Synthesis of Hydrophobic Microbeads from Lignin Fractions

Plastics microparticles, a.k.a. microbeads, are ubiquitously used as exfoliants in personal care products including facial scrub, exfoliating soap, and toothpaste. As tiny spheres with less than 5 millimeters in diameter, microbeads are able to escape wastewater treatment facilities, enter the aquatic environment, and become potent pollutants in lakes and oceans. Commercially available microbead products are manufactured using synthetic polymers such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (PTFE), and nylon. These polymers are not biodegradable, and pose a lasting threat to both the marine ecosystem and human health. Alerted by the hazardous effects of microbeads, a number of state legislations (CA, CO, CT, IL, IN, ME, MD, NJ, WI) have enacted bans on personal care products containing non-biodegradable microbeads.

Polymeric lignin, a co-product of biomass saccharification process, is a promising feedstock for production of plastic materials. As a natural polymer, lignin consists of aromatic units connected by linkages that are labile to biodegradation. Lignin is intrinsically hydrophobic, and has great potential applications as a microbead precursor. Here we demonstrate a novel method for processing enzyme saccharification lignin to a material suitable for microbead production. Fractionated lignin is chemically modified with depolymerizing and crosslinking agents before subsequent processing of the lignin into microbeads using mechanical methods.