Sustainable Aviation?

On the 28th of November 2023, the first long-haul passenger plane powered with 100% ‘sustainable’ air fuel took off.

The Virgin Atlantic Boeing 787 from London to New York is reportedly using two types of SAF (Sustainable Air Fuel).

88% is based upon waste fats.

12% from US corn waste.

SAF offers an ostensibly attractive path for decarbonisation for the airline industry – the lifecycle greenhouse emissions can be up to 70% lower than conventional fossil-based fuels.

Does SAF offer a flight path to sustainability?

While this in many ways represents a significant breakthrough (SAF is currently perhaps 0.1% of global aviation fuel use) there are major challenges ahead.

The UK Government’s Jet Zero Strategy places a significant reliance upon SAF as a viable route to decarbonisation – and one that might broadly support business as usual in the sector.

However, SAF, whilst having a reduced impact on climate, is not carbon-free and currently, there are insufficient feedstocks to meet anticipated production demands.

In February 2023, the Royal Society published a report (Net zero aviation fuels: resource requirements and environmental impacts) which warned that there is no feasible sustainable alternative that would support flying at current levels.

The report is worth a read, to summarise (hugely) it suggested that for the main SAF types, the following challenges exist:

• Biofuels (from crops and waste) – Energy crops would require 50% of the UK’s agricultural land. In addition, there can be competition for waste feedstocks.
• Hydrogen – Producing enough green hydrogen would need 2.4 – 3.4 times the UK’s annual renewable electricity capacity.
• Ammonia – Producing enough green ammonia would need 2.5 – 3.9 times the UK’s annual renewable electricity capacity.
• Synthetic fuels – if produced with renewable energy would need 5 – 8 times the UK’s annual renewable electricity capacity.

There remains huge uncertainty over the viability of Jet Zero targets and whether today’s achievements mark the early steps towards less damaging flying or an interesting footnote for a flight path with an unsustainable destination.