This thesis examines how the non-Newtonian characteristics of liquid hog manure affect the flow conditions within a steady-flow anaerobic digester. There are three main parts to this thesis. In the first part of this thesis, the physical properties of liquid hog manure and their variation with temperature and solids concentration are experimentally determined. Naturally¬¬-settled manure sampled from an outdoor storage lagoon is studied, and density, viscosity, and particle size distribution are measured. Hog manure with total solids concentrations of less than 3.6% exhibits Newtonian behaviour; manure between 3.6% and 6.5% total solids is pseudoplastic, and fits the power law; manure with more than 6.5% total solids exhibits non-Newtonian and time-dependent characteristics. The second part of this thesis investigates the flow of Newtonian and non-Newtonian fluids—represented by tap water and xanthan gum solution, respectively—within four lab-scale reactor geometries, using residence time distribution (RTD) experiments. The effect of reactor geometry, flow rate, and fluid viscosity are evaluated. In the third part of this thesis, flow conditions within lab-scale and pilot-scale anaerobic digester reactors are simulated using three-dimensional modeling techniques. The RTDs of lab-scale reactors as predicted by the 3D numerical models compare well to the experimental results. The 3D models are also validated using data from particle image velocimetry (PIV) experiments. Finally, the viscous properties of liquid hog manure at 3% and 8% total solids are incorporated into the models, and the results are evaluated.

Microbial contamination of drinking water poses an important health risk which causes severe illnesses and epidemics. In order to improve surface and drinking water quality, the understanding of fecal pathogen contamination processes including their prevention and control needs to be enhanced. The watershed model soil water assessment tool (SWAT) is commonly used to simulate the complex hydrological, meteorological, erosion, land management and pollution processes within river basins. In recent years, it has been increasingly applied to simulate microbial contamination transport at the watershed scale. SWAT is used in this study to simulate Escherichia coli (E.coli) and fecal coliform densities for the agriculturally dominated Payne River Basin in Ontario, Canada. Unprecedented extensive monitoring data that consist of 30 years of daily hydrological data and 5 years of bi-weekly nutrient data have been used to calibrate and validate the presented model here. The calibration and validation of the streamflow and nutrients indicate that the model represent these processes well. The model performs well for periods of lower E. coli and fecal coliform loadings. On the other hand, frequency and magnitude of higher microbial loads are not always accurately represented by the model.

In Manitoba, potato fields have been found to be infested with Verticillium dahliae, which can produce Vertcillium wilt disease severity of up to 90% and reduce yield. Potato producers have then an increased interest on use of green manures and organic amendments to control Verticillium wilt. The objectives of this research were to evaluate selected green manure and organic amendments for their ability to reduce propagule density of V. dahliae in soil, incidence and severity of Verticillium wilt, and to enhance potato yield in Manitoba. In addition, a second study was conducted for the purpose of studying the potential of mustard green manure and seed meal to inhibit the germination of microsclerotia. Findings suggest that composted-cattle-manure and oriental mustard seed-meal amendments have promise as an alternative strategy for the control of V. dahliae. However, only composted beef cattle manure reduced disease, increased potato yield and improved nutrient availability (P) in soil

Two laboratory incubation studies and a growth room bioassay of forage barley were conducted to investigate nitrogen (N) and phosphorus (P) mineralization, and nitrous oxide emission from two contrasting agricultural soils amended with anaerobically digested cattle manure (ADM). The ADM is a nutrient-rich co-product from manure-based biogas plants which is applied to cropland at rates used for raw manure since scientific information on nutrient release from ADM is lacking. Application of the separated solids fraction of ADM (SS) reduced nitrous oxide emission but resulted in lower N mineralization compared to raw manure in both soils. Raw manure- and SS- treatments had similar biomass yields and P supply capacities while the application of pelletized SS (PSS) caused net N immobilization, lower P release than manure and SS, and depressed barley yields relative to non-amended (control) soils.

