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3.4.5 Methane potential of co-fermentation of SLS and POME

The CH 4 potential in the second phase used effluent achieved from the BHP test under
the optimal conditions as substrate, the highest cumulative methane and methane production
yield achieved from sole fermentation of POME which was used as substrate control was 433±6
mL CH 4 and 618±8 mL CH 4/g-VS added, respectively at the end of 27 days of fermentation
because its high lipid content when compared with other treatments (O-Thong et al., 2012; Luo
et al., 2011). Meanwhile, cumulative methane and methane production yield achieved from co-
digestion of SLS and POME was 293±7 mL CH 4 and 418±10 mL CH 4/g-VS added, respectively
which is 41% of methane theoretical yield (1014 mL CH 4/g-VS) (Batstone et al., 2002). Low
methane production yield achieved from co-digestion of SLS to POME as compared to sole
fermentation of POME due to SLS was a concentrated substrate with high concentrations of
nitrogen compounds and sulfate as shown in Table 3.1, corresponding to sole fermentation of

SLS (substrate control) with the lowest methane production yield was 230±10 mL CH 4/g-VS added
as shown in Fig. 3.6 and Fig. 3.7. The initial pH of all treatment ranged 7.06-7.55 and at the end
of fermentation the final pH increased to 7.47-7.79. The results indicate that VFA produced in H 2
production stage was converted to methane, corresponding to soluble metabolite products were
small amount in all treatment as shown in Table 3.10.

Fig. 3.6 Cumulative methane production achieved from the sequential methane production in

batch experiment at the end of the 27 days of fermentation.