Effect of caffeine and saponin on anaerobic digestion of food waste

Abstract

Food waste is the single largest component of the waste stream by weight. In the present work, we attempted to study the effect of caffeine and saponin on anaerobic fermentation of food waste to examine their potential influence on biogas production at 8% total solids (TS) content. Addition of caffeine at 50, 100, and 150 ppm to the food waste on the first day resulted in biogas production in 24 hours which normally comes on 4 th day. The maximum biogas production of 408.5 ml/g TS was found at 100 ppm caffeine whereas 50 ppm and 150 ppm caffeine produced 359 ml and 336 ml in comparison with the control which showed 182 ml/g TS. This is the first study of effect of caffeine as stimulants in anaerobic environments. Addition of saponin had no beneficial effect; on the other hand, it inhibited the biogas production at 50, 100 and 150 ppm.