Assessing Bovine Methane Emissions: Respiratory Simulation and Optical Gas Imaging Methods

Abstract

Bovine methane emissions contribute significantly to global greenhouse gas levels. Quantifying these emissions is of key importance in mitigating their production. This work investigates the physical simulation of cattle breaths and the assessment of their methane content through the use of optical gas imaging (OGI). A physical respiratory simulator was designed and built to replicate cow exhalations in controlled laboratory settings, successfully emulating breath flow, tidal volume, respiration rate, temperature, and methane concentration. The simulator was used in infrared imaging experiments that demonstrated the feasibility of using OGI as a technique for measuring breath methane content. To visualize breath gas plumes, image processing methods were developed, encompassing background subtraction, frame differencing, and optical flow. These methods enabled the characterization of plume intensity and movement dynamics under varying concentrations and temperatures. Quantification techniques were developed to compute a measure of breath methane content from thermal video footage. Detected methane intensity exhibited a positive linear correlation with breath methane concentration within the range of 1000 - 4000 ppm. The influence of breath exit temperature on detected methane intensity was found to be minimal, with intensity primarily scaling with the difference between ambient air temperature and background temperature. These observed trends were found to be in alignment with those predicted by theoretical models.