Direct air carbon capture and storage DACCS

Industry

Permafrost patterns of tundra soil, Northeast Greenland National Park

The concentration of GHGs in the atmosphere will have to be stabilized or lowered to mitigate or even reverse current global warming. To achieve this, current GHG emissions need to be reduced. Such mitigation strategies will however take time to deploy, and some emission sources will be difficult to mitigate. Moreover, since current atmospheric levels are already having a major warming effect, negative emission or Carbon Dioxide Removal (CDR) measures that reduce the amount of GHGs in the atmosphere are an active topic of research.

Direct air carbon capture and storage (DACCS) aims to reduce the amount of carbon dioxide in the atmosphere by taking it directly out of the air, and removing it from the carbon cycle. Because the concentration of carbon dioxide in the air is relatively low, this involves huge ventilators that suck in large amounts of air. The carbon could then be removed from the passing air by sorbents. There are two main sorbent ideas currently being explored: absorption and adsorption, with the former dissolving the CO2 into it, and the latter adhering it to a substance. In both cases, the sorbent will release the CO2 again after energy is applied, allowing for the material to be reused. These systems therefore require significant amounts of energy, and they therefore should be coupled to renewable sources so as not to end up with net negative emissions.

The potential of cold areas like the northern and arctic regions is likely to be great for DACCS, as cold climates can provide significant benefits for the efficiency of certain technologies, and especially improve the recovery process after capturing the carbon from the air. The captured CO2 thereafter needs to be disposed of (see also Carbon capture and storage). There are several ways to do this, such as injecting it into basalt rock formations or underseas, or storing it in depleted gas fields. However, there are significant uncertainties about the large-scale feasibility of such injections, and storage underground requires monitoring to ensure no leaks occur. Alternatively, the captured carbon could be turned into resources or materials, although this raises questions about related climate effects and possible costs.

Technological Readiness Level (TRL)

Medium 2

There has been a lot of hype around DACCS, and commercial companies like ClimeWorks, Carbfix, Carbon Engineering, and Global Thermostat have been featured broadly. Many issues however still need to be resolved. The State of Carbon Dioxide Removal report therefore gives it a readiness level of 6 (Smith et al. 2023).

Technological Readiness Level (TRL)

A technology with a TRL of 4-6: TRL 4 – validated in lab; TRL 5 – validated in relevant environment; TRL 6 – demonstrated in relevant environment

Scalability

Medium 2

NASEM (2019) claims that DACCS offer one of the few technologies that could potentially ' be scaled up to remove very large amounts of carbon.' And the State of Carbon Dioxide Removal report estimating potential capture of 5 to 40 GtCO2/yr (Smith et al. 2023). However, given the very limited state of current DACCS systems, there would have to be a significant scaling up of activities (Powis et al, 2023). The issue of scalability is key, as Realmonte et al (2019) show in their model study that assuming DACCS to be scalable, and finding out they aren't, would lead to an overshoot of up to 0.8°C. One requirement for scaling would be a suitable financial system that would enable investment and deployment at scale (McCormick, 2022). Another issue related to the high energy demand of DACCS. This means that scaling up could lead to energy competition (Smith et al, 2023), with Hanna et al (2021) suggesting that they could consume 14% of global electricity by 2075.///Potentially DACCS could be built everywhere (Strefler et al 2021), with the provision that they have access to renewable energy (IPCC, AR6, wg3 12.3.1.1) Specific DACCS technologies would be more efficient in certain areas like colder regions.

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

Low 1

DACCS currently only removed 1% of total novel CDR technology removal of 2.1 million tonnes (see Smith et al, 2023). Given that 0.96 billion tonnes of extra carbon dioxide would be required to keep global warming below two degrees above pre-industrial levels, DACCS would need to be improved and scaled up very quickly to make a significant difference.

Timeliness for near-future effects

Implemented too late to make a significant difference

Northern + Arctic potential

High 3

Although the DACCS would reduce global atmospheric CO2 levels, specific DACCS systems are especially efficient in colder climates (Wilson, 2022), making the construction of DACCS in Northern and Arctic regions attractive (see also Antarctic air capture).

