Agronomic life cycle assessment of guayule (Parthenium argentatum A. Gray) cultivation under irrigated semi-arid Mediterranean conditions using wheat (Triticum aestivum L.) as a local environmental benchmark

Guayule ( Parthenium argentatum A. Gray) is a perennial industrial crop for semi-arid regions due to its capacity to produce natural rubber and co-products under limited water availability. However, the environmental performance of its production stage remains insufficiently characterized under Mediterranean conditions and across its multi-year cultivation cycle. This study applied an attributional life cycle assessment (LCA) to evaluate the environmental impacts and cumulative energy demand (CED) of guayule cultivation using primary, site-specific field data. The system boundaries encompassed production up to the farm gate, with a functional unit of 1 Mg of aboveground dry biomass. The evaluated 12-year cultivation cycle comprised an establishment year without harvest (Year 0), ten production years (Years 1–10), and a production year including crop termination (Year 11), resulting in eleven annual harvests and an annualized biomass yield of 8.5 Mg DM ha⁻¹ year⁻¹ . Environmental burdens were assessed across the cultivation stages and, for contextualization, annualized on an area basis over the cycle using irrigated wheat (Triticum aestivum L.) as a local benchmark, without assuming functional equivalence between the harvested products. Impact assessment included GWP100y, CML-IA environmental impact categories, and CED. Nitrogen fertilization, irrigation, mechanized field operations, and direct field emissions were the main environmental hotspots, while seedling production represented an additional energy demand during crop establishment. Guayule showed lower environmental impacts than the irrigated wheat benchmark. Annualized GWP100y for guayule was 408.5 kg CO₂ eq ha⁻¹ year⁻¹ , whereas the wheat benchmark showed 2411.9 kg CO₂ eq ha⁻¹ year⁻¹ , corresponding to an approximately 83% lower climate-change burden. CED was 9967 and 34,070 MJ ha⁻¹ year⁻¹ for guayule and the wheat benchmark, respectively, corresponding to an approximately 71% lower energy demand for guayule. These results identify nitrogen management, irrigation, and mechanization as opportunities for improving the environmental performance of guayule cultivation under semi-arid Mediterranean conditions.