Anaerobic Digestion And Biological Hydrogen Production From Food Origin Wastes In The Presence Of Aged Refuse

The quantity of food origin wastes is increasing dramatically in China cities due to the habits of Chinese and their food structures. According to the local regulations, food origin wastes cannot be used as feedstuff for livestock as it contains hazardous bacteria and virus. Anaerobic digestion is considered to be a favorable option for the effective treatment of the wastes so that methane gas and fertilizer can be produced while the wastes are stabilized. Traditionally, only methane is obtained. Biological hydrogen production from the wastes is highlighted in world using anaerobic digestion.In this work, experiments at bench and pilot scale were well conducted for food origin wastes to determine the optimum operating conditions to maximize the biogas output. Apart from that, the influences of biogas fluid from food wastes digestion on germination and sprout growth of familiar plant seeds were also investigated. The seeds used in tests were the seeds of rice- 4512, rice- 1750, wheat and cucumber- Jinyou No.1. The results showed that anaerobic digestion was an effective and promising technology for food origin wastes treatment. Further, the primary research was performed on bio-hydrogen production from food wastes for first time in China, from which some favorable harvests were acquired involved in bio-hydrogen process such as the influences of porous matter addition, aged refuse inoculums, and so on.First of all, the food origin wastes were characterized with chemical composition, dehydration behavior and acidification processing. The average water content, VS, C/N, C/P, C/Ca in the wastes was determined to be about 85%, 89%TS, 21.6, 202.8, 34.3, respectively. Plentiful microelements and little poisonous matters in the wastes would benefit for the growth of anaerobic microorganisms. It was also found that the wastes were quite difficult to be dehydrated and readily to be biologically acidified with negligible biogas production.The bench scale experiments were conducted aiming to quest for the feasibility of the anaerobic digestion for food origin wastes and find out the digestion conditions preparing for pilot scale experiments. The optimum ratios of sludge to waste food, water contents, organic load, temperature, etc., were explored in a single-phase or two-phase anaerobic digestor. The results indicated that water content should be controlled to over 90% and inoculation rate of 80% (sludge) so that anaerobic digestion can start and run successfully with a methane content of 50～55% in biogas. Meanwhile, an excellent mixing in the digestion system and a steady temperature profile was also required.