The energy utilization of the alternative fuels is one of the main topics for future developments of recoverable sources in the European Union and in the Czech Republic. The aim of research is combustion tests in the fluidized-bed boiler Foster Wheeler located at Štětí. The experiments are carried out for Czech brown coal, wood, sewage sludge and wastes including analyses and recommendations for optimal thermal utilization and minimizing harmful emissions. The second step is thermal analyses of coal, alternative fuel- wood pellets and sewage sludge from treatment plant. From the results of experiments and thermal modeling it is clear that 15 % of alternative fuels can be used in the large fluidized-bed boilers located in the Czech Republic., Pavel Kolat, Bohumir Čech, Dagmar Juchelková, Helena Raclavská and Juraj Leško., and Obsahuje bibliografii