Lignocellulose, a green carbon source, can replace fossil fuels. This study presents a Ru/Mg(OH)₂ catalyst for self-supplied hydrogen reductive catalytic fractionation (SCF) of lignocellulose, achieving 50.7 wt% yield of lignin-derived monomers with water as solvent. Model studies elucidate the lignin depolymerization pathway, advancing sustainable biorefinery technologies.