Todd Rich writes:

http://www.sciencedaily.com/releases...0705231841.htm

"There is just no energy benefit to using plant biomass for
liquid fuel," says David Pimentel, professor of ecology and
agriculture at Cornell. "These strategies are not sustainable."

He's looking at the wrong plants-- try algae [large file]:
http://www.eere.energy.gov/biomass/p...from_algae.pdf

Some kinds of algae make 100 times as much oil as soybeans.
Soybean-based biodiesel is popular in the US because the soybean
farmers are subsidised.

Diesels can also burn straight vegetable oil, which saves a lot
of processing. It has to be heated, but that's no big deal.

I'm not sure what this has to do with metalworking...