Aldehyde-Assisted Fractionation Enhances Lignin Valorization in Endocarp Waste Biomass

Endocarp biomass, which forms much of the inedible portion of nuts and stone fruits, is a promising feedstock for aromatic chemical production due to its high lignin content and because it is a food industry waste. Here, we tested the nut shells and fruit kernels of seven species and report that their aromatic monomer yields can surpass those obtained using wood chips by up to 30% on a dry biomass basis due to their high lignin content. We also observed that acid-catalyzed aldehyde-assisted fractionation (AAF) facilitates lignin valorization when using industrially relevant particle sizes (3-5 mm) with monomers yields that are 80% to 170% higher than those obtained with reductive catalytic fractionation (RCF) for similarly sized particles. This difference was highly correlated with the feedstock surface area, demonstrating the importance of acidic pretreatment for substrates with low accessibility and/or large particles.