Toward Energy-Efficient Circular Economy Systems: Process Integration and Industrial Symbiosis in the Agri-Food Sector

The transition towards circular production systems requires integrated methodologies capable of combining heterogeneous recovery technologies while providing consistent criteria for process evaluation and industrial implementation. This work presents a methodology, combining direct experimental measurement at laboratory and pilot scale with engineering-based estimation and industrial-scale projection, for the design and assessment of integrated circular valorisation processes, exploiting industrial symbiosis between agri-food residues and multilayer plastic waste streams. The proposed framework encompasses target product identification, recovery process definition, integration into representative case studies, experimental evaluation, mass and energy assessment, Key Performance Indicator (KPI) generation, and engineering-based industrial scale-up. Seven representative case studies were developed within the Agro2Circular project, covering the recovery of high-value bio-based products from agri-food residues and the recycling and biotransformation of multilayer plastic waste. Experimental data from laboratory- and pilot-scale prototypes were used to quantify material throughput, resource consumption, and process performance and to derive harmonised, industrially projected KPIs. The results show that mechanical and separation-based operations achieve substantial energy reductions upon scale-up, whereas biochemical and thermal conversion routes—particularly enzymatic depolymerisation and fermentation-based processes—remain the dominant energy contributors even under industrial conditions, indicating that process intensification, rather than scale alone, is required to close this gap. Beyond the specific case studies analysed, the framework constitutes a transferable methodology for the development, evaluation and scale-up of future circular valorisation platforms involving multiple waste streams and complementary recovery technologies.