Carbon dioxide removal

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Planting trees is a means of carbon dioxide removal.

Carbon dioxide removal (CDR), also known as negative CO2 emissions, is a process in which carbon dioxide gas (CO2) is removed from the atmosphere and sequestered for long periods of time.[1][2][3] Similarly, greenhouse gas removal (GGR) or negative greenhouse gas emissions is the removal of greenhouse gases (GHGs) from the atmosphere by deliberate human activities, i.e., in addition to the removal that would occur via natural carbon cycle or atmospheric chemistry processes.[4] In the context of net zero greenhouse gas emissions targets,[5] CDR is increasingly integrated into climate policy, as a new element of mitigation strategies.[6] CDR and GGR methods are also known as negative emissions technologies (NET), and may be cheaper than preventing some agricultural greenhouse gas emissions.[7]

CDR methods include afforestation, agricultural practices that sequester carbon in soils, bio-energy with carbon capture and storage, ocean fertilization, enhanced weathering, and direct air capture when combined with storage.[2][8][9] To assess whether net negative emissions are achieved by a particular process, comprehensive life cycle analysis of the process must be performed.

A 2019 consensus report by the US National Academies of Sciences, Engineering, and Medicine (NASEM) concluded that using existing CDR methods at scales that can be safely and economically deployed, there is potential to remove and sequester up to 10 gigatons of carbon dioxide per year.[7] This would offset greenhouse gas emissions at about a fifth of the rate at which they are being produced.

In 2021 the Intergovernmental Panel on Climate Change (IPCC) said that emission pathways that limit globally averaged warming to 1.5 °C or 2 °C by the year 2100 assume the use of CDR approaches in combination with emission reductions.[10][11]


The Intergovernmental Panel on Climate Change defines CDR as:

Anthropogenic activities removing CO2 from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical sinks and direct air capture and storage, but excludes natural CO2 uptake not directly caused by human activities.[1]

The U.S.-based National Academies of Sciences, Engineering, and Medicine uses the term "negative emissions technology" with a similar definition.[7]

The concept of deliberately reducing the amount of CO2 in the atmosphere is often mistakenly classified with solar radiation management as a form of climate engineering[contradictory] and assumed to be intrinsically risky.[7][need quotation to verify] In fact, CDR addresses the root cause of climate change and is part of strategies to reduce net emissions and manage risks related to elevated atmospheric CO2 levels.[2][12]

Concepts using similar terminology[edit]

CDR can be confused with carbon capture and storage (CCS), a process in which carbon dioxide is collected from point-sources such as gas-fired power plants, whose smokestacks emit CO2 in a concentrated stream. The CO2 is then compressed and sequestered or utilized.[1] When used to sequester the carbon from a gas-fired power plant, CCS reduces emissions from continued use of the point source, but does not reduce the amount of carbon dioxide already in the atmosphere.

Potential for climate change mitigation[edit]

Using CDR in parallel with other efforts to reduce greenhouse gas emissions, such as deploying renewable energy, is likely to be less expensive and disruptive than using other efforts alone.[7] A 2019 consensus study report by NASEM assessed the potential of all forms of CDR other than ocean fertilization that could be deployed safely and economically using current technologies, and estimated that they could remove up to 10 gigatons of CO2 per year if fully deployed worldwide.[7] This is one-fifth of the 50 gigatons of CO2 emitted per year by human activities.[7] In the IPCC's 2018 analysis of ways to limit climate change, all analyzed mitigation pathways that would prevent more than 1.5 °C of warming included CDR measures.[13]

Some mitigation pathways propose achieving higher rates of CDR through massive deployment of one technology, however these pathways assume that hundreds of millions of hectares of cropland are converted to growing biofuel crops.[7] Further research in the areas of direct air capture, geologic sequestration of carbon dioxide, and carbon mineralization could potentially yield technological advancements that make higher rates of CDR economically feasible.[7]

