[3am]

But most ethanol is net energy negative. Brazilian sugarcane is an exception, but it loses some of its advantage when it's shipped to the US in tankers. Even then, sugarcane requires non-renewable inputs (just not as much as corn). Cellulosic ethanol (from plants that can grow well on marginal farmland, like switchgrass) _is_ still in its infancy. Also, most current engines would need to all be retrofitted to run on anything much greater than E85 because of the greater corrosion.

You're right, though, I should've said something like 'practical biofuels' are in their infancy. I was really more referring to algae oil based petroleum or butanol, as they seem like the most promising candidates for a net-energy positive and high energy density renewable fuel.

(also, it's very cool that you ran on that in the 80s, mind if I ask what kind of car it was, or if you'd had it customized?)

[rbanffy]

> Even then, sugarcane requires non-renewable inputs (just not as much as corn)

I'm not aware of any. Fertilizers?

> most current engines would need to all be retrofitted to run on anything much greater than E85 because of the greater corrosion

OTOH, once the engines get retrofitted (mostly a surface treatment, IIRC), ethanol burns much more cleanly, with much less combustion residue buildup. The early engines had corrosion problems, but once the surface treatment problem was solved, they enjoyed longer active life than their hydrocarbon-burning counterparts.

> mind if I ask what kind of car it was, or if you'd had it customized?

It was a stock Volkswagen Gol (a project derived from the 1st-gen Passat). You can see a couple pictures here: http://carros.uol.com.br/album/volkswagen_gol_historia_album.... At the time, my aunt worked at their engineering department and got one for me as a gift. Mine was a third-generation ethanol engine. She was involved in the ethanol vehicle project.

Most cars you can buy in Brazil today are bi-fuel and can run with any mix of ethanol and gasoline. It's often a good idea to run the car with ethanol from time to time to clean the engine, as ethanol actively removes residue buildup.

[3am]

That is very, very cool. Thank you for posting the link and for the details on retrofitting the engines. I don't know if you're in Brazil, but my understanding is that they are way ahead of the US in renewable fuel usage. Most of our ethanol is corn based for technical and political reasons, and corn is a worse feedstock because it's more difficult for yeast to metabolize and it requires more fertilizer. So it's not nearly as economical here. And you are right, fertilizer is the non-renewable input. Most of the N (nitrogen) in NPK (nitrogen/phosphorus/potassium) is ammonia or urea derived from natural gas via something called the Haber Process.