As global warming and climate change forecasts have worsened, carbon dioxide emissions have garnered increasing amounts of attention. In my own discussions of this subject, I have been asked is there not some way to take carbon dioxide back out of the air. The answer is yes, there is a way, and that way is carbon removal.

Types of Carbon Removal

Carbon removal fortuitously is a broad category encompassing a variety of strategies for removing carbon dioxide from the atmosphere. These strategies fall into one of three categories- nature-based, technological, and hybrid. Nature-based carbon removal strategies include reforestation, afforestation, and agricultural soil management. Ocean-based carbon removal constitutes a hybrid strategy. Technological strategies include direct air capture.

Distinguishing Direct Air Capture From Carbon Capture and Storage

Direct air capture is distinguishable from a similar but different technology, carbon capture and storage. One of the more common types of carbon capture and storage involves fossil fuel power plants and industrial facilities capturing carbon dioxide as it is produced and before it enters the atmosphere. An example of this would be a smokestack scrubber. In contrast, direct air capture removes carbon dioxide already present in the air. Some call previously emitted carbon dioxide legacy carbon, acknowledging that once emitted carbon dioxide can remain in the atmosphere for hundreds of years.

Carbon capture and storage is sometimes referred to as carbon capture, utilization and storage to reflect that some applications of this technology involve utilization rather than storage. An example of this is using the captured carbon dioxide for carbonating beverages. In another utilization, enhanced oil recovery, oil companies inject captured carbon dioxide into wells to assist with the production of oil. While the carbon dioxide obtained through direct air capture can be used for beverage carbonization and enhanced oil recovery, the design of direct air capture appears to emphasize durably storing the carbon dioxide geologically.

How Does Direct Air Capture Work?

At direct air capture facilities, air passes through dozens of massive fans. The carbon dioxide present in the air is absorbed by filters through a process of chemical reaction (which is aided by carbon dioxide’s tendency to bind easily with other materials). Once carbon dioxide fills a filter, heat will be applied to release the carbon dioxide from the filter. If the captured carbon dioxide is not being used for another purpose, it is mixed with water, transported, and piped into geological reservoirs to be durably stored deep underground. With the passage of several years, the carbon dioxide reacts with rocks and through mineralization hardens into presumably permanent formations.

Direct Air Capture Facilities

Few direct air capture facilities exist. A new direct air capture facility, Orca, opened last September in southwest Iceland. Climeworks, a Swiss company, operates the plant and powers it using a nearby geothermal vent. The company stores the carbon dioxide it captures in basalt rock formations underground. Climeworks operates smaller direct air capture facilities in Europe. Yet, according to the International Energy Agency, there are worldwide just 19 direct air capture plants operating. Carbon Engineering, a Canadian company, operates a direct air capture plant in Squamish, British Columbia and has plans, in partnership with Occidental Petroleum, for another in Texas with operations beginning in 2024. Carbon Engineering also plans to open a direct air capture plant in Scotland the following year.

Criticisms

While, as noted above, direct air capture is distinguishable from carbon capture and storage (CCS) and carbon capture, utilization and storage (CCUS), they are similar enough for criticisms of CCS and CCUS to be leveled against direct air capture. Given this, it is useful to examine criticisms of CCS and CCUS.

CCS and CCUS Criticisms

Critics argue that CCS and CCUS allow companies emitting carbon dioxide to continue to do so and at the same time claim they are cleaning up the environment. In fact, such companies are only capturing a portion of the carbon dioxide they produce. Similarly, detractors assert that because CCS and CCUS allow companies to claim they are cleaning up the environment, these technologies perpetuate the use of fossil fuel. Moreover, the use of captured carbon dioxide for enhanced oil recovery results in the production of more oil. Given these outcomes, critics of CCS and CCUS claim that government support of these technologies amounts to a subsidy for the fossil fuel industry.

The first two criticisms above do not apply to direct air capture. Direct air capture does not capture carbon dioxide as it is being produced. Direct air capture facilities are constructed for the purpose of removing carbon dioxide that is already present in the air. The third criticism above regarding perpetuation could be applied to direct air capture. However, the percentage of fossil fuel facility emissions that consists of carbon dioxide can be as much as 500 times greater than the percentage of carbon dioxide in the atmosphere. Therefore direct air capture cannot readily be cited as a justification for perpetuating the use of fossil fuel. It is true that carbon dioxide obtained through direct air capture may be used for enhanced oil recovery, but direct air capture facilities appear designed instead for storage. Conversely, one could view government support of direct air capture as a subsidy for the fossil fuel industry to the extent one views direct air capture as in fact perpetuating that industry, or if the direct air capture carbon dioxide is used for enhanced oil recovery.