The IPCC's 2018 report said that reliance on large-scale deployment of CDR would be a "major risk" to achieving the goal of less than 1.5 °C of warming, given the uncertainties in how quickly CDR can be deployed at scale.[13] Strategies for mitigating climate change that rely less on CDR and more on sustainable use of energy carry less of this risk.[13][14] The possibility of large-scale future CDR deployment has been described as a moral hazard, as it could lead to a reduction in near-term efforts to mitigate climate change.[15][7] The 2019 NASEM report concludes:

Any argument to delay mitigation efforts because NETs will provide a backstop drastically misrepresents their current capacities and the likely pace of research progress.[7]

Carbon sequestration[edit]

Forests, kelp beds, and other forms of plant life absorb carbon dioxide from the air as they grow, and bind it into biomass. However, these biological stores are considered volatile carbon sinks as the long-term sequestration cannot be guaranteed. For example, natural events, such as wildfires or disease, economic pressures and changing political priorities can result in the sequestered carbon being released back into the atmosphere.[16]

Carbon dioxide that has been removed from the atmosphere can also be stored in the Earth's crust by injecting it into the subsurface, or in the form of insoluble carbonate salts (mineral sequestration). This is because they are removing carbon from the atmosphere and sequestering it indefinitely and presumably for a considerable duration (thousands to millions of years).


Afforestation, reforestation, and forestry management[edit]

According to the International Union for Conservation of Nature: "Halting the loss and degradation of natural systems and promoting their restoration have the potential to contribute over one-third of the total climate change mitigation scientists say is required by 2030."[17]

Forests are vital for human society, animals and plant species. This is because trees keep air clean, regulate the local climate and provide a habitat for numerous species. Trees and plants convert carbon dioxide back into oxygen, using photosynthesis. They are important for regulating CO2 levels in the air, as they remove and store carbon from the air. Without them, the atmosphere would heat up quickly and destabilise the climate.[18]

Increased use of wood in construction is being considered.[19]


Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by continual or enhanced biological processes. This form of carbon sequestration occurs through increased rates of photosynthesis via land-use practices such as reforestation, sustainable forest management, and genetic engineering. The SALK Harnessing Plants Initiative led by Joanne Chory is an example of an enhanced photosynthesis initiative[20][21] Carbon sequestration through biological processes affects the global carbon cycle.

Agricultural practices[edit]

Measuring soil respiration on agricultural land

Carbon farming is a name for a variety of agricultural methods aimed at sequestering atmospheric carbon into the soil and in crop roots, wood and leaves. The aim of carbon farming is to increase the rate at which carbon is sequestered into soil and plant material with the goal of creating a net loss of carbon from the atmosphere.[22] Increasing a soil's organic matter content can aid plant growth, increase total carbon content, improve soil water retention capacity[23] and reduce fertilizer use.[24][25] As of 2016, variants of carbon farming reached hundreds of millions of hectares globally, of the nearly 5 billion hectares (1.2×1010 acres) of world farmland.[26][27] In addition to agricultural activities, forests management is also a tool that is used in carbon farming.[28] The practice of carbon farming is often done by individual land owners who are given incentive to use and to integrate methods that will sequester carbon through policies created by governments.[29] Carbon farming methods will typically have a cost, meaning farmers and land-owners need a way to profit from the use of carbon farming, and different governments will have different programs.[29]

Potential sequestration alternatives to carbon farming include scrubbing CO2 from the air with machines (direct air capture); fertilizing the oceans to prompt algal blooms that after death carry carbon to the sea bottom;[30] storing the carbon dioxide emitted by electricity generation; and crushing and spreading types of rock such as basalt that absorb atmospheric carbon.[25] Land management techniques that can be combined with farming include planting/restoring forests, burying biochar produced by anaerobically converted biomass and restoring wetlands (such as marshes and peatlands).[31]

Wetland restoration[edit]

