Search

Simple Summary: A-band ultraviolet (UVA) in solar radiation plays an important role in the natural decay of airborne bacteria. In this study, laboratory simulation experiments were conducted to investigate the impact of varied UVA intensities on the decay of airborne bacteria and to analyze the potential use of UVA to reduce indoor airborne bacteria in cattle houses. Decay and inactive rates of airborne bacteria from cattle sources increased with the UVA radiation intensities when the radiation was over 1500 μW cm−2, and it was affected by the initial concentration and radiation durations. Results of this study provide the foundation for further applying UVA as an alternative way to reduce indoor airborne bacteria in animal houses. Inspired by the effects of solar or UV radiation on the decay of airborne bacteria during their transport, this study investigated the effect of UVA on the decay of airborne bacteria from cattle houses and analyzed the potential use of UVA to reduce indoor airborne bacteria under laboratory conditions. Airborne bacteria from the cattle source were generated and released into a small-scale test chamber (1.5 m3) with different strategies according to the different objectives in decay tests and simulated sterilization tests. Increasing with the UVA radiation gradients (0, 500, 1000, 1500 μW cm−2), the average decay rate of total curable airborne bacteria ranged from 2.7% to 61.6% in decay tests. Under the combination of different UVA radiation intensities (2000 μW cm−2 in maximum) and radiation durations (60 min in maximum), simulated sterilization tests were conducted to examine the potential use of UVA radiation for air sterilization in animal houses. With the dynamic inactive rate (DIR) ranging from 17.2% to 62.4%, we proved that UVA may be an alternative way to reduce the indoor airborne bacteria in cattle houses if applied properly. Similar effects would be achieved using either a high radiation intensity with a short radiation duration or a low radiation intensity with a long radiation duration. [ABSTRACT FROM AUTHOR]

Low-profile, cross-ventilated (LPCV) dairy barns represent a modern trend in farm buildings but are associated with notable air quality challenges. To evaluate the annual variations in the pollutants in an LPCV dairy barn, an Internet-of-Things (IoT)-based environmental monitoring system was installed to continuously measure the total suspended particle (TSP), particle with aerodynamic diameters of ≤2.5 μm (PM2.5), and NH3 concentrations year round at multiple points. Spatiotemporal distributions and main factors were analyzed. The results showed that the annual average concentrations of indoor TSP, PM2.5, and NH3 were 86.4, 28.5, and 875.0 μg/m3, respectively. Corresponding emission rates were 140.6, 28.5, and 3461.1 mg/(h·cow). TSP concentrations were significantly higher during winter and spring (p < 0.05) and were elevated during daily operational hours, particularly in feeding alleys and downwind areas. Emissions were significantly higher in winter and summer (p < 0.05). Indoor PM2.5 concentrations in winter exceeded China's standards for 24.9% of the time, which were 2.2 times higher than those in other seasons (p < 0.05), peaking in the morning hours. NH3 concentrations and emissions were consistently high throughout the year, with peak levels in manure and downwind areas. The building's structure, ventilations, and daily operations were key factors affecting air pollutant levels, which need to be considered when implementing mitigation measures. [ABSTRACT FROM AUTHOR]

Long-term exposure to a relatively high concentration of airborne bacteria emitted from intensive livestock houses could potentially threaten the health and welfare of animals and workers. There is a dual effect of air sterilization and promotion of vitamin D synthesis for the specific bands of ultraviolet light. This study investigated the potential use of A-band ultraviolet (UVA) tubes as a clean and safe way of reducing airborne bacteria and improving calf health. The composition and emission characteristics of airborne bacteria were investigated and used to determine the correct operating regime of UVA tubes in calf houses. Intermittent exceedances of indoor airborne bacteria were observed in closed calf houses. The measured emission intensity of airborne bacteria was 1.13 ± 0.09 × 107 CFU h−1 per calf. Proteobacteria were the dominant microbial species in the air inside and outside calf houses. After UVA radiation, the indoor culturable airborne bacteria decreased in all particle size ranges of the Anderson sampler, and it showed the highest reduction rate in the size range of 3.3–4.7 μm. The results of this study would enrich the knowledge of the source characteristics of the airborne bacteria in intensive livestock farming and contribute to the environmental control of cattle in intensive livestock production. [ABSTRACT FROM AUTHOR]

