Reliable low-cost devices for monitoring ammonia concentrations and emissions in naturally ventilated dairy barns

Exploring use of a commercial passive sampler in a closed static chamber to measure ammonia volatilization

Studies have indicated that up to 47% of total N fertilizer applied in flooded rice fields may be lost to the atmosphere through NH3 volatilization. The volatilized NH3 represents monetary loss and contributes to increase in formation of PM2.5 in the atmosphere, eutrophication in surface water, and degrades water and soil quality. The NH3 is also a precursor to N2O formation. Thus, it is important to monitor NH3 volatilization from fertilized and flooded rice fields. Commercially available samplers offer ease of transportation and installation, and thus, may be considered as NH3 absorbents for the static chamber method. Hence, the objective of this study is to investigate the use of a commercially available NH3 sampler/absorbent (i.e., Ogawa® passive sampler) for implementation in a static chamber. In this study, forty closed static chambers were used to study two factors (i.e., trapping methods, exposure duration) arranged in a Randomized Complete Block Design. The three trapping methods are standard boric acid solution, Ogawa® passive sampler with acid-coated pads and exposed coated pads without casing. The exposure durations are 1 and 4 h. Results suggest that different levels of absorbed NH3 was obtained for each of the trapping methods. Highest level of NH3 was trapped by the standard boric acid solution, followed by the exposed acid-coated pads without casing, and finally acid-coated pads with protective casing, given the same exposure duration. The differences in absorbed NH3 under same conditions does not warrant direct comparison across the different trapping methods. Any three trapping methods can be used for conducting studies to compare multi-treatments using the static chamber method, provided the same trapping method is applied for all chambers.

Analysis of the Horizontal Distribution of Sampling Points for Gas Concentrations Monitoring in an Open-Sided Dairy Barn

In the livestock sector, the monitoring of gas concentrations plays a relevant role in the implementation of mitigation strategies, as well as the improvement in the indoor air quality for both workers and animals in barns. In the present study, measurements of gas concentrations (NH3, CH4, and CO2) at different locations were carried out in an open dairy barn using a commercial photo-acoustic spectroscopy system. Measurement variability for different datasets was computed to contribute to the evaluation of the sampling strategy in the measurement campaign. The results showed that the position of sampling locations (SLs) significantly influenced (p < 0.001) the variability in the gas distribution. Specifically, the SLs located on the perimeter of the building had the highest variability. The number of SLs utilised for determining the mean value of gas concentration in the barn had a significant influence on NH3 (p < 0.001), CO2 (p < 0.001), and CH4 (p < 0.001) in both the central zone and the perimeter one. At least three SLs were necessary to obtain a mean value of gas concentration that reduced the variability to under the 10% in the central zone and 16% in the perimeter one. Moreover, the NH3 concentrations obtained as the mean value of the gas measurements at two SLs with a 10 m distance had a lower variability compared to those recorded at two SLs located at 5 m.

Ammonia mitigation potential in an optimized crop-layer production system

Livestock and crop production are the main sources of ammonia (NH₃) emissions, which are known to degrade the air quality. Numerous studies have been conducted to explore the mitigation potential of various approaches, although few have examined the systematic NH₃ emission mitigation potential when considering both crop and livestock systems based on coherent in situ measurement results. Herein, we design an optimal system wherein coupled crop and layer production systems reveal feasible approaches for significant mitigation potential at each stage of the process. Specifically, these measures involve (i) using a low crude protein (LCP) feed, (ii) composting manure with certain additives, and (iii) substituting manure with optimal fertilization in a summer maize-winter wheat cropping system. The results show that (i) LCP feed leads to a 14 % reduction in NH₃ emissions at the housing stage, (ii) introducing additives during the composing stage reduces NH₃ emissions by 16 %-46 %, and (iii) the NH₃ reduction potential reaches 35 %-44 % at the field application stage. In the overall crop-layer system, the optimal system with the improved management strategy applied at every stage results in a 48 % and 56 % reduction in NH₃ emissions for per unit eggs and grain production, respectively, relative to a traditional production system. This study confirms that NH₃ emissions can be cut in half by implementing optimal crop-livestock systems with appropriate mitigation approaches. This is a feasible model that can be promoted and extended in various agricultural areas, which together with technological, policy, and economic support can enable significant mitigation potential for sustainable agriculture development.