Estimates of the economic value of blue carbon ecosystems per hectare. Based on 2009 data from UNEP/GRID-Arendal.[32][33]
Blue carbon is carbon sequestration (the removal of carbon dioxide from the earth's atmosphere) by the world's oceanic and coastal ecosystems, mostly by algae, seagrasses, macroalgae, mangroves, salt marshes and other plants in coastal wetlands. This occurs through plant growth and the accumulation and burial of organic matter in the soil. Because oceans cover 70% of the planet, ocean ecosystem restoration has the greatest blue carbon development potential. Research is ongoing, but in some cases it has been found that these types of ecosystems remove far more carbon than terrestrial forests, and store it for millennia.

Bioenergy with carbon capture & storage[edit]

Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere.[34] The carbon in the biomass comes from the greenhouse gas carbon dioxide (CO2) which is extracted from the atmosphere by the biomass when it grows. Energy is extracted in useful forms (electricity, heat, biofuels, etc.) as the biomass is utilized through combustion, fermentation, pyrolysis or other conversion methods. Some of the carbon in the biomass is converted to CO2 or biochar which can then be stored by geologic sequestration or land application, respectively, enabling carbon dioxide removal (CDR) and making BECCS a negative emissions technology (NET).[35]

The IPCC Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), suggests a potential range of negative emissions from BECCS of 0 to 22 gigatonnes per year.[36] As of 2019, five facilities around the world were actively using BECCS technologies and were capturing approximately 1.5 million tonnes per year of CO2.[37] Wide deployment of BECCS is constrained by cost and availability of biomass.[38][39]


Biochar is created by the pyrolysis of biomass, and is under investigation as a method of carbon sequestration. Biochar is a charcoal that is used for agricultural purposes which also aids in carbon sequestration, the capture or hold of carbon. It is created using a process called pyrolysis, which is basically the act of high temperature heating biomass in an environment with low oxygen levels. What remains is a material known as char, similar to charcoal but is made through a sustainable process, thus the use of biomass.[40] Biomass is organic matter produced by living organisms or recently living organisms, most commonly plants or plant based material.[41] A study done by the UK Biochar Research Center has stated that, on a conservative level, biochar can store 1 gigaton of carbon per year. With greater effort in marketing and acceptance of biochar, the benefit could be the storage of 5–9 gigatons per year of carbon in biochar soils.[42][better source needed]

Enhanced weathering[edit]

Enhanced weathering is a chemical approach to remove carbon dioxide involving land- or ocean-based techniques. One example of a land-based enhanced weathering technique is in-situ carbonation of silicates. Ultramafic rock, for example, has the potential to store from hundreds to thousands of years' worth of CO2 emissions, according to estimates.[43][44] Ocean-based techniques involve alkalinity enhancement, such as grinding, dispersing, and dissolving olivine, limestone, silicates, or calcium hydroxide to address ocean acidification and CO2 sequestration.[45] One example of a research project on the feasibility of enhanced weathering is the CarbFix project in Iceland.[46][47][48]

Direct air capture[edit]

The International Energy Agency reported growth in direct air capture global operating capacity.[49]
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.

Direct air capture (DAC),is a process of capturing carbon dioxide (CO2) directly from the ambient air (as opposed to capturing from point sources, such as a cement factory or biomass power plant) and generating a concentrated stream of CO2 for sequestration or utilization or production of carbon-neutral fuel and windgas. Carbon dioxide removal is achieved when ambient air makes contact with chemical media, typically an aqueous alkaline solvent[50] or sorbents.[51] 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.

DAC was suggested in 1999 by Klaus S. Lackner and is still in development,[52][53] though several commercial plants are in operation or planning across Europe and the US. Large-scale DAC deployment may be accelerated when connected with economical use cases, or policy incentives.

