I see a serious problem with bio-diesel from soy-beans. Currently an average to excellent soybean yield is about 50 bushels/acre. At $12.00 a bushel that is a $600 annual/acre crop, however at best it will yield about 75 gallons of oil and 60 gallons of bio-diesel. That means with zero capitol and processing expense, the bio-diesel has a crop cost alone of $10.00 per gallon.

I understand that Minnesota has enacted a 2% bio-diesel law that requires nearly all diesel fuel to be blended with 2% bio-diesel, now Minn is attempting to raise it to 20%. Now I don’t know how much nearly is, but here is a web-site to explain it further.

http://www.mda.state.mn.us/searchtemplates/search.aspx?terms=bio-diesel+...

Here is a web-site of oil yield for oil-bearing crops.

http://journeytoforever.org/biodiesel_yield.html#ascend

Do you think the soy meal will make up for the loss plus pay the capitol costs of the oil extraction, bio-diesel conversion processes, blending and transportation costs?

"“Last year, corn kept trying to find that $4.60 going into market, soybeans are now faced with the same situation,” Hannagan said. “This year, soybeans will be the leader. The function of the market is to ration the crop, and that means that we have to get between 7 million and 8 million more acres for soybeans.

“We’re going to get some acres from crop rotation, but the rest is going to have to come from price increases. If we were to plant only 6 million more acres, with no change in demand, ending stocks on Sept. 1, 2009, would be slightly under 100 million bushels. So you can see the urgency that beans have and why beans are over $11. I would suspect that $12.75 on that March soybean contract before March expires would be a realistic objective.”

http://deltafarmpress.com/topstory/071224-leading-change/

Sunflowers or rapeseed yield a lot better than soybeans, though it is true that you can do a lot more with the defatted soy meal.

It really isn't my intention to turn this into an ag forum, promise.
From the 1983 edition of The Encyclopedia Of Organic Gardening " The sunflower is a remarkably versatile commercial plant. Each part of the plant has an economic use: The entire plant can be used as fodder for livestock or poultry, the flowers yield a yellow die, the pith of the stalk can be used to make paper or a mounting medium for microscope slides. Since it has a specific gravity lower than cork, pith can also be used to make life preservers and belts."
This year I'm planning on using many more sunflowers down on the farm. Three feet inside my fence line I'm going to put a double row as a deer deterrent. Apparently deer are confused by depth not hight. I'm also going to try to plant them in squares and let the dead stalks hold my compost.
The Sunflower Seed Huller and Oil Press

Hemp is pretty useful. Oil and fibres for composites / insulating materials, paper and plastics. Its nitrogen fixing too.

http://en.wikipedia.org/wiki/Allocasuarina

She Oak is a nitrogen fixing plant which makes excellent firewood.

Guess it would be good to grow them on rotation with food crops.