Trajectory-based evaluation of greenhouse gas mitigation pathways in municipal solid waste systems: a system dynamics approach

Abstract

Municipal solid waste (MSW) management is a critical component of greenhouse gas (GHG) mitigation in landfill-dominated systems, where methane emissions are governed by cumulative waste deposition and delayed decomposition processes. Conventional assessments often emphasize end-state comparisons, which can obscure the long-term consequences of intervention timing, stock accumulation, and demand-driven non-linear dynamics. This study applies a system dynamics (SD) modeling framework to evaluate trajectory-based GHG mitigation pathways in Thailand’s national MSW system over a multi-decadal horizon (2024-2050), with explicit consideration of methane legacy effects and tourism-driven variability in waste generation. The model represents MSW generation, waste routing, landfill stock accumulation, and delayed methane emissions using first-order decay logic. Tourism activity is incorporated as a time-varying external driver affecting waste generation flows, allowing demand fluctuations and non-linear responses to emerge without altering the underlying system structure. Four scenarios are analyzed to reflect alternative intervention timings and waste management pathways under a consistent modeling framework. Simulation results show that early intervention fundamentally reshapes emission trajectories by constraining landfill stock accumulation and limiting future methane generation. In contrast, delayed interventions—despite achieving similar diversion levels at later stages—retain substantially higher cumulative GHG emissions due to legacy effects embedded in previously accumulated waste. Tourism-driven increases in waste generation act as a stress amplifier, accelerating stock formation and magnifying emissions under landfill-dominant configurations, leading to disproportionate GHG responses relative to demand growth. Overall, the findings demonstrate that the performance of GHG mitigation in MSW systems is strongly shaped by path dependence, time delays, and non-linear demand dynamics. Trajectory-based analysis provides essential insight into why late-stage mitigation cannot fully reverse methane legacy effects, underscoring the importance of early structural change for achieving sustained emission reduction in landfill-dominated waste management systems.