Sustainable conversion of biomass wastes via hydrothermal processes: fundamentals and technology

In a worldwide context where the community has to make giant leaps forward to contain the catastrophic consequences of climate change, we need to face the discordant “How do we power our economies?” with green and circular solutions instead of hiding behind the hypocrisy of fossil fuels. Biomass, renewable, abundant, and cheap, can trigger a shift towards a zero-carbon emission economy, in which it substitutes fossil fuels for the production of energy and materials. Among the strategies to valorize biomass, hydrothermal processes are green pathways for producing biofuels and bio-based materials. However, research has yet to fill several gaps to make these processes ready for industrial scaling and spreading. Therefore, along with this Ph.D. thesis, we provide new insights into hydrothermal processes, touching several scientific areas: from in-depth research around the thermochemical fundamentals to the engineering of new sustainable and biorefinery concepts. Through fundamental research, we try to answer “What’s happening during hydrothermal processes?” facing the enormous complexity of the process by investigating chemical pathways, kinetics, and thermodynamics. Facing sustainability, we explored the coupling of hydrothermal conversion with concentrated solar energy to develop a zero-energy process and the integration of hydrothermal carbonization with subsequent treatments to valorize by-products.