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.