Prospects for the recovery of phosphorus from animal manures: A review

This paper reviews the potential for phosphorus (P) recovery from animal ma nures as a method of increasing the sustainability of the global P cycle. T he P content of animal manures produced annually in the UK is currently est imated at over 120,000 t. This represents approximately twice the annual no n-agricultural P requirement in the UK and has an approximate value of poun d 76 M. Similar quantities of P are produced in manures in the Netherlands and an estimated 600 500 t are produced annually in the US. Up to 65% of ma nure P may be associated with an organic moiety. However, current methods t o identify these including HPLC and P-31 NMR are under-developed while P fr actionation procedures give only operational definitions. Combinations of c urrent technologies developed for the treatment of sewage are likely to pro ve effective in the recovery of P from manures. Enhanced Biological Phospho rus Removal (EBPR) could he adapted to produce a concentrated P effluent. R ecovery of P from which could be achieved by either of two crystallisation pathways to produce magnesium ammonium phosphate (struvite) or calcium phos phate (apatite). Recycling of manure P to land within the agricultural sect or remains the best option in many cases. However, manure production in man y areas such as Chesapeake Bay and the Everglades in North America, the Po Delta in Italy and the sand regions of the Netherlands is too intensive for locally available land to accommodate without the risk of transfer to surf ace waters. Legislation restricting recycling of P to land already exists i n the Netherlands and is likely to become widely adopted. Under these circu mstances recovery of P may alleviate manure management problems.