Amid steady growth in air traffic and related polluting emissions, the aerospace industry is rolling up its sleeves to ensure that the sector grows in a carbon-neutral manner as of 2020.


Greening air transport means developing cleaner technologies and new flight management systems to reduce the environmental impact of aviation. The EU objective is to halve, by 2020, carbon dioxide (CO2) emissions and perceived noise pollution, and reduce nitrogen oxide (NOx) emissions by 80% from 2000 levels.

The EU targets stem from the work of the Advisory Council for Aeronautics Research in Europe (ACAREexternal), a European technology platform established in 2001. ACARE brings together key industrial, research and policy stakeholders to define Strategic Research Agendas (SRAs) identifying the challenges, concepts and technologies that the sector has to work on to become more sustainable.

The European Clean Skyexternal Joint Technology Initiative (JTI) was launched in February 2008 to develop the technologies needed to meet the objectives set by ACARE. 

The €1.6bn 'Clean Sky' programme will be financed equally with EU and industry money. It will focus on six specific projects, including designing greener engines, adapting wing technologies to make new aircraft more energy efficient and developing lighter materials. 

In parallel, SESAR, another large Joint Undertaking, aims to modernise the European air traffic management (ATM) infrastructure to allow airlines to fly more direct routes and reduce fuel consumption and related emissions by over 10% by improving flight efficiency (see EurActiv LinksDossier on the 'Single European Sky').


There are no legally binding targets to reduce CO2 emissions from aviation. But both political concerns over climate change and simple economics (reducing fuel cost to increase profit) are pushing the industry to seek more fuel-efficient ways of flying.

As fuel can represent up to 50% of airlines' costs, pressure is mounting to reduce consumption by improving technology and managing airspace more efficiently.  

Concern over the security of supplies of oil-based kerosene is also a key driver of the search for alternative fuels.

Political trade-offs

While climate change and the subsequent need to reduce fuel consumption and CO2 emissions are of paramount importance, the drive to 'green' the aviation sector has some trade-offs, which need to be acknowledged and politically prioritised. 

For example, reducing noise may mean that you need to increase fuel consumption and thus CO2 emissions, or vice-versa. 

Another example of the trade-off issue is so-called 'open rotor' technology, which provides a step-change - a 15-20% reduction - in fuel consumption. But such engines are far noisier than current turbo jets. 

In addition, safety is of paramount importance to the aviation sector and cannot be compromised by environmental considerations. 

Carbon-neutral growth as of 2020

Civil aviation was responsible for around 2% of all man-made CO2 emissions in 2008, whereas commercial aviation accounts for around 12% of the CO2 produced by the transport sector, according to the International Air Transport Association (IATA).

Despite the current economic situation, air transport remains a growth market. Air traffic is expected to double or even triple by 2020 worldwide and there is widespread agreement that major technological improvements are needed to allow cleaner growth of the global aviation sector. 

The EU's research objectives to improve the environmental performance of Europe's aeronautics industry include reducing CO2 emissions and noise by 50% from 2000 levels and nitrogen oxide (NOx) emissions by 80% by 2020. The 'Clean Sky' public-private partnership was recently launched to develop and validate the technologies needed to meet these targets.

At global level, international airline associations, airports, air navigation service providers and manufacturers are committedPdfexternal to improving fuel efficiency by an average of 1.5% per year until 2020. The objective is to achieve carbon-neutral growth from 2020, and halve overall emissions by 2050 (compared to 2005 levels). 

Research challenges

The establishment of the Single European Sky and a single air traffic management system is expected to reduce the length of flights and related emissions. However, much of the potential to 'green' the sector lies with the aeroplanes themselves and requires action from the aerospace industry. 

After years of taking a back seat to noise concerns, aircraft engine emissions are now on top of the environmental agenda for aviation. The amount of CO2 produced by an aircraft engine is directly related to the amount of fuel burned in that engine. Therefore, the main driver of research into greening air travel is the desire to reduce consumption of jet fuel, whether through the development of more efficient engines and lighter materials or operating flights more efficiently.

