Compartmental process-based model for estimating ammonia emission from liquid dairy manure storage tank

Abstract.

The biogeochemical processes responsible for production and emission of ammonia from stored liquid dairy manure are governed by environmental factors (e.g. manure temperature, moisture) and manure characteristics (e.g. total ammoniacal nitrogen concentration, pH). These environmental factors and manure characteristics vary spatially as a result of spatially heterogeneous physical, chemical, and biological properties of manure. Existing process-based models used for estimating ammonia emission do not consider these spatial variations leading to inaccurate estimations. In this study, a one-dimensional compartmental process-based model was developed to (i) estimate spatial variation of temperature and substrate concentration (ii) estimate spatial variations and rates of biogeochemical processes, and (iii) estimate production and emission of ammonia from a liquid manure storage tank. Model performance was evaluated using experimental data obtained from National Air Emissions Monitoring Study. A sensitivity analysis was performed and air temperature, manure pH, wind speed, and manure total ammoniacal nitrogen concentration were identified as the most sensitive model inputs. The model was used to estimate ammonia emission from a liquid dairy manure storage of a dairy farm located in Rockingham County in Virginia. Ammonia emission was estimated under different management and weather scenarios: two different manure storage periods in cold season from November to April and in warm season from May to October using historical weather data of the Rockingham County. Results suggest greater ammonia emission and manure nitrogen loss for the manure storage period in warm season compared to the storage period in cold season.