Northern + Arctic potential

Very detectable impacts in the Arctic, above the global average; technology ideally/preferably located here

Global potential

High 3

Fuss et all (2018) estimated that DACCS could potentially increase its potential uptake from 0.5 to 5 GtCO2 per year by 2050 to 40 GtCO2 year by the end of the century, this is a figure that is also given in the recent State of Carbon Dioxide Removal report (Smith et al, 2023), and the IPCC AR6 wg3 (2022).

Global potential

Major impacts detected

Cost - benefit

Medium 2

Because the technology is currently rapidly developed, the costs of DACCS could drop over the coming years, potentially greatly impacting the potential for this technology to be scaled up and used at scale (McQueen et al, 2021). Keith et al (2018) giving levelized costs of 94 to 232 USD per ton of CO2 from their pilot plant study. In 2018 Fuss et all estimated that costs per tonne CO2 would drop from 600-1000 to 100-300 dollars, and the State of Carbon Dioxide Removal report repeated this amount in 2023 (Smith et al, 2023). Möllersten and Naqvi’s review of CDR technologies (2022) notes a potential cost reduction from 100-1500 USD/t CO2 to 150-230 USD/tCO2. However the spread of estimates is significant (Sovacool et al, 2022). A major boost for the industry was the launch of a $3.5 billion US Government program in 2022 that included a $180 per ton tax credit and could significantly push down prices.

Cost - benefit

Significant investment costs needed, but still much cheaper than the avoided damage costs (e.g., 30%).

Environmental risks

Low 3

The environmental risks of DACCS are likely to be relatively low in comparison to other CDR methods, although Gambhir and Tavoni (2019) note that some uncertainties around this remain with regards to large scale deployment.

Environmental risks

Very limited, site-specific effects restricted to the solution deployment location only

Community impacts

Neutral 2

Günther and Ekardt (2022) note that although DACCS are less land intensive than BECCS, they could nevertheless impact human rights negatively, especially the right to energy due to their high energy demand.

Community impacts

Unnoticeable or negligible positive or negative effects

Ease of reversibility

Easy 3

Ease of reversibility

Easily reversible naturally

Risk of termination shock

Low 3

Risk of termination shock

Low or insignificant termination shock or damage

Legality/governance

High 3

Such systems are already operational and fall under national legislations.

Legality/governance

Currently legal to deploy, with governance structures in place to facilitate it and/or financial incentives to develop it

Scientific/media attention

High 3

DACCS are widely discussed and covered in both academia and in popular discourse, with companies like Carbfix and Climeworks being frequently covered. Major political interest in DACCS has also started to materialize, especially in the US (Scott-Buechler et al, 2023), as is also testified by the 2022 US government $3.5 billion program.

Scientific/media attention

Numerous scientific papers with substantial funding and ongoing research groups; significant media attention and "hype"; many companies exploring commercialization options

References

Cox, E., Spence, E., & Pidgeon, N. (2020). Public perceptions of carbon dioxide removal in the United States and the United Kingdom. Nature Climate Change, 10(8), 744-749. https://doi.org/10.1038/s41558-020-0823-z

Fuss, S.; Lamb, W.F.; Callaghan, M.W.; Hilaire, J.; Creutzig, F.; Amann, T.; Beringer, T.; De Oliveira Garcia, W.; Hartmann, J.; Khanna, T.; et al. Negative Emissions—Part 2: Costs, Potentials and Side Effects. Environ. Res. Lett. 2018, 13, 063002. https://doi.org?10.1088/1748-9326/aabf9f

Gambhir, A., & Tavoni, M. (2019). Direct air carbon capture and sequestration: how it works and how it could contribute to climate-change mitigation. One Earth, 1(4), 405-409. https://doi.org/10.1016/j.oneear.2019.11.006

