Biodiesel vs Ethanol
From GoBiodiesel
Biodiesel Versus Ethanol the alternative fuels showdown
There are a lot of ways to compare biodiesel and ethanol. Here are a few. Please contribute to this page, but make sure to cite your sources!
__Gallons per acre:Corn ethanol yields about three times as much usable fuel per acre compared to Soy biodiesel, but neither are optimal crops.
Corn yields 230 gallons per acre for ethanol(source: EERC). Brazil's program that produces ethanol from sugar cane currently achieves about 600 gallons per acre. site has a table with the yields for other crops.
Most U.S. biodiesel is made with soybean oil which yields a low 70.13 gallons per acre. Euro biodiesel is primarily rapeseed which yields a better 127g/a, while palm oil yields an impressive 635g/a. Biodiesel can also be produced from algae, but it remains to be seen how many gallons per acre that will yield. (source: Journeytoforever.org)
The cooperative makes biodiesel from "waste" veggie oil, so yield per acre probably isn't the best model.
Interestingly, it takes a staggering 196,000 pounds of prehistoric plant matter to create 13 pounds of crude. This crude yields 6.2 pounds (one gallon!) of gasoline.
__Mileage:__ using biodiesel doesn't really have an impact on mileage. Ethanol has a lower energy content than gasoline, so vehicles using E85 typically get about 25% lower mileage than vehicles using gasoline. In addition, biodiesel benefits from the inherent fuel economy in diesel engines (20-50% better than comparable gasoline engines).
__Emissions:__ Both biodiesel and ethanol benefit from the carbon cycle, that is, burning either of them results in zero new C02, since the same amount of CO2 is taken in during the plant's lifecycle.
Someone needs to make a grid of this to make some sense: Ethanol 30% less CO2, Biodiesel 74% less (source: US DoE) Other emissions need further researching, but it appears from a cursory investigation that biodiesel has far lowered emissions across the board than ethanol.
__Compatibility:__ biodiesel runs in any diesel. It isn't clear that any vehicle can run on 100% Ethanol. Usually Ethanol must be blended with 15% fossil fuel gasoline, and is only compatible in a small fraction of gasoline powered vehicles.
Most gasoline in the US is already blended with a small amount of ethanol at certain times of the year.
__Costs:__ Apparently you can't buy E85 at the pump in Oregon even if you wanted to. Or in Washington State. There's a pump in San Diego, California. Federal subsidies make the cost at or less than gasoline.
Commercial biodiesel has no federal subsidies and is currently more expensive per gallon, about 5-20% more than gasoline mile per mile (because of diesel's greater fuel efficiency).
__Energy yield:__ You get 34% more energy out of ethanol than is required to produce it(from corn). On the other hand, you get 320% more energy from producing biodiesel than you put into it. (source: US Dept. Agriculture)
[This article] quotes a Cornell scientist who asserts that producing ethanol takes more energy than it gives back. His claim is that it takes 131,000 BTUs of energy to produce a gallon of ethanol, but a gallon of ethanol only has 77,000 BTUs of energy!
More research is necessary.
