Co-Digestion of Lignocellulosic Wastes with Food Waste for Sustainable Biogas Production

Abstract

Lignocellulosic waste (LW) and food waste (FW) have great potential for biomethane production. The recalcitrant nature of LW limits its use in anaerobic processes. Without pretreatment, it is difficult to utilize LW at higher organic loading rates (OLRs) through an anaerobic process. Therefore, pretreatment is a compulsory step for efficient utilization (i.e., at higher OLRs) of LW. There are various techniques of pretreatment of LW, and every method has its own advantages and disadvantages and generally makes the process expansive. Pretreatment of LW can change the biomass structure by removing lignin, increasing the surface area, and decreasing the crystalline nature and length of the polymer chain. On the other hand, FW is readily digestible biomass and can be utilized at a comparatively higher organic loading rate than that of LW. Although mono-anaerobic digestion of FW at higher organic loading rates leads to the accumulation of higher volatile fatty acids, the process becomes unstable. This chapter provides state-of-the-art knowledge on the current status of mono-anaerobic digestion of LW and FW for sustainable biogas production, limitations such as pretreatment, low organic loading rates, higher hydraulic retention time, low buffering capacity, and higher accumulation of volatile fatty acids. Besides, the advantages of co-anaerobic digestion of LW with FW over mono-digestion of LW and FW, the technological advancements being made are also discussed.KeywordsLignocellulosic wasteFood wastePretreatmentMono-anaerobic digestionCo-digestion