Expanding airline sector is under major pressure to reduce its CO2 emissions, writes Ciarán Hancock.

AT 11.34am on February 26th a little piece of aviation history was made at Heathrow Airport in London.

Virgin Atlantic flight VS811P took off with five crew on board and headed for Schipol Airport in Amsterdam powered by a mix of kerosene and biofuel on a unique demonstration flight which is a baby step along the way to greener air travel.

Fuelled by a combination of Babassu - a vegetable oil - and coconut oil, the aircraft reached an altitude of 7,620m (25,000ft) on its 40-minute journey. The flight was a collaboration between Virgin, aircraft-maker Boeing, engine manufacturer GE and Imperium Renewables, which is involved in producing biofuels.

Virgin described the demo flight as very successful. "We've shown that it is possible to fly a plane using biofuel," the airline added. "Virgin is now handing the baton to Air New Zealand, which will be operating the next biofuel demo flight later this year. This is part of a much bigger project with Boeing, Air New Zealand and other industry partners looking at what needs to happen to establish a sustainable market for biofuel for aviation."

Virgin said that each demo flight would take the industry a step closer to identifying a long-term, sustainable solution for fuel requirements. That said, Virgin has no plans for another biofuel demo flight.

Never ones to run with the herd, Ireland's Ryanair has no plans to operate a biofuel demo flight, dismissing Virgin's flight as a publicity gimmick. "We're not going to have aircraft flying on biofuels," said Jim Callaghan, Ryanair's head of regulatory affairs. "Where the hell are they [ the biofuels] going to come from? Food prices are going through the roof because of biofuels. I think the biofuels debate is rapidly nearing its end."

This view is not shared by Boeing, whose aircraft Ryanair uses. "Based on test results we're seeing in both laboratory and engine ground test scenarios, we believe that second-generation biofuels have significant promise for commercial aviation in its ongoing efforts to reduce carbon emissions and dependence on petroleum-based jet fuels," the airline told Innovation.

Investment in biofuels continues to rise - from $5 billion (€3.16 billion) in 1995 to an estimated $100 billion by 2010, backed by the likes of Sir Richard Branson and George Soros and major car manufacturers.

Callaghan's point about biofuels, however, is well made. The grain it takes to fill an SUV tank with ethanol could feed a person for a year. Swathes of the Brazilian rain forest has also been lost to biofuels, a questionable pay-off for the environment.

Boeing is pressing ahead with other biofuel demo flights. It is collaborating with Air New Zealand and Rolls-Royce on a test flight later this year and recently announced that a similar demo will take place with Continental Airlines of the United States and engine-maker GE in the first half of 2009.

The Seattle-based aircraft-maker said it was also looking at a raft of other measures to make flying more green. These range from "progressive new products" such as the 787 Dreamliner and the 747-8 Intercontinental to "advocating improvements in air-space efficiency, pioneering the use of innovative, lighter-weight composite materials and helping to advance biofuel development".

Engine-makers are doing their bit, too. GE, which, with Rolls-Royce, dominates the aircraft engine market, says that its new Genx engine is 15 per cent more efficient than its predecessor and 181.4kg (400lb) lighter.

Virgin says in the longer term it anticipates second-generation feedstocks such as jatropha and/or algae being able to meet a significant proportion of aviation's fuel requirements. "Neither algae or jatropha conflict with food or drinking water supplies."

With the price of a barrel of oil above $110, every airline in the world is exploring ways to trim its fuel bill.

Ryanair claims to have the youngest, most fuel-efficient fleet of any airline in the western world. It flies to mostly secondary airports, so it does not have to waste fuel circling congested runways waiting for an all-clear to land. Callaghan says that the configuration of its aircraft means that its fuel burn per passenger is the lowest in the industry. "We are about as efficient as we can get," he says.

Ryanair is facing a fuel bill of about €1.2 billion, roughly 50 per cent ahead of what it paid in the year to the end of March 2008. The airline is now campaigning for greater co-ordination of routes across Europe and more effective management of air space by the various national bodies in a way to lessen the impact of aviation on the environment.

For example, if you travel from Dublin to London, your flight will be routed over Liverpool or Manchester due to restrictions in the air space over Wales by the British military.

"The technology exists now to avoid that type of thing, but it's not just about inefficient flight paths," Callaghan said. "There's incredible fragmentation in Europe with, I think, something like 27 national air-space providers."

This is currently under review by the European Commission, which has set up a project called Sesar with four long-term goals - to increase safety, reduce the environmental impact of aviation, increase the capacity for air travel and reduce the cost of providing air traffic services.

"It's about making sure that all the information is available to all who need to know so that everything can be programmed a little bit better," said Bob Hilliard, a senior executive of the Dublin Airport Authority.

Hilliard said there was no reason why more direct flight paths between cities and airports could not be introduced. "The technology exists to do that. Aircraft navigation equipment is really precision stuff and aircraft can fly with huge precision."

The Sesar project is due to conclude in June with recommendations being made to the European Union.

It is not all bad news in the sector. Fuel efficiency has improved 70 per cent in four decades. Airlines now burn four litres of fuel a passenger per 100km flown, about the same average as cars, according to Boeing.

Still, the aviation industry accounts for 1.6 per cent of global greenhouse gas emissions, according to the European Environmental Agency. Airliner emissions are expected to increase by 3 per cent annually through 2015, the agency says.

This point irritates Callaghan and Ryanair. "There's a lot of scare-mongering out there by environmental groups about the aviation industry," he said. "Maritime transport is 4 per cent of [ emissions], yet nobody is screaming about marine transport. Aviation is recognised as being one of the major engines of growth in the European economy - we need to be careful about that."