Direct air capture

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Direct air capture ( DAC ) is a process for extracting carbon dioxide (CO 2 ) directly from the ambient air . The basic principle is that ambient air flows through a filter that extracts part of the CO 2 . As with Carbon Capture and Utilization , the result of the process is pure CO 2 , which can then be used for various purposes. Because of this property, such plants were referred to as "artificial trees".

Possible uses of the CO 2 are the material use as raw material z. B. for the chemical industry, the production of CO 2 -neutral fuels ( RE gas and e-fuels ) as well as the geological storage of carbon dioxide, whereby negative emissions can be achieved. The latter is known as Direct Air Carbon Capture and Storage ( DACCS ) and is intended to actively remove the climate gas carbon dioxide from the atmosphere and to store it permanently using Carbon Capture and Storage (CCS) in order to counteract global warming .

history

The DAC concept was first proposed by Klaus Lackner in 1999 and experienced rapid development in the 2010s. But it is still in the development stage.

Procedure

Flow diagram of the direct air trapping process using sodium hydroxide as an absorbent including solvent regeneration.
Flow diagram of the direct air filtration process using sodium hydroxide as an absorbent and with solvent regeneration.

To extract CO 2 , large fans are required to force the ambient air through a filter. The filter is located in the amine wash , a liquid solvent selected from organic amines , in other methods as is CO 2 - absorber , for example, sodium hydroxide is used, the CO 2 to sodium carbonate reacted. This is heated to release high-purity gaseous CO 2 . Sodium hydroxide is recycled from sodium carbonate. Alternatively, the CO 2 binds to solid sorbents in the chemisorption process. In the next step, the CO 2 is desorbed from the solid by means of heat and vacuum . Among the specific chemical processes that are being investigated, three should be highlighted: absorption with alkali and alkaline earth hydroxides, carbonation, and organic-inorganic hybrid sorbents consisting of amines such as monoethanolamine (MEA) diethanolamine (DEA) or methyldiethanolamine (DMEA), which Adsorbents present on a porous carrier . The amine scrubbing is also used to filter out pure CO 2 from point sources (exhaust gases) in which the CO 2 is present in higher concentrations.

Low concentration CO 2 can also be separated with an anion exchange polymer resin called Marathon MSA . This substance absorbs air-CO 2 in a dry state and releases it again in a moist state. The technology requires further research to determine its economics.

Other substances that can be used are metal organic frameworks (MOFs).

Membrane separations of CO 2 rely on semipermeable membranes to separate CO 2 from air. This method differs from the other two in that it requires little water and has a smaller footprint.

economics

One of the biggest hurdles in implementing DAC is the cost of separating CO 2 from the air. According to a 2011 study, a facility to capture one megaton of CO 2 would cost $ 2.2 billion a year. Other studies from the same period put the cost of DAC at $ 200–1000 per ton of CO 2 and $ 600 per ton.

In a 2015-2018 economic study of a pilot facility in British Columbia, Canada, the cost was estimated at $ 94-232 per ton of atmospheric CO 2 removed . This study was carried out by Carbon Engineering , which is financially interested in commercializing DAC technology.

As of 2011, CO 2 capture costs for hydroxide-based processes were generally around $ 150 per tonne of CO 2 . The current separation based on liquid amines is 10 to 35 USD per ton of CO 2 . The costs for adsorption-based CO 2 separation are between 30 and 200 USD per ton of CO 2 . It is difficult to determine the specific cost of DAC because each of the methods has large differences in terms of the regeneration of the sorbent used and its cost.

development

Carbon engineering

Carbon Engineering is a commercial DAC company founded in 2009 by Bill Gates and Murray Edwards , among others . Since 2015 it has been operating a pilot plant in British Columbia, Canada , which can extract around one tonne of CO 2 per day. An economic study of their pilot plant conducted from 2015 to 2018 put the costs at USD 94 to 232 per ton of atmospheric CO 2 removed .

Working with Californian energy company Greyrock, they convert some of its concentrated CO 2 into synthetic fuel , including gasoline, diesel and Jet-A jet fuel.

The company uses a potassium hydroxide solution to absorb the CO 2 , which, like the sodium hydroxide mentioned above, forms potassium carbonate .

Climeworks

The first large-scale DAC system from Climeworks went into operation in May 2017. In Hinwil , Canton Zurich, 900 tons of CO 2 can be bound per year. In order to reduce energy consumption, the system uses the heat from a local waste incineration plant. The CO 2 is used to increase the vegetable yield in a nearby greenhouse.

