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During the twentieth century, U.S. agriculture strived to achieve increased food production in order to satisfy both local and export demands. In many cases, this led to increased farm sizes and an operational separation of crop and livestock production. The trend of increasing centralization and industrialization of agriculture, specifically animal agriculture, has resulted in the concentration of waste products associated with animal production (manures and wash-down water) over relatively small geographic areas that are spatially segregated from crop production areas. Because the distance that manure can be economically hauled for land application has practical limits, the public is concerned that this spatial separation of crop and animal production areas could lead to over-application of manures near animal feeding facilities, and thus potentially increase the transport of nutrients to ground and surface waters. An aggregated analysis (statewide) of crop and animal production in Iowa suggests that about 30% to 40% of current nitrogen and phosphorus requirements for crop production could be supplied from manures and litters generated from livestock production, while about 50% of potassium requirements could be supplied. However, neither livestock nor crop production in Iowa is uniformly distributed across all counties. This unequal distribution suggests that a more disaggregated analysis of crop nutrient requirements and manure nutrient supply is necessary to estimate the risks of excess nutrient loss to the environment. Thus, we evaluated crop nutrient demand and manure and litter production at the county level to determine if excess manure generation is of concern and to locate areas where additional manures could be used. Results showed that several counties are becoming manure rich, but most locations maintain sufficient capacity to use manure nutrients effectively. [ABSTRACT FROM AUTHOR]

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 CH4 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 CH4 g-1 VS) than manure from non-foaming pits (150 ±9 mL CH4 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 nonfoaming 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. [ABSTRACT FROM AUTHOR]

Beef feedlot runoff is a potential environmental contaminant. As such, it should be managed properly to preserve water quality. Primary treatment of feedlot runoff often relies on sedimentation techniques; thus, accurate knowledge of feedlot runoff physical properties is required. This study characterized the physical and chemical properties of runoff effluent from earthen and concrete beef feedlots in Iowa with the objective\of providing the necessary information to improve solid settling basin design and performance. Results, although not statistically significant (p = 0.11), indicated that solids in runoff from concrete lots tended to settle more slowly than solids from earthen lots. Particle size distribution and particle density measurements indicated that the poorer settle ability of concrete lot runoff was primarily caused by lower particle densities: 1.47 ±0.17 g cm-3 (average ± SD) for concrete lots as compared to 1.89 ±0.11 g cm-3 for earthen lots. Runoff composition was analyzed before and after settling to relate nutrient reduction to solids removal. Results indicated an average of 41 g total Kjeldahl nitrogen per kg total solids and 16 g total phosphorus per kg total solids were removed during settling. [ABSTRACT FROM AUTHOR]

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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Methane emission is an important tool in the evaluation of manure management systems due to the potential impact it has on global climate change. Field procedures used for estimating methane emission rates require expensive equipment, are time consuming, and highly variable between farms. The purpose of this paper is to report a simple laboratory procedure for estimating methane emission from stored manure. The test developed was termed a methane production rate (MPR) assay as it provides a short-term biogas production measurement. The MPR assay incubation time is short (3d), requires no sample preparation in terms of inoculation or dilution of manure, is incubated at room temperature, and the manure is kept stationary. These conditions allow for high throughput of samples and were chosen to replicate the conditions within deep-pit manure storages. In brief, an unaltered aliquot of manure was incubated at room temperature for a three-days to assay the current rate of methane being generated by the manure. The results from this assay predict an average methane emission factor of 12.2 ± 8.1 kg CH4 head(-1) yr(-1) per year, or about 5.5 ± 3.7 kg CH4 per finished animal, both of which compare well to literature values of 5.5 ± 1.1 kg CH4 per finished pig for deep-pit systems (Liu et al., 2013). The average methane flux across all sites and months was estimated to be 22 ± 17 mg CH4 m(-2)-min(-1), which is within literature values for deep-pit systems ranging from 0.24 to 63 mg CH4 m(-2)-min(-1) (Park et al., 2006) and similar to the 15 mg CH4 m(-2)-min(-1) estimated by (Zahn et al., 2001)., (Copyright © 2015 Elsevier Ltd. All rights reserved.)