The three products are made from the same lipid pool but by different chemistry, and that chemistry determines everything downstream: what specification applies, how much can be blended, how it stores, and what it costs.
Fatty acid methyl ester is made by reacting oil or fat with methanol in the presence of a catalyst, giving an oxygenated ester plus glycerine as a co-product. It is specified under EN 14214 in Europe and ASTM D6751 in the United States, and it is limited by fuel standards and vehicle warranties to a blend percentage, typically 7% in road diesel.
Hydrotreated vegetable oil is made by reacting the lipid with hydrogen, removing the oxygen and producing a paraffinic hydrocarbon very similar to fossil diesel. It meets EN 15940, has a cetane number around 70 to 90, stores well, and can be used neat as a drop-in fuel with no blending ceiling.
Sustainable aviation fuel follows the same hydroprocessing route as HVO — the HEFA pathway — but then isomerises and fractionates the product into the kerosene range. It must meet ASTM D7566, a much tighter specification than road diesel, and is blended up to 50% with conventional jet fuel.
All three draw on the same waste lipids — used cooking oil, POME-derived oil and tallow. That shared pool is the central tension in the market: road transport mandates and aviation mandates are bidding against each other for a feedstock supply that grows slowly, which is why HVO and SAF both command large premiums over fossil fuel.
No. HVO is a drop-in paraffinic fuel that can replace fossil diesel entirely, while FAME is an oxygenated ester limited to a blend percentage by fuel standards and by most vehicle warranties. They can be blended with each other and with fossil diesel, but they are not equivalent products.
Because hydrotreating requires hydrogen, high pressure and considerably more capital per tonne of output than transesterification, and because the drop-in specification value is higher. The feedstock is the same; the conversion step is what costs more.
Chemically it is close — both are HEFA products from hydrotreating a lipid — but SAF must additionally be isomerised for cold flow at altitude and fractionated into the kerosene range, and it must be certified to ASTM D7566, a far tighter specification than EN 15940.
All three deliver savings relative to fossil fuel, and the size of the saving is driven mainly by the feedstock rather than by the process. Waste and residue feedstocks such as UCO and POME oil give the strongest lifecycle savings and are what mandates incentivise.
No. Glycerine is the co-product of FAME transesterification. Hydrotreating breaks the triglyceride down into paraffins, propane and water instead, which is one reason HVO plants have a different co-product and by-product profile from biodiesel plants.