Another possibility is to develop alternative fuels that emit less CO2, such as algae oil and fuel from biomass or natural gas.

  • Engine design 

One of the main research and development (R&D) priorities is to design aeroplane engines that are more fuel efficient. Improving the fuel efficiency of engines would reduce harmful emissions produced during combustion in an engine. These include NOx, which affects local air quality, and CO2, which is believed to contribute to climate change.

The amount of CO2 produced by an aircraft engine is directly related to the amount of fuel (kerosene) burnt in the engine, while the impact of NOx emissions varies significantly across the flight cycle. The greatest amounts are generated during take-off.

A recent International Council on Clean Transportation (ICCT) reportPdfexternal on efficiency trends for new commercial jet aircraft from 1960 to 2008 finds that on average, the fuel efficiency of new aircraft has doubled since 1960. However, the report notes that most of the gains were reached in the 1960s and 1980s, revealing that the rate of improvement has been falling after 1990. 

The paper suggests that rising fuel costs alone have not been sufficient to improve aircraft efficiency. Instead, efficiency improvements tend to come with new aircraft designs, but development has slowed considerably. 

In addition, water vapour (H2O) emitted from aircraft engines can form contrails (condensation or vapour trails) and cirrus clouds. Cirrus clouds trap and reflect infrared radiation (heat) underneath them, contributing to the greenhouse effect. But they also reflect sunlight to some extent, and scientists are yet to determine whether the net effect of cirrus clouds is to warm or cool the earth. 

Companies such as Airbus, Boeing, Rolls-Royce and United Technologies (UTC) are competing to develop the greenest engines and other products that can slash fuel consumption.

  • Alternative fuels

While kerosene is expected to remain the dominant aviation fuel in the near term, development of a range of alternative fuels for aviation is well underway and some certified kerosene-type fuels already exist.

Synthetic kerosene (XTL), FAMEs (Fatty Acid Methyl Esters), hydrogenated oils, liquid hydrogen, methane and ethanol/methanol are considered as potential alternatives. There is also interest in natural gas.

However, some alternative fuels, such as fuel derived from coal, can have an even higher carbon intensity than oil-based kerosene.

Whatever the alternative, it would need to be a 'drop-in' replacement for kerosene that is compatible with existing aircraft and fuel storage systems. If the fuel were 100% mixable with kerosene, existing engines and fuel systems would not need to be modified and the fuel could be introduced across the world from day one.

Using hydrogen and methane-based fuels, however, would require changes to airframes (bigger fuel tanks) and engines, as well as a modified global distribution infrastructure.

Meanwhile, 'drop-in' kerosene biofuels are gaining momentum and the first biofuels for aviation are expected to be certified soon. Two next-generation biofuels produced from jatropha and camelina (oil plants), for example, have already been demonstrated successfully as jet fuels both on the ground and in the air. 

The biggest challenge is scaling up biofuel production so that fuel can be produced in the quantity requiredwithout harming the environment (see EurActiv LinksDossier on 'Biofuels for Transport').

EU Clean Sky JTI

The EU's 'Clean Sky JTI' (Joint Technology Initiative) is a €1.6bn public-private research programme, the financing of which is split 50-50 between the Commission and the industry. The seven-year research programme is expected to provide the manufacturing industry with the financial incentives required to deliver and validate breakthrough technologies for the next generation of environmentally-friendly aircraft by 2020.

The programme consists of six integrated technology demonstrators that are expected to deliver:

The environmental performance of the technologies developed will be assessed in a simulation networkexternal

The programme was set up in 2006. But it suffered serious delays and the first call for proposals was only launched in summer 2009 (EurActiv 17/04/09). 

Towards CO2 standards for aircraft? 

At present there are no standards governing the CO2 emissions of aircraft like those in existence for cars, for example. 

The International Civil Aviation Organisation's (ICAO) Committee on Aviation Environmental Protection (CAEP) initially resisted the idea back in 2001, but concerns about the growing climate impact of the aviation industry have put the issue back on the table.

CAEP is currently working to draw up standards which would impose an emissions cap on new aircraft designs. The standards could be adopted by 2013.


