Consequential Life Cycle Assessment of a Multi-Product Cascade Biorefinery from Hass Avocado Seeds: Environmental Hotspots, System Expansion, and Uncertainty Analysis

The global avocado industry generates seed waste typically directed to sanitary landfills despite rich starch, phenolic, and fiber content. This study evaluates the environmental sustainability of a multi-product cascade biorefinery through the first consequential life cycle assessment (cLCA) of a system converting Hass avocado seeds into native starch, a biodegradable starch-PLA-fiber biofilm, and a microencapsulated phenolic bioinsecticide, using laboratory-validated inventory data scaled through Aspen Plus V15 simulation. Following ISO 14040/44, the gate-to-gate cLCA applies ReCiPe 2016 Midpoint (H) with ecoinvent 3.11 in openLCA 2.6, resolves multi-functionality through system expansion, and uses 1000 kg seed waste as the functional unit (FU). Under deterministic conditions, the biorefinery exceeds the landfill baseline in all five evaluated midpoint categories: climate change (5215.95 vs. 674.03 kg CO2-eq), land use (275.71 vs. 2.94 m2a crop-eq), fossil energy (2514.56 vs. 6.17 kg oil-eq), water use (8.67 vs. 0.27 m3), and freshwater ecotoxicity (341.35 vs. 279.09 kg 1,4-DCB-eq per FU). Monte Carlo uncertainty propagation shows that this deterministic ranking is robust only for land use. For climate change, fossil energy, water use, and freshwater ecotoxicity, high uncertainty in avoided-product credits prevents a robust burden-increase claim against the landfill baseline. A deterministic credit-dependency test further shows that pesticide substitution is the dominant avoided-product credit for climate change, fossil energy resources, and water use, whereas starch substitution is most relevant for land use. Hotspot analysis identifies energy supply and acetone as dominant climate change drivers, and solid waste management as the principal freshwater ecotoxicity contributor. A combined improvement scenario achieves 63.8% climate change reduction and 43.2% freshwater ecotoxicity reduction, establishing renewable energy integration and solvent substitution as priority interventions for cascade Hass avocado seed biorefineries. The results identify the conditions required to improve the environmental sustainability of Hass avocado seed valorization.