Sewage sludge is a problematic by-product of wastewater treatment plants because of its large volume, high moisture content, and unpleasant odour. Thermal processes are effective in their utilization, but they are extremely expensive because they require pre-drying of feedstock. Therefore, the application of an effective pretreatment method is necessary. Hydrothermal carbonization is an adequate process because it takes place in an aqueous environment, improves dewaterability of sewage sludge and creates a solid product, hydrochar, which can be used in energy applications. In particular, the hydrothermal carbonization of sewage sludge was investigated to enhance the hydrochar properties and improve the dewaterability of the process. The reaction parameters, 200 °C and 2 hours, were fixed. Filtration tests for the resulting slurry were performed. The ultimate and proximate analyses supported by the calorific value of hydrochar were conducted. The experimental results of the hydrothermal carbonization of sewage sludge were used to make a preliminary hypothetical upscale of the process on industrial scale, in order to perform a preliminary energy balance, which will be used to supply inventory data for the following Life Cycle Assessment, to provide an evaluation of the environmental feasibility of the process.