DAC is not an alternative to traditional, point-source carbon capture and storage (CCS), but can be used to recapture some emissions from distributed sources, such as some rocket launches.[54] When combined with long-term storage of CO2, DAC is known as direct air carbon capture and storage (DACCS). DACCS can act as a carbon dioxide removal mechanism, although as of 2022 it has yet to be profitable because the cost per tonne of carbon dioxide is several times the carbon price.

Ocean fertilization[edit]

sequestration in the ocean
Ocean fertilization or ocean nourishment is a type of climate engineering based on the purposeful introduction of nutrients to the upper ocean[55] to increase marine food production[56] and to remove carbon dioxide from the atmosphere. A number of techniques, including fertilization by iron, urea and phosphorus, have been proposed. But research in the early 2020s suggested that it could only permanently sequester a small amount of carbon.[57] Therefore, there is no major future in its role to sequester carbon.

Magnesium silicate/oxide in cement[edit]

Lifecycle amounts are not yet fully understood.[19]


Economic issues[edit]

The cost of CDR differs substantially depending on the maturity of the technology employed as well as the economics of both voluntary carbon removal markets and the physical output; for example, the pyrolysis of biomass produces biochar that has various commercial applications, including soil regeneration and wastewater treatment.[58] In 2021 DAC cost from $250 to $600 per ton, compared to $100 for biochar and less than $50 for nature-based solutions, such as reforestation and afforestation.[59][60] The fact that biochar commands a higher price in the carbon removal market than nature-based solutions reflects the fact that it is a more durable sink with carbon being sequestered for hundreds or even thousands of years while nature-based solutions represent a more volatile form of storage, which risks related to forest fires, pests, economic pressures and changing political priorities.[61] The Oxford Principles for Net Zero Aligned Carbon Offsetting states that to be compatible with the Paris Agreement: “…organizations must commit to gradually increase the percentage of carbon removal offsets they procure with the view of exclusively sourcing carbon removals by mid-century.”[62] These initiatives along with the development of new industry standards for engineered carbon removal, such as the Puro Standard, will help to support the growth of the carbon removal market.[63]

In 2021, businessman Elon Musk announced he was donating $100m for a prize for best carbon capture technology.[64]

Although CDR is not covered by the EU Allowance as of 2021, the European Commission is preparing for carbon removal certification and considering carbon contracts for difference.[65][66] CDR might also in future be added to the UK Emissions Trading Scheme.[19] As of end 2021 carbon prices for both these cap-and-trade schemes currently based on carbon reductions, as opposed to carbon removals, remained below $100.[67][68]

In April 2022, a private sector aliance led by Stripe with prominent members including Meta, Google and Shopify, revealed a nearly $1 billion dollar fund to reward companies able to permanently capture & store carbon. According to senior Stripe employee Nan Ransohoff, the new fund "is roughly 30 times the carbon-removal market that existed in 2021. But it’s still 1,000 times short of the market we need by 2050.” [69]

Removal of other greenhouse gases[edit]

Although some researchers have suggested methods for removing methane, others say that nitrous oxide would be a better subject for research due to its longer lifetime in the atmosphere.[70]

See also[edit]


  • IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)].