The EU hopes that its Clean Sky Joint Technology Initiative (JTI) will help European aircraft manufacturers to compete in the race to build the world's cleanest planes. "The future expansion of aeronautics relies on its ability to reduce its environmental impact. Vast resources are needed and neither the EU, nor industry, nor scientists could achieve this on their own," said former EU Research Commissioner Janez Potočnik.

Alain Garcia, chairman of the integration team at ACARE, the Advisory Council for Aeronautics Research in Europe, noted that current levels of research funding, both from national governments and the EU, fall considerably short of what is needed to tackle aviation emissions. More than €100 billion is required for the period 2000-2020 in order to ramp up clean investment in the sector, he said.

'Clean Sky' executive director Eric Dautriat believes the initiative can realistically be expected to deliver between 20% and 40% reductions in carbon emissions and noise pollution, depending on the type of aircraft concerned.

"Clean Sky is the operational arm for delivering the goals set by ACARE [to reduce carbon emissions and noise by 50% and nitrogen oxides by 80% by 2020 compared to 2000 levels] and will allow us, if not to reach these ambitious figures, to at least make some very essential steps forward," Dautriat said.

Marc Ventre, chairman of the Clean Sky JTI governing board and executive vice-president in charge of aerospace propulsion at French group Safran said in autumn 2009 that technical work on Clean Sky was well underway. "One year from now, we will have to make major technological choices, which will influence what tomorrow's aircraft look like."

"In five to seven years, there will be an impressive series of large-scale flight and ground demonstrations spanning the whole range of civil aircraft – mainline and regional aeroplanes, helicopters, business jets – along with their engines and systems," Ventre said. 

Michel Laroche, chairman of the AeroSpace and Defence Industries Association of Europe's (ASD) research and technology commission and executive vice-president of research and technology at Safran, noted that funding under the EU's Research Framework Programme represents "a rather low proportion of the overall budget" dedicated to the aerospace sector, with the vast majority of funding coming from national programmes and private investment. 

Laroche also argues that while the aerospace sector has adopted market-driven research, the EU's Research Framework Programme is "clearly more adapted to a curiosity-driven type of research".

He said the European Commission's complex legal requirements, set up to minimise legal risks, are undermining efficient implementation of the research programme and holding back Europe's efforts to meet ACARE's goals.  

Kevin Morris, environment and sustainability manager at A|D|S, the trade organisation for advancing the UK's aerospace, defence and security industries, stressed that special attention should be paid to long-term priorities in greening air travel, as planes are very expensive and airlines need to keep passenger aircraft in service for 25-30 years to get returns on their investment.

"We need to ask whether the focus on what is the most important [environmental] issue today will still be considered the most important in 10 and 20 years time as well," he said.

Morris noted that drop-in kerosene biofuels were thought to be "pure imagination" two to three years ago, while now they are a reality. "It is likely that biofuels will be certified sometime this year [2010]," he predicted.

However, he stressed that fuel is always going to cost money and that biofuels may cost more than oil-based kerosene. The cost of biofuels will depend on start-up and running costs and prices may not come down until the technology has matured and biofuel plants are up and running, he warned. He could not tell, however, "whether the prices will ever come down to the level of oil-based kerosene".  

Philippe de Saint Aulaire, head of environmental affairs at the AeroSpace and Defence industries Association of Europe (ASD) and director of environmental affairs at the International Coordinating Council of Aerospace Industries Associations (ICCAIA), stressed the importance of addressing the environmental issues facing the aviation sector at global level.

He said aviation needs to be considered as a global sector, because otherwise it will be much more difficult to find solutions which do not create competitive distortions.

Regarding potential future CO2 standards for aircraft, de Saint Aulaire emphasised that manufacturers are already striving to construct the most fuel-efficient aircraft as their customers (airlines) are always looking for the most fuel-efficient planes to decrease costs.

Giovanni Bisignani, director-general and CEO of the International Air Transport Association (IATA), which represents the airline industry, stressed that "our message to governments at ICAO is simple. We need a global sectoral approach to reducing aviation emissions. And governments should incorporate our industry targets as part of their solution".

