Can we solve climate change by capturing carbon?

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In today’s Mail on Sunday climate scientist Myles Allen tells us that our current climate policies are not going to solve the problem. All those wind farms, carbon taxes and cap and trade policies just won’t get the job done. On this I am happy to agree with him, existing policies are in incoherent contradictory mess. However his solution does not seem to offer much more hope than our existing and failing policies. In essence he is arguing that we just capture and store most of the carbon dioxide we emit.

He begins his argument:

There’s been a lot of talk about ‘unburnable carbon’ – the carbon we shouldn’t burn if we are to keep global temperature rises below 2C. A catchy phrase, but can we really tell the citizens of India of 2080 not to touch their coal?

And to those on the other side who think that solar and nuclear will someday become so cheap we will choose to leave that coal alone, I’m afraid you have some basic physics working against you.

This claim about the “basic physics working against you” is probably just as apt for Allen’s solution, but I’ll get to that later.

Instead of relying on building nuclear power plants, solar panels, or electric cars, Allen proposes that we largely just bury carbon:

Fortunately, there is a solution. It is perfectly possible to burn fossil carbon and not release carbon dioxide into the atmosphere: you have to filter it out of the flue gases, pressurise it, and re-inject, or ‘sequester’, it back underground.

If you’re using fossil carbon to drive a car or fly a plane, you just have to pay someone else to bury CO2 for you.

The only thing that actually matters for climate policy is whether, before we release too much, we get to the point of burying carbon at the same rate that we dig it up.

How much can we bury? Perhaps as much as 50% by the 2040s, and this may not cost that much:

Even on relatively pessimistic estimates, if the sequestered fraction rises at one per cent per 10 billion tonnes, it would be getting on for 20 years before the cost of carbon capture would exceed the £100 per year and rising that the average UK household already pays in assorted windfarm subsidies.

The impact on petrol prices is even less dramatic: 50 per cent carbon capture, which we might reach by the 2040s, might add 10p to the cost of a litre of petrol. That’s well under what we already pay in fuel taxes which, we are told, are supposed to help stop climate change.

50% sounds quite good, and will get us most of the way to solving the climate problem. But, what would capturing 50% of carbon emissions involve? In many respects it’s just the reverse of the oil industry, but instead of pumping the stuff out of the ground and burning it, we take it from the air, liquefy it and then pump it underground. This oil industry comparison has been made brilliantly by Vaclav Smil and provides a serious reality check on any proposal to capture a significant amount of CO2 emissions:

Let us assume that we commit initially to sequestering just 20 percent of all CO2 emitted from fossil fuel combustion in 2010, or about a third of all releases from large stationary sources. After compressing the gas to a density similar to that of crude oil (800 kilograms per cubic meter) it would occupy about 8 billion cubic meters—meanwhile, global crude oil extraction in 2010 amounted to about 4 billion tonnes or (with average density of 850 kilograms per cubic meter) roughly 4.7 billion cubic meters.

This means that in order to sequester just a fifth of current CO2 emissions we would have to create an entirely new worldwide absorption-gathering-compression-transportation- storage industry whose annual throughput would have to be about 70 percent larger than the annual volume now handled by the global crude oil industry whose immense infrastructure of wells, pipelines, compressor stations and storages took generations to build.

Let’s rephrase this calculation. To capture half of global CO2 emissions would involve shoving around, and pumping underground, volumes of liquefied CO2 that are more than four times greater than that of the global oil industry. Allen proposes that we can get this in place in about thirty years. This scaling up is truly mind boggling, just think about the number of pipes we would need to build. Imagine also if we doubled CO2 emissions by the 2040s (a not unrealistic proposition if we made CCS the cornerstone of climate policy). How a CCS industry this big can be put in place by the 2090s, let alone the 2040s is pretty doubtful.

And this ignores the incredible legal issues around where to put these CO2 dumps (and I suspect they will be called dumps). The difficulty getting communities to host underground radioactive waste depositories (or dumps) does not exactly indicate that communities will be leaping over each other to accept CO2 dumps that may start leaking and killing people (at least that’s how predictable scaremongering campaigns will phrase it.)

So no, the laws of physics and the numbers seem to be against Allen’s solution. This of course is not to say carbon capture and storage does not have a role to play (think about the difficulties of making billions of tonnes of steel without coal.) However, it’s clear the solution to climate change must principally involve an energy transition away from fossil fuels, reduced deforestation and a more rational use of energy .


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