Claude Laguë

PHYSICAL AND RHEOLOGICAL PROPERTIES OF MANURE PRODUCTS

Selected physical and rheological properties deemed to influence the performances of handling and land application equipment were quantified for different types of manure at different levels of total solids concentration (TS) ranging from 10% to 50% on a wet mass basis. The selected properties included total solids concentration, bulk density, particle size distribution, friction characteristics, and shearing behavior and were measured for dairy cattle, sheep, poultry, and pig manure. The bulk density of all manure products was found to increase with TS and the values for poultry and pig manure were not significantly different at the tested TS levels. The measured density values were in close agreement with ASAE D384. The proposed modified geometric mean length of the particles was found to significantly increase as TS became smaller. The static friction coefficients of all manure types with the exception of pig manure on the different surface materials [plywood, plastic, steel (bare and painted )] did not exhibit large differences and a single linear equation was suggested to predict the static friction coefficient as a function of TS. Animal manures were described as pseudoplastic fluids and the consistency coefficients were found to increase with TS for all manure types. The apparent viscosity of the tested manure products was well correlated to TS. The implications of the property results obtained in this study as well as future research are discussed.

Diurnal Odor, Ammonia, Hydrogen Sulfide, and Carbon Dioxide Emission Profiles of Confined Swine Grower/Finisher Rooms

Abstract The objective of this study was to obtain diurnal variation profiles of odor and gas (ammonia [NH3], hydrogen sulfide [H2S], carbon dioxide [CO2]) concentrations and emission rate (OGCER) from confined swine grower/finisher rooms under three typical weather conditions (warm, mild, and cold weather) in a year. Two grower/finisher rooms, one with a fully slatted floor and the other with partially slatted floors, were measured for 2 consecutive days under each weather condition. The results revealed that the diurnal OGCER in the room with a fully slatted floor was 9.2–39.4% higher than that with a partially slatted floor; however, no significant differences in the diurnal OGCER were found between these two rooms, except for the NH3 concentrations in August, the NH3 and H2S concentrations and emissions in October, and odor concentrations and emissions in February (p > 0.05). The OGCER variations presented different diurnal patterns as affected by time of day, season, type of floor, ventilation rate, animal growth cycles, in-house manure storage, and weather conditions. Significant diurnal fluctuations in the OGCER (except for the odor concentrations and H2S emissions) were observed in August (p < 0.05); all of the gas emissions in October and the CO2 concentrations and emissions in February also showed significant diurnal variations (p < 0.05). These significant diurnal variations indicated that the OGCER during different periods of a day should be monitored when quantifying OGCER concentrations and emissions; for example, source emission data used in air dispersion modeling to decrease the great incertitude of setback determination using randomly measured data.

SOIL COMPACTION BY MANURE SPREADERS EQUIPPED WITH STANDARD AND OVERSIZED TIRES AND MULTIPLE AXLES

A study was conducted on a heavy clay soil to evaluate soil compaction induced by different traffic treatments associated with liquid manure spreader systems. Five spreader weights (from 96 to 218 kN), two running gears (tandem and tridem, i.e., three axles) and two types of tire (conventional low section tire and oversized tire) were combined to obtain six traffic treatments, representative of liquid manure spreading operations in Quebec. Soil dry bulk density ( nb) and cone index (CI) were measured to evaluate compaction. Tire rut depths and the lateral influence zone were also investigated in the study. For a single pass of a spreader, soil compaction was confined to the tilled layer (about 0-250 mm depth) regardless of traffic treatments, and this did not affect emergence rates and yields of soybean under the particular soil and climate conditions that prevailed at the time of the study. Neither tandem nor tridem running gears were found to adequately contain soil compaction within the tilled layer for total spreader weights exceeding 154 kN. The acceptable limitation for a tandem spreader with conventional 21.5L-16.1 tires would be a total load of about 96 kN, resulting in average ground pressures of 150 kPa or less. If medium capacity spreaders are required, oversized tires are recommended for manure spreading on prairies or post-seeding applications on small grain crops. Finally, the recourse to multiple-axle running gears for larger spreaders to maintain or reduce unit load per axle or ground pressure does not result in less soil compaction than lower capacity tandem spreaders with comparable axle loads and ground pressure.

