Glycerol can be derived from animal and vegetable fats as well as synthesis. Synthesis was the increasingly more common way of obtaining it until biodiesel became popular, which yields a significant amount of glycerol as a byproduct. Falling prices for the commodity hints at supply being abundant due to these factors and thus I expect it is unlikely that producers have to resort to the saponification of animal fats to create it. Regardless, glycerol as a compound will be identical no matter the method of its manufacture and as such will not yield an objective difference for our purposes either way.
There is a large quantity of food-grade vegetable glycerine at the very reasonable price of $7.