Development of a molecular dispersion spectroscopy instrument for livestock farming

Abstract

There is currently a clear demand for high-capacity gas measurement equipment across various fields. One sector that particularly stands out, primarily due to the necessity of reducing environmental impact, is livestock farming. However, there is currently no instrumentation available that can reliably undertake this challenging task. This article reports on a molecular dispersion spectroscopy instrument specifically engineered for livestock facilities to simultaneously measure methane (CH₄), ammonia (NH₃) and carbon dioxide (CO₂). In addition to its high temporal resolution, it is important to note that the use of optical spectroscopy allows the system to measure the average gas concentration along the optical path within the stables. This is highly advantageous over conventional point measurements typically used in this particular application. Furthermore, the implementation of dispersion spectroscopy confers the capacity for uninterrupted operation in environments characterized by elevated concentrations of suspended particulate matter. The method also ensures a high performance and linear response in the measurement of gas concentration, allowing for rapid adaptability to different measurement scenarios. Some quantitative indicators of performance found are linearity errors in the determination of concentration of < 0.1 % for CH₄ and CO₂ and 0.32 % for NH₃ (in a range that significantly exceeds the concentrations found experimentally) and detection limits < 35 ppb·m/Hz1/2 for all gases. Finally, the manuscript delineates the early stages of field testing conducted on a livestock farm, illustrating the achievement of suitable operational configurations and the promising initial results obtained with the instrument.