The Low-Down on Military Specs for Renewable Jet Fuel
There are currently three sources of JP-8 for military use: petroleum-derived (not including tar sands Fischer–Tropsch-derived, and renewable-derived. Petroleum-derived jet fuel is the traditional fuel. It is obtained by refining crude petroleum. About 9 percent of a barrel of crude oil is refined to jet fuel for commercial and military use. FT fuels are those produced from either natural gas or coal. This technology was utilized by Nazi Germany during World War II to create liquid fuels from coal. Renewable fuels are more modern than either petroleum- or FT-derived fuels in use and development. As the term renewable implies, jet fuel from this source is produced from something that is produced in a repeatable cycle, such as farming.
The current military specification for jet fuel utilized by the USAF recognizes all three sources. While the major portion of fuel utilized by the USAF is petroleum-derived, efforts are underway to qualify fuels derived from both FT and renewable sources. In the future, this will enable aircraft in the USAF fleet to utilize JP-8 from any source, either as a blend with petroleum-derived JP-8 or, eventually, as a standalone fuel.
The technical criteria that JP-8 must meet to power a USAF aircraft are detailed in MIL-DTL-83133F, a 22-page document. It is important to realize that this document doesn't say what the fuel must be, but only what the fuel must possess in terms of physical properties. It is like the difference between saying you want a 75-pound animal that is yellow in color, has a great disposition and retrieves versus saying you want a Labrador.
In this manner, MIL-DTL-83133F states what the fuel must do, no matter its origin. This includes properties that both petroleum- and FT-derived JP-8 must also satisfy, including a freezing point of minus 52.6 degrees Fahrenheit, a net heat of combustion of 18,700 British thermal units per pound and a distillation curve identical to petroleum-derived JP-8.
Those interested in biofuels should be excited for the future, since airplanes, both military and commercial, will be fueled by jet fuel obtained from petroleum, FT technology, and renewable sources. In many ways, the military specification for jet fuel is paving the way for the production of fuels from renewable biomass resources, which can only help to keep our skies blue.
Paul Pansegrau is a research scientist at the EERC. He can be reached at firstname.lastname@example.org or (701) 777-5169.