Abstract
High-solids anaerobic digestion of organic fraction of municipal solid waste often shows inefficient biomethane recovery due to mass transfer limitations. Consequently, this study presents a two-stage anaerobic digestion process combining high-solids anaerobic digestion followed by ultrasonication of digestate and wet-type anaerobic digestion for effective biomethane recovery from the organic fraction of municipal solid waste. The high-solids anaerobic digestion yielded methane production of 210 L CH4/kg volatile solids (VS). The digestate from the high-solids anaerobic digestion process was ultrasonicated at three different specific energy inputs (1000, 2500, and 5000 kJ/kg total solids (TS)). The increases in the soluble chemical oxygen demand (SCOD) concentrations (8%–32%) and volatile solids (VS) removal efficiencies (3.5%–10%) at different specific energy inputs were linearly correlated (R2 = 0.9356). Thus, ultrasonication led to the solubilization of particulate organics and released soluble organic matters. All ultrasonicated digestate samples showed significantly higher biomethane yields than that observed for the untreated digestate samples. The highest methane yield of 132 L CH4/kg VS was observed for a specific energy input of 5000 kJ/kg TS, which was 1.94 times higher than the control (68 L CH4/kg VS). Although specific energy inputs of 1000 kJ/kg TS and 2500 kJ/kg TS showed comparable methane yields (113–114 L CH4/kg VS), they were ~1.67 times higher than the control. Overall, our results suggest that an integrated system of high-solids and wet-type anaerobic digestion with pre-ultrasonication of digestate has the potential to provide a technically viable solution to enhance biomethane recovery from the organic fraction of municipal solid waste.
Highlights
The rapid urbanization and increased population levels have considerably accelerated the global municipal solid waste (MSW) generation
132 L CH4 /kg volatile solids (VS) was observed for a specific energy input of 5000 kJ/kg total solids (TS), which was 1.94 times higher than the control (68 L CH4 /kg VS)
This study presents high-solids anaerobic digestion followed by wet type anaerobic digestion of ultrasonicated digestate for enhancing the methane yield from OFMSW
Summary
The rapid urbanization and increased population levels have considerably accelerated the global municipal solid waste (MSW) generation. According to a report published by the Organisation for Economic Co-operation and Development (OECD), the global MSW generation is expected to be increased from 1.3 million tons to 2.2 billion tons over the period 2015–2025 [1]. Only a small fraction of MSW is recycled or converted to value-added resources, with the rest being burned or landfilled due to a lack of suitable technologies and economic constraints [2]. The landfilling of MSW nowadays is under a challenge of requisite space due to the decreasing land availability [3]. The landfilling of organic fraction of municipal solid waste (OFMSW), which was estimated to be ~46%. Of the global MSW [4], is criticized because of its high environmental impacts.
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