Chemical composition of animal manure: a modelling approach.

A chemical equilibrium program (CHARON) was used to predict the chemical composition of the liquid fraction and the mineral fraction of pig and poultry manure. The results showed that the major part of calcium and magnesium in solution is complexed by dissolved organic matter. A large part of the dissolved organic matter is complexed with ammonium and potassium ions. Calculated ion activity products showed that possible mineral phases include vaterite, whitlockite, monetite and struvite in all the samples, and potassium taranakite in the pig manure samples. A number of other minerals are either unsaturated or so strongly supersaturated (e.g. apatite), that they do not control the solubility of major cations and anions. Scanning electron microscopy/microprobe analysis showed the abundant presence of a magnesium phosphate, most likely the mineral struvite (MgNH4PO4.6H2O) in one of the pig manure samples. (Abstract retrieved from CAB Abstracts by CABI’s permission)