Compaction effects on greenhouse gas and ammonia emissions from solid dairy manure.

Waste management practices of solid dairy manures were evaluated under controlled conditions to study gas transport and emission inside manure piles. Three applied stresses and three moisture contents were tested to represent manure conditions managed at various pile depths. A Fourier-transform infrared spectroscopy monitor measured concentrations of greenhouses gases [methane, carbon dioxide, and nitrous oxide] and ammonia as part of gas flux rate calculations. Results showed that carbon dioxide dominated the greenhouse gas emissions under all test conditions. Gas transfer, primarily diffusion, was facilitated by manure with high mechanical strength and high permeability. Gas emission rates reduced dramatically when moisture content increased in manure with high water holding capacity, while compaction treatments did not as strongly affect the gas emission rates. Results provide fundamental insights into management strategies for reducing gas emissions from solid dairy manure.

Correction: Chen et al. Computational Fluid Dynamics Analysis of Alternative Ventilation Schemes in Cage-Free Poultry Housing. Animals 2021, 11, 2352.

There was an error in the original publication [...].

Numerical Simulation of Airborne Disease Spread in Cage-Free Hen Housing with Multiple Ventilation Options.

The current ventilation designs of poultry barns have been present deficiencies with respect to the capacity to protect against disease exposure, especially during epidemic events. An evolution of ventilation options is needed in the egg industry to keep pace with the advancing transition to cage-free production. In this study, we analyzed the performances of four ventilation schemes for constraining airborne disease spread in a commercial cage-free hen house using computational fluid dynamics (CFD) modeling. In total, four three-dimensional models were developed to compare a standard ventilation configuration (top-wall inlet sidewall exhaust, TISE) with three alternative designs, all with mid-wall inlet and a central vertical exhaust. A one-eighth scale commercial floor-raised hen house with 2365 hens served as the model. Each ventilation configuration simulated airflow and surrogate airborne virus particle spread, assuming the initial virus was introduced from upwind inlets. Simulation outputs predicted the MICE and MIAE models maintained a reduced average bird level at 47% and 24%, respectively, of the standard TISE model, although the MIRE model predicted comparable virus mass fraction levels with TISE. These numerical differences unveiled the critical role of centrally located vertical exhaust in removing contaminated, virus-laden air from the birds housing environment. Moreover, the auxiliary attic space in the MIAE model was beneficial for keeping virus particles above the bird-occupied floor area.

Computational Fluid Dynamics Analysis of Alternative Ventilation Schemes in Cage-Free Poultry Housing.

This work investigated alternative ventilation schemes to help define a proper ventilation system design in cage-free hen houses with the goal of assuring bird welfare through comfortable conditions. Computational fluid dynamics (CFD) modeling was employed to simulate indoor and outdoor airflows to quantify the effectiveness of ventilation systems in maintaining suitable and uniform living conditions at the hen level. Four three-dimensional CFD models were developed based on a full-scale floor-raised layer house, corresponding to ventilation schemes of the standard top-wall inlet, sidewall exhaust, and three alternatives: mid-wall inlet, ceiling exhaust; mid-wall inlet, ridge exhaust; and mid-wall inlet, attic exhaust with potential for pre-treatment of exhaust air. In a sophisticated and powerful achievement of the analysis, 2365 birds were individually modeled with simplified bird-shapes to represent a realistic number, body heat, and airflow obstruction of hens housed. The simulated ventilation rate for the layer house models was 1.9-2.0 m3/s (4100 ft3/min) in the desired range for cold weather (0 °C). Simulation results and subsequent analyses demonstrated that these alternative models had the capacity to create satisfactory comfortable temperature and air velocity at the hen level. A full-scale CFD model with individual hen models presented robustness in evaluating bird welfare conditions.

Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility.

