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Technology will be the aviation industry’s answer to climate change. Air travel is the fastest growing source of greenhouse gas emissions. Photo: Scott Barbour/Getty Images

Airlines fighting climate change look to technology to become more sustainable, avoid flight bans and achieve net-zero carbon emissions by 2050

  • The aviation industry, already battered by the pandemic, must now deal with another problem: its contribution to climate breakdown
  • Technology holds some answers, but a massive investment in infrastructure and aircraft design will be needed, and soon

As aviation struggles to emerge from a pandemic-driven downturn, another, longer-term challenge already looms. Concern about air travel’s contribution to climate breakdown threatens to curtail its growth after decades of expansion that has shrunk the world for travellers and connected the global economy.

The airline industry, contending with growing political pressure for new restrictions on flying, this month formally committed to a target of “net zero” carbon emissions by 2050. To achieve that, governments and industry will have to invest billions of dollars in infrastructure in the coming decade. Further out, Boeing and Airbus will have to develop dramatically new aircraft designs.

For the flying public, all outcomes point to an increase in the cost of flying. Yet that distant net-zero emissions target is so radical, and the proposed technology solutions so uncertain, that aviation risks falling far short.

Airbus chief executive Guillaume Faury recently warned that if the industry’s new push for climate sustainability fails, governments could force a reduction in air travel by banning some of the flying that is routine today.

Guillaume Faury, Airbus chief executive, has warned that governments could restrict flights if air travel doesn’t become more sustainable. Photo: Pascal Pavani/AFP

“Aviation has a very important role on the planet to connect people and to contribute to prosperity,” he said at a two-day aviation sustainability summit convened by Airbus in France last month. “This is in danger if we don’t manage to transition and succeed in the decarbonisation of the sector.”

Under pressure, the world’s major airlines have firmly committed to one key technology that will dominate aviation’s environmental push in the coming decade: sustainable aviation fuel, or SAF.

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In the near term, Airbus and Boeing will make money from the airlines’ push for sustainability by promoting the sale of new, more efficient jets to replace older planes that burn more gas and produce more carbon emissions. But further out, the plane builders will need to develop dramatically new technologies.

Airbus is already pursuing research to develop by 2035 a zero-emission, short-haul airliner powered by hydrogen. Boeing contends that hydrogen-powered aircraft won’t be realistic until as late as 2050. But as Mike Sinnett, Boeing vice-president of product development, recently said, “whatever the next plane is, we recognise sustainability is going to be a driving factor”.

After the world’s airlines announced the new “net zero by 2050” goal at this month’s annual conference of the International Air Transport Association (IATA), its director general, Willie Walsh, demanded a big technology leap from Airbus and Boeing. “It’s not good enough that we get incremental change in efficiency with the aircraft. To get to net zero we’re going to need a fundamental change,” he said.

Ageing aircraft such as this Boeing 747 will need to be replaced by more efficient planes. Photo: George Rose/Getty Images

Boeing projects the world’s fleet of airliners will double by 2040, driven by growth in emerging economies. That’s an appalling prospect to Sarah Shifley, a lawyer who volunteers on the aviation team of climate activist group 350 Seattle.

“After the summer we’ve had, of heat domes and hurricanes and floods and fires, it’s unfathomable to me to be considering doubling” air traffic, she said.

In some places, particularly Europe, flying is already being curbed by government policy. France in April banned domestic flights between cities with a train connection of less than 2.5 hours. Government agencies and organisations around Europe have imposed similar bans on short-haul flights for employee business travel.

“What would drive innovation and drive focus in the sector is if we were to say, by 2035, we will end the sale of jet aircraft for short-haul flights in Europe,” said Andrew Murphy, aviation director at Transport & Environment, a non-profit that campaigns for clean transport, at the Airbus summit.

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The most recent comprehensive scientific analysis of aviation’s impact on the atmosphere over time – published in January in the journal Atmospheric Environment – estimated the sector’s contribution as 3.5 per cent of total human-induced climate change based on 2011 global flight data. That’s the same percentage calculated by the UN’s Intergovernmental Panel on Climate Change more than two decades ago based on 1992 flight data.

Although aviation grew enormously between 1992 and 2011 as the world’s fleet of airliners more than doubled, the increasingly efficient aeroplanes burned less fuel. Meanwhile, other human-induced climate impacts grew as fast so that percentage contribution was constant.

The Atmospheric Environment analysis estimates that only a third of aviation’s 3.5 per cent net contribution to climate change is from its CO2 emissions, with the largest contribution coming from aircraft contrails.
Jet contrails can become diffuse cirrus clouds that reflect terrestrial radiation, increasing warming. Photo: EyesWideOpen/Getty Images

A jet contrail – the line of what looks like white smoke that sometimes trails a plane – is not an emission. It’s water vapour that is already in the air around the plane that’s triggered to condense, forming ice particles. Although contrails often disappear completely in a short period, under certain atmospheric conditions they persist as diffuse cirrus clouds that reflect terrestrial radiation, with a net warming effect.

