Serum bottles had a total volume of 160 mL and a useful volume of
100 mL. The concentration of microalgal biomass after jar test was
23.8 g COD/L and 20.1 g COD/L corresponding to 21.0 and 25.0 g
microalgal biomass/bottle for Ecotan and Tanfloc, respectively. Following
that, inoculum was added to each trial (42 g VS/bottle) and bottles
were filled with distilled water to reach the useful volume (100 mL). Afterwards,
bottles were flushed with helium gas, sealed with butyl rubber
stoppers and incubated at 35 °C until biogas production ceased.
Biogas production was periodically determined by measuring the pressure
increase in the headspace volume with an electronic manometer
(Greisinger GMH 3151). After each measurement gas was released
until atmospheric pressure. Samples from the headspace volume were
taken every 2–3 days to determine biogas composition (CH4/CO2) by
gas chromatography (GC Trace, Thermo, Finnigan) following the procedure
described by [18].