Environmental Engineering Reference
In-Depth Information
coal exports to the EU of 187% have been attributed to the reduction in the
USA's demand for coal.
38,39
While there were local emissions reductions
during this time frame, due to the sale and combustion of US coal overseas
a net reduction in CO
2
cannot be guaranteed, net global reductions are
dependent on what the USA's exported coal displaced. Similarly, other
countries such as China and India with significant amounts of coal-fired
electricity production may in future reduce CO
2
through a switch to gas, with
the net effect dependent on what happens to the coal that is displaced from
their energy system; if shale gas is simply burnt as well as coal, as appears to
be the case at present, there is no net global carbon saving.
As alluded to earlier, the impacts of shale-gas use on emissions differs
regionally, depending on the incumbent energy mix. In the UK and much of
Europe, where coal-fired power stations are being phased out through a
combination of air quality legislation and climate policy, such as the Large
Combustion Plants Directive and EU Emissions Trading Scheme, shale gas
will most likely displace conventional gas, nuclear or renewables and the net
impact is to increase CO
2
emissions compared to a business-as-usual tra-
jectory. Similarly, a study of the probable end-destination of shale gas ex-
tracted in British Columbia, Canada (an area holding half the technically
recoverable shale gas resources in Canada,
40
where the incumbent energy
system is dominated by hydro-electricity), showed the probable end-
destination of shale gas was not to replace coal-fired electricity but for export
as LNG or to replace conventional gas for use in neighbouring Alberta's
energy-intensive tar sand extraction, perpetuating a positive feedback cycle
of fossil fuel emission production, clearly not a 'transition role'. The
liquefaction and re-gasification of LNG, together with the transport
requirements to the end-user, require additional energy, increasing the life-
cycle GHG emissions of the fuel source and diminishing potential savings
from replacing coal use and hence the potential role as a transition fuel. In
conclusion, there is insu
cient evidence to date that condition (1) is being
met. Shale gas is not displacing an equivalent amount of coal.
The second condition (2) is that increases in energy demand must not
outpace the rate at which carbon intensity of energy supply is reduced. To
date, global energy statistics demonstrate the rate of decarbonisation has
been outpaced by growth in energy demand. On average a 0.3% annual rate of
decarbonisation is observed compared to an increase in global energy use of
2% annually since the industrial revolution and hence a net increase year-on-
year of energy-related CO
2.
41
A six-fold increase in the decarbonisation rate of
global energy demand would be needed to stabilise global energy-related CO
2
emissions, a twenty-four fold increase to begin to deliver the minimum rate of
decarbonisation necessary to provide a reasonable chance of avoiding more
than a 2 1C temperature increase. Could shale gas play a part in accelerating
the decarbonisation of the energy system? Much will depend on whether it is
burnt as well as or instead of coal, as discussed above, and if it does displace
coal, the rate at which it does so. As the emissions intensity of shale gas is
only approximately one third to one half that of coal, its contribution to the
