Bioenergy generation and leachate treatment by anaerobic digestion of organic waste

Abstract

The organic fraction of MSW (municipal solid waste) amounts to over 40%, which becomes over 60% if the recycling is excluded in the estimation. Especially, food waste occupies over 25% of MSW, and becomes the main source of decay, odor and leachate in collection and transportation due to the high volatile solids (VS) and moisture content. Most food waste has been landfilled together with other wastes, resulting in various problems such as emanating odor, attracting vermin, emitting toxic gases, contaminating groundwater and wasting landfill capacity. Since landfilling of food waste will be prohibited in 2005, the research on its recycling technology is, therefore, a major field of waste management. This study was performed to assess the newly devised process, called MUlti-step Sequential batch Two-phase Anaerobic Composting (MUSTAC). The MUSTAC process was developed as an ideal method for treating organic waste. The configuration and the operating method of the process are suggested to enhance the performance and to simplify the operation based on the rate-limiting step approach. Firstly, the enhanced acidogenic fermentation of food waste was examined in a leaching bed by controlling fermentation constraints. The fermentation efficiency is affected by the fermentation constraints such as the biodegradability of substrate, the degrading capability of microorganisms and the environmental conditions. The key factors were, therefore, investigated to control the fermentation constraints, such as the effect of seed inoculation, The effect of adjusting dilution (D) rate and the effect of waste components. Acidogenic fermentation of food waste employing rumen microorganisms resulted in the enhanced efficiency (71.2%) as compared with that (59.8%) employing mesophilic acidogens. In addition, the fermentation efficiency increased from 71.2 to 82.0% by adjusting D rate from 3.0 to $1.0d^{-1}$ depending on the state of the fermentation. The main component ...