Rolls-Royce has debuted its biggest-ever jet engine, which could lead to much greener air travel
The Telegraph says that, with aviation accounting for about 2.5% of carbon dioxide emissions, the industry is under pressure to move towards zero emissions by 2050.
Around the world, engineers are attempting to crack the seemingly-impossible challenge of fuelling long-haul flying without generating large emissions.
Batteries and hydrogen are among alternatives to jet fuel being explored.
But there is a synthetic version of jet fuel which can, with a few small modifications, power existing jet engines.
As well as recycling carbon dioxide, Sustainable Aviation Fuel (SAF) produces less in the way of particles that are blamed for helping warm the earth. SAF is likely to be needed for long-haul flights until technology catches up.
More costly
However, in current engines, the Telegraph says it costs five times as much as its fossil-fuel counterpart.
Rolls-Royce is aiming to narrow the cost gap with the UltraFan.
The engine will be 25% more fuel efficient than its 1990s-era predecessor. It achieves this by being very big - more than 11ft across.
Rather than shifting air more quickly, as other incrementally-better engines have in the past, it will shift more air through a bigger fan, thus improving efficiency.
Simon Burr, director of product development and technology at Rolls-Royce, explained that this strategy, combined with falling SAF prices as technology improves, offers the potential to get "much, much closer" in price to jet fuel, he says. And with it, bring the prospect of guilt-free flying closer.
The fuel that will be used in UltraFan testing is made from used cooking oil. This is not a long-term solution because there will never be enough to fuel the world's planes.
Jet fuel from waste
However, SAF can be made in a number of ways, said Andrew Cornell, chief executive at Advanced Biofuel Solutions, which is developing the means to make jet fuel from waste.
Household waste is the obvious raw material to use, he says. It is run through a number of chemical processes to make first gas and then liquid fuel which, just like oil, can be refined into jet fuel.
Biomass, another feedstock, is broadly carbon neutral because it starts off as plants capturing carbon dioxide.
"You're recycling carbon dioxide rather than generating new carbon dioxide," added Mr Cornell.
This can be combined with carbon capture to reduce the carbon output of the fuel to zero.
Another approach to making SAF is using electrolysis to split water molecules and combining the hydrogen produced with carbon dioxide in the air, though this is a more energy-intensive process.
Huge demand
"You'll need both because overall demand is huge," stated Mr Cornell.
Henrik Wareborn, chief executive of biofuel developer Velosys, estimates that SAF could ultimately cost twice as much as jet fuel, but high tax on fossil fuels and low tax on green fuels could squeeze the difference.
- In October, Aberdeen International Airport welcomed its first commercial delivery of SAF.
It came from Air BP - the aviation division of BP - one of the world's leading suppliers of aviation fuel products and services.
The SAF is blended with traditional jet fuel for Bristow flights to BP's North Sea operations in UK waters.
BP is the first North Sea operator to voluntarily commit to an ongoing supply of SAF for its North Sea flights, helping to decarbonise transport to its offshore operations.
Scottish Transport Minister Jenny Gilruth has said the increased use of sustainable aviation fuels will be an essential stepping stone towards the Scottish aviation sector reaching net-zero.
She added: "The use of these fuels is expected to rise significantly in the coming years and could bring significant economic opportunities for Scotland, so this is a welcome first step from Aberdeen Airport."
The creation of a SAF facility at St Fergus is a key part of the North East Scotland Green Freeport bid. A SAF plant would create up to 920 jobs and £133million in GVA per year.