Greenhouse gas mitigation pathways for municipal solid waste management in reorganised Ho Chi Minh City

The 2025 administrative reorganisation of Ho Chi Minh City merged the former city with Binh Duong and Ba Ria-Vung Tau provinces, creating a megacity that generates approximately 14,000 t day⁻¹ of municipal solid waste, most of which is still landfilled. This study evaluates greenhouse gas mitigation pathways for the reorganised city by comparing seven management configurations: the observed current system, a 2026 business-as-usual trajectory, and five progressive diversion scenarios combining composting, recycling, anaerobic digestion, energy recovery and residual landfilling. Direct emissions were derived from the 2006 IPCC Guidelines and their 2019 Refinement, including leachate treatment, and combined with life cycle avoided-emission credits under an explicit system-expansion convention. We tracked process residues to avoid understating effective landfill requirements, propagated parameter uncertainty through 10,000 Monte Carlo iterations across eight variables under both independent and correlated sampling, and examined structural uncertainty in waste composition, biological emission factors, and global warming potentials separately. The observed system emits 602 kg CO₂-eq t⁻¹, equivalent to 3.08 Mt CO₂-eq yr⁻¹, with landfilling contributing approximately 99% of the net burden. Progressive diversion reduces net emissions by 67% to 124% under the optimistic reference case, but under propagated uncertainty only one configuration achieves a negative median balance: the portfolio that couples moderate energy recovery with recycling expanded under the national extended producer responsibility (EPR) framework. That portfolio is also the least expensive of the deep-diversion options, abating approximately 0.20 Mt CO₂-eq yr⁻¹ more than maximum energy recovery while costing about 33 million United States dollars per year less; the final increment to maximum combustion capacity instead costs 171 to 236 dollars per tonne of carbon dioxide equivalent, against 52 to 68 dollars per tonne for the earlier diversion steps. Residue accounting raises the effective landfill requirement for deep-diversion configurations to about 20% to 25% of generated waste. The results indicate that the city should prioritise landfill diversion, source separation and EPR recycling, and size energy recovery capacity to genuinely residual waste rather than maximising combustion.