Abstract
Purpose Methodology of co-product handling is a critical determinant of calculated resource use and environmental emissions per kilogram (kg) product but has not been examined in detail for different sheep production systems. This paper investigates alternative approaches for handling coproduction of wool and live weight (LW, for meat) from dual purpose sheep systems to the farm-gate. Methods Seven methods were applied; three biophysical allocation (BA) methods based on protein requirements and partitioning of digested protein, protein mass allocation (PMA), economic allocation (EA) and two system expansion (SE) methods. Effects on greenhouse gas (GHG) emissions, fossil energy demand and land occupation (classified according to suitability for arable use) were assessed using four contrasting case study (CS) farm systems. A UK upland farm (CS 1) and a New Zealand hill farm (CS 2) were selected to represent systems focused on lamb and coarse-textured wool for interior textiles. Two Australian Merino sheep farms (CS 3, CS 4) were selected to represent systems focused on medium to superfine garment wool, and lamb. Results and discussion Total GHG emissions per kilogram total products (i.e. wool+LW) were similar across CS farms. However, results were highly sensitive to the method of coproduct handling. GHG emissions based on BA of wool protein to wool resulted in 10–12 kg CO2-e/kg wool (across all CS farms), whereas it increased to 24–38 kg CO2-e/kg wool when BA included a proportion of sheep maintenance requirements. Results for allocation% generated using EA varied widely from 4 % (CS 1) to 52 % (CS 4). SE using beef as a substitution for sheep meat gave the lowest, and often negative, GHG emissions from wool production. Different methods were found to re-order the impacts across the four case studies in some instances. A similar overall pattern was observed for the effects of co-product handling method on other impact categories for three of the four farms. Conclusions BA based on protein partitioning between sheep wool and LW is recommended for attributional studies with the PMA method being an easily applied proxy for the more detailed BA methods. Sensitivity analysis using SE is recommended to understand the implications of system change. Sensitivity analysis using SE is recommended to investigate implications of choosing alternative products or systems, and
Highlights
Sheep are an important part of the global agricultural economy due to their multi-functional role in the production of meat, wool, milk and co-products (e.g. skins, tallow, blood andInt J Life Cycle Assess (2015) 20:463–476 renderable products), as well as for their wider range of cultural and ecological benefits (Zygoyiannis 2006)
greenhouse gas (GHG) emissions based on biophysical allocation (BA) of wool protein to wool resulted in 10–12 kg CO2-e/kg wool, whereas it increased to 24–38 kg CO2-e/kg wool when BA included a proportion of sheep maintenance requirements
BA based on protein partitioning between sheep wool and live weight (LW) is recommended for attributional studies with the protein mass allocation (PMA) method being an applied proxy for the more detailed BA methods
Summary
Sheep are an important part of the global agricultural economy due to their multi-functional role in the production of meat, wool, milk and co-products (e.g. skins, tallow, blood andInt J Life Cycle Assess (2015) 20:463–476 renderable products), as well as for their wider range of cultural and ecological benefits (Zygoyiannis 2006). The impacts of the production and consumption of agricultural products are best assessed by accounting for resource use and environmental emissions throughout the full life cycle of a product, and life cycle assessment (LCA) is an important methodology for this (e.g. ISO 2006). This is a relatively new area of research and while some LCA studies have been published for livestock products, almost all have been restricted to GHG emissions assessment and carbon footprinting of products. Two published studies have investigated the LCA of wool, with both examining meat and wool production from single-casestudy farms in Australia (Brock et al 2013; Eady et al 2012)
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