NASA Confirms Biofuels Cut Jet Pollution

Using a biofuel mix to power jet engines reduces particle emissions in their exhaust by as much as 50 to 70 percent compared to conventional fuels, according to a recent NASA study. The new research results, which were published in the scientific journal Nature last week, were derived from a test series using a DC-8 flying at altitudes up to 40,000 feet while its four engines burned a 50-50 blend of aviation fuel and a renewable fuel produced from camelina plant oil. Three research aircraft took turns flying behind the DC-8 at distances ranging from 300 feet to more than 20 miles to measure emissions and study contrail formation as the different fuels were burned. "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 NASA scientist Rich Moore, lead author of the Nature report.

The formation of contrails is key to aviation's impact on climate change, according to NASA. Contrails are produced by hot aircraft engine exhaust mixing with the cold air at cruise altitudes, and are composed primarily of water in the form of ice crystals. Persistent contrails can 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. In fact, contrails, and the cirrus clouds that evolve from them, have a larger impact on Earth's atmosphere than all the aviation-related carbon-dioxide emissions since the first powered flight by the Wright brothers, according to NASA.

"Soot emissions are a major driver of contrail properties and their formation," said NASA scientist Bruce Anderson. The reductions in particle emissions observed during the flight tests, he said, "should directly translate into reduced ice crystal concentrations in contrails, which in turn should help minimize their impact on Earth's environment." Researchers plan to continue these studies to understand and demonstrate the potential benefits of replacing current fuels in aircraft with biofuels. NASA also said it plans to demonstrate biofuels using their proposed supersonic X-plane.