Eco-physiological parameters to include anecic earthworms’ activity in soil organic matter (SOM) modelling is described. Mineralization in freshly excreted casts is a key process for C and N dynamics and critical for formation of stable SOM. An anecic earthworm module was developed for integration with the Romul_Hum model. The module can be used as a template for epigeic and endogeic earthworms and other litter transforming macro-fauna.