A critical review of multiple alternative pathways for the production of a high-value bioproduct from sugarcane mill byproducts: the case of adipic acid

Biobased fuels, chemicals, and materials can replace fossil fuel products and mitigate climate change. Sugarcane mills have the potential to produce a wider range of biobased chemicals in a similar approach to bioethanol production, including adipic acid. Multiple alternative pathways for converting simple sugars into adipic acid have been described, with the potential for integration into a sugar mill. The economics and expected greenhouse gas emissions reductions compared to fossil-based adipic acid were investigated in the present study to identify preferred pathways for implementation in sugarcane biorefineries. Nine biobased pathways for adipic acid production were screened for technical performances, resulting in the selection of four preferred options for rigorous comparison, i.e., direct microbial conversion of sugars, and production via cis,cis-muconic acid, glucaric acid, and glycerol as intermediate, obtained from sugars. The minimum selling prices of adipic acid for an attractive return on investment were determined for these pathways, using either A-molasses or a combination of A-molasses and pretreated sugarcane lignocelluloses in biorefineries designed to be energy-self-sufficient. Adipic acid production from A-molasses via cis,cis-muconic acid was the best overall performing scenario with the lowest minimum selling price of USD 2,538/Mt and lowered greenhouse gas emissions (2,325 g CO2 eq/kg wet) compared to fossil-based adipic acid production. The scenarios with combined A-molasses and lignocellulosic feedstock had increased minimum selling prices by 29 to 101% compared to adipic acid production from A molasses via cis,cis-muconic acid.