Methane is a greenhouse gas that is approximately 21 times more potent than carbon dioxide. Methane is produced both naturally and through man-made processes. Most commonly associated with farting cows (it's actually burping cows) methane is also produced by industrial processes, termites, from landfill, rice growing and fossil fuel use.
But how much methane do cattle produce in Australia? The current National Greenhouse Gas Inventory calculates that 15% of the national inventory is from agriculture, of which 66% is from livestock digestion (mainly from cattle and sheep). These calculations are based on modelling and averages. The modelling for the national inventory can be updated as research reveals more accurate data for the models.
Recent research by Ed Charmley from CSIRO has found that northern cattle in Australia produce 30% less methane than previously thought. The CSIRO research is currently being reviewed for use in the next inventory and could mean that the Australian livestock industry's impact is revised to be lower than previously thought. These figures are still averaged across the northern herd and it's extremely unlikely that there will ever be a system to measure methane produced from cattle at a local level due to the complexities and costs associated with methane measurement.
How is methane from cows measured?
Methane gas measurement from livestock is a relatively new science and as such reliable methods and data are not yet available. The science is continually evolving and as more research is completed, the data becomes more and more reliable.
Measuring methane in controlled environments, like closed chambers in a lab is now at a stage that the data is quite reliable. However, measuring cattle and sheep in a lab is not an accurate measurement, as the animals are not behaving how they do in a field and as such the data is not a true reflection of animals' methane production.
To measure how much methane animals produce that are grazing, a variety of technologies have been trialled and used in recent years. To date the most effective method of measuring methane produced by cattle in field is an open-path fourier transformer infrared laser or FTIR. The FTIR operates by sending an infrared beam across a paddock, adjacent to and downwind from the grazing animals. The beam is reflected by a mirror back to the instrument.
To get an accurate reading a small gas canister which releases a tracer gas at a known rate is attached to the animals, and the instrument measures the amount of both the tracer gas and the methane from the animals simultaneously in the air between the instrument and the mirror to determine the amount of methane released from the animals.
The FTIR is the measuring instrument that was used by CSIRO for the study that found the northern herd produces 30% less methane than previously thought and is also being used at three other test sites across the country that are being used to quantify methane production and also demonstrate some of the research Australian agricultural scientists are undertaking to find ways to reduce methane production from cattle and sheep.
Methane levels on the average Australian farm have stayed relatively stable despite increases in livestock number nationally. To find out more information please visit http://www.redmeatgreenfacts.com.au
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