NREL Recycles Biorefinery Waste Streams to Create High-Value Chemical Products

by Zia Abdullah (U.S. Department of Energy) Thermochemical conversion of lignocellulosic biomass is a promising route to produce renewable biofuels and oxygenated biochemicals while enabling the reuse, recovery, and recycling of materials containing carbon.

To convert biomass into renewable biofuels and biochemicals, biorefiners must first break down biomass (deconstructed) into smaller subunits. When this deconstruction is performed through thermochemical processing, an aqueous waste stream is often generated in addition to the valuable product.

These aqueous waste streams are predominantly water, but also contain organic compounds like acids and phenolics. Thus, these streams cannot be discharged directly to the sewer and therefore create additional wastewater treatment costs for the biorefinery.

Even though these waste streams contain useful organic materials, they still cannot be efficiently converted to biofuels or biochemicals because they are dilute, making up less than 3% of the waste streams’ composition, and are therefore difficult to separate.

In addition, it is generally not cost-effective to isolate the most valuable components from these organic materials due to the high-purity requirements typically necessary for bulk chemical production.

In response to this costly issue, National Renewable Energy Laboratory (NREL) research engineer Nolan Wilson, group manager Mark Nimlos, and research technician Joseph Roback, with funding support from the Bioenergy Technologies Office, developed a method to enhance the value of aqueous waste streams by isolating these organic compounds, specifically the monomers, which are precursors to everyday materials like plastics.

The team developed a process to isolate two lignocellulosic biomass-derived monomers from this aqueous stream—phenol and catechol. Phenols are primarily used in polycarbonate and phenol-formaldehyde resins, which have use in automotive, aerospace, building material, electronic, and consumer goods applications. Catechol can be found in insecticides, perfumes, and pharmaceuticals. READ MORE