2.2. Description of experimental setup
A stainless steel cylindrical digester was used as shown in Fig. 1.
The total volume of the reactor was about 90 L with a working volume
of 50 L. Mechanical stirring was provided by the rotation of
blades at 10.5 rpm around a horizontal axis powered by a 250W
electric motor. The motor was automatically activated for 15 min
every 4 h.
The digester was equipped with an internal temperature sensor.
It was heated from its external surface using an electrical tape in
order to maintain a constant temperature of 35 ± 1 C inside the digester
during its operation (optimal range of temperature for mesophilic
microorganisms).
A 50 25 gastight window allowed the introduction and sampling
of waste from the top of the reactor. After each load/unloading
operation, the digester was flushed with nitrogen gas to
remove oxygen.
The biogas production was measured continuously using a
drum-type gas meter (range of 0.1–30.0 l/h). The gas meter was
equipped with a pulse generator to transfer the data to a computer.
Biogas was regularly sampled for analysis through a sampling port
sealed with a septum (Fig. 1)