Life cycle assessment of sheep meat and wool production in Northern California

Abstract

A partial life cycle assessment (LCA) of a sheep production system in California was conducted to better understand the environmental impacts of sheep production in the United States. This cradle-to-farm-gate LCA analyzed emissions from sheep-lamb, stocker, and finishing stages of lamb production within the same market chain. Our objective was to calculate the carbon footprint associated with commercial sheep production in northern California and to compare the impact of allocation methods for 1 kg of live weight lamb (LWT), 1 kg cull adult (LWT), and 1 kg of greasy wool at the farm gate. Primary data was collected from on-farm records wherever possible and secondary data from published literature. Whole-system emissions totaled 474.7 Mt carbon dioxide equivalent (CO₂e), of which 42.2% were from animal emissions, 52.6% from feed production and transport, and 5.2% due to animal transport and on-farm operations. Enteric methane was responsible for 34% of total emissions. The sheep–lamb, backgrounding, and feedlot phases were responsible for 86.1, 4.18, and 9.72%, of overall emissions, respectively. Emissions were allocated 100% to meat or between lamb, wool, and cull adult meat on a mass basis. The production system studied for this analysis focused on producing market lambs, with final live weights of 56.4 kg and carcass yield grade 2. Cull adults averaged 54.4 and 68 kg for ewes and rams, respectively, and whole-farm wool production was 2.05 Mt greasy wool. When all emissions were allocated to lamb production, carbon footprints were 28.6 kg CO₂e/kg LWT. When emissions were allocated on a mass basis between lamb, wool, and cull adult meat, 65, 27, and 8% were allocated to lamb, cull adults, and wool, respectively. Carbon footprints were 19 kg CO₂e/kg lamb, 8.0 kg CO₂e/kg cull adult, and 2.5 CO₂e/kg wool. These values highlight the importance of meat production to Californian sheep producers, compared with wool-focused systems found in Australia and the United Kingdom. Whilst lamb has a higher carbon footprint compared with beef regardless of allocation method, coproduct allocation methods also play a significant role in assigning environmental impacts. This analysis is a first step in assessing the overall impact of small ruminant supply chains in the country and identifying aspects that contribute to environmental impacts of production. The results provide baseline data on emissions from sheep production that may be useful in future efforts by the California lamb industry.