Several types of fuel can be burned in a fluidized bed. This paper discusses the impact of low- or medium-volatile fuels (coal) and high-volatile fuels (biomass and waste) on the emissions of NO, N2O and other pollutants. It is found that high- and low-volatile fuels behave in different ways, and measures to reduce emissions from coal combustion are not necessarily effective for high-volatile fuels. This forms a basis for various design options. Copyright (C) 2002 John Wiley Sons, Ltd.