Finite element modeling of soil compaction by liquid manure spreaders.

A three-dimensional (3-D) finite element model was developed to predict the soil compaction caused by heavy liquid manure spreaders. The model includes both material and geometric nonlinearities. The updated Lagrangian method was applied to solve the geometric nonlinearity caused by large displacements. The finite element analysis was conducted with two types of tires, two different loads, and various inflation pressures. The finite element model was verified with the field test data. The results showed that the finite element model is adequate for predicting soil compaction. In agreement with observed data, the finite element results indicated that reused airplane tires with high inflation pressure resulted in the worst soil compaction, while an agricultural high floatation tire with a smaller load and lower inflation pressure caused the least soil compaction. The finite element results also demonstrated that soil compaction can be reduced by using lower tire inflation pressure.

Modeling Mechanical Behavior of Agricultural Soils

The stress-strain behaviors of a Mawcook gravel-sandy loam and a Ste-Rosalie clay were studied under triaxial compression and hydrostatic compression loading paths performed on undisturbed cylindrical samples. The experimental data were compared to two nonlinear elastic models, the hyperbolic model and Bailey’s model, as well as to two elasto-plastic models, a modified Cam clay model, and the simple cap model. The hyperbolic model accurately predicted stress and volumetric strain for the two testing procedures, including the unload-reload cycles. Bailey’s model accurately predicted volumetric strain at a given stress. The two elasto-plastic models were accurate in predicting volumetric strain for the hydrostatic tests and reasonably accurate in predicting stress in the triaxial tests. The main source of error in predicting volumetric strain under triaxial compression was attributed to the variability in soil physical properties among the samples. The Cam clay model used only five parameters and could account for the effects of pre-consolidation, elastic and plastic deformation. The experimental results also indicated that soils with high clay content experienced more volume change at given stress state than the coarse sandy soils, and that soil mechanical behavior within and below the plow layer differed significantly.

Livestock Odor Dispersion Modeling: A Review

This review article on the topic of livestock odor dispersion modeling focuses on odor sources, odor emission rates, odor characteristics and measurements, odor dispersion modeling methods, and methods and results of adapting industrial air dispersion models for livestock odor dispersion simulations. The Gaussian plume models, puff models, fluctuating plume models, and other models that have been applied in livestock odor dispersion modeling are explicitly reviewed. Research work on validation or evaluation of industrial air dispersion models using various field odor plume measurement results, scaling factor or peak-to-mean ratio, and various relationships between odor concentration and odor intensity generated by different studies is also discussed. Although many Gaussian models have been applied in livestock odor dispersion and have achieved relatively satisfactory results, there are many differences between traditional industrial air pollutants and livestock odor, including emission sources, travel distances, and most importantly, measurement methods and the inherent instantaneous characteristic of livestock odor that can challenge the use of Gaussian models. The research on applying advanced air dispersion models such as fluctuating plume models, Lagrangian stochastic models, and computational fluid dynamics (CFD) models in odor dispersion modeling is very limited. As a result, it is found necessary to develop an improved model that can accurately predict livestock odor concentration downwind of the sources. More specifically, a fluctuating plume model that has the ability to consider short time fluctuations of odor concentration is suggested for livestock odor dispersion within the short distances that are typically of interest in odor dispersion modeling.

