Evolutionary behavior of syngas characteristics evolved during the gasification of cardboard has been examined using a batch reactor with steam as a gasifying agent. Evolutionary behavior of syngas chemical composition, mole fractions of hydrogen, CO and CH(4), as well as H(2)/CO ratio, LHV (kJ/m(3)),hydrogen flow rate, and percentage of combustible fuel in the syngas evolved has been examined at different steam to flow rates with fixed mass of waste cardboard. The effect of steam to carbon ratio as affect by the steam flow rate on overall syngas properties has therefore been examined. A new parameter called coefficient of energy gain (CEG) has been introduced that provides information on the energy gained from the process. This new parameter elaborates the importance of optimizing the sample residence time in the reactor. (C) 2008 Elsevier Ltd. All rights reserved.