Terrance A. Fonstad

Molecular characterization of anaerobic digester microbial communities identifies microorganisms that correlate to reactor performance.

A time-course analysis was conducted of thermophilic anaerobic digestion of dairy manure and wheat distillery thin stillage. Sequencing of chaperonin targets provided a phylogenetic survey of both bacteria and archaea in the digestate, along with an appraisal of the diversity of the reactor microbiome. A total of 1129 bacterial operational taxonomic units (OTU) were detected in the reactors, with OTU related to Clostridium becoming numerically dominant by day 7, and Acetivibrio-related OTU by day 35. Archaeal communities were less diverse, with 19 OTU detected representing both acetoclastic and hydrogenotrophic methanogens. Regardless of input material, the same organisms came to dominate the reactors, reflecting strong selective pressures present in the digesters. Principal coordinate analysis of the microbial communities showed that the bacterial communities clustered based on factors other than input material. Bacterial and archaeal OTU were identified with significant correlations to performance parameters, suggesting important roles in the methane production pathway.

GREENHOUSE GAS EMISSIONS FROM LIQUID SWINE MANURE STORAGE FACILITIES IN SASKATCHEWAN

Greenhouse gas (GHG) emissions from manure storage facilities at four different commercial farrow-to-finish swine operations under liquid manure management located in Saskatchewan, Canada, were experimentally determined during the spring-to-fall period between 2001 and 2003. These operations featured three types of manure storage facilities: uncovered concrete tank, uncovered earthen manure basin (EMB), and covered (blown chopped straw) EMB. GHG emission rates were expressed in terms of unit mass of animal producing the stored manure. On average, methane and carbon dioxide emission rates were respectively 3.75 g CO2 equivalent day-1 kg-1 and 1.73 g CO2 equivalent day-1 kg-1, while nitrous oxide emission rates were negligible. The total average GHG emission rate measured in this study was 5.48 g CO2 equivalent day-1 kg-1. On average, GHG emissions from the uncovered EMB were the largest, while those from the covered EMB were the lowest. Emissions were maximum during the summer and at their lowest during the spring, and night emissions were larger than those that occurred during the daytime. Estimations based on the results of this study indicate that the addition of a blown chopped straw cover on an EMB can yield reductions in CO2 and CH4 emissions of 56 and 786 tonnes of CO2 equivalent per year, respectively, for each 1,000-sow increment.

Microbial community composition is consistent across anaerobic digesters processing wheat-based fuel ethanol waste streams.

Biochemical methane potential (BMP) assays were conducted on byproducts from dry-grind wheat-based ethanol plants amended with feedlot manure at two input ratios. Whole stillage (WST), thin stillage (TST) and wet cake (WCK) were tested alone and with 1:1 and 2:1 ratios (VS basis) of byproduct:feedlot manure in bench-scale batch reactors. The addition of manure increased both the rate and consistency of methane production in triplicate reactors. In addition, digesters co-digesting thin stillage and cattle manure at 1:1 and 2:1 stillage:manure produced 125% and 119% expected methane based on the biomethane potential of each substrate digested individually. Bacterial community analysis using universal target amplification and pyrosequencing indicated there was a numerically dominant core of 42 bacteria that was universally present in the reactors regardless of input material. A smaller-scale analysis of the archaeal community showed that both hydrogenotrophic and acetoclastic methanogens were present in significant quantities.

