Anaerobic co-digestion (AcoD) allows for underutilised digesters to increase biomethane production. The organic fraction of municipal solid waste (OFMSW), e.g. food waste, is an abundant substrate with high degradability and gas potential. This paper focuses on the implementation of codigestion of mixed sludge from wastewater treatment and OFMSW through batch and continuous labscale experiments, modelling and microbial population analysis. The results show a rapid adaptation of the process and an increase of the biomethane production of 20 to 40% with 50% OFMSW and it has an impact on the microbial community. The methanogenic activity increases and changes towards acetate degradation while the community without co-substrate remains unaffected. The modelling results show that ammonium inhibition increases at elevated organic loads and that intermittent feeding causes fluctuations in digester performance due to varying inhibition. Modelling can be successfully used for designing feed strategies and experimental set-ups for anaerobic co-digestion.