Sky's the limit

12th February 2013


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Paul Suff reports on what the aviation industry is doing to reduce its environmental impacts

Emissions from aviation currently account for around 2% of total global carbon emissions. This proportion is expected to increase significantly in the near future. Global air traffic is growing at about 5% a year and, if no action is taken, by 2020 international aviation emissions are projected to be around 70% higher than they were in 2005, even if fuel efficiency improves.

The committee on climate change, which advises the government, reported in 2008 that carbon emissions from aviation in the UK had increased 50% between 1996 and 2007, and accounted for 5% of the country’s total greenhouse-gas (GHG) emissions. Projections by the transport department predict UK aviation emissions (from all domestic and international flights) will increase from 34 million tonnes of CO2 (MtCO2) in 2005 to around 48 MtCO2 by 2030.

Aviation emissions are not confined to carbon: aircraft emit other pollutants into the atmosphere, including nitrogen oxides (NOx), volatile organic compounds and carbon monoxide, that affect global warming. And the sector has wider environmental impacts, including noise, land use and air quality, which all need to be addressed as it plots a more sustainable future.

Four pillars

Pressure on the aviation industry to mitigate its climate change impacts has led it to set ambitious CO2 reduction targets. The sector as a whole has agreed to stop the growth of carbon emissions by 2020 and halve them by 2050 against 2005 levels.

The European Commission has also set a number of environmental goals as part of its Flightpath 2050 strategy. These include a 75% reduction in CO2 emissions per passenger kilometre travelled; a 90% reduction in NOx emissions; and a 65% reduction in perceived noise from flying aircraft. The commission’s targets are against a 2000 baseline.

According to PwC, reaching the global aviation targets will not be easy, and will require the industry to improve its carbon intensity by 5.1% every year. This will require the aviation sector to accelerate advances in fuel efficiency and scale-up biofuel production. Alternatively it could purchase carbon offsets.

The International Air Transport Association (Iata), which represents 240 airlines, and the International Civil Aviation Organisation (Icao), the UN body governing civil aviation, are pursuing a four-pillar strategy to achieve the industry’s climate goals that involves: improvements in technology, more effective operations, more efficient infrastructure and economic measures.

The sector says much of the improvement needed will come from technological advances, which could cut emissions per aircraft by up to 35%. Switching to alternative fuel sources, principally second-generation biofuels, could reduce emissions by a further 5% by 2020, says Iata, if at least 6% of aircraft fuel is from algae, jatropha or camelina, for example.

The body also estimates that improvements in operational practices, including reductions in the use of auxiliary power units, more efficient flight procedures and weight-saving measures, will achieve a 3% reduction in CO2 by 2020. Better air traffic management and airport infrastructure could provide an additional 4% cut by the end of the decade.

Despite these predicted improvements, Iata acknowledges that the airline industry will still have to offset 90 MtCO2 in 2025 to maintain emissions at 2020 levels and achieve carbon-neutral growth.

A new carbon standard for aircraft is set to be unveiled by Icao later this year. It will be underpinned by the “CO2 metric system”, a way of measuring an aircraft’s fuel-burn performance agreed by the Icao committee on aviation environmental protection in July 2012. The forthcoming standard will help to reduce carbon emissions from aircraft by encouraging the integration of fuel-efficient technologies into aircraft design and development, says Icao.

Technological fix

The Icao carbon standard should lead to further improvements in aircraft technology, although the industry has made significant technological advances since jet engines were first employed in commercial aircraft in the 1960s. Planes today are 75% quieter and use 70% less fuel on a passenger-kilometre basis than the earliest jet aircraft.

Existing technological “fixes” helping the aviation industry to lessen its environmental impacts include mounting winglets on the wingtips of aircraft to improve aerodynamics and reduce fuel burn, and replacing aluminium with composite materials to make planes lighter.

Clean Sky, a public–private partnership between the European Commission and the aerospace industry, was set up in 2008 to develop breakthrough technologies to significantly improve the environmental performances of aeroplanes and air transport. These include wing technologies, producing lighter aircraft, and innovation in engine technology and electrical systems.

Jeanne Yu, director of environmental performance at Boeing Commercial Airplanes, confirmed at a London workshop in November 2012 that the US aircraft manufacturer was planning to develop lighter aircraft by increasing its use of non-metallic composite materials. Boeing’s Dreamliner (787), for instance, is made primarily of carbon-fibre composite materials, and is 50% composite by weight.

Airbus too is producing lighter planes by using composites. Around 25% of its A380 – the world’s largest passenger aircraft seating up to 850 passengers – is made from composites, with the carbon-fibre centre wing box alone saving 1.5 tonnes of weight.

