Long-Term Performance Assessment of Bioreactor Landfills under Varying Placement Conditions and Waste Characteristics Using a CoupledThermo–Hydro–Bio–Mechanical Model

This study employed a recently developed coupled thermo–hydro–bio–mechanical model to evaluate the effects of physical, biochemical, and thermal characteristics of municipal solid waste (MSW) on the long-term performance of both conventional and bioreactor landfills. Specifically, the study assessed the effect of placement conditions [i.e., initial gravimetric moisture content (MC) and the placement dry density (DD)], biochemical conditions [i.e., initial solid degradable fraction (SDF0) and maximum hydrolysis rate], and thermal characteristics (i.e., MSW thermal conductivity and heat capacity) on long-term performance indicators such as waste stabilization, methane (CH4) generation, settlement, and temperatures in conventional and bioreactor landfills. Results show that higher MC and DD at placement enhance degradation rates in conventional landfills, while their effect is less pronounced in bioreactor landfills, primarily because of near-saturated conditions that limit the additional benefits of leachate recirculation. Bioreactor landfills consistently exhibited higher peak temperatures (>60°C) across all scenarios than conventional landfills due to higher heat generation rates. A higher SDF0 extended stabilization periods under conducive moisture conditions, primarily due to increased volatile fatty acid accumulation from cellulose hydrolysis, which inhibited the microbial activity. However, under nonconducive conditions, i.e., low MC, increased SDF0 led to faster stabilization, highlighting the interplay between moisture availability and degradable content. Internal landfill temperatures showed a strong correlation with SDF0, while thermal conductivity and heat capacity significantly influenced degradation by affecting temperature distribution and, subsequently, microbial activity.