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

ABSTRACT

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.

KEYWORDS:

• Miscanthus × giganteus
• biorefining
• hemicelluloses
• hot-water extraction
• soda-AQ pulping
• yield
• P-factor

Acknowledgements

The authors are grateful for the financial support from the Doctoral School in Chemistry at the University of Jyväskylä, Finland. We are also thankful to MSc Yasir Iqbal from the University of Hohenheim, Germany, for kindly providing miscanthus stalks for our experimental work. Additionally, financial support from the Maj and Tor Nessling Foundation (Joni Lehto) is gratefully acknowledged.

Disclosure statement

The authors declare that there is no conflict of interest regarding the publication of this paper.