Small temperature differences can improve the performance of mesophilic sludge-based digesters

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Mesophilic sludge digesters are crucial for biogas production.
• Optimizing operational parameters is key to enhancing energy recovery.

Purpose of the Study:

• To evaluate the impact of minor temperature elevations on biogas output in mesophilic digesters.
• To develop and test strategies for increasing biogas yields in full-scale operations.

Main Methods:

• Assessed methane production across samples from 15 full-scale digesters.
• Incubated samples at varying temperatures (35°C, 39°C, 42°C) to measure specific methane yield.

Main Results:

• Methane production significantly correlated with small temperature shifts.
• Specific methane yield increased from 35°C to 39°C, achieving 42–97.5 ml g VS⁻¹.
• A positive energy balance was achieved with minimal additional heating costs.
• Temperatures above 39°C sometimes reduced production.

Conclusions:

• Slight temperature increases are recommended for mesophilic sludge digesters to maximize biogas production.
• This strategy is particularly beneficial for digesters operating at the lower end of the mesophilic temperature range.