Like virtually every area of human activity, air transport has an impact on the environment.

This impact takes several forms, including the disturbance caused by aircraft noise and aircraft engine emissions. A major concern for the industry is greenhouse gas emissions from aviation and their implication for climate change.

CO2 is not the only emission from aviation. The exhaust from aircraft engines is made up of CO2 and water vapour (7- 8%), nitrogen oxides (0.5%), unburned hydrocarbons, carbon monoxide and sulphur oxides, traces of hydroxyl family and nitrogen compounds and small amounts of soot particles. According to the Air Transport Action Group, 92% of aircraft engine exhaust is normal atmospheric oxygen and nitrogen.

Boeing has forecast that the world’s fleet will double over the next 20 years, with passenger and cargo traffic each to grow 5% per year. As a result, the aviation industry’s current carbon footprint is bound to increase.

However, a growing carbon footprint is unacceptable to both the industry and consumers. This is reflected in a poll carried out by Airbus on passenger expectations, in which 86% of respondents voted for the use of less fuel and the release of fewer carbon emissions. The idea of aircraft powered by non-fossil fuels, such as biofuels, appealed to 78%, while quieter aircraft appealed to 66%.

The fact is that aviation has been improving its environmental performance consistently for the last 50 years; greater efficiency directly benefits the profitability of business as well as the environment.

From the moment aircraft are designed, engineers are working out how to make them more efficient. Aircraft manufactures are focused on reducing fuel consumption – and operating costs in general – in the battle to win orders from airlines.

Fuel costs, which can account for 50% of an airline’s operating costs, can make or break an airline. New technologies on the horizon have the potential to decrease greenhouse gas emissions from aviation significantly, and solutions that are being implemented today also promise other savings. Consequently, the quest for further efficiency continues on a number of fronts.

Inspired by nature

Improving the efficiency of aircraft to reduce the level of emissions per passenger (or over the distance flown) is a focal point for technological innovation. Nature has long inspired mankind and birds inspired the modern day plane – so it’s no surprise that engineers have looked to the flight of birds for further inspiration.

Movable wing surfaces In the same way that sea birds sense gust loads in the air with their beaks and react by adjusting the shape of their wing feathers to suppress lift, probes in the nose of the new Airbus A350XWB detect gusts ahead of the wing and deploy movable surfaces for more efficient flight. This helps reduce fuel burn and, therefore, emissions.

Eagle-inspired winglets If the wings of large birds of prey were too long, their turning circle would be too big to fit inside the rising columns of warm air which they use to soar. The eagle’s wings perfectly balance maximum lift with minimum length by curling feathers up at the tips until they are almost vertical.

Thanks to small devices known as ‘winglets,’ which mimic the upward curl of the eagle’s feathers, 3-5% reductions in fuel burn have been achieved.

This principle plays a major part in the design of the A380. If this aircraft had been built to a conventional design, the plane’s wingspan would have been three metres too long for the world’s airports.

The A380’s wings are 20cm inside airport limits, but still provide enough lift for the world’s largest passenger aircraft to fly efficiently – saving fuel, lowering emissions and reducing airport congestion.

While it is no surprise that more and more aeronautical innovations are inspired by birds, designers are looking at a greater array of natural structures, organs and materials – and these tried and tested patterns of the natural world will continue to be a powerful source of inspiration in the future.

Lotus The surface of a lotus leaf has evolved to keep it clean and dry by causing rainwater to roll off and take any dirt with it.

Known as the ‘lotus effect’, these properties have inspired coatings for cabin fittings, which shed water in beads and take contaminants with them. This improves hygiene and reduces the volume of water needed.

This in turn reduces the weight of the aircraft and, therefore, the fuel burn and carbon emissions as well. This innovation is already used on the surfaces of Airbus cabin bathrooms, and in the future will be found on the fabric of seats and carpets. There are even plans to use the lotus technique on the outside of the aircraft.

‘Groovy’ shark skin Just as the shark swims effortlessly through the water, so soon will aeroplanes fly through the sky. Scientists have found the skin of a shark is covered by microscopic grooves that actually reduce their drag through the water, therefore allowing the shark to conserve energy as it searches for food.

For over 30 years this ‘groovy skin’ concept has been investigated and tested by aerospace engineers, and is finally being adapted and applied to the construction of aircraft. Just as a shark can minimise the energy it expends in motion, these microscopic grooves can help to reduce the fuel burnt by a jet aircraft.

Butterfly Wings Butterflies have long been a symbol of transformation, so it’s fitting that their wings are a focus of aircraft engineers. While they are some of the most beautiful and delicate creatures on the planet, their wings are fantastically intricate mechanisms, designed to achieve optimum efficiency in flight.

Researchers are looking to harness the butterfly’s ability to twist and turn wings in flight. There’s a future possibility of using small movable surfaces and active internal structural components as part of an aircraft wing, to mimic the way micro-capillaries in a butterfly’s wing make for more efficient flight.

Getting lighter…

Lots of people look to lose weight to improve their performance; the same is true in the battle for efficiency. Reducing the weight on the plane will mean it uses less fuel. Boeing says that its 787 Dreamliner will cut fuel use by 20% thanks to new engines and the use of lightweight, composite materials.

Meanwhile, EADS says that the A380 is the first long-haul aircraft to consume less than three litres of fuel per passenger over 100 km, a rate comparable with an economical family car.

It claims that the A380’s efficiency and advanced technology result in 15–20% lower seat-mile costs than those of competing aircraft. Fuel-efficient engines and the use of advanced composite materials have played a vital role in reducing the A380’s operating costs.

The airframe is made up of some 25% composite material by weight, while the Airbus A350XWB, which entered production in 2010, utilises around 50% composite material.

Air traffic management systems reduce the amount of fuel wasted through inefficient routing and flight patterns. It is a fact of modern aviation that the route from A to B is not always as direct as it could be, so modern day systems are now being designed to plan more efficient routes.

Carbon-neutral growth and the future

The aviation industry has set three global commitments for reducing its emissions.

From now until 2020, it has committed to a 1.5% improvement in efficiency per year. The industry is using a four-pillar strategy to further increase its fuel efficiency by a further 17% over the coming decade. One of the most important parts of that strategy is the introduction of new technology – the biggest impact of which comes through the replacement of older aircraft in the fleet with newer, more efficient planes. This is not cheap. To keep to the 1.5% fleet efficiency improvement target, the world’s airlines will need to purchase around 12,000 new aircraft by 2020, at an estimated cost of $1.3 trillion.

While emissions will continue to grow until 2020, the aviation sector has agreed to cap its net emissions at the 2020 level. From this point on, any emissions the aviation industry is unable to reduce through operational, technological or infrastructure measures, or by using biofuels, will need to be offset by market-based measures.

After 2020, the industry will start seeing some of the large emission reduction efforts made possible by advancements. By this time, sustainable biofuels will be well established and the necessary supply chain will begin to deliver large volumes of low-carbon fuel to the airlines.

These two major factors, as well as continuing work on infrastructure and operations efficiency, will allow the industry to aim for its most ambitious goal: to ensure that net carbon emissions from aviation in 2050 will be half of what they were in 2005, or 318.5 million tonnes.

Sammuel Yisrael IEng MIET is an aerospace expert from Test and Measure Automation Experts, and has worked on some of the most high profile projects within Aerospace.