Source: News Bharati English19 Mar 2017 11:10:36
Washington, March 19: According to a study published in the journal ‘Nature’, using biofuels to help power jet engines reduces particle emissions in their exhaust by as much as 50% to 70%. A team of scientists led by the United States space agency had put a 50-50 blend of normal jet fuel and biofuel into a NASA DC-8 aircraft and then flew small chase planes fitted with instruments 100 to 500 feet behind them to measure the emissions.
Biofuels are an attractive option for aviation because they contain very little or no sulfur and aromatics, unlike petroleum-based fuels. As a result, they reduce the emissions of sulphates and soot particles by reactors, which have an impact on air quality and the formation of clouds of condensation, these typical white streaks produced by aircraft in flight in their wake.
"Those dust particles serve as nuclei for water vapor in the very cold atmosphere to condense on and for the artificial-looking linear contrails that we see when we look out the window," said Richard Moore from NASA's Langley Research Center, and who led the research team. You’ll then see those lines spread and form cirrus clouds that weren't there before the plane flew through the airspace.”
"We know these contrails and cirrus clouds have a warming effect on the Earth's climate, and it's currently thought the warming effect associated with those clouds is more significant than all of the carbon dioxide emitted by aviation since the first powered flights began.”
Previous studies on the effect of jet fuel had been conducted on a grounded jet by locking it down and throttling up its engines, but scientist wanted to see how the particles interacted with the far colder air at cruising altitudes between 30,000 and 40,000 feet.
To ensure they were only measuring pollution from the contrails of the aircraft they were following, scientists flew between 30 meters (98 feet) and 150 meters (492 feet) behind the aircraft. The study found it cut the amount of black carbon 50% by number and 70% by mass.
The 50-50 jet-fuel burned by the DC-8's four engines was “a renewable alternative fuel of hydro processed esters and fatty acids produced from camelina plant oil,” according to a NASA press release.
While the promising results may suggest it would be logical to only use biofuels, Dr. Moore said a number of engineering and infrastructural limitations, including some jet engines needing a certain quota of traditional jet fuel to function safely, meant that wasn't currently possible.