As mentioned in part one of this two-part series, the two e-fuels widely expected to perform best in coming decades are e-ammonia for long-distance maritime shipping and e-kerosene for aviation.

Part two explores the potential of e-kerosene in the context of sustainable aviation fuel (SAF)—a sectoral term for biofuels and e-fuels and the primary way the global aviation sector is hoping to decarbonise through 2050—followed by the major barriers e-kerosene must first overcome.

Potential scale

The aviation sector acted as a trendsetter in 2009 when the Geneva-based International Air Transport Association (IATA), representing almost 300 airlines worldwide, set a goal of slashing its CO₂ emissions to half of 2005 levels by mid-century. Recently, Transition Economist reported that Willie Walsh, IATA’s director general, is planning to ask his member carriers to adopt a net-zero emission target for 2050 at their annual meeting in Boston in October. Aviation presently contributes around 2.5pc of global total anthropogenic CO₂ emissions.

Analysis by the World Economic Forum shows that, absent government support, e-fuels may be economical in the 2035 timeframe” Dodd, ATAG

Late last year, the cross-industry Air Transport Action Group (ATAG) released Waypoint 2050, a report providing three plausible pathways for meeting the global aviation sector’s emission commitment. The core ways to reduce emissions are: improving aircraft and engine design to produce lighter, more efficient aircraft; developing hydrogen- and electric-powered aircraft; and using SAF. But since the report was released, plane manufacturer Airbus has backtracked on when it could be manufacturing commercial hydrogen-powered aircraft, now agreeing with fellow manufacturer Boeing that they will not be widely available before 2050.

According to Haldane Dodd, head of communications at the Geneva-based ATAG, he and the other authors of the report recognised that hydrogen-powered aircraft faced ‘several key challenges’ and, as a result, assumed these aircraft would be flying no more than short-haul routes over the 2035 to 2050 period.

“It will likely be a source of energy for only short-haul flying, and so we will need to ensure a supply of traditional liquid fuel in the form of low carbon sustainable aviation fuels for longer-haul routes,” Dodd tells Hydrogen Economist. “If the hydrogen opportunities do not bear fruit, SAF can also be used for those routes as well.”

In the three ATAG scenarios, SAF contribute 50-75pc of emission reductions for the global aviation sector as of 2050. The report does not break down SAF between biofuels and e-fuels but does indicate biofuels as dominating earlier in the projection period, before e-fuels become economic later in the period. “There will certainly be a reliance on bio- and waste-derived SAF in the early years, but a larger use of power-to-liquid [e-fuels] as we get closer to 2050,” says Dodd. “There is not one solution, but a menu of options depending on local market opportunities to supply the required feedstocks.”

In terms of meeting a possible net-zero target for the global aviation sector by 2050, the weight of emissions reductions would fall even more upon SAF, according to Dodd. “Net-zero is possible through a ramp-up in SAF supply and using offsetting (likely in the form of carbon removal) to account for any residual emissions,” he says. “Already a number of airlines have committed to net-zero as a goal. Some parts of the world may need a little longer to achieve this, but the decarbonisation of air travel is possible, albeit a significant challenge.”

Major barriers

The two major barriers to relatively timely development and use of e-kerosene for aviation are the cost of green hydrogen and a sufficient quantity of economic negative-emission CO₂. “Analysis by the World Economic Forum shows that, absent government support, e-fuels may be economical in the 2035 timeframe,” says Dodd. “However, there have also been recent announcements to try and bring down the cost of hydrogen, which may change these dynamics.”

On the other hand, a lack of economic negative-emission CO₂ could pose an even greater barrier, since direct air capture (DAC) is likely to be its main source, based on a process of elimination. “Point source CO₂ is negated because emission reductions cannot be double counted, with the companies capturing it to receive the credit,” Tristan Smith, a professor at University College London’s Energy Institute, tells Hydrogen Economist. “Biomass will not be the source, because it would be more economic to simply turn it into biofuels, assuming the feedstock is available. That leaves DAC, an extremely high cost method for capturing CO₂ because of its low concentration in the atmosphere.”

The first part of this two-part series explored the potential of e-ammonia for shipping through 2050 as well as the major barriers it must first overcome.

---

Author: Vincent Lauerman