Biohydrogen Production as a Clean Fuel by Acid and Alkaline Pretreated Mixed Culture During Glucose Fermentation

Background: Biohydrogen production from organic wastes is one of the most promising alternatives for sustainable, green energy production. Dark fermentative biohydrogen production is a complicated anaerobic process in the absence of sunlight. Objectives: The current study investigated the enrichment of biohydrogen-producing bacteria from anaerobic mixed culture by acid and alkaline pretreatment. Methods: Anaerobic sludge was extracted from a full-scale anaerobic sludge digester. In order to remove large particles and debris, the sludge was sieved and subjected to acid and alkaline pretreatment. Four strong acids including HCl, HNO3, H2SO4, and H3PO4 was used for acid pretreatment and tow mineral bases including NaOH and KOH for alkaline pretreatment. The pretreated sludge was fed to glass containers with a working volume of 400 mL and headspace of 100 mL. Results: HCl and H2SO4 as acid pretreatment agents produced more biohydrogen than the other agents. In case of HCl pretreatment, the volume of H2 gas was 133.6 mL, followed by H2SO4 (80.6 mL), KOH (72.5 mL), HNO3 (70.1 mL), H3PO4 (68.7 mL), and NaOH (59.8 mL). In the pretreatment methods, the solution pH and alkalinity were in the ranges of 4.8 to 6.9 and 2,400 to 3,800 mg/L, respectively. Conclusions: According to the results, pretreatment methods with acids, especially HCl, could be used for the enrichment of biohydrogen-producing bacteria from mixed cultures.