Table 1.
Reactors' operation at steady state conditions before and after H2 addition.
| Mesophilic | Thermophilic | |||
|---|---|---|---|---|
| Pre H2 | Post H2 | Pre H2 | Post H2 | |
| Temperature (°C) | 35 ± 1 | 35 ± 1 | 55 ± 1 | 55 ± 1 |
| CH4 yield (mL/gVS) | 111 ± 24 | 168 ± 21 | 249 ± 27 | 359 ± 22 |
| Biogas composition (%) | ||||
| CH4 | 69.7 ± 0.3 | 88.9 ± 2.4 | 67.1 ± 0.8 | 85.1 ± 3.7 |
| CO2 | 30.3 ± 0.3 | 8.8 ± 3.2 | 32.9 ± 0.9 | 6.6 ± 0.9 |
| H2 | 0 | 2.3 ± 1.8 | 0 | 8.3 ± 3.6 |
| H2 consumption efficiency (%) | 0 | 98.8 ± 1.2 | 0 | 92.4 ± 3.3 |
| pH | 7.73 ± 0.15 | 8.17 ± 0.13 | 7.89 ± 0.17 | 8.49 ± 0.04 |
| VFA (mg/L) | 90.10 ± 49.23 | 155.94 ± 31.94 | 284.76 ± 168.24 | 381.41 ± 73.59 |
| Acetate (mg/L) | 61.90 ± 8.20 | 143.60 ± 39.51 | 236.34 ± 169.47 | 320.55 ± 58.34 |
| Propionate (mg/L) | 1.48 ± 0.33 | 3.30 ± 2.66 | 7.87 ± 7.66 | 42.27 ± 12.89 |
| iso-butyrate (mg/L) | 0.02 ± 0.07 | 0.20 ± 0.29 | 1.99 ± 0.65 | 1.05 ± 1.53 |
| Butyrate (mg/L) | 2.38 ± 0.84 | 1.16 ± 1.26 | 4.40 ± 1.95 | 1.52 ± 1.65 |
| iso-valerate (mg/L) | 0.09 ± 0.19 | / | 1.40 ± 1.24 | 1.13 ± 1.67 |
| Valerate (mg/L) | 0.92 ± 1.75 | 3.95 ± 9.24 | 0.84 ± 1.39 | 14.52 ± 18.79 |
| n-hexanoate (mg/L) | 23.32 ± 44.20 | 0.11 ± 0.33 | 31.91 ± 57.16 | 0.36 ± 0.66 |