Valorization of aqueous waste streams from thermochemical biorefineries

Thermochemical conversion of lignocellulosic biomass is a promising route to produce fuels and oxygenated chemicals and could enable circular carbon utilization. In most thermochemical conversion processes, however, some chemical co-products are lost in aqueous waste streams that are both dilute and heterogeneous. Cost-competitive isolation of these chemical co-products is challenging due to the high-purity requirements typically necessary for bulk chemical production. Here, we demonstrate the production and isolation of two biomass-derived monomers, phenol and catechol, from a comprehensively characterized aqueous waste stream generated via catalytic fast pyrolysis. Specifically, we separate phenol and catechol to 97 wt% purity using the industrially relevant processes of liquid–liquid extraction, distillation, and recrystallization. Techno-economic analysis predicts that a mixed phenolics stream can be produced from the waste stream at a minimum selling price of $1.06 kg−1. Overall, this work demonstrates an approach to high-purity oxygenated aromatic compounds that is potentially economically feasible and technically achievable which increases the atom efficiency of thermochemical conversion through waste stream valorization.