Anaerobic digestion of banana stem waste

Waste banana stem has a high organic content (83%); with 15–20% (w/w) lignin and cellulose which gives it a sheath-like texture. Banana stem slurries (BSS) at 2–16% total solids (TS) concentration were anaerobically digested under mesophilic (37–40°C) as well as thermophilic conditions (50–55°C) in batch culture. The final biogas yields, 267–271 l/kg TS fed, were observed with 2–4% TS slurries, under mesophilic conditions. In the thermophilic range, the biogas yields, 212–229 l/kg TS fed, were found with 2–8% TS slurries. However, thermophilic digestion rates were 2.4 times faster than mesophilic. Methane accounted for 59–79% of the total biogas. Methane yield was maximum at 2% TS BSS in both the temperature ranges. The process led to 45–50% reduction in organic solids and 40–55% reduction in COD. With 16% TS BSS inhibition resulted in 50–60% loss in biomethanation process efficiency.