An analysis done by Biofuels Digest has come to the very surprising conclusion that an electric car will produce 30% more carbon dioxide emissions over its lifetime than a car powered by E85 corn ethanol. Not only that, the study also found that the same electric car will produce 21% more carbon dioxide than even a gasoline powered car.
These claims assume that 100% of the electricity for the EV comes from coal-fired power plants and that a comparable car would get 35 mpg—both of which seem like unrealistic assumptions. So I dug around the internet today to try and come up with more realistic numbers.
Problems With the Study
Biofuels Digest deserves credit for thinking hard about the big picture, but, after all of my research and thinking today, I feel they’ve left out some details that make the study difficult to swallow. Namely the following:
- The future of electric cars is not based on the Tesla Roadster, it is based on sedans that seat 4-5 people. When comparing cars you need to compare apples to apples. Comparing a hypothetical 35 mpg car to an electric car doesn’t seem logical. That 35 mpg car would be a Toyota Yaris or Chevy Aveo. If you want to compare an electric car to a fuel-powered car, compare that EV to a 27 mpg 4 door gasoline sedan (and I’m being generous on mpg there). CAFE standards are fleet-wide standards. It’s not that every car in the US will get 35 mpg when CAFE takes full effect.
- There is nowhere in the country that you can obtain 100% of your electricity from coal (even if you are a crazy, twisted soul and really wanted to). In the US, coal accounts for roughly 51% of all electricity generation. In some areas, such as where I live in the Pacific Northwest, hydropower accounts for 80% of electricity generation. Coal-fired power plants are far and away the largest CO2 emitter in the US. In fact, when just looking at electricity generation in 2007, coal accounted for about 81% of all CO2 emitted by power plants.
- Total CO2 emissions from all kinds of US electricity generation in 2007 was 2,433 teragrams and the total electricity generation was 3,828 billion kWh. When you do the resulting calculations and conversions you find that, on average, the US is emitting 1.4 pounds of CO2 for every kWh of electricity generated—much better than the 2.09 pounds CO2/kWh cited in BD’s study.
- On average, regardless of size or type, electric cars go about 4 miles per kWh (mpkWh) of electricity. BD’s study used a value of 3.12 mpkWh because that is what Tesla used to get some time ago. Newer electric cars will get at least 4 mpkWh, and that number is getting better all the time.
Electric Cars Actually Produce 40% Fewer Emissions Than E85 Powered Cars
If you download Biofuels Digest’s results spreadsheet and plop in some corrected numbers accounting for the above criticisms, you find that electric cars produce 40% fewer CO2 emissions than E85 powered cars and 52% fewer emissions than gasoline powered cars. Even if you don’t change any numbers except for the pounds of CO2 emitted per kWh of electricity generation, electric cars still do better than E85 powered cars. These are much more realistic numbers. And the great thing about electric cars is that, as our electricity becomes cleaner over time, so do all of our cars.
Even so, I’ve always felt that for our country’s security and for the benefit of the environment, it is important to have as diverse an energy/transportation portfolio as possible. There are many reasons to have both electric cars and biofuels. Both improve on the environmental impacts of living and both fulfill different needs. Personally I think electric cars make a lot of sense and they will eventually win out over combustion engines naturally, but it will take some time. In the meantime we need biofuels to increase our energy security and lower the environmental impact of our current fleet.