to extract CO2 from ambient air is about 250 kWh per tonne of CO2, while capture from natural gas and coal power plants requires, respectively, about 100 and 65 kWh per tonne of CO2.[14][1] Because of this implied demand for energy, some have proposed using "small nuclear power plants" connected to DAC installations.[9]

When DAC is combined with a carbon capture and storage (CCS) system, it can produce a negative emissions plant, but it would require a carbon-free electricity source. The use of any fossil-fuel-generated electricity would end up releasing more CO2 to the atmosphere than it would capture.[28] Moreover, using DAC for enhanced oil recovery would cancel any supposed climate mitigation benefits.[9][15]

Applications

Practical applications of DAC include:

These applications require different concentrations of CO2 product formed from the captured gas. Forms of carbon sequestration such as geological storage require pure CO2 products (concentration > 99%), while other applications such as agriculture can function with more dilute products (~ 5%). Since the air that is processed through DAC originally contains 0.04% CO2 (or 400 ppm), creating a pure product requires more energy than a dilute product and is thus typically more expensive.[22][31]

DAC is not an alternative to traditional, point-source carbon capture and storage (CCS), rather it is a complementary technology that could be utilized to manage carbon emissions from distributed sources, fugitive emissions from the CCS network, and leakage from geological formations.[1][29][14] Because DAC can be deployed far from the source of pollution, synthetic fuel produced with this method can use already existing fuel transport infrastructure.[30]

Cost

One of the largest hurdles to implementing DAC is the cost of separating CO2 and air.[31][32] As of 2023 it is estimated that the total system cost is over $1,000 per tonne of CO2.[6] Large-scale DAC deployment can be accelerated by policy incentives.[33]

Development

Carbon Engineering

Main article: Carbon Engineering

Carbon Engineering is a commercial DAC company founded in 2009 and backed, among others, by Bill Gates and Murray Edwards.[30][29] As of 2018, it runs a pilot plant in British Columbia, Canada, that has been in use since 2015[17] and is able to extract about a tonne of CO2 a day.[9][29] An economic study of its pilot plant conducted from 2015 to 2018 estimated the cost at $94–232 per tonne of atmospheric CO2 removed.[17][3]

Partnering with California energy company Greyrock, Carbon Engineering converts a portion of its concentrated CO2 into synthetic fuel, including gasoline, diesel, and jet fuel.[17][29]

The company uses a potassium hydroxide solution. It reacts with CO2 to form potassium carbonate, which removes a certain amount of CO2 from the air.[30]

Climeworks

Main article: Climeworks

Climeworks's first industrial-scale DAC plant, which started operation in May 2017 in Hinwil, in the canton of Zurich, Switzerland, can capture 900 tonnes of CO2 per year. To lower its energy requirements, the plant uses heat from a local waste incineration plant. The CO2 is used to increase vegetable yields in a nearby greenhouse.[34]

The company stated that it costs around $600 to capture one tonne of CO2 from the air.[35][13][need quotation to verify]

Climeworks partnered with Reykjavik Energy in Carbfix, a project launched in 2007. In 2017, the CarbFix2 project was started[36] and received funding from European Union's Horizon 2020 research program. The CarbFix2 pilot plant project runs alongside a geothermal power plant in Hellisheidi, Iceland. In this approach, CO2 is injected 700 meters under the ground and mineralizes into basaltic bedrock forming carbonate minerals. The DAC plant uses low-grade waste heat from the plant, effectively eliminating more CO2 than they both produce.[9][37]

On May 8, 2024, Climeworks activated the world's largest DAC planet named Mammoth in Iceland. It will be able to pull 36,000 tons of carbon from the atmosphere a year at full capacity, according to Climeworks, equivalent to taking around 7,800 gas-powered cars off the road for a year.[38]

Global Thermostat

Global Thermostat is private company founded in 2010, located in Manhattan, New York, with a plant in Huntsville, Alabama.[30] Global Thermostat uses amine-based sorbents bound to carbon sponges to remove CO2 from the atmosphere. The company has projects ranging from 40 to 50,000 tonnes per year.[39][verification needed][third-party source needed]

The company claims to remove CO2 for $120 per tonne at its facility in Huntsville.[30][dubious – discuss]

Global Thermostat has closed deals with Coca-Cola (which aims to use DAC to source CO2 for its carbonated beverages) and ExxonMobil which intends to start a DAC‑to‑fuel business using Global Thermostat's technology.[30]

Soletair Power

Soletair Power is a startup founded in 2016, located in Lappeenranta, Finland, operating in the fields of Direct Air Capture and Power-to-X. The startup is primarily backed by the Finnish technology group Wärtsilä. According to Soletair Power, its technology is the first to combine Direct Air Capture with buildings' HVAC systems. The technology captures CO2 from the air running through a building's existing ventilation units inside buildings for removing atmospheric CO2 while reducing the building's net emissions. The captured CO2 is mineralized to concrete, stored or utilized to create synthetic products like food, textile or renewable fuel. In 2020, Wärtsilä, together with Soletair Power and Q Power, created their first demonstration unit of Power-to-X[40] for Dubai Expo 2020, that can produce synthetic methane from captured CO2 from buildings.

