The case for carbon capture and storage is compelling yet there are questions about its economic and technical viability. Matthew Lockwood explores the opportunities and challenges of this approach in reducing carbon emmissions.
Well over half of the world’s carbon emissions come from a few thousand power stations and large industrial sources. Many use coal as a fuel, and since China, India and the USA all have large domestic reserves, the security of supply and low cost of coal mean that it will be hard to cut its use any time soon. That is why the idea of capturing carbon dioxide at the point where it would otherwise be emitted to the atmosphere, and then sequestering or storing it in depleted oil-fields or underground aquifers, or simply dissolving it into the oceans, is now attracting so much interest.
However, while the case for carbon capture and storage (CCS) is compelling, there are many questions about its technical and economic viability.
One obvious concern is that the stored carbon dioxide may leak out. In its widely respected 2005 report on CCS, the InterGovernmental Panel on Climate Change (IPCC) reports a high degree of confidence that leakage is very unlikely in “appropriately selected and managed geological reservoirs”, while the release of carbon dioxide dissolved in the sea would take hundreds of years.
More of a problem is that suitable locations for carbon storage are not always that near to the power stations and factories where the carbon is emitted. The IPCC report estimates that there is a limit of between 20 and 40 per cent on global fossil fuel emissions that could be stored.
Nevertheless, this would make a huge contribution to tackling climate change, and there is some experience of piping and storing carbon dioxide in gas-fields and saline aquifers in Norway, Canada and Algeria. So if the capturing of carbon can be made to work, there will be no technical barriers to the widespread application of CCS.
Much attention currently focuses on coal-fired power stations, because they are the major part of the problem, and will also require carbon capture on a much bigger scale than has been attempted in the past. Currently there are two leading contenders for capture technology.
One –called post-combustion - removes carbon dioxide from the flue gases of power stations, after the coal has been burnt in air. This is not a new technology and is used in the natural gas processing industry, but not at the same scale or with coal as a fuel, so there are still some outstanding technical uncertainties. The big attraction of the post-combustion approach is that it can be retro-fitted to existing coal plants, including those of the type that China is currently building so rapidly.
By contrast, pre-combustion capture works only in combination with a new kind of coal-fired power generation involving a process called gasification. Coal is not burnt, but rather heated up under pressure and converted into a cocktail of gases that includes carbon dioxide. Pre-combustion capture is far easier, more efficient and potentially cheaper than post-combustion capture, and is already used on a commercial basis at a smaller scale in fertilizer manufacturing. It also produces hydrogen as a by-product, which could be really helpful if fuel cell technologies take off. The drawback is that only a handful of power stations using gasification exist so far, and the basic power generation process is expensive.
The costs of applying CCS to coal-fired power generation are still uncertain, whichever technological approach is taken. There are a number of estimates from different sources around, but most put the additional cost of electricity produced using CCS at around 2-4 pence per kilowatt hour. Costs may come down over the long term, but initially at least, CCS will need some form of support to be commercially viable.
Many energy companies think that in Europe that support may come in the form of a price for carbon through the EU emissions trading scheme (ETS). Carbon pricing makes running conventional coal and gas plants more expensive, while plants using CCS will incur hardly any penalties. Under plans put forward by the European Commission, the price of carbon could rise to about €40 per tonne of carbon dioxide, which many analysts think could be enough to make coal with CCS competitive.
All the elements of CCS – capture, transportation by pipeline or ship, and storage – have been tried out at small scale somewhere in the world. But so far no one has demonstrated them all working together, at the scale of a coal-fired power station. Moreover, these technologies are large scale, capital-intensive and there is still an element of technological risk with both pre-combustion and post-combustion approaches. As the Stern Review argued, this makes CCS an ideal area for international collaboration between governments in supporting and coordinating research and demonstration.
But this has so far proved quite hard to do. The Gleneagles Dialogue on climate change and clean energy set up in 2005 was supposed to kick start the process, but progress on the ground has been patchy. The USA made a commitment to develop demonstration of the pre-combustion approach at power station scale, but earlier this year its flagship FutureGen project was called to a halt. The European Commission has said it wants to see 12 demonstration projects up and running by 2015, but is dependent on member state governments to provide the money needed.
In this context it is significant that the UK government has committed to a demonstration exercise capturing carbon from 300-400 MW of coal-fired power generation by 2014. It was decided to restrict the demonstration to projects that use only post-combustion technologies, partly on the grounds that the rich world needs to demonstrate to China and India the technologies that will be needed for retr-fitting existing coal power stations.
This is strongly disputed by parts of industry and environmental groups. They argue that China can and will develop its own CCS demonstrations, and that the pre-combustion approach offers the quickest and cheapest route to get CCS going at scale in the UK. With a new coal-fired power station at Kingsnorth now in the planning pipeline, timing does matter. While the Government is about to consult on what a “CCS-ready” coal-fired power station might look like, the reality is that coal-fired power generation will only become low-carbon when the technology is proven and commercially viable.
Matthew Lockwood is a Senior Research Fellow in Climate Change at the Institute for Public Policy Research. Ippr’s report on eth future of coal-fired power generation in the UK, After the Coal Rush, will be published in May.