The emission factor method (Tier 1) recommended by the Intergovernmental Panel on Climate Change (IPCC) is commonly used to estimate greenhouse gas (GHG) emissions from livestock and poultry farms. However, the estimation accuracy may vary due to practical differences in manure management across China. The objectives of this study were to estimate the direct and indirect nitrous oxide (N2O) emissions from dairy manure management between 1990 and 2021 in China and characterize its spatial and temporal variations following IPCC guideline Tier 2. The N2O emission factor (EF) of dairy cow manure management systems was determined at the national level and regional level as well. The results showed that the national cumulative N2O emission of manure management from 1990 to 2021 was 113.1million tons of CO2 equivalent, ranging from 90.3 to 135.9 million tons with an uncertainty of ±20.2%. The annual EF was 0.021 kg N2O-N (kg N)−1 for total emissions, while it was 0.014 kg N2O-N (kg N)−1 for direct emissions. The proportions of N2O emissions in North China, Northeast China, East China, Central and Southern China, Southwest China and Northwest China were 32.3%, 18.6%, 11.4%, 5.8%, 6.1% and 25.8%, respectively. In addition, N2O emissions varied among farms in different scales. The respective proportions of total N2O emissions from small-scale and large-scale farms were 64.8% and 35.2% in the past three decades. With the improvement in farm management and milk production efficiency, the N2O emissions per unit mass of milk decreased from 0.77 × 10−3 kg to 0.48 × 10−3 kg in 1990–2021. This study may provide important insights into compiling a GHG emission inventory and developing GHG emission reduction strategies for the dairy farming system in China. [ABSTRACT FROM AUTHOR]

Based on the experiments of isothermal forging wedge-shaped samples, Deform-3D numerical simulation software was used to confirm the strain distribution in the wedge-shaped samples. The effect of deforming temperature and strain on abnormal grain growth(AGG) in extruded FGH96 superalloy was examined. It is found that when the forging speed is 0.04 mm/s,the critical AGG occurring temperature is 1100℃,and the critical strain is 2%.AGG does not occur within 1000-1070℃,but still shows the feature of ‘critical strain’,and the region with strain of 5%-10% has the largest average grain size.AGG can be avoided and the uniform fine grains can be gained when the strain is not less than 15%.

A mixing fan and spraying system is commonly used to control the indoor environment of naturally ventilated dairy barns worldwide. However, its impact on particulate matter (PM) concentration and variation is still unclear due to the lack of year-round field data. To systematically characterize the PM dynamics under different environmental controls (namely, EC1: No Fans and No Spraying; EC2: Fans; EC3: Fans and Spraying), a year-round continuous monitoring of PM less than 2.5 μm in aerodynamic diameter (PM2.5) and total suspended particle (TSP) concentrations, as well as indoor environmental factors, was carried out inside a naturally ventilated dairy barn using an IoT-based sensor monitoring network. Results showed that the hourly mean TSP and PM2.5 concentrations were 94.7 μg m−3 and 49.8 μg m−3, respectively. EC2 had a higher TSP content (116.6 μg m−3) than EC1 (98.0 μg m−3) and EC3 (81.9 μg m−3). EC1 had the greatest PM2.5 concentration (57.1 μg m−3), followed by EC2 (48.3 μg m−3) and EC3 (44.7 μg m−3). EC1 showed clear TSP and PM2.5 fluctuations during the daily operations at 07:00 to 08:00 and 18:00 to 19:00, while irregular peaks in EC2 and a relatively steady diurnal variation in EC3 were found. Daily Tsp concentrations in the three ECs did not exceed 300 μg m−3. However, 17.8%, 11.5%, and 4.8% of the observed days in EC1, EC2, and EC3 had daily mean PM2.5 concentrations above the healthy threshold (75 μg m−3), mostly from 07:00 to 08:00 and 22:00–07:00. In conclusion, the mixing fan and spraying system had significant effects on PM concentration and variation, and more protection procedures should be taken for farm workers to prevent long-term health risk exposure, to EC1 in particular. [ABSTRACT FROM AUTHOR]

ABSTRACT Laboratory experiments were carried out in a wind tunnel with a model of a slurry pit to investigate the characteristics of ammonia emission from dairy cattle buildings with slatted [...]

