Carbon Capture and Storage
A lot of noise has been made recently about Carbon Capture and Storage technology, most recently with the UK Government backing the building of four new coal fired power stations subject to them implementing Carbon Capture and Storage (http://news.bbc.co.uk/1/hi/uk_politics/8014295.stm).
CCS is a very attractive idea, which basically does exactly what it says on the tin, captures the carbon dioxide generated when the coal is burnt and then stores it rather than releasing it in to the environment. This is attractive because there are still large reserves of coal available, and the main reason for not using them is not because of the cost of extraction but rather their CO2 emissions. Coal fired power stations have always been attractive as base power generation since they are able to change load comparatively fast (to match the generating power required) and are fairly easy to operate, well understood (the fuel is burnt, bosh!) and reasonably safe (for instance there is not the safety stigma associated with nuclear power).
There are three methods of Carbon Capture, pre-combustion, post combustion and oxy-fuel combustion. Pre-combustion capture involves removing the carbon before the burning takes place, typically by gasification and the water-gas shift reaction, which produces hydrogen and carbon dioxide, the carbon dioxide is then captured and the hydrogen is used in the power station. Post-combustion capture scrubs the exhaust gases of CO2 and Oxy-fuel combustion burns the fuel in pure oxygen, allowing the CO2 to be extracted much easier (there is predominantly only CO2 and H20 in the exhaust).
The storage element will be done by pumping the gas into either empty oil wells (as is already done in some rigs in the form of Enhanced Oil Recovery (EOR) to extract more oil from near empty wells), or into deep sea saline aquifers. This presents two main difficulties, firstly the need to transport the CO2 to these locations, and secondly who is responsible for monitoring them (and who gets to use them!) since they will be offshore, and this means there will be the need for international co-operation.
It should also be noted that the use of CCS technology will inherently use more power than a similar facility without the technology, and so is not likely to be economically viable until the market is levelled, either by making the use of the technology mandatory, or offering some incentive (such as tax on CO2). The UK Government has already set up Carbon Budgets (see the Climate Change Act 2007).
There is loads of information available on the internet about this technology, and it has featured recently in many issuse of the IMechE magazine Professional Engineering (www.profeng.com). CCS provides a potentially eco-safe, and politically secure energy supply for the UK, as well as ensuring steady supply and looks like a promising area to be in at the moment…
- Mike
