Municipal Solid Waste Biogas Production Enhancement Using a Hybrid Landfill Bioreactor: A Case Study ^†

This study aimed to investigate the application of hybrid bioreactor technology for biogas production enhancement from a municipal solid waste organic fraction (OFMSW). Two bioreactor (Br) columns were operated for up to seven (7) months to simulate a typical (Br-1) and a hybrid (Br-2) landfill bioreactor, respectively. The OFMSW used included kitchen, garden, and paper waste at a ratio of 16:3:1. Partial aeration during the first stage was practiced, and diluted leachate with water was recirculated throughout the operation in Br-2 while tap water was added in Br-1 for humidification. The results showed that partial aeration and diluted leachate recirculation led to greater performance in terms of accelerated methanogenesis onset and biogas production enhancement. Methanogenesis onset occurred after 90 days for Br-2, while it was realized after 143 days for Br-1. A biogas accumulation of 21.52 L at an average rate of 0.12 L/day was produced from Br-2, which was higher than the volume of accumulated biogas produced in Br-1 of 8.75 L, averaging 0.05 L/day for 7 months. The leachate pH slowly increased and fluctuated around 7 in Br-1, while in Br-2, it quickly increased from 5.24 to 8.2 during the methanation phase. The reduction in TOC (260 mg/L) and COD (4000 mg/L) indicated the maturation phase of the leachate in Br-2, while Br-1 had high values of TOC (461.1 mg/L) and COD (10,000 mg/L) ranging within the methanation phase after 6 months of operation. The TOC/COD ratio of 0.63 was also indicative of a stabilized leachate in Br-2, while Br-1 had a lower ratio than 0.5. The results indicated that diluted leachate recirculation and partial aeration had a considerable effect on biogas production and the onset of methanogenesis. Partial aeration introduced oxygen into the process, while leachate recirculation re-introduced the discharged nutrients with water, diluting the high concentration of leachate pollutants.