Poultry facilities are going through an evolution in design due to growing demands for cage-free eggs and egg products without unified guidelines to accommodate these transitions. The goal of this study was to help builders and egg producers assess current ventilation design within cage-free production facilities for conditions that impact hen comfort and welfare. The method of evaluation was simulation of the indoor environment of a hen house via computational fluid dynamics (CFD) modeling with individual hens modeled at a typical stocking density. This paper describes the development of a three-dimensional model of a commercial floor-raised cage-free hen house that is cross-ventilated to document current environmental conditions. A one-eighth section of the barn was modeled at full-scale using existing ventilation schemes with each bird represented by a hen-shaped, heated, solid body. A conventional top-wall inlet, side-wall exhaust (TISE) ventilation configuration was modeled for this study. The simulated ventilation rate for the hen house was approximately 3 m3/h (1.77 ft3/min) per hen resulting in 7092 m3/h (4174 ft3/min) for the 2365 birds, which falls at the higher end of the desired cold weather (0 °C) ventilation range. Contours of airflow, temperature, and pressure were generated to visualize results. Three two-dimensional planes were created at representative cross-sections to evaluate the contours inside and outside the barn. Five animal-occupied zones within each of the model planes were evaluated for practical hen comfort attributes. The simulation output suggested the TISE standard ventilation system could limit air speed to a comfortable average of 0.26 m/s (51 ft/min) and the temperature could be maintained between 18 and 24 °C on average at the bird level. Additionally, the indoor static pressure difference was very uniform averaging -25 Pascal (0.1 inches of water), which falls in the normal range for a floor-raised hen house with negative-pressure ventilation during cold weather conditions. Findings confirmed that CFD modeling can be a powerful tool for studying ventilation system performance at the bird level, particularly when individual animals are modeled, to assure a comfortable indoor environment for animal welfare in poultry facilities.

Operator Exposure to Hydrogen Sulfide from Dairy Manure Storages Containing Gypsum Bedding.

Dairy manure storages containing gypsum-based bedding have been linked anecdotally with injury and death due to presumed dangerous levels of gases released. Recycled gypsum products are used as a cost-effective bedding alternative to improve animal welfare and provide agronomic benefits to manure recycled back to the land. Sulfur contained in gypsum (calcium sulfate) can contribute to hydrogen sulfide (H2S) gas formation under the anaerobic storage conditions typical of dairy manure slurry. Disturbance of stored manure during agitation releases a burst of volatile gases. On-farm monitoring was conducted to document conditions during manure storage agitation relative to gas concentration and operator safety. One objective was to document operator exposure to H2S levels; therefore, each operator wore a personal gas monitor while performing tasks associated with manure storage agitation. Data from three dairy bedding management categories on ten farms were compared: (1) traditional organic bedding, (2) gypsum bedding, and (3) gypsum bedding plus a manure additive thought to reduce H2S formation and/or release. Portable meters placed around the perimeter of dairy manure storages recorded H2S concentrations prior to and during 19 agitation events. Results show that farms using gypsum bedding produced higher H2S concentrations during manure storage agitation than farms using traditional bedding. In most cases, gypsum-containing manure storages produced H2S levels above recognized safe thresholds for both livestock and humans. Farm operators were most at risk during activities in close proximity to the manure storage during agitation, and conditions 10 m away from the storage were above the 20 ppm H2S threshold on some farms using gypsum bedding. Although H2S concentrations rose to dangerous levels, only two of 18 operators were exposed to >50 ppm H2S during the first 60 min of manure storage agitation. Operators who are aware of the risk of high H2S concentrations near gypsum-laden manure storages can reduce their exposure risk by working upwind and away from the H2S plume within a closed tractor cab.

Effects of Feeding Encapsulated Nitrate to Beef Cattle on Ammonia and Greenhouse Gas Emissions from Their Manure in a Short-Term Manure Storage System.

