High hopes for airlines
The aviation industry is counting on innovation to achieve net-zero carbon emissions by 2050. But it remains a tall order, and travel bans and higher flying costs look likely
As aviation struggles to emerge from a pandemic-driven downturn, a longer-term challenge looms. Concern about air travel’s contribution to climate change 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, has 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 next 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 netzero emissions target is so radical, and the proposed technology solutions so uncertain, that aviation risks falling far short.
Airbus CEO Guillaume Faury recently said if the industry’s push for climate sustainability fails, governments could force a reduction in air travel by banning some of the flying that is routine today.
“Aviation has a very important role … to connect people and to contribute to prosperity,” he said at an aviation sustainability summit convened by Airbus in France in September. “This is in danger if we don’t manage to transition and succeed in the decarbonisation of the sector.”
Under pressure, 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.
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 ones that burn more gas and produce more carbon emissions. But further out, plane builders will need to develop dramatically new technologies.
Airbus is already pursuing research to develop by 2035 a zeroemission, 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 airlines announced the new “net zero by 2050” goal at last 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.
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, especially Europe, flying is already being curbed by government policy. France in April banned domestic flights between cities with a train connection of less than 2½ 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 shorthaul flights in Europe,” said Andrew Murphy, aviation director at Transport & Environment, a nonprofit organisation that campaigns for clean transport, at the Airbus summit.
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 humaninduced climate impacts grew as fast so that percentage contribution was constant.
The Atmospheric Environment analysis estimates only a third of aviation’s 3.5 per cent net contribution to climate change is from carbon dioxide emissions, with the largest contribution coming from aircraft contrails.
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 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-carbon dioxide impact on the climate – mostly from contrails, but also from soot particles, nitrogen oxides and other trace emissions – is twice as large as from its carbon dioxide emissions alone is cited with alarm by climate activists. But there’s great scientific uncertainty around the climate impact of non-carbon dioxide 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”.
At the 2021 UN Climate Change Conference, COP26, held this week in Glasgow, Scotland, countries are committing 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 is launching 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.
Faury is confident Airbus engineers will have a hydrogenpowered 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 -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 carbondirty 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.
Whatever the next plane is … sustainability is going to be a driving factor
MIKE SINNETT,
BOEING VICE-PRESIDENT OF PRODUCT DEVELOPMENT
It’s not good enough that we get incremental change in efficiency … To get to net zero we are going to need a fundamental change WILLIE WALSH, DIRECTOR GENERAL OF IATA
It may well be that the flying does cost a little bit more. But that will be a price worth paying
JOHN HOLLAND-KAYE,
CEO OF HEATHROW AIRPORT
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.
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 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, CEO 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.”