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mL H 2 and 38.8±0.8 mL H 2, respectively as showed in Fig. 3.1, at the same time, cumulative
hydrogen production obtained from individual fermentations of SLS and POME with initial
organic concentration of 21 g-VS added/L were 21.5±0.9 mL H 2 and 1.3±0.2 mL H 2, respectively
(Fig. 3.2). Nevertheless, less than one day lag phase and the stationary phase had been reached at
th
the 4 day’s fermentation of all mixing ratio of both initial organic loads. Low hydrogen
production yield achieved from individual fermentations of SLS and POME with initial organic
concentration of 21 g-VS added/L (13.9±0.4 mL H 2/g-VS added and 0.6±0.1 mL H 2/g-VS added,
respectively) when compared to individual fermentations of SLS and POME with initial organic
concentration of 7 g-VS added/L were 28.8±7.0 mL H 2/g-VS added and 158.4±3.3 mL H 2/g-VS added,
respectively. The hydrogen potential of individual fermentations of SLS and POME with initial
organic concentration of 21 g-VS added/L decreased due to SLS was a concentrate substrate with
high concentrations of ammonia, sulfate and also low pH, similarly high concentration of oil and
grease and also low pH in POME, which could potentially inhibit or overload the process and
lead to decrease in biodegradability (O-Thong et al., 2012).

In case of co-digestion, when the POME composition in the fermentation broth was
increased, the hydrogen concentration, cumulative hydrogen and hydrogen production yield
increased. The best results of hydrogen production with initial organic concentration of 7 g-
VS added/L achieved at the mixing ratio of SLS to POME at 50:50 %v/v with the highest hydrogen
concentration, cumulative hydrogen and hydrogen production yield were 29.4±0.1%, 31.0±0.5
mL H 2 and 85.7±4.9 mL H 2/g-VS added (Fig. 3.3), respectively possibly correlates to existing
appropriate C/N ratio around 15. On the other hand, the optimal mixing ratio of SLS to POME
under the initial organic concentration of 21 g-VS added/L was 65:35 %v/v with the hydrogen
production yield was 36.8±0.8 mL H 2/g-VS added. The possible reason for high hydrogen
production yield was achieved due to the inhibitants content in the SLS was diluted and lipid
content in the POME fraction was still low as well as increasing in C/N ratio in the mixture
around 12. It should be noted that the hydrogen production yield obtained from sucrose control
with initial concentration of 7 g-VS added/L was 321.1±10.5 mL H 2/g-COD added which is 64% of
the theoretical biohydrogen production yield (498 mL H 2/g-COD added) (Kongjan et al., 2011).
Although, the hydrogen production yield achieved from SLS: POME mixing ratio of 50:50 %v/v
was different significant with the hydrogen production yield achieved from SLS: POME mixing
ratio of 55:45 %v/v with P ≤ 0.05 which was analyzed by using t-Test: Two-Sample Assuming
Unequal Variances. In the present study, however, SLS was chosen as the main substrate and
POME was chosen as a co-substrate. Thus, we wish to utilize a large proportion of SLS in the
mixture along with high in hydrogen production yield. The resulted shows that a relatively high
hydrogen production yield was achieved from SLS: POME mixing ratio of 55:45 %v/v of
71.8±1.7 mL H 2/g-VS added was obtained. Therefore, in this work should be chosen the optimal
mixing ratio of SLS to POME to generate both biohydrogen and biomethane was 55:45 %v/v.

Co-digestion of SLS with POME resulted in better than individual fermentation of SLS
2-
because inhibitants in SLS include, NH 3, SO 4 , and ZnO/TMTD were diluted and C/N ratio in