Comparative evaluation of raw and detoxified mahua seed cake for biogas production

Non-edible oils are progressively being utilized for production of bio-diesel around the world which embraces the future assurance towards renewable energy. After the extraction of oil, 50–60% of the material, termed as de-oiled seed cake, goes waste due to the presence of toxins. The present paper evaluates the use of raw and detoxified (water treated; detoxified up to 75%) non-edible oil seed cake, Madhuca indica, for biogas production. Different treatments comprising of varying proportions of raw/detoxified mahua seed cake (MC) and cow dung (CD) were designed. Detoxified cake(s) produced significantly better results compared to raw cake. Combination of 50% hot water detoxified MC and 50% CD gave maximum biogas production of 442 L/kg total solids with 58.5–60% methane content. This gave an increase of 125% over CD, along with 33.15% and 34.05% reduction in total solids (TS) and volatile solids (VS), respectively. Significant reduction in celluloses (34.46%) and hemicelluloses (29.76%) and an increase in the nutrients (N, P, K) of the digested slurry were obtained for the same. Anaerobic digestion of mahua cake, detoxified by simple water treatments, offers one of the viable methods for waste to energy generation.