We have conducted tests by burning coal and waste such as waste plastics and car shredder dust, using a furnace with a circulating fluidized bed. It was studied the effect of mixed combustion on the emission behavior of HCl, SOx, NO_x, N_2O, heavy metals and dioxins. It was found that mixed combustion with coal reduces HCl, SOx and dioxins. Elution tests of the fly ash from the bag house also show the benefit of mixed combustion.