A COMPUTER-MODEL FOR PREDICTING AMMONIA RELEASE RATES FROM SWINE MANURE PITS

This paper presents a computer model for predicting ammonia release ra tes from manure pits in swine buildings. The model couples ammonia dif fusion and generation in the manure with ammonia release from the manu re surface. Ammonia release rates and concentration profiles in the ma nure are computed over a storage period for given pit designs, manure properties, and pit environmental conditions. As an example, computer simulations were performed for a pit designed with a final manure dept h of 1.0 m in finishing swine buildings, operated at 1-8% initial tota l solids content in the manure, two temperatures (20 and 30-degrees-C) , and three velocities 2 cm above the manure surface (0, 0.2 and 0.5 m s-1). The results show that air velocity and manure temperature have s ignificant effects on ammonia release rates. Lower layers of manure in the pit have lower pH, higher ammoniacal nitrogen, and higher nutrien ts than the higher layers.