Thank you for your knowledgeable comment. We have two answers: (1) we have no easy access to a high phosphorous, high sulfur charging agent, while we live virtually next to a commercial pig farm and (2) pig pee from commercially raised pigs is chock full of both macro and micro nutrients and adsorb to biochar and are needed in poor soils. Like humans that take lots of vitamins, pigs fed on high mineral, commercial feed pee out the overload. Good commercial feeds contain macronutrients such as calcium, phosphorous, sodium and chloride and micronutrients such as zinc, copper, iron, manganese, iodine and selenium, all of which show up in commercial pig pee. As you note, all pig pee also provides a lot of macronutrients nitrogen and potassium. In the developing world, urine or any sort, including human, is an excellent and readily available source of N, P, K and many micronutrients, depending on the source and the source’s nutritional status. At Warm Heart, our motto is “Go with the best you have, if it is better than nothing.” We are sad to say, it almost always is.