Prometheus Fuels

Main article: Prometheus Fuels

Is a start-up company based in Santa Cruz which launched out of Y Combinator in 2019 to remove CO2 from the air and turn it into zero-net-carbon gasoline and jet fuel.[41][42] The company uses a DAC technology, adsorbing CO2 from the air directly into process electrolytes, where it is converted into alcohols by electrocatalysis. The alcohols are then separated from the electrolytes using carbon nanotube membranes, and upgraded to gasoline and jet fuels. Since the process uses only electricity from renewable sources, the fuels are carbon neutral when used, emitting no net CO2 to the atmosphere.

Heirloom Carbon Technologies

Heirloom's first direct air capture facility opened in Tracy, California, in November 2023. The facility can remove up to 1,000 U.S. tons of CO2 annually, which is then mixed into concrete using technologies from CarbonCure. Heirloom also has a contract with Microsoft in which the latter will purchase 315,000 metric tons of CO2 removal.[43]

Other companies

Innovations in Research

Within the research domain, the ETH Zurich team's development of a photoacid solution for direct air capture marks a significant innovation. This technology, still under refinement, stands out for its minimal energy requirements and its novel chemical process that enables efficient CO2 capture and release. This method's potential for scalability and its environmental benefits align it with ongoing efforts by other companies listed in this section, contributing to the global pursuit of effective and sustainable carbon capture solutions.[48]

