Improvement of glycerol waste utilization by co-feedstock with palm oil decanter cake on biohydrogen fermentation

Co-feedstock of palm oil decanter cake with the both functions of substrate and microbial source in biogas fermentation was examined in this study. Decanter cake with the characteristic of high biodegradable organic contents and nutrient rich compositions is an attractive feedstock for biogas production. The various types of bacteria of the indigenous microbes from decanter cake resulted in the enhancement of the biogas productivity based on biogas potential production (H_max) and energy recovery including glycerol waste utilization. Decanter cake with 2% TS w v⁻¹ used as co-feedstock with varying glycerol waste concentration in the range of 7.5–45 g L⁻¹ were used for the biogas production in 0.5 L batch reactors under the condition of initial pH 7 and 37 °C. Comparative performance of the biogas production using combined decanter cake as co-feedstock and indigenous microbes and sole glycerol waste fermentation with anaerobic sludge as inocula was evaluated. Types of inoculum seeds displayed strong effect on the biogas compositions and glycerol waste utilization. CH₄ was the predominant biogas composition, while no H₂ was observed in the sole glycerol waste fermentation. H₂ production was predominantly detected in the combined decanter cake fermentation. The presence of the anaerobic sludge appeared to promote only methanogenesis resulting shorter fermentation period, lower glycerol waste utilization and biogas production potential (H_max). The increase of the glycerol waste concentration depressed CH₄ production and glycerol waste utilization. On the contrary, this work demonstrated the addition of decanter cake as co-feedstock and microbial source, containing hydrolytic and acedogenic bacteria, yielded a better performance in the biogas production and simulate glycerol waste utilization at the same time.