Novel OA-ICOS Sensor for Real-Time Quantification of Enteric Methane from Ruminants

Methane (CH₄) is a potent greenhouse gas, with livestock rumination being a significant contributor to global emissions. This study developed a real-time monitoring system utilizing Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) to simultaneously track rumination behavior and CH₄ concentrations in cattle breath. By optimizing the off-axis integrated cavity structure and implementing a specialized environmental control system, we enhanced stability and detection accuracy, achieving a rapid 3 s response time to dynamic concentration changes. Laboratory stability tests and Allan deviation analysis demonstrated a minimum detection limit of 0.07 ppm. Continuous field monitoring of Simmental cattle revealed a daily methane production of approximately 311.83 L. The emission rates exhibited a distinct double-peak pattern heavily influenced by feeding schedules. Furthermore, a positive correlation was observed between the time elapsed post feeding and both the frequency and intensity of methane emission peaks. This method enables highly dynamic, stable, long-term monitoring of greenhouse gas emissions from ruminants, providing a robust tool for quantifying emissions and informing scientific feeding practices.