Food Waste and Catering Waste; Focus on Valorisation of Used Cooking Oil and Recovered Triglycerides - The Economic Utilisation of Food Co-Products - page 103

For instance, products such as surfactants, lubricants, coatings, polymers
have been generated from either food or nonfood triglycerides and fatty
acids. Selected examples reported the use of vegetable oils and fats in lubri-
cation, 70 paints and drying applications, 71 which can potentially be econ-
omically attractive and sustainable ''end-of-waste'' routes for UCO and
recovered fats. 72

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6.5.4.1 Vegetable Oil, Fats and UCOs as Lubricants
Biorenewable, nonhazardous and biodegradable components for lubrication
are expected to considerably increase in future years, driven by environmental
and health concerns (toxicity, not being readily biodegradable, etc.) as well as
by the large demand of mineral-based lubricants worldwide (37.5million
tonnes/year). 73
Vegetable oils, greases and fats either neat, in blends, as well as chemically
modified, or with additives have become a promising alternative to mineral-
and synthetic-based oils with a large number of examples reported in
literature. 74 The preferred applications for vegetable oils in lubrications are
those in which thermal/oxidative stability is not a critical issue. These include
cutting fluids, 75 low working temperature hydraulic fluids 76 and others.
Although the reported examples for UCO as a lubricant are limited 77 due to
their physicochemical properties particularly related to thermal and oxidative
stabilities.
However, additives are required to improve oxidative stability and viscosity
at high and low temperatures to achieve a similar performance to those of their
synthetic/mineral equivalents. These include anti-wearing agents (zinc dial-
kyldithiophosphates: ZDDPs), antioxidants (hindered phenols, aromatic
amines and others), detergent/dispersants (sulfonates, salicylates and others)
etc.) chemical modification, 78 (i.e. improvements in thermal/oxidative stability,
viscosity modification boundary lubrication, etc.), deodorisation 79 (via distil-
lation to improve flash point properties) and/or blending with mineral products
to meet the specifications. 80
Research in this area is needed to achieve further developments. For
instance, the free fatty acids available in large amounts of acid oils/UCOs could
be rectified by conversion into soaps, amides (i.e. partial emulsification of water
in cutting fluids), fatty acid alkyl esters (FAAE) or neopentyl triol esters
(resulting in increased thermal/oxidative stability in hydrolic fluids). 81 Other
modifications likely to improve properties such as viscosity index or oxidative
stability are conversion into estolides, 82

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epoxidation and partial oxidation

(Scheme 6.3).
In summary, UCOs and derivatives have significant potential to become
environmentally friendly alternatives to mineral-based lubricants, with low
volatility, high viscosity index, high biodegradability and lower production
costs. The utilisation of UCO in this area is, however, not free of challenges,
due to variability of composition and lower oxidative and thermal stability in
comparison to currently available virgin oils and mineral products.