Hydrothermal Carbonization of Autoclaved Municipal Solid Waste Pulp and Anaerobically Treated Pulp Digestate

In this study, the autoclaved organic fraction of municipal solid waste pulp (OFMSW) and the digestate from OFMSW pulp after anaerobic digestion (AD) were processed by hydrothermal carbonization (HTC) at 200, 250, and 300 degrees C for 30 min and 2 h. The focus of this work was to evaluate the potential for producing an energy-dense solid hydrochar from either OFMSW or digestate by HTC. The fate of inorganics, especially the heavy metals in hydrochar is discussed. In addition, the aqueous products were analyzed to identify the chemicals produced and the chemical changes during HTC. A carbon balance was performed from the solid and liquid phase analyses. Moreover, two conceptual MSW treatments consisting of autoclaving with or without AD, but including HTC, were proposed and mass and energy balances were performed. From the proximate, ultimate, FTIR, and fiber analyses, the hydrochar becomes increasingly energy and inorganic dense with the increase of HTC temperature.