Production and Kinetic Studies of Biogas from Anaerobic Digestion of Banana and Cassava Wastes

Purpose In the present study, anaerobic digestion of cassava (Manihot esculenta) and banana (Musa paradisiaca) wastes was investigated and the kinetic modelling of the conversion process was carried out. Methods The experiments were carried out in a batch reactor under mesophilic conditions. Results The total solids content of cassava and banana were 14.7% and 15.7% respectively, moisture content of cassava and banana were 85.3 and 84.3% respectively while the volatile solids content of cassava and banana were 92.32% and 96.27% respectively. The cumulative biogas yield of cassava substrate reached 18.8 L/g VS after 30 days while that of banana reached 14.24 L/g VS in the same digestion time. The first- order kinetics showed that the cassava substrate had greater potential for biogas production due to its relatively higher k value (0.19) than the banana substrate (0.03). Modified Gompertz kinetic parameters showed a total biogas production of 30.54 L/gVS for cassava at a maximum production rate of 0.56 L/g/VS/day while banana had a total biogas production of 24.91 L/gVS at a maximum production rate of 0.44 L/g/VS/day. The short lag phase of the digestion process indicatedthat the microbes acclimatized quickly to the slurry environment. The modified Gompertz model was a better fit for the experimental and simulated data, based on the closeness of R2 values to 1. Conclusion Both cassava and banana substrates showed great potential for biogas production. Therefore, biogas generated from waste valorization can mitigate over-dependence on depleting fossil fuel/crude oil in Nigeria and Africa.