  1. ^ a b c Intergovernmental Panel on Climate Change. "Glossary — Global Warming of 1.5 ºC". Archived from the original on December 22, 2019. Retrieved February 23, 2020.
  2. ^ a b c "Geoengineering the climate: science, governance and uncertainty". The Royal Society. 2009. Archived from the original on October 23, 2019. Retrieved September 10, 2011.
  3. ^ Minx, Jan C; Lamb, William F; Callaghan, Max W; Fuss, Sabine; Hilaire, Jérôme; Creutzig, Felix; Amann, Thorben; Beringer, Tim; De Oliveira Garcia, Wagner; Hartmann, Jens; Khanna, Tarun; Lenzi, Dominic; Luderer, Gunnar; Nemet, Gregory F; Rogelj, Joeri; Smith, Pete; Vicente Vicente, Jose Luis; Wilcox, Jennifer; Del Mar Zamora Dominguez, Maria (2018). "Negative emissions: Part 1 – research landscape and synthesis" (PDF). Environmental Research Letters. 13 (6): 063001. Bibcode:2018ERL....13f3001M. doi:10.1088/1748-9326/aabf9b. Archived from the original on March 16, 2020. Retrieved September 13, 2019.
  4. ^ IPCC, 2021: Annex VII: Glossary [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. MassonDelmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press. In Press. Archived September 5, 2021, at the Wayback Machine
  5. ^ Geden, Oliver (May 2016). "An actionable climate target". Nature Geoscience. 9 (5): 340–342. Bibcode:2016NatGe...9..340G. doi:10.1038/ngeo2699. ISSN 1752-0908. Archived from the original on May 25, 2021. Retrieved March 7, 2021.
  6. ^ Schenuit, Felix; Colvin, Rebecca; Fridahl, Mathias; McMullin, Barry; Reisinger, Andy; Sanchez, Daniel L.; Smith, Stephen M.; Torvanger, Asbjørn; Wreford, Anita; Geden, Oliver (March 4, 2021). "Carbon Dioxide Removal Policy in the Making: Assessing Developments in 9 OECD Cases". Frontiers in Climate. 3: 638805. doi:10.3389/fclim.2021.638805. ISSN 2624-9553.
  7. ^ a b c d e f g h i j k National Academies of Sciences, Engineering (October 24, 2018). Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. ISBN 978-0-309-48452-7. Archived from the original on November 20, 2021. Retrieved February 22, 2020.
  8. ^ Vergragt, P.J.; Markusson, N.; Karlsson, H. (2011). "Carbon capture and storage, bio-energy with carbon capture and storage, and the escape from the fossil-fuel lock-in". Global Environmental Change. 21 (2): 282–92. doi:10.1016/j.gloenvcha.2011.01.020.
  9. ^ Azar, C.; Lindgren, K.; Larson, E.; Möllersten, K. (2006). "Carbon Capture and Storage from Fossil Fuels and Biomass – Costs and Potential Role in Stabilizing the Atmosphere". Climatic Change. 74 (1–3): 47–79. Bibcode:2006ClCh...74...47A. doi:10.1007/s10584-005-3484-7. S2CID 4850415.
  10. ^ Page 4-81, IPCC Sixth Assessment Report Working Group 1, 9/8/21, Archived August 11, 2021, at the Wayback Machine
  11. ^ IPCC15, Ch 2.
  12. ^ Obersteiner, M.; Azar, Ch; Kauppi, P.; Möllersten, K.; Moreira, J.; Nilsson, S.; Read, P.; Riahi, K.; Schlamadinger, B.; Yamagata, Y.; Yan, J. (October 26, 2001). "Managing Climate Risk". Science. 294 (5543): 786–787. doi:10.1126/science.294.5543.786b. PMID 11681318. S2CID 34722068.
  13. ^ a b c "SR15 Technical Summary" (PDF). Archived (PDF) from the original on December 20, 2019. Retrieved July 25, 2019.
  14. ^ Anderson, K.; Peters, G. (October 14, 2016). "The trouble with negative emissions". Science. 354 (6309): 182–183. Bibcode:2016Sci...354..182A. doi:10.1126/science.aah4567. hdl:11250/2491451. ISSN 0036-8075. PMID 27738161. S2CID 44896189. Archived from the original on November 22, 2021. Retrieved April 28, 2020.
