Life cycle assessment of the Mekong Delta rice supply chain: emission inventory and mitigation pathways toward food security synergies

Despite growing pressure to mitigate greenhouse gas emissions in rice systems, supply chain assessments jointly addressing mitigation and food availability trade-offs within an explicit national policy framework remain limited. Vietnam's Mekong Delta, supplying approximately 10% of global rice trade while accounting for 48% of national agricultural emissions, represents a critical case study for evidence-based mitigation. We conducted an LCA drawing on 11 focus groups with rice farmers and 478 farmer and post-harvest stakeholder interviews to quantify cradle-to-market carbon intensities and evaluate mitigation scenarios and food security trade-offs under a cradle-to-dryer-gate boundary. Cradle-to-market carbon intensities were 2.96 and 2.93 kg CO 2 -eq kg −1 for market-ready milled rice in the domestic and export channels, respectively, with over 97% of emissions concentrated in cultivation, dominated by methane from flooded fields and anaerobic straw decomposition, the two highest-sensitivity parameters. We established a Business-as-Usual baseline (1.84 kg CO 2 -eq kg −1 dried paddy; 46.52 Mt CO 2 -eq yr −1 ) to enable scenario-based analysis across six intervention levers through single-lever, trade-off, and policy-aligned scenarios. Deep alternate wetting and drying and intensified straw removal achieved single-lever reductions of 14-26%. Trade-off analysis revealed two mitigation pathways: structural interventions, such as land transformation, achieved larger reductions but cut milled rice output by up to 18%, while efficiency-based interventions (food loss reduction, silo drying) reduced emissions while improving food availability. The integrated MI3 achieved a 31% reduction in total GHG emissions alongside a 1.75% increase in milled rice output, surpassing current policy targets and suggesting that ambitious mitigation need not reduce food availability under the modelled conditions. These findings demonstrate that mitigation and food security can be mutually reinforcing, offering actionable pathways for Vietnam's One Million Low-Emission Hectare Initiative and Nationally Determined Contributions.