GREENHOUSE GAS EMISSION AND NUTRIENT FATE ON DAIRY CONFINED ANIMAL FEEDING OPERATIONS

Tariq Mahmood Khalil

Concentrated animal feeding operations (CAFOs) are undergoing scrutiny in regard to manure management and nutrient flow, with a focus on specific environmental concerns related to greenhouse gas emissions, impact on air quality, and water pollution. The goal of this research was to investigate gaseous emissions and nutrient fate on dairy CAFOs through experimental and model studies. The impact of manure treatments on carbon kinetics was investigated in a laboratory study. Results showed that the decomposition rate constant (k) of untreated manure was significantly different from treated manure effluents. An empirical model was developed to predict k values of manure that had been subjected to various processing treatments and thus had variable biochemical composition. The developed model’s carbon mineralization subroutine was improved by using manure-specific k values instead of typical k which ignore the effects of different manure treatments. The development of Dairy-CropSyst, a decision support tool for gaseous emission and manure nutrient fate from animal, barn, lagoon, and manure field application was completed. The model has the capability to simulate the effect of existing and emerging manure treatments including anaerobic digestion, solids separation, and ammoniacal nitrogen recovery. Model outputs may assist the dairy industry by aiding in decision making on gaseous emissions, soil nutrient status, animal-to-land ratio, and recovery of value-added products from manure. Dairy-CropSyst performance was evaluated by comparing model simulations with observed emission from animal, barn, lagoon, and crop field unit operations. Overall the methane, ammonia, and nitrous oxide emissions, model simulated emissions from these unit operations were found in close agreement with observed values. Dairy-CropSyst was used to investigate the impact of current and emerging manure treatment options on gaseous emission and nutrient fate at two locations in Washington State. Model scenarios considered the impact of anaerobic digestion, coarse fiber removal, fine solids recovery, and ammoniacal nitrogen recovery when arranged in four sequential orders. These analyses also included the effect of weather, herd size, and animal-to-land ratio, each at two levels. The simulation scenario that had all four treatments not only reduced gaseous emissions and nutrient overloading of soils, but also recovered manure nutrients in value-added products.

GREENHOUSE GAS EMISSION AND NUTRIENT FATE ON DAIRY CONFINED ANIMAL FEEDING OPERATIONS

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