Kate Mackenzie How good is natural gas, when lifecycle emissions are measured?

Is natural gas the easy way to reducing greenhouse gas (GHG) emissions that its supporters suggest?

While the fuel burns cleaner than coal, a very preliminary paper by Robert Howarth, a professor of ecology and environmental biology at Cornell University, says that natural gas might not be such a good option when total emissions are considered.

Howarth’s paper is made up of very rough estimates, which he acknowledges, but he already thinks that natural gas recovered from new hydrofracturing techniques appears to have higher emissions than combustion emissions alone would suggest.

Howarth writes that there appears to have so far been no study of the total GHG emissions from shale gas – or at least, none that are available to the public. And his view is fairly negative (emphasis his):

A first attempt at comparing the total emissions of greenhouse gas emissions from HVWWHFobtained 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. When the total emissions of greenhouse gases are considered, HVSWHF-obtained natural gas and coal from mountain-top removal probably have similar releases, and in fact the natural gas may be worse in terms of consequences on global warming.

Howarth says that transport of the gas, as with other fossil fuels that are becoming more difficult to retrieve, is one consideration, but the leakage of methane associated with shale gas is probably far more important. Methane is a far more potent greenhouse gas than carbon dioxide, although it also dissipates faster.

He uses some EPA and EIA figures on average methane emissions as a ratio of natural gas consumption – although we note that these figures may be different (although not necessarily lower) for shale gas. In other words, the paper seems to be looking generally at natural gas rather than shale gas in particular.

The gas industry was dismissive of the paper, as Reuters reports:

“We concur with the author’s own assessment that this two-page draft is ‘highly uncertain’, that the ‘numbers should be treated with caution’, and that there is ‘no rigorous estimate’ to support its conclusions,” Whitten said.

However it’s not entirely unbelievable.

Industry commentators say shale gas production is more like ‘manufacturing’ than traditional fossil fuel ‘producing’. Studies of lifecycle emissions of US corn ethanol, for example, are one of the key reasons it has fallen from favour as an environmental solution. Such studies are complex and can throw up contrarian results – for example, a well-publicised study that we wrote about last year found that in some – admittedly rather unusual -  circumstances, airplanes might be less GHG-intensive than trains.

Most of its findings supported prevailing ideas about which modes of transport are lower-emission, but the detail with which it looked at lifecycle emissions – building roads and producing steel to create transport infrastructure, for example – underlined how complex this process is (some argue that even then, the study wasn’t holistic enough).

But what’s most striking about Howarth’s paper is not the alarming implications of his very rough estimates, but his statement that rigorous estimates of the emissions from developing, processing, and transporting natural gas are not available – nor are such estimates available, he says, for coal-fired power.

It would be interesting to see just how detailed lifecycle studies of different energy sources would need to be in order to be fully comprehensive – and how different sources, from fossil fuels to renewables, would stack up. Perhaps none of them are what they seem.

Related links:

Hydro-fracing and earthquakes? Uh-oh… - FT Energy Source
EPA frac study: What the beginning may say about the end – Houston Chronicle