Weizmann's process employs the bacterimum Clostridium acetobuylicum to ferment sugars into acetone, butanol, and ethanol. The researchers at Berkeley have developed a catalyst enabling removal of the acetone and butanol while leaving the ethanol behind.
The fuel generated appears to be very compatible with diesel.
In this case, the extractive fermentation process uses less than 10 percent of the energy of a conventional distillation to get the butanol and acetone out. This is where the major energy savings are.