Implementation of Open-circuit Chambers for Monitoring Gas Emissions from Large Ruminants

摘要

To study the effect of mitigation strategies, the Animal Sciences Unit of the Institute for Agriculture and Fisheries Research has constructed six open-circuit chambers for monitoring gas emissions from large ruminants. The chambers were constructed from polypropylene panels around an internal stainless steel frame. In the chamber the floor was raised, to integrate a removable manure tray under the grid in the rear. Each chamber had large windows and three doors. The ventilation system was a mechanical central flow system. The airflow was monitored by a module integrated in the air exhaust of each chamber, that was equipped with an integrated full size free-running impeller, that continually measured the airflow, and a control damper that regulatesthe amount of air. The refresh rate was adjustable between 200 and 1300 m /hour. The methane (CH_4), carbon dioxide (CO_2), nitrous oxide (N_2O) and ammonia (NH_3) concentrations were measured with an interference free self-calibrating infrared laser optical-feedback cavity-enhanced absorption spectrometer, in the exhaust channels of each chamber. The detection ranges for CH_4, CO_2, N_2O and NH_3 are set between 0-700 ppm, 0-5000 ppm, 0-5 ppm, and 0-70 ppm respectively. The wholemeasuring system functioned at a continuous underpressure of 110 mbar, created by a sonic nozzle at the each sampling point. The system was continuously monitored for temperature, air flow, water, system pressure and gas concentrations. If values fall outside the set thresholds, the operator is warned via telephone.To our knowledge this is a unique and reliable system for measuring gas emissions in open-circuit chambers for large ruminants, with no interference between the gases and low maintenance costs.