Food Waste and Catering Waste; Focus on Valorisation of Used Cooking Oil and Recovered Triglycerides - The Economic Utilisation of Food Co-Products - page 106

upon frying leading to an increase in the FFA content and polymerisation
reactions, which could be overcome by the introduction of functionalities in
the carbon chain of the parent oil (epoxydation, 85 ozonolysis/ introduction of
carboxylic groups to increase hydrophilic properties of paints, insertion of
olefins, etc.). 86

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6.5.4.5 Fabric Softeners
Various applications have also been found for the use of recovered oils and
fabric softeners. Recovered rapeseed and palm oil can be used. The oil is
converted either into amides or ethoxylates and produces a high-quality fabric
softener.

d y y f n n 3 .

6.6 Soapstocks; By-products from Oil Refining,
Recovered Triglycerides and UCO-derived Biodiesel

6.6.1 Introduction
Edible oil purification, biodiesel production, AOCHE production and pulp
milling processing all generate coproducts of variable composition that are
generally regarded as soaps or soapstocks. 87 These result from a combination
of various streams in an oil refinery (caustic neutralisation, transesterification,
euent disposal, deodorising) 88 and require further processing in order to
recover valuable components. Some of these components are free fatty acids,
triglycerides, nonsaponifiable matter, 89 different grades of glycerine, 90 and tall
oils in the case of paper-pulp refining. Therefore soapstocks can be considered
both as pre-consumer and post-consumer FSCW/FW, for oil refining and
UCO-biodiesel processing respectively. 91
Crude oils from the seed crushing/ purification process, for instance, contain
variable amounts of gums, colour-impairing bodies and fatty acids. 92 In one of
the steps in the purification process, oil is treated with a caustic solution in
order to achieve fatty acid removal. During the process, fatty acids are
converted into soaps and part of the neutral oil, glycerides and phospholipids,
are also saponified, generating soapstocks with a relatively high carboxylate
content that can form stable emulsions. 93 These soapstocks from oil refining are
generated at a rate of around 6% to the oil produced, 94 where in biodiesel
production from UCO soap produced can be up to 45 wt% to the feed. 95 There
are different soapstock treatment methods, for instance the use of mineral acid
and/or solvent treatment followed by phase separation as shown in Figure 6.12
which has been a common approach in industry. This method is relevant to the
current work since it resembles the approach taken in the biodiesel soap
treatment for fatty material and glycerine recovery (Figure 6.13). 96
The end uses of the fractions recovered from various soapstock refining
processes are diverse. Use as an animal feed component 97 is the most common,
however, no less important are their utilisation as biofuel precursors, 98

in the