A blend of conventional jet fuel with biofuel has been found to significantly reduce particle emissions from airliners, say an international group of researchers.

While today's planes are about 70 per cent more fuel efficient compared with those from the 1960s, they are still responsible for about two per cent of human-generated CO2, a main driver of climate change. In 2015, that amounted to 781 million tonnes.

Aware of the effect jet travel has on climate change, the airline industry has been seeking greener alternative fuels to further reduce emissions.

In the new study, scientists conducted test flights in 2013 and 2014 using a 50-50 combination of biofuel and conventional fuel on a NASA DC-8. Analysis revealed that particle emissions from the plane were reduced by anywhere from 50 to 70 per cent using the mixed fuel.

Biofuels can be made from natural sources such as algae and plants like camelina or jatropha, which can be grown almost anywhere and do not have to compete for agricultural land or displace food crops.

100% biofuel the goal

Canada's National Research Council has been studying the application of biofuels for some time. In 2012, researchers tested a plane using 100 per cent biofuel — something that the industry is aiming for, pending government approvals.

Anthony Brown, who works at the flight research laboratory with the NRC and who participated in both studies, said that Canada has been researching biofuels "from the word go."

A camelina seed pod is cracked open. Camelina can be used as biofuel along with several other plants like jatropha. (Gillette News Record/Sarah Voegele/Associated Press)

"It's a big deal," Brown said of the new findings. While research into cleaner fuel continues, Brown said that the airline industry is slower than the automobile industry, for example, in terms of research.

"Incrementally, researching the use of biofuel in jet transport aircraft is a piece-by-piece, step-by-step process."

Benefits and challenges

An advantage for airlines is that they don't have to worry about costly modifications to their planes: biofuel operates in the system the same way as conventional fuel.

As well, the plants used in biofuels are a sustainable resource and absorb CO2 as they grow, which is then released back into the atmosphere when the fuel burns.

Then there's the benefits to airlines.

Fuel costs are the single greatest expense for airlines and fluctuating oil prices create problems, said Rich Moore, lead author of the report. If airlines could rely on a sustainable and economic resource like biofuel, it could eventually help save them money.

"But they're also looking at it for the environmental impacts," Moore said. "And that will become more important in the future as society and governments look at policies and regulations targeting aviation environmental emissions."

NASA's HU-25C Guardian aircraft flies 250 metres behind the agency's DC-8 aircraft on May 14, 2014, before it descends into the DC-8's exhaust plumes to sample ice particles and engine emissions. (National Research Council of Canada)

The researchers believe that biofuel could be adopted widely by airlines within the next 10 years. But there are some challenges that need to be overcome first.

The main one is cost. Moore said that at the moment biofuel costs about $18 US a gallon. That's a steep premium over the current cost of about $4 US a gallon for conventional fuel.

"Right now the major downside is cost, and that is mainly [because] the fuel supply isn't there yet; it's not mature," Moore said.

"But the expectation is as we move forward and as industry and companies in the private sector come up with innovative ways to produce these biofuels in a sustainable way, the cost will come down dramatically."

Risk for developing countries

While arable land may not be sacrificed for biofuels in Western countries, it could be different for developing countries, said Seth Dworkin, associate professor at Ryerson University's department of mechanical and industrial engineering, who was not involved with the study.

"If a plane takes off in Toronto and lands in Nairobi, it has to be fuelled with essentially the same fuel," he said. He's concerned that, in developing countries, arable land might be sacrificed to grow crops for biofuel in place of food.

"It's still a potential disadvantage that needs to be considered very carefully."