Impact of soft hydrothermal pre-treatments on the olive mill solid waste characteristics and its subsequent anaerobic digestion

The aim of this study was to investigate the effect of a soft hydrothermal pre-treatment (SHP) on olive mill solid waste (OMSW) and its subsequent anaerobic digestion (AD). OMSW was pre-treated in an autoclave at temperatures of 121 °C and 133 °C and excess pressures of 1.1 and 2.1 bars, respectively at heating times of 15, 20, and 30 min. The digestibility of pre-treated and untreated OMSW was determined in terms of methane potential through using biochemical methane potentials tests (BMP). Important solubilization of high-valuable compounds such as hydroxytyrosol and 3,4-dihydroxyphenylglycol was observed after pre-treatments. SHP showed a significant reduction in fiber length and width ( p