Anaerobic co-digestion of food waste with landfill leachate

Abstract

Anaerobic digestion (AD), which is considered to be a viable method of disposing of organic wastes, is a favorable technology to biologically convert organic waste into energy. Landfill leachate, a major organic waste stream, can be reliably treated through the AD process in which both pollution control and energy recovery can be achieved simultaneously. Food waste (FW) is an easily biodegradable substrate for AD with high carbohydrate, lipid, protein, and moderate moisture content. Although FW can be converted into useful bioenergy in the form of methane through the AD process, sole AD of FW has several challenges, including volatile fatty acids inhibition, trace elements deficiency, and poor digestate dewaterability. Compared to mono-digestion of these substrates, co-digestion of FW with landfill leachate provides better treatment performance and is expected to provide better nutrient balance and biogas production, since the high ammonia nitrogen concentration in landfill leachate could enhance the buffering ability of the AD process that ensures the stable operation of AD. Besides, landfill leachate having rich trace elements could improve the nutrient balance for AD bacteria. Co-digestion of FW with landfill leachate could promote refractory organics degradation. Moreover, the divalent cations in the leachate could improve the dewaterability of the digestate and facilitate the subsequent treatment of liquid and solid digestates. Co-digestion of FW with landfill leachate has the potential to greatly increase biogas yield owing to these synergistic effects. Hence, co-digestion of FW with landfill leachate can be considered as a feasible and promising approach.