How much energy does it take to produce biodiesel / bioethanol?

Apparently David Pimentel, a professor at Cornell University, published a paper in 2005 with Tad W. Patzek of the University of California, Berkeley stating that the corn-to-ethanol process powered by fossil fuels consumes 29 percent more energy than it produces.

For more info, check out this link, with everything you want to know about ethanol:
http://select.nytimes.com/search/restricted/article?res=F20C11F83C5A0C778DDDAC0894DE404482

You might need NYTimes Select to log in--I'm not sure...but it's a lengthy Q&A; with Jim Motivalli, one of the NYTimes' car guys and also an editor at E (the Environmental Magazine). It's a pretty good article.

I little further reading on Pimental might be helpful here. He's quite the controversial figure.

http://www.worldchanging.com/archives/003042.html

xian, in all fairness to Pimental, the criticism in your link is that his calculations are off IF WE CHANGE ALL OF OUR CURRENT AGRICULTURAL PRACTICES. Which isn’t likely to happen anytime soon. If Pimental had used such an unrealistic and biased calculation, his study would have been no more useful than any other utopian prediction. Pimental’s study is valid for today’s production. Much of the production toward ethanol and biodiesel today ignores that the overall net effect on the enviroment WITH THE CURRENT TECHNOLOGY is negative, largely because the green issues are merely a red herring for the true intent, agribusiness subsidies. Not to say research shouldn’t continue, but wide-scale production and use should not commence until the net environmental effect is at least more positive than petrochemicals.

Bigfish and occ: A surprising source of “hard engineering” answers to ethanol, biodiesel, alternative fuels and global warming can be found in various Car and Driver columns.