The greenhouse gas methane: measuring emission from cattle

Janne Karin Brodin

Researchers at the Department of Animal and Aquacultural Sciences (IHA) at Norwegian University of Life Sciences (UMB) are about to start using a method for measuring the emission of methane from cattle. Until now, calculations for the Norwegian greenhouse gas accounts have been using equations based on figures from other countries in order to estimate greenhouse gas emissions from animal husbandry.

Differences in production and feeding regimes make it likely that these figures do not reflect actual greenhouse gas emissions from Norwegian livestock production.

In Norway, agriculture represents approximately 9 % of greenhouse gas emissions measured as CO2 equivalents. Emissions from livestock production make up a significant part of this – not only from the animals themselves, but also from connected processes. Methane (CH4) from animal husbandry itself makes up 48 % of the total emission of methane in Norway. In addition to that, livestock farming produces nitrous oxide (N2O) and ammonia (NH3) from manure. Methane and nitrous oxide are powerful greenhouse gases and have an effect that is 23 and 296 times stronger respectively than carbon dioxide. This means that emissions from animal husbandry play a not insignificant part in Norway’s total greenhouse gas balance.

The production of methane and secretion of nitrogen in the manure from ruminants depend on the feed the animals are given. Methane is secreted via exhalation and regurgitation of air from the rumen. The gas is then released via the cowshed’s ventilation system. Other aspects, such as how the manure is handled, will also influence the total quantity of methane released in the cowshed.

Cooperation with Canadian researchers
Researchers at Lethbridge Research Centre in Alberta, Canada have long experience in measuring methane emissions from livestock. At IHA, a group of researchers led by professor Odd Magne Harstad have established cooperation with the Canadian researchers, among them professor Tim McAllister and dr. Alexandre Chaves. This cooperation has led to mutual visits in order to start, among other things, experiments on registering methane emissions from ruminants in Norway.

How it is done
IHA has well established research facilities for metabolism and digestion experiments on ruminants, facilities which will be important for the measuring of methane emissions. The equipment used will make it possible for researchers to measure the quantity of methane produced by the individual cow. A capsule containing a marker will be placed in the rumen. The marker will be released over time. Samples are then taken from the air that the cow breathes out and regurgitates from the rumen. The samples are analyzed for methane and marker content, and the daily quantity of methane is calculated.

A hose leads from the halter to the white container above the cow Photo: Janne Brodin

Methane release is measured via a halter with a tube attached. The tune leads to a container with a constant pressure, which siphons off parts of the air that the cow exhales and regurgitates.The air is collected in the container. The container is replaced once a day and air samples are taken out and analyzed for methane and marker content.

Cow with a halter collecting information about metan production Photo: Janne Brodin

For several reasons, methane production varies
Roughage harvest time, feed ration composition (roughage:concentrate), additives in the feed and feed production processes are very important factors influencing the quantity of methane which is released when the cow has eaten the feed. It is possible to influence individual factors so that methane production is reduced, but it has been shown that such steps may have a negative impact on other areas, such as reduced digestibility, which again gives a higher quantity of nutrient release through manure.

Where to go from here
Research on greenhouse gas emission from livestock production is at the starting line in Norway. In the autumn of 2007, the Ruminant physiology and nutrition group at IHA arranged a seminar on greenhouse gases from livestock farming, and contributed to a report on knowledge status and required research on greenhouse gases and bioenergy from agriculture – (“Klimagasser og bioenergi fra landbruket – kunnskapsstatus og forskningsbehov”) at UMB. The practical work on establishing measuring techniques for methane is now well under way at IHA. In order to be able to contribute more accurate figures to the greenhouse gas accounts, one of the main tasks in the time ahead will be to chart methane emissions based on Norwegian feed rations. As the only ones in Norway, the IHA researchers will also apply themselves to looking into the total production of greenhouse gases in livestock buildings methane as well as nitrous oxide. The first step is bovine methane emission measurements, which starts at IHA in March 2008 in close collaboration with the Canadian researchers.

Updated: 16.12.09
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