Environmental Engineering Reference
In-Depth Information
carbon cap, the unconstrained use of shale gas is inconsistent with the
carbon budgets necessary to avoid dangerous climate change.
1 Introduction
Shale gas has been hailed as both a climate change hero and villain. Pro-
ponents have argued that it has displaced higher-carbon fossil fuels in elec-
tricity generation and transport in the USA, reducing national emissions,
whilst there has also been widespread reporting in the popular press that
shale gas could have a greater climate change impact than burning coal. In-
deed, the International Energy Agency (IEA) concluded in its World Energy
Outlook special report on the topic that substantial growth in unconventional
gas use in the global energy system would result in very significant levels of
climate change, with a rise in temperature of the order of 3.5 1C.
1
As with any energy technology, there are multiple perspectives to address
when considering the climate change impacts of shale gas. These are largely
related to the boundaries of the analysis. The following have been considered
within the scientific and policy literature, with most attention falling on life-
cycle estimates and comparisons of Greenhouse Gas (GHG) emissions:
Life-cycle climate impacts, normalised per unit of gas, for comparison
with other sources of gas, e.g. conventional production from the North
Sea or Liquified Natural Gas (LNG) imports from the Arabian Gulf;
Life-cycle climate impacts, normalised per unit of electricity, for com-
parison with other generation sources, e.g. nuclear power or coal;
Cumulative impact of emissions from shale gas within the global energy
system; and
Indirect investment and policy impacts on the energy system of novel
gas reserves.
This chapter provides an overview of research on these issues, identifying
the key sources of emissions in shale gas production and situating this
within energy systems in order to understand the wider implications for
climate change.
2 Life-cycle Climate Impact of Shale Gas Production
2.1 Sources of Greenhouse Gas Emissions
Estimates of the life-cycle climate impact, colloquially termed the 'carbon
footprint', of shale gas have identified multiple sources of emissions from the
exploration of a potential basin through to the delivery of natural gas to an
end-user (see Table 1). Direct emissions arise from the combustion of fossil
fuels for energy, intentional venting of methane for safety reasons, and un-
intentional releases, termed 'fugitive emissions'. Indirect emissions arise
