Plant-powered planes show promise

Green' biofuels are increasingly being used by airline owners to reduce harmful emissions. But are they really a viable solution for powering every craft in the skies?

January 15, 2013
By Jon Stewart 

To the eye, there was nothing remarkable about the aging Falcon 20 jet as it took off from Ottawa International airport in Canada at the end of October in 2012. But the twin-engined, 10-seater plane was in the process of making aviation history.

After a short flight that saw it climb to 30,000 ft (9,000m) over the capital city, the plane touched back down at the airport to secure its world first.

"Today, I flew the world’s first 100% biofuel flight," said pilot Tim Leslie on landing the National Research Council of Canada (NRC) craft. "It is truly inspiring to take this step towards an eco-friendly future."

Unlike conventional aircraft which burn kerosene – a polluting fossil fuel - Leslie’s plane was powered by fuel derived from rapeseed oil. However, it could equally have been powered by one of a number of biofuels made from algae, flax, coconut husks or even from used cooking-oil.

These kinds of fuels are considered to be eco-friendly and “green” because the plants from which they are derived absorb CO2 from the atmosphere as they grow and release it when they burn, with no net addition of greenhouse gases to the atmosphere. As a result, they are viewed by many as one of the main ways the aviation industry can reduce its carbon footprint.

That’s important when you realize that aviation currently accounts for around 2% of all greenhouse gas emissions, according to the Intergovernmental Panel on Climate Change, although the effects are disproportionate to other types of pollution.

“In terms of climate impact it’s somewhat higher than that,” says Steven Barrett, assistant professor of astronautics and aeronautics at the Massachusetts Institute of Technology (MIT), and the director of the Laboratory for Aviation and the Environment. “Estimates vary from 5 to 10%, because of the altitude at which aircraft fly. Emissions from planes have a different impact than they would on the ground.”

For example, the contrails from a jet – those white streaks you sometimes see trailing a plane – are known to cause high-altitude cirrus clouds, which compound global warming.

Dropping in

It is generally agreed, that these effects will only get worse if nothing is done because air travel is growing….quickly.  In fact, between now and 2030, the number of passengers and number of fights is likely to more than double, according to the UN International Civil Aviation Organization. 
 
Airline manufacturers and carriers are all too well aware of these effects and are working to try to mitigate them.

“We feel it’s our responsibility to deal with our segment in a very aggressive way,” Dr John Tracy, chief technology officer (CTO) at Boeing, recently told me. “Probably 75% of the research and development dollars we invest in the commercial airplane side goes towards improving our environmental footprint.”

Long term,  new aircraft shapes could help, while even further into the future are the prospects of electric, hydrogen or even solar powered aircraft. However, these kinds of development are years – even decades – away. In the short term biofuels are looked on as a potential savior as most commercial passenger jets can use them with little to no modification, and because they seem to offer significant benefits.

For example, newly released figures collected by a plane trailing the Canadian Falcon 20 suggested that there was a 50% reduction in aerosol emissions compared to conventional fuel. Previous studies with the rapeseed fuel also show that there is a 25% reduction in particles and up to 49% reduction in soot – or black carbon - emissions compared to conventional fuel. Additionally, the NRC research also claims to show increased engine efficiency.

Read more here:   http://www.bbc.com