I originally posted this on the wrong thread... I'm an idiot!!!
OK - I just looked into it a little bit...
While stearic acid is a fatty acid derived from animal fat, it can also be synthesized from hydrogenating certain vegetable oils.
Hydrogenation is the process of forcing hydrogen atoms into the "holes" (double bonds) of unsaturated fatty acids. It's usually done with hydrogen gas and a metal catalyst at higher temperatures.
For example, one can hydrogenate alpa-linolenic acid (one of the good omega-3-fatty acids in fish)to get stearic acid.
Of course, a drawback to manufacturing stearic acid this way may be traces of the metal catalyst used in hydrogenation that cannot be removed.
I really can't find anywhere (at the moment) any definite answer about the manufacturing process used to make stearic acid for cosmietic/emulsifier purposes.