Solar pyrolysis process offers solution to utilize solar energy for converting biomass energy into solar fuel. A Box-Behnken design of experiments was performed to optimize a solar pyrolysis process for the production of combustible gases from beech wood. Response surface methodology (RSM) was used to study the effects of temperature, heating rate and argon flow rate on products distribution, gas LHV (lower heating value) and gas composition. The operating variables were as follows: temperature (800-2000 degrees C), heating rate (50-450 degrees C/s) and argon flow rate (4-8 NL/min). A second-order regression model was used to predict the responses. The proposed model described well the experimental values. The analysis of variance (ANOVA) was performed with Minitab 17 software and the significant effect of the factors and their interaction effects were tested at 95% confidence interval. The gas LHV was significantly influenced by temperature and heating rate. The maximum gas LHV higher than that of initial beech wood was found as 14,589 kJ/kg under process conditions as: 2000 degrees C temperature, 450 degrees C/s heating rate. The beech wood calorific value is upgraded through solar pyrolysis. (C) 2015 Elsevier Ltd. All rights reserved.