Anaerobic fermentation of hybridPennisetummixed with fruit and vegetable wastes to produce volatile fatty acids

The production of volatile fatty acids (VFAs)viaanaerobic fermentation is a new technology that provides a high-value utilization of biomass. This work used hybridPennisetum(HP) and fruit and vegetable waste (FVW) as raw materials to investigate the influence of different ratios of HP to FVW on the production of VFAs under different methanogenic inhibition conditions. It has been shown that both alkaline and neutral conditions (using methanogenic inhibitors), could generate higher acid yields than acidic conditions. Under initial alkaline conditions, mono-fermentation of HP and FVW could obtain maximum VFA yields of 596 +/- 22 mg g(-1)VS and 626 +/- 7 mg g(-1)VS, which were higher than those obtained under neutral conditions. In contrast, there was no remarkable difference in VFA yield between alkaline and neutral conditions when co-fermentation of HP and FVW was carried out. The VFA yields decreased significantly with the process of co-fermentation. The maximum VFA yields were decreased by 33.2% and 21.9% when HP was fermented with 15% and 30% of FVW, respectively. There was a clear difference in the composition of VFAs obtained under different initial conditions. The maximum selectivity was achieved under alkaline conditions, where the acetate content reached more than 85%. This study brings a theoretical basis for optimizing the anaerobic fermentation process of lignocellulose to produce VFAs

Liquid–Liquid Extraction of Volatile Fatty Acids from Anaerobic Acidification Broth Using Ionic Liquids and Cosolvent

Promoting efficiency of liquid–liquid extraction at a high pH is a main challenge for the recovery of volatile fatty acids (VFAs) from organic wastes. In this study, the extraction efficiency of VFAs from artificial solution and acidification fermentation broth of kitchen wastes using ionic liquids (ILs) was assessed at high pH. The effect of ILs addition ratio in diluent, volumetric solvent to feed ratio (S/F) on extraction efficiency were investigated. The solvent consists of [P666,14][Cl] (IL101) and dodecane was found to be the promising solvent for VFA extraction at pH 6.0, especially for butyric acid. The IL-101 ratio in dodecane and S/F was significant factors for the liquid–liquid extraction of VFAs. In general, a higher IL-101 ratio and S/F can promote the extraction efficiency of single VFAs. As a result, the maximum extraction rate of acetic acid (38.4–49.9%) and butyric acid (66.0–92.1%) from different VFA concentration solutions was observed at 10% IL-101 in dodecane and S/F = 2/1. The solvent was also effective in different types of real fermentation broth of kitchen wastes. The maximum extraction rate and selectivity of butyric acid was 60.2%/70.5% in butyric acid type broth and 74.6%/62.7% in mixture acid type broth