Darbo tikslas – nustatyti kiaulių ir galvijų mėšlui būdingas maksimalaus metano susidarymo (Bo), ir teorinio metano susidarymo (Bu) reikšmes, bei ištirti klimato kaitą skatinančių, ir aplinką teršiančių dujų emisijų mažinimo iš mėšlo priemonių taikymo efektyvumą. Darbo uždaviniai: 1) nustatyti maksimalų metano dujų kiekį galintį išsiskirti iš kiaulių ir galvijų mėšlo. 2) ištirti priedų įtaką NH3, CO2, CH4, H2S, NO ir CO dujų emisijoms iš skysto ir pusiau skysto galvijų ir kiaulių mėšlo. 3) nustatyti įvairių plaukiojančių dangų poveikį NH3, CO2, CH4, H2S, NO ir CO dujų emisijoms skysto ir pusiau skysto mėšlo laikymo metu. 4) ištirti priedų ir plaukiojančių dangų kompleksinio naudojimo įtaką NH3, CO2, CH4, H2S, NO ir CO dujų emisijoms iš skysto ir pusiau skysto galvijų ir kiaulių mėšlo. Tyrimai vykdyti dviejų kiaulių tvartų aplinkoje ir laboratorinėmis sąlygomis. Bandymams laboratorinėmis sąlygomis atlikti buvo panaudoti mėšlo mėginiai surinkti iš 28 gyvulininkystės ūkių. Tyrimų metu nustatytas maksimalus metano dujų kiekis galintis išsiskirti iš kiaulių ir galvijų mėšlo. Taip pat ištirtas mikrobiologinio preparato ir sieros rūgšties priedų, plaukiojančių dangų, t. y., keramzito, natūralių durpių, valgomojo saulėgrąžų aliejaus, medžio pjuvenų, šiaudų, polietileno plėvelės, bei priedų kompleksinio naudojimo su polietileno plėvele poveikis NH3, CO2, CH4, H2S, NO ir CO dujų emisijoms iš mėšlo. Atliki tyrimai, kuriuose įvertintas priedų bei įvairių plaukiojančių dangų poveikis... [toliau žr. visą tekstą] / The aim of the present study – to study the ultimate (Bo) and theoretical (Bu) methane yield from pig and cattle manure, and to investigate the effectiveness of implements on the emission reduction of polluting and greenhouse gases from manure. Tasks of the present study: 1. To measure the ultimate methane yield from pig and cattle manure. 2. To investigate the effect of the additives on the reduction of emission of the NH3, CO2, CH4, H2S, NO and CO gases from liquid and semi-liquid manure of cattle and pigs. 3. To determine the effect of different floating covers on the reduction of emission of the NH3, CO2, CH4, H2S, NO and CO gases from liquid and semi-liquid manure during the storage. 4. To investigate the effect of the complex of additives and floating covers on the reduction of emission of the NH3, CO2, CH4, H2S, NO and CO gases from liquid and semi-liquid manure of cattle and pigs. The investigations were performed in two piggeries and a laboratory. To carry out the experiments in the laboratory, the manure was collected from 28 farms. During the investigation period, the ultimate methane yield from pig and cattle manure was determined. Also, the effect of the microbial-based and sulphuric acid additives, floating covers, i. e., leca (light expanded clay aggregate), natural peat, sunflower oil, sawdust, straw and plastic film, and furthermore, the complex of additives and a plastic film cover on the emission of NH3, CO2, CH4, H2S, NO and CO gases from manure were... [to full text]

A review of the literature indicates that the understanding of the mixing phenomena in anaerobic digesters is limited and the ability to measure digester mixing characteristics is lacking. Moreover, rheological characteristics of the sludge are largely ignored. The need for a more thorough understanding of fundamental mixing relationships and the ability to measure these relationships in the anaerobic digester is recognized. To this end, investigations using experimental and numerical methods to visualize flow patterns and quantify mixing that impact biogas yields is reported. Results from this research identifies optimum mixing regimes for digesters depending on their sludge rheology, operational regimes, digester dimensions and mixing systems, and also produces an industrial guide to improve digester design. The results show that in order to accurately predict the optimum mixing regime for a particular anaerobic digester, it is necessary to determine to what extent biogas output is dependent upon, and can be influenced by flow patterns in an anaerobic digester. These flows are in turn determined by physical characteristics of the digester, the feed regime, the mixing system and the rheological properties of the sludge. Mixing regimes are tailored to produce flow patterns that could potentially increase biogas production and/or reduce mixing energy input of the digester. An all-inclusive anaerobic digester model is developed and validated using advanced experimental techniques that can be used to optimize the digestion process in terms of physical and biological parameters. In either case, the model provides an ongoing management of anaerobic digester process to improve overall energy yield from the digester and reduce its environmental impact.