Godin, J., Liu, W., Ren, S., & Xu, C. C. (2021). Advances in recovery and utilization of carbon dioxide: A brief review. Journal of Environmental Chemical Engineering, 9(4), 105644. https://doi.org/10.1016/j.jece.2021.105644

Günther, P., & Ekardt, F. (2022). Human Rights and Large-Scale Carbon Dioxide Removal: Potential Limits to BECCS and DACCS Deployment. Land, 11(12), 2153. https://doi.org/10.3390/land11122153

Hanna, R., Abdulla, A., Xu, Y., & Victor, D. G. (2021). Emergency deployment of direct air capture as a response to the climate crisis. Nature communications, 12(1), 368. https://doi.org/10.1038/s41467-020-20437-0

Kazemifar, F. (2022). A review of technologies for carbon capture, sequestration, and utilization: Cost, capacity, and technology readiness. Greenhouse Gases: Science and Technology, 12(1), 200-230. https://doi.org/10.1002/ghg.2131

Keith, D.W.; Holmes, G.; St. Angelo, D.; Heidel, K. A Process for Capturing CO2 from the Atmosphere. Joule 2018, 2, 1573–1594. https://doi.org/10.1016/j.joule.2018.05.006

McCormick C 2022 Who pays for DAC? The market and policy landscape for advancing direct air capture (National Academy of Engineering). Available at: www.nae.edu/266376/Who-Pays-for-DAC-The-Market-and-Policy-Landscape-for-Advancing-Direct-Air-Capture [Accessed 22 July 2024]

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), 032001. https://doi.org/10.1088/2516-1083/abf1ce

Möllersten, K., & Naqvi, R. (2022). Technology Readiness Assessment, Costs, and Limitations of five shortlisted NETs. Available at: https://www.researchgate.net/publication/359427009_Technology_Readiness_Assessment_Costs_and_Limitations_of_five_shortlisted_NETs_Accelerated_mineralisation_Biochar_as_soil_additive_BECCS_DACCS_Wetland_restoration [Accessed 22 July 2024].

Powis, C. M., Smith, S. M., Minx, J. C., & Gasser, T. (2023). Quantifying global carbon dioxide removal deployment. Environmental Research Letters. https://doi.org/10.1088/1748-9326/acb450

Realmonte, G., Drouet, L., Gambhir, A., Glynn, J., Hawkes, A., Köberle, A. C., & Tavoni, M. (2019). An inter-model assessment of the role of direct air capture in deep mitigation pathways. Nature communications, 10(1), 3277. https://doi.org/10.1038/s41467-019-10842-5

Scott-Buechler, Celina, Julia Jeanty, Catherine Fraser, Grace Adcox, and Charlotte Scott (2023). Advancing Equitable Deployment of Regional DAC Hubs. Data For Progress. Available at: https://www.dataforprogress.org/memos/advancing-equitable-deployment-of-regional-dac-hubs [Accessed 22 July 2024]

Smith, S. M., Geden, O., Nemet, G., Gidden, M., Lamb, W. F., Powis, C., Bellamy, R., Callaghan, M., Cowie, A., Cox, E., Fuss, S., Gasser, T., Grassi, G., Greene, J., Lück, S., Mohan, A., Müller-Hansen, F., Peters, G., Pratama, Y., Repke, T., Riahi, K., Schenuit, F., Steinhauser, J., Strefler, J., Valenzuela, J. M., and Minx, J. C. (2023). The State of Carbon Dioxide Removal - 1st Edition. The State of Carbon Dioxide Removal. https://doi.org/10.17605/OSF.IO/W3B4Z

Song, M., Rim, G., Kong, F., Priyadarshini, P., Rosu, C., Lively, R. P., & Jones, C. W. (2022). Cold-temperature capture of carbon dioxide with water coproduction from air using commercial zeolites. Industrial & Engineering Chemistry Research, 61(36), 13624-13634. https://doi.org/10.1021/acs.iecr.2c02041

