The waste tail gas fuel emitted from refinery plant in Taiwan e.g. catalytic reforming unit, catalytic cracking unit and residue desulfurization unit, was recovered and reused as a replacement fuel. in this study, it was slowly added to the fuel stream of a heater furnace to replace natural gas for powering a full-scale distillation process. The waste tail gas fuel contained on average 60 mol% of hydrogen. on-site experimental results show that both the flame length and orange-yellowish brightness decrease with increasing proportion of waste gas fuel in the original natural gas fuel. Moreover, the adiabatic flame temperature increases as the content of waste gas fuel is increased in the fuel mixture since waste gas fuel has a higher adiabatic flame temperature than that of natural gas. The complete replacement of natural gas by waste gas fuel for a heater furnace operating at 70% loading (i.e. 3.6 x 10(7) kcal/h of combustion capacity) will save 5.8 x 10(6) m(3) of natural gas consumption, and 3.5 x 10(4) tons (or 53.4%) of CO(2) emission annually. Recovering and reusing the waste tail gas fuel as natural gas replacement will achieve tremendous savings of natural gas usage and effectively lower the emission of carbon dioxide. (c) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.