| Résumé | Currently, the majority of the biomass residue around Canada is incinerated or landfilled although it still contains valuable chemicals such as tannins (2–40 wt %) that can be extracted and used for the production of materials such as binder for plastic composites or polyols for polyurethane foam synthesis. However, most of the methods currently used for tannin extraction involve chemicals such as sodium sulfite, sodium bisulfite or sodium carbonate that are not environmentally friendly. Therefore, cleaner methods of tannin extraction are re-emerging as alternatives. Today’s challenge is the development of a cleaner method that is both cost-effective and environmentally friendly as the one presented in this paper to extract tannins from Canadian yellow birch bark. The bark was mechanically pretreated and then tannins were extracted using hot water. Tannin solution was separated from the residue by centrifugation and the tannin extracts were recovered after water evaporation. The yield, energy and water consumption results of the entire extraction process showed that tannin extraction and tannin isolation are the most energy consuming steps (23% and 72% of the total energy used, respectively). Three methods were developed to reduce the energy and water consumption while maximizing the tannin yield. The first method assisted by ultrasound allows to save up to 34% of energy and 34% of water for the tannin extraction step while increasing the tannin yield by 52% compared to the hot water extraction method. The second method which recycles the extract solution allows a consumption reduction of 39% in energy and 40% in water for the tannin isolation step compared to the hot water extraction method. Interestingly, a combination of Methods provides the most significant energy and water reduction for the whole process, which are 41% and 49%, respectively, while increasing the tannin yield by 13% compared to the hot water extraction method. |
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