German airline Lufthansa has been reducing the weight of its planes as part of a fuel-efficiency strategy introduced in 2009. Dr Peter Schneckenleitner, head of political communication at Lufthansa, says that removing just 1kg in weight from each of its aircraft will save the airline 30 tonnes of aviation fuel a year. “We have more than 100 projects running to improve fuel efficiency, with many looking at reducing the weight of an aircraft,” he confirms.

So far, lightweight cargo containers have saved 14kg per unit, while the weight of some craft has been reduced by 230kg by removing fuel tanks that are not needed for certain flights.

Overall, modifications to the frames of planes – the fuselage, wings and undercarriage – will deliver reductions in emissions across the industry of up to 25%. The other major source for reducing emissions is engines.

Technological developments can cut direct carbon emissions from engines by as much as 20%. Meanwhile, improvements in engine emissions technologies are expected to deliver three-quarters of the 80% reduction in NOx emissions required by 2020; a target adopted in 2001 by Acare – the advisory council for aviation research and innovation in Europe. The remainder will come from burning less fuel as a result of improved engines, airframes and operations.

CFM International, a joint venture between GE Aviation and French firm Snecma, is developing a turbofan engine to enter service in 2016 that cuts fuel consumption by 15% compared with current engines. Rolls Royce, meanwhile, reports that the latest version of its Trent aero engine, due to be launched in 2014, will be 16% more fuel efficient that the first Trent, which came into service in 1996.

By 2025, a new generation of “open-rotor” engines is expected, which could offer a 25%–30% fuel efficiency improvement over existing engines.

Advances in technology are also helping reduce aircraft noise. The UK applies Icao’s “balanced approach to airport noise management”. This includes reducing noise at the source, which is mainly from engines, although airframe noise is increasingly important.

Yu’s colleague at Boeing, Sean Newsum, director of environmental strategy, says the Chicago-based company has done a lot of work on reducing noise. He told the London workshop that Boeing had used runway microphones to discover that much of the landing noise from a plane came from its anti-icing exhaust vents. A simple change in vent design vastly improved noise levels, says Newsum, who claimed that Boeing had reduced the departure noise of its aircraft at Heathrow airport by 90% since 1960.

Yu also explained that Boeing operates a “demonstrator” programme, which tests innovations on actual flights. In 2012, an “ecodemonstrator” flight tested a series of fuel-saving innovations, including adaptive trailing edges, advanced flight deck technology and a regenerative fuel cell.

Alternative energy

When BA’s “sustainable” jet fuel facility in east London is fully operational in 2015, it will be capable of turning 500,000 tonnes of waste each year into 50 tonnes of biofuel for the UK’s leading airline. The GreenSky London biofuel plant is a joint venture between BA and US bioenergy company Solena and will be the first of its kind in Europe.

The process of converting carbon-rich waste normally bound for landfill into sustainable biofuel for the aviation industry offers life cycle GHG savings of up to 95% compared with fossil-fuel derived kerosene, claims Solena.

Other airlines are also pursuing alternatives to conventional jet fuel as they seek to reduce carbon emissions. Like BA, Lufthansa is partnering with Solena to build a biofuel production facility in Germany. The plant will convert more than 520,000 tonnes of waste biomass into jet fuel, diesel fuel and electricity, using the same technology as the London facility. Schneckenleitner at Lufthansa describes the development of biofuels as a key strategy for the industry. “Only by using more biofuel can aviation achieve its 2020 and 2050 goals,” he says.

Since the certification of hydroprocessed esters and fatty acids (HEFA) fuels in the summer of 2011, 15 airlines have performed more than 1,400 commercial passenger flights with blends of up to 50% biojet fuel from used cooking oil, jatropha, camelina and algae, reports Iata. Lufthansa was the first to pilot biofuel on regular flights, when, between July and December 2011, one engine on an Airbus A321 operating between Hamburg and Frankfurt was powered by a 50-50 blend of regular fuel and biosynthetic kerosene. The six-month trial produced carbon savings of 1,500 tonnes, reports Lufthansa.

BA says the GreenSky plant will provide around 2% of its global fuel needs, while Etihad Airways has announced its commitment to replacing 10% of the jet fuel it uses with biofuel by 2017.

Competition for biomass feedstocks from other sectors, however, means that biofuels for use in aircraft are likely to make only a small dent in overall emissions from aviation. According to Iata, a 3% blend of sustainable, second-generation biojet worldwide each year would reduce carbon emissions from the industry by around 2%, or 10 MtCO2.

Operating systems

Changes to how aircraft operate in the air and on the ground are also part of the sector’s strategy to address environmental issues. Many planes spend too much time in the sky waiting to land or too much time on the ground waiting to take off.

