The UNIQUE project aims at integrating the fluidized bed steam gasification of biomass and the hot gas cleaning and conditioning system into one reactor vessel. This paper outlines thermodynamic calculations and lab-scale experimental investigations on alkali removal and sour gas control. The results show that the alkali concentration in gasifier derived gases can be limited to values below 100 ppbv using aluminosilicates. The H2S concentration can be limited to values above 100 ppmv using conventional Ca or Cu based sorbents and to values below 1 ppmv by a new Ba containing sorbent developed by Forschungszentrum julich. In addition, the Ba containing sorbent can also limit the HCl concentration to values below 1 ppmv. (C) 2011 Elsevier Ltd. All rights reserved.