Enzymatic Pretreatment of Sugarcane Bagasse and Fruit-Vegetable Waste for Energy Conversion by Co-digestion

Lignocellulosic crop residues have a high energy potential through anaerobic co-digestion (AcoD), due to their carbon content. The lignin content makes them recalcitrant to digestion thus pretreatment is essential. Biological pretreatment (application of enzymes) is of growing interest due to its environmental friendly process. A few studies have been conducted on the direct addition of enzymes. Hence, this study has evaluated the impacts of addition of laccase and lipase- followed by alkaline pretreatment- in the AcoD of highly lignocellulosic substrate- sugarcane bagasse (SB) and readily degradable co-substrate- fruit vegetable waste (FVW). Batch digesters were set-up for digestion at same initial conditions and mesophilic temperature range for both enzymes. Till the end of 81-days long process, lipase produced 1093.6 ml/g-VS cumulative biogas and 80.8% VS reduction. In comparison, laccase produced 988.6 ml/g-VS cumulative biogas (11% less than lipase) and 72.6% VS reduction. The application of lipase enzyme was, therefore, more effective for the stated substrate, as compared to laccase enzyme. Lipase remained more effective, because the concentration of VFA produced in laccase digester was higher, causing lower pH, and hence, process inhabitation. Graphical Abstract