Coal seam gas is no solution to climate change
The coal seam gas industry is fond of positioning itself as a solution to climate change. They have managed to convince the Queensland Government of this - Queensland has set a target of 18% of domestic energy to be provided by gas by 2020.
But much like the earlier claims of the fossil fuel industry that so-called 'clean coal' would solve the climate crisis, the arguments about the climate change virtues of coal-seam gas do not stand up to scrutiny. In fact, preliminary research suggests that energy from coal seam gas may be slightly more environmentally damaging than burning coal.
The work of Professor Robert W. Howarth - Professor of Ecology and Environmental Biology at the Cornell University in the US - provides a more accurate depiction of the contribution that coal seam gas makes to greenhouse gas emissions.
Professor Howarth writes:
Natural gas is being widely advertised and promoted as a clean burning fuel that produces less greenhouse gas emissions than coal when burned. While it is true that less carbon dioxide is emitted from burning natural gas than from burning coal per unit of energy generated, the combustion emissions are only part of story and the comparison is quite misleading.
A complete consideration of all emissions from using natural gas seems likely to make natural gas far less attractive than other fossil fuels in terms of the consequences for global warming.
Professor Howarth acknowledges that the analysis used is preliminary, but there is currently no better publicly available or peer-reviewed assessment for a basis of comparison.
Howarth's position is this: while acknowledging that the coal seam methane fuel burns cleaner than coal, it does not withstand scrutiny as a 'cleaner' energy source when total emissions are considered.
Considering the release during combustion alone, greenhouse gas emissions from burning natural gas average 13.7 g C of CO2 per million joules of energy compared to 18.6 for gasoline, 18.9 for diesel fuel, and 24.0 for bituminous coal.
However, additional emissions of greenhouse gas occur during the development, processing, and transport of natural gas (due to the use of fossil fuels to build pipelines, truck water, drill wells, make the compounds used in drilling and fracturing, and treat wastes, and the necessary land-clearing to establish wells and infrastructure).
A reasonable estimate of this appears likely to equal at least one third of those released during combustion (4.5 g C of CO2 per million joules of energy). By comparison, indirect the greenhouse gas emissions from diesel fuel or petrol is in the range of 8%, or 1.5 g C of CO2 per million joules of energy.
Methane Leakage from Coal Seam Gas
A far more important consideration, however, is the leakage of methane through the production, transport, processing and use of coal seam gas. Methane is by the far the major component of natural gas, and it is a powerful greenhouse gas: 72-times more powerful than is CO2 per molecule in the atmosphere.
Since methane is such a powerful greenhouse gas, even small leakages of natural gas to the atmosphere have very large consequences on global warming.
The best available figures that Howarth could find suggest a leakage rate from the oil and gas industry of an amount of methane equal to 1.5% of the natural gas consumed (based on leakage data reported in Inventory of U.S. Greenhouse Gas Emissions and Sinks from 2006, and the US Department of Energy's own consumption figures). This page from Sourcewatch provides a figure of 1.4%, with a .5% margin of error.
If we assume a 1.5% leakage rate, this would have a greenhouse gas warming potential equal to 14.8 g C of CO2 per million joules of energy.
Total greenhouse gas emissions from coal seam gas is therefor equivalent to 33 g C of CO2 per million joules of energy. For diesel fuel or gasoline, the total greenhouse gas emissions are equivalent to approximately 20.3 g C of CO2 per million joules of energy.
Is coal seam gas worse than coal?
Howarth points out that direct comparisons with coal is difficult, as the total emissions from mining and transport are not well known, and almost never reported. If we assume that they are roughly equivalent to one third of the emissions from direct combustion (as was done for coal seam gas), then the total emissions from coal would be equal to 31.9 g C of CO2 per million joules of energy, or very slightly less than the estimate for coal seam gas.
Professor Howarth's conclusions are straightforward:
Far better would be to rapidly move towards an economy based on renewable fuels. Recent studies indicate the U.S. and the world could rely 100% on such green energy sources within 20 years if we dedicate ourselves to that course.
For more information, check out:
- Natural gas transmission leakage rates, Sourcewatch
- Fracking is not a clean alternative
- How good is natural gas, when lifecycle emissions are measured?
- Gas can be dirtier than coal but Government & NGOs falsely assert that gas is clean energy by Dr Gideon Polya
- Natural Gas: Transition fuel or Greenhouse Menace
- Gasland Ain't So Green After All
Download Professor Howarth's "Preliminary Assessment of the Greenhouse Gas Emissions from Natural Gas Obtained by Hydraulic Fracturing" below.