The aim of this article is to investigate the effect of the Hydraulic Retention Time (HRT) on the anaerobic CSTR digester performance in term of methane production using modelling combined with a specific characterization of wastes. Hence, a recently developed methodology (“anaerobic respirometry”) has been applied to define input state variable set for the “Anaerobic Digestion Model n°1” (ADM1) adapted to each substrate including also hydrolysis rates. Then, ADM1 was used to simulate CSTRs with different HRT for each substrate. The results obtained for 12 common organic wastes from agro-industries (slaughterhouses and meat industry) are significantly different in function of the considered substrates. As an example, an HRT of 7 days is sufficient to reach 80% of the maximal methane production for bovine blood whereas HRT values of 32 and 78 days are required for waste activated sludge and rumen content, respectively, to reach the same yield. These results highlight the interest in the adaptation of the reactor design according to the composition of the reactor feed.