The aim of this study was to determine the methane (CH₄) generation factor (k) and CH₄ generation potential (L) for bulk waste in order to calibrate a CH₄ generation model (USEPA Landgem 3.02) and provide information on the remaining CH₄ generation potential in a large (54 ha) municipal solid waste landfill located in a boreal climate. The CH₄ generation model was calibrated by actual CH₄ recovery and emission measurement data. Moreover, waste characterisation information from a previous study was considered. The appropriate k for bulk waste was 0.18 in the studied landfill, which indicated a higher rate of degradation than proposed by the Intergovernmental Panel on Climate Change as a default k value of 0.09 for wet conditions in boreal and temperate climes, whereas the calibrated L of 100 m³/t was lower than estimated on the basis of a previous waste characterisation study. The results demonstrate the importance of model calibration, as inappropriate model parameters may result in a large discrepancy (approximately 100 % or 119 million m³ having an energy equivalent of nearly 1.2 TWh) in cumulative CH₄ generation estimates within a 18-year timescale (2012–30) at the studied landfill.