Oct 9, 2008

20% ethanol for every gas car?

The Department of Energy released a report today with their initial findings on a project to identify the effects of higher blends of ethanol in engines not designed for the fuel.

Vehicle results include the following when E15 and E20 were compared with traditional gasoline:

  • Tailpipe emissions were similar;
  • Under normal operations, catalyst temperatures in the 13 cars were largely unchanged;
  • When tested under full-throttle conditions, about half of the cars exhibited slightly increased catalyst temperatures with E15 and E20, compared to traditional gasoline; and,
  • Based on informal observations during testing, drivability was unchanged.
It is a little confusing that tailpipe emissions were similar. From research I've seen, 10% Ethanol blended in with gasoline decrease carbon dioxide (CO2) emissions by about 5%. E85 Flex Fuel (85% ethanol) decreases CO2 by about 41%.

It will be interesting to see where this research leads - bringing more ethanol into the fuel supply would decrease overall mileage, but it would decrease dependence on foreign oil as well.


Spencer said...

There should definitely *not* be a decrease in CO2 emissions per mile driven on a car running E85 versus gasoline.

What you may have mistaken it with is net CO2 emissions, because people who write about the CO2 emissions from E85 take into account the fact that the corn used to grow it absorbs CO2 (so the balance of CO2 emitted is somewhat less - perhaps 41% as you mentioned).

But either way, in an internal combustion engine, you will always have CO2 emitted, and no fuel will emit less except for hydrogen.

The same is true for biodiesel; B99 emits as much carbon dioxide as dino diesel, but when you take into account the CO2 absorbed by the soybeans used to make the biodiesel, the *net* CO2 emissions are less.

Sasha Friedman said...

Hi Spencer - you are correct in that I was referring to lifecycle emission decreases and not just straight tailpipe emission decreases. Pretty much whenever I quote emission statistics, they will be life-cycle based.

Lifecycle analysis takes a holistic look, from cradle to grave, at the different stages of inputs and outputs of a process.

This creates some interesting statistics and ideas - mainly a big boost for reducing and reusing.

For example, about 50% of a car's lifetime emissions will be generated by the time it gets to a dealer's lot - a good argument for buying used cars.