A method for reducing pollutant emissions uses a two-stage primary combustion process for a solid-containing fuel including a primary furnace having a combustion chamber, a solid fuel burnout zone and a primary flue-gas post combustion chamber, and a separate secondary combustion train. The fuel is burned in the primary combustion chamber while supplying primary gas in a substoichiometric amount so as to form high heating-value gas and low-carbon solid residue. A partial stream of this gas is diverted and the remainder is passed to the post-combustion chamber. The diverted stream is passed to the secondary combustion train, which includes a conditioner, a secondary combustion chamber and an energy recovery device. Energy-spent exhaust gas from the train is recirculated to the furnace upstream of the post-combustion chamber in which it is burned with the remainder of the high heating value gas and an oxygen-containing gas supplied in superstoichiometric amounts.