Manure amendments for mitigation of dairy ammonia and greenhouse gas emissions: preliminary screening

 Amendments can be practical and cost-effective for reducing ammonia [NH3] and greenhouse gas [GHG] emissions from dairy manure.  In this study, the effect of 22 amendments on NH3 and GHG carbon dioxide [CO2], methane [CH4] and nitrous oxide [N2O] emissions from dairy manure were simultaneous investigated at room temperature (20℃).  Dairy manure slurry (2 kg; 1:1.7 urine: feces; 12% total solids) was treated with various amendments, representing different classes of product, following the suppliers’ recommended rates.  In this screening of products, one sample of each amendment was evaluated along with untreated manure slurry with repeated measurements over 24 h.  Gas emissions were measured after short (3 d) and medium (30 d) storage duration using a photoacoustic multi-gas analyzer.  Six amendment products that acted as microbial digest, oxidizing agent, masking agent or adsorbent significantly reduced NH3 by >10% (P = 0.04 to <0.001) after both 3 and 30 d.  Microbial digest/enzymes with nitrogen substrate appeared effective in reducing CH4 fluxes for both storage times.  Most of the masking agents and disinfectants significantly increased CH4 in both storage periods (P = 0.04 to <0.001).  For both CH4 and CO2 fluxes, aging the manure slurry for 30 d significantly reduced gas production by 11 to 100% (P<0.001).  While some products reduced emissions at one or both storage times, results showed that the ability of amendments to mitigate emissions from dairy manure is finite and re-application may be required even for a static amount of manure.  Simultaneous measurement of gases identified glycerol as a successful NH3 reduction agent while increasing CH4 in contrast to a digestive-microbial product that significantly reduced CH4 while enhancing NH3 release.Keywords: methane, greenhouse gas, emission, amendment, additive, dairy manure, ammonia, mitigatio

Evaluation of odor emissions from amended dairy manure: preliminary screening

Manure amendments have shown variable effectiveness in reducing odor.  Twenty-two amendments were applied to dairy manure then evaluated for odor reduction efficacy after storage at 20℃ for 3 d and 30 d.  Amendments represented differing primary modes of action including: microbial digestive, oxidizing, disinfecting, masking, and adsorbent.  Each amendment was added to 2 kg dairy manure (1:1.7 urine:feces; 12% total solids) following recommended rates.  In this preliminary screening, one sample (n=1) of each amendment was evaluated along with untreated manure (Control).  Odor emission from each treated manure and Control was estimated twice by five or six qualified odor assessors (n=10 or 12) after each storage duration, using an international standard for triangular forced-choice olfactometry.  Odor quality was defined using hedonic tone, Labeled Magnitude Scale and ASTM methods for supra-threshold odor intensity, and an odor character wheel for descriptors.  For selected treatments, odor emissions were significantly reduced relative to Control at 30 d versus 3 d incubation (P<0.0001).  However, no amendment was significantly effective for both incubation times.  Likewise, for all amendments tested, aging the manure slurry for 30 d significantly reduced odor emission and odor intensity (P<0.0001).  A proprietary microbial amendment (Alken Enz-Odor + Clear Flo: aerobic/ facultative microbes with growth factors), disinfectant (hydrogen peroxide), and masking agent (Hyssopus officinalis essential oil) provided significant short-term control of odor (P <0.06).  However, after 30 d seven amendments significantly increased odor emission (P<0.02) while only two amendments offered a significant efficacy (P<0.0001): a proprietary microbial aerobic/facultative product (Bio-Regen) and a proprietary mix of chemicals (Greaseater), both with weekly re-application.  Hedonic tone observations suggested an improvement to “slightly to moderately unpleasant” smell versus untreated manure for all amendments except clinoptilolite zeolite adsorbent.  Hedonic tone improvement was correlated with reduced manure odor supra-threshold intensity.Keywords: odor, hedonic tone, odor strength, amendments, additives, dairy manure, United States of Americ

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 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

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

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