Modelling of anaerobic digestion processes is a key aspect to study and optimize the digesters and related waste streams. However, some parameters have to be calibrated according to the substrates characteristics for an adequate prediction of the biogas production and effluent characteristics. This article presents a calibration procedure for the IWA Anaerobic Digestion Model n°1 applied to the modelling of a digester treating pig slurry. The most sensitive parameters were selected and calibrated combining the results from a continuous digester and from batch trials run with the sludge sampled from the digester and fed with specific substrates additions.