Review of environmental performance of sheep farming using life cycle assessment

Life cycle assessment (LCA) is increasingly being used as a tool to estimate environmental impacts in the sheep sector. Policymakers have been keener on developing policies and recommending best management practices from a life cycle perspective. This paper reviews the key LCA studies of the sheep sector within the last fifteen years to assess the state of the art of the environmental impacts of the sheep supply chain. Peer-reviewed LCAs as well as global, organizational efforts on the subject have also been reviewed and discussed. Discussions are categorized by products, hotspots, methodologies and system boundaries, and impacts of interest. The vast majority of studies have utilized a "cradle-to-farmgate" system boundary, where impacts associated with production of major farm inputs, management/applications of inputs and direct emissions from livestock are included. The sole focus of the majority of studies in terms of the category of impact has been climate change, quantified through greenhouse gas (GHG) emissions. The impact results are difficult to generalize due to wide discrepancies in farming practices, production efficiencies, product allocation and emission modeling methods. The GHG emissions, however, associated with sheep meat, milk and wool fall in the range of 3.5-25 kg CO2-eq/kg live weight, 2-5 kg CO2-eq/kg fat and protein corrected milk (FPCM), and 20-60 kg CO2-eq/kg greasy wool, respectively. The overwhelming consensus is that the single largest contributor to GHG emissions is direct methanic emission from livestock, generally contributing to 50%-75% of overall GHG emissions. More research needs to be conducted on determining impacts of "post-farm" activities such as processing of sheep products before it reaches the consumers, inclusion of the benefits of carbon sequestration, and consideration of environmental impacts other than climate change. (C) 2021 Elsevier Ltd. All rights reserved.