The conclusion that aviation’s non-CO2 impact on the climate – mostly from contrails, but also from soot particles, nitrogen oxides and other trace emissions – is twice as large as that from its CO2 emissions alone is cited with alarm by climate activists. However, there’s great scientific uncertainty around the climate impact of the non-CO2 emissions.

A lead author of the Atmospheric Environment paper, David Fahey, of the United States’ National Oceanic and Atmospheric Administration in Boulder, Colorado, said that modelling the effect of contrails is complex, producing calculations with such wide probability ranges that the warming impact is “of uncertain magnitude”.

A giant sand artwork highlights the net-zero carbon pledge and the COP26 global climate conference. Photo: Christopher Furlong/Getty Images

At the 2021 United Nations Climate Change Conference, COP26, which is winding down in Glasgow, Scotland, countries have committed to new targets to lower emissions.

As a global business, international air travel has until now fallen outside the scope of those national targets, its goals instead set through the UN’s International Civil Aviation Organisation, which is heavily influenced by the world’s airlines.

However, as conference host, Britain launched the International Aviation Climate Ambition Coalition in Glasgow to try to get more countries to sign a substantive declaration on aviation emissions. Clearly, if aviation is to avoid regional restrictions being imposed on flying, major industry players will have to convince the public and governments that they are taking real action.

It’s not good enough that we get incremental change in efficiency with the aircraft. To get to net zero we’re going to need a fundamental change
International Air Transport Association Director General Willie Walsh

Faury is confident Airbus engineers will have a hydrogen-powered short-haul aeroplane ready by 2035 but, at the IATA conference in Boston, Boeing Commercial Airplanes chief Stan Deal expressed his doubts that hydrogen-powered airliners could be ready in that time frame.

First, there’s the complexity of a totally new vehicle design. Deal pointed out that liquid hydrogen occupies 18 per cent more volume than current jet fuel and must be wrapped in cryogenic equipment to keep it cooled to -418 degrees Fahrenheit (-250 degrees Celsius). Designing such a system, he said, presents “some physics problems”.

Certifying it as safe to fly also will be a major hurdle. Sinnett says: “To have a safe system that can carry liquid hydrogen and be as safe as we are with jet fuel today, that might be bigger and heavier than you want to put on an aeroplane”.

In addition, hydrogen production requires lots of electricity – and if that comes from a carbon-dirty source, there’s no net climate benefit in using it as fuel. So energy companies will have to vastly scale up production of “green hydrogen” from sustainable sources.

Technological innovation will help make air travel less damaging to the environment, but flights will likely become more expensive. Passengers travel through Lisbon Humberto Delgado International Airport. Photo: Horacio Villalobos/Corbis via Getty Images

Then airports around the world will have to invest in the cryogenic tank infrastructure and equipment needed to dispense the liquid hydrogen.

While Boeing has worked with Nasa on various “green plane” concepts, for now it offers the prospect of only incremental technology tweaks to its current planes. Otherwise, it promotes SAF as the potential solution to aviation’s climate impact. Yet that too is a difficult technological goal.

SAF is a hydrocarbon fuel typically produced from biomass feedstock such as waste oils or plant debris and purified so the final liquid is essentially identical to current jet fuel.

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When SAF burns in a jet engine, it produces the same carbon emissions. Nevertheless, it’s deemed “sustainable” because the life cycle of those emissions shows the carbon being absorbed from the air by plants, then recycled back to the air. This contrasts with fossil fuel, where the carbon going into the air had previously been sequestered underground for millions of years.

If SAF is carefully produced using the cleanest methods, it’s touted as providing a life-cycle reduction in carbon emissions of between 50 per cent and 80 per cent compared with fossil fuels. Because SAF can be simply dropped in a tank the same as jet fuel, neither the design of the aircraft nor the fuelling infrastructure at the airport need to change.

The problem is producing SAF in sufficient quantities at an affordable price. The small quantities produced today cost five to seven times as much as jet fuel. Also, identifying truly sustainable SAF sources is problematic. Imported palm oil, for example, the cause of deforestation in Southeast Asia, is unacceptable. And producers must consider what land use is displaced by growing the feedstock.

Still, momentum and investment are building to overcome these obstacles and many SAF projects are in the works around the world.

At the Airbus summit, John Holland-Kaye, chief executive of London’s Heathrow Airport, said that without sustainability “we won’t have a business”.

“It may well be that the flying does cost a little bit more,” he said. “But that will be a price worth paying.”