Mesophilic and thermophilic anaerobic digestion

You may or may not have heard of the terms ‘mesophilic’ and ‘thermophilic’ anaerobic digestion, especially in conjunction with cultures and the bacteria used during the AD process. But it’s these bacterias that are fundamental to generating energy from waste; turning the AD feedstock into gas that can be pumped into the gas grid and, as such, understanding the difference between mesophilic and thermophilic anaerobic digestion is pretty important! Let’s explore… 

The difference between mesophilic and thermophilic anaerobic digestion

Mesophilic anaerobic digestion: ‘mesophilic’ refers to medium-temperature loving bacteria which will ferment best at temperatures of around 30°C. Mesophilic anaerobic digestion is the most common AD system due to it having a more stable operation. However, within this, it’s also considered to yield a lower biogas production rate. 

Thermophilic anaerobic digestion: ‘thermophilic’ operates at a much higher temperature range than mesophilic; between 50 and 65°C. Although less stable than it’s cooler counterpart, thermophilic anaerobic digestion does reduce pathogens whilst providing more rapid reaction rates. Alongside this, whilst thermophilic anaerobic digestion is generally more efficient in biogas production it is associated with higher maintenance cost.

Which is best for your project? 

Mesophilic anaerobic digestion is the most commonly used AD process with reported 90% of anaerobic digestion plants utilising this system. 

This is largely due to the stability of mesophilic AD coupled with the fact that it is widely considered to be much easier to maintain than thermophilic AD.

However, it really does depend on your unique project as to which system is most suitable, and the best thing to do when looking into mesophilic and thermophilic anaerobic digestion is to speak to an expert who can provide you with the technical information, skills and experience you need to get the most out of your AD project. 

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