Simulating temperature-dependent biodegradation-induced settlement at a landfill with waste lifts placed under frozen conditions.

Instrument bundles placed within the Ste. Sophie landfill (Quebec, Canada) have been collecting temperature and settlement data since January 2010. Previous modelling efforts simulated settlement based on a three-component model to account for primary or instantaneous compression, secondary compression or mechanical creep and time-dependent biodegradation-induced settlement. In northern climates where waste may be placed under frozen conditions, a time-dependent biodegradation-induced settlement term is unable to simulate settlement due to biodegradation as waste temperatures transition from below zero to optimal values for anaerobic degradation. This paper presents a temperature-dependent biodegration-induced settlement model. The model simulates heat generation as a function of temperature and tracks the expended energy as the waste degrades. The ratio of the expended energy to the total potential expended energy is used in the proposed temperature-dependent biodegradation-induced settlement term. The new term better accounts for the delayed biodegradation process observed in wastes placed under frozen conditions. The model was able to simulate the settlement trends observed at the Ste. Sophie landfill. The goal of developing and including a temperature-dependent biodegradation-induced settlement term in the model was to study the effects of operating conditions on waste settlement and stabilization. An optimized waste lift placement strategy could enhance waste stabilization and improve the airspace utilization within a landfill, simultaneously bringing increased revenues to landfill operators while decreasing the post closure environmental burden of landfills.