Ethanol itself is far superior to petroleum distillates for internal combustion engines, especially small displacement turbocharged ones. This point needs to be made /extremely/ clear to everyone before pursuing the political end of the discussion.
I don't see why that needs to be extremely clear for this discussion. But regardless:
Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Gasoline has an energy density of almost 10,000 Wh/l and pure Ethanol only 6,000.
Ethanol is inferior compared to basically any combination of gasoline + non-ethanol octane booster.
Volumetric energy density isn't the only consideration for fuels though. Ethanol burns cooler, faster, and with more stability. When you raise the octane rating to reduce detonation you also reduce wear on the internals, allowing the manufacturer to use cheaper components. The same is true for the lower exhaust gas temperatures with exhaust values and turbo inlets. Current mileage standards have also caused manufacturers to jack up cruise-area ignition timing to extract a more complete burn before TDC from gasoline, which risks increased knock, and isn't as much an issue with ethanol. I also can't fail to mention the disgusting layer of grease and soot that covers the inside of engine, gas tank, and exhaust components (and the rear end of your car) from gasoline. Again, not much of an issue with ethanol.
These strengths are almost never written about or discussed. I agree with many of the points of the article in terms of the production efficiency issues, and corn being a weak production candidate, but I can't stand if/when this becomes an ethanol-substance bashing bonanza.
I also can't stand (in the overall discourse on the matter) when the article's points are used against the adoption of ethanol over petroleum. These aren't reasons against ethanol, they're reasons to work towards optimizing the means of production.
I also can't stand (in the overall discourse on the matter) when the article's points are used against the adoption of ethanol over petroleum. These aren't reasons against ethanol, they're reasons to work towards optimizing the means of production.
I agree, but I actually thought the article was pretty careful about specifying that it was ethanol produced from corn and sugarcane that they were talking about.
Energy/volume is irrelevant (at these levels). What really matters is the usable energy coming out the engine compared to the engine coming in. Because of its higher octane, ethanol could in principle be run in ICUs with much higher compression ratios than engines designed for gasoline use have, giving higher efficiency (like diesel engines have higher efficiencies). The problem is that no engines actually are tuned for maximum ethanol efficiency, since that makes them unusable with gasoline. (Turbocharging somewhat offsets this, which is why I assume the grandparent specified this, but only partially.)
