The combination of biomass pyrolysis with heat recovery from molten slag is a feasible and economically applicable technology. The thermal behavior and kinetic analysis on cellulose (CE) with furnace slag under a fast heating rate were investigated. An iso-conventional method was used to obtained kinetic parameters for primary gaseous product formation. A positive synergistic effect was observed from the formation of gaseous products, with the reduction of the CO2 content to the lowest value of 16.71 vol %. The lower heating value of the gaseous products reached the lowest value of 7.9 MJ m(-3) at 30% mass ratio of slag. The activation energy of CO2, CO, CH4, and H-2 from CE was 40.49, 31.83, 78.67, and 21.82 kJ mol(-1). The samples with 30% mass ratio of slag presented the lowest activation energy for CO2 with 12.32 kJ mol(-1) and the highest activation energy for CO with 29.35 kJ mol(-1). The addition of furnace slag reduced the activation energy required for CO2, CO, and CH4, especially for CH4.