Strategies for designing sustainable biomass microbeads for consumer application

While plastic microbeads are useful as exfoliants and rheological modifiers in a wide range of personal care consumer products, billions of these primary microplastics enter the environment daily in the US alone, causing extensive environmental harm. Non-derivatized biomass, in the form of microcrystalline cellulose and Kraft lignin, presents an abundant sustainable alternative to plastic microbeads, but there are a number of processing challenges associated with shaping these forms of biomass into microbeads with the appropriate size, shape, and stiffness to compete with commercial plastics. The poor solubility of cellulose in most conventional solvents, combined with the high viscosities of cellulose solutions create difficulties in dispersing these solutions either through extrusion or emulsion techniques to attain microbeads of the appropriate size – hundreds of microns in diameter. To overcome these challenges, we tuned the extensional viscosity of biomass solutions to enable smaller beads from an extrusion method. Using lessons learned from this extrusion method, we developed our high-yield emulsion method to scalably produce biomass microbeads. Using this method, we tuned interfacial tension to create beads of the appropriate size with a wide range of morphologies, resulting in a viable platform to eliminate a major source of primary microplastics from widely available material.