Anaerobic Digestion and Co-digestion of Poultry Droppings (PD) and Cassava Peels (CP): Comparative Study of Optimal Biogas Production

Abstract

An investigation of the effects of poultry droppings (PD) on the anaerobic co-digestion of cassava peels (CP) has been conducted in order to determine the kinetics for optimal biogas production. The laboratory batch anaerobic digestion were carried out in five (5) different ten-litre anaerobic digesters which were used for the fermentation of the substrates with cumulative biogas production of 13.1, 24.6, 16.7, 8.6 and 7.1L/g volatile solid(VS). The digesters A, B, C, D and E with process conditions of (100% PD and 0% CP), (75% PD and 25% CP), (50% PD and 50% CP), (25% PD and 75% CP) and (0% PD and 100% CP) respectively, were incubated for forty four (44) days at ambient mesophilic temperature of 37±1 oC at a pH of 6.7. The gas production did not begin until the second day for the first four digesters while that of digester E started on the fourth day, (this is as a result of high cellulose content) and then increased steadily until it reached a maximum biogas yield between the 18th and 22nd day of anaerobic digestion. The highest biogas production of 24.6L/g volatile solid(VS) recorded in digester B could be attributed to better synergy of microorganisms in the digester as a result of the presence of some limited quantity of cassava peels and a C/N ratio of 23.4. This result shows that biogas production could be enhanced effectively through co-digestion process of substrates.