Energy Yield

And the winner is...Biodiesel

Different studies show varying returns, but almost
always, biodiesel ranks at the top.

For every unit of fossil energy used in the entire bio-diesel production cycle,
3.2 units of energy are gained when the fuel is burned, or a
positive energy balance of 320 percent.

For more information about Energy Yield, see the following article:
Study By University of Minnesota Researchers Shows Biofuels are Energy Positive