Evaluation of an integrated process to fully utilize bamboo biomass during the production of bioethanol

- Sequential autohydrolysis-alkaline extraction efficiently fractionated bamboo.
- Autohydrolysis improved the accessibility of silica and lignin to NaOH.
- Silica, lignin and sugars were recovered from the two pre-extraction liquors.
- Both recovered sugars and two-stage treated solids were used to produce ethanol.

Aiming for the complete utilization of bamboo biomass, an integrated process which combines ethanol production with the recovery of silica and lignin was proposed. To reduce chemical charge required for the fractionation of silica and lignin from bamboo and improve the digestibility of the obtained substrate, a sequentially two-stage pretreatment process of autohydrolysis and alkaline extraction was carried out. From the view of enhancing enzymatic hydrolysis and recovery of silica and lignin, a two-stage treatment of autohydrolysis at 180 °C for 90 min followed by alkaline extraction at 100 °C with 6% NaOH (based on pretreated chips) for 120 min was optimized. About 93.7% of original silica and 75.7% of original lignin could be recovered from bamboo. Enzymatic hydrolysis and fermentation of carbohydrates showed that an overall sugar yield of 88.6% of original sugar content and an ethanol recovery of 0.467 g/g sugar were achieved based on the proposed scheme.