THE GHGS FROM NATURAL GAS

Preliminary Assessment of the Greenhouse Gas Emissions from Natural Gas obtained by Hydraulic Fracturing
Robert W. Howarth, 17 March 2010 (Cornell University)

"Natural gas is being widely advertised and promoted as a clean burning fuel that produces less greenhouse gas emissions [GhGs] 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…

"There is an urgent need for a comprehensive assessment of the full range of emission of greenhouse gases from using natural gas obtained by high-volume, slick water hydraulic fracturing (HVSWHF, or “hydrofracking”)…Some information suggests that one or more assessments may have been conducted by industry groups, but if so these are available only to industry…If such assessments exist, they have not been subjected to external, unbiased scientific review."

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"A first attempt at comparing the total emissions of greenhouse gas emissions from HVWWHF obtained natural gas suggests that they are 2.4-fold greater than are the emissions just from the combustion of the natural gas. This estimate is highly uncertain, but is likely conservative, with true emissions being even greater…[Based on total GhGs] HVSWHF-obtained natural gas and coal from mountain-top removal probably have similar releases, and in fact the natural gas may be worse…[GhGs] from HVSWHF-obtained natural gas are estimated to be 60% more than for diesel fuel and gasoline. These numbers should be treated with caution. Nonetheless, until better estimates are generated and rigorously reviewed, society should be wary of claims that natural gas is a [more] desirable fuel…Far better would be to rapidly move towards an economy based on renewable fuels…[A Path to Sustainable Energy by 2030> and other] 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…

"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…Additional emissions…occur during the development, processing, and transport of natural gas…"

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"…[T]he greenhouse gas emissions obtaining, processing, and transporting diesel fuel and gasoline are in the range of 8% …or perhaps 1.5 g C of CO2 per million joules of energy…[A]s fossil fuel energy resources become more diffuse and difficult to obtain (as is gas in the Marcellus Shale), the energy needed to extract them and the greenhouse gas emissions associated with this effort go up substantially.

"The leakage of methane gas during production, transport, processing, and use of natural gas is probably a far more important consideration. 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…The most recent data…suggest a leakage rate from the oil and gas industry of an amount of methane equal to 1.5% of the natural gas consumed…Total greenhouse gas emissions from natural gas from hydraulic fracturing may, therefore, be equivalent to 33 g C of CO2 per million joules of energy…[T]otal emissions from coal [could] be equivalent to 31.9 g C of CO2 per million joules of energy, or very slightly less than the estimate for the natural gas."