An Evaluation of the Physicochemical and Biological Characteristics of Foaming Swine Manure

Abstract

Foam accumulation in deep-pit manure storages is an increasing concern for swine producers because of the logistical and safety-related problems it creates. To investigate this phenomenon, samples of swine manure were collected over a 13-month period from 58 swine production facilities in Iowa with varying levels of foam accumulation. Samples were tested for a number of physical, chemical, and biological parameters including pH, total and volatile solids, volatile fatty acid concentration, long-chain free fatty acid concentration, biochemical methane potential, methane production rate, surface tension, foaming capacity, and foam stability. Statistical analysis indicated that manure collected from facilities with foam accumulation produced methane at significantly (p < 0.05) faster rates than non-foaming manures (0.148 ±0.004 and 0.049 ±0.003 L CH 4 L-1 slurry d-1 , respectively) and consequently had significantly (p < 0.05) greater fluxes of biogas moving through the manure. The biochemical methane production assay suggested that manure from foaming pits had less potential to generate methane (123 ±9 mL CH 4 g-1 VS) than manure from non-foaming pits (150 ±9 mL CH 4 g-1 VS), presumably because more of the methane potential had previously been consumed, as indicated by the higher methane production rates. Short-chain fatty acid concentrations were significantly lower in foaming manures (4200 ±570 mg kg-1) than non-foaming manures (9470 ±730 mg kg-1). The methane production rate, biochemical methane potential, and short-chain fatty acid assays suggest enhanced anaerobic digestion efficiency from foaming barns as compared to non-foaming barns. Other assays, such as surface tension and foaming capacity, indicated an accumulation of a surfactant at the manure-air interface of the foam, which may be capturing biogas bubbles generated within the manure. Most importantly, the foam layers exhibited a greatly enhanced ability to stabilize bubbles, which appeared to be correlated to the higher solids concentrations that stabilize the bubbles.

Impact of Dietary Carbohydrate and Protein Source and Content on Swine Manure Foaming Properties

“…In general, the BMP magnitudes reported in our study were substantially higher than the magnitudes reported for samples collected from deep-pit production swine barns. Van Weelden et al (2015) reported an average value of 121 ±86 mL CH 4 g -1 VS for both foaming and non-foaming samples, with foaming samples showing a slightly lower average value; in our study, BMP values of 155 to 395 mL CH 4 g -1 VS were found. The current BMP results were comparable to other studies, which showed that fresh swine manure ranged between 244 to 480 mL CH 4 g -1 VS (Burton and Turner, 2003;Møller et al, 2004;King et al, 2011) depending on ration.…”

“…The foaming capacity and stability were tested according to the method described by Van Weelden et al (2015). In brief, air was passed through a 300 mL manure sample at 0.2 L min -1 until a constant foam height was recorded.…”

Microbial assemblages and methanogenesis pathways impact methane production and foaming in manure deep-pit storages

“…Data were collected to describe each farm's feed ingredients. Manure sampling procedures and characterization (e.g., total solids, methane production rate) have previously been described [7]. Additional manure characterization (i.e., pH, moisture, organic N) was performed by Midwest Laboratories (Omaha, NE).…”

“…Pair-ended bacterial 16S rRNA gene sequences were assembled using the Ribosomal Database Project (RDP) Paired-end Reads Assembler 7 with minimal overlap of 80 bases (-o 80) and minimal assembled length 350 bases (-l 350). Assembled sequences with an expected maximum error-adjusted Q score less than 25 over the entire sequence were eliminated.…”