Greenfeed

GreenFeed (C-Lock Inc., Rapid City, South Dakota, USA) is a sniffer system where breath samples are provided when animals visit a bait station (Huhtanen et al., 2015). GreenFeed

Emission Monitoring (GEM) systems are designed for measuring animal emissions in their production environment. As with other sniffer systems, GreenFeed samples breath from individual animals several times (in general 4 to 6 times) per day for short periods (3 to 7 minutes in which an under pressure is created to suck the whole breath of the animal to measure the flux). They record CH4 and carbon dioxide (CO2) fluxes during short-term periods of 3-10 minutes when cattle visit an automated feeder fitted with a semi-enclosed head hood in which air is continuously drawn through an air-collection pipe (C-Lock, 2016; Huhtanen et al., 2015; Hammond et al., 2016A; Velazco et al., 2016). Air samples are continually (every second) analyzed for CH4 and CO2 concentrations using non-dispersive infrared sensors. Gas fluxes are eventually calculated as the product of the air flow in the collection pipe and the concentration of gases corrected for the background concentrations and adjusted to standardized temperature, humidity and pressure. The position of the head in the feeder is detected by an infrared sensor. Gas fluxes are not calculated if the head is not correctly positioned in the feeder as not all the air in the feeder may be collected. GreenFeed is a portable standalone system used in barn and pasture applications and incorporates an extractor fan to ensure active airflow and head position sensing for representative breath sampling (Hammond et al., 2016B). Measurements are pre-processed by the manufacturer, and data are available in real-time through a web-based data management system (Hammond et al., 2015). Because GreenFeed captures a high proportion of emitted air and measures airflow, which can be calibrated using a tracer gas, CH4 emission is estimated as a flux at each visit. Providing visits occur throughout the 24 hours, CH4 emission can be estimated directly as g/day (Hammond et al., 2015; Huhtanen et al., 2015). More importantly, repeatability of CH4 measurement must be high so the duration of the measurement period must be taken into account (Huhtanen et al., 2013; Arbre et al., 2016); (R=0.7 after 17 days duration of measurement period, or R=0.93 after 45 days, Arbre et al., 2016).