2.2. Production of biogas
A laboratory scale plant was assembled for production and purification
of biogas. It contains a digester, collection chamber, gaspurification unit and gas storage system. The experimental setup for
the gas production and purification is presented in Fig. 1. The 0.2 m3
polypropylene digester tank (used as a reactor) with an air tight rubber
gasket was interconnected to the purification unit. Cafeteria, vegetable
and fruit wastes were cut into small pieces and were mixed in
equal proportion. A homogenous mixture was obtained, which was
diluted with tap water at 1:1 ratio. In order to optimize gas production,
feed stock was maintained to contain 8% of total solid. The
prepared raw materials were used as input charge for the production
of biogas in the digester tank. About 80% of the digester volume
was filled with the diluted organic waste. For better digestion, the
batch pH was maintained between 6.8 and 7.6 by adding lime (CaO).
Mesophilic batch digestion was conducted at 33 ± 2 °C temperature
under 30 days hydraulic retention time. Inside the digester, biogas
was generated from anaerobic decomposition of the input sample by
the action of various methanogenic microorganisms and bacteria. The
amount of biogas generated was monitored for 30 days.