A global sectoral approach would mean that governments must account for aviation emissions at a global level and as an industrial sector, rather than within national targets, Bisignani argued. "This would ensure that airlines pay for their climate cost just once, not several times over, and it would drive emissions reductions with global standards on a level playing field," he said. 

A recent study by the International Council on Clean Transportation (ICCT), which brings together regulators and experts from China, the EU, France, Germany and the US, noted that the pace of improvements in aircraft energy efficiency is very slow, and no progress has been made in the last decade.

It argued that emission reductions would mainly come from the introduction CO2 standards which would apply not only to new designs but also to newly-built aircraft from current production lines.

Daniel Rutherford, co-author of the ICCT's report, argues that if current designs are not subjected to the future CO2 standard, improvements will happen far too slowly. "Conventional wisdom holds that fuel prices drive constant improvements in new aircraft efficiency, but our analysis suggests efficiency improvements only tend to come with the introduction of new designs, which are much less common today," he said. 

Applying a carbon dioxide standard only to new production lines, as the UN's ICAO has proposed (see below), could actually prove counter-productive by encouraging manufacturers to delay the introduction of more efficient designs in favour of older, unregulated models, the ICCT fears.

Meanwhile, the International Civil Aviation Organisation (ICAO), a UN body, is proposing a CO2 standard for new aircraft designs only - rejecting suggestions that designs currently in production should be subjected to a maximum level of emissions. 

In a separate development, the head of low-fare airline EasyJet, Andy Harrison, has accused airframe makers of delaying the delivery of cleaner, more fuel-efficient planes "because the cash flow they have from the Boeing 737 and Airbus 320 narrow-bodied planes is what they are interested in, and they want to keep that going". 

Ahead of the December 2009 climate talks in Copenhagen, an industry group bringing together the Airports Council International (ACI), the Civil Air Navigation Services Organisation (CANSO), the International Air Transport Association (IATA) and the International Coordinating Council of Aerospace Industries Associations (ICCAIA) called on governments to "give their full backing and explicitly state their support for ICAO as the appropriate United Nations body for setting and administering aviation-specific standards and targets to address CO2 emissions from aviation".

Their worry is that a disparate regulatory system will be adopted in several regions or countries, raising compliance costs and hurting the global industry.


  • Oct 2001: Establishment of the Advisory Council for Aeronautics Research in Europe (ACAREexternal).
  • 2002 and 2004: ACARE publishes Strategic Research Agendas (SRAs).
  • 2008: Addendum to the ACARE SRA.
  • 2008: Clean Sky JTI launched.  
  • 1 April 2009: 4th Aviation & Environment summitexternal(summit communiquéPdfexternal). 
  • 15 Dec. 2009: Clean Sky JTI information day (see presentationsexternal).
  • 1-12 Feb. 2010: ICAO Committee on Aviation Environmental Protection (CAEP) meeting to discuss work on aircraft CO2 standards and fix a date for its potential adoption.
  • 23 Feb. 2010: Deadline for the Clean Sky JTI second call for proposalsexternal.
  • 11-14 May 2010: ICAO colloquium on aviation and climate change.
  • 16-17 Sept. 2010: Aviation & Envrionment summit 2010 in Geneva (read the summit communiqué).
  • Oct. 2010: ICAO to consolidate the sector's green target and present a roadmap.
  • 2010-2012: Full review of the ACARE SRA.
  • 2010-2013: ICAO hopes to adopt a CO2 standard within the next Committee on Aviation Environmental Protection (CAEP) tri-annual cycle.
  • 28 March 2011: Commission White Paper on Transport.
  • 30 March - 1 April 2011: Sixth European Aeronautics Days with focus on sustainable aviation.
  • June 2011: Paris Air Show 2011 with focus on biofuel-powered planes.
  • 1 Jan. 2012: Target date for including aviation in the EU's Emissions Trading Scheme.
  • By 2015: Clean Sky expected to test and validate new technologies.
  • By 2020: Industry target to reduce carbon emissions and noise by 50% and cut nitrogen oxides by 80% compared to 2000 levels.