Abstract
Waste fish oils (FOs) and used cooking vegetable oils (UCOs) are increasingly becoming alternative renewable fuels. However, different physicochemical aspects of these renewable fuels, including the effect of storage, are not well-known. In this work, the effect of the storage period on physicochemical properties of selected samples of FOs and UCOs was investigated. The bio-oils were stored at 4 °C for up to five years before each experimentation. The chemical properties were characterized using capillary gas chromatography with flame ionization detection (GC-FID) and high-performance size exclusion chromatography including an evaporative light scattering detector (HPSEC-ELSD). Water contents and acid numbers of the bio-oils were determined using the Karl Fischer (KF) titration and the ASTM D 664 methods. Furthermore, the average heating values and surface tension of the bio-oils were determined. According to the results obtained, for all bio-oil types, the concentrations of polymerized triglycerides, diglycerides, and fatty acids and monoglycerides had increased during the storage periods. The physical properties of the bio-oils also showed a small variation as a function of the storage period. The overall results observed indicate that the deterioration of the physicochemical properties of bio-oils can be controlled through storage in dark, dry, and cold conditions.
Highlights
Used cooking vegetable oils (UCOs) and waste fish oils (FOs) are of increasing interest as economic feedstock for bio-oils or biodiesel production
The FOs were produced from the gutting remains of rainbow trout after extracting the edible oil, while the filtered UCOs originated from frying vegetable oils used in restaurants
After five years storage period, greater changes about 4.3% were measured in the composition of the polymerized triglycerides in FOs than in UCOs
Summary
Used cooking vegetable oils (UCOs) and waste fish oils (FOs) are of increasing interest as economic feedstock for bio-oils or biodiesel production. Compared to petroleum based oils, they are more eco-friendly [1,2,3,4,5,6,7,8]. They have limited oxidative stability as their source is, i.e., fresh vegetable oils [3]. The usage of waste-derived oils, not in the food production chain, offers a feasible way to increase the share of carbonneutral fuel alternatives. According to the revised Sulfur Directive, since the beginning of 2020, maximum sulfur content of marine fuels is reduced to 0.5%, i.e., down from the 2012 Sulfur Directive limit 3.5%, globally [9]
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