Exploring Hydrocarbon Depletion
Page added on February 28, 2012
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.
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,
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.”