Comparative Life Cycle Assessment (Gate-to-Gate) of Flood and Drip Irrigation for Wheat Production: A Case Study in the Central Mashhad Plain, Iran

This study presents a life cycle assessment (LCA) of drip and flood irrigation systems for wheat production in the semi-arid Central Mashhad Plain, northeastern Iran, following the ISO 14040/14044 framework. The functional unit is defined as 1 ton of wheat grain at the farm gate. Environmental impacts were assessed using the ReCiPe 2016 Midpoint (H) method. Inventory data were sourced from field surveys, the Ecoinvent database, and regional statistics. The results indicate that while drip irrigation reduces water consumption by approximately 35.3% compared with flood irrigation, it is associated with higher environmental burdens in a range of impact categories, notably marine ecotoxicity (+62%), freshwater ecotoxicity (+58%), freshwater eutrophication (+42%), fossil resource scarcity (+41%), human non-carcinogenic toxicity (+38%), and global warming potential (+19%), along with substantial increases in mineral resource scarcity, human carcinogenic toxicity, and terrestrial ecotoxicity. These trade-offs are mainly linked to the material and energy demands of the pressurized irrigation infrastructure (pipes, pumps, and filters). Sensitivity and uncertainty analyses confirm the robustness of the comparative rankings. However, the analysis is limited by the gate-to-gate system boundary and the use of background databases that may not fully reflect region-specific emission factors. These findings highlight the importance of integrated irrigation policies that address both water conservation and the broader environmental implications of irrigation modernization in semi-arid, groundwater-dependent regions.