The results of a multi-year practical study conducted by NASA in association with Canadian and German agencies has found that particle emissions can be cut by up to 70% when a jet engine is fuelled by something other than standard aviation fuel.
To test the effects on the environment of different types of potential jet fuel, NASA conducted a series of flights in California over 2013 and 2014 using a DC-8 plus three further aircraft that followed in its wake in order to sample the air.
These planes also monitored contrail formation, the white, cloud-like vapor left in an airplane's wake when flying at certain altitudes and in certain weather conditions.
When standard aviation fuel burns, soot particles are deposited into the atmosphere, therefore increasing air pollution. However, contrails have a greater negative impact, generating cloud cover that artificially changes the Earth's temperature, holding in heat that would otherwise escape or preventing the sun's rays from efficiently penetrating the ground.
The full results of the study's findings, which form part of the larger Alternative Fuel Effects on Contrails and Cruise Emissions Study, or ACCESS, will be published in the journal Nature in April and point to extremely promising results for a biofuel made up of hydro processed esters and fatty acids produced from camelina plant oil mixed in equal quantities with standard aviation fuel. In tests at 40,000 feet soot particle exhaust emissions were cut by between 50-70%.
"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.
"Soot emissions also are a major driver of contrail properties and their formation," said Bruce Anderson, ACCESS project scientist at NASA's Langley Research Center in Virginia. "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."