Producing Biogas with Two-Stage Fermentation Process of High Total Solids Content Kitchen Wastes

Abstract

This paper inoculated kitchen waste with activated sludge and fresh cow dung to explore the acidification and fermentation separated two-stage fermentation biogas process, in order to get acclimation acidification bacteria and methanogenic bacteria, high total solids content (TS) fermentation process, reduce the hydraulic load and shorten the fermentation cycle. The physiochemical characteristics of kitchen waste were that TS is 22.9%,the volatile solids (VS) is 11.7%, initial pH value is 6. The biogas producing process was as follow: Adjusting the TS of kitchen waste to 11.5% ,with 10% inoculum quantity, fermented at 37 °C , monitoring and adjusting pH. There were two biogas producing peak , and biogas production cycle was 15 days. The two-stage fermentation biogas process was as follow: Acidized the material of 22.9%TS for 5 days, Feeding the acidized material at the ratio of 1/4 to the vigorous biogas reaction system, then pH reduced but the biogas production was normal. After 5 days, pH raised and the second batch of material could be added. Feeding materials to the acidification tank and fermentation tank continuously, which can gradually get good acclimation acidification bacteria and methanogenic bacteria. Refluxing the biogas to acidification tank and methane fermentation tank, which can mix the materials evenly, shorten the fermentation cycle, improve the efficiency of the acidification and biogas production.