Conly Hansen and Jianming Zhong
Dept. Utah State University, Logan, UT, 84322-8700, USA
This study investigated effects of pH, temperature, hydraulic retention time (HRT), and organic loading rate (OLR) on hydrogen production from food processing waste (FPW) using dark fermentation in semi-continuous 60 L pilot induced bed reactors (IBR). Results show pH played a key role on hydrogen production with optimal pH range of 4.8-5.5. Digestion under thermophilic temperatures (60 °C) had advantages of gaining higher hydrogen yield and suppressing growth of methanogens. The optimal OLR was 32.9 g-chemical oxygen demand (COD)/l d at 3 d HRT. Under optimal conditions highest hydrogen yield was 71.7 ml/g CODloaded with 44.6% COD removal. Two-stage digestions demonstrated more energy gain from methane and further COD removal. The overall gas production in two-stage digestion was 71.7 ml hydrogen and 61.0 ml methane g/DPW COD. The overall COD removal under optimal conditions was 88.2%. The Anaerobic Digestion Model No. 1 (ADM 1) was modified and implemented in software R to describe and correctly predict hydrogen production from FPW. Validation results show this model described reasonably well the dynamic behavior of hydrogen production in IBR. DNA-based studies to characterize IBR microbiology are underway and should facilitate efforts to refine and enhance reactor operations.