stove burner while plastic valves w

stove burner while plastic valves were installed to control the gas flow. The gas holder stores the biogas and allows the volume of biogas produced to be measured through the indirect measurement of a liquid column height. The digester and gas holder were designed, built and operated by the methods described in (Fountoulakis et al., 2008; Karki, 2002) with slight modifications. The composition of biogas (CH4 and CO2 contents) was determined using a gas chromatography (GC) (Hp 5890, Avondale, USA). Biogas composition measurement was taken two times a week in duplicate from each digester. A 100 ll gas tight
syringe was used to take biogas samples from the digesters head space after releasing the gas. This was followed by injecting the biogas sample into the GC (Owen et al., 1979; Zhang et al., 2006). The schematic of the setup is as shown in