Waste disposal is imposed by the European Union under Treaty of Accession concerning waste management order. One of the waste disposal methods is thermal utilisation. The paper presents an investigation of sewage sludge briquettes used as a fuel in combustion process. The research study was carried out on samples taken from the Municipal Wastewater Treatment Plant in Bochnia. Briquettes with lime were formed. The analysis of the elementary chemical composition of municipal sewage sludge, the composition of the ash and thermogravimetric analysis were carried out. The results indicate that the prepared briquettes had sufficient fuel properties.

The motivation of this work was to define the reburning potential of sewage sludge gasification gas (syngas). Numerical simulation of co-combustion process of syngas in hard coal-fired boiler has been done. All the calculations were performed using the Chemkin program. Plug-Flow Reactor model was used. The calculations were modelled using GRI-Mech 2.11 mechanism. The highest NO conversions are obtained at the temperature of about 1000-1200 K. The highest reduction efficiency was achieved for the molar flow ratio of syngas equal to 15%. The combustion of hard coal with sewage sludge - derived syngas reduces NO emissions and the amount of coal needed to produce electricity and heat. Advanced reburning, which is a more complicated process gives efficiency of up to 80%. The calculations show that the analyzed syngas can yield better results.