Mathematical model to predict ammonia emission from in-house windrowing of poultry litter

Abstract

In&-house windrowing between flocks is an emerging sanitary management practice to partially disinfect the built-up litter in broiler houses. Windrowing litter results in high litter temperatures that can reduce the risk of transmitting pathogens to next flock. Simultaneously, this practice may also increase ammonia (NH3) emission from the litter because NH3 in the litter volatilizes to the atmosphere more rapidly at higher litter temperature. However, windrowing litter also reduces the total surface area exposed to the atmosphere, thus reducing the house emission rate to certain extent. In this study, we developed mathematical models to determine mass transfer area of litter when the litter is windrowed to triangular- and rectangular-prismatic, and semi-cylindrical shapes. Using these models, the heights of windrows yielding the smallest mass transfer area were estimated. Smaller mass transfer area is preferred as it reduces both emission rates and heat loss. The heights yielding the minimum mass transfer area were 0.8 and 0.5 m for triangular and rectangular prismatic windrows, respectively. Only one height (0.6 m) was theoretically possible for semi-cylindrical windrows because the base and the height were not independent. Above mass-transfer area predicting models were then integrated with published process-based mathematical models to predict the total house NH3 emission rates from the in-house windrowing of poultry litter.