Part of the answer to excessive time circling in the air or taxiing on the ground is to improve the air traffic management (ATM) process. Vijay Poonoosamy, head of government and international affairs at Etihad Airways, told a panel discussion at the 2011 aviation summit, hosted by Icao and the World Bank, that air traffic control was one of the low-hanging fruits the sector could pick to improve its environmental impacts.

Research by Airbus in 2012 found that 28 MtCO2 from aviation could be saved annually if ATM and onboard technology were optimised. Nats, the UK air traffic control service, estimates that aircraft circling before arrival accounts for roughly 2% of annual carbon emissions in its controlled airspace in the UK (and north Atlantic) – around 0.5 MtCO2.

The EU is pursuing its single European sky (SES) ATM system, under which 36 national air navigation services will merge into nine functional airspace blocks. Once a common air space across Europe is established, flights will be shorter and more efficient, reducing carbon emissions by around 50 MtCO2 annually.

Schneckenleitner at Lufthansa says that airlines are frustrated that progress on SES is so slow, with several member states missing the December 2012 deadline for implementing new rules. “Airlines in Europe cannot just fly from A to B; there are a lot of detours, which, on average add around 50km to every flight,” he explains. “If there are fewer detours this will save a lot of fuel, but the political will so far has been less than impressive.”

In the US, where flight paths are more direct than in Europe, the aviation authorities are pursuing the NextGen – next generation air transportation system – project, which includes measures to guide and track aircraft more precisely in the air and on the ground to save fuel, decrease emissions and manage the impact of noise on communities.

The project, which is being completed in stages, should enable aircraft to take even more direct routes and avoid delays caused by “stacking” as planes wait for an open runway. The Federal Aviation Authority claims NextGen will reduce aviation fuel consumption by more than 6,000 tonnes and cut emissions by 14 MtCO2 by 2018.

Nats is involved in several projects to improve the management of the flights it oversees. In 2009, Nats pledged to reduce CO2 emissions from each flight in its airspace by 10% by 2020. It aims to achieve this by improving the vertical profile of flights – adopting what it describes as a smooth, continuous climb and descent on take-off and landing – and by optimising cruising height, speed and route.

One project, called Topflight, which Nats is running as part of the SESAR programme (the technical and operational component of SES) seeks to optimise the journey of 60 transatlantic flights to minimise emissions and delay. It is expected that each optimal trip will save approximately 500kg of fuel – the equivalent to 1.6 tonnes of CO2.

“Topflight is an exciting opportunity to prove the perfect flight concept is scalable and sustainable in an operational environment. If successful, the trial could have a profound impact on the way the aviation industry works,” comments Patrick Ky, executive director at SESAR.

Topflight follows a 2010 trial, in which the ATM of a single BA Heathrow to Edinburgh flight was made “perfect”, saving one-quarter of a tonne of fuel and nearly one tonne of CO2.

Airlines are also reducing emissions through better maintenance. Lufthansa, for example, has established a new cleaning process whereby engines are cleaned more often to cut emissions. A one-year trial by the German airline delivered fuel savings of about 0.5% across its fleet – translating into 74,000 tonnes of carbon emissions not being released into the atmosphere.

Regulating the future?

Much of what the aviation industry is doing to combat its environmental impacts is voluntary. But if these prove unsuccessful, further regulation is likely to follow.

Regulations and standards to curtail noise and improve air quality near airports have been in place for many years. And, from the start of 2013, the European Commission took the first step in regulating emissions, with all aircraft departing or landing from EU airports included in the bloc’s emissions trading scheme (ETS).

A pledge by Icao to establish a global market-based mechanism to cap emissions this year resulted in the commission suspending, for the time being, the inclusion of flights to and from the EU in the ETS. However, if the Icao assembly in October 2013 fails to adopt a global framework EU enforcement will resume.

Schneckenleitner at Lufthansa believes that financial pressures will ensure the aviation industry continues to improve its environmental performance, particularly in reducing emissions. “Fuel is the industry’s main cost. Every kilo of fuel saved is not only good for the environment but good for the bottom line,” he says. “Economic and ecological savings go hand-in-hand.”

Schneckenleitner points out that Lufthansa has improved the fuel efficiency of its fleet by 30% over the past 20 years. He also says the German airline is investing €17 billion in modernising its fleet (it currently has 168 new aircraft on order), which will see further gains in fuel efficiency.

Ultimately, although the aviation industry can pursue a range of operational and technical options to reduce its GHG emissions and improve its environmental performance, these abatement measures will be submerged if the predicted growth in airline travel materialises.

By 2030, 50 million flights are expected to take place each year, roughly double the number in 2011. As the OECD points out, the predicted growth in flights and passenger miles in Asia alone will outpace the sector’s efforts to improve flight paths, create more efficient taxiing and increase planes’ fuel efficiency.


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