Effect of post-digestion temperature on serial CSTR biogas reactor performance.

Area of Science:

• Environmental Engineering
• Biotechnology
• Anaerobic Digestion

Background:

• Continuous-flow stirred tank reactors (CSTRs) are widely used for waste treatment and biogas generation.
• Post-digestion stages can further enhance biogas yield and process stability.
• Temperature is a critical factor influencing microbial activity in anaerobic digestion.

Purpose of the Study:

• To investigate the impact of post-digestion temperature on the performance of a lab-scale CSTR system.
• To compare the effects of 55°C, 37°C, and 15°C on biogas production, stability, microbial community, and methanogenic activity.

Main Methods:

• A serial CSTR system with a main reactor (55°C, 15 days HRT) followed by post-digesters (5.3 days HRT) was employed.
• Three different post-digestion temperatures (55°C, 37°C, 15°C) were tested.
• Biogas production, volatile fatty acid (VFA) concentrations, microbial community, and specific methanogenic activity were analyzed.

Main Results:

• Post-digestion at 55°C, 37°C, and 15°C resulted in additional biogas production of 11.7%, 8.4%, and 1.2%, respectively.
• The 55°C post-digester exhibited the highest biogas yield and superior stability, indicated by low VFA levels.
• High acidogen and methanogen activity was observed at 55°C and 37°C, while activity was minimal at 15°C.

Conclusions:

• Post-digestion temperature significantly influences biogas production and process stability in CSTR systems.
• Operating post-digesters at mesophilic temperatures (55°C and 37°C) maximizes biogas yield and microbial activity.
• Lower temperatures (15°C) drastically reduce methanogenic activity and overall system performance.