Plug-in cars could actually increase air pollution
— -- The expected introduction of plug-in hybrid electric vehicles could cut U.S. gasoline use but could increase deadly air pollution in some areas, two reports say.
That's because a plug-in's lower tailpipe emissions may be offset by smokestack emissions from the utility generating plants supplying electricity to recharge the big batteries that allow plug-ins to run up to 40 miles without kicking on their gasoline engines. Plug-ins, called PHEVs, are partly powered, in effect, by the fuel used to generate the electricity.
About 49% of U.S. electricity is generated using coal, so in some regions a plug-in running on its batteries is nearly the equivalent of a coal-burning vehicle. The trade-off is one that even plug-in backers acknowledge. It could undercut the appeal of vehicles that appear capable of using no gasoline in town and hitting 50 to 100 mpg overall fuel economy.
If large numbers of plug-in hybrids were being recharged with power from the least-sophisticated coal plants, "There is a possibility for significant increases of soot and mercury," says a report by environmental advocacy group Natural Resources Defense Council. Soot particles can make it hard to breathe, especially for asthmatics. Mercury is toxic.
"Plug-in hybrids are perhaps not good for all areas," says Howard Learner, executive director of the Environmental Law & Policy Center, a Chicago-based advocacy group. In "states that are heavily coal, that equation doesn't work out very well for the environment."
After PHEVs drain their stored energy, they operate like conventional hybrids, triggering their gasoline engines to help drive the wheels and recharge the batteries. Conventionals can't be plugged in; their batteries are recharged only while driving.
The longer a plug-in is designed to operate on just the batteries, the less gasoline it uses, but the more electricity it needs to recharge the larger batteries.
Thus, the better the PHEV — that is, the longer it goes just on its batteries — the greater the charge required and the more the pollution that might result from an electric utility's power generation.
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