Much emphasis has been placed on the need for alternative powerplants and fuel sources, but Steve Bridgewater asks what the airline industry can do within the cabin to reduce its carbon footprint and overall effect on the environment

[This article first appeared in the November/ December 2021 issue of Airline Cabin Management]

In late 2021, the world’s attention was focused on Glasgow as the world’s leaders discussed the environment at the much-anticipated 26th Conference of the Parties (COP26) Climate Summit.

Perhaps surprisingly, the transport sector was not discussed until almost the last day, when a coalition was announced to put forward a declaration that encourages net zero carbon emissions globally from the air transport business by 2050.

Meanwhile, addressing the ‘Green Aviation Event’ – which took place in the City of London on 25 October and was co-organised by the Honourable Company of Air Pilots (HCAP) and the Worshipful Company of Scientific Instrument Makers (WCISM) – Robert Courts MP (UK Aviation Minister) pointed out that aviation was responsible for 5% of global emissions, but was getting more than 5% of attention. Noting that the world needed a sustainable and highly profitable aviation sector, he emphasised the desire for what he called ‘guilt-free’ flying: “Flying is not the problem; emissions are,” he said.

While much emphasis has been placed on the quest for alternative powerplants – be they electric, hybrid or hydrogen – and the development of Sustainable Aviation Fuel (SAF), there is much more that the air transport industry can do to both minimise its impact on the climate and win the hearts and minds of the eco-minded traveller.

Procedural Changes

Continuous descent approaches and continuous climb departures could each save approaching 1% on fuel burns, while single-engine taxiing could save over 2%. Even bigger savings could come from unimpeded taxiing, and using electric tugs to transport aircraft to the end of the runway could save a total of 15 minutes of engine running per departure. Building more stands at terminals to reduce delays would help further and it is estimated that these changes alone would amount to a 10% reduction in fuel burn. To put that into context, 1% of fuel use across Europe alone is the equivalent of two million tonnes of CO² emissions per year. Then there is the ethical question of whether ferrying aircraft halfway round the world to benefit from cheaper maintenance is justified.

Speaking at the Green Aviation Event, UK CAA Chairman Sir Stephen Hillier emphasised the importance of airspace modernisation, which he claimed could offer a rapid opportunity to reduce carbon. However, this would need to take into account the impact on noise, and would have to apply to all airports and routes equally. Looking further into the future, Professor Paul Robinson of Imperial College introduced the results of research which demonstrated potential drag reductions through the excitation of small-amplitude, high-frequency vibrations in aircraft skins. Such research is at an early stage, and he acknowledged that, as yet, there was no knowledge of any effects that such technology might have on, for instance, cabin noise.

Design Opportunities

Multiple airlines have announced programs to try to become more sustainable in the coming years. Delta recently committed $1 billion to become carbon neutral by 2030, while easyJet pledged to get there by 2035, JetBlue by 2040, and United Airlines by 2050. Older aircraft remain the least fuel efficient and Wizz Air UK – which operates a fleet with an average age of 5.08 years – estimates that if all other European airlines ran aircraft of a similar vintage, they would save 34% on their emissions.

During the event in the City of London, easyJet’s David Morgan produced a startling statistic regarding future fuels, claiming that 18 tonnes of kerosene would enable an Airbus A320 to fly from London to Dubai; 18 tonnes of battery would get the same aircraft to Dover; and 18 tonnes of hydrogen would get it all the way to Sydney, Australia – but the volume involved would be impossible to carry. 

If hydrogen is the saviour, it will require a complete redesign of new aircraft to carry the fuel in the mid-section – perhaps with passengers above/below/alongside in a blended wing concept. This need for new aircraft – however they are powered – in turn opens opportunities to radically change, modernise and improve the cabin environment. As discussed in our Future of First Class feature [Ed: see p38] some operators are already looking at ways to reconfigure interiors but the advent of entirely new concepts gives even greater scope for innovation and radical change.

In recent months, increasing emphasis has been placed on the ‘green’ cabin, with many airlines realising that small changes go a long way towards their carbon footprint and the regard in which their customers hold them. 