Finite Element Prediction of Soil Compaction Induced by Various Running Gears

A three-dimensional finite element model was used to predict soil compaction induced by different running gears used on heavy liquid manure spreaders on two different soils. The finite element analyses were conducted for three types of tires: conventional implement I-1 high flotation bias tires, radial tires, and low pressure R-3 tires; and three types of running gears: two-, three- and four-axle. The soil compaction under removable rubber tracks was also studied under the assumption of uniform stress distribution. The results showed that substituting radial tires or low pressure tires for high flotation bias tires reduced soil compaction levels and that increasing the number of axles of the running gears lowered soil compaction significantly without increasing the width of the compacted zone. The results also implied that track-based running gears would possibly reduce traffic induced soil compaction. The simulation confirmed that axle load and the number of wheel passes were two major factors influencing subsoil compaction. The study of compaction on two soils indicated that, with similar running gears, compaction in clay soils was far more severe than that in coarsely textured soils.

PERFORMANCES OF CONVEYING SYSTEMS FOR MANURE SPREADERS AND EFFECTS OF HOPPER GEOMETRY ON OUTPUT FLOW

The objectives of this work were to evaluate the performances of different conveying systems for manure spreaders and to study the effect of the hopper geometry on material flow. Experiments were carried out at the University of Saskatchewan (Canada) and at Cemagref (France). A prototype land applicator was evaluated with both a scraper conveyor and a system of four augers. The specific energy required to unload the machine with the four-auger system was found to be higher than with the scraper conveyor, with average values for all experimental runs of 184 and 73 J/kg, respectively. A three-factor factorial design was used to study the effect of the vertical position of a flow-control gate, velocity of the conveying system, and inclination angle of the sidewalls for both types of conveying systems. The specific energy for both conveying systems was significantly affected by the position of the gate. The characteristic flow rate, as defined in European Standard EN 13080, was influenced by all three factors in the case of the scraper conveyor. The position of the gate, the velocity of the conveyor, and the interaction between these two factors were found to be significantly affecting the characteristic flow rate of the four-auger system. The output flow of three commercial manure spreaders having similar functional units but different hopper geometries was studied. The stretch within the tolerance zone was observed to increase when the length and width of the hopper were increased. The longitudinal coefficient of variation was observed to decrease when the length of the hopper was increased. The same effect was observed when increasing the width of the hopper and when reducing its depth. The physical properties of the products spread were deemed to have an influence on the response of the evaluation criteria to changes in hopper geometry. Cohesive products were observed to improve the discharge flow in terms of the stretch within the tolerance zone, the longitudinal coefficient of variation, and the actual to theoretical unloading time ratio.

Effectiveness of a Manure Scraper System for Reducing Concentrations of Hydrogen Sulfide and Ammonia in a Swine Grower-Finisher Room

The effectiveness of a manure scraper system for reducing the risk of barn worker and animal exposure to hydrogen sulfide (H2S) was evaluated by comparing gas levels in two swine production rooms, one with a manure scraper system installed (scraper) and the other with a conventional manure pit-plug system (control). Measurements were done over four production cycles; during each 12-week cycle, gas concentrations were measured 4 to 5 times during weeks that conventional manure removal activities were performed in the control room, while the scraper system was operated daily in the scraper room. Daily removal of manure from the scraper room resulted in measured maximum H2S concentrations that were significantly lower (by 90%) compared to the control room. The type of manure removal system had no significant effect on ammonia (NH3) concentration and emission; during each trial, NH3 emission increased in both rooms over the 4 to 5 monitored weeks. The scraper system was also operated in two different modes. These tests revealed that NH3 production was reduced when all the manure was removed from the room compared to leaving the liquid portion on the pit floor surface, although the differences were not significant (p > 0.10). The estimated cost of including the scraper system in the construction and operation of a new barn is CDN

Development of a Livestock Odor Dispersion Model: Part II. Evaluation and Validation

1.89 per pig sold, which is 35% less (on a per pig basis) than the cost of retrofitting an existing facility. The manure removal system tested was effective in reducing exposure of workers and animals to H2S, without significant adverse impact on NH3 production. However, given the highly variable nature of H2S production and dispersion within a room, care should always be taken when handling manure inside swine barns.