Sustainable Aviation Fuel (SAF) is a critical solution for reducing the carbon footprint of air travel.
To qualify for SAF certification under international standards such as ASTM D7566, CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation), and the EU Renewable Energy Directive II (RED II), feedstocks must demonstrate sustainability and significant lifecycle greenhouse gas (GHG) reductions. Here Haush outlines the key biomass and waste feedstocks used for SAF production, along with regional availability in Australasia, Europe, and the USA.
Biomass Feedstocks
Biomass feedstocks consist of renewable organic materials derived from plants and agricultural residues. These are categorised into lipid-based feedstocks, lignocellulosic biomass, and algal biomass.
Lipid-Based Feedstocks (Oils and Fats)
- Used Cooking Oil (UCO) – Recovered from restaurants and food processing industries.
- Animal Fats (Tallow, Poultry Fat, etc.) – By-products of meat processing.
- Non-Edible Plant Oils – Includes oils from Jatropha, Camelina, Carinata, and Pongamia.
- Palm Fatty Acid Distillate (PFAD) – A by-product of palm oil refining, subject to strict sustainability criteria.
Regional Availability
- Australasia: Tallow and UCO from Australia and New Zealand’s livestock and food industries.
- Europe: Rapeseed and UCO from extensive food processing operations.
- USA: Soybean oil and UCO from major fast-food chains and agricultural production.
Lignocellulosic Biomass
- Agricultural Residues – Corn stover, wheat straw, sugarcane bagasse, rice husks.
- Forestry Residues – Sawdust, wood chips, branches, and logging residues.
- Dedicated Energy Crops – Miscanthus, switchgrass, hybrid poplar, willow.
Regional Availability
- Australasia: Sugarcane bagasse (Queensland, Australia), wheat straw (New Zealand).
- Europe: Wheat straw (France, Germany, UK), forestry residues (Sweden, Finland).
- USA: Corn stover (Midwest), switchgrass (Great Plains region), forestry residues (Pacific Northwest).
Algal Biomass
- Microalgae and Macroalgae – Cultivated in controlled environments or harvested from the ocean.
Regional Availability
- Australasia: Emerging production in Australia’s coastal regions.
- Europe: Algae farms in the Netherlands, France, and Spain.
- USA: Research and pilot projects in California, Florida, and Hawaii.
Waste Materials (Domestic and Industrial)
Waste-based feedstocks offer a highly sustainable alternative as they utilise by-products that would otherwise contribute to pollution.
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Municipal Solid Waste (MSW)
- Organic Fraction of MSW – Includes food waste, paper, and yard waste, separated from non-biodegradable materials.
Regional Availability
- Australasia: Waste-to-energy projects in Australia’s major cities.
- Europe: Advanced waste separation and biofuel conversion in Germany and the UK.
- USA: Large-scale MSW-to-biofuel projects in California and Texas.
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Industrial Waste Gases
- Carbon-Rich Emissions – Captured from steel mills, refineries, and chemical plants.
Regional Availability
- Australasia: Limited but growing potential in Australia’s industrial zones.
- Europe: Pioneering projects in the UK, Sweden, and Germany.
- USA: Steel mill waste gas conversion projects in Pennsylvania and Illinois.
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Waste Plastics (Emerging Technology)
- Advanced Pyrolysis of Post-Consumer Plastics – Converts plastic waste into synthetic crude suitable for SAF.
Regional Availability
- Australasia: R&D projects in Australia and New Zealand.
- Europe: Emerging circular economy initiatives in Scandinavia and Germany.
- USA: Pilot projects in Texas and California.
Approved SAF Production Pathways
Internationally certified pathways for SAF production include:
- HEFA (Hydroprocessed Esters and Fatty Acids) – Converts fats, oils, and greases.
- FT-SPK (Fischer-Tropsch Synthesized Paraffinic Kerosene) – Uses lignocellulosic biomass or waste gases.
- ATJ-SPK (Alcohol-to-Jet) – Converts alcohols (e.g., ethanol, isobutanol) from biomass.
- CHJ (Catalytic Hydrothermolysis Jet) – Processes lipids into jet fuel.
- FT-SPK/A (Fischer-Tropsch with Aromatics) – Produces synthetic kerosene with aromatics.
- SIP (Synthesized Iso-Paraffins) – Derives fuel from sugars via fermentation.
Certification and Sustainability Requirements
To qualify as sustainable, SAF feedstocks must meet the following criteria:
- Lifecycle GHG Reduction – A minimum of 50% reduction compared to conventional jet fuel (varies by region).
- Land-Use and Biodiversity Protection – Feedstocks must not come from deforested or high-biodiversity areas post-2008.
- Traceability and Chain of Custody – Compliance with sustainability standards such as ISCC (International Sustainability and Carbon Certification) and RSB (Roundtable on Sustainable Biomaterials).
The Future
The diversification of SAF feedstocks is key to scaling up production and reducing aviation emissions. Regional availability of biomass and waste materials plays a crucial role in determining the most viable pathways. By leveraging existing agricultural residues, industrial waste, and emerging technologies, the aviation industry can transition towards a more sustainable future.
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