The Chevy Volt gives the phrase “pay to pollute” a whole new meaning.

General Motors pitches the pricey Chevy Volt as a means of reducing carbon emissions. The Volt web page states:

Electricity – a more sensible primary fuel
Put simply, electricity is a cleaner source of power. And as technology improves in the generation of electricity, we will continue to see reduced carbon outputs. Advancements in electricity production along with reduction in emissions from electric-powered driving could help make our world a cleaner place.

So does the Chevy Volt’s battery actually reduce carbon emissions? Here’s our analysis.

According to the EPA the 4-seat Volt is capable of driving 35 miles on its 16 kilowatt hours (kWh) of stored electric charge. The Volt’s gas-only fuel economy rating is 37 mpg.

Since two oxygen atoms from the atmosphere combine with each carbon atom when gasoline is burned, a gallon of gas produces about 19.6 lbs. of carbon dioxide (CO2) when burned. So when operating on gasoline, the Volt produces 0.53 lbs. of CO2 per mile (19.6 lbs. of CO2 per gallon divided by 37 miles per gallon).

Since we can’t quantify accurately just how much transmission loss there is between electricity generation and charging points, we’ll assume an impossible 100 percent efficiency at the charger to work out the CO2 emissions for the Volt’s 16 kWh stored charge.

In 2007, national “average” CO2 emissions were 2.16 lbs per kWh from coal-fired generation and 1.01 lbs per kW for gas-fired generation. according to Power Systems Analysis. Given that 44.46 percent of electricity in the U.S. is coal-fired and 23.31 percent is gas-fired, on a national basis, then, the mean emission of CO2 per kWh is 1.2 lbs/kWh. (2.16 lbs/kWh x 0.4446 = 0.96 lbs/kWh from coal, plus 1.01 lbs/kWh x 0.2331 = 0.24 lbs/kWh from gas).

The Volt’s “emissions mileage” from its stored charge is then 16 kWh x 1.2 lbs/kWh divided by 35 MPG = 0.55 lb CO2/mile.

So on an “average” basis, the Volt emits more CO2 from battery use than from gasoline use (0.55 lbs/mile vs. 0.53 lbs/mile).

Maybe you don’t think that’s a big difference, but the difference becomes more pronounced when the Volt is charged in states that rely more on coal-fired electricity.

In West Virginia where coal fires 96 percent of the state’s power, the Volt’s per mile CO2 emissions reach 0.95 lbs per mile. In Ohio, Volts emit about 0.84 lbs of CO2 per mile — much higher than the gasoline-powered rate of 0.53 lbs. per mile.

In fact, coal is burned to produce 44 percent or more of the electricity in 26  states (AR, CO, DE, GA, IA, IL, IN, KS, KY, MD, MI, MN, MO, MT, NC, ND, NE, NM, OH, OK, PA, TN, UT, WI, WV, WY).  So, on average, Volts charged in those states will emit more CO2  from battery use than gasoline use.

Last November, the Nature Conservancy proclaimed:

CHEVY VOLT COULD DECELERATE AMERICA’S CARBON FOOTPRINT

Too bad it didn’t check under the hood.

 

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