Carbon Capture. Getting behind the hysteria.

Carbon capture is in the news again, as the new Labour government announces a substantial new programme for the development of the technology. This has attracted a barrage of criticism from both Left and Right, in spite of the fact that carbon capture is widely regarded as an essential component of any mitigation strategy. So it’s worth exploring a bit further.

 

Some technical background.

 

We should get the terminology clear. There are many approaches to carbon capture, including the use of natural processes in the carbon cycle, for example by improved land use, planting trees or through various “geo-engineering” schemes to increase the “fixing” of the carbon in the oceans.  Greens and others, unsurprisingly, tend to favour the most “natural” and least environmentally intrusive of these. 

 

Second, when CO₂ is captured, it can either find a useful purpose, or it can be sent to a safe permanent store. Use in the soft drinks industry will be trivially small, but it can also be used in the production of synthetic fuels. Most recently there has been a lot of interest in synthetic aviation fuel (SAF) for the hard-to-decarbonise aviation industry.

 

Trees are one form of direct atmospheric carbon capture (DACC). But there are also industrial process approaches to direct capture, sometimes referred to as mechanical trees, which rely on established chemical techniques to separate CO₂  from the atmosphere. It’s claimed that the cost of DACC and subsequent storage (DACC+S) could be brought down to below $200/ tonne, a level that could imply total costs of emission-free oil use well within the historical range of oil price variations. Proposed options for storage include geological formations such as depleted oil reservoirs  and the deep oceans

 

Problems with and arguments against the various DACC methods include:

 

·       excessive requirement for land use, sometimes in competition with food production; this will apply to some but not all methods of both a “natural” and industrial nature; this places an upper limit on what they can achieve

·       excessive land use can also have ecological and human rights implications

·       unproven nature and potentially high costs, and, in the case of natural methods, science unknowns around whether particular land-use policies will be net emitters or receivers of CO₂

·       for industrial methods, high energy use requirements

·       the argument that carbon capture is a distraction from the preferred alternative of eliminating fossil fuels

·       in relation to storage, doubts about suitability of locations, safety and permanence; transport of CO₂and injection into storage may also be expensive

 

The above has all been about direct air capture. However it is, for obvious reasons, likely to be much easier and cheaper to capture high concentrations of CO₂  at the point of combustion when it is released from the fossil fuel. A Green version of this technique involves the use of sustainable bio-fuels, known as bio-energy carbon capture and storage or BECCS. BECCS is likely to be severely supply limited in relation to the scale of what is needed. More generally carbon capture can be fitted or retro-fitted to fossil burning plant, including power generation, and this has generally been the main focus of carbon capture and storage policies, usually referred to as CCS.

 

An additional issue for CCS is that it is likely to be less than 100% effective, with a leakage rate of perhaps 10% or more, so it is not a silver bullet.

 

Is carbon capture an essential component of climate strategies?

 

The IPCC is fairly clear that carbon removal, ie DACC, will be an essential component of any feasible route to a sustainable future. It also endorses continued use of fossil fuels, where this is accompanied by CCS, as one of the options for getting to a net zero future. CCS is also supported by the UK Committee on Climate Change (CCC) as part of a UK strategy aimed at this objective. Both these bodies have the advantage of access to a huge body of scientific and technical advice on the subject, in the context of means to mitigate climate change.

 

So should the UK government be promoting CCS?

 

On the basis of IPCC and CCC advice, the principle of promoting CCS seems to bejustified. There may be alternative means of getting to net zero, but if this is the quickest and cheapest option, then there should be no reason to object to it. Moreover this will not just be a UK issue. Much of the world is even more locked into fossil-based technologies than the UK, so the potential of CCS as an interim or transition technology may be quite important.

 

Whether it has a positive contribution to a UK industrial strategy is another question. Potentially the answer is that it does. Countries like Germany have a much higher lock-in to fossil fuel. But as ever, geography and trading relations matter. Not all countries will enjoy the storage options that the UK has, and Brexit will make the potential to exploit European markets harder.

 

Finally there is a history to this. In 2015 the Cameron/ Osborne government cancelled a CCS programme after the spend of £ 100 million of public money and substantial private sector investment of time and resources. This was part of a major rolling back of  Cameron’s Green promises and accompanied the slashing of budgets on other “easy win” measures such as home insulation. As a marker of determination to take net zero seriously, the Labour government's move is a welcome step. But it does not detract from the need to continue to explore the wider DACC options for carbon removal and storage, nationally and globally.

CLIMATE SCIENCE. RESIDUAL UNCERTAINTIES THAT DO NOT CHANGE THE UNDERLYING MESSAGE.

