Optimization of anaerobic hydrogen and methane production from dairy processing waste using a two-stage digestion in induced bed reactors (IBR)

This study investigated the effects of pH, temperature and hydraulic retention time (HRT) and organic loading rate (OLR) on hydrogen production from dairy processing waste (DPW) in semi-continuous 60 L pilot induced bed reactors (IBR). Results show pH played a key role on hydrogen production and the optimal pH range was in 4.8-5.5. Digestion under thermophilic temperatures (60 °C) had advantages of gaining higher hydrogen yield and suppressing the growth of methanogens. The optimal OLR was 32.9 g-COD/l-d at HRT of 3 days. Under optimal conditions highest hydrogen yield was 160.7 ml/g-COD removed with 44.6% COD removal. Two-stage digestions demonstrated more energy gain from methane production and further COD removal. The overall gas production in two-stage digestion was 71.7 ml hydrogen and 61.0 ml methane per gram DPW COD. The overall COD removal under optimal conditions was 88.2%.