[en] Highlights: • An innovative method of gasification with use of flue gas was investigated. • Gasification temperature ranging from 350 °C was considered. • Discussed gasification unit is connected to a power boiler. • Syngas with combustible components is recirculated to the boiler. • Wide range of biomass and waste fuels can be used as a feedstock. - Abstract: The paper presents results of the investigation of an innovative biomass and alternative fuel low-temperature gasification method before co-firing in industrial or power plant boilers. Before running industrial-size installation, laboratory tests were carried out to determine usability of alternative fuels to low-temperature gasification process. Tests were conducted in a laboratory reactor designed and constructed specifically for this purpose. The experimental stand enables recording of the weight loss of a sample and syngas composition. The process occurs for a fuel sample of a constant weight and known granulation and with a flue gas of known composition used as a gasifying agent. The aim of the laboratory research was to determine the usability of selected biomass fuel for indirect co-firing in power boilers and to build a knowledge base for industrial-size process by defining the process kinetics (time for fuel to remain in the reactor), recommended fuel granulation and process temperature. Presented industrial-size gasification unit has been successfully built in Marcel power plant in Radlin town, Poland. It consist an innovative rotary gasification reactor. Gasification process takes place with use of flue gas from coal and coke-oven fired boiler as a gasifying agent with recirculation of resulting gas (syngas) with combustible components: CO, H_2, CH_4. C_nH_m to the boiler’s combustion chamber. The construction of the reactor allows the use of a wide range of fuels (biomass, industrial waste and municipal waste). This paper presents the results of the reactor tests using coniferous wood pellets as a fuel. Presented tests confirmed a possibility of continuous low-temperature gasification in a rotary gasification reactor with combustion of a process’ products in boiler’s combustion chamber.