Natural wastes allows for the management of at least two substrates with different properties. In this case, the enhancement of biogas production for the treatment of a mixture of two-stage olive-factory waste (2POMW) and steers excrement (CM) (60:40 w/w) at mesophilic temperature range (35 °C) was the main goal of this work. It was investigated how the appearance and potency of the assimilation interaction were affected by water powered maintenance time (HRT). A decreasing sequence of HRTs between 40 and 12 days was studied. The associated natural stacking rates (OLR) ranged from 2.06 to 6.07 gVS/LR•d. The reactor’s pseudo-consistent state activity was planned for HRTs between 40 and 15 days. The highest methane efficiency gains (0.94 LCH4/LR•d) and explicit methane yield gains (0.52 LCH4/gVSremoved) for 15 days HRT were obtained when absolute acridity (measured as acidic corrosive) in the profluent was 150 mg/L, confirming process solidity. Anaerobic co-absorption of 2POMW and CM because the end of this time saw a clear increase in unexpected unsaturated fats, which led to process instability and a decrease in biogas production.