Environmental concerns and biofuel policies have contributed
to a significant increase in global biodiesel production.
Biodiesel is produced by the transesterification of
vegetable oils or animal fats with an alcohol, usually
methanol, in the presence of a catalyst. In the reaction a
large amount of glycerin is obtained as a by-product,
approximately 10% by weight of the biodiesel produced
(Thompson and He, 2006). In recent years, the surplus of
crude glycerin has led researchers to look for new ways of
using this by-product, one of which may be as a costcompetitive
feedstuff. In fact, several researchers have
determined that crude glycerin is a good alternative as a
feed ingredient for swine (Kijora et al., 1995; Lammers
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