Compared to using conventional fuels, using biofuel blending jet engines can reduces particle number and mass emissions in their exhaust trails by as much as 50 to 70 percent, a new study from U.S. space agency NASA found.
Worldwide, flights produced 781 million tonnes of CO2 in 2015, according to the Air Transport Action Group (ATAG).
The cooperative international research, published in the journal Nature, was led by NASA and involving agencies from Germany and Canada.
The study shows that aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate.
Data was gathered during flight tests in 2013 and 2014 near NASA's Armstrong Flight Research Center in Edwards, California, looking at the impact of alternative fuels on the performance of engines, emissions, and aircraft-generated contrails seen at altitudes that commercial airliners fly at.
The test series were part of the Alternative Fuel Effects on Contrails and Cruise Emissions Study (ACCESS).
NASA described the contrails as being 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.
"Soot emissions also are a major driver of contrail properties and their formation," Bruce Anderson, ACCESS project scientist at NASA's Langley Research Center in Hampton, Virginia, said in a statement.
"As a result, the observed particle reductions we've measured during ACCESS should directly translate into reduced ice crystal concentrations in contrails, which in turn should help minimize their impact on Earth' s environment."
The benefits come not just from reducing carbon emitted directly into the atmosphere but by also cutting down the chance of contrails forming, which can have an even bigger impact on the Earth's atmosphere.
The results from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil.
"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 their proposed supersonic X-plane, according to the agency.
