This paper presents experimental and numerical results on steam gasification of waste tyres in a rotary kiln pilot plant. Both the process performance and the gas features have been evaluated varying the feeding ratio (FR), defined as the steam/tyres mass ratio. First, several experimental tests have been performed. Then, the obtained experimental results have been used to verify the consistency of a numerical model developed with the aid of the commercial code ChemCAD (R). Once done, the effect of increasing the FR on the gas energy content has been evaluated. Numerical results showed that the gas energy content increases as the FR increases as well, achieving a maximum value for FR = 0.33 that produced a gas which composition N(2) free is (H(2) = 52.7%(vol), CO = 18.1%(vol), CO(2) = 7.0%(vol), CH(4) = 22.2%(vol)) in correspondence of which the lower heating value (LHV) is equal to 29.5 MJ kg(gas)(-1). Higher FR values do not produce a further increase of the gas energy content, rather require a greater amount of input energy for heating the steam from the atmospheric to the process temperature. (C) 2010 Elsevier Ltd. All rights reserved.