Insects may not seem the most obvious problem to tackle when trying to make aviation more sustainable. But avoiding them on takeoff could help cut airlines’ fuel bills and emissions by up to 10%.
It’s already an idea that NASA has explored. Last year it tested hi-tech coatings to make dead insects slide off wings, with one design delivering a 40% reduction in insect residue.
This is just one of many attempts to meet the huge challenge of making aviation more sustainable. The sector accounts for 2% of all man-made CO2 emissions, and a recent European parliament report estimated that if climate change ambition levels don’t rise, aviation emissions could make up 22% of global emissions (pdf) by 2050.
Progress has been made though. Small, steady annual advances in fuel efficiency mean that a modern Boeing 737 burns only around half as much fuel per passenger as the first 737 did in 1967. Winglets have reduced fuel consumption by around 4%, carbon brakes save hundreds of kilos per aircraft, efficient turbofan engines produce more thrust from less fuel, economy seats are stronger and lighter, and checking an aircraft for chipped or scratched paint can reduce its fuel bill by 0.5% (pdf).
There are plenty more of these tweaks in the technology pipeline. Nasa’s project also demonstrated lightweight wing flaps that morphed shape and a new tailfin design that promises to cut fuel usage by another 0.5%.
Planes can be flown smarter too. A smooth, continuous descent can save 40% of the fuel burned during an aircraft’s final approach, while smarter air traffic control in Europe and the US – including more efficient takeoff and landing, more direct routes and less circling – could save tens of millions of tonnes of CO2 over the next decade.
Meanwhile, on the ground, EasyJet is about to trial a hydrogen fuel-cell system to reduce emissions during taxiing, which consumes around 4% of the airline’s entire fuel budget.
But these incremental improvements pale in comparison to the challenges, especially given the industry’s growth. Over the past decade, aviation revenues have doubled, from $379bn (£270bn) in 2004 to $727bn in 2015, thanks in large part to an increase in low-cost travel.
Aviation was not included in the Paris climate agreement and has traditionally been seen as hard to regulate; international disagreements on emissions standards have also stymied progress. However, last month 23 countries, including the US and UK, agreed the first global standards to cut commercial aircraft emissions in future planes, to be achieved through innovation in aircraft design and fuel-efficient technologies.
Putting aviation on a more sustainable footing is an enormous challenge, according to Steven Barrett, director of the Laboratory for Aviation and the Environment at MIT. “Not least because the technological lifecycle for aviation isn’t far off a century,” he said. “The 747 was designed in the 1960s and the latest version, the 747-8, will be in service until the 2050s or 2060s. Something developed today can take 30 years to penetrate the fleet because old aircraft are only retired when they become uneconomic.”
A few years ago, it was expected that second-generation biofuels, made from plants that did not replace food crops, would help fill much of the gap. But the crash in the price of fossil fuels and continued difficulties in finding and producing sustainable biofuel feedstock plants has tarnished their appeal.
New wing shapes are another option. By bracing wings with struts or turning the entire plane into a giant wing – a hybrid or blended wing body – an aircraft can generate more lift and have superior fuel economy. Nasa wants to build experimental X-planes within the next 10 years, although questions remain about how to regulate such innovative designs and whether passengers will like them.
Another possibility is for air travel to go electric. Airbus has demonstrated a two-seater called the E-Fan, which can remain aloft for an hour, and is now pushing small all-electric and hybrid planes into production. And Nasa is working towards an experimental nine-passenger electric aircraft that has dozens of small propeller engines spaced out along the length of its wing, a configuration that promises a smooth, quiet and efficient ride.
Nasa hopes to have the plane, called Sceptor (scalable convergent electric propulsion technology), flying by 2019. It will have lithium-ion batteries and a 500kW power plant. Tesla chief executive Elon Musk has hinted that he might be interested in designing a vertical takeoff and landing electric jet.“There is a chance that electric planes could be viable for short-range flights, maybe a city centre to city centre flight of about an hour,” said Barrett.
Hybrid electric planes could even recover energy when descending to recharge their batteries, like regenerative braking in electric cars.
But to really save money and emissions, you need to slow down. Astro Teller, the captain of moonshots at Google, revealed earlier this month that the technology giant had been working on a lighter-than-air, variable-buoyancy cargo airship: “This could get the cost of shipping closer to boats than planes, get the carbon footprint of moving cargo lower than for boats, and get speeds of transport halfway between boats and planes – all without needing runways,” he wrote.
However, Google calculated the cost of a building an initial prototype at close to $200m (£144m). “[This is] way too expensive for us to get the first data point on whether we’re on the right track,” said Teller.
While that might sound a lot, Boeing invested around $32bn to develop the 787 Dreamliner and airlines in the US spend an estimated $50bn annually on jet fuel.