This testing is being performed as part of the previously announced contract with Gevo to supply more than 16,000 gallons to the US Army.

Gevo’s isobutanol can be used to produce a variety of conventional military jet fuels such as JP5, JP8 and commercial aviation jet fuel. We are pleased to see that the Department of Defense is moving forward with its ‘Farm to Fleet’ initiative and we would like to see the alcohol-to-jet from isobutanol be used as a blendstock for the ‘Farm to Fleet’ program that aims to produce renewable fuels in the USA. We greatly appreciate the U.S. Army’s partnership and support in this effort. ATJ from isobutanol is a clean burning, homegrown, bio-jet fuel, and we have a potential route to deliver aviation biofuels at scale and at competitive cost for many aircraft platforms including military and commercial.

—Patrick Gruber, Gevo CEO

Three pathways to SPK: FT (left); hydrogenated oil (center); ATJ (right). Source: Gevo. Click to enlarge.

ASTM has already approved two synthetic fuel pathways—gas-to-liquids and hydroprocessed oils—for the production of synthetic paraffinic kerosene (SPK) for aviation use. ASTM has also assembled an alcohol to jet (ATJ) task force (D02.J0.06, Emerging Turbine Fuels) to investigate the requirements for this third major pathway.

SPK produced from alcohol feedstocks (ATJ-SPK) has the same properties as SPK produced through hydroprocessing bio-derived fats and oils (HEFA-SPK), or through the gasification-Fischer-Tropsch synthesis process followed by hydroprocessing (FT-SPK). All three routes to SPK (FT-SPK, HEFA-SPK, ATJ-SPK) rely on hydroprocessing followed by fractionation as the final steps to produce highly branched paraffinic kerosene in the same boiling point range as petroleum-derived jet fuel.

Gevo’s patented ATJ fuel is designed to be fully compliant with aviation fuel specifications and provide equal performance, including fit-for-purpose properties.

Gevo’s ATJ process involves the dehydration of isobutanol—which Gevo produces via fermentation—followed by oligomerization and hydrogenation. The Gevo bio-kerosene is the same as that conventionally produced from butylenes.

1. Isobutanol produced from starch or biomass is dehydrated over an acidic catalyst to produce isobutylene, which is then further reacted to product mixtures of longer chain aliphatic hydrocarbons.

2. A portion of this material is reacted separately to form high density aromatic compounds.

3. Hydrogen gas, a byproduct of the aromatization reaction, is used to remove unsaturated bonds in the aliphatic material.

4. The hydrocarbons then are blended in proportions that can meet all ASTM standards for fuels: isooctane is a dimer of dehydrated isobutanol and is a major component of the premium value alkylates, a key gasoline component; a trimer of the isobutylene (dehydrated isobutanol) is a jet fuel blend stock; a polymer of four and five isobutylenes can make a diesel blend stock.

Gevo has engineered yeast optimally to convert sugars to isobutanol, and has demonstrated concentrations of more than 107 g/l (goal >105 g/l) with a productivity rate of 2 g/l/h (goal 2g/l/h), according to a presentation the company made this summer at the Paris Air Show. The Gevo Integrated Fermentation Technology (GIFT) continually separates the isobutanol during fermentation.

Resources

• Alcohol to Jet (Gevo presentation)