Reactive bed materials for the optimisation of the biomass gasification in a fast internally circulating fluidised bed (FICB) reactor system were tested under sulphur-free (S-free) and H2S enriched conditions in a micro-scale fluidised bed reactor. In the experiments, the bed materials (natural olivine, (FexMg1-x)(2)SiO4, perovskite-type oxides, Ba0.3Sr0.7Fe0.9Mn0.1O3-delta and La0.65Sr0.35Cr0.5Mn0.5O3-delta, Gd0.1Ce0.9O2 and a natural calcite, CaCO3) were examined under realistic redox-cycling conditions to study their oxygen capacity and release, their catalytic activity towards toluene reforming as well as their mechanical and chemical stability. It was found that the synthesised materials outperform the natural materials as reactive bed materials for the FICFB process under S-free atmosphere. Gd0.1Ce0.9O2 has better catalytic properties, perovskites show a higher oxygen storage capacity. However, in the presence of H2S, the perovskite loose their oxygen capacity, while calcite can form a sulphide/sulphate cycle which allows for significant oxygen capacity. Additionally, the catalytic activity goes up. Therefore, under real conditions, the two natural materials, calcite and to a lower extent olivine, have clear advantages with respect to price, catalytic activity and oxygen capacity. (c) 2008 Elsevier Ltd. All rights reserved.