The use of composite fuels using pitcoal and sawdust represents a high perspective. The paper deals with the experimental results focusing on the combustion efficiency of composite fuel briquettes and on the polluting emissions level. A special care is given to the determination of boiler efficiency and to the establishment of exploiting economic conditions, like the supply, cleaning etc. The research of the combustion of pitcoal-wood biomass briquettes is conducted on a 55 kW boiler. A numerical modeling of the combustion processes within the boiler allowed a critical comparison between the experimental and numerical data.