(94e) Characterization of Used Cooking Oils and Their Supply Chain for the Exploitation As Raw Materials in Urban Biorefineries

In recent years, the chemical industry has focused its efforts on the sustainable generation of chemical products derived from renewable and sustainable resources (biobased chemicals) (1). This trend has pushed the oleochemical industry to exploit alternative raw materials that are not suitable for human consumption (second generation) such as used cooking oils (UCOs). Because these are waste materials, they do not compete in the market with edible oils and fats (reducing pressure on food prices and land use), are low cost, have a large volume of production, and can maintain a sustainable supply under a circular economy concept. In particular, UCOs are generated in large volumes, mainly in urban centers, making them suitable feedstock for urban biorefineries.

After impurities removal and refining, the UCOs become an oleochemical platform for the production of commodity biobased fuels (e.g. biodiesel (2,3)), but more importantly, valued added products. UCOs can be used as building block for the synthesis of valuable biobased products such as monomers, additives for polymers and resins, surfactants, etc (4,5). In particular, production of polyurethane monomers (polyols and non-isocyanate moieties) is of major interest in the near future(6). However, there is a major limitation when using UCOs as feedstock associated to the chemical heterogeneity. UCOs composition largely varies with the nature of original virgin oil, the conditions during the cooking process (processed food, fryer type, temperature, processing time, etc.), and the refining process (7,8).

In order to assess the feasibility of using UCOs as feedstock for urban biorefineries in the production of value-added chemicals, this work developed a method to characterize UCOs and their supply chain in a typical urban center (Bogota, Colombia). The studied supply chain corresponded to food establishments because they are larger UCOs generators compared with industrial users (e. g. snack producers). Initially the UCOs supply spots were classified according to the following categories: institutional food, fast food, casual food, and tablecloth restaurants (9,10). UCOs were obtained from the categories with the largest outlets across the city. The physicochemical characterization of representative samples collected around the city was done by evaluation of iodine value, acid value, moisture, density, saponification value, peroxide value and total polar compounds.

A pilot test was performed to evaluate the chemical heterogeneity of UCOs obtained from each category around the city. According to results, the density of samples presented low coefficient of variation (0,5%) as this property barely changes during oil processing. On the other hand, properties such as iodine value and saponification value presented a coefficient of variation around 14%, indicating that these properties do not change much among the different categories. Finally, properties such as moisture, acid value, peroxide value and total polar compounds presented high coefficient of variation (55%). This indicate that these properties largely depend on the type of food establishment, and that UCOs originated from each supplier might need a specific refining process. Properties characterized with high coefficient of variation were used to stablish the required processing conditions for UCOs refining (11).

Iodine and saponification values were of special interest because they are surrogate variables that determines the potential use of UCOs as oleochemical feedstock. Thus, the ranges of iodine values and saponification index of UCOS collected in the city of Bogota were 85-105 g I₂/100 g, and 130-201 mg KOH/g respectively. According to these results UCOs can be used as raw materials for epoxidized oils and subsequently for the ring-opening reaction to biobased polyols (12,13). As some suppliers produced highly saturated UCOs, it is necessary to avoid their blending with UCOs from different categories in the central collection depots. Instead, they can be separately processed and be used for the production biofuels, surfactants, or other additives for commodity plastics (such as PVC) (14,15).

References

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