  15. ^ IPCC15 & Ch. 2 p. 124.
  16. ^ Myles, Allen (September 2020). "The Oxford Principles for Net Zero Aligned Carbon Offsetting" (PDF). Archived (PDF) from the original on October 2, 2020. Retrieved December 10, 2021.
  17. ^ "Forests and climate change". IUCN. November 11, 2017. Archived from the original on October 9, 2020. Retrieved October 7, 2020.
  18. ^ "Forest Protection & Climate Change: Why Is It Important?". Climate Transform. May 13, 2021. Archived from the original on June 3, 2021. Retrieved May 31, 2021.
  19. ^ a b c "Greenhouse Gas Removals: Summary of Responses to the Call for Evidence" (PDF). Archived (PDF) from the original on October 20, 2021.
  20. ^ Beerling, David (2008). The Emerald Planet: How Plants Changed Earth's History. Oxford University Press. pp. 194–5. ISBN 978-0-19-954814-9.
  21. ^ National Academies Of Sciences, Engineering (2019). Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, D.C.: National Academies of Sciences, Engineering, and Medicine. pp. 45–136. doi:10.17226/25259. ISBN 978-0-309-48452-7. PMID 31120708. S2CID 134196575.
  22. ^ Nath, Arun Jyoti; Lal, Rattan; Das, Ashesh Kumar (January 1, 2015). "Managing woody bamboos for carbon farming and carbon trading". Global Ecology and Conservation. 3: 654–663. doi:10.1016/j.gecco.2015.03.002. ISSN 2351-9894.
  23. ^ "Carbon Farming | Carbon Cycle Institute". Retrieved April 27, 2018.
  24. ^ "Carbon Farming: Hope for a Hot Planet – Modern Farmer". Modern Farmer. March 25, 2016. Retrieved April 25, 2018.
  25. ^ a b Velasquez-Manoff, Moises (April 18, 2018). "Can Dirt Save the Earth?". The New York Times. ISSN 0362-4331. Retrieved April 28, 2018.
  26. ^ "Excerpt | The Carbon Farming Solution". Retrieved April 27, 2018.
  27. ^ Burton, David. "How carbon farming can help solve climate change". The Conversation. Retrieved April 27, 2018.
  28. ^ Jindal, Rohit; Swallow, Brent; Kerr, John (2008). "Forestry-based carbon sequestration projects in Africa: Potential benefits and challenges". Natural Resources Forum. 32 (2): 116–130. doi:10.1111/j.1477-8947.2008.00176.x. ISSN 1477-8947.
  29. ^ a b Tang, Kai; Kragt, Marit E.; Hailu, Atakelty; Ma, Chunbo (May 1, 2016). "Carbon farming economics: What have we learned?". Journal of Environmental Management. 172: 49–57. doi:10.1016/j.jenvman.2016.02.008. ISSN 0301-4797. PMID 26921565.
  30. ^ Ortega, Alejandra; Geraldi, N.R.; Alam, I.; Kamau, A.A.; Acinas, S.; Logares, R.; Gasol, J.; Massana, R.; Krause-Jensen, D.; Duarte, C. (2019). "Important contribution of macroalgae to oceanic carbon sequestration". Nature Geoscience. 12 (9): 748–754. Bibcode:2019NatGe..12..748O. doi:10.1038/s41561-019-0421-8. hdl:10754/656768. S2CID 199448971.
  31. ^ Lehmann, Johannes; Gaunt, John; Rondon, Marco (March 1, 2006). "Bio-char Sequestration in Terrestrial Ecosystems – A Review". Mitigation and Adaptation Strategies for Global Change. 11 (2): 403–427. CiteSeerX doi:10.1007/s11027-005-9006-5. ISSN 1381-2386. S2CID 4696862.
  32. ^ Nellemann, Christian et al. (2009): Blue Carbon. The Role of Healthy Oceans in Binding Carbon. A Rapid Response Assessment. Arendal, Norway: UNEP/GRID-Arendal
  33. ^ Macreadie, P.I., Anton, A., Raven, J.A., Beaumont, N., Connolly, R.M., Friess, D.A., Kelleway, J.J., Kennedy, H., Kuwae, T., Lavery, P.S. and Lovelock, C.E. (2019) "The future of Blue Carbon science". Nature communications, 10(1): 1–13. doi:10.1038/s41467-019-11693-w.
