Performance of two-stage vegetable waste anaerobic digestion depending on varying recirculation rates.
Vegetable waste, which characterized by high moisture content, was evaluated as a substrate for biogas production. The effects of recirculation rate (RR) on the performance of two-stage anaerobic digestion were investigated. The system was operated at an organic loading rate of 1.7 g VS/L/d with varying RRs (0, 0.6, 1, and 1.4). Results demonstrated that volumetric biogas production rates in acidogenic reactor increased from approximately 0.2 7 L/L/d to 0.97 L/L/d, when pH is increased from approximately 5.1 to 6.7. These indicate that recirculation of alkaline effluent from the methanogenic reactor helps create a favorable condition for biogas production in the acidogenic reactor. The decrease in chemical oxygen demand (COD) concentrations from approximately 21,000 mg/L to 6800 mg/L was also observed in the acidogenic reactor. This condition may be attributed to dilution under recirculation. The dynamics between hydrolysis and methanogenesis under recirculation indicated that mass transfer capacity between two-stage reactors improved.
College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, PR China.
Zhuang
Z
Zuo
Key Laboratory of Clean Utilization Technology for Renewable Energy in Ministry of Agriculture, College of Engineering, China Agricultural University, Beijing 100083, PR China. Electronic address: wushubiao@gmail.com.
Shubiao
S
Wu
College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, PR China.
Wanqin
W
Zhang
Key Laboratory of Clean Utilization Technology for Renewable Energy in Ministry of Agriculture, College of Engineering, China Agricultural University, Beijing 100083, PR China.
Renjie
R
Dong
D000693:Anaerobiosis; D056804:Biofuels / Q000382:microbiology; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors / Q000382:microbiology*; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation; D008697:Methane / Q000378:metabolism; D012037:Refuse Disposal / Q000295:instrumentation* / Q000379:methods*; D013997:Time Factors; D014675:Vegetables / Q000737:chemistry*; D014866:Waste Products
D056804:Biofuels; D005232:Fatty Acids, Volatile; D014866:Waste Products; D008697:Methane
Anaerobic digestion; Biogas production; Recirculation rate; Two-stage process; Vegetable waste