Sustainability and policy - Climate Change: Biological and Human Aspects - page 471

tightness needs to be such that the carbon dioxide is secure for over a thousand years.
One problem is that exploratory drills and oil- and gas-extraction processes serve to
undermine tightness. Well-capping technology is reasonably developed but may need
optimising. Estimates vary, and further work needs to be done, but optimistically it
is thought that leakage could be 0.004-2.4% on a 1000-year horizon. Further, some
0.03% leakage might take place during transportation and injection (Department of
Trade and Industry, 2003). Less optimistically, the IPCC Special Report on Carbon
Dioxide Capture and Storage (IPCC, 2005) estimates that the technology could be
reasonably assumed to be capable of storing 80-99% for 100 years and some 60-95%
for 500 years.
There is another key advantage to using oil and gas fields, which is that the actual
process of storing carbon dioxide can be used to help extract remaining oil and gas.
Pumping in carbon dioxide at the base of one end of the field drives remaining oil
and gas further away and upwards. This is known as enhanced oil recovery (EOR).
It is particularly attractive because it helps extend an oil or gas field's economic life
and offset the cost of the carbon-capture exercise. It also means that the field provides
more energy, which is itself important as the carbon dioxide from power-station flue
gases needs to be compressed, and then pumped from the power station before being
injected into the geological structure. This takes energy and so can offset (in energy
terms) the utility of carbon capture.
Estimate costs per tonne of carbon dioxide emissions reduced by carbon capture
vary both due to the uncertainties associated with the new technology and because
much depends on the locations of the geological fields and the power stations. Stor-
age costs without EOR could be about £30-90 t − 1 (2003 prices) and with EOR
significantly less. (For comparison it is interesting to note that the price of car-
bon on the EU trading scheme in the latter half of 2005 was around £22 t − 1 .) It
should be noted that if EOR was always economically viable then the oil companies
would always be using it. That they do not means that governments must provide
a long-term economic and regulatory framework to ensure the process's economic
viability.
Although it is early days, the suggestion is that fossil fuel power stations with
carbon-capture methods have costs comparable with nuclear power and offshore
wind energy. The Policy Exchange, a British think tank, in 2008 estimated carbon
storage reduction costs for a small-scale pilot plant to be £70 tCO 2 − 1 (£257 tC − 1 )
but if carbon capture was rolled out in a large scale then costs might be just £30
tCO 2 − 1 (£110 tC − 1 ) and incur an annual extra cost per household of around £60:
this would make carbon capture and storage coal-fired electricity plants roughly as
expensive as wind energy. It also estimated that fitting CCS to UK plants could
cut emissions by 20% by 2020 and global emissions by between 28 and 50% by
2050. (The 2007 Stern review estimated that CCS has the potential to contribute up
to 20% of global CO 2 mitigation by 2050. Furthermore, to achieve stabilisation at
550 ppm without CCS will increase costs by more than 60%.) However, because
carbon capture is not immediately economic, the prospects for wide-scale adoption
of the technology in the short term are unrealistic. What is more easily possible is to
ensure that any new fossil fuel power stations are built as 'capture-ready' so that CCS
can be added later. This is particularly important for less-developed nations, where