Milorganite is exactly that, it's composed of heat-dried microbes that have digested the organic material in wastewater. It's manufactured by the Milwaukee Metropolitan Sewerage District, which captures waste water from the metropolitan Milwaukee area and uses naturally occurring microbes to digest the nutrients. After the organic matter has been consumed, the cleaned water is returned to Lake Michigan and the resulting material is dried and marketed as Milorganite®.
The problem with human waste is the concentration of heavy metals as I understand it. We are the very top of the food chain and we accumulate all of the heavy metals from below which then gets further concentrated in our dried waste.
