Synergistic effect of mixing wheat straw and lignite in co-pyrolysis and steam co-gasification.

•Pyrolysis and gasification of mixed wheat straw/lignite were studied at 700–900 °C.•A synergy was observed, which was more significant in gasification than pyrolysis.•H2O vapor has magnified the synergy between biomass and coal.•Excess gas production in co-gasification is linear with temperature above 800 °C.