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Focusing on the reuse of the energy and aiming at the thermal and kinetic characterization of sewage sludge and its mixture, with pruning residues (50 mass%), the thermogravimetry was used. The kinetic study was elaborated from the local isoconversional integral method in heating rates 10.0, 20.0 and 30.0°C min-1 at a temperature ranging from 219 to 386°C at nitrogen atmosphere, in a flow of 100 mL min-1. The average activation energy of sewage sludge sample revealed the value of 219 kJ mol-1 and that of the mixture 161 kJ mol-1 , supporting the incorporation of pruning residues in the sewage sludge. During the degradation process, a remarkable increase in activation energy was noticed that ranged from 20 to 70% conversion in the sewage sludge sample, and regarding the mixture, an almost linear behavior was observed during the decomposition reaction. There was no evidence of kinetic compensation effect in the performed studies. The evaluation of the thermal characteristics, as well as the kinetic study of the degradation of sewage sludge and its mixture with pruning residues, can lead to important insights and contribute to a better use of energy regarding the environmental issues.

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A wide variety of organic residues may be used as energy source such as anaerobic sludge from wastewater treatment systems. However, due to inherent differences in composition, the proper characterization of these biomasses is essential to support their reuse through any conversion process. The aim of this study was the employment of thermal analysis techniques (TG/DTG and DTA) to perform the characterization of anaerobic sludges from different wastewater treatment plants (industrial and municipal), which were further applied for biological production of H 2. The different profiles observed through thermal characterization support the application of these residues as inocula, confirming their potential for H 2 production, while demonstrating the main causes for the different yields obtained (mol H 2 mol-1 sucrose): 0.9 from sludge of brewery industry and 2.0 from sludge of municipal wastewater treatment plant, corresponding to the overall yields of 10.8 and 25%, respectively. These results confirm the versatility of thermal analysis techniques for biomass characterization, focused on its application for power generation. It is urgent to adopt more sustainable and cost-effective solutions for their management, considering a large amount of residues daily generated in both treatment processes addressed; therefore, biohydrogen production by anaerobic digestion may be a promising alternative for the reuse of both residues as it promotes their transformation from costly and potentially polluting waste into clean and renewable energy sources. The development of this anaerobic process is even more attractive in countries as Brazil, where the weather conditions are naturally favorable.