MaREI Director Jerry Murphy talks Sustainable Aviation Fuel on RTE Radio 1
MaREI Director Jerry Murphy spoke with Philip Boucher-Hayes on RTE Radio 1 about three critical issues in the decarbonisation of aviation.
1. Combustion of jet fuel is responsible for 2% of the world’s CO2 emissions. However non-CO2 warming effects are greater than warming from CO2 emissions. This is because combustion takes place at 33,000 feet. Non-CO2 warming is induced by particulates, water vapour (contrails) and NOx. If we replace jet fuel with SAF we still have these non-CO2 warming effects.
2. Batteries are too heavy and voluminous for heavy long distance travel. Jet fuel consumption is far in advance of the potential resource of biofuel (termed bio-SAF). Shipping (of a similar order to aviation) also needs liquid biofuels. Agricultural land is limited to about 0.2 ha arable land per person. Bio-SAF may get us to 15 or 20% replacement of jet fuel. After we exhaust bio-SAF we will then need to make E-SAF ( fuel from electricity) which will use offshore wind and photovoltaic to make hydrogen (splitting water into hydrogen and oxygen). Hydrogen is an essential element in liquid fuels (hydro-carbons). The other element is carbon. Carbon needs to be sucked out of the air by direct air carbon capture. The cost of direct air carbon capture is about €400 / t CO2.
3. SAF will be very expensive, of the order of 3 times cost of jet fuel, and this will only reduce the warming effect from aviation by about 60%. For true mathematical net zero aviation we will need SAF plus more Direct Air Carbon Capture, combined with sequestration, to match the non-CO2 warming. The cost of flights will increase hugely to the extent that flying will reduce.
