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Natural Gas Our New Savior? Not So Fast . . .

By Mike Lemonick

Remember how ethanol was going to save us? It was the perfect solution to not one, but two different problems. The first was energy security: since it’s a type of alcohol distilled from home-grown corn, ethanol would replace the gasoline made from oil imported from Bad People in places like Iran. The second was climate change. Ethanol emits heat-trapping CO2 like gasoline does, but the corn sucks in CO2 while it’s growing, so it’s mostly a wash.

That was the sales pitch, anyway, and for a while, lots of people bought it. The Federal government subsidized ethanol production, and an EPA regulation requiring the use of renewable fuels boosted ethanol’s stock still further. Then scientists began calculating the actual climate impact of corn ethanol, and discovered it wasn’t much better than gas — and might actually be worse.

Engineers maneuver a motor and drill bit on a natural gas drilling platform in Fort Worth, Texas. Credit: Robery Nickelsberg/Getty Images. 

You’d think we’d have learned something from this cautionary tale. Evidently not, though: we have a new savior called natural gas. It’s the perfect solution, because it’s plentiful and home-drilled, (thank you, fracking), and it emits only half the CO2 that coal does. If we could replace our current coal-fired power plants with gas plants, it wouldn’t solve the problem of climate change, but it would buy us time to shift over to true renewables like wind and solar.

You know what’s coming next, right? I’m afraid so. Just as happened with ethanol, scientists and engineers are starting to take a more serious look at natural gas, and the story turns out to be more complicated and less ideal than it originally seemed. First, the good news: natural gas emits drastically less soot and other particulates than coal. Soot is bad for the lungs, and it contributes to global warming all by itself, so cutting back on it would clearly be a good thing.

And if you could magically flip a switch and turn all existing coal plants in to gas plants, you would indeed cut CO2 emissions significantly.

But there is no magic switch, and therein, according to a recent analysis published in Environmental Research Letters, lies a problem. “The most surprising thing we found,” lead author Nathan Myhrvold told me recently, “is that unless you switch to a form of energy that cuts emissions really drastically” — and he isn’t talking about any piddling 50%, either — “you basically don’t get any real effect.” (If you recognize Myhrvold’s name, it might be because he used to be a top executive at Microsoft, or it might be from his exploits as a barbecue champion or as a donor to the Search for Extraterrestrial Intelligence — but he also holds a degree in theoretical physics from Princeton.)

His point, and that of his co-author Ken Caldeira, a climate scientist with the Carnegie Institution of Washington, is that before a new natural-gas power plant can go into operation it’s already made the climate problem worse. It takes energy to build the plant, most of which comes from fossil fuels. The process of drilling for natural gas and piping it to the plant, moreover is prone to leakage — and methane, the main component of natural gas, is itself a powerful greenouse gas . And while the construction is going on, says the Myhrvold-Calderia study, you’re still emitting CO2 from those old, dirty coal plants, which can’t be switched off until the new gas plants are ready to go.

The bottom line that emerges from this “life-cycle analysis,” or LCA, said Myhrvold, is that by the time we could switch from coal to gas, there would already be so much more CO2 and methane in the atmosphere that we’d be much deeper in the hole. “It’s like living on a credit card,” he said. “It’s easy to get into a situation where it will take years and years to pay back.”

In fact, he argues, because CO2 stays in the atmosphere for so long once it’s up there, a switch to natural gas would have zero effect on global temperatures by the year 2100. “If you take 40 years to switch over entirely to natural gas,” he said,

“you won’t see any substantial decrease in global temperatures for up to 250 years. There’s almost no climate value in doing it.” 

A switch to renewables (true renewables, that is, not corn-based ethanol) would also incur a carbon debt: it takes energy to manufacture solar panels and wind turbines too, after all. If we made that switch, according to Myhrvold and Calderia’s calculations, you wouldn’t see a change in temperatures for decades either. But by 2100, the decrease would start to kick in (he explicitly rejects the idea of new hydropower dams, by the way, whose energy is renewable but which are, he said, “much worse than coal for the first hundred years”: the trees and other vegetation that rot beneath backed-up water release lots of methane).

