Aircraft powered directly by hydrogen or batteries will account for just 5% of emissions reduction in aviation by 2050, a report from a US consultancy has found — analysis which appears to contradict the marketing effort on the part of the aviation sector, promising massive emissions reductions from H2 and all-electric aircraft.

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And the aviation sector as a whole is set to miss its 2050 net-zero targets by 30%, according to Bain & Co’s report, A Realistic Path to Net-Zero Emissions for Commercial Aviation.

However, hydrogen might have an important role to play in boosting output of bio-based sustainable aviation fuels (SAFs), which the report’s authors said would be critical to reducing emissions across the sector.

Long lead times required to get hydrogen and all-electric aircraft approved by regulators and commercially available, coupled with airlines’ reluctance to renew their existing fleets early, means that the actual contribution to emissions reduction from these novel technologies will be relatively negligible by 2050.

“Neither will mature fast enough to replace a substantial portion of the existing fleets in the next 30 years,” the report warned, without providing separate emissions reductions figures for all-electric and hydrogen.

In addition, hydrogen-powered aircraft designs could find themselves bogged with technical and logistical problems, lengthening lead times even further.

“Hydrogen’s low volumetric energy density requires changes to aircraft architecture, and hydrogen is difficult to transport and expensive to liquify,” the analysis continued, adding: “Both technologies [hydrogen-powered and all-electric aircraft] require a huge level of investment and substantial changes to airport infrastructure and aircraft architecture.”

French aircraft maker Airbus has promised to bring its hydrogen-powered aircraft into service as soon as 2035, as part of its ZEROe programme.

But the report authors believe that the sector will meet the majority of its emissions reductions (43%) from improving efficiencies in fleet and ground operations, with a further 23% from replacing fossil fuel-based Jet A1 kerosene with SAFs.

This means that, with the adoption of a few H2 and all-electric aircraft, the airline industry is set to achieve just 70% reductions by 2050.

But even this might not be achieved if governments do not take action to improve the supply of SAFs which under current projections will only reach 135 million tonnes by 2050, enough to replace just 35% of total jet fuel demand by that date.

In this scenario, SAFs would only be able to achieve an emissions reduction of 13%, while the sector as a whole would only achieve 60%.

Governments could boost SAF production by 15 million tonnes by incentivising the supply of green hydrogen towards SAF production. Green hydrogen can be used to increase yields of SAFs made using the Fischer-Tropsch process — a method used by producers signed up to supply fuel to Delta Airlines.

SAF production could also be boosted by incentivising biofuel refineries to make aviation fuels, and prioritising aviation-focused fuel production for access to biofuel feedstock. These measures would push up supply by 60 million tonnes and 30 million tonnes respectively, the document said, allowing the aviation sector to reach 70% emissions reduction.

Bain also forecasts that, by 2050, only 19% of SAFs would be synthetic e-fuel produced by combining green hydrogen with captured carbon dioxide.

Significantly, even if SAF supply was increased, the EU and US are likely to miss a swathe of their SAF blending targets, the report warned.

In April, the EU unveiled draft rules that would see planes refuelling with blends containing at least 2% of SAFs in 2025, of which 1.2% should be derived from synthetic aviation fuels, or “e-fuels” — hydrocarbons such as e-kerosene made by combining carbon molecules with green hydrogen made with renewable energy.

The blend mandates would be ratcheted up every five years until they reach 70% of SAFs by 2050, of which 35% should be made from e-fuels.

And the US is hoping to supply at least three billion gallons of SAF per year by 2030 and 35 billion gallons by 2050.

But according to Bain & Company’s analysis those goals will only be achieved if they adopt the three boosting measures outlined in their report — and even then only in 2030.

Otherwise, without importing volumes, the EU is set to miss its target by 7% in 2030 and 57% in 2050, while the US will miss by 30% in 2030 and 42% in 2050.

And even if they max out supply (excluding imports), the US will only achieve 81% of its target in 2050, and the EU 85%.