Integrating Techno-Economic and Environmental Criteria in the Design and Optimization of a Full Utilization Multiproduct Lignocellulosic Biorefinery

Abstract

An insightful methodology employing the Pareto front approach and a mixed indicator (equivalent carbon dioxide saving cost) to assess the trade-offs between economic and environmental objectives is described to design, optimize, and interpret the complex superstructure of 54 multiproduct lignocellulosic biorefineries. Through a Mixed-Integer Nonlinear Programming (MINLP) strategy, full valorization of all three biomass components is demonstrated, comparing eucalyptus residues, wheat straw, and olive pruning residues across different plant sizes (50 and 150 t/h) and product market price scenarios, considering equivalent carbon dioxide saving cost, particularly emphasizing high-value lignin products. Key results indicate that larger plant capacities and favorable prices for products such as vanillin and levulinic acid maximize economic returns, achieving a net present value of 120–130 €/t. Wheat straw demonstrates superior environmental performance, achieving 1,200–1,500 kg CO_2eq savings/t. The evaluation of CO₂ saving costs reveals that smaller biorefinery sizes (approximately 300–400 €/t CO_2eq savings), the production of levulinic acid (around 100–200 €/t CO_2eq), and phenol formaldehyde resins from lignin (approximately 300–400 €/t CO_2eq) yield the most favorable results. However, our analysis suggests that it may be necessary for a significant 10-fold increment of the current carbon taxation levels to make environmentally optimal biorefinery options economically competitive. The criteria analyzed here serve as a practical tool for stakeholders, balancing profitability with sustainability in biorefinery investments.