“You can quibble about LCA numbers,” he said, “and a number of people have emailed us criticizing some of our assumptions. But the main idea is that if you’re transitioning to something that’s only twice as good as coal, it’s not really worth your time. If you’re doing something that’s better by a factor of 10, it’s reasonable.”

« Commentary


By dan in illinois
on February 28th, 2012

Let me see if I have this straight.  Natural gas would make us much less dependent on foreign oil and it would reduce our CO2 emissions, but “only by 50%”, which the “experts” judge to be not significant.  Of course, unlike wind and solar, which not only would have plenty of technical issues but have to be heavily subsidized by the government, natural gas would occur with no government cost.  Weighing all this, the conclusion is that natural gas is not a good part of the solution to the energy problem?

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By David Snällfot (Malmö)
on February 28th, 2012

Fossil fuel gas or “natural” gas is prone to fugitive methane emissions or methane leakage, the preferred nomenclature used in this article.
Now these leaks are usually in the order of a few percent, ranging from about 1.7 to 6% for conventional gas and increasing to 3.6 to 7.9% for that more unconventional sort, shale gas.
Measuring methane leaks from the point of extraction, processing, pipelining to the combustion chamber is not exactly common practice (although it certainly should be) and hence the numbers above are probably conservative (taken from Howarth et al: http://www.springerlink.com/content/e384226wr4160653/ )
So, does it matter? Well, yes it does. Methane is an important greenhouse gas with a large Global Warming Potential, usually cited to be 25 times that of CO2 in a 100 year period, but more recent studies points to a significantly larger potential (when its effect on aerosols is at least attempted to be included in the calculations) pushing up the number to 33 times that of CO2. (Taken from Shindell et al: http://www.sciencemag.org/content/326/5953/716 )
What all this means is that the leaks above, small as they might seem, are in fact large enough to cancel out any theoretical climate friendliness of fossil fuel gas, since a mere 2-3% leak of methane from anywhere along the chain from extraction to combustion, effectively renders gas on par with coal in terms of emissions.

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By Mike MacCracken (Bethesda, MD 20814)
on February 28th, 2012

The discussion here needs to be carefully stated—we can reduce the rate of warming if we go after the right things in the right way. Reducing methane emissions can help in the near term, and there are lots of inexpensive alternatives (fix leaky pipes, capture methane from sewage plants and disposal sites, adjust the feeding of ruminant animals, fileter the methane out of coal mine air, and many more that have other side benefits), so let’s not confuse the article’s finding the switching coal to methane for utilities isn’t the perfect answer.

Same goes for black carbon—there are lots of cost-effective, multi-benefit technologies, and quite a number can have a big effect. For example,  reduce soot from inefficient wood burning stoves,  two-stroke engines, unfiltered exhaust from power plants, and more.

And for reducing emissions from coal-fired power plants, improve efficiency, replace with solar and wind, don’t build any more, use the heat so net efficiency goes from about 35% (in US)  to close to 65% (in Denmark), etc. No way does this article say there are not lots of things to be doing.

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By John Ward (Gainesville/FL/32605)
on August 21st, 2012

I’m surprised that your article failed to mention the most recent study of natural gas as a bridge fuel, http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/cathles/Natural Gas/Assessing the greenhouse impact of natural gas FINAL UNFORMTTED.pdf
The author, L.M. Cathles, argues that “substituting natural gas for coal and oil is a significant way to reduce greenhouse forcing, regardless of how long the substitution takes.”
Clearly the rate of methane emissions is a consideration in assessing the benefit of natural gas as a bridge fuel, as is the creation of a vast infrastructure to handle natural gas extraction, transporting, and use, along with a lobby that would make it difficult to end the use of natural gas once established and that would obstruct the further lowering of greenhouse gas emissions essential to preserve some semblance of the world we now enjoy. But I’m not qualified to evaluate Cathles’ model for tracking use of natural gas under various assumptions. As far as I can tell, the jury is still out.

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