What is the typical detention time in a mesophilic digester?

In a mesophilic digester, the typical detention time is around 15 to 30 days, with a duration of approximately 20 to 28 days commonly cited. This timeframe is influenced by the optimal temperature range for mesophilic bacteria, which is generally between 30°C to 38°C (86°F to 100°F). During this period, the bacteria effectively break down organic material in the digester, facilitating the production of biogas and reducing the volume of waste solids.

The choice of 28 days aligns well with industry standards and practices, being at the upper end of the typical range. An extended detention time allows for improved digestion efficiency, leading to better biogas production and thorough stabilization of the sludge. While options that suggest 14 days or 21 days may be within range for certain conditions or specific operational preferences, they generally do not represent the common detention times seen in conventional mesophilic digestion processes. The option of 35 days would likely be excessively prolonged for mesophilic digestion, as it could lead to inefficiencies or operational challenges.