What is CDR?

Carbon dioxide removal (CDR) is the name given to methods or processes that remove carbon dioxide (CO2) from the atmosphere and stores it for a long period of time. CDR can slow the rising concentration of CO2 in the atmosphere or even lower it, to reduce its cumulative warming impact and slow down climate change. The Intergovernmental Panel on Climate Change (IPCC) considers CDR as necessary to achieve net-zero emissions both globally and internationally.

Using this definition, a process is an effective CDR method only when three conditions are met:

• It removes more CO2 from the atmosphere than would be removed via natural processes.

• It stores CO2 in a way that does not allow it to easily re-enter the atmosphere.

• It removes more CO2 than the method itself emits.

There are many CDR methods. They differ in two important ways. The first is where the CO2 is extracted from. This could be from the air, the ocean, or plants. The second difference is in how it is stored. This could be deep underground as a fluid, combined with minerals to turn it into a rock, in plants or soil, or dissolved in the ocean. Afforestation is an example of a CDR method. It involves planting and growing trees in areas where there were none before. In this process, trees and plants absorb CO2 from the air via photosynthesis. The CO2 is stored in the trunks, branches, roots and soil. If the trees remove more CO2 from the air than what is released from their  lifecycle (planting, growing, decay), including from inputs such as fertilizers or machinery, then this is considered CDR. Direct air capture with carbon storage is another CDR method. It involves using special materials to capture and separate CO2 directly from the air, and then durably storing that CO2 deep underground or combining it with minerals to turn into rock. Other examples include spreading certain minerals over a field that can react with and capture the CO2 dissolved in rainwater, or adding certain minerals to oceanwater to increase its ability to absorb CO2. CDR methods all have different attributes, such as cost of implementation, land use, energy use, environmental impacts and benefits.

One important attribute is the durability of storage. This refers to how securely and for how long the CO2 will remain locked away from the atmosphere. In the example of afforestation, hazards like forest fires pose a threat to the durability of the carbon storage. In general, “durable CDR” refers to methods that store CO2 for thousands of years or more.

Interest in CDR has grown significantly in the past 10 years:

• The Intergovernmental Panel on Climate Change (IPCC)’s 2022 report  says “the deployment of CDR to counterbalance hard-to-abate residual emissions is unavoidable if net-zero CO2 or GHG emissions are to be achieved.”

• The Government of Canada has developed several policies to support CDR development, including investment tax credits for certain types of CDR projects and a procurement program for CDR services.

• Many companies are supporting CDR by buying "removal credits” voluntarily. Of all the removal credits voluntarily purchased by the end of 2024, 95 per cent have been purchased since 2023.

Note that CDR is different from carbon capture and storage (CCS). CCS captures CO2 directly from the source of emissions — like a natural gas power plant or oil refinery — whereas CDR captures and removes CO2 already in the atmosphere.

CDR may reduce the cumulative effects of CO2 emissions, but it cannot reverse all the impacts of climate change. CDR does not address the negative social and environmental impacts caused by our current energy system and also risks perpetuating the same impacts if not developed responsibly.