Life Cycle Assessment of Conventional and Organic Rice Production Under Alternative Irrigation Management in Thailand

This study evaluates the environmental sustainability of conventional and organic rice production systems in Nakorn Nayok province, Thailand, focusing on the Khao Dawk Mali 105 variety. Limited studies have evaluated comparative production systems, alternative water management scenarios, and uncertainty in rice life cycle assessment (LCA) under tropical smallholder conditions. A cradle-to-farm gate LCA was conducted under water-sowing continuous flooding (WSF), with 1 kg paddy rice as the functional unit and the ReCiPe 2016 midpoint (H) method. The results showed that organic systems under flooding exhibit higher global warming potential (GWP) than conventional systems, primarily due to methane emissions, which contributed over 83% of the total GWP. The relatively high GWP values compared with previous studies are associated with continuous flooding conditions, methodological assumptions based on IPCC default emission factors, and lower yield in the studied systems. Uncertainty analysis suggests that organic WSF had higher environmental impacts in 8 out of 18 midpoint categories, while sensitivity analysis highlights the importance of water management. Alternative practices, including dry-sowing delayed flooding (DSF) and saturated soil (ST), can reduce the GWP by 39–57% and water consumption by 8–18%, highlighting the importance of water management as an effective strategy for improving environmental sustainability in rice production systems. Sensitivity and multivariate analyses suggest that resource use and water management are key drivers of environmental impacts. Overall, the findings demonstrate that water management and yield are key factors influencing environmental performance in rice production systems and provide insight for improving sustainability under tropical agricultural conditions.