Can the notoriously damaging airplane industry be less destructive to the environment? 413 looks at four news ways of radically rethinking air travel, and asks if it can ever be a sustainable option
When the Icelandic volcano Eyjafjallajökull erupted in the spring of 2010, carbon-rich volcanic ash spewed into the atmosphere. Black dust rained across Northern Europe for weeks. But despite the ash cloud, the eruption did something you might not expect: It also, for a time, fought global warming. By cancelling more than 100,000 commercial flights, Eyjafjallajökull is estimated to have saved 2.8 million tonnes of carbon dioxide emissions – far more than the amount it billowed into the sky.
If you’re a frequent flyer, you perhaps already suffer from flygskam–the Swedish phrase for ‘flightshame’. Even so, it’s worth appreciating the scale of aviation’s emissions problem: Worldwide, flying emitted 918 million tonnes of CO2 in 2018. Or to put it another way, each passenger on a return flight from London to New York is responsible for the same amount of greenhouse gas emissions as the average uk household emits in an entire year, melting 6.6m2 of Arctic ice in the process. (Multiply that almost threefold if you’re flying business class.)
Aviation’s climate impacts are also growing rapidly. Between 2007 and 2017, the total number of people flying worldwide increased from 2.2 billion to 4 billion a year, and aviation- related emissions are expected to grow fivefold by 2050. (Despite flygskam, global passenger numbers still grew 3.3 per cent last year.)
To try and bring flying’s environmental cost under control, the aviation industry is having to rethink what flying might mean in the future. “There’s a tremendous focus on making aeroplanes more sustainable,” says Roelof Vos, an assistant professor of aerospace engineering at Delft University of Technology, which works on innovative aeroplane designs. The problem, Vos explains, is that “efficiency gains in current aircraft design have plateaued somewhat. The low hanging fruit has all been picked.” This means more radical measures will need to be taken. Here are four potential ways to reduce the damage.
MAKING FUEL FROM WASTE
The easiest way to reduce carbon emissions is to burn less fossil fuel. Biofuels – the term for any fuel that is made from biomass, rather than fossil fuels extracted from the ground – are well known in aviation. Many airports, including Oslo, Los Angeles and Stockholm, already offer it mixed it into their jet fuel. (Even older jets can use a 50/50 biofuel-jet fuel mix; any more biofuel, however, requires new, specially designed engines.)
The impacts of biofuel, however, are varied. Advocates say that biofuel emits just over half the amount of co2 as regular fossil fuels (39 grams of co2 per joule, versus oil’s 75.1 grams). But in truth, it’s not that simple, because that rarely factors in how the biofuel is produced. According to some studies, biofuel made with plant oil – which is produced on heavily deforested and polluted plantations – is actually three times worse for the environment than fossil fuels, and only 0.1 per cent of flights globally are currently powered by biofuels; salvation is a long way off.
Hope might come from an unlikely source: your dustbin. In 2019, chemical engineers at University College London won a grant from British Airways to develop biofuels from common household waste. The engineers estimate the technique, which uses gasification to turn the waste into kerosene, could provide one-third of the uk’s biofuel, and eliminate the need for deforestation. “The carbon emission reduction is massive – it’s 90 per cent less than fossil fuels, but also 60 per cent less than other biofuels,” says Massimiliano Materazzi, a research fellow at UCL who leads this project.
Another option is to reimagine planes themselves. In fact, the industry’s efficiency drive is behind some of the most significant reimagining of commercial aeroplane design since the 1950s, with designers racing to cut weight and drag. “If you need less thrust, then you need less fuel,”
Vos says. For example, the Aurora D8 airliner concept developed by NASA and MIT University uses a double-width fuselage (nicknamed the ‘double bubble’) with a pointed nose, essentially turning the aircraft’s body into a wing.
At Delft, Vos and his team are working on the ‘Flying V’, a collaboration with Airbus and KLM that doesn’t have separate wings at all. “The fuselage and the wings are integrated in one component,” Vos explains. “We distribute the entire weight of the passengers, the cargo, and the structure inside that wing, which means less structural material.” With the cabin inside the wing surface, that means radically rethinking the interior design – the seats are staggered, ensuring all passengers can face forward, for example. But the change in space also creates room for different types of seating, such as train-style tables, and collapsible beds in the more confined space near the wing edge.
