In 2014, Boeing proposed the possibility of using green diesel at a low blending ratio to produce aviation drop-in fuel. Green diesel is produced from vegetable oils and animal fats via the same base method as HEFA biojet fuel: the catalytic hydro-deoxygenation of fatty acid esters and free fatty acids (e.g. bio-oils and fats). The process produces diesel fuel as well as light (naphtha) hydrocarbons. The aviation fuel requires additional hydroprocessing and fractionation to achieve the lower freezing point required for use in aircraft. HEFA is approved for use for up to 50% when mixed with conventional jet fuel.

However, this additional processing induces increased cost and a lower product yield, noted a December 2014 IATA report on alternative fuels—a disincentive for producers to make biojet fuel.

Boeing has proposed that as initial step, blending a low ratio of green diesel in order to comply with the jet fuel freezing point would make aviation biofuel more widely available and price competitive with Jet A, including US government incentives.

Boeing’s Green Diesel concept, in three slides. Click to enlarge.

Diamond Green Diesel in Norco, La., produced the 757’s green diesel from waste animal fats, inedible corn oil and used cooking oil to reduce lifecycle CO₂ emissions by up to 80% less than petroleum jet fuel.

The green diesel flight to Langley was coordinated with the US Federal Aviation Administration, Pratt & Whitney and Honeywell, among others; EPIC Aviation blended the fuel. In December 2014, the ecoDemonstrator 787 made the first-ever flights with green diesel.

Among more than 15 technologies on the 757 test plane, Boeing has begun testing solar and thermal “energy harvesting” to power electronic windows, as a way to reduce wiring, weight, fuel use and carbon emissions. Also, on the 757’s flight deck, Boeing has installed a 3D-printed aisle stand made from excess carbon fiber from 787 production to re-purpose this high-value material and reduce airplane weight and factory waste.

With the ecoDemonstrator, Boeing looks to reduce environmental impact through the airplane's lifecycle, from improving fuel efficiency and cutting carbon emissions to recycling production materials In addition to our new technologies, flying the ecoDemonstrator 757 with U.S-made green diesel is another positive step toward reducing our industry’s use of fossil fuel.

—Mike Sinnett, vice president, Product Development, Boeing Commercial Airplanes

NASA and TUI Group, the world’s largest integrated tourism group, are collaborating with Boeing on ecoDemonstrator 757 tests. TUI Group is collaborating with Boeing to demonstrate its commitment to innovate for a more sustainable future for air travel and tourism.

This spring, under contract with NASA’s Environmentally Responsible Aviation (ERA) Project, the ecoDemonstrator 757 tested active flow control on the vertical tail and bug-phobic coatings on the right wing. With the exception of Boeing proprietary technology, NASA’s knowledge gained by collaborating with Boeing on ecoDemonstrator research will be publicly available to benefit the industry.

We have been thrilled with the data we were able to obtain from our experiments during the ecoDemonstrator 757 flight campaign, and are excited about the impact these NASA-developed technologies will have on the US air transportation industry.

—Ed Waggoner, director of NASA’s Integrated Aviation Systems Program

Since it was launched in 2011, the ecoDemonstrator Program has tested more than 50 technologies with a Next-Generation 737 (2012), 787 (2014) and 757 (2015).

Resources

• IATA 2014 Report on Alternative Fuels