pH Specific Calcium Carbonate Precipitation in Gypsum-amended Litters
Abstract
Flue-gas desulfurization gypsum (FGDG) (CaSO4·2H2O) has been proposed as a litter amendment to control ammonia (NH3) volatilization due to pH buffering by calcium carbonate (CaCO3) precipitation. There is limited information on the formation of CaCO3 in broiler litter and the pH at which CaCO3 forms. Furthermore, newly developed acidified-gypsum amendments have been proposed, but there is no research indicating CaCO3 forms in acidified litter. The objective of our study was to establish a pH range in which CaCO3 forms in broiler litter. We conducted a laboratory incubation in which litter pH, CO2 emission, and CaCO3 precipitation were measured. Treatments in this study included: broiler litter (control) (BL), broiler littler + 20% FGDG (BL+FGDG), and broiler litter + 20% reagent grade gypsum (BL+GYP). In order to measure CaCO3 precipitation at different pH levels, our litter was initially treated with 8% alum (acidifying chemical). Urea and additional water were added to the litter to ensure urea hydrolysis was not limited during the incubation. We hypothesized that CaCO3 precipitation in gypsum-amended litters would decrease CO2 emissions, and CaCO3 would not form at a pH < 8. Our results indicate that the addition of FGDG and reagent-grade gypsum have a minimal effect on litter pH (p = 0.022). Calcium carbonate did not form in these gypsum-amended litters at a pH < 7.9. Our results also indicate the dissolution of different types of gypsum in broiler litter reduces CO2 emission due to reduction in microbial activity.
pH Specific Calcium Carbonate Precipitation in Gypsum-amended Litters
Flue-gas desulfurization gypsum (FGDG) (CaSO4·2H2O) has been proposed as a litter amendment to control ammonia (NH3) volatilization due to pH buffering by calcium carbonate (CaCO3) precipitation. There is limited information on the formation of CaCO3 in broiler litter and the pH at which CaCO3 forms. Furthermore, newly developed acidified-gypsum amendments have been proposed, but there is no research indicating CaCO3 forms in acidified litter. The objective of our study was to establish a pH range in which CaCO3 forms in broiler litter. We conducted a laboratory incubation in which litter pH, CO2 emission, and CaCO3 precipitation were measured. Treatments in this study included: broiler litter (control) (BL), broiler littler + 20% FGDG (BL+FGDG), and broiler litter + 20% reagent grade gypsum (BL+GYP). In order to measure CaCO3 precipitation at different pH levels, our litter was initially treated with 8% alum (acidifying chemical). Urea and additional water were added to the litter to ensure urea hydrolysis was not limited during the incubation. We hypothesized that CaCO3 precipitation in gypsum-amended litters would decrease CO2 emissions, and CaCO3 would not form at a pH < 8. Our results indicate that the addition of FGDG and reagent-grade gypsum have a minimal effect on litter pH (p = 0.022). Calcium carbonate did not form in these gypsum-amended litters at a pH < 7.9. Our results also indicate the dissolution of different types of gypsum in broiler litter reduces CO2 emission due to reduction in microbial activity.