Pengchong Zhang

By Pengchong Zhang

Treating industrial wastes requires large amount of capital investment and also creates environmental concerns from several aspects. One of the techniques to reduce these concerns is anaerobic digestion. By applying anaerobic digestion technique, the organic waste from various industries could be removed and recovered to renewable energy, mostly in the form of biogas (methane); therefore, waste treatment process shifted from a cash negative process to an economic beneficial process. In this chapter, various kinds of industrial wastes were selected and descripted, followed by a gradually progressive order. The selected waste streams include paper mill wastes, brown grease, and corn ethanol thin stillage. Due to their dissimilar properties, the motivations of treating these wastes are also different. Paper mill effluents and solid wastes contain large portion of refractory or toxic chemicals and fibers; their bio-treatability, organic removal efficiency, and substrate utilization rate have been investigated and the results showed good anaerobic treatability. Brown grease is already well-known as a treatable substrate; therefore, the economic effort by using a high-rate anaerobic digester will be more important. For thin stillage, a systematic design of incorporated anaerobic digestion process was analyzed; the cost analysis was also conducted; and the possibility of using this technique as an add-on system was discussed.

Part of the book: Advances in Biofuels and Bioenergy

By Pengchong Zhang

Food wastes were mostly treated in landfills due to economic reasons, which create rich organic leachate and soil contamination risks. An alternative for food waste treatment is to use the anaerobic digestion technique to reduce the organic content, as well as to recover bioenergy in the form of biogas. In this chapter, a common type of food waste brown grease was selected and investigated using a pilot-scale high-rate completely mixed digester, and the digestibility, biogas production, and the impact of blending of liquid waste streams from a nearby pulp and paper mill were assessed. Using a pseudo-first-order rate law, the observed degradation constant was estimated to be 0.10–0.19 d−1 compared to 0.03–0.40 d−1 for other organic solids. These results demonstrate that brown grease is a readily digestible substrate that has excellent potential for energy recovery through anaerobic digestion.

Part of the book: Energy Systems and Environment