Thermochemical conversion of wet lignocellulosic biomass for energy and products

The aim of this study is to assess the valorization of wet residual biomass into value-added bioproducts by slow pyrolysis, hydrothermal carbonization (HTC) and physical and chemical activation; in particular, char from anaerobic digestion digestate was intended to soil amelioration, while char from lignin-rich residue from lignocellulosic ethanol was activated for the production of activated carbons. This work deals with experimental investigation in the production and characterization of char from the thermochemical conversion of these wet residual biomass. Within the period of the doctorate, a dedicated test bench for hydrothermal conversion experiments and an activation reactor in a specifically adapted ceramic furnace were built for this purpose. The char from slow pyrolysis and hydrothermal carbonization, together with physical and chemical activated carbons and HTC aqueous phase, were comprehensively characterized in laboratory. The first chapter introduces the issues and the opportunities related with wet residual biomass, in particular with anaerobic digestion digestate and lignin-rich residue from lignocellulosic ethanol, and describes the potential applications of char derived from these feedstocks. The second chapter deals with a description of hydrothermal carbonization and slow pyrolysis, together with a comprehensive state of the art of industrial initiatives on these thermochemical conversion processes. The third chapter is related to the design and commissioning of the experimental apparatus, which was used for the hydrothermal carbonization and activation experiments: a micro-reactor test bench (MRTB) and an activation reactor for a tubular ceramic furnace. In the fourth and in the fifth chapters are reported a detailed description of the experimental campaign on anaerobic digestion digestate and lignin-rich residue, respectively. These chapters follow a classic paper structure, with the material and methods and results and discussion sections. The sixth chapter focuses on process integration at industrial/farm scale of the investigated thermochemical processes (slow pyrolysis, hydrothermal carbonization and activation) with the technology that produced the wet residual biomass. A preliminary economic analysis and reactors design section is also reported.