As global carbon dioxide emissions continue to rise, many researchers and policymakers have concluded that removing carbon from the atmosphere will be necessary to keep the rise in global temperatures below two degrees Celsius – as agreed to in the Paris Climate Agreement. The United Nations' Intergovernmental Panel on Climate Change (IPCC), in its fifth assessment report, found that many climate models can only meet the two-degree Celsius goal when carbon removal strategies are included among the potential policy options (IPCC, p.16).
Carbon Removal Strategies
Carbon removal can take many different forms. According to the Center for Carbon Removal, the strategies to remove carbon are generally split into two categories: natural carbon removal and technological carbon removal.
Carbon removal by naturally occurring processes is simply the uptake and storage of carbon dioxide (CO2) by our ecosystems. This can be accomplished through “carbon sinks;” specifically, through land-based carbon sinks and “blue carbon.” Land-based carbon sinks describe the large swaths of forests, wetlands, agricultural lands, and soil that pull CO2 from the air and store it in their biomass (UNEP, p.60). “Blue carbon” is a similar phenomenon, but describes the storage of carbon in coastal and ocean ecosystems, such as intertidal saltmarshes, mangrove forests, and seagrass meadows. While these carbon removal systems are (by definition) naturally occurring, there are policies that can be implemented to maximize the natural uptake of carbon. Afforestation (planting trees in places naturally without trees) and reforestation (planting trees in deforested areas) are common practices that can enhance carbon uptake. Improving agricultural land management techniques is another way to increase carbon uptake and storage.
Carbon removal can also be achieved through technology that actively removes carbon from the air. The most common technological forms of carbon removal include: carbon capture and storage (CCS—the "S" can also stand for sequestration), carbon capture, utilization, and storage (CCUS), bioenergy with carbon capture and storage (BECCS), and direct air capture (DAC). While CCS and CCUS are technically considered emission mitigation techniques (they do not remove carbon directly from the atmosphere, per se), they are still crucial to understanding carbon removal generally. This is because the technology behind CCS and CCUS is very similar to the technology employed to remove carbon through BECCS and DAC.
CCS is generally the most basic type of carbon removal – it is the process of trapping carbon from streams of pollution and storing it, usually miles underground. CCUS is the same process as CCS, but it allows for the captured carbon to be used for other purposes (which can make carbon removal more profitable and so more practical). These uses range from enhanced oil recovery to forming “soda bubbles” (as noted by Sen. Whitehouse). These re-utilization technologies sometimes result in the captured carbon being released back into the atmosphere, depending on how the carbon is used. Some potential uses (e.g., trapping carbon in cement) could permanently capture the carbon, while other uses (such as adding carbon to soda) would release the carbon back into the atmosphere. Still, on the whole, carbon capture technologies reduce the overall amount of carbon emissions by reusing the carbon that otherwise would have been immediately emitted into the atmosphere.
BECCS and DAC are two technologies that directly remove carbon from the atmosphere (generating “negative emissions”). BECCS specifically refers to capturing carbon emitted from facilities that generate electricity through biomass combustion. Essentially, this is how BECCS works: the plants (biomass) pull CO2 from the atmosphere via photosynthesis, the BECCS facilities use the biomass to generate electricity, and all the resulting carbon is captured using CCS. This process makes BECCS especially attractive, because it removes carbon while also producing electricity. Lastly, DAC describes the process of removing CO2 directly from the atmosphere.
Benefits of Carbon Capture
The most obvious benefit that both natural and technological systems share is their ability to remove carbon from our atmosphere, or prevent it from reaching the atmosphere to begin with. These systems, when employed properly, have the potential to help keep global temperatures from surpassing the two degree Celsius mark. To achieve this goal, carbon dioxide must actively be removed from the atmosphere – a process known as generating “negative emissions.” In an article published by Nature Communications, Thomas Gasser and his co-authors found that the only feasible way to keep warming under two degrees Celsius is to generate negative emissions, as well as substantially decrease our greenhouse gas emissions. While carbon removal should not be viewed as a panacea, it should be incorporated into global strategies to reduce climate change.
The benefits of implementing some of these carbon capture techniques are not limited to a reduction in greenhouse gasses. Enhancing the natural carbon removal process has many societal benefits as well. These include increasing climate resiliency (UNFCC, p. 74) and advancing other environmental goals, such as enhancing land conservation practices and bolstering wildlife conservation.
