Carbon Dioxide Removal: Can It Be Effective?
from Energy Security and Climate Change Program

Carbon Dioxide Removal: Can It Be Effective?

A facility in Iceland sequesters carbon in minerals deep underground.
A facility in Iceland sequesters carbon in minerals deep underground. Marco Djurica/Reuters

Governments and companies are embracing new emissions-reducing technologies that pull carbon dioxide out of the atmosphere. But it is uncertain whether this can work at the scale and in the time necessary to avert climate calamity.

March 29, 2024 10:38 am (EST)

A facility in Iceland sequesters carbon in minerals deep underground.
A facility in Iceland sequesters carbon in minerals deep underground. Marco Djurica/Reuters
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Carbon dioxide pollution in the atmosphere reached an all-time high last year—424 parts per million. That is likely the highest level since three million years ago, when trees grew in the polar regions and sea levels were up to twenty meters higher. Meanwhile, scientists warn that unless heating caused by the accumulation of carbon dioxide and other greenhouse gases is contained, the planet is hurtling toward a catastrophic increase in global average temperatures. That could affect ocean circulation, unleash sustained sea level rise, and kill coral reefs.

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One climate solution gaining governmental and private sector attention is carbon dioxide removal, or CDR. The question remains whether it will work at the scale and in the time necessary to avert climate calamity.

What is CDR?

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CDR includes technologies and processes that pull carbon from the atmosphere and then durably store it in the ground, vegetation, oceans, or aquifers. CDR only refers to intentional human activity, including nature-based solutions such as planting trees where none exist, restoring wetlands, and improving soil practices to absorb and store carbon. It also includes biomass and marine carbon removal, as well as mineralization-based processes that, for example, use crushed rocks to absorb carbon. 

Other CDR practices rely on emerging technologies. They include techniques that draw carbon out of the air with chemicals and giant fans to store it for thousands of years in deep underground geological formations, such as rocks with porous areas filled with salty water or depleted oil and gas reservoirs. These technologies are called Direct Air Capture (DAC). CDR can also involve storing carbon in commercial products such as wood paneling and cement. 

CDR approaches present trade-offs in terms of cost, efficacy, risks, and timelines. DAC technologies have attracted increasing attention from investors, but they are the most expensive carbon removal technique and remain unproven at scale. Methods that rely on storage in geological formations last far longer than other forms of CDR, meaning that the carbon can stay locked away for thousands of years, while methods that rely on soils and vegetation are less expensive, although they can prove less durable. For example, when wildfire incinerates a forest, the forest no longer stores carbon. Storage in commercial products like structural wood used in construction [PDF] can also be comparatively short-lived: when the building gets destroyed, the carbon risks release. 

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CDR is sometimes grouped with a related technology known as carbon capture utilization and storage (CCUS). CCUS is typically used to capture carbon emissions directly from sources of pollution such as manufacturing plants or fossil fuel operations. Although CCUS can reduce the amount of greenhouse gases that reach the atmosphere, it does not reduce the gases that are already in the atmosphere. CCUS therefore does not act to drive down temperatures; in contrast, CDR does. 

Why is CDR necessary?

Through the UN climate negotiation process, nations have set a goal of limiting global average surface temperatures to preferably no more than 1.5° Celsius (2.7° Fahrenheit) above preindustrial times. Achieving the 1.5° goal requires that nations reach net-zero emissions by 2050, which is only possible through large amounts of CDR in addition to aggressive efforts to cut the amount of carbon that reaches the atmosphere, according to the Intergovernmental Panel on Climate Change (IPCC). Scientists estimate that by 2050, the world could need to rely on CDR to remove up to ten billion tons of carbon—double the United States’ annual emissions—every year. 

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The IPCC envisions that through 2050, CDR can lower the accumulation of emissions in the atmosphere, thereby slowing heating; CDR would also have to draw down more carbon out of the atmosphere than is added to it to achieve the goal of net-zero emissions. Beyond 2050, CDR can further counterbalance emissions from “hard-to-abate” sectors such as steel manufacturing, aviation, shipping, and agriculture, and create net-negative emissions, pulling carbon that has already accumulated out of the atmosphere. 

Who is funding it?     

