Additives Enhancement Of Bio-hydrogen Production From Food Wastes

Food wastes have not been allowed for the uses as livestock feeds, and their safe treatment has been received great attention. Among the options for the wastes treatment, anaerobic digestion is considered environmentally-friendly and cost-effective. In this work, additives enhancement for bio-hydrogen production from the food wastes was explored, taking advantage of their high organic contents and biodegradability.Pretreatment means such as acid and alkaline adjustments for the inocluated sludge aiming for the promotion of bio-hydrogen production. It was found that acid and alkaline soaking of inoculated sludge could effectively eliminate the hydrogen-consuming bacteria and enrich hydrogen-producing bacteria. The maximum hydrogen productive rates were determined to be 14.9 and 17 mL/g VS respectively, nearly 15 times over the controlled tests, at an inoculation rate 40%, moisture content 90% and temperature 36℃, and soak pH 4 and 12.Alkaline additives such as detergents, silicates, sodium carbonate were added to the food wastes anaerobic digestion system to enhance bio-hydrogen production. Single-factor test indicated that the maximum hydrogen volumetric concentrations and productive rate of 51.78% and 117.4 mL/gVS can be obtained at the optimum conditions of 20% alkaline additive over dry weight of food wastes used, 30% inoculation rate, 90% moisture content and 36℃.Metallic Fe prersence in the digestion system can play an active role on hydrogrn production. When its doses were 6, 10 and 20% of dry weight of food wastes, the maximum hydrogen volumetric concentrations were 48.22, 41.82 and 41.67% and hydrogen productive rates were 74.2, 61.7 and 86.6 mL/g VS repectively, nearly 1.40, 1.15 and 1.61 times over that of the blank test （53.8 mL/g VS）. The addition of Fe₂（SO₄）₃ obviously prohibited the production of hydrogen.Yeast extract was a source of organic nitrogen. When the doses were 10, 20 and 30% of dry weight of food wastes, the maximum hydrogen productive rate can reach 57.4, 71.9 and 104.9 mL/g VS respectively, nearly 1.11, 1.40 and 2.03 times over that of the blank test （51.5 mL/g VS）.Alkaline additive addition can effectively accelerate hydrogen production while prohibit the production of methane. In the presence of alkaline additive, the maximum hydrogen productive rate of food wastes, rice, cabbage and eggs were 240.0, 53.0, 3.34 and 20.0 times, with negligible methane production, over those of controlled test without the additives with large amount of methane evolution.