Originally Posted by
PILOTGUY
Hopefully a little additive can help with the freeze point. Jet fuel has a BTU (energy release) of about 132000-135000 per gallon. Biofuel is in the 130000-132000 range, so the energy difference is fairly small. The emissions reduction would be in the 60-80% range, according to Boeing.
Jet fuel is about 6.84 pounds per gallon, give or take due to the specific gravity of each batch made. Biofuel is 7.5 pounds per gallon.
Kudos to CAL for doing this flight.
Additives will get you a few degrees C unless you add a ridiculous amount...chemistry has it's limits. The freezing point is the biggest hurdle for most bio-fuels...they would simply require a redesign of the fuel system to keep the bulk fuel about 35 C warmer than current systems...$$$$$$$