Electricity, hydrogen and green kerosene planes are coming

A few years ago it would have been hard to imagine, but airlines have also committed to climate neutrality by 2050. The solution lies in sustainable aviation fuels, hydrogen and electric aircraft, which are already well under development.

Perhaps the economic sector most visibly affected by the coronavirus epidemic is the aviation industry. This is illustrated by the fact that, after two decades of rapidly rising carbon emissions, the pandemic last year sent the sector’s emissions down by about a third to 1997 levels, compared with the previous year. However, following this unprecedented collapse, the number of passengers and the volume of cargo carried is expected to rise steadily again in the coming decades. Without a number of new operational and technical solutions and changes in habits, the sector’s greenhouse gas emissions could skyrocket again, the International Energy Agency (IEA) warns in its November assessment of the sector.

As in other areas, financial and regulatory measures to improve efficiency can contribute to making the aviation sector more climate-friendly in the short term. This is also true for the management of investment risks to support the expansion of sustainable fuel use. As low-carbon fuels and other technologies become more widespread, airlines will seek to offset emissions to some extent by promising offsetting measures, such as financing tree planting, wind farms or methane capture projects.

While these undoubtedly have social benefits, they do not actually reduce the amount of carbon dioxide emitted from jet engines. Not to mention the consequences in terms of concentrations of other gases, which exacerbate global warming.

More interesting, and with greater potential for achieving long-term climate goals, is the development of alternative technologies such as sustainable aviation fuels, hydrogen or electric aircraft. There is a need to exploit this potential, as emissions from this sector are responsible for around 3.5% of global warming. This may not seem like much, but it should not be an exception to the scope of emission reduction measures.

The case for green alternatives is underlined by the fact that it does not seem likely that environmental concerns or the anti-flight shame movement will cause everyone to switch from flying to the much lower carbon footprint train (see also: climate summit and private jets) when they can. In fact, like the climate-destroying fashion for SUVs, flying has become very popular in recent years for shorter distances, with the powerful help of airlines. The pressure to ban short-haul flights is growing in the EU. But as they account for only a few percent of total aviation emissions, the desired measure alone would not solve the problem.

Staying with the EU, the Community has also set ambitious greening targets for the aviation sector, which the inclusion of EU carbon emissions in the trading scheme could bring us closer to achieving. There seems to be a clear perception in the industry of the growing sustainability expectations of society and investors.

At this year’s International Air Transport Association (IATA) conference in October, for example, airlines representing its membership agreed to commit to achieving climate neutrality by 2050. This seems a significant commitment. If only because by 2050, 10 billion passenger journeys are expected to be made by air each year.

The industry association currently believes that the bulk of the emissions reduction challenge, around 65%, can be met by sustainable fuels such as alternative kerosene, which can be produced from wood and tobacco waste, sugar cane or used cooking oil and can be used in today’s engines without modification. Sustainable aviation biofuels (SAF or biojet), however, have similar concerns to biomass.

As the carbon in them is derived from biomass, their combustion releases carbon dioxide extracted by plants back into the atmosphere. This means that their sustainability depends first and foremost on the biomass used as feedstock coming from sustainable agriculture. If this can be achieved, it is possible to reduce carbon dioxide emissions over the entire life cycle of the fuel by 80-90% compared to fossil kerosene.

According to the IEA’s scenario leading to climate neutrality in 2050, bio kerosene could account for approximately 15% of total aviation fuel consumption in 2030, compared to currently known international plans to achieve blending rates of 1-5% by 2025, which means that the transition clearly needs to be accelerated.

Another alternative to fossil fuels could be sustainable synthetic kerosene. If the process that requires electricity is based on clean, renewable electricity, using carbon dioxide extracted directly from the air as a feedstock, the resulting fuel will be virtually carbon neutral.

The first passenger flight powered by partially sustainable synthetic kerosene took off in February 2021, meaning that the technology, which is 3-6 times more expensive than conventional jet fuel, is still in the early stages of commercialisation. However, the technology is being developed globally, which foresees a reduction in costs in the future. In any case, the EU’s current target is for clean fuel to account for 28% of liquid fuel used in European aviation by 2050.

Like hydrogen-rich synthetic fuels, green hydrocarbons produced by water decomposition using solar or wind energy could also play a significant role in meeting future energy needs in aviation and transport. The industry association now estimates that hydrogen’s share of the aviation fuel market could be around 13% by mid-century. Europe’s largest aircraft manufacturer, Airbus, is also betting on hydrogen, having shifted its focus from smaller, electric aircraft to this technology.

Costs, lack of airport infrastructure and other barriers still stand in the way of the uptake of hydrogen-powered aircraft today. However, Airbus plans to have the first planes capable of carrying up to 200 passengers and travelling up to 3,500 kilometres in service around 2035. Others, such as the UK government, have similar plans.

Several other companies are also looking to hydrogen technology. Los Angeles start-up Universal Hydrogen, for example, is developing a fuel distribution network that delivers hydrogen to machines in modular capsules. And even more interestingly, it is designing conversion kits that can be retrofitted to aircraft. Another company, Ampaire, also based in Los Angeles, is developing hybrid electrical systems that can also be retrofitted to smaller aircraft. It is not the only such venture, with United Airlines already planning to mass-produce the new technology.

As for battery-electric planes, existing prototypes of these today can carry up to 20 passengers over 100 kilometres. Their range is not expected to exceed 1000 kilometres by mid-century. As this propulsion is likely to remain suitable only for shorter-haul air travel – which accounts for a small proportion of the sector’s emissions – its emission reduction potential appears limited, but the range of the various hybrids could reach 3000 km in the future.

Battery innovation breakthroughs will be needed to accelerate the uptake of the technology. This is even more true for aircraft than for electric cars. Lithium-air batteries, which can achieve the same energy density as aviation fuel, are still at a very early stage of development. A further challenge is that batteries, unlike fuel tanks, do not become lighter during flight.

The barriers to technology are illustrated by the fact that, for example, replacing the jet engine of a Boeing 747 would require more than 500 tonnes of the lithium-ion battery currently widely used. This would be such an extra load that even if it could be crammed into the jumbo, it would be impossible for the plane to take off. To lift this weight into the air, eight additional jets would be needed. At the same time, more and more manufacturers are designing and building electric aircraft that look even bizarre.

For example, the speed record holder Rolls-Royce and NASA. The world’s first all-electric airline is already preparing to enter the market. For now, they are all concentrating on the smaller size range because of technical limitations. There is also notable activity in the single and double-seater aircraft and air taxi categories. It is not excluded that they could play a significant role in the not too distant future in alleviating urban congestion and air pollution.