Biofuelsare produced from crops that are using scarce land and water resources needed for food and survival. Even worse, they may be grown on cleared forest land. Biofuels from recycled waste (such as used cooking oil, or municipal waste) cannot be scaled up sufficiently to make a large contribution. Even if produced from ‘waste’ products, burning biofuels is still releasing carbon that otherwise would be sequestered in the soil.
Synthetic fuel(‘synfuel’) is very inefficient and expensive to make, combining hydrogen produced from water by electrolysis, with carbon from Direct Air Capture (DAC). DAC is still in its infancy, and both require a lot of electricity. To produce the equivalent of the UK’s current annual consumption of 11.7m tonnes of aviation fuel would require 250TWh (TerraWatt-hours, 1TWh = 1bn KWh) – almost 75% of the total UK electricity generation (330TWh in 2018). This must be renewable electricity to call flights sustainable, and UK renewables currently only produce 110TWh a year.
Aviation requires higher quality fuel than road vehicles, so is more difficult to produce, either as biofuels or synfuel.
Sustainable Aviation’s most optimistic projections still only show SAF reducing emissions by 4-8% by 2035 (UK production of 1m tonnes/year, www.sustainableaviation.co.uk/goals/climate-change/). IATA target is only 2% by 2025.