The company said it costs around $ 600 to remove a ton of CO 2 from the air.

Climeworks is a partnership with Reykjavik Energy. The CarbFix project was started in 2007 . The CarbFix2 project was started in 2017 and received funding from the European Union's Horizon 2020 research program . The CarbFix2 pilot project runs next to a geothermal power plant in Hellisheidi , Iceland. With this approach, CO 2 is injected 700 meters underground, where it mineralizes basalt bedrock to form carbonate minerals. In the DAC system, inferior waste heat from the geothermal power plant is used, which saves more CO 2 than both produce.

Global thermostat

Global Thermostat is a privately held company founded in 2010 in Manhattan , New York with a plant in Huntsville, Alabama . Global Thermostat uses carbon-based amines sorbents attached to carbon sponges to remove CO 2 from the atmosphere. The company has projects ranging from large-scale extraction at 50,000 tons per year to small projects at 40 tons per year.

The company claims to be removing CO 2 at its Huntsville facility for $ 120 per tonne.

Global Thermostat has signed contracts with a beverage manufacturer (with whom DAC will generate CO 2 for its carbonated beverages) and an oil company that plans to pioneer DAC-to-fuel with Global Thermostat's technology. It is about the production of fuels with the carbon obtained from DAC.

other companies

  • Infinitree - formerly known as Kilimanjaro Energy and Global Research Technologym part of the US Carbon Sink . Demonstration of a pre-prototype of an economically viable DAC technology in 2007.
  • SkyTree - a company in the Netherlands,
  • UK Carbon Capture and Storage Research Center ,
  • Antecy - a Dutch company founded in 2010,

DACCS

DAC is also seen as a promising climate protection technology. When DAC is combined with a CCS system , this technology can produce negative emissions and thus help to achieve the goals of the Paris Climate Agreement . At the same time, scientists point out that DACCS cannot be a substitute for rapid climate protection measures in the present, as there is no guarantee that DACCS can be used sufficiently in the long term. The development and implementation of DACCS systems should not lead to the climate protection efforts being weakened in the hope of future successes of the DACCS technology. The development of DACCS should be promoted, but this should not lead to DACCS being used instead of other climate protection options, but together with them.

However, the prerequisite for the creation of negative emissions is that a carbon-free energy source is available for the operation of the DACCS systems. The use of electrical energy generated with fossil fuels , on the other hand, would ultimately release more CO 2 into the atmosphere than would be captured at the same time. A disadvantage of DACCS is the high energy consumption of the technology. Due to the low concentration of CO 2 in the air, DAC requires a much larger amount of energy compared to conventional extraction from point sources such as flue gas . The theoretical minimum energy required to extract CO 2 from the ambient air is approx. 250 kWh per ton of CO 2 , while separation from natural gas and coal-fired power plants requires approx. 100 or 65 kWh per ton of CO 2 . Because of this implicit energy demand, some geoengineering proponents have suggested using "small nuclear power plants" to power DAC systems, which could potentially create a whole host of new environmental impacts.

DAC, which relies on amine-based absorption, also has significant water requirements. It has been estimated that 300 km³ of water are required to capture 3.3 gigatons of CO 2 per year, or 4% of the water is used for irrigation . On the other hand, using sodium hydroxide requires much less water, but the substance itself is highly corrosive and dangerous. Overall, the water consumption of DACCS is about a factor of 10 or more below the water consumption of BECCS . In addition, the area consumption of DACCS, especially in comparison to the area-intensive use of BECCS, is minimal and is 0.001 ha / ton of CO 2 eq per year. Like BECCS, DACCS also requires the presence of secure geological CO 2 stores, also with regard to the risk of leakages and induced earthquakes.

The removal of atmospheric carbon dioxide by DACCS systems is probably significantly more expensive than traditional climate protection options for decarbonising the economy due to the high material costs. Even with significant cost reductions, DACCS systems would therefore in all probability only be built when practically all significant point sources of fossil carbon dioxide emissions have stopped releasing CO 2 .

A potential use of DAC for an improved oil yield would also cancel out the climate protection benefits.

