High-rate methane fermentation of lipid-rich food wastes by a high-solids co-digestion process

This paper presents an experimental study on anaerobic degradation of lipids-rich food wastes by using the high solids co-digestion process. The experiments were conducted under mesophilic (35 degrees C) and thermophilic (55 degrees C) condition, respectively, by using a semi-continuous flow completely mixed reactor. The influent TS level was controlled at around 10%, while the hydraulic retention time (HRT) was changed from 15 days to 7.5 days. The lipids (fats or oil and grease) content in the influent TS was changed from 8% to 40% by adding salad oil (vegetable) and lard (animal) to the food wastes. The result of this study showed that the food wastes containing high lipids content was effectively degraded by the high solids co-digestion process and over 85% of lipid was degraded to biogas with 60-65% of methane. In addition, thermophilic methane fermentation was more effective for reducing lipids and had more higher loading capacity compared with mesophilic condition.