The Facts About Fugitive Methane

In The Facts About Fugitive Methane, published by the Centre for Policy Studies on Monday 26 October 2015, Richard Muller, Professor of Physics at the University of California, reveals that previous estimates of methane leakage in shale gas production have been seriously over-estimated.

Methane, the main component of natural gas, has a high greenhouse potential, and opponents of shale gas production argue that even if one or two percent of the gas leaks, the advantage of natural gas over coal would be negated.

Elizabeth and Richard Muller’s new research now shows this estimate is incorrect:

  • over a 100 year time span, an implausible 12% of the produced natural gas used today would have to leak in order to negate an advantage over coal.
  • The best current estimates for the average leakage across the whole supply chain are below 3%; even at 3% leakage natural gas would produce less than half the warming of coal averaged over the 100 years following emission.
  • Half this 100 year average comes from the first 10 years; three-quarters from the first 20 years; the warming at 100 years is almost entirely from the (relatively low) CO2 produced from burned methane, not from the leaked methane itself.
  • An additional reason to produce electric power from natural gas is that the legacy advantage of natural gas is enormous; after 100 years, only 0.03% of leaked gas remains in the atmosphere, compared to 36% for remnant carbon dioxide. 

Elizabeth and Richard Muller comment:

“The concerns over fugitive methane is based on the following true but easily misinterpreted facts about methane:

  • Methane, when released to the atmosphere, has Global Warming Potential (GWP) of 86 over a 20 year period. This means that methane is 86 times more potent as a greenhouse gas than CO2, pound for pound, averaged over the 20 years following the emission.
  • Methane leakage has been observed in range 6.2% to 11.7% based on measurements taken of the air above some drilling areas. 

But the maths described above is incorrect, and as a result the conclusions are incorrect:

  • When comparing coal to methane for equal electric power, the 20-year global warming potential of methane compared to carbon dioxide is 11, not 86.
  • Legacy warming from fugitive methane is minuscule compared to that of carbon dioxide.
  • Average leakage today is far below dangerous levels.”

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