Recovery of lactic acid and other organic acids from food waste ethanol fermentation stillage: Feasibility and effects of substrates

Recycling ethanol fermentation stillage from food waste could help to resolve the pollution problems, but it would lead to the accumulation of lactic acid (LA), which had a negative effect on ethanol fermentation. In this study, bipolar membrane electrodialysis was used to recover LA as well as other fatty acids in the stillage, and the corresponding parameters that affected this process were investigated. Pretreatment via centrifugation and ultrafiltration reduced the turbidity successfully. Experiments on simulated and real stillage showed that organic acids such as formic acid and acetic acid had a slight effect on the separation of LA, but the existence of chloride ions could form strong anion competition with lactate ions. Simulation experiments with sodium chloride reduced the recovery of LA from 98% to 92%. The recovery rate of LA from real stillage could reach 71.2%. After electrodialysis, the stillage can be reused in ethanol fermentation, the fermentation time was shortened to 24 h, and the ethanol yield increased.