Green Biorefinery Side Stream as a Source of Chlorophyll Pigments, Lignin, and Cellulose for Textile Fibers

Green biorefineries are key to a biobased economy and to reducing the carbon footprint of several supply chains. Achieving this goal requires utilizing as many material streams as possible while focusing on value-added products that offer economic benefits. Herein, we investigate the potential of a fibrous byproduct from protein extraction of green perennial biomasses (press cake) as an alternative raw material to pigments and wood-based products. We propose an integrated process that further refines and valorizes the press cake to obtain chlorophyll pigments, lignin, and cellulosic pulp. First, the chlorophyll extraction from grass-clover press cake was optimized, and its impact on the subsequent pulping step was evaluated, revealing that the extraction with ethanol and acetone did not affect the pulping step, while DMSO presented several issues. Pulping conditions were then optimized to maximize the cellulose content in the pulp without compromising the quality of the lignin stream or the recovery yields. The resulting high-cellulose pulps, approaching a cellulose content of 90 wt %, were successfully spun into textile fibers through wet-spinning, as one example of added-value application. Our results present a proof-of-concept for optimizing green biorefineries to obtain four added-value products from renewable grass-clover biomass: proteins, chlorophyll pigments, cellulose pulp, and lignin.