Well on track to making their aircraft run on coal, the US forces have just ordered 600,000 gallons of renewable jet fuel made from weeds, algae or rendered fat from animal corpses.
News of the biofuel push comes courtesy of Honeywell subsidiary UOP, which has been developing sustainable/renewable biofuels for use in jet engines since 2007, originally under the auspices of our old friends at DARPA. The Pentagon wildscience bureau originally called for jet fuel made from sources "including but not limited to plants, algae, fungi, and bacteria", raising the intriguing prospect of mushroom-powered air forces, but the programme seems to have developed along more conventional lines.
The past two years have seen trials of various kinds of "sustainable" or "second generation" biofuel in airliners, generally involving jatropha nuts, algae or similar feedstocks. Ordinary biofuels made from crops grown on farmland have acquired a bad reputation of late, being blamed for driving up food prices and causing hunger - not to mention the fact that they would tie up far more arable land than is realistically available if they came into widespread use.
Thus algae which can grow on unused water surfaces is seen as a good candidate for feedstock; so are plants such as jatropha or (as we have in this case) camelina weeds, able perhaps to grow on unused land. Another option is the use of fatty grease from livestock carcasses in the form of tallow - livestock which would have been raised anyway, so this comes under the heading of energy from waste.
Now, according to Honeywell, the US Air Force will buy 400,000 gallons of algae/weeds/corpse-fat jet fuel, and the US Navy will take 190,000 gallons. These fuels will be mixed with regular fossil juice to produce synthetic JP-8 which will be tested out for use on the full range of military aircraft.
The idea is not to reduce the US forces' carbon burden as such, but rather to provide an alternative source of supply in the event of war or crisis cutting off traditional sources. Nonetheless, by developing the technology, the contract may lead to more use of possibly-sustainable biofuels by civil air transport.
Synthetic jetfuel made from coal using the Fischer-Tropsch process is already certified on many US military aircraft, but this is actually worse in carbon emissions than using crude oil. About a tonne of coal has to be burned to produce a tonne of synthifuel with this method. The US air force doesn't care, though; what concerns them is that America has abundant coal reserves, but has to import crude oil.
"We are pleased to see that the US military is taking this important step toward the use of bio-derived jet fuel on its platforms," says UOP chieftain Jennifer Holmgren. ®