The removal of carbon dioxide gas from the atmosphere is seen by some as crucial to compensate for the emissions from human activities that are, it is claimed, difficult to decarbonise – for instance, those generated in aviation and agriculture. However, an interesting Quadrature Climate Foundation (QCF) overview back in 2024 noted that since the concentration of CO2 in the air is about 0.04% it is ‘very difficult & correspondingly costly to do CDR’. Ii added it is ‘scientifically, environmentally & economically more effective to avoid a ton of emissions than it is to remove it from the atmosphere’. So, CDR should ‘not be used as an excuse to continue with business as usual’ and ‘net negative emissions technologies should only be deployed to compensate for residual emissions after abatement, or as a means of addressing legacy emissions’.
So though it thought Carbon Dioxide Removal (CDR) was important, especially natural as opposed to engineered CDR, it wasn’t very positive overall. It concluded that ‘CDR faces a suite of bottlenecks to scale, including the need for more research and development to de-risk various CDR approaches, access to financing, resources, and talent’. It is interesting then to look at a recent major CDR conference in Milan to see if things have improved. Well it seems not a lot. While much was made of the need for CDR, it was noted that ‘we should be very clear that there still are huge uncertainties about the effectiveness of lots of this CDR technology – are they marketable or not?’
Nevertheless, Dr Morgan Edwards, the lead author of the recently published ‘state of CDR report’, was upbeat on the need for CDR. He said that meeting the Paris Agreement’s 1.5C goal by the end of this century would require CDR to ‘scale up rapidly’ from 2.2bn tonnes of CO2 (GtCO2 p.a) today to 8.8GtCO2 by 2050. And CDR does appear in many official plans and scenarios, alongside carbon capture and storage (CCS) i.e. the removal and storage of carbon dioxide produced by fossil combustion. For example, carbon removal is seen as an essential pillar in UK energy ‘net zero’ pathway, along with CCS, with the Carbon Budget and Growth Delivery Plan targeting roughly 21.8 MtCO2 of removals by 2035.
However, as noted above, scientists have stressed that CDR must be in addition to steep emissions cuts, and there are issues. As Carbon Brief noted in a useful review of the Milan conference, CDR isn’t just about compensation for hard-to-decarbonise activities, ‘CDR has another role, which is as a mechanism to return average global warming to 1.5C above pre-industrial levels, in the likely event that the Paris Agreement’s temperature target is exceeded’. If and when this overshoot gets worse, then CDR is seen as at least one answer. Well it might be, but so is mitigation- via more renewables, and if you must, nuclear, plus energy demand management/efficiency.
What can CDR offer? CDR from afforestation and reforestation compensated for about 6% of human fossil-fuel emissions between 2014-23. And it can do more, as Barbara Saget from the Paris School of Economics made clear. As Climate Brief noted, her teams research ‘had showed that nature-based CDR was needed in the medium-term to offset hard-to-abate emissions and limit reliance on more expensive solutions’. However, it also found that ‘as forests grow, an increasing share of captured CO2 is used to compensate for carbon produced during forest disturbances, rather than human-caused greenhouse gas emissions. Furthermore, in the EU, the issue of tight land availability restricts the expansion of forest-based removals’. Thus, Saget concluded, ‘forests are not reliable in the long-run to offset the hard-to-abate emissions, first because of the release of emissions – this reversal risk – but also because of land constraints. So, we need to rely on technological CDR to compensate for these remaining emissions.’
Certainly ‘the major scale up of novel CDR that we might need to meet climate goals’ was stressed at the conference, although it was also made clear that wider-spread use was ‘likely require substantial cost reductions for these technologies.’ Although it was also noted that ‘carbon pricing would influence the geography of biochar deployment and would eventually shift biochar from an “agricultural technology” to a “carbon-removal technology”.’
However, for the others CDR approaches, such as carbon negative DACCS (Direct Air Carbon Capture and Storage) and BECCS (Biomass Energy with Carbon Capture and Storage), there was sense that it could be hard going, especially the idea of dealing with overshoot. For example, it was reported that a national survey on US public opinion about decarbonisation &climate policies, including CDR, had revealed that many members of the US public see the concept of a return to 1.5C from above as ‘fantastical and implausible’.
That view was partly reinforced by the parallel report on the current state of CDR, mentioned above, which noted that the USA, which was previously a ‘leader’ on CDR, has now ‘frozen or dismantled funding and support’ for CDR under the Trump administation. It also said that, for the rest of the world there was still a ‘lack of robust demand signals’ for CDR, including measures such as binding targets, government procurement initiatives and tax incentives for buyers.
So where are we going with CDR? At the Milan conference, Dr Morgan Edwards still looked to rapid expansion and said ‘we need to see an upscaling in ambition over the next few years to get on a track consistent with these long-term scenarios.’ However, opponents like Prof. Kevin Anderson and colleagues at the Tyndall Climate Centre in Manchester have said ‘while some carbon removal is necessary to offset “impossible to mitigate” emissions from agriculture - for example, nitrous oxide from fertiliser use- using CDR to justify ongoing fossil fuel use is a high-risk approach that undermines the Paris climate commitments. Nature-based carbon removal options are also overstated’.
As I argued in an earlier post, it may that there will be a role for changed farming methods and natural carbon sequestration, and some may see DECCS and BECCS as playing an interim role as negative emission options, despite the land-use implications of BECCS and the energy needs of DECC. However, give the unknown costs and the potential eco-impacts, CDR generally, much like CCS, does not seem to be a major way forward to a sustainable future. Especially if it undermines progress on renewables, which look like a much better bet on the energy supply side in most sectors, as does energy efficiency on the demand side. Zero direct carbon, not net zero carbon.
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