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Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation
Published on: July 13, 2012
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Processing anaerobic sludge for extended storage as anaerobic digester inoculum
Jiajia Li1, Steven M Zicari2, Zongjun Cui3
1College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China; Department of Biological and Agricultural Engineering, University of California, Davis, CA 95616, United States.
Bioresource Technology
|June 8, 2014
Summary
Processing thermophilic anaerobic sludge reduces volume and moisture for easier handling. While storage decreases microbial inoculum activity, processed sludge shows signs of recovery after four months, improving biogas production rates.
Area of Science:
- Environmental Microbiology
- Anaerobic Digestion Technology
- Waste Management
Background:
- Thermophilic anaerobic sludge requires processing to reduce volume and moisture for cost-effective storage and transport.
- Sludge is utilized as a microbial inoculum for initiating anaerobic digester startup.
- Reducing sludge volume and moisture content is crucial for managing storage and transportation expenses.
Purpose of the Study:
- To evaluate the impact of processing (centrifugation and vacuum evaporation) on thermophilic anaerobic sludge.
- To assess the effect of storage duration (2 and 4 months) on the performance of processed sludge as microbial inoculum.
- To compare the biogas and methane production potential of fresh, processed, and stored sludge.
Main Methods:
- Thermophilic anaerobic sludge moisture content was reduced from 98.7% to 82.0% by centrifugation, and further to 71.5% by vacuum evaporation.
- Processed sludge samples were stored for 2 and 4 months.
- Biogas and methane production were measured using food waste and non-fat dry milk as substrates, with data analyzed using the modified Gompertz model.
Main Results:
- Fresh, unprocessed sludge exhibited the highest methane yield.
- Storage led to a 1-34% decrease in methane yield for both unprocessed and processed sludges.
- Processed sludges demonstrated a partial recovery of activity after 4 months of storage compared to 2-month samples, with increasing maximum methane production rates.
Conclusions:
- Sludge processing effectively reduces moisture content, aiding in storage and transport.
- While storage diminishes inoculum activity, processed sludge can partially regain its efficacy over time.
- The findings support the viability of processed thermophilic anaerobic sludge as a microbial inoculum for anaerobic digestion, with potential for activity recovery during extended storage.
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