Used Cooking Oil (UCO) — Frequently Asked Questions

Most traded UCO sits between about 2 % and 10 % FFA expressed as oleic acid, and many contracts use 5 % maximum as the basis, with price adjustments or rejection above it. The right figure depends on your process: a biodiesel plant with limited acid esterification capacity needs a tighter limit, while an HVO or SAF unit converts FFA directly but must manage the corrosivity of high-acid oil in tanks and lines.

MIU groups moisture, insoluble impurities and unsaponifiable matter, the fraction of the oil that adds no fuel value. Contracts commonly cap it at 2–3 %, sometimes with a separate limit of about 1 % on moisture and impurities combined. Some buyers pay on a net-weight basis and deduct MIU above the agreed threshold, so name the test methods, for example Karl Fischer titration for water and ISO 663 for insoluble impurities.

Polyethylene from packaging and frying equipment can dissolve in hot oil and is not removed by conventional bleaching, so it can foul hydrotreater preheaters and catalysts. Chlorine, from salt and some food residues, forms corrosive compounds in the reactor section. Neither parameter matters much to a FAME plant, which is why HVO and SAF contracts often add mg/kg limits that biodiesel contracts omit.

UCO is generally discussed as the main Annex IX Part B feedstock under the EU Renewable Energy Directive, alongside category 1 and 2 animal fats. Its contribution to transport targets is capped, and national rules, multipliers and reporting obligations differ between Member States and the UK. Confirm the accepted category and the certificate scope for the specific lot with your certification body before contracting.

UCO settles in storage, with water and solids concentrating near the bottom, so a sample taken from the top can understate MIU. Draw composite samples through the full depth of every tank, compartment or flexitank, seal and retain them until the lot is accepted, and name an independent referee laboratory in advance. Agree beforehand whether the loading or the discharge analysis governs.

State the conversion route (FAME, HVO or SAF), your FFA and MIU basis and rejection limits, any contaminant limits in mg/kg, preferred test methods, volume per month or per shipment, packaging (flexitank, ISO tank or bulk), delivery point and Incoterm, and the sustainability documents your market requires. This lets the lot analysis and available documentation be checked against your needs before a quotation is issued.