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Carbon challenge

Engineers need to come up with a way for people to use fossil fuels without putting CO2 into the atmosphere, says Jon Gibbins

This is a terrible time to be an engineer in the sense that there is a real problem. And the problem is not how soon we have a utopian world to live in, but whether we can get on top of climate change before it gets on top of us.

Once we lose control of the climate, all we have got are a few desperate geo-engineering options to try and then we have got to take what is coming to us. And one of the most depressing things would be that what is coming to us is coming very slowly. We would be sitting there knowing that things were going to get worse — more pressure on water and food production — for quite a long time. The fallout from that would be pretty severe.

If you think you are partly responsible for averting that, then you may or may not enjoy that responsibility, because if we fail the results will lie with us and with many further generations. This is not a fairy story; it is actually reality. It is hard to believe it, but it is.

This is the challenge. We can put about 500 gigatonnes of carbon into the atmosphere and have a 50:50 chance of avoiding dangerous and possibly runaway climate change — and there is at least five times that amount of carbon available in fossil fuels. What we have got is an accessible resource that people would like to use and it is difficult to stop them using — fossil fuels — and a very finite resource in the form of the atmosphere. Avoiding dangerous climate change, rather than running out of fossil fuels, is the real challenge.

An important point that people who rattle on about renewables or nuclear do not recognise is that if you want to claim any benefit environmentally for using these instead of fossil fuel, you have to say how that fossil fuel will remain unused for at least a millennium. Almost nobody who promotes non-fossil energy takes that into account.

What we need to do is come up with technologies that will allow people to use fossil fuels without putting the CO2 into the atmosphere. It is probably easier to persuade people to use fossil fuels in that way than it is to persuade them not to use fossil fuels at all. Then, if you do carbon capture and storage, you have burnt the fuel. The carbon is now CO2 locked away a kilometre or more underground and it would be hard for people to get it out again, even if they wanted to.

We are looking at three basic ways to capture the CO2: post-combustion, where you scrub it out of the flue gas using a reversible reaction with a liquid solvent; pre-combustion, where you make CO2 and shift all the chemical energy in your fuel to hydrogen; and oxyfuel, where you burn the fuel in oxygen and get a mixture of CO2 and water vapour. In all of these, you take the CO2 away and store it in porous rocks under an impermeable sealing layer underground.

For coal power plants with carbon capture and storage (CCS), all three of these capture options are predicted to give you a cost and performance that are very similar. We are not looking at a particular winner. It is more like renewables where there are many different technologies with different purposes.

For early projects, costs will be higher — that is the same for any technology — but what we do on early projects from now until 2020 is significant, because if we are not globally heading on a steep downwards emissions path, fairly soon after 2020 we are probably not going to get anywhere near 500 gigatonnes of carbon limit.

We really do need to have CCS available as an option by 2020, although, as yet, we have not built any power plants with CCS. To have a serious chance of building large numbers of very expensive pieces of kit that will run reliably day in, day out for many decades, you have got to go through two learning cycles. And learning cycles at this scale of plant take around five years.

We are looking at getting the first tranche of new plants constructed very, very quickly. We are then looking at getting tens of these plants built so that we can get onto the second generation, work out the technology, train the people and build up the capacity, aiming for roll-out in developed countries, EU and elsewhere by 2020 and globally fairly soon after that. In the meantime, the plants that are built without capture have got to be built capture-ready — a little bit of thought will make it quite easy to retrofit the technology.

The ability to build large numbers of CCS power plants — which are serious bits of kit — in 10 years’ time is a problem that keeps me awake at night. Something wonderful might come along in the long term but, in the meantime, engineers have got to make something that works and provides a serious political option within the next 500 weeks.

Dr Jon Gibbins is a senior lecturer in energy technology for sustainable development at Imperial College and principal investigator for the UK Carbon Capture and Storage Consortium. The above is an edited version of a presentation made at London’s Energy Institute earlier this year.

Readers' comments (1)

  • Gibbins' list of CO2 capture options has a significant omission: the enhanced olivine weathering championed by, among others, Dr. R.D. Schuiling.

    Given millions of km^2 of land that currently we consider low-value, it turns out to be fairly easy, in energetic terms, to strew pulverized alkaline earth silicate minerals over it, and take down, if necessary, tens of gigatonnes of CO2 per year.

    It forms stable carbonates that come down only to the surface. They do not need burial.

    The energy with which a silicate surface pulls a CO2 molecule out of air is intrinsic to the two substances, so the low-value land does not need to be sunlit. It can be a cold polar desert, or conceivably even a wet desert such as the South Pacific

    This air-cleaning method is not specific to coal. It cleans up after yesteryear's coal burning, cars, butane lighters.

    That means it we can start doing it any time we're ready. We don't have to build new, special CO2 emitters because pulverized olivine will work with the ones we already have.

    The unclean coal plants now being built in China, and soon to be built there, are capture-ready with respect to this, the easiest CO2 capture method. Silicate dustmotes in Antarctica or Siberia will deal with their CO2, if and when we create those dustmotes.

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