Carbon capture and storage: essential technologies for a cleaner tomorrow

At the conference of Britain’s governing Labour Party in Liverpool last week, two protesters squeezed in a white elephant costume with “carbon capture and storage” written on it. Last month, Nature published a paper suggesting underground carbon dioxide storage capacity is much less than previously thought. These two happenings link a continuing hostility from environmentalists towards one of our key climate technologies.

Of course, it’s right that government funding for any environmental project should be carefully scrutinised at a time of tight budgets, to ensure it’s worth its costs. Of course, it’s right that scientists should dig carefully into assumptions about key climate mitigation measures to ensure their potential isn’t overstated.

A deep dive

The Nature paper, ‘A prudent planetary limit for geologic carbon storage’, was authored by a group of heavyweight climate scientists, mostly from European universities and research institutions. It applies several limitations on subsurface carbon dioxide storage, calculating that this reduces possible storage from estimates of 10,000-40,000 gigatonnes in the scientific literature, to about 1,460 gigatonnes.

This would be enough to limit global warming by 0.7°C. Although still significant, this limit would be problematic for climate strategies that rely on “overshoot”: allowing the build-up of atmospheric carbon dioxide, then removing up to 2,000 gigatonnes by end-century.

Contrasting theories

But several informed observers pointed out serious problems with the paper, including the Carbon Capture and Storage Association, experts writing at the Science Media Centre, and my colleague Jack Andreasen Cavanaugh at the Center on Global Energy Policy at Columbia University.

The study applies extremely conservative, and in some cases arbitrary-seeming, criteria to negate a large part of subsurface storage.

For instance, it rules out injection of CO₂ at depths of more than 2.5 kilometres below surface, although some existing CCUS projects, such as Aquistore in Canada, already inject deeper than this. A greater thickness of overburden should, if anything, improve the storage security the authors are concerned about.

They also rule out injection in offshore settings of more than 300 m of water depth, “owing to both economic and risk considerations”. Their explanation of the technical risk in deepwater injection is not coherent, as it refers to an oil reservoir blowout. Again, CO₂ injection in Brazil has been carried out for about a decade in waters 2,000 metres deep.

Possible oversight

The paper does not obviously make any attempt to estimate storage costs for excluded areas; the ostensibly economic criterion is therefore completely arbitrary. If meeting our climate goals is essential (as the authors undoubtedly agree), and if CCS is an essential part of that, then we should be willing to bear substantial costs. Environmentalists are certainly willing to accept very high costs for certain favoured approaches to reaching net-zero emissions.

These restrictions on water and reservoir depth contribute the two biggest reductions to the theoretical storage capacity. Without them, the potential would be 7,200 gigatonnes – far beyond any likely requirement well into the twenty-second century. Careful regional geological assessments of areas such as the UK, Norway and US, for instance, find available volumes well above those estimated by the Nature authors.

The paper also assesses only subsurface storage in sedimentary rocks, not the very large potential for mineralising CO₂ by reaction with igneous rocks such as basalt and peridotite, either underground or on the surface. Mineralisation provides assuredly permanent storage, and produces solid, non-toxic products that can be used, for example, as building materials.

Even if the paper’s conclusions are taken at face value, storage capacity would be more than enough for CCS to be a large part of the climate solution. 0.7°C of mitigation would, for instance, make the difference between seriously exceeding the Paris Agreement’s target of no more than 2°C of heating, and achieving its aspiration of limiting warming to 1.5°C. The estimated storage is easily enough to absorb required capture amounts under plausible climate scenarios for over 100 years.

A need for awareness

Given these obvious objections, it’s hard to escape the feeling that this paper shows either an excess of conservatism, or that the authors chose a methodology to support scepticism on CCS as a valid part of the climate solution.

Both the Nature paper itself, and the media response to it, highlight a worrying wider attitude to carbon capture and storage (CCS). Breakthroughs in renewables, batteries and electric vehicles are rightly celebrated. Progress in CCS is downplayed or receives only qualified praise, while negative news is widely spread.

Some usually well-informed and factual publications have covered the carbon storage paper mostly uncritically, while also committing a blunder that media continually repeat, confusing volumes of carbon capture and storage (from point sources such as industry) with carbon dioxide removal directly from the atmosphere. Simply reading the paper itself should have cleared this up.

Progress in CCS has been much less so far than the climate needs. This is because of insufficient and inconsistent support from governments and industry, not because of a lack of storage capacity, nor any fundamental technical or economic failing.

Disastrous consequences

Veterans of the misguided “peak oil supply” panics of the 1970s and early 2000s will shake their heads at the paper’s suggestion of “treating geologic carbon storage as a scarce resource that needs to be deployed strategically to maximise climate benefits rather than treating geologic carbon storage as a limitless commodity”. It would be disastrous if we cut back on CCS projects on industrial or power plants today, for the fear that we might not have enough storage space for atmospheric CO₂ removal in the year 2200.

This paper, and the commentary on it, take us in exactly the wrong direction. Instead of highlighting a genuine issue, they raise unnecessary worries about CCS that will be picked up by the general public and make it even harder to get future carbon storage projects over the finish line.

Robin M. Mills is CEO of Qamar Energy, and author of The Myth of the Oil Crisis