The Growing Importance of CDR
Approx. 3 min read
Unfortunately, despite huge amounts of advocacy, rhetoric, plans and pledges, global emissions are not falling fast enough. Globally, we must continue in our endeavours to try and bring emissions down. However, we have now reached a stage where emissions abatement alone will not be enough of a mitigant to dampen the worst effects of climate change. We need to massively increase the rate at which we are removing carbon from the atmosphere.
Meeting the recent pathways laid out by the IPCC will require total cumulative net CO2 removals of 20-660 Gt CO2 by 2100, an endeavour that would need collaboration at a scale humanity has never seen before. The IPCC stated that “CDR is a key element in scenarios that limit warming to 2°C (>67%) or 1.5°C (>50%) by 2100 (high confidence)”.
Carbon Dioxide Removal (CDR) is the process whereby carbon dioxide is actively and permanently removed from the atmosphere. Carbon removal technology is a catchall phrase to describe any activity, project or system that results in net CDR. Nowadays the term ‘technology’ immediately conjures images of electronic devices, complex machines and computer boards. In a CDR context, technology is used in its literal sense: the application of scientific knowledge for achieving practical goals, in a reproducible way. A CDR technology can be anything from growing seaweed to futuristic direct air capture machines and everything in between.
CDR differs to carbon avoidance projects, as it results in an actual drawdown of carbon dioxide. Carbon avoidance projects either reduce the amount emissions produced, for example through cleaner and more efficient cookstoves that require less wood to fuel them and therefore produce fewer emissions; or they prevent the destruction of carbon sinks, for example stopping deforestation or maintaining habitats that are effective at drawing down carbon dioxide.
Recently, there has been some critical coverage on certain types of carbon avoidance projects – in particular avoided deforestation projects. A recent Guardian exposé made the bold claim that more than 90% of rainforest carbon offsets offered by the biggest certifier are worthless.
The main basis for the claim that so many avoided deforestation carbon credits are ineffective is that the authors of the report suggest that the deforestation baseline rates are inaccurate and overstated. Ascertaining an accurate baseline deforestation rate for a project is crucial, as it is the yardstick against which the additionality of the project is measured. In other words, if the project was not in existence, what area of forest would be lost over a year and what is the corresponding amount of photosynthetic biomass that has been preserved. Preserving trees and other plants that photosynthesise and draw in carbon ensures that they continue to remove carbon dioxide from the atmosphere. Thus, by preventing a certain area of forest being cut down and cleared, a project will have avoided a certain quantity of carbon dioxide staying in the atmosphere. So, if a project has overstated the amount of forest that would have been lost without the project existing, then they are overstating the amount of carbon dioxide they are avoiding from staying in the atmosphere.
Still with us?
There have been responses from proponents of avoided deforestation projects that the Guardian itself has exaggerated the exaggeration of the baseline rates.
Now everyone is a bit lost.
What is clear, is that the science behind these projects is imperfect and can be very difficult to accurately quantify for myriad reasons, not least because monitoring these projects is very resource intensive and illegal logging rates can vary greatly, even within the same area of forest.
CDR projects, on the other hand, are (usually) conceptually much easier to track and quantify. The good thing is that they result in the direct removal of carbon dioxide, thus directly counteracting atmospheric warming. However, not only do we need far more CDR projects to be established but we also need much greater variety in the type of CDR technologies being deployed. To date, there has been too much of a focus on terrestrial projects, with ocean-based solutions massively underutilised.
The State of Carbon Dioxide Removal Report, published this year, is a comprehensive global assessment of the current state of CDR. Amongst the main findings was that “Virtually all current CDR (99.9% or 2 GtCO₂ per year) comes from conventional management of land, primarily via afforestation and reforestation” and that “only a tiny fraction (0.1% or 0.002 GtCO₂ per year) results from novel CDR methods which involve storing captured carbon in the lithosphere, ocean or products”.
Fig. 1 – Diagram showing the underutilisation of alternative CDR technologies, especially ocean-based solutions that fall under the ‘Other novel CDR’ category on the diagram. BECCS is bioenergy with carbon capture and storage. Biochar involves producing biologically unavailable carbon, by heating biomass in a low oxygen environment, and then burying the carbon in soils, where it will remain for 100s to 1000s of years.
Taken from: Smith, S.M., Geden, O., Minx, J.C., Nemet, G.F., Gidden, M., Lamb, W.F. and Powis, C., 2023. The State of Carbon Dioxide Removal Report 2023.
The potential for effective ocean-based CDR projects is enormous. The ocean covers more than two thirds of the planet’s surface, yet is has barely been used for new CDR projects. Solutions need to be modular, scalable, based on rigorous and accurate science, and easily monitored and assessed for their additionality.
Our aim is to ultimately reach a gigatonne scale for removing carbon dioxide, through cultivating Sargassum seaweed in the open ocean. How will we do that? By ensuring our solution is modular, scalable, based on rigorous science, and easily monitored and assessed for its additionality.
Hopefully the dial will soon move and novel CDR methods will make up substantially more than 0.1% of the CDR technology sector.
