Other methane measurement techniques provide estimates of emissions from individual animals. This raises the question whether the animals that have been measured are representative of average emissions coming from an entire herd over long periods of time.
Micro-meteorological techniques seek to address thi squestion directly, by measuring wind speed, direction and turbulence, as well as the concentration of methane in the air downwind from a flock of sheep or herd of cattle. These data are used to calculate the amount of methane generated by all livestock in a paddock.
WHY DO IT
One challenge for estimating total emissions across the country is the large variability between animals, and the high cost ofmeasuring individual animals. Only a relatively small number of animals can be measured individually, so estimates for an entire flock/herd or for the country as a whole have to make assumptions about typical emission rates per animal.
Paddock-scale measurements can be useful in checking whether measurements from individual animals can be multiplied torepresent emissions from a group of animals under typical farmmanagement.
CHALLENGES
This research is highly technical and still experimental.
Micro-meteorological techniques are labour intensive, mainly in setting up and running the highly specialised equipment.Measurements also depend on favourable wind conditions and suitable paddocks, and for methane, the emissions source (livestock) moves around, which can further reduce the precision of the method. Importantly, intake is also not known accurately, making comparisons between flocks/herds and over time difficult. It is hard to distinguish the methane produced by a single herd of cows or flock of sheep from methane in the air from other sources, and therefore the precision of the method is limited, making it difficult to verify small changes in emissions.