Long-term temperature measurement: Biogas digesters fermenting slurry

This paper reports the results of the temperature profile of the unheated and unstirred continuous fermenting bio-slurry in a fixed-dome Deenbandhu 2000 model. The digester is a brick-built system of bulk size 6 m3. The digester was monitored for eight months, measuring internal bio-slurry temperature. A K-type nickel chromium-nickel temperature sensor with a sensitivity of approximately 41 µV and response time of 0.8s in liquids was positioned at the centre of the digester to measure the slurry temperature. The sensor was connected to the data logger and programmed to record temperature readings every second for the entire study period. The study results reported give a clear indication about the reaction of bio-slurry temperature in the digester at a local level, particularly for the eight months’ period, which covered all seasons. The calculated values of the daily average temperature reveal that the digester was operating within the range of psychrophilic 10.32 and mesophilic 28.80 , although it sometimes operated at 35 and above during certain hours in summer. This study is useful for anaerobic digestion processes for biogas production. The results obtained can be used as a basis to estimate the amount of heat required to raise the temperature of digesters to reach an optimum temperature of mesophilic digesters