Potential of 2,3-butanediol, volatile fatty acid and methane production from medium and low-value forest industry side streams.

Medium- and low-value side streams from the forest industry, such as sawdust and biosludge, are typically used for energy production, yet they offer potential for higher-value products via biological conversion. This study explores the combined production of 2,3-butanediol (BDO) and volatile fatty acids (VFAs) from birch sawdust and sludges from kraft mill pulping and wastewater treatment, alongside anaerobic digestion for methane. Integration of BDO and VFA production is evaluated by valorising BDO process residues. Pretreated birch sawdust yielded BDO 0.12 g/g of total solids (TS), and VFA up to 0.68  g/gTS, indicating economic feasibility. Combining both processes in a biorefinery could enhance revenues. Kraft mill sludges produced BDO up to 0.88 g/gTS, VFAs between 0.45-0.64  g/gTS, and methane 430 Nm3/t volatile solids (VS) without pretreatment. These findings demonstrate the potential of forest industry side streams for producing bio-based chemicals and methane, supporting integrated biorefineries for improved resource efficiency and value creation.