313 Efficacy of Vermifiltration to Treat Liquid Cattle Manure to Mitigate Carbon and Nitrogen Emissions

Abstract The objective was to determine the efficacy of a vermifiltration system that treats liquid cattle manure to alter methane (CH4), nitrous oxide (N2O), ammonia (NH3) emissions, and nutrient composition (potassium-K; phosphorus-P; nitrogen-N). Liquid manure was sampled as it entered the worm-bed (influent) and as it exited from the worm-bed (effluent) to measure changes in nutrient composition. Worm-bed surface fluxes of CH4 and N2O were measured in real-time for three distinct environmental temperatures (0 ˚C, 10 ˚C, and 20 ˚C) to examine seasonal variation at several locations in the 3.64 ha worm-bed using isolation chambers and cavity ring-down spectrometry. NH3 flux was measured from the chambers using a ChemComb 3500 Speciation Collection Cartridge and coated honeycomb denuders. NH3 samples were eluted within 4 h of collection and stored at -20 ˚C until colorimetric analysis. Duplicate NH3 measurements were made for each chamber location at each temperature. Examination of the influx and efflux data indicates reductions of 25% in K, 96% in P, 99% in total suspended solids, 92% in volatile solids, and 92% in total Kjeldahl N. Chamber CH4 concentrations at 0 ˚C (0.51 to 1.18 ppm) tended to be less at 10 ˚C (2.17 to 2.67 ppm) and 20 ˚C (1.6 to 2.45 ppm) but were not different across temperatures (P < .077) and reflected ambient concentrations (2.44 ppm). N2O concentrations at 0 ˚C (157.00 to 224.00 ppb) and 10 ˚C (86.3 to 176.5 ppb) were not different than ambient (358.5 ppb), but at 20 ˚C (400.0 to 655.0 ppb) concentrations tended to be greater (P < 0.07). NH3 concentrations at 0 ˚C (0.06 to 0.33 ppm) and 20 ˚C (1.35 and 2.21 ppm) were not different but at 10 ˚C (11.8 to 28.7 ppm) were greater (P < 0.05). Fluxes were calculated for each sampling period. During 0 ˚C flux densities were 1.61 ± 0.17 mg· m-2· day-1 for N2O, 2.5 0.57mg m-2· day-1 for CH4, and 0.007± 0.00 mg m-2· day-1 for NH3. At 20°C flux densities were 1.98± 0.63 mg· m-2day-1 for N2O, 2.88± 0.755 mg m-2· day-1 for CH4, and 25.4 ± 0.0 mg· m-2· day-1 for NH3.Flux calculations and extrapolation of emission rates to the entire system indicates that vermifiltration is an effective strategy to alter nutrient concentrations and reduce CH4 emissions but not emissions of N2O and NH3.