Mike Stephenson, British Geological Survey
In a now famous article in the journal Science, Pacala and Socolow introduced the scientific world to the concept of ‘stabilization wedges’. These are units by which we could measure the amount of effort we’ll need to tackle global warming - while still keeping the lights on. Several of these wedges are needed to get from the ruinous ‘business as usual’ high-CO2 emissions scenario to one where we might reduce global warming to a manageable level.
One of Pacala and Socolow’s wedges consisted of converting coal power plants to gas - in other words to make gas the provider of electricity baseload, rather than coal. They said that to achieve a ‘wedge of carbon abatement’ you could switch 1400 GW worth of 50%-efficient coal plants to gas power stations. This suggestion was rather far-sighted in that it predicted today’s discussions about the potential for natural gas - and particularly shale gas - to provide a lower carbon fossil fuel alternative. Switching from coal to natural gas saves carbon because burning gas in power stations is about half as CO2-polluting as burning coal.
But another wedge they suggested was to introduce widespread carbon capture and storage (CCS) on gas and coal power stations. This is where the CO2 from the power stations is buried out of harm’s way deep in geological formations. CCS has been taken up as Government policy in several countries (for example in Britain), though no large-scale CCS yet operates here. A third suggested wedge was to double the amount of global nuclear power.
But is gas - whether conventional gas or shale gas - really a low carbon fuel? At the moment this question is difficult to answer. There have been relatively few studies and the ones that have been published have been challenged. A recent report for the European Commission (AEA Technology, Climate Impact of Potential Shale Gas Production in the EU) concludes that shale gas compares rather favourably in terms of its overall carbon footprint with conventional gas, particularly if the shale gas is ‘home grown’ and is competing with conventional gas that is imported. This is because of the emissions related to transporting and liquefying imported gas. The effects of substituting gas for coal in countries whose electricity supply is dominated by coal power stations can be radical. For example if Poland switched from coal to gas a 41-49% reduction in CO2 emissions would result. If carbon capture and storage was employed on such gas power stations the emissions would drop even further.
However the chance to develop shale gas and other low carbon wedges is being jeopardised not by their technical feasibility but by their image amongst the public and investors.
The public dialogue on shale gas is becoming increasingly hysterical and irrational. Recent views of shale gas suggest that Blackpool might disappear beneath the Irish Sea because of fracking, or that the Mendips Hills will become volcanoes. Neither of these have any scientific basis. There are also widespread though less extreme views about the safety of CCS and geological disposal of nuclear waste. Views like these diffuse into the general discourse and become the currency of discussion, lowering the quality of the debate and risking bad decisions and faulty policy. This is not to say that there aren’t scientific concerns about for example methane contamination of water supplies or small earthquakes caused by fracking. But the proper business of science in deciding whether gas (methane or CO2) might leak out of the ground is distracted by ridiculous questions that don’t need answering.
But if these geo-engineering wedge technologies aren’t seen as feasible it will be harder and more expensive to achieve the emissions targets we’ve set - and other ‘wedges’ will have to take the strain. In short we may lose technologies that could act as bridges to a lower carbon future.
Most geologists and technologists are confident that shale gas, CCS and nuclear waste disposal can be done safely, and the weight of scientific evidence in these new areas backs these views up. But the science still needs to be seen to be independent and peer-reviewed and it needs to be communicated! Scientists are not naive enough to believe that the results of scientific experiments enter the public consciousness, but their conclusions can, by slow diffusion, improve the quality of public and policy debate so that the right decisions can be made. The public and policy makers, in turn, need to know that science can be rather a slow process, and that single studies may yield ambiguous results. Also they should know that the spectacle of seeing scientists disagree and argue is a sign of progress, not a basis to distrust them.
Having the public (and investor community) on the side of low carbon geo-engineering technologies will help to keep our technology options open. Improving the quality of public debate is helped by doing the right science at the right time, keeping it independent, and communicating it well. This will help to keep the lights on while also meeting emissions targets and keeping global warming at bay.