The reactor used in this study was

The reactor used in this study was a continuously stirred tank reactor (CSTR) with a volume of 1 L, magnetically stirred, and conducted in a semi-batch operation. The mesophilic conditions were maintained using a thermostatic bath at 37 °C (Fig. 1) [13, 14]. The volume of methane produced during the process was measured using 1.5 L Boyle–Mariotte tank full of water, which was connected to the reactor. To purify the biogas, the CO2 generated during the process was removed using a NaOH solution (6 N). The volume of methane produced was measured using the water displacement technique. This volume was corrected at standard temperature and pressure conditions (STP: 0 °C and 1 atm) [12].