Investigation on Water Hyacinth in Anaerobic Co-Digestion for Biogas Production: A measure to Reduce Kosavampatti and Phoosur Lake Municipal Solid Waste Loading

Abstract

The main aim of this study was to evaluate the lab scale, microbe-enhanced biogas production from water hyacinth blended with poultry waste and cow dung. A mesophilic anaerobic two-stage continuous reactor was set up to study the co-digestion for enhanced biogas production. The optimized mixing ratio of cow dung, water hyacinth, and poultry litter (2:1:1; 4:3:1 and 5:2:1) was used along with the effective microbial solution in a two-stage continuous reactor. The biogas yield was maximum in the 2:1:1 blend than the blends with a mixing ratio of 4:3:1 and 5:2:1. The reactor-loading rate was 4 and 5 g.L-1.day-1 with a retention time of 30 and 60 days respectively. The two-stage anaerobic digestion helps in controlling toxicity by acidogenesis and enhances energy production, thereby proving to be a technology that prevents environmental deterioration and enhances energy recovery, both of which are twin issues that need scientific attention. Maximum specific biogas of 0.128 Nm.L.g-1 of Volatile solid reduction (VSR) in hydrolyzer and 0.205 Nm.L.g-1 of VSR in methanizer was obtained at an optimized Carbon/Nitrogen (C/N) ratio of 20.8. The co-digestion of protein-rich waste with a carbon-rich source offers a reduced acclimatization period in the hydrolyzer with an increased C/N ratio, thereby increasing the biogas yield as observed in the methanizer. Several other parameters including Ammonia level, Volatile Fatty Acids influenced by the reactor alkalinity also determine the biogas yield. With increased alkalinity, free ammonia increases and may be inhibitory for anaerobic fermentation and may be toxic for methanogenic bacteria, thereby contributing to the reduction in biogas yield. The present investigation has led to a novel biogas and power-producing clean development mechanism (CDM) for the first time from a heterogeneous mixture of animal excreta and plant waste (livestock droppings, cow dung, and water hyacinths). The waste samples have been collected from sewage and sullage polluted Kosavampatti Lake and Phoosur lake in Namakkal district of Tamilnadu, India therein ending up in a high quantity of CO2 mitigation.