Anaerobic hydrogen production from unhydrolyzed mushroom farm waste by indigenous microbiota.

The cultivation of mushrooms generates large amounts of waste polypropylene bags stuffed with wood flour and bacterial nutrients that makes the mushroom waste (MW) a potential feedstock for anaerobic bioH2 fermentation. MW indigenous bacteria were enriched using thermophilic temperature (55°C) for use as the seed inoculum without any external seeding. The peak hydrogen production rate (6.84 mmol H2/L-d) was obtained with cultivation pH 8 and substrate concentration of 60 g MW/L in batch fermentation. Hydrogen production yield (HY) is pH and substrate concentration dependent with an HY decline occurring at pH and substrate concentration increasing from pH 8 to 10 and 60 to 80 g MW/L, respectively. The fermentation bioH2 production from MW is in an acetate-type metabolic path.

Co-fermentation of water hyacinth and beverage wastewater in powder and pellet form for hydrogen production.

Hydrogen (H2) production potential of water hyacinth (WH) and beverage wastewater (BW) mixture in powder and pellet form at various combination ratios were evaluated. Batch co-fermentation results showed peak biogas production of 105.5 mL and H2 production of 55.6 mL at the combination ratio of 1.6 g WH and 2.4 g BW in pellet form. With the same ratio in pellet form, the maximum H2 production rate 542 mL H2/L-d, maximum specific H2 production rate 869 mL H2/g VSS-d and H2 yield 13.65 mL/g feedstock were obtained, and were 88, 88 and 34% higher than its powder form. The predominant soluble metabolite was acetate in the concentration of 1059-2639 mg COD/L (40-79% of total metabolites) in most runs during co-fermentation of mixed feedstock. Carbon-to-nitrogen ratio and the physical form of the combined feedstock are essential criteria for optimum H2 production. Co-fermentation also alleviates the waste disposal problem of the industries.

Acid-base enrichment enhances anaerobic hydrogen production process.

This study offers a novel and quick enrichment technology that can be used as a preliminary method to obtain a hydrogen-producing species from the biological sludge produced by wastewater treatment. The influences of acid-base enrichment (by sludge pH adjustment) on the anaerobic hydrogen-producing micro-organisms were investigated using serum bottle assays. The enrichment pH values were controlled at 3, 4, 5, 7, 10, 11 and 12 with 1 N hydrochloric acid and 1 N sodium hydroxide. For each enrichment pH, the cultivation pH values were controlled at 5, 6 and 7. Based on the experimental results, hydrogen accumulation from sludge with acid or base enrichment is higher than that of the control. The hydrogen-production potential of the sludge with acid or base enrichment is 200 and 333 times enhanced, compared with the control, when the enrichment pH is 10 and 3, respectively. The enhancement is due to a shortening of the micro-organisms' lag-time which occurs at a proper cultivation-pH level.