Abstract. Oil palm frond can be used as alternative energy source by torrefaction process. Torrefaction is a treatment process of biomass into solid fuel by heating within temperature range of 200-300°C in an inert environment. This research aims to result solid fuel through torrefaction and to study the effect of process variable interaction. Torrefaction of oil palm frond was using fixed bed horizontal reactor with operation condition of temperature (225-275 °C), time (15-45 minutes) and nitrogen flow rate (50-150 ml/min). Responses resulted were calorific value and proximate (moisture, ash, volatile matter and fixed carbon). Analysis result was processed by using Design Expert v7.0.0. Result obtained for calorific value was 17.700-19.600 kJ/kg and for the proximate were moisture range of 3-4%; ash range of 1.5-4%; volatile matter of 45-55% and fixed carbon of 37-46%. The most affecting factor signficantly towards the responses was temperature then followed by time and nitrogen flow rate.

Palm frond can be converted to solid fuel using torrefaction process as an alternative energy source. Torrefaction is the process to convert the biomass into solid fuel at a temperature range of 200-300oC in inert condition. Calorific value is the most important response in solid fuel. The aim of this research is to obtain the optimum condition of palm fronds torrefaction statistically was used Response Surface Methodology. Torrefaction of palm frond on fixed bed a horizontal reactor which is equipped with horizontal condenser and condensate trap with the condition process such as the temperature (225-275oC), time (15-45 min), and N2 flow rate (50-150 ml/min). This research methodology consist of drying, washing with liquid product of torrefaction, torrefaction, and analysis. The response variables  were mass yield, calorific value, energy yield, and proximate. Design Expert Trial Version 7.0 Software was used for optimization of condition process with desirability. The optimized condition process were temperature of 275oC, time of 44 minute, and N2 flow rate of 50 ml/min.  Keywords: solid fuel, design expert, optimization, palm frond, torrefaction