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Note: This article was AI-translated from Arabic and is currently under manual review. The author is not responsible for any translation errors. Please refer to the original Arabic text for the most accurate and authoritative information.
Used cooking oil becomes a circular-economy resource when it is collected in an organised way, kept separate from the food chain, and converted in qualified facilities into products that meet specifications. The real value of this resource starts with safe collection, documented origin, oil analysis, and choosing the right conversion pathway.
It is the oils and fats left over from cooking and frying in homes, restaurants, hotels and food factories. Its properties vary with the type of original oil, how long it was used, the temperature, the nature of the food, and the amounts of water and food residues mixed into it.
During heating, the oil's components change through oxidation, hydrolysis and polymerisation reactions. Analytical indicators, including total polar compounds, are therefore used to assess frying-oil deterioration. Colour alone is not enough to judge whether the oil is still fit for use or how far it has deteriorated.
Two separate decisions must be kept apart: the end of the oil's suitability for food use, and its acceptance as a feedstock for industrial conversion. Each decision has its own tests and requirements.
A documented collection system takes discarded oils out of food circulation and directs them to defined industrial uses. India's RUCO programme offers a regulatory example that links used-oil collection with its conversion into biodiesel and limits its return to the food chain.
India sets a total polar compounds limit of 25%, beyond which the oil is no longer fit for food use. This is an Indian regulatory value and is not presented as a uniform legal limit in Iraq or in all countries; the applicable local requirements should be reviewed. From a quality standpoint, filtering deteriorated oil or removing its odour is not proof that it has regained its food suitability.
The International Civil Aviation Organization (ICAO) lists used cooking oils among HEFA feedstocks under Annex A2 of ASTM D7566, with a blending limit of up to 50% for this pathway, provided fuel requirements are met. This is an approved blending ratio, not the yield of converting oil into jet fuel.
We propose a documented route that starts when oil is withdrawn from frying and ends with its handover to a qualified party. It includes:
These are suggested measures for designing the system and should be adapted to the environmental licensing and waste management requirements of the country where they are applied.
A mass balance is also used to check that the records are plausible, by comparing the quantities of oil purchased and added to the fryers with what was absorbed by the food, what remains, and what was handed over for recycling.
Before conversion, representative samples are taken to characterise each batch. Pre-treatment should include removing food residues, suspended matter and water, then preparing the oil to the converter's specification. No single operating recipe fits all used cooking oils; differences in acidity, water and impurities can change the treatment requirements. Research shows that free fatty acids can be pre-treated before completing the conversion of used cooking oil into biodiesel.
Producing aviation fuel, on the other hand, requires specialised processing plants, hydrogen supply, catalysts, product separation and certification testing. It should therefore not be treated as a simple extension of oil filtration.
We suggest keeping the incoming-oil analysis programme separate from the finished-fuel testing programme. For used cooking oil, the basic tests include acid value, moisture content and insoluble impurities, with further tests added according to the plant's requirements, such as fatty acid composition and elements or contaminants that affect the process.
ISO 660:2020 specifies methods for determining the acid value and acidity of oils and fats. Acid value is usually expressed as the amount of potassium hydroxide needed to neutralise the acids in one gram of sample.
Reference analytical methods for oils include insoluble impurities by ISO 663 and polar compounds by ISO 8420. The method is chosen to suit the purpose of the measurement and the type of sample. Authenticity of origin cannot be inferred from a single test; results must be linked to records, the chain of custody and the mass balance.
Completing the chemical reaction is not enough to release the fuel. Biodiesel evaluation includes viscosity, acid number, water and sediment, free and total glycerol, methanol control, flash point, oxidation stability and residual elements.
Examples from the U.S. Department of Energy's summary of B100 requirements: a maximum acid number of 0.50 mg KOH/g, free glycerol of 0.020% by mass, and total glycerol of 0.240% by mass. The full specification and its current edition should be reviewed when setting release limits, as the summary does not cover all of its requirements. Filtered cooking oil is not used directly as biodiesel; its viscosity and properties are different, and it can cause deposits and operating problems in engines.
Technical compliance of a fuel and its sustainability are related, but they require different evidence. Eligibility under CORSIA requires meeting sustainability criteria and a life-cycle emissions assessment, in addition to documenting the feedstock and supply chain. The environmental impact depends on the energy and hydrogen source, collection and transport distances, conversion efficiency and by-product management. A single emissions-reduction figure therefore cannot be attributed to all used-oil projects.
The International Energy Agency (IEA) notes that competition between producers of biodiesel, renewable diesel and aviation fuel is putting pressure on the available supply of oils and fats. A feasibility study should therefore be built on feedstock that can actually be collected consistently, with its costs and quality taken into account.
A food plant can start with a documented collection and handover programme before considering a conversion unit. We suggest assessing the monthly quantity available, the share of water and impurities, storage and transport costs, the buyer's specification, and rejection cases.
For arithmetic illustration only: if 1,000 kg of oil is collected and 5% water and impurities are removed, 950 kg of treated feedstock remains. This does not mean 950 kg of aviation fuel will be produced; the yield varies with the technology and the product slate.
In Egypt, a platform affiliated with the Ministry of Environment lists an investment opportunity to collect 10,000 tonnes per year of used cooking oil through a licensed company, with options to export it or produce biodiesel. This describes a proposed project and is not proof of quantities actually achieved.
The quality of the system is measured by its ability to take oil out of food use, keep it traceable, deliver it to known specifications, and convert it into a certified product with economic value and a documented environmental impact.