Dirty Power, Clean Cars: Even From Coal, EVs are Cleaner

Jim Motavalli

Jim Motavalli | Jun 04, 2010

Few American grids are 100 percent coal-fired. (photo courtesy EPRI)One of the most common questions fielded at Car Talk Plaza comes from a guy - and it's usually a guy - who thinks he knows the answer already.

"These electric cars," he says. "I don't get it. Aren't you just transferring the pollution from the tailpipe to the smokestack because the electricity comes from coal plants? That's why I'm ignoring this whole plug-in thing and plan to keep my Hummer."

It's a fair question, even if they put it in the form of a statement. But rest easy, Mr. Questioner, and you may have to sell off that Hummer after all. Charging battery electrics from a grid that is 100 percent coal-fired (and we have few that are that coal-dependent) still offers a 30 to 40 percent climate emissions improvement over the average internal-combustion car.

Let's look at the big picture here. The American electricity grid in 2009 was 44.6 percent coal, 23.3 percent natural gas, 20.2 percent nuclear, 6.9 percent hydro and 3.6 other renewables like wind and solar. I thought there were still a lot of fuel oil plants, but not so: fuel oil is less than one percent of the mix, about on par with cool things like landfill gas recovery and methane digesters (from both ends of the cow). Those digesters (they love 'em in Vermont) are more important than you probably realize, because the UN has concluded that livestock produce 18 percent of global warming emissions (more than transportation).

King Coal is a big polluter, producing (according to the National Mining Association) between 39 and 41 percent of global climate emissions. China, which is building coal plants at a furious rate, is poised to make that international figure even worse. But the electric car charging thing is not straightforward, because few people (even in the coal-dependent Midwest) charge from a 100 percent coal grid.

"Clean coal" will seem like an oxymoron if you've ever - as I have -- visited West Virginia and seen, from the air and the ground, the blasted moonscapes that constitutes mountaintop removal mining. I mean, they burn off intact hardwood forests so they can scar the earth with huge shovels, fill streams with polluted waste, then carry off the coal in trucks so big they have to be assembled on site. It's hard to see how you get to "clean coal" from that starting point.

There's surprisingly little hard data on the coal/cars equation. A study conducted by the Electric Power Research Institute (EPRI) concluded that plug-in hybrid cars (which use a gas engine after the plug-in battery power is exhausted) are cleaner in each of nine scenarios, involving both low-carbon and high-carbon grids. "Annual and cumulative greenhouse gas emissions are reduced significantly across each of the nine scenario combinations," they said, in the dry language of such things.

The Nissan Leaf has the Prius' climate impact when charged from coal. (Jim Motavalli photo)

But that's plug-in hybrids. What about battery cars, which are wholly tied to the grid? I asked Eladio Knipping, an EPRI senior technical manager for the environment, for some quick "back of the envelope" calculations and he came up with the 30 to 40 percent cleaner figure, which puts your battery car on about the same plane as a hybrid. Which isn't bad.

It also makes battery cars look worse than they actually will be. "We have an evolving grid," Knipping said. "In the Midwest it's primarily coal, but there are inputs from nuclear and it's transitioning to cleaner coal technologies, natural gas and renewables. Even in areas that are primarily coal, there is a diversity of sources."

So using an EV in, say, Gary, Indiana is like owning a Prius? "Yes, like a Prius," Knipping said. If your local power plant is natural gas-fired (and almost a quarter are), you're in even better shape - a 60 to 70 percent improvement over the gas car, and only about half the emissions of a hybrid.

Don't take his word for it. I got essentially the same answer from everyone I talked to, even some who probably disagree on almost everything else. According to Luke Popvich, a spokesman for the National Mining Association, "It's not a one-to-one exchange, that's for sure. You're never going to get the same mix of pollutants out of a smokestack as you do from a tailpipe. In the last 20 to 30 years we've cleaned up a lot of our smokestack emissions."

Of course, he would say that, but his essential point - that power plants are going to keep getting cleaner - is an important one.

Charles Griffith, the Clean Car Campaign director at The Ecology Center in Michigan, agreed with the "like a hybrid car" scenario, and also that the grid is getting steadily better. "The basic point is that it's not worse to have electric vehicles on a grid that is primarily coal-based," he said. "As we put more renewables into the grid, the profile for EVs will only get better over time. We're moving in the right direction."

The Natural Resources Defense Council has studied the exhaust vs. smokestack question with EPRI and Deron Lovaas, the transportation policy director, is also a member of the choir. "The benefits become truly immense as the grid gets cleaner," he said. "If you look at just coal the benefits are modest, but the minute you begin cleaning it up the benefits accumulate. There's no comparison."

I guess that settles it, unless I can find anyone with an argument backed up by actual facts. This is a bipartisan conclusion. So if you're one of those guys calling Car Talk about this, please bring us your irrefutable data.

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