Implementing technological strategies also has benefits. One major benefit is the potential to quickly remove CO2 on a large scale (compared to natural systems, which are slower to absorb carbon). Another is the utilization aspect in CCUS – that extra carbon could serve many useful purposes, generating economic growth and jobs. If CCUS were to become profitable, it could spread quickly and help combat climate change. Lastly, even if technological strategies are unable to remove 100 percent of carbon, they can still help smooth the transition to a clean energy economy by reducing the amount of carbon emitted from coal-fired or natural gas power plants.
Concerns Around Carbon Capture
While there are many societal benefits associated with carbon removal (along with a pressing argument for doing so quickly), there are possible drawbacks and risks. For natural carbon removal systems, concerns include the potentially large administrative costs, the designation of large areas for carbon removal, and the slow speed at which carbon sinks can absorb the CO2. For technological carbon removal systems, the main concerns are costs, scalability, and the associated moral implications.
The costs of enhancing natural carbon removal systems – such as implementing regulations and designating large areas of land for this purpose – are potentially high. Also, investing in naturally occurring carbon removal systems may not be the quickest way to reduce atmospheric CO2. If other GHG mitigation strategies can reduce overall emissions faster (and more cheaply) than natural carbon removal systems, then directing investments to these other strategies will be more efficient.
Technological carbon removal systems are not without their drawbacks either. The technology behind these systems is proven, yet removing carbon remains costly. Until regulations are put in place, carbon is priced adequately, or carbon utilization becomes profitable, carbon removal technologies will continue to remain economically unfeasible. (A recent update to the federal tax code that creates incentives for carbon capture is discussed in more detail below.)
Another concern with technological carbon removal strategies is their scalability. In order to avoid the two-degree Celsius mark, these technologies will need to be scaled up globally, and incredibly fast. Given their current cost and unprofitability, it is debatable as to whether these technologies can be scaled up quickly enough.
Lastly, a concern that invariably comes up during discussions of carbon removal is its potential for creating moral hazard. Some argue that the presence of carbon removal will allow others to continue emitting GHG pollutants, under the assumption that their current emissions can be removed from the atmosphere at a later date. But this line of thinking is flawed, because both emission reductions and carbon removal are necessary to avoid the two-degree Celsius mark; relying solely on carbon removal is untested, expensive, and unrealistic.
It is rare to find a bipartisan climate bill in the United States Senate. Still, on March 22, five senators – two Republicans and three Democrats – introduced the USE IT Act (S.2602), a bill that supports funding for carbon removal research. A few weeks ago, this bill was voted out of the Environment and Public Works Committee – a substantial step toward moving the legislation forward. While this bill draws bipartisan support for different reasons, the resulting outcome is the same: carbon removal is advanced.
Another notable policy development is the recent update to Section 45Q of the federal tax code. Section 45Q now incentivizes industries to enter into the carbon capture market. This updated provision eliminates the cap on redeemable tax credits that industries can claim when removing carbon from the atmosphere. So, entering the carbon removal market becomes less financially risky. The updated tax credit applies to CCS, CCUS, and DAC. Other recent policy developments include the introduction of the Farmers CARE Act (H.R.5627), which would incentive farmers to create grazing plans that also maximize the carbon uptake of soil; and the introduction of the Department of Energy Research and Innovation Act (H.R.589 and S.2503), which encourages carbon removal through DAC technologies and natural systems.
Carbon removal research is also making headway. Earlier this month, the company Carbon Engineering, along with scientists at Harvard University, claimed to have developed a cheap method for removing atmospheric CO2 via DAC technologies. Other developments include the recent opening of a CCS testing facility in Wyoming and a Stanford University study which finds that 60 percent of the CO2 emitted from ethanol plants could potentially be captured at a low cost.
Carbon removal systems are feasible, have many benefits, and are making progress in the policy and research realms. Most importantly, carbon removal strategies address climate change, which is one of the world’s most pressing threats. Incorporating carbon removal into our policy solutions is necessary to avoid the two degree-Celsius mark, and thereby avoiding a possible tipping point into a climate catastrophe.
Author: Maria Pfister
- "Negative emissions physically needed to keep global warming below 2°C," Nature Communications
- "Federal Budget Bill Includes Massive Tax Credits for Carbon Capture," Center for Carbon Removal
- USE IT Act (S.2602), U.S. Senate
- Farmers CARE Act (H.R.5627), U.S. House of Representatives
- Department of Energy Research and Innovation Act (S.2503), U.S. Senate
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- "The Emissions Gap Report 2017: A UN Environment Synthesis Report," UN Environment
- "Fifth Assessment Report on Climate Change: Summary for Policy Makers (2014)," Intergovernmental Panel on Climate Change (IPCC)