| Food waste yield increase with the economic growth and the improvement of people's living standard.If not treated properly,food waste will do harm to both environment and human health and be a waste of energy as well.Food waste proves to be an suitable substrate for anaerobic fermentation.Plenty of voliatle fatty aciods?VFAs?with a broad use can be produced through this process.For better use of VFAs,operational regulation can be used to incease the VFAs production efficiency.Energy crisis caused by increasing development and utilization of fossil fuels urges people to develop renewable energy.Biodiesel,as a kind of renewable and clean energy,has gradually attracted attention.Crude glycerin is one of the by-products in biodiesel production from food waste.The mixed fermentation of crude glycerin and food waste can change the C/N of substrate,adjust fermentation process and recycling crude glycerin.The purpose of this paper was to study the VFAs production in food waste anaerobic fermentation via semicontinuous experiment,to predict VFAs yield via modling,and to explore the effects of glycerol on the VFAs production via batch assays..A semi-continuous reactor was operated for anaerobic fermentation of food waste.During the experiment,in order to analyze anaerobic fermentation substrate degradation and VFAs production,parameters including s COD,ammonia nitrogen,soluble protein,soluble polysaccharide,VFAs and its composition were tested.The results indicated that VFAs production efficiency increased over time.The proportions of n-valeric acid and nbutyric acid were higher.And the proportions of n-valeric acid and n-butyric acid were 36.00%±2.63% and 24.35%±2.18%,respectively.After 5 days,the concentrations of ammonia nitrogen,soluble protein and soluble polysaccharide reached a balance,and the hydrolysis was generally stable.Based on the data collected from the semi-continuous reactor,dynamic relationships were established among s COD,ammonia nitrogen concentration,soluble protein concentration,soluble polysaccharide concentration and VFAs concentration.A model based on BP neural network was established and evaluated to predict the VFAs production from anaerobic fermentation of food waste.The results indicated that this model had certain accuracy and credibility to achieve a good predictive ability.This model could provide a reference for the industrial application of food waste anaerobic fermentation.Co-digestion of food waste and glycerol was studied in batch assays to explore the effect of glycerol on the biodegradation of substrates and VFAs production.When the C/N of substrate was 10.69/1?control group?,15/1,20/1 and 25/1,the total VFAs production of the batch experienment was 21719.34±2248.43 mg COD·L-1,29181.43±658.38 mg COD·L-1,29631.48±472.04 mg COD·L-1 and 32969.93±5598.73 mg COD·L-1,respectively.The total VFAs production of the three experimental group increased 34.36%,36.43% and 51.80% compared with the control group.The results showed that glycerol increased the C/N of the substrate,which was beneficial to the synthesis of hydrolases and promoted the hydrolysis.According to the changes in the VFAs production and composition,glycerol could affect the total VFAs production rate and components.Production of odd-numbered carbon VFAs such as propionic acid and n-valeric acid rather than n-butyric acid was enhanced by adding glycerin.This study provides a reference for the optimization of acidogenic fermentation from food waste and application and development of PHA production. |
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