Understanding Time Lags Important for Climate Policies.

“Cumulative carbon”, the fact that human emissions of CO₂ are removed only slowly from the atmosphere through the natural carbon cycle, is the essence of the climate change problem. Given the thermal inertia of our planet it may produce a substantial time lag between effective action, to limit emissions, and actual stabilisation of temperatures, equivalent to the operation of a domestic heating radiator on a one way ratchet. Some climate scientists believe this effect may have been exaggerated, and will be largely offset by other elements in the natural cycle. Even so there is a consensus that we need to move to a world of net zero emissions and beyond.

So much of the predictive element of climate science has been borne out by observation that it is easy to forget there are still major gaps in our understanding and major uncertainties that are very relevant to understanding what climate policies are necessary to (ultimately) stabilise global temperatures.

The slow but seemingly relentless upward trend in global surface temperatures sits firmly in the middle of past model predictions, and denials that it is actually happening (the famous Lawson “hiatus” based on cherry picking outlier el Nino effects), or that it has nothing to do with human contributions to greenhouse gas concentrations, look increasingly threadbare and ridiculous. There is no doubt that human-induced climate change is with us, and that it is dangerous.

However, although the science makes it clear that urgent emission reductions are essential, it is much less clear how much leeway we have, and whether the 1.5^o C or 2.0^o C “targets” are attainable. The uncertainties manifest themselves in discussions over the time lags involved, for example between stabilisation of the atmospheric concentration levels of CO2 and stabilisation of global temperature. These questions relate in turn to complexities of the natural carbon cycle and the

The issue of time lags is in some ways politically important. Thomas Stocker, then co-chairman of the IPCC Working Group I (assessing scientific aspects of the climate system and climate change), and addressing the Environmental Change Institute in Oxford in 2014, argued that “committed peak warming rises 3 to 8 times faster than observed warming”. The implication is that there are very substantial time lags. In this case temperatures could continue to rise, perhaps for several decades or even centuries, even if net human emissions were reduced to zero. Similar comments can be found from other climate scientists. It has even been suggested that the thermal inertia effect, considered on its own, could stretch the lag to about 200 years – the time for heat equilibrium adjustment to reach the deep oceans.

The intuitive physical explanation of long time lags is simply the phenomenon of thermal inertia. When we turn up the radiator at home it may take an hour or more for the room to reach a new equilibrium temperature. Global warming, in this analogy, is a radiator heating system on an upward ratchet. The issue for humanity is that by the time temperatures become really uncomfortable, we have already ratcheted up the future temperature to which we have committed. If this is a real danger it dramatically increases the risks associated with climate inaction or “business as usual” trends. It is also creates an alarming image of climate change as a kind of doomsday machine in which humanity is trapped through its failure to anticipate and respond.

However rather more optimistic views have been presented by other scientists. In 2014 Ricke and Caldeira[1] argued that the lags had been seriously overstated, suggesting a time lag of only ten years as a more appropriate estimate. Oxford-based climate scientists, such as Myles Allen, have also suggested that stabilising atmospheric concentrations could lead to a comparatively early stabilisation of global temperature.

The main reason is the potential offsetting effect of the absorption of incremental carbon through the various elements of the natural carbon cycle, including ocean CO₂ uptake and the behaviour of biosphere carbon sinks. However there is no natural law that requires such a balance of effects, and the reality seems to be that we are trying to compare two magnitudes, both of which are of major importance but are also difficult to measure with precision. If the effects broadly cancel out over particular timescales, this is essentially a numerical coincidence within the modelling effort. We can expect future research, better measurement, and associated modelling, will gradually improve our understanding.

But melting ice caps are a separate story!

The above discussion does not however cover all the long time lags involved. One particular concern has to be the polar ice caps. If global temperatures reach the point where these start to melt, then the consequential effects in the form of rising sea levels will go on for centuries. Ice sheets, as opposed to sea ice, can, like the retreating glaciers, only be restored by precipitation. That will be slow and net annual ice gain will probably depend on conditions associated with a fall in global and polar temperatures to or beyond what used to be regarded as normal.

And the policy implications of these uncertainties?

In reality the consequences for policy of differing estimates can be exaggerated, since there is agreement on most fundamentals. Most modelling now recognises that stabilisation of temperature, even at a higher level, requires progress to net zero human emissions. Importantly, this is probably unachievable without substantial measures to remove CO2 (and other gases) from the atmosphere.  In practice processes for carbon sequestration are likely to be very expensive process. They represent a form of geo-engineering.

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[1]Maximum warming occurs about one decade after a carbon dioxide emission. 2014, Ricke and Caldeira

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.