A study was conducted to investigate effects of feeding encapsulated nitrate (EN) to beef cattle on ammonia (NH) and greenhouse gas emissions from their manure. Eight beef heifers were randomly assigned to diets containing 0 (control), 1, 2, or 3% EN (55% forage dry matter; EN replaced encapsulated urea in the control diet and therefore all diets were iso-nitrogenous) in a replicated 4 × 4 Latin square design. Urine and feces collected from individual animals were reconstituted into manure and incubated over 156 h using a steady-state flux chamber system to monitor NH, methane (CH), carbon dioxide (CO), and nitrous oxide (NO) emissions. Urinary, fecal, and manure nitrate (NO)-N concentration linearly increased ( < 0.001) with feeding EN, and urinary urea concentration tended to be lower ( = 0.078) for EN versus Control. The hourly emissions of NH, CO, and NO (mg head h) were not affected, although NH emission rates tended to be lower ( = 0.070) for EN compared with Control at 0 to 12 h. Cumulative NH, CO, and NO emissions over 156 h were not affected, but CH emissions were less (4.5 vs. 7.4 g head; = 0.027) for EN compared with Control. In conclusion, although NH emissions were initially lower for EN manures, total NH emitted over 156 h was not affected. Dietary EN lowered CH emissions from manure, and, despite greater NO concentrations in EN manure, NO emissions were not affected in this short-term incubation.

Using minced horseradish roots and peroxides for the deodorization of swine manure: a pilot scale study.

Enzymes that have proven to be capable of removing toxic compounds from water and soil may also be useful in the deodorization of animal manures. Considering that pork production in the US is a $40-billion industry with over half a million workers, odor control to protect air quality in the neighboring communities must be considered an essential part of managing livestock facilities. This pilot scale (20-120 L) study tested the use of minced horseradish (Armoracia rusticana L.) roots (1:10 roots to swine slurry ratio), with calcium peroxide (CaO(2) at 34 mM) or hydrogen peroxide (H(2)O(2) at 68 mM), to deodorize swine slurry taken from a 40,000-gallon storage pit at the Pennsylvania State University's Swine Center. Horseradish is known to contain large amounts of peroxidase, an enzyme that, in the presence of peroxides, can polymerize phenolic odorants and thus reduce the malodor. Twelve compounds commonly associated with malodor (seven volatile fatty acids or VFAs, three phenolic compounds and two indolic compounds) were used as odor indicators. Their concentration in swine slurry before and after treatment was determined by gas chromatography (GC) to assess the deodorization effect. The pilot scale testing demonstrated a complete removal of phenolic odorants (with a detection limit of 0.5 mg L(-1)) from the swine slurry, which was consistent with our previous laboratory experiments using 30-mL swine slurry samples. Horseradish could be recycled (reused) five times while retaining significant reduction in the concentration of phenolic odorants. In view of these findings, inexpensive plant materials, such as horseradish, represent a promising tool for eliminating phenolic odorants from swine slurry.

Deodorization of swine manure using minced horseradish roots and peroxides.

Public concerns about offensive odors from livestock manures are on the rise and so is the pressure to develop practical ways to reduce the odors. The use of minced horseradish (Armoracia rusticanaL) roots (1:10 w/v plant tissue to swine slurry ratio), with calcium peroxide (CaO2 at 26 or 34 mM) or hydrogen peroxide (H2O2 at 34, 52, or 68 mM) for the deodorization of swine manure, was evaluated through a series of laboratory experiments. The principle underlying this deodorization method is the oxidation of odorants by the concerted action of horseradish peroxidase (present in the plant tissue) and peroxide that serves as an electron acceptor, followed by polymerization of phenolic odorants with a possible copolymerization or adsorption of other odorant compounds. The deodorization effect was assessed by a human panel and gas chromatography (GC). In the case of the GC method, 12 compounds commonly associated with malodor (7 volatile fatty acids or VFAs, 3 phenolic compounds, and 2 indolic compounds) were used as odor indicators. Malodor assessment of the treated slurry by a human panel indicated a 50% reduction in odor intensity. GC results showed 100% removal of all phenolic odorants without reoccurrence for at least 72 h. In view of these data, using plant materials as enzyme carriers and peroxides as electron acceptors emerges as an effective approach to phenolic odor control in animal manure.