Lignin Nanoparticles: Contribution of Biomass Types and Fractionation for an Eco-Friendly Production

In order to handle urgent energy and environmental issues, the development of a circular economy supported by lignocellulosic biorefineries is essential right now. In this respect, lignin should no longer be seen as a waste or byproduct but as a renewable and abundant resource. This is why research has recently focused on the development of lignin nanoparticles (LNPs) from kraft lignin (KL), opening up new value-added areas. However, to date, no study has focused on a top-down lignin-based approach over further produced LNP properties, i.e., the contribution of the initial raw biomass types (hardwood, softwood, and herbaceous material) and lignin macroparticle extraction. This top-down, lignin-based approach, considering lignin valorization as the primary resource from the design phase, offers insights into the chemical lignin structure and functional group interactions in LNP formation. To this end, a new water steam explosion pretreatment was carried out upstream of an ethanol-organosolv treatment in order to rapidly extract pure lignin, which is then reduced to nanosize by antisolvent precipitation. We show that the initial raw biomass type such as lignin extraction (organosolv lignin compared to KL) makes a significant difference to particle size (50–250 nm), aggregation, and morphology in aqueous suspensions. The tailored LNPs formed by this eco-friendly, simple, fast, and high-yield process (7–15 wt % LNPs of initial biomass byproducts), which can be upscaled for industrial purposes, are stable over 90 days' storage and have better properties than those of kraft LNPs. LNPs resulting from this work therefore have great potential for high value-added applications such as cosmetics and medicine.