Biomass gasification is more suitable than combustion for Combined Heat and Power (CHP) applications. In this field, fluidized bed reactor technology ensures good mixing of continuously fed fuel and provides homogeneous temperature distribution in the reactor. The aim of the gasification is to produce clean syngas, thus it is important to investigate the influence of various operating conditions on the property of gas products and tar evolution. Usually, temperature and catalytic bed composition are the most studied parameters. In spite of the advantages of fluidized beds, biomass gasification suffers from technical problems such as slagging and fouling due to the high ash content and the formation of low melting point compounds and eutectic composition. The understanding of bed agglomeration requires the investigation of natural phases of biomass mineral matter and bed material. Due to the abundance of ash in biomass and its low degree of crystallization, supplementary methods have to be used beside XRD, LA-ICP-MS and SEM-EDX analysis to characterise interactions between ashes and fluidized bed material. (C) 2012 Elsevier B.V. All rights reserved.