  34. ^ Obersteiner, M. (2001). "Managing Climate Risk". Science. 294 (5543): 786–7. doi:10.1126/science.294.5543.786b. PMID 11681318. S2CID 34722068.
  35. ^ National Academies of Sciences, Engineering (October 24, 2018). Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. doi:10.17226/25259. ISBN 978-0-309-48452-7. PMID 31120708. S2CID 134196575. Archived from the original on May 25, 2020. Retrieved February 22, 2020.
  36. ^ Smith, Pete; Porter, John R. (July 2018). "Bioenergy in the IPCC Assessments". GCB Bioenergy. 10 (7): 428–431. doi:10.1111/gcbb.12514.
  37. ^ "BECCS 2019 perspective" (PDF). Archived (PDF) from the original on March 31, 2020. Retrieved June 11, 2019.
  38. ^ Rhodes, James S.; Keith, David W. (2008). "Biomass with capture: Negative emissions within social and environmental constraints: An editorial comment". Climatic Change. 87 (3–4): 321–8. Bibcode:2008ClCh...87..321R. doi:10.1007/s10584-007-9387-4.
  39. ^ Grantham 2019, p. 10
  40. ^ "What is biochar?". UK Biochar research center. University of Edinburgh Kings Buildings Edinburgh. Archived from the original on October 1, 2019. Retrieved April 25, 2016.
  41. ^ "What is Biomass?". Biomass Energy Center. Archived from the original on October 3, 2016. Retrieved April 25, 2016.
  42. ^ "Biochar reducing and removing CO2 while improving soils: A significant sustainable response to climate change" (PDF). UKBRC. UK Biochar research Center. Archived (PDF) from the original on November 5, 2016. Retrieved April 25, 2016.
  43. ^ "Maps show rocks ideal for sequestering carbon". The New York Times. Archived from the original on May 16, 2018. Retrieved May 15, 2018.
  44. ^ U.S. Department of the Interior. "Mapping the Mineral Resource Base for Mineral Carbon-Dioxide Sequestration in the Conterminous United States" (PDF). U.S. Geological Survey. Data Series 414. Archived (PDF) from the original on July 27, 2020. Retrieved May 15, 2018.
  45. ^ "Cloud spraying and hurricane slaying: how ocean geoengineering became the frontier of the climate crisis". The Guardian. June 23, 2021. Archived from the original on June 23, 2021. Retrieved June 23, 2021.
  46. ^ "CarbFix Project | Global Carbon Capture and Storage Institute". Archived from the original on July 3, 2018. Retrieved May 15, 2018.
  47. ^ "The CarbFix Project". (in Icelandic). August 22, 2017. Archived from the original on May 16, 2018. Retrieved May 15, 2018.
  48. ^ "Turning Carbon Dioxide Into Rock, and Burying It". The New York Times. February 9, 2015. ISSN 0362-4331. Archived from the original on May 16, 2018. Retrieved May 15, 2018.
  49. ^ "Direct Air Capture / A key technology for net zero" (PDF). International Energy Agency (IEA). April 2022. p. 18. Archived (PDF) from the original on April 10, 2022.
  50. ^ Keith, David W.; Holmes, Geoffrey; St. Angelo, David; Heide, Kenton (June 7, 2018). "A Process for Capturing CO2 from the Atmosphere". Joule. 2 (8): 1573–1594. doi:10.1016/j.joule.2018.05.006.
  51. ^ Beuttler, Christoph; Charles, Louise; Wurzbacher, Jan (November 21, 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.
  52. ^ Sanz-Pérez, Eloy S.; Murdock, Christopher R.; Didas, Stephanie A.; Jones, Christopher W. (October 12, 2016). "Direct Capture of carbon dioxide from Ambient Air". Chemical Reviews. 116 (19): 11840–11876. doi:10.1021/acs.chemrev.6b00173. PMID 27560307.
