What is carbon removal?

Carbon dioxide removal (CDR), or carbon removal, is the process of removing CO2 from the atmosphere and sequestering it permanently. Carbon has circulated for millennia from the atmosphere to forests, soils and ocean as part of the natural carbon cycle, but atmospheric concentrations of CO2 and other greenhouse gases have steadily increased since the Industrial Revolution, predominantly due to burning fossil fuels. Carbon removal seeks to accelerate and augment the natural carbon cycle to reduce the level of CO2 in the atmosphere or use technologies that directly extract CO2 from the air.

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How can carbon be removed from the atmosphere?

Carbon removal includes a range of approaches, from nature-based approaches like growing trees and restoring coastal wetlands to more technological approaches like direct air capture (DAC), carbon mineralization and approaches that store the carbon found in biomass (bioenergy with carbon capture and storage is the most common approach here, but others have been proposed as well). A robust portfolio of natural and technological approaches will help reduce costs, increase flexibility, minimize risks and balance tradeoffs associated with any one solution.

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Why is carbon removal needed?

Keeping temperature rise to 1.5 degrees C, as outlined in the Paris Agreement, will require us to reach net-zero emissions globally by midcentury. Reaching this goal will require deep emissions reductions, first and foremost, from every sector of the economy. Carbon removal is needed alongside those efforts to balance residual GHG emissions that cannot, or would not, be reduced by midcentury if abatement technologies do not become available or cost effective at scale. Even after we reach net-zero, carbon removal can help reduce the historic excess concentration of CO2 in the atmosphere (sometimes called ‘legacy emissions’) to safer levels. Current concentrations of CO2 are already causing more frequent and intense extreme weather events and sea level rise that are disproportionately affecting countries least responsible for these emissions.

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Is large-scale carbon removal possible?

Some carbon removal approaches like tree restoration can be deployed at large scales today but require supportive policies to incentivize implementation. Other approaches that are at earlier stages of development, like direct air capture (DAC), would benefit from continued research and development, policy support to accelerate deployment of existing technologies, and adoption of best practices and safeguards to ensure responsible scale up. These investments are necessary to develop approaches today so they will be ready to deploy when they are needed in coming decades. Complementary infrastructure will also be needed to support carbon removal build-out, including CO2 transport and geological sequestration sites to store captured CO2 for approaches like DAC, and renewable energy infrastructure to power carbon removal technologies.

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How much carbon removal do we need?

The Intergovernmental Panel on Climate Change (IPCC), the world’s most authoritative body on climate science, has stated that all pathways that limit global warming to 1.5°C will require some degree of carbon removal. The IPCC’s climate modeling scenarios indicate that dependence on carbon removal could vary widely, from less than 1 billion tonnes per year to more than 10 billion tonnes per year of carbon dioxide removed. Other estimates that use different methodologies also point to several billion tonnes of carbon removal needed per year.

The amount of carbon removal ultimately required to avoid the worst impacts of climate change depends on the speed and scale of emissions reductions. We have a near-term opportunity – and imperative – to reduce emissions as much as possible to minimize our future reliance on carbon removal. In most cases, it will be more costly and difficult to pull emissions out of the atmosphere rather than prevent them from being emitted.

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What are the local impacts of carbon removal?

The intended effect of carbon removal is to pull CO2 out of the atmosphere to ultimately reduce the atmospheric concentration of CO2 to safer levels. This benefit is global, but carbon removal projects may also have local impacts, which can be positive or negative.

For example, tree planting and practices that increase soil carbon can improve air quality, water cycling and resilience to climate change. But changes to the way the land is currently being used may also disadvantage some people economically. Technological approaches like DAC can bring jobs and investment, but need nontrivial amounts of land, energy and water to operate.

These local impacts need to be considered in project planning and in partnership with potential host communities. Understanding the local impacts of proposed projects, communicating those with local communities and providing opportunities for negotiation of benefits will be critical to developing community understanding and hopefully acceptance of carbon removal technologies, and ultimately scaling carbon removal responsibly.

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What’s the difference between carbon capture and carbon removal?

Carbon capture and use or storage (CCUS) is a technology that captures carbon dioxide emissions at the source, such as cement plants, before it enters the atmosphere – making it a form of emissions reduction. CCUS is likely to be particularly critical in the industrial sector, where there are few or no alternatives to abate some types of emissions (e.g., process emissions from cement production).

Carbon removal is distinct from point source CCUS because CDR removes excess carbon dioxide that has already been emitted into the atmosphere.

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Cover Image by: Cecilio Ricardo / USDA Forest Service