SOLUTE AND MOISTURE FLUX BENEATH CATTLE FEEDLOT PENS

Seepage of manure beneath cattle feedlot pens can be responsible for groundwater contamination. In semiarid climates, such as the Canadian Prairies, there can be deep unsaturated zones, thus slowing solute travel to the water table. The purpose of this study was to determine the depth and rate of manure seepage and soil moisture flux using profile analysis techniques. Manure seepage was represented by the solutes K + , Cl – , NH4–N, and NO3–N. Solute concentrations from soil cores beneath three 30–year–old feedlots near Saskatoon, Saskatchewan, were examined. Although nitrate and ammonia ions were measured, the objectives were met using chloride and potassium as they are not affected by biological transformation and can be used to approximate nitrate and ammonia ions. The concentrations of K + , Cl – , and NH4 + –N were at least two orders of magnitude greater in the top soil layer than their background solute levels found at depth beneath the feedlot. In soil cores, Cl – decreased to background levels by 2.2 to 4.9 m depth and was at 50% relative concentration by 0.2 to 0.6 m depth, whereas K + background and 50% concentrations occurred at depths between 1/3 to 2/3 that of chloride. Moisture flux beneath these pens is between 2 and 6 mm/yr, which although low, is not atypical for the prairies. Movement by diffusion accounts for 1 to 2 mm per year. This study indicates that although most of the manure solutes are moving as bulk flow (matrix) and movement is thus very slow, there is sufficient bypass flow to contaminate shallow piezometers located up to 20 m outside of the pens.

Livestock Mortalities Burial Leachate Chemistry after Two Years of Decomposition

A study was performed to determine the chemical composition of animal mortality leachate arising in a burial setting. Three species of livestock were used: bovine, swine and poultry. Leachate collected from lined burial pits over two years of decomposition was analyzed for major and minor ions. Livestock mortality leachate contains on average, concentrations of 12,600 mg/L of ammonium-N, 46,000 mg/L alkalinity (as bicarbonate), 2,600 mg/L chloride, 3,600 mg/L sulphate, 2,300 mg/L potassium, 1,800 mg/L sodium, 1,500 mg/L phosphorus along with relative lesser amounts of iron, calcium and magnesium. Maximum concentrations of select samples had concentrations of ammonium-N and bicarbonate up to 50% higher than these average values. The pH of the leachate was near neutral. In comparison to earthen manure storages and landfills, the strength of the leachate was 2-4 times higher.

Influence of Mass Burial of Animal Carcasses on the Types and Quantities of Microorganisms within a Burial Site

Microbial communities were characterized through a depth of 10 m in and near an eight-year-old burial site that was implemented as a control measure for cases of chronic wasting disease among wild elk. Quantitative PCR based on the 16S rRNA-encoding gene showed that the burial trench had significantly (2 to 5 orders of magnitude) more bacterial 16S rRNA-encoding genes g-1 soil within and up to 2 m below the burial site compared to a nonburial control core sample at the same depths. Topsoil and depths below the burial site (>6 m) showed similar quantities of 16S rRNA genes for both cores. Furthermore, when microbial communities were examined by cpn60 universal target amplification and pyrosequencing, 5825 operational taxonomic units (OTU) were found at a variety of abundances in all of the 13 core samples that were analyzed. Taxonomic analysis indicated that the overall community composition changed considerably with increasing depth, and that the burial core community was distinct from that of the control core at all depths. Organisms associated with phosphate accumulation, nitrogen fixation, and ammonium oxidation were found in highest abundance near the surface of the burial core (up to 2.5 m), while organisms associated with ammonification were found at the burial depth, consistent with an increase in ammonium concentration in pore water. Sequences from organisms associated with dissimilatory metal reduction were concentrated just below the burial depth (4.5 to 5.5 m). Anaerobic microorganisms dominated the microbial community at the burial site (3.75 m). The approaches described in this study provided distinct sequences that can be used to develop molecular assays for organism tracking and overall fingerprinting of microbes associated with burial sites. These data can be helpful in site evaluation and may help in the selection of future burial sites.

Livestock Mortalities Burial Leachate Chemistry: The First Nine Months

A study was performed to determine the leachate chemistry from five livestock mortalities burial pits. Three species were used in this study, poultry, swine and bovine. Leachate chemistry was measured five times over a period of nine months. It was found that the chemical composition and concentrations of the leachate varies slightly by species but in general follows the same trend over the time period. Ammonium and bicarbonate are the major anions and cations respectively. Bovine leachate showed the highest values for ammonium and bicarbonate at 992 meq/L (3 months) and 875 meq/L (9 months) respectively. .