ASTM International recently revised ASTM D7566 Annex A5—the Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons—to add ethanol as an approved feedstock for producing alcohol-to-jet synthetic paraffinic kerosene (ATJ-SPK). (Earlier post.) The revision of ASTM D7566 Annex A5 clears the way for increased adoption of sustainable aviation fuels because ethanol feedstocks can be made from so many different low-cost sources. Supporting this advancement is technology from Pacific Northwest National Laboratory (PNNL) and its industrial partner, LanzaTech. (Earlier post.)
PNNL developed a unique thermocatalytic process for converting ethanol into ATJ-SPK. The first step of the process is to convert the ethanol into ethylene (“dehydration”). During the second step (“oligomerization”), ethylene molecules are chemically combined to build the range of hydrocarbon molecules needed for aviation fuel.
These hydrocarbons are then hydrogenated, followed by fractionation to produce alcohol-to-jet synthetic paraffinic kerosene with the desired properties. The process can use ethanol from any source, including ethanol produced via LanzaTech’s proprietary gas-to-ethanol process.
PNNL worked with LanzaTech to scale up the catalyst, and LanzaTech scaled up the entire process to produce 4,000 gallons of ethanol-derived ATJ-SPK.
LanzaTech compiled the data from extensive analysis and testing of the ATJ-SPK product into a research report for review by the Federal Aviation Administration as well as aircraft and engine OEMs. The review verified that the ATJ-SPK meets all fit-for-purpose properties required by ASTM D4054, the Standard Practice for Qualification and Approval of New Aviation Turbine Fuels and Fuel Additives.
Following this review, a ballot was submitted to the ASTM membership to approve the addition of ethanol as a feedstock in ASTM D7566 Annex A5, which passed on 1 April of this year. A second ballot also passed, increasing the blend ratio of ATJ-SPK to 50% from 30%. As a result, sustainable aviation fuel produced from ethanol using an alcohol-to-jet process can be used by commercial airlines in up to 50% blends with conventional jet fuel.
ASTM qualification of ethanol derived jet fuel means that where there is sustainable ethanol we have the potential to produce low carbon jet fuel. The scale of production is what matters, and the inclusion of ethanol in ASTM D7566 Annex A5 is, therefore, hugely significant as it means we can access large volumes of sustainable ethanol feedstock globally to support the aviation sector’s decarbonization targets.—Jennifer Holmgren, LanzaTech CEO
This work was supported by the Department of Energy’s Bioenergy Technologies Office.