The hydrolytic stage in high solids temperature phased anaerobic digestion improves the downstream methane production rate

•The hydrolytic stage of TPAD systems have been investigated.•Cattle slurry and maize silage were used as substrates.•Various hydrolytic temperature were tested.•Higher hydrolytic performances were obtained at higher temperature.•Downstream methane production rate noticeably increased after 48 h hydrolysis. The role of the hydrolytic stage in high solids temperature phased anaerobic digestion was investigated with a mixture of cattle slurry and maize silage with variable ratios (100, 70 and 30% volatile solids coming from cattle slurry). It was incubated for 48 h at 37, 55, 65 and 72 °C. Soluble chemical oxygen demand and biochemical methane potential were measured at 0, 24 and 48 h. Higher temperatures improved the amount of solubilized COD, which confirmed previously reported results. Nevertheless, solubilization mostly took place during the first 24 h. The rate of methane production in post-hydrolysis BMPs increased after 48 h hydrolysis time, but not after 24 h. The first order kinetic constant rose by 40% on average. No correlation was observed between soluble COD and downstream methane production rate, indicating a possible modification of the physical structure of the particulate solids during the hydrolytic stage.