Impact of fiber source and feed particle size on swine manure properties related to spontaneous foam formation during anaerobic decomposition

Foam accumulation in deep-pit manure storage facilities is of concern for swine producers because of the logistical and safety-related problems it creates. A feeding trial was performed to evaluate the impact of feed grind size, fiber source, and manure inoculation on foaming characteristics. Animals were fed: (1) C–SBM (corn–soybean meal): (2) C–DDGS (corn–dried distiller grains with solubles); and (3) C–Soybean Hull (corn–soybean meal with soybean hulls) with each diet ground to either fine (374 μm) or coarse (631 μm) particle size. Two sets of 24 pigs were fed and their manure collected. Factors that decreased feed digestibility (larger grind size and increased fiber content) resulted in increased solids loading to the manure, greater foaming characteristics, more particles in the critical particle size range (2–25 μm), and a greater biological activity/potential

The Impact of Carbohydrate and Protein Level and Sources on Swine Manure Foaming Properties

This study explored the impact of swine diet on the composition, methane production potential, and foaming properties of manure. Samples of swine manure were collected from controlled feeding trials with diets varying in protein and carbohydrate levels and sources. Protein sources consisted of corn with amino acids, corn-soybean meal with amino acids, corn-soybean meal, corn-canola meal, corn-corn gluten meal, and corn-poultry meal. Carbohydrate sources consisted of corn-soybean meal, barley, beet pulp, distillers dried grains with solubles (DDGS), soy hulls, and wheat bran. Manure samples were tested for a number of physical and biochemical parameters, including total solids, volatile solids, viscosity, density, methane production rate, biochemical methane potential, foaming capacity, and foam stability. Statistical analyses were performed to evaluate whether different carbohydrate and/or protein ingredients affected these physico-chemical properties or the samples’ ability to produce methane gas. After conducting these trials, another feeding trial was performed to evaluate if the addition of Narasin into rations (corn-soybean and DDGS) could reduce the methane production rate or potential of the manure. These samples were also tested for the physical and biochemical parameters mentioned previously. Finally, an additional manure foaming study was conducted involving the addition of specific carbohydrates ground to different particle sizes and corn oil to observe the effects that the additives had on foaming capacity and stability

Three-Phase Foam Analysis and the Development of a Lab-Scale Foaming Capacity and Stability Test for Swine Manures

Foam accumulation on the manure slurry at deep pit swine facilities has been linked to flash fire incidents, making it a serious safety concern for pork producers. In order to investigate this phenomenon, samples of swine manure were collected from over 50 swine production facilities in Iowa with varying levels of foam accumulation over a seven month period. These samples were tested for a number of physical and chemical parameters including temperature, pH, total solids, volatile solids, volatile fatty acid concentration, biochemical methane potential, and methane production rate. After establishing these parameters, a foaming capacity and stability test was performed where samples were placed in clear PVC tubes with air diffusers at the bottom to simulate biogas production. The amount of foam produced at a set aeration rate was recorded as a measure of foaming capacity, and foam stability was assessed by measuring the height of foam remaining at certain time intervals after aeration had ceased. The results of this test indicated that samples collected from foaming barns showed a greater capacity to produce and stabilize foam. In addition, statistical analysis indicated that manures with foam produced methane at significantly greater rates than non-foaming manures (0.154 ± 0.010 and 0.052 ± 0.003 L CH4./L slurry*day respectively, average standard error), and consequently had significantly greater fluxes of methane moving through the manure volume. On the other hand, the biochemical methane production assay suggested that manure from foaming pits had less potential to generate methane (112 ± 9 mL CH4/g VS) than non-foaming pits (129 ± 9 mL CH4/g VS), and the VFA analysis showed significantly lower concentrations in foaming pits (4472, 3486, and 1439 μg/g for the surface level and descending depths of the pit, respectively) as compared to non-foaming pits (9385,8931, and 6938 μg/g for the same sample depths). When taken together, these assays suggest enhanced anaerobic digestion efficiency from foaming barns, as well as the possible accumulation of a surfactant at the manure-air interface of foaming deep pits. Overall, this work supports a three-phase system conceptualization of foam production in swine manure deep pits, and that the control of one or more of these phases will be required for mitigation

Microbial Community and Chemical Characteristics of Swine Manure during Maturation

Swine diet formulations have the potential to lower animal emissions, including odor and ammonia (NH3). The purpose of this study was to determine the impact of manure storage duration on manure chemical and microbial properties in swine feeding trials. Three groups of 12 pigs were fed a standard corn–soybean meal diet over a 13-wk period. Urine and feces were collected at each feeding and transferred to 12 manure storage tanks. Manure chemical characteristics and headspace gas concentrations were monitored for NH3, hydrogen sulfide (H2S), volatile fatty acids, phenols, and indoles. Microbial analysis of the stored manure included plate counts, community structure (denaturing gradient gel electrophoresis), and metabolic function (Biolog). All odorants in manure and headspace gas concentrations were significantly (p \u3c 0.01) correlated for length of storage using quadratic equations, peaking after Week 5 for all headspace gases and most manure chemical characteristics. Microbial community structure and metabolic utilization patterns showed continued change throughout the 13-wk trial. Denaturing gradient gel electrophoresis species diversity patterns declined significantly (p \u3c 0.01) with time as substrate utilization declined for sugars and certain amino acids, but functionality increased in the utilization of short chain fatty acids as levels of these compounds increased in manure. Studies to assess the effect of swine diet formulations on manure emissions for odor need to be conducted for a minimum of 5 wk. Efforts to determine the impact of diets on greenhouse gas emissions will require longer periods of study (\u3e13 wk)