Greenhouse gas emissions of lamb production in Tasmania
Christie, KM and Rawnsley, RP and Smith, RW, Greenhouse gas emissions of lamb production in Tasmania, Proceedings of the Climate Change Research Strategies for Primary Industries Conference (CCRSPI) 2012, 27-29 November 2012, Melbourne Cricket Ground, Melbourne, Victoria, pp. 154-155. (2012) [Conference Extract]
The Australian red meat industry is committed to finding ways to reduce on-farm greenhouse gas (GHG) emissions through research and development. To achieve this there is a need for a whole of farm perspective on the GHG emissions contribution, based on best practice data acquisition and analysis. While there have been several GHG emissions studies undertaken for various sheep enterprises in other states of Australia (e.g. Howden et al. 1996; Peters et al. 2010; Alcock and Hegarty 2011), there appears to be few examples of assessments relating to either partial or whole-of-farm GHG emissions associated with lamb production in Tasmania. This study examined the GHG emissions associated with the lamb production component of a mixed lamb/cropping enterprise at Cressy (41.7°S, 147.1°E) in the Northern Midlands of Tasmania. The farm enterprise was segregated into two sub-enterprises; a home-bred lamb enterprise producing 1,572 lambs (34,630 kg dressed weight per annum) from 1,485 Poll Dorset cross Coopworth ewes and a purchased lamb enterprise producing 5,470 1st and 2nd cross prime lambs (accumulating 37,614 kg dressed weight on-farm per annum). Greenhouse gas emissions included pre-farm embedded emissions from key farm inputs (i.e. grain, fodder and fertilisers), GHG emissions from the consumption of electricity and diesel fuel and on-farm methane and nitrous oxide emissions. Total farm GHG emissions were estimated using the Sheep Greenhouse Gas Accounting Framework (Eckard 2008) calculator, based on the National Greenhouse Gas Inventory methodology (DCCEE 2009). The total farm GHG emission was 1,061.0 t CO2e/annum. When segmented into the two lamb enterprises, the enterprise emissions were 629.3 and 431.7 t CO2e/annum for the home-bred and purchased lamb enterprises, respectively. This equated to a GHG emissions intensity of lamb production of 18.2 and 11.5 kg CO2e/kg dressed weight for the home-bred and purchased lamb enterprises, respectively. Several abatement strategies were explored for the home-bred lamb enterprise focusing on management and/or genetic improvements. Joining maiden ewes at 7 months of age compared to 19 months of age, a practice already adopted by this farmer and therefore estimated in reverse by including an additional year of unjoined maiden ewes to the current farm enterprise, reduced the GHG emissions intensity of meat production from 20.4 kg CO2e/kg meat to 18.2 kg CO2e/kg meat; equivalent to a 10.7% decline. Increasing lamb weaning rates by an absolute of 10%, combined with reducing ewe numbers by 106, to maintain the same number of weaned lambs, reduced the GHG emissions intensity of meat production from 18.2 to 16.9 kg CO2e/kg meat; equivalent to a 12.7% decline. Reducing the annual crude protein concentration of the weaned lamb diet from 24% to 14% reduced GHG emissions intensity from 18.2 to 17.6 kg CO2e/kg meat; equivalent to a 3.2% decline. This analysis used an inventory approach to estimate GHG emissions, as opposed to a dynamic biophysical approach, and therefore fails to capture the dynamic interactions between emission sources, climate, soil and management practices. This study also did not explore the financial implications of adopting the various abatement strategies explored. For example, reducing the excess crude protein from the weaned lamb diet resulted in a reduction in nitrous oxide emissions. A proportion of the lambs’ diet consisted of grazing lucerne so replacing this forage with another forage source of lower crude protein concentration would reduce nitrous oxide emissions. However, this strategy could also result in a lower digestibility diet, thus reducing lamb daily intakes. The net result of reducing nitrous oxide emissions could be an increase in enteric methane emissions as lambs would require more time to reach target weights for slaughter. Therefore whole-farm analysis of abatement strategy options needs to consider biophysical and economic analyses, not just inventory analysis, to examine which strategies will result in win-win outcomes for both farmers and the environment. This study was supported by funding from the Australian Department of Agriculture, Fisheries and Forestry under its Australia’s Farming Future Climate Change Research Program, Meat & Livestock Australia and the Tasmanian Institute of Agriculture. Alcock DJ, Hegarty RS (2011) Potential effects of animal management and genetic improvement on enteric methane emissions, emissions intensity and productivity of sheep enterprises at Cowra, Australia. Animal Feed Science and Technology 166-167, 749-760. DCCEE (2009) National Inventory Report 2009, Volume 1: The Australian Government Submission to the UN Framework Convention on Climate Change, April 2011. (Department of Climate Change and Energy Efficiency: Canberra, Australia); http://www.climatechange.gov.au/en/publications/greenhouse-acctg/national-inventory-report-2009.aspx Eckard RJ (2008) Sheep Greenhouse Accounting Framework Calculator (University of Melbourne: Melbourne, Victoria); http://www.greenhouse.unimelb.edu.au/Tools.htm Howden SM, White DH, Bowman PJ (1996) Managing sheep grazing systems in southern Australia to minimise greenhouse gas emission: adaptation of an existing simulation model. Ecological Modelling 86, 201-206. Peters GM, Rowley HV, Wiedemann S, Tucker R, Short MD, Schulz M (2010) Red meat production in Australia: Life cycle assessment and comparison with overseas studies. Environmental Science and Technology 44, 1327-1332.