Commercial airlines can significantly reduce pollution by using biofuels, according to a NASA study that found biofuel-powered jet engines reduces particle emissions in their exhaust by as much as 50 to 70 percent.
The findings, a result of a cooperative international research program led by NASA and involving agencies from Germany and Canada, and are detailed in a study published in the journal Nature.
It follows an earlier report from Lux Research that found biofuels will be key to achieving the aviation industry’s pledge to cut CO2 emissions to 0.2 billion tons (GT) in 2050 — half the 2005 figure — as opposed to the 2.1 GT projected by current growth rates.
For the NASA study, researchers collected data on the effects of alternative fuels on engine performance, emissions and aircraft-generated contrails at altitudes flown by commercial airliners during flight tests in 2013 and 2014 near NASA’s Armstrong Flight Research Center in Edwards, California.
The tests involved flying NASA’s workhorse DC-8 as high as 40,000 feet while its four engines burned a 50-50 blend of aviation fuel and a renewable alternative fuel of hydro processed esters and fatty acids produced from camelina plant oil. A trio of research aircraft took turns flying behind the DC-8 at distances ranging from 300 feet to more than 20 miles to take measurements on emissions and study contrail formation as the different fuels were burned.
Contrails are produced by hot aircraft engine exhaust mixing with the cold air that is typical at cruise altitudes several miles above Earth’s surface, and are composed primarily of water in the form of ice crystals.
Researchers are most interested in persistent contrails because they create long-lasting, and sometimes extensive, clouds that would not normally form in the atmosphere, and are believed to be a factor in influencing Earth’s environment.
“This was the first time we have quantified the amount of soot particles emitted by jet engines while burning a 50-50 blend of biofuel in flight,” said Rich Moore, lead author of the Nature report.
Researchers plan on continuing these studies to understand and demonstrate the potential benefits of replacing current fuels in aircraft with biofuels. It’s NASA’s goal to demonstrate biofuels on its proposed supersonic X-plane.