What’s the difference between carbon removal and carbon sequestration?
Carbon dioxide removal (CDR) and carbon capture and sequestration (CCS) are not the same thing. Both will be critical in achieving net zero emissions by 2050.
By Asiyah Choudry
August 31, 2022
Global emissions continue to be a significant barrier to addressing climate change. Carbon dioxide removal (CDR) and carbon capture and sequestration (CCS) refer to two different strategies that can help mitigate atmospheric carbon. CDR and CCS are important because 15-40% of human-caused emissions are expected to persist in the atmosphere for thousands to tens of thousands of years, contributing to climate change. The UN Intergovernmental Panel on Climate Change (IPCC) has reported that CDR and CCS will be critical in achieving the emissions reductions needed to limit global warming. Let’s take a closer look at these strategies and how they differ.
What is carbon dioxide removal?
Carbon dioxide removal is the process of removing atmospheric carbon and trapping it in plants, the ocean, or other carbon sinks where it can remain for centuries. Since CDR removes atmospheric carbon emissions, it can help us achieve drawdown, defined as the point in time where global emissions begin to decline.
One example of CDR is reforestation. Trees are an important source of carbon removal, absorbing an estimated 30% of atmospheric carbon. Another example of CDR is direct air capture, a technology that extracts carbon dioxide from the air. Once extracted, the carbon can be stored underground or converted into an input for industrial processes. However, direct air capture is a newer technology that has not been widely adopted. Reforestation costs approximately $50 per ton of carbon removed while direct air capture is significantly pricier, costing between $250 and $600 per ton. Although cheaper, reforestation comes with some caveats and is not the most effective approach to climate change mitigation on its own.
In the US, carbon dioxide removal will play an important role in reducing atmospheric carbon. The US Long-Term Strategy includes plans for the removal of approximately 1-1.8 billion metric tons of carbon dioxide equivalent annually by 2050.
What is carbon capture and sequestration?
Carbon capture and sequestration prevents the release of emissions from industrial processes that rely on fossil fuels or biomass. Unlike CDR, CCS does not remove atmospheric carbon.
The CCS process consists of three steps. Carbon is captured from the burning of fossil fuels. Next, the carbon is compressed and transported to a storage facility. Lastly, the carbon is injected into geological formations deep underground, where it will remain permanently.
It’s also important to note that CCS will not remove 100% of the emissions captured. Typically, CCS projects target a 90% efficiency rate.
To achieve net zero emissions by 2050 - a target to which over 70 countries, including the US, are signatories - we will need 1.7 billion tons of CCS capacity by 2030. As of the end of 2021, global CCS capacity was 40 million tons. For context, US emissions reached 5,222 million tons of carbon in 2020. While more CCS facilities are expected to come online, CCS is not on track to reach the levels required for net zero. According to the Global CCS Institute, the US currently has 13 operational CCS facilities.
CDR removes emissions from the atmosphere and is carbon negative. In contrast, CCS captures carbon from industrial processes before it enters the atmosphere. Since CCS does not reduce the amount of carbon in the atmosphere, it is not carbon negative. Instead, CCS is carbon neutral because it does not increase the level of atmospheric carbon. Carbon removal supports a drawdown in emissions, while carbon capture and sequestration can help to neutralize emissions associated with burning fossil fuels.
Criticisms of CDR and CCS
Cost remains a barrier to the deployment of CDR and CCS technologies. Globally, the deployment of CDR and CCS technologies is still in the early stages. As a result, the cost of implementing these technologies is high. CCS is not expected to see widespread adoption unless it becomes more economically competitive, or governments mandate adoption.
Critics of CDR argue that it reduces our willingness to reduce emissions because we expect they can be offset at a later date. CCS has been criticized as enabling continued reliance on fossil fuels as it helps to mitigate some of the negative effects. The concern with both CDR and CCS is that they will reduce our willingness to address emissions in the short term.
In a report by the Institute for Carbon Removal Law and Policy, experts in climate policy argue that CDR and CCS should be excluded from the IPCC’s climate modeling until there is enough evidence demonstrating that they are technically, economically, and politically feasible. While CDR and CCS have potential as carbon solutions, we should be actively pursuing deep cuts in emissions without expecting that CDR and CCS will be the silver bullet.
CDR, CCS, and the path to net zero
It is evident that both CDR and CCS are necessary to meet climate targets, but CDR and CCS have not been deployed at a large enough scale to mitigate climate change as of now. As a result, it's important that individuals, businesses, and governments work to reduce greenhouse gas emissions.
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