A biogenic life cycle approach towards estimating the carbon intensity of wool production: Evidence from six Australian case studies

Life cycle assessments (LCA) of wool typically associate this natural textile fibre with a high greenhouse gas emissions intensity because of enteric emissions. We analysed the application of 14 LCAs published between 2010 and 2024 and found that they focussed exclusively on emissions, disregarding the fact that wool production is embedded in a biogenic system. ISO 14067:2018 recognises biogenic carbon but has not been applied to wool yet. Here we seek to rectify this. This study explores the application of ISO 14067:2018 to six representative Australian wool enterprises, extending the detailed LCA case study data from Wiedemann et al. (2016) to define and map the flows of biogenic carbon ingested by grazing sheep. Thereafter we explore the impact of key aspects of system biogenic function on calculated wool emissions intensity within the sheep production system. Mapping of ingested carbon flows across enterprises showed that the major carbon destinations were manure (54.1 %), followed by respiration (22.7 %), urine (7.5 %), and enteric emissions (5.2 %). Exploration of the emissions intensity of wool production showed that while biogenic model outputs closely correlated with those of Wiedemann et al. (2016) when biogenic carbon was excluded, emissions intensities were reduced by the addition of biogenic functionality, declining by on average 102 % with retention of 66.7 % of manure within the grazing system. We conclude that conducting LCA of biological products without addressing biogenic carbon inflates the emission intensity. For the first time, the on-farm cradle-to-farm gate flow of biogenic carbon of Australian greasy wool production are comprehensively analysed in a manner that conforms with ISO 14067:2018; it has a major impact on wool's carbon footprint. Fig. 5: Consumption of carbon and the allocation and flow thereof through six case studies. Source: Table 1 • Biogenic carbon flows in greasy wool production are mapped in conformance with ISO 14067:2018. • Biogenic carbon emission intensities of six Australian case studies have been calculated. • The results disaggregate fossil and biogenic removals and sources of emissions. • Emissions intensity is shown to be sensitive to manure retention assumptions. • We conclude that LCAs which ignore biogenic carbon overstates wool's emission intensity.