High-rate methane fermentation of the organic solid waste

Abstract

A study to develop anaerobic digestion alternatives for the resources recovery from organic solid wastes was performed. In order to evaluate applicability of anaerobic digestion for organic solid wastes, the effects of waste composition and particle size on the characteristics of anaerobic degradation were evaluated by methane conversion efficiency and kinetics using an anaerobic batch biodegradability test. The anaerobic degradation kinetics of organic wastes can be explained by the first order reaction model. The ultimate methane production for food wastes tested was over 0.32 L $CH_4$/g VS, higher than those of paper wastes, and they were severely affected by composition of the wastes. And, the degradation rate of the food wastes is faster than those of other tested wastes. Those imply that the anaerobic digestion of food wastes is a very attractive alternative for treatment of the waste. The anaerobic degradation rate was enhanced by particle size reduction, depending on substrate species, but for food wastes, it is considered to be a costly ineffective. Anaerobic toxicity assays to evaluate the effects of sodium ion on the anaerobic degradation of food wastes using an anaerobic batch reactor were performed for sodium ion concentrations whose concentration varies from 0.5g $Na^+$/L to 20 g $Na^+$/L. The inhibitory effects of sodium ion on the methane production can be observed by the retardation of methane production and the reduction of ultimate methane production. Different species of anaerobic microorganisms degrading food wastes showed different characteristics of acclimation and inhibitory effects according to the sodium ion concentration. The effects of sodium ion on the maximum methanation rate, the first order kinetic constant and the ultimate methane production can be properly evaluated by a generalized non-linear expression model, and that can be described by the uncompetitive inhibition model. The sodium ion concentration, $IC_50$, causing 50% in...