Glycerol, What?

Breakfast was same as yesterday, lightly toasted whole wheat bread with peanut butter. Ingredients weren't available for the peanut butter, but they wouldn't put animal fats in that, would they?  At work I snacked on some Arrowroot biscuits from my flight bag, but now that I look at the ingredients list I see glycerol listed.  Okay first: weird. What is glycerol doing in my biscuits? And then it's hard to know where it came from. Some is produced as a byproduct of soapmaking from animal fats, some is a byproduct of making diesel fuel out of crude oil that presumably was biological several million years ago, and some is a byproduct of the production of cooking and salad oils. The Wikipedia article suggests that only the result of the last process is considered safe for human ingestion, so I think that means that these arrowroot biscuits are okay for vegans.