Effect of Fruit Waste Substrate Concentration and pH on Biogas Production by Mixed Culture

Biohydrogen refers to the production of hydrogen gas (H₂) from organic wastes through microorganisms for renewable and sustainable energy sources and recycling operations. The present research work aims for anaerobic digestion of organic waste, i.e. orange peel, core, and skeletons, as a remarkable feedstock for the production of biohydrogen and methane gas in a food-to-microorganism (F/M) ratio of 1–10 and initial substrate concentrations of 20–100 g total sugar/l. The kinetics of batch anaerobic digestion with a mixed culture of domestic wastewater inoculums and acid treatment was investigated under mesophilic (30 °C) and thermophilic (45–60 °C) circumstances. A favourable biohydrogen production has been observed by 27 g VS/l organic substrate mixture with 0.3 N H₂SO₄ acid pretreatment. The acid pretreatment of 0.2 N substrate improvises fermentation with a cumulative yield of 0.89 ml/g in 10–45% hydrogen volume. Peel fermentation resulted in total gas production at a rate of 3.5 ml STP/gram VS, whereas core fermentation yielded an H₂ volume ratio ranging from 5 to 32%. A maximized yield production of hydrogen was observed at 57 ml/mg of VS at F/M ratio of 7 after 44h of anaerobic ebullition under thermophilic circumstances. On the other hand, in mesophilic states, the hydrogen production rate was at a narrow F/M interval of 6 with a yield of 39 ml/mg of VS and 46% VS reduction. The uttermost specific progression rate of mixed culture was obtained at 40 g total sugar/l with a pH of 5.5 under thermophilic circumstances of 55 °C. Thus, the well-established experimental work illuminates a unique approach for H₂ generation under controlled anaerobic fermentation environments.