Application of life cycle assessment to sheep production systems: investigating co-production of wool and meat using case studies from major global producers

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 CO 2 -e/kg wool (across all CS farms), whereas it increased to 24-38 kg CO 2 -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 to evaluate system change strategies in which case consequential modelling is appropriate. To avoid risks of burden shifting when allocation methods are applied, results should be presented for both wool and LW.

Assessing the environmental impact of ruminant production systems

“…LCA has been applied to all major ruminant production systems (beef, dairy, lamb and wool), albeit with different degrees of scrutiny into system-wide uncertainties. Frequently cited examples of works on the sheep sector include Biswas et al (2010), Ripoll-Bosch et al (2013) and Wiedemann et al (2015a). For dairy, Üçtuğ (2019) provides an extensive literature review encompassing 31 studies.…”

The need for co-product allocation in the life cycle assessment of agricultural systems—is “biophysical” allocation progress?

“…However, several new allocation methodologies have been proposed for LCA studies of agricultural systems based on physical relationships between co-products. These methodologies are often referred to as Bbiophysical^allocation (International Dairy Federation 2010; Eady et al 2012;Thoma et al 2013;Gac et al 2014;Van Der Werf and Nguyen 2015;Wiedemann et al 2015). Draft guidelines on carbon footprinting in livestock systems issued by the FAO have also recommended that biophysical allocation should be adopted for models of the on-farm stages of livestock production (FAO 2014a;FAO 2014c), although currently not in the feed supply chain (FAO 2014b).…”

Review of Methodological Choices in LCA-Based Textile and Apparel Rating Tools: Key Issues and Recommendations Relating to Assessment of Fabrics Made From Natural Fibre Types

“…This leaves a degree of ambiguity in the Higg MSI and potential inconsistencies in the underlying datasets and results. Having noted this, the review of primary data sources revealed a series of studies that had aims and methods consistent with attributional LCAs i.e., [49][50][51][52] and one study that had aims and methods consistent with consequential LCA [53].…”