The need for CDR has spurred interest within both the private sector and governments. Last fall, at the UN Conference of the Parties (COP28) in Dubai—the latest UN climate convening—more than seventy sessions focused on carbon removal, an exponential increase over prior years. 

Monies have begun to flow to CDR initiatives, and Washington is one government placing a big bet on carbon dioxide removal. The bipartisan infrastructure bill passed in 2021 provides $3.5 billion to create four regional DAC hubs, while the Inflation Reduction Act passed in 2022 creates tax benefits amounting up to a $180 per ton credit for CDR and carbon storage. That could also lead to a nationwide employment boost: a new study by the Rhodium Group finds that almost all states have the potential to house at least one DAC facility by 2035. By 2050, economic benefits could flow to all states, with Texas as the biggest winner.

Other governments are investing in CDR as well. Australia, Canada, Japan, and the United Kingdom have also provided research and development funding for CDR, and the European Commission has proposed a strategy for the European Union (EU) to capture, trade, and durably store carbon to meet EU climate goals. In February, the EU moved closer to adopting a framework for certifying the quality of carbon dioxide removal projects. The effort could increase trust in the quality of carbon credits traded in carbon markets. 

In addition to government support, the private sector has recently been clamoring for carbon credits from CDR projects to meet corporate net-zero commitments. Demand for carbon credits has driven investment in DAC by companies including Microsoft, Shopify, and Airbus; Swiss Air and Lufthansa have also partnered with a DAC start-up. The consulting firm McKinsey predicts that by 2050, the CDR industry could be worth up to $1.2 trillion.

Why are there reservations about CDR?

Advocates for rapid reduction of fossil fuels have expressed concern that CDR efforts could create a moral hazard by lowering ambition to cut oil and gas consumption. The head of Occidental Petroleum, Vicki Hollub, lent credence to this argument when she suggested that implementing DAC would preserve the oil industry and give oil producers a license to continue to operate. Occidental plans to build around 100 DAC plants to help its oil production reach net-zero.

Concern has also arisen that companies and governments could expand CDR’s applications beyond addressing emissions from hard-to-abate sectors. The IPCC has cautioned that CDR should not substitute [PDF] for steep reductions in carbon emissions, emphasizing that reducing the amount of carbon produced and emitted is the main way to hold warming to 1.5°C. It envisioned a lesser role for large-scale CDR technology such as DAC, given that the technology’s success at scale remains to be seen, making reliance on it a “major risk.” The International Energy Agency has also recognized the need for CDR, but it has warned against too heavy a dependence on technologies that are “expensive and unproven.”

Critics argue that CDR is too expensive and energy-intensive to serve as a viable alternative to rapidly reduce fossil fuels. The world’s first large-scale DAC facility, located in Iceland, can capture only about four thousand tons of carbon annually, a minute share of global emissions. Questions also abound as to whether CDR technology can scale quickly enough at a cheap enough price to avert significant heating. Some argue that money going to CDR would be better spent on keeping more emissions out of the atmosphere in the first place by, for example, increasing investment in renewable energies such as solar and wind power. 

Finally, the focus on carbon removal fails to address other greenhouse gas emissions such as methane that cause more warming in the immediate future. A molecule of methane could last just twelve years in the atmosphere, while a carbon molecule could last hundreds of years. But during its short life span, the methane molecule could trap eighty times the heat compared to the carbon molecule. Atmospheric methane levels are already over two and a half times what they were in preindustrial times, and in the past few years methane emissions have accelerated. 

Is CDR on the right track?

A series of steps known as measurement, reporting, and verification (MRV) are essential to ensure that CDR is responsibly used. The European Union has taken the lead in creating standards by seeking to bring clarity to the quality of CDR initiatives. In contrast, the United States has yet to adopt a national regulatory framework, although it leads the world in legislation to support CDR. Without greater clarity as to the effectiveness of CDR projects, “greenwashing” could occur. 

Elections around the world could play an outsized role in future CDR investments. Former President and 2024 candidate Donald Trump has pledged to dismantle the Inflation Reduction Act, which gave an unprecedented boost to CDR investments. Similarly in Europe, the growing influence of right-wing politicians may threaten government support for CDR. Given the expense involved and the uncertainty of success, some CDR efforts, including engineered DAC solutions, could fall by the wayside without government support.


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