An overview of bio augmentation of methane by anaerobic co-digestion of municipal sludge along with microalgae and waste paper

Municipal sludge from primary settling tanks of the Sewage treatment plant (STP) is a potentially important bio mass for the production of bio gas. Large amount of sludge is daily produced at wastewater treatment plants (WWTPs) where anaerobic digesters are located. Coupling the waste water treatment plant with the micro-algal culture is currently considered one of the most promising avenues towards the production of renewable bioenergy, either in the form of biodiesel or biogas. Research on anaerobic digestion of microalgae and sewage sludge will be important for the future of WWTPs because it could be a key step for recycling nutrients for algal cultivation as well as for energy recovery. Any co-substrate can have a co-effect in the sense that they stimulate enzymatic synthesis that can also improve the anaerobic digestion yield. Studies have shown that co-digestion can increase the anaerobic digestibility of algae by improving the substrate composition. Early studies have shown that due to the difference in anaerobic inocula, waste composition, and the experimental environment the quantity and the quality of the methane production vary widely. Sewage Sludge improves the digestibility of microalgae and enhances the production of methane. Co-digestion of waste paper and algal sludge could efficiently balance the feed stock Carbon-Nitrogen(C/N) ratio between 20-25 likely to benefit the methane production rate. This paper reviews recent experimental findings of the co digestion of algae with sewage and several substrates and the methods to enhance the methane production and the factors affecting the augmentation of the bio gas. (C) 2015 Elsevier Ltd. All rights reserved.