Inedible

Question

Dear Rabbi Abadi, You often rely on your analysis of an ingredient being inedible, to permit it such as oleic acid, myristic acid,non-kosher release agent,whey powder,etc. However as Rav Shlomo Zalman Auerbach points out, it is not so simple to declare something as not edible& no longer a food. The SA YD 81 says that urine of a non kosher animal such as a donkey,is non-kosher. How edible would you consider that?