초록
<P><B>Abstract</B></P> <P>This study aimed at maximizing the energy yields from food waste in a three-step conversion scheme coupling dark fermentation (DF), photofermentation (PF) and anaerobic digestion (AD). Continuous H<SUB>2</SUB> production was investigated over a period of nearly 200 days in a thermophilic semi-continuous DF process with no pH control. The highest H<SUB>2</SUB> yield of 121.45 ± 44.55 N L H<SUB>2</SUB>/kg VS was obtained at an organic loading rate of 2.5 kg VS/m<SUP>3</SUP>/d and a hydraulic retention time of 4 days. The DF effluents mainly contained volatile fatty acids (VFAs) and alcohols as metabolites and un-hydrolyzed solid residues. The supernatant, after separation, was used to recover H<SUB>2</SUB> in a PF using <I>Rhodobacter sphaeroides</I>. The solid residual fraction along with PF effluent was converted into methane by anaerobic digestion. By combining DF and PF, the H<SUB>2</SUB> yield from the food waste increased 1.75 fold. Moreover, by adding AD as a post treatment of the DF residue, the total energy yield was substantially increased to reach 5.55 MJ/kg VS<SUB>food waste</SUB> added, versus 3.55 MJ/kg VS<SUB>food waste</SUB> when applying solely AD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three step conversion of food waste to biohydrogen and methane is presented. </LI> <LI> Coupling of dark and photo fermentation (DF-PF) can increase biohydrogen yields. </LI> <LI> Anaerobic digestion (AD) can valorize DF-PF residues by conversion to methane. </LI> <LI> High energy yields and treatment of waste can be achieved by integrated DF-PF-AD. </LI> </UL> </P>