Ammonia (NH3) concentrations in summer were continuously monitored from three typical laying hen houses of CC (conventional cage), AV (aviary), and NM (natural mating colony cage) with manure belt systems in North China Plain to quantify their emission levels, to characterize the diurnal variations, and to investigate the impact of environmental factors. Diurnal profiles were acquired by hourly measurements, and the effect of environmental factors on NH3 emissions was presented by correlation analysis. The results showed that house-level NH3 emissions in summer were the highest in the NM at 27.16 ± 13.12 mg/h·hen, followed by the AV at 4.08 ± 3.23 mg/h·hen and the CC at 3.43 ± 1.46 mg/h·hen within a complete manure removal cycle, which were significantly affected by manure accumulation inside the houses. After manure removal, NH3 concentrations were reduced by 64.29%, 28.57%, and 35.71% in CC, AV, and NM, and consequently their emissions were lowered by 67.12%, 71.36%, and 55.69%, respectively. It was suggested that the manure should not be stored on the belt for more than 4 days in NM. A positive impact of indoor and outdoor temperature and ventilation rate on NH3 emissions from AV and NM were found, while indoor and outdoor relative humidity had a negative effect. However, the above five factors did not significantly affect the emissions from CC. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) from poultry production facilities may strongly affect the health of animals and workers in the houses, and PM emitted to the ambient air is an important pollution source to the surrounding areas. Aviary system is considered as a welfare friendly production system for laying hens. However, its air quality is typically worse as compared with conventional cage systems, because of the higher PM concentration of indoor air and other airborne contaminants. Furthermore, PM's physical property, which has a direct impact on the penetration depth into the lungs of the birds and humans, is largely unknown for the aviary system. Therefore, a systematic method was utilized to investigate the characteristics of particles in the aviary house with large cage aviary unit system (LCAU) in Beijing, China. For the field measurements, three measuring locations were selected with two inside and one outside the house with LCAU to continuously monitor PM concentrations and collect the samples for particle size distribution (PSD) analysis. Results showed that PM2.5, PM10, and total suspended particulate (TSP) concentrations averaged at 0.037 ± 0.025 mg/m3, 0.42 ± 0.10 mg/m3, and 1.92 ± 1.91 mg/m3, respectively. Particle concentrations increased from October to December due to less ventilation as the weather got colder, and were generally affected by stocking density, ventilation rate, birds' activities, and housing system. Meanwhile, indoor PM2.5 concentration was easily impacted by the ambient air quality. Mass median diameter (MMD) and mass geometric standard deviation (MGSD) of the TSP during the measurement were 18.92 ± 7.08 μm and 3.11 ± 0.31, respectively. Count median diameter (CMD) and count geometric standard deviation (CGSD) were 1.94 ± 0.14 μm and 1.48 ± 0.08, respectively. Results indicated that the aviary system can attain a good indoor condition by suitable system design and environment control strategy. Implications: Indoor PM2.5 concentration of the layer house can be significantly affected by ambient air quality when the air quality index (AQI) was larger than 100. PM2.5 and PM10 concentrations of the layer house with a LCAU system were comparable to the cage system. TSP concentration was higher, and PM size was larger than most of the cage system. System design, larger space volume, and higher ventilation rate were the main influence factors. Good indoor environment of the aviary system can be achieved through the reasonable design of the production system and appropriate environment control strategy. [ABSTRACT FROM AUTHOR]

