Biogas Production from Castor (Ricinus communis Linn) seedcake in the presence and absence of Buffalo Dung

Abstract

A laboratory scale digester experiment was conducted using three treatments- control (only buffalo dung), test A (castor seed cake and buffalo dung), and test B (only castor seed cake). Treatments were replicated twice. Digestion was carried out in 5L glass digester bottle connected with one gas holder bottle of 2L capacity which remains joined with another glass bottle of 2L capacity for replacement of water in gas holder. The experiment was run on 6% total solids content in all the digesters. Initially, 10% inoculum collected from running biogas plant was added to all the sets. Production of biogas was measured by water displacement method from 73 days onwards upto 163 days of experimentation. Digested slurry coming out from the digesters was also analyzed for various chemical parameters important from plant nutrient’s point of view. During this study, it was found that, biogas production was 86.88% and 100.58% higher in digesters fed with mixture of buffalo dung + castor seedcake and only castor seedcake compared to that in control set respectively. The pH was near neutral in all sets during whole experiment. While, electrical conductivity was 88.16, 268.61 and 865.20% higher in effluent slurry compared to the feeding slurry in digesters fed with buffalo dung, buffalo dung + castor seedcake and only castor seedcake respectively. On the contrary, total solids, total volatile solids and total organic carbon decreased in effluent slurry over feeding slurry. It was revealed from the whole study that, castor seedcake alone or as mixture with buffalo dung, have positive effect on biogas production and nutrients content of digested slurry.