What is Carbon Dioxide Removal (CDR)?
With a rapidly closing window of opportunity to limit temperature rise to 1.5 degrees, Vertree’s Head of Technological Carbon Removal, David Stead, examines the role of CDR technologies on the pathway to net zero.
Recognised by the Intergovernmental Panel on Climate Change (IPCC) as required to achieve global and national targets for net zero greenhouse gas emissions[1], CDR is rising up the global agenda. Reducing emissions is an urgent imperative but ultimately will not alone be sufficient to achieve net zero, certainly not in the limited time frame required and especially considering that global emissions remain on the up (rising 0.9% to 36.8 billion tonnes in 2022[2]).
But CDR it is not without its challenges and of course varying costs. In this article we define CDR, provide an overview of emerging technologies, and examine the reasons for investment today as part of an urgent and comprehensive strategy to avert climate breakdown.
Broad Definition
Carbon dioxide removal (CDR) encompasses any technology, practice or process which removes carbon dioxide from the atmosphere and durably stores it. A medium to high level of durability is considered to be over 100 years. CDR as a term is reserved specifically for deliberate human activities to remove carbon dioxide and is not inclusive of natural processes which remove carbon without intervention.
There are now an increasing number of emerging technologies focused on CDR…
Examples of Technological Carbon Dioxide Removals (T-CDR)
Bioenergy with Carbon Capture and Storage (BECCS) – This is the capture and permanent storage of CO2 through the use of biofuels (fuels derived from a biogenic source). Naturally, biomass captures carbon as it grows which offsets the emissions of its combustion. The removal potential, however, lies in pairing it with carbon capture and storage to permanently divert the carbon dioxide from the carbon cycle post combustion.
Biochar/biooil – Often a form of the above, these products are the result of separating carbon from biomass and storing it. Biochar is a substance like charcoal created through a process called pyrolysis, which involves heating up biomass to very high temperatures in low-oxygen conditions. It is typically applied to soils for storage and thought to improve the quality of the soil. Biooil is similar in that it is created through pyrolysis but results in a liquid, which typically will be pumped into geological storage.
Direct Air Capture (DAC) – One of the most expensive and energy-intensive processes, these technologies capture CO2 from the atmosphere by mechanical means for storage in geological formations or for use in other applications. The technology can be implemented at any given location, not at the source of emissions as with carbon capture.
Carbon storing materials – There is growth in new innovative processes which create materials to act as sinks to store carbon e.g. concrete or plastics. These are particularly appealing where the sink is a useful product in itself and provides a durable storage solution. However, it is important to complete full carbon lifecycle analysis and confirm net removals are achieved.
Mineralisation – This is the accelerated capture and storage of CO2 in the form of carbonate minerals such as calcite or magnesite. It uses natural processes but accelerates them by extracting and refining rocks and minerals to increase exposure to the atmosphere. Whilst the chemical pathway is clear and well understood, the timing and rate of sequestration is site and weather dependent. Projects have been working to improve the accuracy of carbon accounting, and crediting mechanisms are only recently emerging.
Ocean fertilisation – This involves accelerating, by technical means, the natural processes of CO2 uptake by both the water and organisms in oceans. This is done by adding nutrients to the upper ocean waters. The science for these technologies is still being developed, and few projects are in commercial operation today, but the potential is huge and it is an exciting space.
Examples of nature-based carbon removals
Soil carbon – This encompasses agricultural or land management practices which protect and bolster natural carbon stocks in the soil.
Afforestation, reforestation and Improved Forest Management (IFM) – Within these mechanisms tree growth is supported, encouraged and protected, and carbon remains naturally in the biomass.
Blue carbon – This is CO2 capture and storage by biomass specifically in marine or coastal ecosystems such as mangroves and seagrass beds.
Nature versus technology?
Nature-based solutions to carbon removal leverage known natural processes and are currently low-cost comparative to technological removals. They restore natural habitats and usually provide numerous social and environmental co-benefits. However, permanence and precise carbon measurement will always be challenging as natural ecosystems are often vulnerable to loss or degradation, bringing the risk of carbon sinks being lost.
Technological carbon removals have the potential to provide permanence and for the carbon to be more easily measured and quantified (in some technologies). However, they are currently more expensive and considered to have as-yet unproven viability at scale. As emerging technologies, they are also yet to have the standardised methodologies and mechanics for accounting and verification of other solutions. Perhaps the most significant concern however relates to the perception that their investment will come at the expense of preserving and restoring natural systems.
But that shouldn’t be the case. In fact, we will need both, at scale, on the journey to net zero. Rather than pit one solution against another, realising the potential of both is the best chance we have of achieving our goals.
Why invest in technological removals today?
While we can invest in nature-based solutions today at comparatively low cost, and we should do this, investment in T-CDR is also essential today to enable these mechanisms to develop, scale and reach their potential in the coming decades as our climate deadlines near and we will need them most.
Due to the cumulative warming potential of CO2 in the atmosphere, the implementation of carbon removal technology is essential as soon as possible. Delaying removals will lessen the chances of these technologies effectively limiting global warming.
What does this mean for your organisational climate strategy?
It is widely accepted (by international target and claim standards such as the Science Based Target initiative, and the Oxford Offsetting Principles) that to achieve net zero, companies will eventually be required to eliminate residual emissions with carbon removals. Removals will also be particularly material for hard-to-abate sectors who are likely to be most exposed to rising costs of carbon and the pressures to decarbonise.
Consequently, the demand for removals is set to increase along with cost and competition over supply. Making investments into key projects and technologies could therefore pay dividends (or carbon credits) in future, and having a diverse portfolio of removals can limit risk and increase advantage.
Very few corporates are making investments in the space of T-CDR yet, which also provides the opportunity of the first-mover advantage in this space. Plus attending to legacy emissions becomes a possibility and could be the next frontier of climate leadership for organisations.
Ultimately, there is no time to lose in advancing all elements of our climate strategies and this includes CDR. If viewed as complimentary to science-aligned reductions and nature-based restoration, investing today can ensure we will have the broadest range of technically and financially viable solutions to tackle the climate crisis.
[1]https://www.ipcc.ch/report/ar6/wg3/downloads/outreach/IPCC_AR6_WGIII_Factsheet_CDR.pdf
