Environmental Engineering Reference
In-Depth Information
Arrow Energy is operating a reverse-osmosis plant of modest capacity in
the Surat, but this is still the exception rather than the rule. Under current
regulations, evaporation ponds are no longer permitted, but holding ponds
of similar design provide 'temporary' storage while operators await devel-
opment of cost-effective recycling methods. Regardless of treatment method,
by-products include salt in vast volumes and contaminated sludge in
quantities and kinds that depend on local conditions and extraction and
treatment practices. Until better solutions are discovered, most of the con-
taminated waste will be stored in brine ponds and salt pits on the gas
fields.
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3.2.2 The Atmosphere. CSG burns much cleaner than coal: typical carbon
emissions per unit of electricity generated from burning coal range from
43% to 87% greater than from CSG-LNG, which has the additional advan-
tage of not producing by-products such as sulfur, mercury, ash and par-
ticulates.
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If emissions were restricted to those from burning fuel,
wide-spread substitution of CSG for coal would bring big reductions in
Australia's carbon footprint. More comprehensive accounts suggest a more
nuanced picture - when the methane and carbon dioxide that will inevit-
ably escape from CSG wells and gas-fields, the energy used and emissions
released in extraction and processing, etc., are counted, the greenhouse
gas reduction benefit of CSG becomes more tenuous and specific to indi-
vidual CSG operations.
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The sheer magnitude of planned CSG operations in Australia generates
some very large estimates of potential atmospheric emissions. Approved
CSG and liquefied natural gas projects, including associated infrastructure,
could generate 39 Mt of carbon dioxide equivalent each year.
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Modeling
suggests that the CSG industry eventually could produce as much green-
house gas as all the cars on the road in Australia.
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The cognisant federal agency has recognised the policy and regulatory
challenge posed by large quantities of methane and carbon gases likely to be
released directly into the atmosphere from the gas fields and liquefaction
plants. Greenhouse gas data for CSG are being collected, including the pri-
mary sources of emissions and reasons for variations in leakage rates.
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Well
integrity is one component of a more comprehensive strategy to minimise
leakage of CSG into the air.
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3.2.3 Sub-surface Impacts. Sub-surface geology and hydrology can be dis-
turbed by CSG mining in two distinct ways: withdrawal of large quantities
of water, which is endemic to CSG operations; and fracking, which frac-
tures the coal seam and surrounding soil and rock layers to release the
gas, and is used in some CSG operations. Gas extraction and the lowering
of water tables create voids that may lead to land subsidence. Fracking
may lead to disturbance and irreparable damage to aquifers, migration of
methane and contaminants, and increased seismic activity.
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The potential
