Effect of liquid hot water pre-treatment on sugarcane press mud methane yield

•Improved biomethanation by LHW pre-treatment compared with untreated press mud.•A 33% COD solubilisation resulted in the best methane yield (>55% increase).•Increase of methane yield by a maximum of 63% at 150°C for 20min.•Highest furfural concentration of 1214.17mgL−1 was found at 200°C for 5min.•HAc release was influenced more by temperature than by pre-treatment severity. Sugarcane press mud was pretreated by liquid hot water (LHW) at different temperatures (140–210°C) and pre-treatment times (5–20min) in order to assess the effects on the chemical oxygen demand (COD) solubilisation, inhibitors formation and methane yield. The experimental results showed that a high degree of biomass solubilisation was possible using LHW. Higher methane yields were obtained at lower severities (log(Ro)=2.17–2.77) with (i) mild temperatures (140–150°C) and long contact times (12.5min, 20min) or (ii) mild temperatures (175°C) with short contact time (2min). The highest increase in methane yield (up to 63%) compared to the untreated press mud was found at 150°C for 20min. At temperatures of 200°C and 210°C, low methane efficiency was attributed to the possible formation of refractory compounds through the Maillard reaction.