Unlike more far-flung electric concepts, Vos says, the Flying V’s advantage is that it could be built using existing technology, and is designed to work within existing airports. “There’s really no technology breakthrough needed for this airplane to fly,” he says. Vos’s researchers are now working on simulation models, to better understand how the aircraft would fly, with the hope that one of the main manufacturers might want to develop it further.
Unlike more far-flung electric concepts, Vos says, The Flying V’s advantage is that it could be built using existing technology, and is designed to work within existing airports. “There’s really no technology breakthrough needed for this airplane to fly,” he says. Vos’s researchers are now working on simulation models, to better understand how the aircraft would fly, with the hope that one of the main manufacturers might want to develop it further.
LIGHTER THAN AIR
Historically, hydrogen and flight have been associated with one thing: the 1937 Hindenburg disaster. But with aviation reassessing its impact on the climate, hydrogen is once again the subject of excited discussions, for obvious reasons: It’s energy dense, can be produced using renewable energy,
and when burned only has one emission – water. Thus, just as hydrogen cars are seeing significant investment, some companies are moving into the development of hydrogen aircraft. ZeroAvia, a California and uk-based startup, is currently working on a 10–20 seater aircraft using hydrogen fuel cells, which it claims will have a range of 300–500 miles, enough to fly from Los Angeles to San Francisco, or London to Frankfurt. “For the small regional airplanes – the average 19 seater – we can produce around four times the range compared to battery flight,” says Sergey Kiselev, ZeroAvia’s head of European operations. And Hybrid Air Vehicles, a uk company, hope to bring back giant airships to replace air freight (though their modern designs use helium, rather than hydrogen, to fly).
But many remain sceptical. Hydrogen, which is prone to leaking, requires large, delicate tanks for storage, and is highly flammable. Kiselev says these fears are overblown: “From a safety standpoint, hydrogen is actually much safer than kerosene because it’s a light molecule, it goes up in the air,” 37 he says. To circumvent this, nasa is currently researching using cryogenically cooled liquid hydrogen, which would be easier to store, and more efficient.
Other researchers are doubtful about its emissions. “If you emit water at high altitudes, you might get increased contrail formation, which could still give a global warming effect,” Vos says. Evidently, commercial airliners running on hydrogen are still decades away.
With our cars going electric, it might seem inevitable that aircraft do the same too. Indeed, many manufacturers are working on electric aircraft concepts: Airbus’s E-Fan X, which aims to replace one of four engines in a 100-seater jet with an electric motor (thus supposedly reducing emissions by 25 per cent), is expected to begin testing in 2022. EasyJet is working with Wright Electric on a short-haul electric plane, which it hopes might begin testing in 2023.
But electric flight faces a major obstacle: Lithium-ion batteries, which power almost all electronics – including electric cars – are simply too heavy. Developing electric planes has proven complex and expensive. Zunum Aero, a much-hyped electric- aircraft startup backed by Boeing, was driven all-but bankrupt, and looks likely to shut down.
There is hope, however, for smaller aircraft. Several companies, including Lilium, Airbus, Volocopter and China’s EHang, have demonstrated EVTOL (electric vertical take-off and landing) craft – better known as ‘flying cars’ – that can carry people, and may replace helicopters and private jets over short distances. EVTOLs “bring the benefits of emission-free flight with the ability to take off and land from a heliport,” explains Michael Cervenka, CEO of uk-based Vertical Aerospace, which is currently working on a craft designed to carry four passengers and a pilot up to 100 miles. “It will be certified to the same stringent safety levels as large civil airlines, whilst being considerably quieter and less expensive than helicopters.” Fleets of flying taxis would, inevitably, reshape the urban landscape; their proponents envision a landscape where roads are rewilded, and instead we travel overhead, zipping about in emissions-free fleets of autonomous drones. Critics argue that such visions are sci-fi nonsense, and that personal aircraft
are dangerous, unrealistic, or both. Either way, it’s likely that regular flying taxis are years away yet. Until then, the most sustainable way to fly is still not to fly at all.