Production and kinetic studies of biogas from anaerobic digestion of banana and cassava wastes

Abstract

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.