In the USA, the idea of a biofuel isn't sustainable. It's just a bunch of words meant to appease the worried -- and the outright stupid. However, I live in a part of the world where ethanol is more popular than gasoline and is somewhat sustainable -- as long as the number of car owners doesn't geometrically increase. NAFTA (no, not the North American Free Trade Agreement, this NAFTA is ethanol fuel) is readily available throughout Argentina, Uruguay, and the primary combustible fuel (about 80% of all vehicles) in Brazil. Granted, Brazil has wiped out a large portions of the tropical American rain forest, but they are no longer dependent upon Venezuela or any other country for oil. They are carefully conserving their oil reserves and untapped fields. The UK is has been shown in the local press to be especially pissed at Brazil's temerity to tell British Petroleum to fuck off. Soon, Argentina will take measures to do the same. It's amazing that such "third world" countries can be so intelligent about such natural resources once Europe and the USA are kicked out. These countries are certainly not without their problems. Buenos Aires is constantly running low on electricity during the summer months. They have plans to replace their current (and only) nuclear power plant near Bariloche before something bad happens. Of course, the USA is all flustered about Argentina updating its nuclear reactor or possibly building a second one; primarily because Argentines have pointed out that the French do a better job of building such power plants and containing the waste (they encase it in molten glass to stablize it, then store it in salt mines). In the US, they're still using metal containers for all their nuclear waste.
But back to biofuels: if the population is the right size and the government is behind it, biofuels are a reasonable intermediate solution until solar and hydrogen are perfected -- but not in the USA. It's too little too late for the USA.
Oh, and by the way, you should see the diesel fuel I put in my 407 Peugeot. It's clear and about the same consistency of a glass of water. It's incredibly clean burning and free of sulfur. No need to add red or green dye to the stuff. Although large buses and transport vehicles still use the old stuff, but it's being phased out.
They also don't use catalytic converters down here. Instead, Peugeot, Citroen, and Renault invested in developing a completely new, advanced generation of internal combustible engine that puts out more water vapor than hydrocarbons. They saw early on that the catalytic converter wasn't a viable, long-term solution. Now you know why you can't buy those French autos in the USA. They don't have catalytic converters because they put out less contaminants than American and Japanese autos that do have catalytic converters. What a concept. No?