Soluble products and predicted H2 yield under different initial pH conditions.
| Parameters | Initial pH conditions | ||||
|---|---|---|---|---|---|
| Uncontrolled | pH 4.0 | pH 5.0 | pH 6.0 | pH 7.0 | |
| Ethanol (mmol) | 41.74 | 40.65 | 30 | 35.43 | 38.04 |
| Acetate (mmol) | 71.67 | 125 | 160.3 | 99.83 | 232.17 |
| Butyrate (mmol) | 24.32 | 23.51 | 22.97 | 80.95 | 135.23 |
| Propionate (mmol) | 14.77 | 43.29 | 109.32 | 121.93 | 45.0 |
| Predicted H2 production (Hp) (mmol)a | 233.7 | 337.7 | 252.6 | 397 | 651.7 |
| Observed H2 production (Ho) (mmol) | 0.8 | 13.7 | 58.3 | 128.3 | 160.1 |
| Ho/Hp (%)b | 0.3 | 4.1 | 23.1 | 32.3 | 24.5 |
a
Based on eqn (2)–(4), assuming that production of 1 mol of ethanol accompany 1 mol of H2 production, and 1 mol of acetate and butyrate production accompany 2 mol of H2 production.
b
The ratio of observed H2 production and predicted H2 production.