Supply chains are starting to take sustainability very seriously and many OEMs are demanding verifiable sustainability from suppliers and partners. For some years, business aviation giant Gulfstream Aerospace has mandated “environmentally conscious business practices” in its suppliers’ code of conduct and others are following suit. 

Sustainable materials and manufacturing processes found in Gulftream’s cabins, such as the use of renewable natural fibres like cotton and wool, are now becoming commonplace in airliners too. Likewise, many of the materials are recyclable. 

Chromium Free

Of course, the ecological effect of aircraft begins when it is manufactured and one of the ongoing problems that has plagued the industry for many years is the use of hexavalent chromium as a corrosion inhibitor or paint primer. This is harmful to the eyes, skin and respiratory system as well as a known carcinogen.

Coatings companies have therefore been trying to eliminate the compound and companies such as PPG Industries are looking towards organic alternatives using alkali earth or transition-metal compounds. Not only are these better for the environment, they are also potentially 30% lighter than standard chromated primers. Furthermore, they can be applied by either dipping or plasma electrolytic oxidation rather than spraying, thus reducing the amount of primer that is applied as well as removing the need for the use of harmful aerosols.

The drive for sustainability has already seen a number of ‘small’ changes, which add up to create a significant difference. Airlines’ drive for sustainability includes the reduction, re-use, and recycling of plastics used in packaging, swizzle sticks and drinking straws.

Singapore Airlines recently started working with US-based AeroFarms – the world’s largest indoor vertical farm – to deliver sustainable fresh produce “from farm to fork” on selected flights. The AeroFarms system is said to use 95% less water compared to field farming and 40% less than hydroponics. Grown indoors, without sunlight, soil or pesticides, the farming method is also more productive with leafy greens taking 14 days to reach maturity instead of the normal 30-45. According to AeroFarms this results in 390 times more productivity per square foot compared to traditional field farming.

In November, easyJet was presented with the Sustainability Award at the 2021 Professional Clothing Industry Association Worldwide Awards. This was in recognition of its new pilot and cabin crew uniforms, which are made by Tailored Image using fabric made from 100% recycled plastic bottles. With 45 bottles in each uniform, this will prevent 2,700,000 plastic bottles from ending up in landfill or in oceans over five years.

Fello’fly

Around a decade ago I attended an Airbus press conference where the manufacturer announced plans for fleets of aircraft flying in a ‘V’ formation “like flocks of geese” to save fuel. The concept was simple and followed the aerodynamic principle in which geese migrate in large groups, effectively ‘surfing’ on the wake of the birds ahead of them. At the time Airbus admitted that having flights departing at the same time would limit passenger flexibility. So, it came up with an innovative concept to make the proposal more appealing; each aircraft would be ‘themed.’ One, it proffered, would have a family friendly cabin, one might have a business suite, one could be dedicated towards sleep and relaxation and one could even be a flying casino.

Serendipitously, just as this article was being written ten years later, Airbus performed the first long-haul ‘fello’fly’ demonstration of such formation flying and the two A350s saved more than six tonnes of CO² emissions on a trip between Toulouse and Canada’s Montreal-Trudeau International Airport.

Airbus said the flight confirmed that by using specially developed flight control systems to stay in the wake updraft of the proceeding aircraft, fuel savings of more than 5% could be achieved without compromising safety.

The next step is to get the support of authorities so the new operational concept could be certified – but Airbus says this wake-energy retrieval has the potential to reduce CO² emissions by between 3 and 4 million tons per year.

If the fello’fly concept proceeds as planned it could revolutionise the aircraft cabin, negating the need for zones within individual aircraft and allowing entire cabins to be designed for specific needs.

Technological Advances

Among the innovations unveiled at November’s Dubai Airshow was Lufthansa Technik AG’s Explorer VIP cabin concept. It is aimed at the super-wealthy owner/operator but the most striking element of the proposal could easily be adapted by airlines choosing to theme aircraft for fello’fly use.

