Air cargo and aviation in general generate a large amount of C02 emissions. The International Council on Clean Transportation estimates that in 2018 2.4% of total C02 emissions came from commercial aviation. Airline association IATA puts the figure for 2019 at around 2%.
And many studies suggest that when other outputs are included, such as contrails and nitrogen oxides, aviation’s contribution to climate change increases to between 3.5% and 5%.
While this figure is dwarfed by other industries, such as coal’s 40% of total C02 emissions, it is still a significant figure and one the industry knows it needs to tackle as concerns over the impact of global warming grow and regulators clamp down on polluting industries.
To help mitigate concerns, airline association IATA and United Nations body the International Civil Aviation Organization (ICAO) have been on the front foot and set the industry the target of achieving net zero emissions by 2050.
IATA has broken down how it expects the industry to achieve this ambitious target: a 65% reduction in emissions through the use of sustainable aviation fuels (SAF), 13% from hydrogen and electric propulsion, 3% from more efficient operations and 19% through offsets and eventually through carbon capture.
SAF therefore plays a key role in aviation achieving its carbon reduction aims and cargo has been leading the way in its implementation.
The last few years have seen the cargo industry embrace the use of SAF as shippers increasingly require sustainable transport solutions to meet their own Environmental, Social and Governance (ESG) requirements.
However, sustainable fuels are often misunderstood and not everyone is quite as positive about their environmental credentials.
The first common misconception about SAF is that it emits zero carbon. SAF emits as much CO2 as jet fuel in flight and it is only when life cycle emissions are taken into account that producers can claim the fuel reduces greenhouse gas emissions by up to 80% compared with fossil jet fuel use.
So where do these life cycle emissions savings come from?
SAF uses waste products such as cooking oil, animal fat waste, grease, municipal waste and agricultural, forestry waste and residues as well as biomass. It can also be created from crops grown specifically to be turned into fuel.
The savings are calculated in two ways. Firstly, IATA says that if a crop that absorbs carbon dioxide during its lifetime is then used for SAF, the carbon absorbed by the crop when it is growing is roughly equivalent to the amount of carbon dioxide produced when the fuel is burned in a combustion engine.
“This would allow the SAF to be approximately carbon-neutral over its life cycle,” IATA says.
However, the organisation points out that emissions are also created during the production of SAF, from the equipment needed to grow the crop, transport the raw goods, refine the fuel and so on.
Secondly, IATA says that in the case of SAF produced from municipal waste, the environmental gains are derived both from avoiding petroleum use and from the fact that the waste would be otherwise left to decompose or used in an incinerator and generate carbon in the process.
Cait Hewitt, policy director at non-governmental organisation the Aviation Environment Federation (AEF), tells Air Cargo News that SAF is being embraced because not much needs to be done to accommodate it in small quantities and it doesn’t require the transformational change required for other options such as hydrogen-powered aircraft.
Part of the concern for AEF is how the SAF is produced. She says that in the UK, SAF is mainly produced by unsustainable industries such as intensive meat production or fossil fuel extraction in the case of SAF made using unrecyclable plastic.
“All SAFs work like offsets; they don’t reduce emissions from aircraft at all – just as much CO2 is released by a plane burning SAF as by a plane burning kerosene,” she says.
“All the supposed emissions reductions come on a net basis from other sectors of the economy.
“That raises issues like risks of double counting of emissions savings and of judgments about what emissions cuts would or should have happened anyway.
“You can reduce waste by turning it into jet fuel but actually the UK is committed to eliminating landfill waste anyway. It’s much better for it to be avoided or recycled than combusted.”
Looking ahead, there are also concerns that as demand for SAF ramps up, the source material could be produced in an increasingly unsustainable way.
Hewitt says that there are no readily available feedstocks for alternative aviation fuel that can be easily ramped up without unwanted environmental consequences.
Plantations of crops such as palm oil, rapeseed or soy that can be used for SAF can result in deforestation and can also have a negative impact on biodiversity.
“Land is in demand for agriculture and forestry for example so shouldn’t be used to grow biofuel crops,” explains Hewitt.
Growing crops specifically for biofuel can also sometimes involve using land that had crops or trees that were already consuming carbon anyway. The logic only works if they are planted in an area that otherwise would not have been turning carbon into oxygen.
There are also concerns about whether enough SAF can be produced and at what cost. Figures from IATA suggest that in 2024 SAF production is expected to reach 1.9bn litres, which accounts for just 0.53% of aviation’s fuel need. It also represents around 6% of total renewable fuel capacity.
IATA says that this allocation limits SAF supply and keeps prices high.
It believes aviation needs between 25% and 30% of renewable fuel production capacity for SAF if it is to reach net zero carbon emissions by 2050.
“It is government policy that will make the difference. Governments must prioritise policies to incentivise the scaling-up of SAF production and to diversify feedstocks with those available locally,” says Willie Walsh, IATA’s Director General.
One potential future technology that could help allay concerns over the sustainability of SAF is the development of synthetic e-fuel.
E-fuels are made by using electricity to combine hydrogen obtained from water and carbon dioxide from the air.
The carbon emitted when using the fuel is the same as was extracted from the air when it was originally created.
However, producing hydro-carbons in this way is energy intensive – renewable energy would need to be used for it to be carbon neutral – and the costs can be high.
“E-fuel could have a role in cutting emissions for long-haul flights but comes with a range of problems,” says Hewitt.
“While in theory they can be produced from renewable energy that is more scalable than other SAF feedstock options, in practice the supply of renewable electricity is likely to remain constrained.
“To provide enough e-fuel for all UK flying we’d need to be putting up a new wind turbine once every three days continuously between now and 2050.”
She adds that other sectors would also be looking to use the e-fuel that is produced and if supply is limited others may be prioritised over aviation.
The cargo industry is however already investing in the development of the fuel type and in 2021 Kuehne+Nagel and Lufthansa Cargo agreed on a partnership for the promotion and use of power-to-liquid (PTL) synthetic fuel.
The two companies agreed to purchase 25,000 litres of the fuel per year from the world’s first production site for synthetic crude oil in Germany.
At this stage, the production of e-fuel is small in scale and the cost is likely to be even higher.
While there are many question marks over the use of SAF, it remains aviation’s least-worst solution to reducing carbon emissions if we want to continue flying people and goods across the globe.
Until new technologies or other alternative fuels gain traction, the only real alternative solution is keeping planes on the ground.
