Geoscience Reference
In-Depth Information
future fossil fuel consumption is likely to rise markedly. A number of nations, such as
India and China, are already thinking about CCS and are participating in the Carbon
Sequestration Leadership Forum. Other than a few exceptions, developed Western
nations have yet to fund CCS in developing nations but this is a likely option in
the future.
It is important to note that there are limitations to CCS technology other than
those already cited. Chief of these is that, as currently envisioned, CCS systems
only apply to power stations where the amount of carbon dioxide being captured
is of sufficient quantity for CSS to be practically feasible (even if it is still not
generally economical without some support). This limits our ability to reduce carbon
emissions.
The argument against CCS is that it facilitates continued reliance on fossil fuels.
There is also a sustainability argument in that in the long term (many decades and
centuries), as fossil fuels dwindle, other longer-lived energy resources will need
to be exploited. The nuclear option is currently one of the few technically proven,
greenhouse-friendly options available, although it has its own associated environ-
mental concerns. Because of these some green campaigners view CCS as the prefer-
able investment option.
The counter argument to this is that because carbon capture is predominantly
related to fossil fuel consumption, and because consumption of finite fossil fuels is
not sustainable in the long term (beyond a couple of centuries as our main energy
resource), fossil fuels' (non-CCS) climatic impact, although very significant, will be
eventually curtailed. CCS could therefore have a limited role in providing time while
we transfer to a sustainable, long-term energy strategy. Nonetheless, if considerable
quantities are to be stored then the tightness of the geological formations used needs
to be greater than 60-95% for 500 years, as the IPCC's 2005 special report estimates,
if we are to completely prevent a long-term climatic impact.
The IPCC (2001a) SRES scenarios for the 21st century assume 1000-2200 GtC
consumption and one might presume approximately double this if we included the
22nd century. This last greatly exceeds the estimated carbon release that triggered the
IETM/PETM. This thermal maximum (and indeed the earlier Toarcian event) lasted
well over 100 000 years. Consequently, from a palaeo-environmental perspective if
CCS is used to store hundreds or thousands of gigatonnes of carbon then significant
leakage needs to be minimal over this kind of 100 000-year time frame if a similar
thermal event is to be avoided. (It is interesting to note how this perspective compares
with that for storage of nuclear waste: see section 8.2.5.) Upon further technology
appraisal it may be that such storage tightness is not achievable. However, this does
not mean that the technology is without value. It would appear from both the Toarcian
and Eocene carbon isotope excursion (CIE) events that the build-up of atmospheric
carbon took tens of thousands of years. We know that the biosphere coped with both
these events (ecosystem disruption, biome latitude migration, greatly increased global
precipitation and erosion notwithstanding). What we do not know, even loosely, is
how the biosphere will react to at least 1000 GtC injected into the atmosphere in a
century. Even if carbon-capture technology could help reduce our 21st- (and 22nd-)
century anthropogenic impact to 'only' that of an Eocene event, it would confer
major benefits. It would give more time for the biosphere to adjust and contribute
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