The efficiencies and capacities of carbon conversion in fruit and vegetable waste two-phase anaerobic digestion: Ethanol-path vs. butyrate-path

Abstract

To rapidly treat and stably utilize great quantities of fruit and vegetable waste (FVW), the strategies in anaerobic digestion pattern have been constantly improved. In this work, the efficiencies and capacities of carbon conversion in different FVW anaerobic digestion systems were studied. Compared to butyrate-path (BD) two-phase and single-phase anaerobic digestion (SD), the ethanol-path two-phase anaerobic digestion (ED) system showed the highest rate of converting insoluble into soluble carbon formation (82.2%) and methane yield conversed from soluble carbon which is 0.14 gCOD_CH4 (gVSS d)^-1. It was also found that the coexistence of Bacillus and Methanococcus in the methanogenic phase maintained fatty acids and methane generation. The advantage of carbon conversion efficiency in ED can be elucidated from the highest acetification rate (704.10 mgCOD (L h)^-1) which means more converted acetate can be smoothly used for methane generation. Compared to methanogenesis converted from butyrate and propionate, the thermodynamic condition of methanogenesis converted from ethanol was more feasible. Also, the highest capacity of max methane production (197773.7 mL) of ED was simulated. ED might be an efficient and advantageous option for FVW methane digestion. Furthermore, comparison of acidogenic product and methane in conversion efficiency revealed that fatty acids should think as ideal anaerobic product rather than methane.

Keywords: Acidogenic product; Carbon conversion; Fruit & vegetable waste (FVW); Methane potential; Two-phase anaerobic digestion.