Environmental Benefits of Plug-ins Called Into Question

By · July 30, 2010

With roughly $6 billion in incentives for plug-in vehicles working its way through the United States Congress as part of the trimmed-down energy bill, the question of how much cleaner EV's actually are, has re-emerged.

The Great 'Zero-Emissions' Debate

BMW ad

Recently, BMW was forced to pull an advertising campaign from British media markets after the Advertising Standards Authority decided that the ads were misleading in their description of the Concept ActiveE as a “zero-emissions” vehicle. The campaign's tagline, "100 percent joy, zero percent emissions," was found by regulators to misrepresent the lifecycle carbon footprint of the car, because much of the electricity used to power plug-in cars currently comes from burning coal.

This isn't the first time that a carmaker has run afoul with the ASA for claiming to sell a zero-emissions product. Renault has twice been banned by the watchdog for the a similar offense—with their second ad having been amended to claim only a 90 percent reduction in emissions. Even though that statement was found to be true in the company's native France, the French electricity generation mix is cleaner than Britain's, meaning that emissions savings over diesel would be lower in the U.K.

So Just How Much Better Are Plug-ins?

The disagreement over how to classify emissions from EVs is an old one. Plug-in fans see the glass half-full: Since the vehicles themselves produce no emissions and are theoretically capable of running purely on renewable energy, why should they be blamed for society's refusal to move off of dirty, coal-powered electricity? Skeptics say that using 'zero-emissions' terminology is fundamentally misleading, and serves no purpose but to distort the environmental benefits of electric cars.

Both sides have a point. If manufacturers and supporters of electric cars are going to use lifecycle emissions in their arguments against ethanol, they should at least be willing to admit that under most current conditions—and absent an expensive and well-designed renewable energy setup—charging an EV will result in some level of carbon emissions.

Solar Parking Lot height="269" />

The debate over just how big those emissions are is even more contentious and difficult to resolve than any semantic argument over advertising slogans. The U.S. Department of Energy has estimated total carbon savings from electric vehicles to be about 50 percent compared to ICE's. That calculation uses the current combined fuel economy average for the United States (about 22 mpg,) but doesn't take into account the effect that hybrids and more efficient gasoline and clean diesel cars will soon have as more and more are rolled out to meet future CAFE standards.

A Ford-funded study out of M.I.T. found that when vehicles are powered by electricity derived from nuclear and renewable energy, they provide vast carbon savings over gasoline-fueled autos. But if that electricity comes from the currently available mix of coal and other emissions-heavy energy sources, the study says that emissions are actually higher.

The M.I.T. study has come under heavy criticism since its release, and is a bit of an outlier compared to the other limited research that has been presented on the subject. Nevertheless, representatives from the Auto Alliance and advocates for competing fuels like ethanol have used the findings to argue that it's far too soon to "pick winners" in the clean fuels race.

NRDC Says Already-Significant Carbon Savings Will Only Get Bigger

According to a report from the National Resources Defense Council and the Electric Power Research Institute, plug-in vehicles that rely primarily on energy from coal provide a significant emissions drop-off over conventional cars. The 18-month study looked at nine different scenarios involving different energy mixes and rates of electric vehicle adoption, finding that each scenario represented an improvement over petroleum based fuels.

Of course, the biggest immediate carbon pay-off for EVs will come in places like the Pacific Northwest, where renewables already make up a significant portion of the energy mix. As other regions blend in more and more renewables, they should see increased benefits as well. Advancements in the power grid should also pay big dividends, and overnight vehicle charging saves energy by helping to even-out demand for energy between day and nighttime consumption.

No Easy Answers

Coal Plant

Though the environmental benefits of electric vehicles currently vary depending upon region and usage, nearly all of the available research on the subject indicates that they represent the cleanest available transportation technology that doesn't require pedaling. But the discussion does underline an important issue that will need to be addressed as the world works to get off of fossil fuels and reduce greenhouse gas emissions. If the electrical power we use doesn't get cleaner—and the methods we use to distribute it don't get more efficient—replacing gasoline with electricity will only make a modest dent in global emissions.

Even as the world's leading car culture, the United States is estimated to derive less than 30 percent of its overall carbon emissions from transportation. In order to maximize the positive impact that the electric cars of tomorrow will have on the environment, a lot of work has to be done to clean up the infrastructure that they plug into.

New to EVs? Start here

  1. Seven Things To Know About Buying a Plug-In Car
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  3. Buying Your First Home EV Charger
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