Unlocking Agro-residue Potential Via a Multi-product Integrated Biorefinery

The intrinsic valorization of agro-industrial residues through integrated and sustainable strategies is gaining increasing attention due to its potential environmental, energetic, and economic benefits. The present study proposes a circular biorefinery model for the wine sector, aimed at converting grape pomace, wine lees, and pruning residues into biomethane and a crude bio-oil, through a synergistic combination of several processes. Both experimental and modelling results were combined to assess a novel process integration. Grape pomace and wine lees were considered as the substrate for the anaerobic digestion, biomethane was obtained from a pressure sorption adsorption process, while the off gases were used to sustain the energy demand of the digestate (hydrothermal liquefaction). Vine prunings were treated by pyrolysis and used as the adsorbent phase in the pressure sorption adsorption. The results highlight yields to gaseous, liquid, and solid products of approximately 10%, 30%, and 30%wt on dry raw material basis, respectively, demonstrating effective mass partitioning across product streams in the integrated biorefinery process. Through strategic energy integration – leveraging pyro-gas, hydro-gas, and off-gases from biomethane upgrading – the valorization of the residual digestate proved sufficient to sustain the HydroThermal Liquefaction (HTL) processing of approximately 80% of total digestate stream. This synergy not only achieves near-complete waste utilization, but also enhances overall process efficiency, reducing external energy inputs by over 70% while maintaining favourable technical viability.