The pathway from seasonal waste to sustainable aviation fuel
An overview from Rory Hannah, Krishnikha Ananthakrishnan and Eleanor Borrill from the University of Sheffield
Christmas Day is all about celebrating and indulging, but the increased consumption also drives a substantial and highly concentrated rise in household waste. In the UK, government guidance notes that waste generation can increase by around 30% at this time of year, adding pressure to collection systems and increasing the volume of material sent for disposal. Estimates from Defra further suggest that the additional waste produced over Christmas exceeds 3 million tonnes nationally, reflecting the combined impact of packaging, food waste and seasonal garden waste. Food waste is particularly prominent, with Defra citing that of the 175 million mince pies purchased, approximately 74 million are discarded.
Importantly, much of this ‘waste’ retains significant resource value. Cooking fats and oils are energy-dense lipid feedstocks, paper and card contain recoverable carbon, and woody biomass such as Christmas trees can be converted into useful chemical intermediates. When these streams are appropriately separated and processed, they can be redirected away from landfill and towards fuel production, including sustainable aviation fuel (SAF). This provides a practical link between everyday seasonal waste and industrial decarbonisation, setting the context for how waste-derived pathways such as HEFA (hydrotreated esters and fatty acids) process, anaerobic digestion and Fischer–Tropsch synthesis can contribute to lower-carbon aviation.
From waste to SAF
The journey to producing SAF from your holiday waste is a marvel of chemistry and engineering, ensuring that materials like the turkey grease from dinner, the discarded wrapping paper, and even your Christmas tree don’t end up polluting landfills.
This whole process begins with intensive sorting and processing to separate the waste streams, which are then collected and transported to a site. Major industrial sites, such as the industrial hubs planned for Teesside are being identified as key locations for developing large scale waste to fuel plants. The materials are then channelled into several different processing pathways.
One common pathway is the HEFA route, which is perfect for the cooking grease from dinner, waste fats and oils from waste food and alcohol. This process takes the grease from dinner and refines it with hydrogen in a catalytic process called hydrotreating, turning the long-chain fatty acids into jet-ready hydrocarbons, specifically synthetic paraffinic kerosene (SPK).
Leftover food and unfinished wine or beer can feed anaerobic digestion, producing biogas. This biogas can power SAF production facilities or be upgraded into renewable fuels used elsewhere.
For more solid waste, such as your old Christmas tree and recycled plastic, the Fischer-Tropsch (FT) synthesis method can be used, serving as a direct pathway to SAF. This involves gasification, where the solid waste is converted into a clean synthesis gas (syngas). This syngas is then reacted over a catalyst to build new hydrocarbon chains suitable for jet fuel.
Using waste plastic as a feedstock gives this residue a crucial second life, diverting it from landfill and linking it to decarbonisation targets supported by related policies, especially when coupled with carbon capture and storage to manage process emissions. The development of this capability locally in the UK represents massive future possibilities for a green energy industry.
A robust policy framework is essential to scaling up SAF production from waste streams, including the surge of materials generated over Christmas. In the UK, the Renewable Transport Fuel Obligation (RTFO) provides foundational support by awarding credits to eligible SAF pathways, improving project economics for waste- and residue-based fuels. Market signals are further strengthened by the UK Emissions Trading Scheme (ETS) and the International Civil Aviation Organization (ICAO)’s global CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) mechanism, both of which increase the relative cost of fossil jet fuel and recognise SAF as a key emissions-reduction tool.
On the supply side, capital programmes such as the Advanced Fuels Fund (AFF) help de-risk early commercial projects, while the government’s forthcoming Revenue Certainty Mechanism (RCM) is designed to stabilise long-term SAF pricing and give investors confidence in new production facilities. The UK SAF Mandate ties these elements together by creating guaranteed demand through a main obligation on airlines, a dedicated power-to-liquid (PtL) sub-obligation to drive ultra-low-carbon fuels, and a HEFA cap to drive feedstock and technology diversity. Together, these policies form an integrated ecosystem capable of turning seasonal waste into a meaningful contributor to net zero aviation.
Further reading
www.gov.uk/government/news/24-ways-to-waste-not-this-christmas
Review of technological developments and LCA applications on biobased SAF conversion processes www.frontiersin.org/journals/fuels/articles/10.3389/ffuel.2024.1397962/full
About the authors
Rory Hannah, Krishnikha Ananthakrishnan are final-year project students (MEng, Aero Engineering) working on SAF production pathway study using process modelling and TEA/LCA analysis. Eleanor Borrill is a second-year PhD student whose topic is on combustion and supply chain study of SAF, with a particular focus on the waste feedstock. Their work is overseen by Ruoyang Yuan, University of Sheffield.
Quiz answers
1 – Fischer-Tropsch
Gasification +Fischer-Tropsch is the preferred pathway, as it’s usually more efficient, but alcohol-to-jet can also be used.
2 – HEFA
HEFA can only take oil as a feedstock, so waste oil from cooking can be used. The rest of the food can be used in gasification +Fischer-Tropsch or alcohol-to-jet.
3 – Fischer-Tropsch
Gasification +Fischer-Tropsch is the preferred pathway, but alcohol-to-jet can also be used.
4 – Alcohol-to-Jet/HEFA
Alcohol-to-jet only (beer and low alcohol content drinks cannot be used, only high alcohol content e.g. vodka could be used if you extract the ethanol). HEFA cannot be used for this.
5 – Fischer-Tropsch
Gasification +Fischer-Tropsch is the preferred pathway, but alcohol-to-jet can also be used.
6 – Fischer-Tropsch
The preferred pathway for waste plastic is fast pyrolysis but gasification +Fischer-Tropsch could potentially be used.
