This study investigates the biogas production from chicken manure at different organic loading rates (OLRs), in a
mesophilic-thermophilic two stage anaerobic system. The system was operated on semi continuous mode under
different OLRs [1.9 g volatile solids (VS)/L$d e 4.7 g VS/L$d] and total solid (TS) contents (3.0e8.25%). It was observed that
the anaerobic bacteria acclimatized to high total ammonia nitrogen concentration (>3000 mg/L) originated as a result of
the degradation of chicken manure. High volatile fatty acid concentrations were tolerated by the system due to high pH
in the reactors. The maximum average biogas production rate was found as 554 mL/g VSfeed while feeding 2.2 g VS/Ld
(2.3% VS e 3.8% TS) to the system. Average methane content of produced biogas was 74% during the study.
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