Life Cycle Assessment consequenziale di una bioraffineria integrata: Oltre il processo Kraft

The valorization of renewable resources such as lignocellulosic biomass is of central importance in addressing contemporary environmental challenges, including climate change, land use, water scarcity, and fossil resource depletion. This thesis investigates the environmental advantages associated with the integrated valorization of lignocellulosic biomass within a pre-hydrolysis kraft (PHK) pulping plant. A biorefinery scenario is developed in which hemicellulose and kraft lignin, residual streams otherwise incinerated for energy recovery, are converted into high-value bio-based products, including a novel bio-based adhesive synthesised at laboratory scale, surplus tetrahydrofuran (THF) and, in lower amount, bio-oil, and char. The environmental profile of the integrated biorefinery scenario is quantified and compared against a conventional PHK pulping reference scenario through a comparative consequential life cycle assessment (LCA), conducted in accordance with ISO 14040/14044, an internationally recognized standard methodology for the quantification of the environmental impacts across the full life cycle of a product system.. The functional unit common to both scenarios is 1 kg of unbleached dissolving-grade pulp, used in the manufacture of textile fibers and cellulose derivatives, produced from hardwood via the PHK process. Environmental profile results are discussed across the six impact categories with the highest weighting in the PEF (Product Environmental Footprint) methodology: climate change (kg CO₂ eq.), particulate matter formation (disease inc.), land use (Pt), water use (m³ world eq.), resource use - fossils (MJ), and resource use - minerals and metals (kg Sb eq.). The integrated biorefinery scenario achieves a net environmental benefit across the majority of impact categories, most notably for climate change, shifting from +1.012 to −0.143 kg CO₂ eq. per functional unit, and fossil resource use from +6.268 to −18.91, driven by the substitution of fossil-derived polyurethane and tetrahydrofuran (THF) through system expansion. Land use represents the primary environmental trade-off of the integrated scenario, reflecting the greater biomass demand associated with the valorization processes. A contribution analysis was performed, which provides insights into the contribution of each analysis group in the product system for each impact category, demonstrating that the burdens introduced by the valorization processes are more than offset by the substitution credits attributable to the displaced fossil products, a result that is intrinsic to the consequential modelling framework adopted. A sensitivity analysis on the electricity emission factor and cogeneration efficiency confirms that the climate change advantage of the integrated biorefinery is maintained across all realistic energy contexts, with the exception of highly fossil-intensive grids combined with low cogeneration efficiency. A sensitivity analysis on the life cycle impact assessment (LCIA) method, comparing EF 3.1 with ReCiPe 2016 (H), confirms the robustness of the main conclusions across both methods.