An off comment, I well remember my mother making soap out of lard, lye, and water in a big cast iron soap kettle over a wood fire.
Yep, and that is one thing you need to be wary of. It's easy to make soap instead of biodiesel. After the reaction is done we take and mix the
diesel with water. The product floats to the top and any soap or impurities get removed by the water.