Download Methane emissions

Methane emissions
This is a new policy addressing concerns regarding methane emissions
Policy
Research into reducing methane emissions from livestock production is encouraged. Nevertheless,
emissions from livestock on Australian farms should not be incorporated into a carbon pollution
reduction scheme or carbon tax because methane from cattle is part of the biogenic carbon cycle.
Background
Methane is a greenhouse gas that is produced and released from biogenic and non-biogenic sources.
Some of the biogenic sources include the enteric fermentation of plant material by animals, plant
degradation in wetlands and the breakdown of animal waste products.
Livestock are considered one of the larger anthropogenic contributors of methane. Methane is
considered a major greenhouse gas, being 21 times more potent than carbon dioxide on a molecular
basis.1 However, methane has a net lifetime in the atmosphere of only 8.3 ± 1.7 years, after which it
converts back to carbon dioxide and water.2 Methane production has been part of the biogenic carbon
cycle from animals and plants for millions of years.
Livestock numbers in Australia have reduced significantly compared with previous years. The number of
beef cattle has dropped since 1978, when there were 29.8 million head, to 24.3 million in 2009. Dairy
cattle numbers have also dropped from 2.17 million in 1999 to 1.6 million head in 2009. Sheep numbers
have declined from 179 million sheep in 1970 to 72.7 million sheep in 2009.3 As such, the methane
levels in the atmosphere due to Australian livestock have actually reduced over the past 30 years.4 The
carbon dioxide produced by these livestock through respiration and methane breakdown is part of the
biological carbon cycle of plant growth and consumption, and does not represent an increased level
compared with carbon dioxide produced by fossil fuels.
Reducing methane levels has been seen as a quick fix for reducing greenhouse gas levels. However,
this would only represent a short-term solution. Efforts to combat global warming, more importantly,
should be made in areas that form part of the non-biogenic carbon cycle such as the use of fossil fuels
and cement production. Other areas of focus should include stopping the removal of natural carbon
reservoirs, such as ceasing deforestation.
References
1. Moss AR, Jouany J-P, Newbold J. Methane production by ruminants: its contribution to global
warming. Annales De Zootechnie 2000;49:231–253.
2. Intergovernmental Panel of Climate Change. IPCC Fourth Assessment Report: Climate Change
2007: Working Group I: The Physical Science Basis. Retrieved March 24, 2012, from IPCC:
www.ipcc.ch/publications_and_data/ar4/wg1/en/ch7s7-4-1.html.
3. Australian Bureau of Statistics. www.abs.gov.au
4. Australian Government Department of Climate Change and Energy Efficiency. National
greenhouse gas inventory. http://ageis.climatechange.gov.au/ Accessed 21 March 2012.
5. Martin C, Morgavi DP. Methane mitigation in ruminants from microbe to the farm scale.
Cambridge University Press, 2010.