Automatic process control for stable bio-hythane production in two-phase thermophilic anaerobic digestion of food waste

The paper reports the results of a long term (310 days) pilot-scale trial where food waste as sole substrate was treated in a two-phase thermophilic anaerobic digestion process. This was optimized for concurrent hydrogen and methane production. First phase's optimization for hydrogen production was obtained recirculating the effluent coming from the methanogenic phase and without the addition of external chemicals. A drawback of such approach is the recirculation of ammonia into the first phase reactor for hydrogen production with possibility of consequent inhibition.