As a convenient method, the closed chamber method has been applied to determine gaseous emission fluxes from fully open animal feeding operations despite the measured fluxes being theoretically affected by deployment time, wind speed over the emitting surface and detected gas mass. This laboratory study evaluated the effects of deployment time (0 to 120 min) and external surface wind speed (ESWS) (0.00, 0.25, 0.50, 0.75, 1.00, 1.50 and 2.00 m sec-1) on the measurement accuracy of a 300 mm (diameter) × 400 mm (height) (D300×H400) closed chamber using methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) as reference gases. The results showed that the overall deviation ratio between the measured and reference CH4 fluxes ranged from 9.99 % to -37.32 % and the flux was overestimated in the first 20 min. The measured N2O and SF6 emissions were smaller than the reference fluxes using the chamber. N2O measurement accuracy decreased from -14.47 to -35.09% with deployment time extended to 120 min, while SF6 accuracy sharply increased in the first 40 min, with the deviation stabilizing at approximately -5.00%. CH4, N2O and SF6 measurements were significantly affected by deployment time and ESWS (P<0.05), and the interaction of those two factors greatly influenced CH4 and SF6 measurements (P<0.05). With the D300×H400 closed chamber, deployment times of 20 to 30 min and 10 to 20 min are recommended to measure CH4 and N2O, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec-1. Implications: This study recommended the suitable deployment times and wind speeds for using a D300 × H400 closed chamber to measure CH4, N2O, and SF6 in an open system, such as a dairy open lot and manure stockpile, to help researchers and other related industry workers get accurate data for gas emission rate. Deployment times of 20 to 30 min and 10 to 20 min were recommended to measure CH4 and N2O emissions using the D300 × H400 closed chamber, respectively, from the open operations of dairy farms under wind speeds lower than 2 m sec−1. For the measurement of SF6, a typical tracer gas, a deployment of 70 to 90 min was suggested. [ABSTRACT FROM AUTHOR]

Curtain-sided barns with circulation fans above stall are commonly used to house dairy cows in China. Many farms equipped with circulation fans are unable to provide appropriate cooling, especially for the naturally ventilated shed, which can result in decreasing feed intake and milk production. For alleviating heat stress and improving animal comfort, a system consisting of an air cooler and a 30 m perforated air duct (PAD) was integrated to evenly distribute cooling air. The air was cooled by underground water and delivered to targeted zones above stall bed. The system was evaluated in an open sided dairy barn in Tianjin, China. For the stalls equipped with PAD system, air velocity reached above 1.1 m/s at 0.5 m height plane of the stall space, and was more uniformly distributed. Compared to the stalls equipped with circulation fans, the PAD system lowered air temperature by 1.5°C, and increased relative humidity by 8.1%. On average, Temperature Humidity Index (THI) and Equivalent Temperature Index (ETI) were decreased by 0.5 and 0.6, respectively. After a 15 days' operation of the system, rectal temperatures of the treated dairy cows were significantly lowered. The results also showed that the cows under PADs had a higher milk production. These findings suggest the PAD can be an effective cooling alternative for naturally ventilated dairy barns to alleviate heat stress. [ABSTRACT FROM AUTHOR]

To investigate the impacts of major factors on carbon loss via gaseous emissions, carbon dioxide (CO2) and methane (CH4) emissions from the ground of open dairy lots were tested by a scale model experiment at various air temperatures (15, 25, and 35 °C), surface velocities (0.4, 0.7, 1.0, and 1.2 m sec−1), and floor types (unpaved soil floor and brick-paved floor) in controlled laboratory conditions using the wind tunnel method. Generally, CO2and CH4emissions were significantly enhanced with the increase of air temperature and velocity (P< 0.05). Floor type had different effects on the CO2and CH4emissions, which were also affected by air temperature and soil characteristics of the floor. Although different patterns were observed on CH4emission from the soil and brick floors at different air temperature-velocity combinations, statistical analysis showed no significant difference in CH4emissions from different floors (P> 0.05). For CO2, similar emissions were found from the soil and brick floors at 15 and 25 °C, whereas higher rates were detected from the brick floor at 35 °C (P< 0.05). Results showed that CH4emission from the scale model was exponentially related to CO2flux, which might be helpful in CH4emission estimation from manure management. Implications: Gaseous emissions from the open lots are largely dependent on outdoor climate, floor systems, and management practices, which are quite different from those indoors. This study assessed the effects of floor types and air velocities on CO2and CH4emissions from the open dairy lots at various temperatures by a wind tunnel. It provided some valuable information for decision-making and further studies on gaseous emissions from open lots. [ABSTRACT FROM AUTHOR]

