Characteristics of Biogas Production from Organic Wastes Mixed at Optimal Ratios in an Anaerobic Co-Digestion Reactor

• Published in: Energies (Basel) Vol. 14; no. 20; p. 6812
• Main Authors: Song, Young-Ju, Oh, Kyung-Su, Lee, Beom, Pak, Dae-Won, Cha, Ji-Hwan, Park, Jun-Gyu
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-10-2021
• Subjects: anaerobic co-digestion; Anaerobic digestion; Animal manures; Animal wastes; Atmospheric pressure; Biodegradability; Biodegradation; Biogas; Efficiency; Food; Food waste; Gases; Hazardous materials; Livestock; livestock manure; Load distribution; Loading rate; Manures; Methane; Microorganisms; Mixing ratio; Nitrogen; Organic loading; Organic matter; Organic wastes; Reactors; Sewage sludge; Sludge; Sludge digestion; Substrates; Sulfur; Volatile solids; Yield
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en14206812

This study determined the optimal mixing ratio of food waste and livestock manure for efficient co-digestion of sewage sludge by applying the biochemical methane potential (BMP) test, Design Expert software, and continuous reactor operation. The BMP test of sewage sludge revealed a maximum methane yield of 334 mL CH4/g volatile solids (VS) at an organic loading rate (OLR) of 4 kg VS/(m3·d). For food waste, the maximum methane yield was 573 mL CH4/g VS at an OLR of 6 kg VS/(m3·d). Livestock manure showed the lowest methane yield. The BMP tests with various mixing ratios confirmed that a higher mixing ratio of food waste resulted in a higher methane yield, which showed improved biodegradability and an improved VS removal rate. The optimal mixing ratio of 2:1:1 for sewage sludge, food waste, and livestock manure was determined using Design Expert 10. Using continuous co-digestion reactor operation under an optimal mixing ratio, greater organic matter removal and methane yield was possible. The process stability of co-digestion of optimally mixed substrate was improved compared with that of operations with each substrate alone. Therefore, co-digestion could properly maintain the balance of each stage of anaerobic digestion reactions by complementing the characteristics of each substrate under a higher OLR.