Physic nut waste is selected as the biomass feedstock for fast pyrolysis as it is available in large amounts from biodiesel production in Thailand. The volatile matter and fixed carbon contents are 73.8% and 13.6% while ash contents are 5.8%. Carbon is the main element with 49.03 wt%. The oxygen content of 39.0 wt% is considerably high which could directly convert to the oxygenated pyrolysis liquid products. To decrease oxygenated compounds, HZSM-5 was used as a catalyst to upgrade pyrolytic products from fast pyrolysis using analytical pyrolysis-GC/MS method. The HZSM-5 catalyst was successfully synthesized by hydrothermal method at 160-180 degrees C for 24h. The particle size, surface area, and pore diameter were 11.25-15.52 mu m, 567-582 m(2)/g, and 21.78-26.11 angstrom, respectively. The pyrolysis was performed at 500 degrees C with the Jatropha wastes to catalyst ratio of 1:1-1:10. The presence of HZSM-5 contributed to eliminate the undesirable oxygenated compounds such as acids and ketones which could alleviate problem regarding acidity and instability in bio-oil. In addition, it enhanced significantly the yields of desirable hydrocarbon compounds. The increase in catalyst contents had an effect on the enhancement of hydrocarbons yields, and tended to promote deoxygenation and denitrogenation. At moderate biomass to catalyst ratio (1:5), HZSM-5 synthesized at 170 degrees C contributed to improve the hydrocarbon yields of 95%, including mainly toluene and xylene, which are valuable products because of their high heating value properties. (c) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.