Evaluation of urban wastes as promising co-fuels for energy production – A TG/MS study

• Combustion characteristics of lignite/urban waste blends were evaluated.
• Waste paper was the most reactive among the species studied.
• Emissions of CxHy, CO, SO2 from blends decreased as compared to lignite combustion.
• Sewage sludge increased CxHy and NOx released from the mixtures.
• Combustion characteristics of mixtures showed synergy between component fuels.

This work aimed at investigating the potential of using urban wastes and lignite mixtures for energy generation. The objective was to determine the combustion characteristics and the gaseous pollutants of indigenous lignite/urban waste (MSW, RDF, waste paper, sewage sludge, demolition wood) blends, as well as to evaluate the compatibility of each component in the blend. The experiments were conducted in a thermogravimetric analysis system, at non-isothermal heating conditions, over the temperature range 25–900 °C. Combustion gases and emissions of SO2, NOx and hydrocarbons were continuously monitored through a quadrupole mass spectrometer coupled to the thermobalance system. The results showed that the ignition behaviour of the fuels was determined by the amount of volatiles, the H/C ratio, the content of impurities in the samples and in the case of mixtures the blending ratio. Waste paper was the most reactive among the species studied. Emissions of hydrocarbons, CO and SO2 from blends decreased as compared to lignite combustion only, whereas those of NOx remained unchanged. However, sewage sludge increased CxHy and NOx released from the mixtures. Lignite and biomass fuels showed synergy when blended. Co-firing urban wastes with lignite allows for energy recovery, economic benefits and some advantages in terms of thermal reactivity and toxic emissions.