Development of stabilization methods using a pilot scale anaerobic digester for seasonal variations in kitchen wastes for improved methane production with zero breakdowns

• Published in: Cleaner Engineering and Technology 2020-12, Vol.1, p.100015, Article 100015
• Main Authors: Isha, Adya, Kumar, Subodh, Jha, Bhaskar, Subbarao, Paruchuri M.V., Chandra, Ram, Vijay, Virendra Kumar
• Format: Article
• Language: English
• Subjects: Anaerobic digestion (AD); Energy and economic analysis; Kitchen waste; pH maintenance; Pongamiade-oiled cake
• ISSN: 2666-7908; 2666-7908
• DOI: 10.1016/j.clet.2020.100015

Anaerobic digestion of kitchen waste faces the challenge of frequent composition variation and rapid digester acidification due to its highly degradable nature. Considering this challenge, one year long pilot scale anaerobic digestion study was conducted in the anaerobic digester of 25 ​m3/day capacity with seasonal kitchen waste (fruits and vegetable waste). The seasonal variation in kitchen waste content was studied by dividing a year into six seasons (each season comprising 60 days), namely, spring, summer, monsoon, autumn, early winter, and prevernal winter. Considering all the properties of kitchen waste, the anaerobic digestion experiment was conducted with the organic loading rate (OLR) of 0.60–0.72 ​kg VS/m3/day. The specific biogas production for all the seasons was found to be 0.56–0.68 ​m3/kg VS, with the volumetric methane content of 54.3–62.8%. The average seasonal specific methane production was observed in the range of 0.30–0.41 ​m3/kg VS. The anaerobic digestion conversion efficiency of 55.3–67.0% was found for the anaerobic digestion of the wastes. The problem of the rapid acidification of kitchen waste has been rectified with the addition of protein-rich de-oiled pongamia cake in place of alkali chemicals. The economic analysis of kitchen waste based anaerobic digestion showed the maximum economic benefits of biogas production as INR 30,783 for its utilization as LPG and INR 37,777 for its utilization as electricity for the summer season compared to all other seasons. The extra economic benefits earned by the utilization of the digested slurry as organic manure, as it contains a good amount of nitrogen (N) 2.3–2.6%, phosphorus (P) 0.6–0.9%, and potassium (K) 0.7–1.1%. [Display omitted] •Pilot-scale operation of kitchen waste-based anaerobic digester.•Rapid acidification of kitchen waste hinders the operation of anaerobic digester.•The addition of protein and fat-rich material helps to maintain the appropriate pH of the digester.•The challenge of pH drop in the digester was resolved by using pongamia de-oiled cake instead of any chemicals.