The kinetic constant K-0, determined under a range of substrate loadings, was used to compare immobilized cell anaerobic digesters treating abattoir and milk bottling waste waters. Two types of mineral support were evaluated, sepiolite and bentonite, and found to influence significantly the process kinetics. Sepiolite promoted the digestion of the milk bottling waste whereas bentonite promoted the digestion of abattoir waste. Possible reasons as to why these effects are observed are proposed based on the composition of the waste water.