Can multiple short-term measures of methane be used to quantify daily methane emissions: beef cattle

Summary

​The GreenFeed Emissions Monitoring (GEM) devices are unique patented tools which use a 'bait station' to attract individual cattle to a small feeding booth in which their CO2 and CH4 emissions are measured over 3‐5 minutes, 5‐10 times per day.
They can be used to determine total CH4 production, total CO2 production, and also differentiate
CO2 arising from mammalian respiration, from that arising from rumen fermentation.
This study evaluated a GEM unit using supplement and a GEM unit using water as the baits.
With appropriate filtering, the estimate of daily emissions from the two units was within 1% of each other.
A comparison of GEM measured emissions and Calorimeter measured emissions from cattle was slightly confounded by reduced intake on days when cattle were in chambers, however the methane yields (g CH4/kg DMI) were very similar between the two systems.
Emissions form individual animals were remarkably stable over time (CV < 6%)
Recovery of a carbon dioxide pulse (as a test gas) through the GEM unit was 99%
We are convinced that the GEM units can, with appropriate control, provide an accurate measure of daily methane emissions period, based on our and New Zealand (not included) data.
We have had continuous assistance during these studies by the GEM manufacture team.
We have also made substantial progress in how to introduce animals to the GEM units and get the animals using them well.
However, there are some weak points in the GEM armour that need to be improved.
Large (daily) dependence on manufactures to process and quality check data. While this is helpful in this testing stage, it is not realistic or helpful if such support was found to be essential for data to be collected into the future. We have received continuous assurance that they will equip us for independent operation…but we are not there yet.
A large number of hardware failures/replacements that have needed to be 'talked through' and use software patches from USA. While we expect these are just teething troubles with a new unit and have come to an end, IF such intensive input were an ongoing need would preclude use of the units in all but the most managed environments in which a technician is always on hand.
An intensive calibration schedule of sensors is required that again mean the current GEM units are not devices that can be parked in the paddock, switched on (to 12v power) and abandoned with an expectation that data will appear in your email every day.
Low supplement holding capacity and general construction standard that is less robust than would be required for use in harsh environments (eg. exposed cabling, heavy use of plastics and silicon sealant)
We have held discussions with C‐Lock about increasing the level of auto‐calibration to allow use in more remote environments and in the absence of skilled technical staff.
In summary, the GEM device have brought new possibilities for in‐paddock emissions measurement that will provide a powerful capability for validating emissions and mitigation 4 levels, while also providing a valuable tool for feed efficiency research.​