Synthesis gas production by steam-gasification of carbonaceous waste materials with high volatile contents ( e. g., sewage and industrial sludge, fluff, and scrap tire powder) is kinetically examined. A multiple pseudo-component first-order reaction model is formulated to describe the rates of the combined pyrolysis and gasification processes. Arrhenius-type kinetic parameters are determined by dynamic thermogravimetric experimental runs conducted in the temperature range 473-1476 K. (C) 2009 Elsevier Ltd. All rights reserved.