KLM Royal Dutch Airlines will take a step closer toward "green" flying in September when it launches more than 200 flights operating between Amsterdam and Paris that run on a biofuel made from recycled cooking oil.

The fuel, produced by Dynamic Fuels and supplied by SkyNRG, does not require any mechanical changes to KLM's jet engines.

"In November 2009 we demonstrated that it was technically possible to fly on biokerosene," the company's managing director, Camiel Eurlings, said in a statement. "Now, a year and a half after our first demonstration flight on Camelina, a new phase has been entered around the world, that of certification."

Authorization will soon be granted to operate commercial flights on biofuel, he said.

The company is not the first to test the biofuel waters. Boeing in combination with Continental Airlines, now United Continental, tested a "green" flight in 2009 using a twin-engine 737-800 with fuel derived from algae and jatropha.

Boeing spokesman Terrance Scott had said there was a "noticeable improvement" of about 3% when comparing the blend with that of conventional petroleum.

Other airlines such as Air New Zealand, Qatar Airways and Lufthansa have also experimented.

While KLM said it is open to using different raw materials to make more environmentally-friendly fuels, as long as they meet a range of sustainability criteria such as a reduction in carbon dioxide emissions and minimum negative affects on food supply, challenges remain.

"The route to 100% sustainable energy is enormously challenging," Eurlings said. "The costs of biofuels need to come down substantially and permanently."