Direct Air Capture Criticisms

Direct air capture does have disadvantages. It is a relatively new technology and therefore lacks a demonstrable performance history. Direct air capture is also very expensive. Presently the price for this technology is $600 to $800 per ton of carbon dioxide. Components for direct air capture facilities are made manually rather than through automation, which contributes considerably to this price. In addition, the operations of the facilities require significant energy, the cost of which adds to the price for this technology. The use of significant energy in the operation of direct air facilities also draws criticism. In addition, proponents of renewable energy assert that government support for direct air capture reduces government support for energy from sources like solar and wind.

Addressing Criticisms

As predictions for global warming and climate change have intensified, nations have endeavored to increase their efforts to prevent the worst of these predictions from becoming reality. In the U.S., the current administration has adopted the ambitious goal of net-zero emissions (with the amount of carbon dioxide being released into the atmosphere equal to the amount being removed) by 2050. The difficulty of achieving that goal, as well as the enormity of the problem it targets, warrant that all possible solutions for global warming and climate change be pursued. This assessment of the current situation undercuts the assertion among direct air capture critics that federal support for direct air capture reduces federal support for renewable energy. While some observers view the “pie” of federal support for all of these efforts to be of fixed size, others do not. Moreover, dealing effectively with carbon dioxide will mean not only reducing some carbon dioxide emissions and eliminating others but also removing carbon dioxide that is already in the atmosphere.

Concern about the large amount of energy required to operate direct air capture facilities can be resolved by using renewable energy sources, as is done with the Orca facility in Iceland. Scaling up will expand the technology’s track record. By scaling up, direct air capture technology can also attempt to address its high price. The technology will benefit from economies of scale through increasing the number, size, and capacity of direct air facilities, as well as adopting assembly-line industrialization for components. Such efforts, according to at least one industry executive, will reduce the price of carbon dioxide obtained through direct air capture to $200 to $300 per ton by the end of this decade and to $100 to $150 per ton at the end of the next, thereby rendering the technology competitive. Likewise some analysts think it possible that direct air capture will enjoy the steep cost declines experienced by wind and solar technologies.

Support for Direct Air Capture

Direct air capture technology has garnered increased support of late from both the public and private sectors. In March of last year, the U.S. Department of Energy (DOE) announced that it would provide $24 million for direct air capture research. On November 5, DOE launched its Carbon Negative Shot, which aims to remove gigatons of carbon dioxide from the atmosphere and durably store it for less than $100 per ton. The following week, DOE stated its intention, through an initiative named CarbonSAFE, to fund research and development of carbon dioxide geologic storage sites with minimum capacities of 50 million metric tons. Perhaps most significantly, the November 15 Infrastructure Investment and Jobs Act appropriated $3.5 billion for a program to build four regional direct air capture hubs, as well as a total of $115 million for two direct air capture technology prize competitions. Similarly, direct air capture technology should also benefit from the Appropriations Act of 2022, which provides an additional $45 million for carbon capture, removal, utilization, and storage technologies. Direct air capture technology can also obtain public support through the 45Q tax credit, which provides $50 per ton of carbon dioxide permanently stored.

The private sector is also steadily increasing its support for direct air capture technology. Climeworks, the Swiss company which operates Orca, raised the equivalent of $110 million in private investment during 2020 and $650 million in 2022. Microsoft invested in Orca through its climate innovation fund, and United Airlines is investing directly in direct air capture. Some of the private support for direct air capture comes in the form of carbon offset purchases (which compensate for carbon dioxide emissions) by companies like Microsoft, Swiss Re, Shopify, and Stripe.

Prospects for the Future

While direct air capture technology is not without its critics and disadvantages, significant levels of private and public sector support increase the likelihood of direct air capture scaling up and reducing its costs. In turn, those developments would greatly increase the technology’s viability and could lead to it becoming a substantial part of the carbon removal industry. If this promising technology can reach its full potential, the world will have a tool for significant carbon dioxide removal. The resulting removal of carbon dioxide from the atmosphere would reduce global warming and better enable us to steward our livable planet into the future.

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