Leakage of methane from fracking boosts shale gas global warming impact; National Academy review is warranted
Comparison of greenhouse gas emissions from shale gas (with low and high estimates of fugitive methane emissions) [with other energy sources]. Top panel (a) is for a 20-year time horizon, and bottom panel (b) is for a 100-year time horizon. Estimates include direct emissions of CO2 during combustion (blue bars), indirect emissions of CO2 necessary to develop and use the energy source (red bars), and fugitive emissions of methane, converted to equivalent value of CO2 as described in the text (pink bars).
I was a (relatively) early booster of shale gas as a potential game changer for greenhouse gas mitigation [see Game Changer, Part 1: There appears to be a lot more natural gas than previously thought (6/10) and Part 2: "Unconventional gas makes the 2020 climate targets so damn easy and cheap to meet" (7/10)].
But there were always lurking concerns about the impact of methane leakage in from the unconventional gas extraction process known as hydraulic fracturing, since methane is a considerably more potent greenhouse gas (GHG) than carbon dioxide. Now three Cornell University professors have published a major analysis in Climatic Change, “Methane and the Greenhouse-Gas Footprint of Natural Gas from Shale Formations,” that seeks to quantify the impact of the leakage from the best available data.
They find a leakage rate large enough to seriously undercut gas’s GHG benefit even in high-efficiency combined cycle plants — and one that is all-but-fatal to any GHG benefit from using natural gas as a transport fuel. That conclusions is doubly true if one looks at the GHG impact over a few decades, rather than a century.
This is a potentially game-unchanging conclusion for one of the seminal energy policy choices of this decade — how hard to push shale gas here and around the world. And yet, as the lead author Cornell Prof. Robert Howarth explained to me in an interview, it is based upon very limited data. And that’s in part because the industry has fought efforts to get more data. Prof. Howarth agreed with my suggestion that this would be a very ripe topic for the National Academy of Sciences to review.
The study’s basic conclusion is that shale gas production is a bigger, longer and more complicated enterprise than conventional drilling, and that methane leakage is much higher during production and processing: