Investigation of thermal behaviour and synergistic effect in co-pyrolysis of municipal solid waste and sewage sludge through thermogravimetric analysis

Abstract

Municipal solid waste (MSW) and sewage sludge (SS) co-pyrolysis have the potential to revolutionize waste management and address energy challenges. Consequently, it is crucial to explore the thermal and synergistic effect of MSW, SS and their blends using thermogravimetric analysis. Different blending ratios (MSW90%SS10 %, MSW80%SS20 % and MSW65%SS35 %) were analyzed under an inert nitrogen (N2) gas atmosphere, at various heating rates (10,20 and 30 K min−1), from 30 °C to 900 °C. This paper specifically addressed the effect of heating rate and blending ratio on separate and jointed pyrolysis of the two raw materials. The analysis revealed two significant decomposition stages observed in the individual pyrolytic processes and their blends. Results showed that a higher heating rate slowed down the decomposition rate due to less effective heat transfer. The blending ratio of 35 % SS at 20 K min−1 exhibited a positive synergistic effect while an antagonistic effect was observed in another mixing ratio. Activation energy determined using the Coats-Redfern model in the second stage of active pyrolysis for MSW90%SS10 %, MSW80%SS20 % and MSW65%SS35 % was 41.879, 43.365 and 40.271 kJ mol−1 respectively. The negative ΔS (entropy) and positive ΔH (enthalpy) values indicated a decrease in disorder and an endothermic reaction respectively. This finding was consistent with the formation of complex products from the feedstock and the endothermic nature of the pyrolysis process. Therefore, strategic co-pyrolysis optimization of MSW and SS with the precise blending ratio of 35 % sewage sludge and controlled heating rate of 20 K min−1, exhibits substantial potential for advancing eco-friendly waste management practices while enabling effective energy recuperation.