The role of solvent soaking and pretreatment temperature in microwave-assisted pyrolysis of waste tea powder: Analysis of products, synergy, pyrolysis index, and reaction mechanism

•The pyrolysis of fresh waste tea powder consumed high microwave energy (3114 kJ)•Torrefaction of waste tea powder enhanced the bio-oil yield (46.4 wt%)•Co-pyrolysis of fresh and torrefied tea waste caused the synergistic interactive effects.•Torrefied waste tea powder soaked in acetone improved the char yield (59.8 wt%)•High pyrolysis index (26.7) was obtained with ethanol solvent-soaked feedstock.