It excludes emissions reductions activities, such as carbon capture utilisation or storage (CCUS) technology that operates at point of source, capturing emissions from flue or smokestacks. This is an emissions reduction, as opposed to a removal, as it is reducing the amount of emissions that would have been emitted into the atmosphere rather than removing emissions that are already in the atmosphere. 

Any utilisation of the carbon dioxide that would allow for it to be re-emitted is also not classed as a carbon dioxide removal. Nor is carbon removed by natural sinks, such as healthy, functioning rainforests, seagrass meadows and other ecosystems that exist without human intervention or aid. However, any human-led activities to restore or expand these ecosystems would qualify as carbon dioxide removal.

What do we mean by carbon dioxide being stored for at least 100 years? 

There are dozens of ways to remove carbon, from restoring ecosystems to speeding up the rate of the natural weathering of rocks (known as enhanced weathering). Different carbon removal solutions store carbon for different amounts of time. The amount of time that carbon dioxide stays locked away, as well as the risk of reversal (i.e. re-released into the atmosphere) is known as durability. Lower durability removals store carbon for decades to centuries. Higher durability removals, or longer term storage, can be expected to remain for at least 100 years, but up to 10,000 years or longer, depending on the method. See Box 8, Figure 1 from the IPCC WGIII report for examples of different methods and how they fit according to removal process and storage timescales.

For example, the carbon dioxide stored in the woody biomass of trees can be re-released into the atmosphere if those trees naturally decompose at the end of their life or prematurely burn in a forest fire. As such, the removal from afforestation or reforestation can last from 5 years to 500 years (depending on the longevity of the trees). Although these removals solutions are commonly described as ‘lower durability’ or less than 100 years.  

This is important because the amount of time that carbon dioxide stays out of the atmosphere has an impact on climate change and keeping to the goals of the Paris Agreement. 

Box 8, Figure 1: categorises carbon dioxide removals methods based on the removal process and the storage medium. Note that specific land-based implementation options can be associated with several CDR methods – for example, agroforestry can support soil carbon sequestration and provide biomass for biochar or BECCS.

Why Carbon Dioxide Removals?

To deliver a resilient, safe climate we must reduce carbon dioxide emissions by at least 50% by 2030, reach net-zero emissions by 2050 and stay at net-negative emissions throughout the second half of the century.

The science is clear. All IPCC modelled pathways that keep warming below the Paris Agreement threshold of 2°C, or preferably 1.5°C, require emission reductions and the safe removal and storage of CO2 from the atmosphere.

We cannot be deforesting with one hand and reforesting with the other. This does not shift the overall carbon balance in the right direction. To achieve our Paris-aligned goals, we must be reducing our emissions as fast as possible across all sectors while increasing our global capacity to remove past emissions from the atmosphere. These activities are complimentary; they cannot be substituted one for the other.

By 2050, the IPCC estimates that we will need to remove up to 6 billion tonnes of CO2 per year through net removal on managed land (including afforestation and reforestation) and approximately another 3 billion tonnes per year through solutions such as DACCS and BECCS. In 2020 we emitted ~37 billion tonnes of CO2. We currently remove just a few million tonnes of CO2 per year.

Fortunately, many scalable carbon dioxide removal methods already exist, such as mangrove restoration, direct air capture and storage, enhanced weathering and reforestation. However, it is not only about developing and scaling our removals capacity but how we do it. This is where the ‘responsible’* part comes in.

*“accounting for societal values and interests in relation to which carbon dioxide removal approaches to incentivize, how they should be incentivized, and how they should be governed once incentivized.”

How to do carbon dioxide removals right

“Developing CDR capacity is not a matter of simply selecting the technologies that look best when viewed through a science-informed lens. Rather, how we develop CDR matters. It matters whether these approaches take place in disadvantaged communities without offering benefit, or whether they are designed in ways that offer communities good employment and revenue. It matters whether they decrease biodiversity or restore it. It matters whether polluters are paying for it, or if those who can least afford it are bearing the cost. These are choices.” – CDR Primer, 2021

Removals must support the goals of communities beyond simply reaching our 2030 targets; restoring health, providing economic vitality, regenerating ecosystems, promoting social and environmental justice whilst increasing our resilience to the effects of climate change. It is important that we see a just, equitable, managed and financed scaling of the carbon dioxide removals ecosystem.