Assessing Influence Factors on Daily Ammonia and Greenhouse Gas Concentrations from an Open-Sided Cubicle Barn in Hot Mediterranean Climate

Simple Summary

Gas concentration is a relevant parameter for the estimation of emissions in dairy farms, but few studies have investigated the influence of cow behavior and barn management on gas concentrations in open buildings. In this study, concentrations of ammonia, methane, and carbon dioxide were investigated in an open dairy barn in a hot Mediterranean climate. Since hot climate conditions cause heat stress to the cows, gas concentrations were statistically analyzed to assess whether variation of environmental and animal-related parameters produced significant effects on the level of gas concentrations in the barn environment. In this study, it was statistically proved that daily gas concentrations were influenced by both the effect of micro-climate conditions, connected with the barn typology, and of barn management on the animals. Therefore, the mitigation strategies for the reduction of these gases could be pursued through the improvement of the barn management aimed at modifying cow behavior and through the control of climatic conditions in relation to the building features.

Abstract

Measurement of gas concentrations constitutes basic knowledge for the computation of emissions from livestock buildings. Although it is well known that hot climate conditions increase gas emissions, in the literature the relation between gas concentrations from open barns and animal-related parameters has not been investigated yet. This study aimed at filling this gap by evaluating daily gas concentrations within an open-sided barn in hot Mediterranean climate. The influence of microclimatic parameters (MC) and cow behavior and barn management (CBBM) were evaluated for ammonia (NH₃), methane (CH₄), and carbon dioxide (CO₂) concentrations. Results showed that both MC and CBBM affected concentrations of NH₃ (p < 0.02), CH₄ (p < 0.001), and CO₂ (p < 0.001). Higher values of NH₃ concentration were detected during the cleaning of the floor by a tractor with scraper, whereas the lowest NH₃ concentrations were recorded during animal lying behavior. Measured values of CO₂ and CH₄ were highly correlated (C = 0.87–0.89) due to the same sources of production (i.e., digestion and respiration). The different management of the cooling systems during the two observation periods reduced significantly CH₄ concentrations in the barn when the cooling system in the feeding area was switched off. Based on methodological choices due to the specific barn typology, parameters related to animals can provide information on the variation of gas concentrations in the barn environment in hot climate conditions.

Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building

The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to +97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.

Characterization of particulate and gaseous pollutants from a French dairy and sheep farm

Agricultural activities highly contribute to atmospheric pollution, but the diversity and the magnitude of their emissions are still subject to large uncertainties. A field measurement campaign was conducted to characterize gaseous and particulate emissions from an experimental farm in France containing a sheep pen and a dairy stable. During the campaign, more than four hundred volatile organic compounds (VOCs) were characterized using an original combination of online and off-line measurements. Carbon dioxide (CO₂) and ammonia (NH₃) were the most concentrated compounds inside the buildings, followed by methanol, acetic acid and acetaldehyde. A CO₂ mass balance model was used to estimate NH₃ and VOC emission rates. To our knowledge, this study constitutes the first evaluation of emission rates for most of the identified VOCs. The measurements show that the dairy stable emitted more VOCs than the sheep pen. Despite strong VOC and NH₃ emissions, the chemical composition of particles indicates that gaseous farm emissions do not affect the loading of fine particles inside the farm and is mainly explained by the low residence time inside the buildings. The experimental dataset obtained in this work will help to improve emissions inventories for agricultural activities.

Ammonia sensing by closely packed WO3 microspheres with oxygen vacancies

Ammonia (NH₃), is a precursor for the formation of atmospheric fine particulate matter (PM_2.5), and thus establishing efficient and cost-effective methods to detect ammonia emission is highly desired. Transition metal oxide semiconductors-based sensors for electrochemical gas sensing have been extensively explored. Among various types of semiconductors, tungsten oxide (WO₃) possesses an anisotropic layered crystalline structure and is recognized as a promising material for gas sensing. However, the performance of commercial WO₃ is unsatisfactory because of its high impedance and low charge transportation efficiency. Thus, the modification of commercial WO₃ is needed to make it an efficient ammonia sensor material. In this work, closely packed WO₃ microspheres with oxygen vacancies were synthesized successfully through a novel two-step hydrothermal route. Our WO₃ showed a good selectivity to ammonia sensing, and its response intensity was 2.6 times higher than that of commercial WO₃ because of its optimized conductivity. Moreover, the mechanism behind its robust ammonia sensing performance was elucidated. The effectiveness of the as-prepared WO₃ microspheres for ammonia sensing also suggests a new strategy for modifying transition metal oxide materials.