Web links

Individual evidence

  1. ↑ David Biello: 400 PPM: Can Artificial Trees Help Pull CO2 from the Air? , May 16, 2013; Accessed October 2, 2019
  2. ↑ Bernd Schlupeck: Artificial trees go into series
  3. ↑ Can forests with artificial trees save the climate?
  4. ↑ Jie Bao et al .: Greenhouses for CO2 sequestration from atmosphere . In: Carbon Resources Conversion . tape 1 , 2018, p. 183–190 , doi : 10.1016 / j.crcon.2018.08.002 .
  5. ^ A b E. S. Sanz-Pérez, CR Murdock, SA Didas, CW Jones: Direct Capture of CO2 from Ambient Air . In: Chem Rev.. . 116, No. 19, August 25, 2016, pp. 11840-11876. doi : 10.1021 / acs.chemrev.6b00173 . PMID 27560307 .
  6. ↑ a b c d e Direct Air Capture (Technology Factsheet) ( en-US ) In: Geoengineering Monitor . May 24, 2018. Retrieved August 27, 2019.
  7. ↑ a b c Berend Smit, Jeffrey A. Reimer, Curtis M. Oldenburg, Ian C. Bourg: Introduction to carbon capture and sequestration . London 2014, ISBN 978-1-78326-329-5 .
  8. ↑ a b c d e Direct Air Capture of CO2 with Chemicals: A Technology Assessment for the APS Panel on Public Affairs . In: APS physics . June 1, 2011. Retrieved August 26, 2019.
  9. ↑ a b c d Anja Chalmin: Direct Air Capture: Recent developments and future plans ( en-US ) In: Geoengineering Monitor . July 16, 2019. Retrieved August 27, 2019.
  10. ↑ a b c d e Robert F. Service: Cost plunges for capturing carbon dioxide from the air. In: sciencemag.org. Science - AAAS, June 7, 2018, accessed August 26, 2019 .
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  12. ^ Carbon capture . In: Lenfest Center for Sustainable Energy . Archived from the original on December 20, 2012. Retrieved September 6, 2019.
  13. ↑ David Biello: 400 PPM: Can Artificial Trees Help Pull CO2 from the Air? ( en ) In: Scientific American . May 16, 2013. Retrieved September 4, 2019.
  14. ↑ a b Richard Schiffman: Why CO2 'Air Capture' Could Be Key to Slowing Global Warming ( en-US ) In: Yale E360 . May 23, 2016. Retrieved September 6, 2019.
  15. ↑ Lynn Yarris: A Better Way of Scrubbing CO2 ( en-US ) In: News Center . March 17, 2015. Retrieved September 7, 2019.
  16. ↑ a b c Novel carbon capture and utilization technologies: research and climate aspects . (PDF) In: Science Advice for Policy by European Academies (SAPEA) . May 23, 2018, ISSN  2568-4434 , p. 50. doi : 10.26356 / carboncapture .
  17. ↑ a b Kenton Heidel, David St Angelo, Geoffrey Holmes, David W. Keith: A Process for capturing CO2 from the atmosphere . In: Joule . tape 2 , no. 8 , 2018, ISSN  2542-4785 , p. 1573–1594 , doi : 10.1016 / j.joule.2018.05.006 .
  18. ↑ a b c d e Peter H. Diamandis: The Promise of Direct Air Capture: Making Stuff Out of Thin Air ( en-US ) In: Singularity Hub . August 23, 2019. Retrieved August 29, 2019.
  19. ^ A b c John Vidal: How Bill Gates aims to clean up the planet . In: The Observer . February 4, 2018, ISSN  0029-7712 ( theguardian.com ).
  20. ↑ Alister Doyle: From thin air to stone: greenhouse gas test starts in Iceland (en) . In: Reuters , October 11, 2017. Retrieved September 4, 2019. 
  21. ↑ Jeff Tollefson: Sucking carbon dioxide from air is cheaper than scientists thought . In: Nature . June 7, 2018. Retrieved August 26, 2019.
  22. ↑ Public Update on CarbFix ( en-GB ) November 3, 2017. Accessed September 2, 2019.
  23. ↑ a b Darrell Proctor: Test of Carbon Capture Technology Underway at Iceland Geothermal Plant (en-US) . In: Power Magazine , December 1, 2017. Retrieved September 4, 2019. 
  24. ↑ Global Thermostat ( en-US ) In: Global Thermostat . Retrieved December 7, 2018.
  25. ^ First Successful Demonstration of Carbon Dioxide Air Capture Technology Achieved by Columbia University Scientist and Private Company . In: Columbia University . April 24, 2007. Archived from the original on June 22, 2010. Retrieved on August 30, 2019.
  26. ↑ Home ( en ) In: ANTECY . Retrieved August 27, 2019.
  27. ↑ Giulia Realmonte et al .: An inter-model assessment of the role of direct air capture in deep mitigation pathways . In: Nature Communications . tape 10 , no. 3277 , 2019, doi : 10.1038 / s41467-019-10842-5 .
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