The key is where the source of the electricity all-electric cars. If it comes from coal, the electric cars produce 3.6 times more soot and smog deaths than gas, because of the pollution made in generating the electricity, according to the study that is published in PNAS. They also are significantly worse at heat-trapping carbon dioxide that worsens global warming, it found.
The study examines environmental costs for cars’ entire lifecycle, including where power comes from and the environmental effects of building batteries.
“Unfortunately, when a wire is connected to an electric vehicle at one end and a coal-fired power plant at the other end, the environmental consequences are worse than driving a normal gasoline-powered car,” said Ken Caldeira of the Carnegie Institution for Science, who wasn’t part of the study but praised it.
But if the power supply comes from natural gas, the all-electric car produces half as many air pollution health problems as gas-powered cars do. And if the power comes from wind, water or wave energy, it produces about one-quarter of the air pollution deaths.
Hybrids and diesel engines are cleaner than gas, causing fewer air pollution deaths and spewing less heat-trapping gas.
But ethanol isn’t, with 80 percent more air pollution mortality, according to the study.
“If we’re using ethanol for environmental benefits, for air quality and climate change, we’re going down the wrong path,” Hill said.