Integrative process for rubberwood waste digestibility improvement and levulinic acid production by hydrothermal
Boonya Charnnok1, Navadol Laosiripojana2
1Department of Specialized Engineering, Energy Technology Program, Faculty of Engineering, Prince of Songkla University, Hat Yai Campus, Hat Yai District, Songkhla Province 90110, Thailand; Department of Civil and Environmental Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai Campus, Hat Yai, Songkhla 90110, Thailand.
Abstract:
This study aimed to develop an integrative process for converting rubberwood waste into sugars, methane, and levulinic acid. Sulfuric acid pretreatment at pH 2.5 yielded the highest glucose of 182.5 g/kg rubberwood waste. Replacing the acid solution with sulfuric acid wastewater led to 11.0% lower glucose yield than that obtained using sulfuric acid. However, the cost reduction equals the difference in revenues between sulfuric acid wastewater and sulfuric acid, resulting in similar total cost and revenue. Furthermore, thermal reactions of the process water resulted in the highest yield of levulinic acid, 17.9% at 220 °C. Meanwhile, anaerobic digestibility of enzymatic hydrolysis residue was increased using inoculum from a digester treating pig farm wastewater owing to the acetoclastic pathway. These co-products potentially returned additional revenues, accounting for 45.8% of the total revenue. These findings highlight the potential pathway for valorization of rubberwood waste via the integrated approach with acid wastewater pretreatment.
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