Upon reviewing the results of the test, which was conducted by the Southwest Research Institute (SwRI) and the Air Force Research Lab, the task force had no objection to Gevo proceeding to jet engine testing, the next phase in the certification process. Jet engine testing is expected in 2012, with full certification of Gevo’s biojet fuel expected in 2013.

ASTM is a consensus type organization; everybody has to agree for anything to move forward. It can be pretty tricky, having a full mix of competitors. For us, we’s following the established procedures: first establish a committee, then figuring out the protocols, testing the analytical method of how one goes about this. The fact that it is agreed upon by all the competitors is significant.

—Patrick Gruber, Gevo CEO

Gevo’s renewable jet. Gevo has developed and demonstrated the technology to convert isobutanol into aliphatic and aromatic hydrocarbons using known chemistry and existing refinery infrastructure:

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.

Our kerosene is the same as that produced from butylenes; it’s the same old kind of kerosene, made from C₄ building blocks. People have not had the paradigm of having exact drop-ins; we come along and the whole system is set up to make sure [the renewable fuel] actually works. But this is the same old kerosene.

—Patrick Gruber

Gevo’s proposition for the market is that it can cost-effectively produce and purify isobutanol to serve as the feedstock for this established process.

In April, Gevo signed an engineering and consulting agreement with Mustang Engineering, LP for the conversion of its renewable isobutanol to biojet fuel. This effort will focus on the downstream processing of isobutanol to paraffinic kerosene (jet fuel) for jet engine testing, airline suitability flights and advancing commercial deployment. (Earlier post.)

To further assist its entry into the jet fuels market, Gevo is engaged in discussions facilitated by the Air Transport Association of America (ATA) with several major passenger and cargo airlines in order to secure commitments from the ATA member airlines to purchase significant quantities of renewable jet fuel made from its isobutanol once the proper certifications have been obtained. To serve this market, Gevo is also in discussions with major refiners to produce renewable jet fuel using isobutanol at their refineries.

Gruber notes that Gevo could deploy pretty quickly because it takes a retrofit approach, converting ethanol plants (with a current global capacity of some 20 billion gallons) to work with Gevo’s microorganisms to produce isobutanol.

Any of [the existing plant infrastructure] is fair game. These are small capital projects. That’s not the same as everybody else; they have to build new greenfield plants.

—Patrick Gruber

Noting that “the bugs are coming along really nicely” Gruber said the Gevo is planning a 1-million gallon demo plant in the first half of next year.

Resources

• Benjamin G. Harvey and Heather A. Meylemans (2011) The role of butanol in the development of sustainable fuel technologies. Journal of Chemical Technology & Biotechnology Volume 86, Issue 1, Pages: 2–9 doi: 10.1002/jctb.2540