Overall soil productivity is declining in the U.S. due to loss of soil organic matter (SOM). Decreased SOM lowers soil water storage, reduces water infiltration, slows aggregate formation, and depletes soil of nutrients. In many systems, crop nutrients are replaced by expensive synthetic fertilizers that can lead to environmental concerns. This practice is not economically or environmentally sustainable in the long term. To secure future soil use and crop production, sustainable management practices are needed to prevent further SOM depletion. Incorporating legumes into cropping systems is one alternative that can bolster soil organic C (SOC) (key indicator of SOM) and reduce N fertilizer applications through symbiotic legume N fixation. Three studies were conducted over multiple years at the Texas A&M AgriLife Research and Extension Center near Overton, TX. Annual cool- and warm-season legumes were evaluated as potential green manure crops and intercrops under grain sorghum [Sorghum bicolor (L.) Moench], high-biomass sorghum [Sorghum bicolor (L.) Moench], and annual forage cropping systems. These studies quantified legume soil moisture usage and C and N contributions to the soil and subsequent crop yields in East Texas. Primary project objectives were to maintain or maximize primary crop yields at reduced N fertilizer rates and to build SOC through the integration of legume green manures and intercrops. Green manuring cool-season legumes showed the most beneficial effect on SOC, soil total N, and crop yields; however, significant increases in yield were only detected after three years in rotation. Intercropping Iron-and-Clay cowpea (Vigna unguiculata L. [Walp]) decreased yield of both high-biomass sorghum and grain sorghum due to competitive vegetative growth. Iron-and-Clay did however improve biomass yields of high-biomass sorghum in two subsequent years when implemented as a green manure. Despite large N yields as high as 310 kg ha-1, impacts of legumes on annual forage crops was limited. Poor response was likely a result of previous field history in which a permanent warm-season grass pasture was cultivated for site preparation and mineralized SOC released substantial amounts of available N. Under low soil N conditions, legume green manures produce enough N to likely reduce N fertilizer requirements cost-effectively for subsequent crops in East Texas.

Promotion of agroforestry practices in sub-Sahara Africa may help sustain subsistent food and wood production by integrating trees and crops on farmlands to replenish soil fertility and improve crop yield. Using rotational woodlot and pigeonpea intercropping systems in semi-arid Tanzania as case studies, my research screened suitable tree species to increase fuelwood supply and examined mechanisms for reducing tree-crop competition. By adopting nutrient use efficiency (the ratio of biomass yield to nutrient uptake) as a criterion, I found that selecting tree species of low wood nutrient concentrations would minimize nutrient exports by 42 – 60 %, thus reducing soil nutrient depletion while concurrently sustaining local fuelwood supply harvested from rotational woodlots. Currently smallholder farmers cannot afford to replenish soil fertility because of high fertilizer costs. However, 5-year tree fallowing raised soil N and P levels for maize culture as high as those from recommended fertilizer applications. Post-fallow maize yield was also increased significantly over natural fallow practices. Apparently there is a trade-off between yields of maize and fuelwood under rotational woodlot culture providing farmers the choice to proportion tree and crop composition based on priority demands. An alternative practice of intercropping pigeonpea with maize may also rapidly replenish soil fertility as well as enhance maize yield when competitive interactions between trees and crops are controlled. Vector analysis revealed that such interactions suppressed biomass yields of maize and pigeonpea by 30 % and 60 %, respectively, due to limited soil nutrients and/or moisture. Optimizing yields of both crops would require prescribed fertilizer addition when intercropped, but dose rates can be lowered by half under the improved fallow system due to alleviating interspecific competition. My findings form the basis of a plea for greater use of rotational woodlot and pigeonpea intercropping systems in semi-arid areas. I conclude that smallholder farm management of rotational agroforestry systems can be significantly improved by refining tree selection criteria and mitigating nutrient competition between trees and crops to maintain food and fuelwood production.

Eutrophication resulting from phosphorus (P) accumulation in water systems has been a worldwide concern for three decades. Agricultural soils are known to be an important non-point source of P in waterways. The objectives of this research are to identify agricultural management practices that reduce the risk of P loss from soils, and to investigate the underlying mechanisms of P retention and loss from soils. In the short term (4 years), dissolved P loads were not affected by tillage and were similar in corn (in a continuous corn rotation) and soybean (in a soybean/corn rotation) production systems. Soils amended with composted cattle manure had a greater P load than chemically fertilized soils. On average, 30% of the total P leached was in organic P forms, indicating that organic P compounds could also be problematic to water systems. Although manure application improved soil aggregation and thus may increase P retention by avoiding soil erosion, P loss through subsurface flow by leaching may be substantial. A simple soil test, either Mehlich-3 P or P saturation ratio can predict the P leaching potential, but water ponding on the surface of agricultural land could significantly affect the accuracy of the prediction. / The P adsorption data was fit with the Langmuir 2-surface model, which predicted that up to 90% of the native adsorbed P was distributed on the high-energy surface. Native adsorbed P in manured soils was weakly retained, as the binding strength coefficient was 50 times less in manured than chemically fertilized soil. This findings was confirmed by measuring P desorption, which showed that P desorption rate was almost 3 times greater from manured soils than from chemically fertilized soils. Manuring alters soil particle surfaces by increasing negative charge. This is the direct reason for less P adsorption and greater P desorption by manured soils. / The Langmuir 2-surface model and the adapted non-ideal competitive adsorption (MICA) model were equally good at modeling P adsorption data. However, the NICA model is more robust and can predict phosphate adsorption with changing soil solution pH. The simultaneously modeling of P adsorption and hydroxyl adsorption with the NICA model makes it a promising tool for analyzing competitive adsorption among anions in soils.

Diss. (sammanfattning) Alnarp : Sveriges lantbruksuniv. / Härtill 5 uppsatser.