Abstract: A method and system for increasing the efficiency and environmental compatibility of combustion systems, preferably for heat recovery from a wet flue gas and/or for flue gas purification, especially of flue gas from the combustion of high water-content fuels, such as biomass, especially wood, and for reducing the volumetric flow of the flue gas and/or for recovery of water from the flue gas, wherein the flue gas is brought into contact with a measured quantity of concentrated hygroscopic in at least one absorber unit and the measured quantity of hygroscopic material is diluted and heated with absorption of water from the flue gas. Heated is extracted from the heated and diluted hygroscopic material after which it is concentrated in at least one separating unit by separation of water and the resulting measured quantity of concentrated hygroscopic material obtained is routed at least partially to the absorber unit.