  53. ^ "Direct Air Capture (Technology Factsheet)" (PDF). Geoengineering Monitor. May 24, 2018. Archived (PDF) from the original on August 26, 2019. Retrieved August 27, 2019.
  54. ^ "How the billionaire space race could be one giant leap for pollution". the Guardian. July 19, 2021. Retrieved February 14, 2022.
  55. ^ Matear, R. J. & B. Elliott (2004). "Enhancement of oceanic uptake of anthropogenic CO2 by macronutrient fertilization". J. Geophys. Res. 109 (C4): C04001. Bibcode:2004JGRC..10904001M. doi:10.1029/2000JC000321. Archived from the original on March 4, 2010. Retrieved January 19, 2009.
  56. ^ Jones, I.S.F. & Young, H.E. (1997). "Engineering a large sustainable world fishery". Environmental Conservation. 24 (2): 99–104. doi:10.1017/S0376892997000167.
  57. ^ "Cloud spraying and hurricane slaying: how ocean geoengineering became the frontier of the climate crisis". The Guardian. June 23, 2021. Archived from the original on June 23, 2021. Retrieved June 23, 2021.
  58. ^ "How Finland's plans to scale up carbon removal to help the world reach net zero emissions". European CEO. July 1, 2021. Archived from the original on July 1, 2021.
  59. ^ Lebling, Katie; McQueen, Noah; Pisciotta, Max; Wilcox, Jennifer (January 6, 2021). "Direct Air Capture: Resource Considerations and Costs for Carbon Removal". Archived from the original on May 13, 2021. Retrieved May 13, 2021. {{cite journal}}: Cite journal requires |journal= (help)
  60. ^ Brown, James (February 21, 2021). "New Biochar technology a game changer for carbon capture market". The Land. Archived from the original on February 21, 2021. Retrieved December 10, 2021.
  61. ^ Myles, Allen (February 2020). "The Oxford Principles for Net Zero Aligned Carbon Offsetting" (PDF). Archived (PDF) from the original on October 2, 2020. Retrieved December 10, 2020.
  62. ^ Myles, Allen (September 2020). "The Oxford Principles for Net Zero Aligned Carbon Offsetting" (PDF). Archived (PDF) from the original on October 2, 2020. Retrieved December 10, 2021.
  63. ^ Giles, Jim (February 10, 2020). "Carbon markets get real on removal". Archived from the original on February 15, 2020. Retrieved December 10, 2021.
  64. ^ @elonmusk (January 21, 2021). "Am donating $100M towards a prize for best carbon capture technology" (Tweet) – via Twitter.
  65. ^ Tamme, Eve; Beck, Larissa Lee (2021). "European Carbon Dioxide Removal Policy: Current Status and Future Opportunities". Frontiers in Climate. 3: 120. doi:10.3389/fclim.2021.682882. ISSN 2624-9553.
  66. ^ Elkerbout, Milan; Bryhn, Julie. "Setting the context for an EU policy framework for negative emissions" (PDF). Centre for European Policy Studies. Archived (PDF) from the original on December 10, 2021.
  67. ^ Evans, Michael (December 8, 2021). "Spotlight: EU carbon price strengthens to record highs in November". Retrieved December 10, 2021.
  68. ^ "Pricing Carbon". The World Bank. Archived from the original on June 2, 2014. Retrieved December 20, 2021.
  69. ^ Robinson Meyer (April 23, 2022). "We've Never Seen a Carbon-Removal Plan Like This Before". The Atlantic. Retrieved April 29, 2022.
  70. ^ Lackner, Klaus S. (2020). "Practical constraints on atmospheric methane removal". Nature Sustainability. 3 (5): 357. doi:10.1038/s41893-020-0496-7. ISSN 2398-9629.

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