soberups
Pees in the brown Koolaid
E10 is 10% ethanol 90% gasoline. It's mandated in about eight states. It creates less carbon emissions. However by doing a little six month study on my own, I averaged about a 10% loss in MPG, therefor needing more, which in turn doesn't really lower the emissions I was putting out compared to 100% gasoline.
The reduction in carbon emissions deends entirely upon the source of the ethanol. You are correct that ethanol decreases mileage, thereby requiring more fuel to be used overall. However, gasoline is emitting carbon that had been sequestered underground in oil, whereas ethanol is made from corn or other organic material that drew carbon out of the air thru photosynthesis of the crop from which it was harvested.
If we stopped drilling for oil and 100% of our fuel was refined from biomass, there would be no net increase in carbon emissions.
Making ethanol out of corn is not particularly efficient until you remember that most of the corn grown in this country is used for animal feed. If you refine corn into ethanol, the leftover mash is a high-protien meal that can still be fed to cattle. A cow eating this meal will emit far less flatulence since the starch in the corn has been removed and distilled into ethanol first. In a sense, you can say that burning ethanol in an engine is the same as burning cow farts...the gas was already going to be emitted either way, so it makes sense to capture that wasted energy first and use it intstead of a fossil fuel.