Feasibility of bio-hythane production by co-digesting skim latex serum (SLS) with palm oil mill effluent (POME) through two-phase anaerobic process

Hydrogenogenic batch fermentation without nutrients addition was investigated at different SLS: POME mixing ratios of 100:0, 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45,50:50, and 0:100 (Volatile Solid, VS basis) at initial organic concentrations of 21 and 7 g-VS/L. Satisfactory hydrogen yield of 84.5 ± 0.7 mL H2/g-VSadded was achieved from 7 g-VS/L batch having SLS: POME-VS mixing ratio of 55:45. Adding NaHCO3 3 g/L or 0.43 g-NaHCO3/g-VS) in the two-stage anaerobic system at 7 g-VS/L could provide sufficient buffering capacity. Hydrogenogenic effluent from 7 g-VS/L batch at SLS: POME mixing ratio of 55:45 (VS basis) could further generate rather high methane yield of 311.2 ± 8.0 mL- CH4/g-VSadded in themethanogenic stage.According to the experimental results, bio-hythane approximately 55.5 × 106 m3/year with 21% (V/V) of hydrogen, equivalent to51.0 × 106 l-gasoline could be produced potentially from 3.88 × 106 m3 of mixed SLS and POME through the two-stage anaerobic co-digestion.