Effects of thermo-chemical pre-treatment of grass silage on methane production by anaerobic digestion

► Thermo-chemical pre-treatment enhanced the solubilisation of grass silage. ► Pre-treatment caused the highest reduction of the lignin content, followed by reduction of hemicellulose and cellulose. ► Grass silage pre-treated at NaOH loading rates of 5% and 7.5% had the highest specific CH4 yields. ► Anaerobic digestion of 7.5% NaOH pre-treated GS had the longest lag phase. ► 100 °C and the NaOH loading rate of 5% is a proper GS pre-treatment condition.