Effects of Surfactants on the Anaerobic Digestion of Food Waste

To solve the bottleneck of low degradation rate and low biogas yield in anaerobic digestion of food waste, the addition of anionic surfactant sodium N-lauroylsarcosinate (SN) and nonionic surfactant primary alcohol ethoxylate (AEO) were proposed. The results showed that both surfactants could promote the methane production and facilitate the degradation of food waste. The highest methane yield per mass of volatile solid was obtained in 0.1 g/L AEO (497.14 mL) and 1 g/L SN (445.51 mL), which was improved by 92% and 72% compared with the control group. While with the increase of surfactant concentration, methane yield was decreased due to negative effect caused by the surfactant. This corresponded with the variation of pH, total volatile fatty acids (TVFAs), and soluble chemical oxygen demand (SCOD). The microbial community analysis showed that the relative abundance of methanobacterium increased while the relative abundance of methanosaeta decreased after the addition of surfactant. Meanwhile, the methane production pathway was shifted from codominance of hydrogenotrophic and aceticlastic methanogens to predominance by hydrogenotrophic methanogens in the groups with low concentration of AEO and SN.