NEGATIVE NET CARBON. DIRECT EXTRACTION OF CO2. IS IT A GAME CHANGER?

DIRECT EXTRACTION OF CO2 FROM THE ATMOSPHERE.  IS THIS REALISTIC? IF SO IT COULD BE A GAME CHANGER?

A Swiss company has told the Carbon Brief website that there is a real prospect of reducing the costs of the direct extraction of carbon dioxide from the atmosphere to a point where it will be possible to consider large scale operations that could substantially offset current emissions and even feature in attempts to reduce concentration levels, in the so-called “zero carbon” or “net negative CO₂” policies that many people consider are implied in the Paris agreements. If their promises are realistic, then this would be a truly revolutionary development, with profound implications for our approach to climate policy. But there will be a lot of questions to answer on the way.

A Swiss company has opened what is believed to be the world’s first ‘commercial’ plant that sucks carbon dioxide from the atmosphere, a process that could help reduce global warming, it is claimed. The firm, Climeworks, expressed confidence they could bring down the cost from $600 per tonne of the greenhouse gas to $200 in three to five years with a longer term target of $100. This is almost an order of magnitude lower than previous estimates of the cost of direct carbon extraction, widely assumed to be around $1000 per tonne.

This is also one of the two most important candidates for a game changing technology breakthrough that I identified in my 2016 submission to the House of Lords Inquiry, which can be viewed as a separate page on this site. If it proves to be feasible then it may represent a considerable advance on what has hitherto been considered the only feasible route to net negative carbon, the so-called bio-energy with carbon capture and storage (BECCS) approach. Shortcomings of the latter include the limited supply of bio-energy, not least due to land availability constraints, and controversy over whether this really represents a sustainable approach[1]. So direct sequestration, if feasible, is very attractive.

There are clearly still a large number of outstanding questions before we get too excited by this prospect.

Is $200 or $100 per tonne really achievable? And if so is the technology scaleable? And to what scale[2]? If it is scaleable, it seems likely the world could be seeking an expansion of the process well beyond the 1% of current emissions suggested as an ambitious target by Climeworks.

The other big question is how to dispose of the CO₂ after its capture. This is a big issue, and a very substantial part of the cost for all carbon capture technologies, including those based on removing the CO₂ from fossil fuel combustion. This cost needs to be factored in and is bound to be a fairly substantial element in the total. It does not appear to be included in the Climeworks figures. Moreover the disposal issue, at scale, will raise its own environmental and risk issues.

But if these questions can be answered this could be a very significant technology advance. It is certainly not the magic bullet that solves all problems, but it could have some important consequences for the way we look at climate policies. Why?

First, one of the most terrifying features of the climate change threat is the apparent irreversibility of the processes involved. CO₂ emissions are cumulative. If they cannot be removed on any scale, then there is a real risk of a future where the climate science starts to tell us there is no return.  At this point priorities would take a dangerous turn towards survival rather than the global idealism, or at least hope, that underpins global agreements. But it is not just that dealing with a very expensive problem is psychologically more attractive than coping with the prospect of unavoidable catastrophe. Ability, in principle at least, to partially reverse out of the worst consequences, puts a finite bound on the costs of making the wrong policy choices. Inter alia it ought to increase the available policy options.

Second, and more importantly, direct sequestration has the potential to change the basis of policy in relation to carbon pricing. I have previously commented on the weakness of traditional cost benefit analysis (CBA) in this context. CBA fails to provide a basis for a carbon price, and the failure is in large measure due to an impossible number of uncertainties (in climate, geographical and economic impact) to which probabilities cannot be assigned from any established base of knowledge. But if we have a clear way of putting a cost on CO₂ removal, then we have at least a first approximation to a “true” cost of CO₂ emissions. This might inter alia provide a better justification for effective carbon pricing, and even for global adoption of a “common” rate of carbon tax. It could be a much more hard-edged approach than complex negotiations over carbon trading schemes, which, as with the EU Emissions Trading Scheme, have so far failed to deliver adequate carbon prices.

These are obviously early days for direct extraction technologies, and we should avoid premature optimism, but this could be an important part of the geo-engineering landscape to watch.

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[1] One of the reasons BECCS is controversial is that its justification requires careful analysis of the entire chain of processes involved, starting with the cultivation of the bio-crop and including any ecological or carbon related side effects, as well as consideration of the alternative land uses for food production or other purposes.

[2] Limits to scale might be imposed, for example, by the availability of other input chemicals to the extraction process. But the more serious limitations are likely to be on disposal of the CO₂ gas. A preferred route of extraction might be capture of the carbon in a solid and inert form, such as calcium carbonate, if this were possible.