Techno-economic and environmental assessment of a sugarcane biorefinery: direct and indirect production pathways of biobased adipic acid

Adipic acid (ADA) is a highly valuable industrial dicarboxylic acid used largely as a precursor of nylon 6,6 production. It is currently synthesized via a petrochemical process that accounts for over 80% of the global industrial N2O emissions. Biobased ADA offers a cleaner alternative but requires technological advancements in microbe and bioprocess performance to be commercially relevant. An in-depth feasibility analysis was conducted to evaluate two biobased pathways for the production of ADA, modeled as integrated sugarcane biorefineries in Aspen Plus (R). The pathways examined were: (1) direct fermentation of sugars to ADA (S1-ADA) and (2) hydrogenation of biobased cis,cis-muconic acid to ADA (S2-ccMA-ADA). The impact of improvements to key bioprocess metrics (product yield, titer, and volumetric productivity) on the minimum selling price and greenhouse gas (GHG) emissions for both pathways was also evaluated in a full-factorial study. S1-ADA demonstrated the highest feasibility potential, achieving minimum selling prices and GHG emissions that were 33.3% and 78.7% lower, respectively, than those of fossil-based production. These results were obtained under conditions of optimal strain performance and bioprocess efficiencies. However, under comparable technological advancements, the best-achievable results for S2-ccMAADA indicated a green premium of 13.4% alongside a 68.4% reduction in emissions compared to the fossil-based product. Consequently, the direct biobased pathway (S1-ADA) shows greater potential to compete with and eventually replace its fossil- based counterpart once optimized. This finding highlights the need to prioritize S1-ADA for further biotechnological development.