Reality Check: Demystifying the Need for Carbon Dioxide Removal
Carbon dioxide removal (CDR) is not a substitute for emissions reduction, but science says we’ll need it too, to protect a livable planet. To ready these crucial tools, here’s what we must do.
Carbon dioxide removal (CDR) is not needed because emissions reductions alone will be sufficient to achieve the world’s climate goals.
Based on the best available science, the pathway to a 1.5°C-aligned future that avoids catastrophic climate change will require massive amounts of CDR to extract CO2 from the atmosphere and durably store it.
While we must do all we can to minimize the need for CDR by accelerating emissions reductions, the world will need billions of tons of CDR annually by 2050. This is a matter of consensus among major climate-focused groups — from the UN Intergovernmental Panel on Climate Change (IPCC) to the National Academies of Sciences, Engineering, and Medicine (NAS) to the International Energy Agency (IEA).
Achieving this scale will require the development, testing, and substantial deployment of CDR solutions in the next decade so that they can be built cost-effectively, sustainably, and equitably when needed. CDR is not a substitute for other climate action, and emissions reductions still comprise the majority of activity needed to keep global warming within target levels.
The emissions budget is shrinking rapidly
The IPCC’s latest research makes clear that we have a limited budget for new greenhouse gas emissions to avoid the worst impacts of climate change. Unfortunately, the world is on track to use up that budget in the next 12 years.
As a result, rapid and drastic reductions as well as CDR at the multi-billion-ton per year scale will be needed to stabilize the climate. For comparison, only a few industries in the world move physical mass at this scale, including coal, steel, concrete, liquid fuels, water, and food.
It is also likely that — even with a successful and complete transition of the energy system away from fossil fuels and the deep decarbonization of industry — residual emissions will continue beyond 2050 in some sectors, such as agriculture and aviation. It is also possible that emissions from forest fires, permafrost melts, and other events that occur outside of human industrial activity will increase, because of dynamics already unleashed.
Thus, CDR will need to fulfill three roles that cannot be accomplished by emissions reductions:
- Reducing net emissions during the decarbonization transition, to avoid temperature overshoot before 2050
- Counteracting continued emissions after the decarbonization transition from activities that are very expensive or technically infeasible to mitigate, like some forms of agriculture and aviation, to continue avoiding temperature overshoot after 2050.
- Removing historical emissions after achieving net zero, to address any temperature overshoot that has occurred.
What CDR is — and is not
CDR is human activity that removes CO2 from the atmosphere and durably stores it in geologic, terrestrial, or ocean reservoirs, or in products. Many CDR methods are at an early stage, and new techniques are being developed at a rapid pace.
The known CDR techniques can be broadly grouped into three categories: biogenic, geochemical, and synthetic, based on whether the key input to the removal process is sustainable biomass, alkaline minerals, or low-carbon energy. Each of these categories is comprised of a vast and growing number of specific approaches. Each of these has unique benefits, impacts, and potential. Forthcoming publications will describe these CDR methods in more detail.
CDR does not include activities that reduce greenhouse gas emissions by capturing CO2 from processes that generate emissions, such as the combustion of fossil fuels or calcination of carbon-rich rocks to produce cement. The capture and storage of CO2 from point sources such as power plants (coal or fossil gas combustion) or cement plants (emissions from heating limestone) reduces emissions from industrial activities but does not reduce the amount of CO2 in the atmosphere. This is an important distinction to note, as both removal and reduction solutions are necessary.
Decades are required to build an industry
Today’s CDR industry is incredibly small compared to what it needs to be in 2050, and it will not be possible to instantly build a multi-billion-ton industry from scratch once the easiest and cheapest mitigation options have been exhausted.
It takes time to create new industries. For example, solar photovoltaic power generation was invented in 1950. A functioning, scaled market to pay for electricity production already existed. However, by 2010 solar provided just 0.1 percent of global electricity and required another decade to reach just 3.1 percent. Many CDR approaches are being tested for the first time now, and there is no functioning, scaled market in place to pay for CDR.
We need to take major steps forward on CDR in this decade so that multi-billion-ton scale removals are possible at a reasonable cost when they are needed. These steps include, but are not limited to: technology research, development, and deployment (RD&D); development of monitoring tools, standards, regulations, markets, and buyers; training thousands of workers; and building the necessary supporting infrastructure.
Critically, a great deal of learning and cost reduction can only happen through building pilot and commercial facilities, so we need to safely test and deploy CDR approaches in the real world starting now.
Concerns and challenges
Given that CDR is necessary and we must develop and responsibly deploy these solutions soon, it is important to note some of the concerns and challenges associated with CDR and emphasize the need for caution.
- A major concern with CDR is mitigation deterrence — i.e., moral hazard — the possibility that the increased plausibility of using CDR to address climate change will reduce motivation to cut emissions.
- In addition to emissions that cause warming, a parallel concern — emphasized especially by environmental justice advocacy groups — is that the use of CDR would perpetuate harms from non-CO2 pollution on overburdened communities either through direct impacts from the project on air quality, water quality, ecosystems, or quality of life, or by providing emitters with a license to continue operating and generating emissions.
- Another risk is that CDR would result in the diversion of financial and material resources away from emissions reduction efforts.
In short, poorly implemented CDR could cause negative impacts in a range of areas, including environmental, health, and equity. These challenges are especially acute given that many CDR methods are so nascent, the potential scale of these risks cannot yet be fully understood.
It is beyond the scope of this article to discuss potential solutions to these concerns except to note that adequately addressing the environmental and social impacts of CDR deployment will be key to building this sector.
CDR’s critical role
Excess reliance on CDR could slow or increase the cost of reaching our climate goals, so reduction should be prioritized wherever possible. However, the science is clear: CDR will be needed to reach those goals.
Action is needed now, and this decade represents our only opportunity to ensure that CDR is deployed cost-effectively, sustainably, and equitably on the timeline and at the scale required.