System Template 5: Biogas System

How It Works

This system supports two different User Interface technologies: a Pour Flush Toilet (U.4) or, if there is a demand for the urine to be used in agriculture, a Urine-Diverting Flush Toilet (U.6).

A Urinal (U.3) could additionally be used. The User Interface is directly connected to a Biogas Reactor (S.12, also known as an anaerobic digester) for Collection and Storage/ Treatment. If a Urine-Diverting Flush Toilet is installed (and/or a Urinal), it will be connected to a Storage Tank (S.1) for Urine collection.

Depending on the loading and design of the Biogas Reactor, a thin or thick digestate (Sludge or slurry) will be continuously discharged. Because of the high volume and weight of the material generated, the Sludge should be used onsite. In some circumstances, a very thin digestate (Effluent) can be discharged to a sewer (though this is not shown on the system template here).

Use and/or Disposal: Although the slurry has undergone anaerobic digestion, it is not pathogen free and should be used with caution, especially if there is no further treatment. Depending on how it is used, additional treatment may be required before application (e.g., in Planted Drying Beds, T.15).

It is nutrient-rich and makes a good fertilizer that can be applied in agriculture (D.5) or transported to a Surface Disposal or Storage site (D.12). The Biogas produced must be constantly used, and can be incinerated as a clean fuel for cooking or used for lighting (D.13). If the gas is not burned, it will accumulate in the tank and, with increasing pressure, will push out the slurry until the Biogas escapes to the atmosphere through the slurry outlet.

A Biogas Reactor can work with or without Urine. The advantage of diverting Urine from the reactor is that it can be used separately as a concentrated nutrient source without pathogen contamination. The Urine collected in the Storage Tank is ideally applied on local fields (D.2).

Conveyance: Stored Urine can be transported in Jerrycans or a Tank (C.1), or using a Motorized Emptying and Transport technology (C.3).