See also

References

  1. ^ a b c d e European Commission. Directorate General for Research and Innovation; European Commission's Group of Chief Scientific Advisors (2018). Novel carbon capture and utilisation technologies. Publications Office. doi:10.2777/01532. ISBN 978-92-79-82006-9.[page needed]
  2. ^ a b Erans, María; Sanz-Pérez, Eloy S.; Hanak, Dawid P.; Clulow, Zeynep; Reiner, David M.; Mutch, Greg A. (2022). "Direct air capture: process technology, techno-economic and socio-political challenges". Energy & Environmental Science. 15 (4): 1360–1405. doi:10.1039/D1EE03523A. hdl:10115/19074. S2CID 247178548.
  3. ^ a b Keith, David W.; Holmes, Geoffrey; St. Angelo, David; Heide, Kenton (7 June 2018). "A Process for Capturing CO2 from the Atmosphere". Joule. 2 (8): 1573–1594. doi:10.1016/j.joule.2018.05.006.
  4. ^ Beuttler, Christoph; Charles, Louise; Wurzbacher, Jan (21 November 2019). "The Role of Direct Air Capture in Mitigation of Anthropogenic Greenhouse Gas Emissions". Frontiers in Climate. 1: 10. doi:10.3389/fclim.2019.00010.
  5. ^ Quarton, Christopher J.; Samsatli, Sheila (1 January 2020). "The value of hydrogen and carbon capture, storage and utilisation in decarbonising energy: Insights from integrated value chain optimisation" (PDF). Applied Energy. 257: 113936. Bibcode:2020ApEn..25713936Q. doi:10.1016/j.apenergy.2019.113936. S2CID 208829001.
  6. ^ a b "Carbon-dioxide-removal options are multiplying". The Economist. 20 November 2023.
  7. ^ "The many prices of carbon dioxide". The Economist. 20 November 2023.
  8. ^ a b Sanz-Pérez, Eloy S.; Murdock, Christopher R.; Didas, Stephanie A.; Jones, Christopher W. (12 October 2016). "Direct Capture of carbon dioxide from Ambient Air". Chemical Reviews. 116 (19): 11840–11876. doi:10.1021/acs.chemrev.6b00173. PMID 27560307.
  9. ^ a b c d e f g h i "Direct Air Capture (Technology Factsheet)" (PDF). Geoengineering Monitor. 24 May 2018. Archived (PDF) from the original on 26 August 2019. Retrieved 27 August 2019.
  10. ^ "Direct Air Capture / A key technology for net zero" (PDF). International Energy Agency (IEA). April 2022. p. 18. Archived (PDF) from the original on 10 April 2022.
  11. ^ a b Li, Guihe; Yao, Jia (2024-09). "Direct Air Capture (DAC) for Achieving Net-Zero CO2 Emissions: Advances, Applications, and Challenges". Eng. 5 (3): 1298–1336. doi:10.3390/eng5030069. ISSN 2673-4117. {{cite journal}}: Check date values in: |date= (help)CS1 maint: unflagged free DOI (link)
  12. ^ "Carbon Collect's MechanicalTree selected for US Department of Energy award". ASU News. 2 July 2021. Retrieved 9 December 2021.
  13. ^ a b c d Smit, Berend; Reimer, Jeffrey A.; Oldenburg, Curtis M.; Bourg, Ian C (2014). Introduction to carbon capture and sequestration. London: Imperial College Press. ISBN 9781783263295. OCLC 872565493.
  14. ^ a b c d e "Direct Air Capture of CO2 with Chemicals: A Technology Assessment for the APS Panel on Public Affairs" (PDF). APS physics. 1 June 2011. Archived (PDF) from the original on 3 September 2019. Retrieved 26 August 2019.
  15. ^ a b c Chalmin, Anja (16 July 2019). "Direct Air Capture: Recent developments and future plans". Geoengineering Monitor. Archived from the original on 26 August 2019. Retrieved 27 August 2019.
  16. ^ Sanz-Pérez, Eloy S.; Murdock, Christopher R.; Didas, Stephanie A.; Jones, Christopher W. (2016). "Direct Capture of CO2 from Ambient Air". Chemical Reviews. 116 (19): 11840–11876. doi:10.1021/acs.chemrev.6b00173. PMID 27560307. S2CID 19566110.
  17. ^ a b c d e f Service, Robert (7 June 2018). "Cost plunges for capturing carbon dioxide from the air". Science. doi:10.1126/science.aau4107. S2CID 242097184.
  18. ^ Nikulshina, V.; Ayesa, N.; Gálvez, M.E.; Steinfeld, A. (July 2008). "Feasibility of Na-based thermochemical cycles for the capture of CO2 from air—Thermodynamic and thermogravimetric analyses". Chemical Engineering Journal. 140 (1–3): 62–70. doi:10.1016/j.cej.2007.09.007.
  19. ^ Biello, David (16 May 2013). "400 PPM: Can Artificial Trees Help Pull CO2 from the Air?". Scientific American. Archived from the original on 4 September 2019. Retrieved 4 September 2019.
  20. ^ Burns, Judith (27 August 2009). "'Artificial trees' to cut carbon". BBC News | Science & Environment. Archived from the original on 14 August 2017. Retrieved 6 September 2019.
  21. ^ Freitas RA Jr. Diamond Trees (Tropostats): A Molecular Manufacturing Based System for Compositional Atmospheric Homeostasis. IMM Report No. 43, 10 Feb 2010; http://www.imm.org/Reports/rep043.pdf.
  22. ^ a b Lackner, Klaus S. (1 February 2013). "The thermodynamics of direct air capture of carbon dioxide". Energy. 50: 38–46. Bibcode:2013Ene....50...38L. doi:10.1016/j.energy.2012.09.012.
  23. ^ "Carbon Capture". Lenfest Center for Sustainable Energy. Archived from the original on 20 December 2012. Retrieved 6 September 2019.
