Would it be possible to convert the manure of zoo animals into a biological ressource? It could for instance be converted to biogas and sold - or used as fuel for rides in the zoo. It could also be composted and sold as fertilizer. Or it could go through pyrolysis and be sold/used as biochar (very good and entirely clean plant nutrition) as well as fuel gasses. What do you think? Or do you have an idea how animal manure could be manufactured to make it a ressource rather than high-expense trash? I'm looking forward to hear your responses!