The Explorer’s cabin features the large-scale projection system for virtual content, which can turn the cabin into anything from a disco to a virtual aquarium. Although similar features have been seen in other Lufthansa Technik design studies, the company has now found a way to implement them in a way that is certifiable. Working with Diehl Aerospace, Diehl Aviation and Thales it has developed lightweight passively cooled projectors which can be integrated into cabin walls and ceiling.

Increasing use of ‘intelligent’ technologies is opening up opportunities to streamline the cockpit and the cabin. Integrated platforms work together to both improve operational efficiencies and significantly reduce the amount of wiring required for the cabin, galley, and flight deck. New materials could also help airlines ‘go green’ and researchers are investigating new composites and coatings that are lighter, thinner, less toxic and more environmentally friendly than those already in use.

Using composites instead of traditional aluminium to manufacture aircraft components has helped reduce the overall weight of aircraft such as the Boeing 787 and Airbus A350 by around 20%. Now, research is being undertaken at the University of Alabama to enable carbon fibre composites to be embedded with nanoparticles and enable them to be cheaply and quickly produced by 3D printing. The latter would reduce material loss because parts can be produced in the exact size and shape needed instead of being cut out from a larger piece of material, as is done with aluminium.

Whereas metal aircraft conduct electricity in the event of a lightning strike (the current passing directly through them with little or no damage) composites are not conductive and can be severely damaged. Manufacturers bond a copper mesh within the carbon to conduct the electricity.

To improve conductivity and allow aircraft to dispense with the heavy copper layer, scientists are developing reinforced composites with nanographene or carbon nanotubes, and conductive polymers.

Thinking Differently

The UK Digital Cabin (digitalcabin.aero) project by aerospace trade association ADS includes a number of companies which are developing green technologies.

Cecence, an award-winning composite solutions company, specialises in lightweight FST compliant sustainable structural components for aero interiors.

The company has a purpose-driven agenda to innovation in lightweight aero interiors using recycled carbon, natural fibres and bio-based resin systems.  

Composite materials provide weight savings and durability without compromising on strength but often rely on materials which require a huge amount of energy to produce. Natural fibres such as hemp sequester CO² in their growth. By combining these with a bio‑resin, Cecence is able to produce net zero products that make a positive contribution from the very beginning of the product’s life. Cecence’s latest sustainable seat back provides a global warming potential (GWP) reduction of 84% compared to more traditional composite materials. 

STG Aerospace specialise in emergency exit and cabin lighting systems. Its lighting products provide either no power or low power lighting. Its saf-Tglo emergency exit systems are self-charging, requiring no power, while its cabin lighting systems are designed for low power. Brand marketing manager Kate Williams says: “There is increasing expectation that every business should operate as sustainably as possible and prioritise social value with the same rigor as economic value. STG fully embraces that challenge.”

Meanwhile, Airtek offers an all-composite seat which is lighter and helps drive down weight and emissions. It combines high end cabin design with motorsport-derived engineering and certification and uses a patented monocoque structure which results in a reduced need for much of the traditional metallic under seat support structure. This reduces weight and, in turn, aircraft fuel burn and associated carbon emissions. It also offers the largest volume of under seat storage space of any business class seat in the market.

ADS represents and supports more than 1100 UK businesses operating in the aerospace, defence, security and space sectors and its Digital Cabin initiative is a new route to market for aircraft interiors SMEs. Using 3D Web-GL technology, it has created a virtual aircraft cabin where aircraft interiors companies can showcase their products and services to a global audience in a new and immersive way.

In recent years the aviation world has become a very visual target for climate change protestors. It is worth remembering that although the industry contributes a relatively small amount of carbon this is contrary to popular public perception. Therefore, anything the aviation world can do to win the hearts and minds of the eco-conscious traveller is a benefit. 

There is no doubt that airlines will have to continue using kerosene for some time to come, so it must become more efficient, burn less carbon per customer and do all it can to play its part in slowing climate change.

In the words of the Lord Mayor of the City of London, speaking at the Green Aviation Event: “Aviation needs to go green or go home – and if it doesn’t go green we won’t have a home to go to.”