Fabrication and environmental applications of multifunctional mixed metal-biochar composites (MMBC) from red mud and lignin wastes.

•Novel MMBC fabrication from RM and lignin wastes via one-step pyrolysis in N2 atmosphere.•MMBC exhibited hierarchical porous structure, various functional groups, and metallic Fe.•Incorporated RM promoted syngas generation and hydrocarbons decomposition of lignin.•Demonstrated multifunctionality (adsorption, reduction, and catalysis) of MMBC.