Hot-water extraction of Miscanthus × giganteus prior to soda-AQ pulping: a biorefining perspective

Agricultural residues, such as giant miscanthus (Miscanthus × giganteus, a hybrid of Miscanthus sinensis and Miscanthus sacchariflorus), show a great potential for use in lignocellulosic biorefineries. In this study, various hydrolysates were prepared from miscanthus stalks under varying temperatures (140 and 150°C) and reaction times corresponding to P-factors of 50 and 200, prior to undergoing sulfur-free soda-anthraquinone (AQ) pulping (alkali charge 15% and AQ charge 0.05% on oven-dried feedstock) to recover carbohydrate-derived material. During hot-water extraction, a significant mass removal (10%) of the initial miscanthus was obtained at 150°C with a reaction time of 240 min (P-factor 200). Hydrolysates were characterized in terms of pH and the amounts of carbohydrates, volatile acids (acetic and formic acids), and furans. Hot-water extraction also influenced the delignification stage; the highest pulp yield (62%) for the hot-water-extracted miscanthus (at 150°C with a P-factor of 200) was obtained at 165°C with a cooking time of 60 min (effective alkali charge 15% and AQ charge 0.05% on oven-dried feedstock). Results revealed that giant miscanthus is an attractive feedstock for this kind of integrated biorefining.