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Coal vs. Natural Gas: Why an Amazing New Study Doesn't Prove What It Says

Natural-gas junkies advertise the fuel as a magic elixir that will painlessly usher Americans from dirty coal and foreign oil to a cleaner alternative. Now a new paper from Cornell University not only debunks these clean energy claims, but makes an audacious declaration: natural gas produced from shale is dirtier than coal.

Now, natural gas is far from a wonder fuel. But the Cornell paper's big headline-generating conclusion -- and it pains me to say this -- simply can't be taken seriously, thanks to inadequate data and a serious methodological problem. Which is not to say it's wrong, just that we have no real way of knowing.

The paper by Cornell's Robert Howarth, a self-described biogeochemist and "ecosystem scientist," asks a question that should have been floated long before we pinned our hopes on natural gas as a clean bridge fuel. Namely, that is, what sort of greenhouse emissions does shale gas produce when you include the methane (a powerful greenhouse gas) leaked during production and transport? Put more simply: Is shale gas anywhere near as clean as we've been led to believe?

Here's what Howarth study discovered:

  • Higher emissions from shale gas are released during hydraulic fracturing, a process in which a solution of water, sand and chemicals is blasted into the earth to break up shale formations rock and release the trapped natural gas.
  • Between 3.6 percent and 7.9 percent of the methane from shale-gas production escape to the atmosphere in venting and leaks over the lifetime of a well;
  • These methane emissions are at least 30 percent more than and perhaps twice as great as those from conventional gas;
  • Compared to coal, the footprint of shale gas is at least 20 percent greater and perhaps more than twice as great on the 20-year horizon and is comparable when looked at over 100 years.
The carbon footprint of shale gas could be worse than coal. It could be better. We don't know because the data used on Howarth's report is woefully incomplete. It's not that Howarth purposefully avoided certain data. There just isn't a lot out there, a problem he readily admitted in an interview with MIT's Technology Review.
The reason is that all of the data come from industry sources ... and industry has not been very forthcoming. Were the industry to comply, then more and better documented data could become available, and one could improve on our study.
Unfortunately, the problems don't end there. Howarth's study ignores what happens when gas and coal is converted into electricity. Instead, the study is solely focused on the emissions involved in production of each fuel source. This is flawed because modern gas power-generation technology is more efficient than that for coal, meaning that gas yields more electricity per unit of energy content. As Michael Levi from the Council on Foreign Relations notes:
The per kWh (kilowatt per hour) comparison is the correct one, but Howarth doesn't do it. This is an unforgivable methodological flaw; correcting for it strongly tilts Howarth's calculations back toward gas, even if you accept everything else he says.
Natural gas justifiably has its fair share of detractors. Hydraulic fracturing is hardly innocuous. Complaints of groundwater contamination abound and people who live near shale gas operations, like the folks in Dimock, Penn., have reported sick animals and their own health problems.

And while this study asks an important question, we're not a whole helluva a lot closer to the answer.

Photo from Flickr user stevendepolo, CC 2.0