Biogas Production Potential of Castor Bean (Ricinus Communis L.) Cake

Abstract

Every passing day the world’s population is increasing that means more and more energy demand and the resources fulfilling energy demand are depleting rapidly. Most commonly available resources in developing countries like Pakistan are fossil-fuel based energy sources. There are two major shortcomings of using fossil fuels, first is environmental hazard and second is depletion of fossil fuels. Both of above-mentioned reasons encourage researchers like us to search for renewable energy resources that will help us to make our environment greener and safer. In developing countries like Pakistan, the second most important issue is waste management. Waste management is not properly administered, and basic infra-structure is missing. So, utilization of waste material as a source of energy is an emerging concept. For example, utilization of biomass as a substrate for biogas production etc. In this study castor seeds were evaluated for their biogas production ability. Residues left after the solvent extraction process were utilized and their net biogas production was calculated. In the batch anaerobic digestion maximum. Biogas yield was exhibited by the oil which was 619 Nml/g of VS (0.619 NL/g VS). Methanol and Ethyl acetate residues also produced good amount of biogas, 499 Nml/g of VS and 564 Nml/g of VS respectively. During the continuous anaerobic digestion process, reactors were run at OLR 1g of VS per day and HRT was kept constant at 10 days. After achieving the steady state biogas production from the reactors was calculated. Maximum biogas yield was achieved by methyl acetate residues which was 312 Nml/ g of VS of substrate added per day, followed by chloroform 297 Nml/ g of VS of substrate per day. Minimum yield was produced by the whole seed 110 Nml/ g of VS of substrate per day. VFAs and alkalinity of the reactors were also measured after regular interval of time. Maximum VS reduction was achieved in the methyl acetate residues around 64% followed n-Hexane and ethyl acetate residues in which VS reduction was observed around 63 and 61% respectively. The current study signifies a direction to use the use of castor seeds and its residues for the use of biogas production. Leftover residues after the solvent extraction not only provide a renewable source for biogas production but also can also be managed and utilized in a more sustainable way