Environmental Engineering Reference
In-Depth Information
the ground, growth in energy demand must not outpace carbon intensity
savings and it must be part of a pathway towards truly low carbon energy
sources. How could this be achieved? There are two plausible scenarios where
shale-gas exploitation could be consistent with climate change agreements.
Firstly, if there were an introduction of a global climate regime with a cap
commensurate with 2 1C and/or, secondly, if the associated CO
2
were pre-
vented from reaching the atmosphere via carbon capture and storage (CSS).
To take the first scenario, an annual or periodic global limit on the
amount of CO
2
that can be released into the atmosphere is set. Regulated
entities, nations, cities or industrial actors, must then be bound by some
permitting regime, which may or may not involve carbon trading or taxation.
In this system, shale gas could be used within a system where CO
2
release is
limited to a set global cap. This avoids the indirect emissions implications of
the national local measures. However, such a system would require a global
agreement, including both developed and developing countries alongside
globally agreed administration systems. At present, global negotiations are
not suciently advanced for this to become a reality in the near- to medium-
term future.
The second scenario, perhaps in conjunction with the first, is to prevent
the majority of emissions associated with shale gas from reaching the at-
mosphere. If shale gas is used for combustion, this requires carbon capture
and storage technology and a socio-economic system that facilitates its de-
ployment. The principle of CCS technology is ostensibly straightforward: the
CO
2
is removed from the exhaust stream of a large point source, pre- or post-
combustion, and transported to a long-term storage site, such as an old oil
or gas field or saline aquifer. The technology has significant potential as
many of the individual steps of the process are well established in different
industries. The challenge is to assemble all steps together to ensure the long-
term safe storage of CO
2
and to do it at the gigawatt scale. The technology is
perhaps most promising when allied with biomass combustion to deliver net
negative emissions.
To date approximately eight large-scale carbon capture plants are in op-
eration, predominantly deployed to recycle the CO
2
stripped during the pre-
processing of natural gas for use in enhanced oil recovery.
47
No carbon
capture and storage (CCS) projects are as yet coupled to electricity generation
plant, although two carbon capture plants are under construction (Boundary
Dam, Canada, and Kemper County, USA) and intending to capture CO
2
for
enhanced oil recovery rather than for long-term storage.
47
To put the world
on a track to a 2 1C future, the International Energy Agency's 450 Scenario
requires CCS technology to capture and provide long-term storage of 2.5 Gt
CO
2
by 2035, or approximately 870 large-scale CCS plants attached to long-
term storage: a build rate of approximately 40 per year between 2014 and
2035.
48
To realise this potential, the build rate of these plants needs to be
significantly accelerated, at a pace incompatible with delays for a decade or
more. Such a roll-out will require substantial economic incentives and
regulatory support.