Sovacool, B. K., Baum, C. M., Low, S., Roberts, C., & Steinhauser, J. (2022). Climate policy for a net-zero future: ten recommendations for Direct Air Capture. Environmental Research Letters, 17(7), 074014. https://doi.org/10.1088/1748-9326/ac77a4

Strefler, J.; Bauer, N.; Humpenöder, F.; Klein, D.; Popp, A.; Kriegler, E. Carbon Dioxide Removal Technologies Are Not Born Equal. Environ. Res. Lett. 2021, 16, 074021. https://doi.org/0.1088/1748-9326/ac0a11

Wilson, S. M. (2022). The potential of direct air capture using adsorbents in cold climates. Iscience, 25(12), 105564. https://doi.org/10.1016/j.isci.2022.105564

Related ideas

Shelf-Iceberg, North of Antarctic Peninsula

Ice sheets and glaciers

Ice sheet stabilization via buttressing

One of the potentially most catastrophic effects of contemporary global warming would be the dramatic increase in sea levels as a result of the melting Greenland and Antarctic ice sheets. Even if all current emissions were immediately stopped, sea level rise could still occur because of lockedin warming (State of the Cryosphere report 2022).

A school of juveniles of the Dusky spinefoot Siganus luridus (second)

Oceans & marine

Artificial upwelling

Oceans play an important role in global heat transfer and carbon storage processes. As global temperatures and atmospheric carbon levels rise, some have suggested artificially modifying the vertical movement of water to enhance these processes.

River Ölfusá just North of Selfoss, South Iceland

Oceans & marine

River Liming

The pH of water is lowered when it takes up atmospheric carbon. Given that the Earth’s oceans serve as a major carbon sink, there is increasing interest in the possibility to artificially increase the alkalinity of water to restore pH to previous levels, and/or increase carbon uptake potential.

Industry

Radiative covering and building technologies/ Passive daytime radiative cooling

An increase in GHGs in the atmosphere leads to a greater amount of outgoing infrared radiation from the earth being retained. There are several ideas to reduce the resulting warming by modifying surface radiation processes.

Blue Iceberg, Rødefjord, Northeast Greenland National Park

Sea ice & icebergs

Modular iceberg creation by submersibles

Arctic sea ice extent has rapidly decreased over the last few decades, with most multi-year ice disappearing altogether. This has already had major effects on local communities and ecosystems. The disappearance of the relatively reflective sea ice also leads to a dramatic decrease of albedo in the Arctic and subsequent high energy uptakes by the darker water during the Arctic summers.

Oceans & marine

Ocean fertilization

The oceans are the largest carbon sink for atmospheric carbon, and have taken up over 30% of anthropogenic emissions. Carbon uptake occurs abiotically through processes like ocean-atmosphere interaction and weathering processes, and biotically, mainly through carbon consuming photosynthesising organisms.

Cultivating algae for export to Japan, Zanzibar

Oceans & marine

Seaweed and macro algae cultivation

The potential of carbon sequestration by marine based plants such as mangroves, seagrass and algae, often referred to as blue carbon, and the importance of better understanding it, has clearly been recognised (Mcleod et al. 2011). The IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (2019) concluded blue carbon can play an important role in both climate regulation and adaptation. The term algae groups together several kinds of marine photosynthetic organisms. These are often subdivided into very small microalgae like phytoplankton, and larger macroalgae like kelp and seaweed. Although there is still large uncertainty about the total amount of carbon sequestered by these marine organisms, a recent estimate by Duarte et al. (2022) indicated that all macroalgae took in as much CO2 as the Amazon rainforest.

Land-based measures

Afforestation, reforestation and forest management

Although the rate of deforestation has slowed over the last few decades, the world is still losing forest cover (FAO 2020). Adequate management, protection, and restoration of existing forests, and the planting of unforested areas, play a crucial role in climate mitigation scenarios (IPCC AR6 WG3), and many countries now include forests in their climate mitigation targets (NDCs).The Northern and Arctic regions are essential in this endeavor since they are home to large swaths of boreal forests that make up 27% of total global forest area (FAO 2020).