The open lots and manure stockpiles of dairy farm are major sources of greenhouse gas (GHG) emissions in typical dairy cow housing and manure management system in China. GHG (CO2, CH4and N2O) emissions from the ground level of brick-paved open lots and uncovered manure stockpiles were estimated according to the field measurements of a typical dairy farm in Beijing by closed chambers in four consecutive seasons. Location variation and manure removal strategy impacts were assessed on GHG emissions from the open lots. Estimated CO2, CH4and N2O emissions from the ground level of the open lots were 137.5±64.7 kg hd-1yr-1, 0.45±0.21 kg hd-1yr-1and 0.13±0.08 kg hd-1yr-1, respectively. There were remarkable location variations of GHG emissions from different zones (cubicle zone vs. aisle zone) of the open lot. However, the emissions from the whole open lot were less affected by the locations. After manure removal, lower CH4but higher N2O emitted from the open lot. Estimated CO2, CH4and N2O emissions from stockpile with a stacking height of 55±12 cm were 858.9±375.8 kg hd-1yr-1, 8.5±5.4 kg hd-1yr-1and 2.3±1.1 kg hd-1yr-1, respectively. In situ storage duration, which estimated by manure volatile solid contents (VS), would affect GHG emissions from stockpiles. Much higher N2O was emitted from stockpiles in summer due to longer manure storage. Implications: This study deals with greenhouse gas (GHG) emissions from open lots and stockpiles. It’s an increasing area of concern in some livestock producing countries. The Intergovernmental Panel on Climate Change (IPCC) methodology is commonly used for estimation of national GHG emission inventories. There is a shortage of on-farm information to evaluate the accuracy of these equations and default emission factors. This work provides valuable information for improving accounting practices within China or for similar manure management practice in other countries. [ABSTRACT FROM PUBLISHER]

Reducing airborne microorganisms may potentially improve the environment in layer breeding houses. The effectiveness of slightly acidic electrolyzed water (SAEW; pH 5.29–6.30) in reducing airborne microorganisms was investigated in a commercial layer house in northern China. The building had a tunnel-ventilation system, with an evaporative cooling. The experimental area was divided into five zones along the length of the house, with zone 1 nearest to an evaporative cooling pad and zone 5 nearest to the fans. The air temperature, relative humidity, dust concentration, and microbial population were measured at the sampling points in the five zones during the study period. The SAEW was sprayed by workers in the whole house. A six-stage air microbial sampler was used to measure airborne microbial population. Results showed that the population of airborne bacteria and fungi were sharply reduced by 0.71 × 105and 2.82 × 103colony-forming units (CFU) m−3after 30 min exposure to SAEW, respectively. Compared with the benzalkonium chloride (BC) solution and povidone-iodine (PVP-I) solution treatments, the population reductions of airborne fungi treated by SAEW were significantly (P< 0.05) more, even though the three disinfectants can decrease both the airborne bacteria and fungi significantly (P< 0.05) 30 min after spraying.Implications: There are no effective methods for reducing airborne microbial levels in tunnel-ventilated layer breeding houses; additionally, there is limited information available on airborne microorganism distribution. This research investigated the spatial distribution of microbial population, and the effectiveness of spraying slightly acidic electrolyzed water in reducing microbial levels. The research revealed that slightly acidic electrolyzed water spray was a potential method for reducing microbial presence in layer houses. The knowledge gained in this research about the microbial population variations in the building may assist producers in managing the bird housing environment and engineers in designing poultry houses. [ABSTRACT FROM AUTHOR]