A landfill located in Ste-Sophie, QC was instrumented with sensors measuring temperature, oxygen concentration, and settlement. A quasi-thermal-mechanical-biological conceptual model was developed and a corresponding numerical model was set-up in COMSOL Multiphysics to simulate the temperatures within the vertical waste profile. Thermal conductivity was varied with depth and time in the waste profile. An aerobic heat generation model was proposed that related the aerobic heat generation rate to the oxygen concentration measured near the surface. An anaerobic heat generation model presented in the literature was included in the model. The heat generation rate was dependent on waste temperature and the total energy expended. Corresponding field data were collected and the simulated temperatures were in good agreement with measured field temperatures. A heat budget was computed showing that aerobic and anaerobic heat generation accounted for 36% and 64% of total heat generation, respectively, during the filling stages of landfill operation.