  24. ^ Biello, David (16 May 2013). "400 PPM: Can Artificial Trees Help Pull CO2 from the Air?". Scientific American. Archived from the original on 4 September 2019. Retrieved 4 September 2019.
  25. ^ a b Schiffman, Richard (23 May 2016). "Why CO2 'Air Capture' Could Be Key to Slowing Global Warming". Yale E360. Archived from the original on 3 September 2019. Retrieved 6 September 2019.
  26. ^ Yarris, Lynn (17 March 2015). "A Better Way of Scrubbing CO2". News Center. Archived from the original on 25 December 2017. Retrieved 7 September 2019.
  27. ^ Castro-Muñoz, Roberto; Zamidi Ahmad, Mohd; Malankowska, Magdalena; Coronas, Joaquín (October 2022). "A new relevant membrane application: CO2 direct air capture (DAC)". Chemical Engineering Journal. 446: 137047. doi:10.1016/j.cej.2022.137047. hdl:10261/280157. S2CID 248930982.
  28. ^ a b c Ranjan, Manya; Herzog, Howard J. (2011). "Feasibility of air capture". Energy Procedia. 4: 2869–2876. Bibcode:2011EnPro...4.2869R. doi:10.1016/j.egypro.2011.02.193.
  29. ^ a b c d e f Vidal, John (4 February 2018). "How Bill Gates aims to clean up the planet". The Observer.
  30. ^ a b c d e f g h i Diamandis, Peter H. (23 August 2019). "The Promise of Direct Air Capture: Making Stuff Out of Thin Air". Singularity Hub. Archived from the original on 29 August 2019. Retrieved 29 August 2019.
  31. ^ a b c d Negative Emissions Technologies and Reliable Sequestration. 2019. doi:10.17226/25259. ISBN 978-0-309-48452-7. PMID 31120708. S2CID 134196575.[page needed]
  32. ^ Fasihi, Mahdi; Efimova, Olga; Breyer, Christian (July 2019). "Techno-economic assessment of CO2 direct air capture plants". Journal of Cleaner Production. 224: 957–980. doi:10.1016/j.jclepro.2019.03.086. S2CID 159399402.
  33. ^ Simon, Frédéric (23 November 2021). "LEAK: EU strategy seeks to remove carbon from atmosphere". www.euractiv.com. Retrieved 1 December 2021.
  34. ^ Doyle, Alister (11 October 2017). "From thin air to stone: greenhouse gas test starts in Iceland". Reuters. Archived from the original on 1 September 2019. Retrieved 4 September 2019.
  35. ^ Tollefson, Jeff (7 June 2018). "Sucking carbon dioxide from air is cheaper than scientists thought". Nature. 558 (7709): 173. Bibcode:2018Natur.558..173T. doi:10.1038/d41586-018-05357-w. PMID 29895915. S2CID 48355402.
  36. ^ "Public Update on CarbFix". Climeworks. 3 November 2017. Archived from the original on 26 August 2019. Retrieved 2 September 2019.
  37. ^ Proctor, Darrell (1 December 2017). "Test of Carbon Capture Technology Underway at Iceland Geothermal Plant". POWER Magazine. Archived from the original on 26 August 2019. Retrieved 4 September 2019.
  38. ^ Proctor, Darrell (8 May 2024). "The 'world's largest' vacuum to suck climate pollution out of the air just opened. Here's how it works". CNN. Retrieved 16 May 2024.
  39. ^ "Global Thermostat". Global Thermostat. Archived from the original on 9 November 2018. Retrieved 7 December 2018.
  40. ^ "Expo 2020 Dubai: The key to clean air inside Finland Pavilion? Carbon dioxide". gulfnews.com. 28 June 2021. Archived from the original on 28 July 2021. Retrieved 28 July 2021.
  41. ^ Service, Robert F. (3 July 2019). "This former playwright aims to turn solar and wind power into gasoline". Science | AAAS. Archived from the original on 6 October 2019. Retrieved 23 January 2020.
  42. ^ Brustein, Joshua (30 April 2019). "In Silicon Valley, the Quest to Make Gasoline Out of Thin Air". Bloomberg.com. Archived from the original on 29 January 2020. Retrieved 23 January 2020.
  43. ^ Plumer, Brad (9 November 2023). "In a U.S. First, a Commercial Plant Starts Pulling Carbon From the Air". The New York Times.
  44. ^ Clifford, Catherine (1 February 2021). "Carbon capture technology has been around for decades — here's why it hasn't taken off". CNBC. Archived from the original on 21 November 2021. Retrieved 21 November 2021.
  45. ^ Sigurdardottir, Ragnhildur; Rathi, Akshat (6 March 2021). "This startup has unlocked a novel way to capture carbon—by turning the fouling gas into rocks". Fortune. Archived from the original on 21 November 2021. Retrieved 21 November 2021.
  46. ^ Takahashi, Dean (25 February 2020). "Last Energy raises $3 million to fight climate change with nuclear energy". VentureBeat. Archived from the original on 12 January 2021. Retrieved 21 November 2021.
  47. ^ Patel, Prachi (28 May 2022). "Carbon-Removal Tech Grabs Elon Musk's Check Millions poured into XPrize effort to pull CO2 out of the sky". IEEE Spectrum. Archived from the original on 28 May 2022. Retrieved 16 June 2023.
  48. ^ Kazmer, Rick (10 April 2024). "Scientists make breakthrough in pollution removal with liquid that bubbles like cola: 'Our process … requires much less energy'". The Cool Down. Retrieved 14 April 2024.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Direct_air_capture&oldid=1249012317"