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Safety evaluation of sewage‐sludge‐derived fuels by comparison with other fuels

The utility of sewage sludge as a biomass fuel is taken as a new approach to recycle unwanted wastes as renewable energy and deal with global warming. However, safety caring of this new type of fuel is a premise before it is practically used in boilers. Thermal behaviors of four sludge‐derived fuels which are under development were examined by several calorimeters (such as thermogravimetry/differential thermal analysis, C80 and thermal activity monitor) at temperature ramp and isothermal conditions. Heat generation at relatively low temperatures was observed. The corresponding spontaneous ignition was detected in an adiabatic spontaneous ignition tester at 80∘C in some sludge species. Moreover, a certain amount of gaseous evolution was accompanied when the sludge fuels were stored at room temperature and at 60∘C. Oxidation is mainly responsible for the heat and gas release from the sludge fuels. The hazards of the sewage sludge fuels were also compared with a bituminous coal and a refuse‐derived fuel, which have the main feature of spontaneous ignition. Copyright © 2009 John Wiley & Sons, Ltd.