Preparation Of Methane From Anaerobic Digestion Of Vinegar Residues

Vinegar residues(VR)is one of the main by-products in industrial vinegar production process,and the annual production of VR in China exceeds 3 million tons.VR mainly consists of wheat bran,rice husk,and etc.VR is a typical organic waste since the content of lignocellulose and crude protein are accounting for more than 70%of the total weight of dry VR.Anaerobic digestion can realize the reduction and resourceful treatment of organic wastes,however,the biodegradability of VR is low.In this work,a series of studies were conducted to improve the anaerobic digestion performance of VR.Alkaline hydrogen peroxide(AHP)pretreatment was employed to improve the methane production of VR.T he effects of hydrogen peroxide concentration,pretreatment temperature,and pretreatment time on the anaerobic digestion performance of VR were studied using single factor experiment.The results showed at H2O2 concentration of.4%,pretreatment temperature of 40?,and pretreatment time of 12h,the highest methane yield of 302.0 mL/gVS was obtained with a biodegradability of 70.0%.On contrary,the untreated VR has shown the maximum methane yield of 195.6 mL/gVS and biodegradability of 43.8%,hence,the pretreatment increased the methane production of VR by 54.4%.Analysis of lignincellulose structure and content before and after pretreatment showed that lignin was effectively removed,hemicellulose was degraded,and the availability of cellulose was increased.Anaerobic co-digestion of VR with chicken manure(CM),pig manure(PM),cow dung(CD)in different mixing ratio was studied.The results showed that in the co-digestion of VR mixing with CM,the largest SEI of 16.8%was obtained at the mixing ratio of VR:CM=1:3,in addition,methane yield at the mixing ratio of VR:CM=1:3 and 1:4 reached 294.0 and 294.1 mL/gVS,respectively,which was higher than the methane yield of VR and CM as a single substrate.In the co-digestion of VR and PM,the largest SEI of 12.2%was obtained at the mixing ratio of VR:PM=1:3.Methane yield of336.2 and 337.7 mL/gVS at the mixing ratio of VR:PM=1:3 and 1:4 was close to the methane yield of PM as a single substrate,although methane yield at all the mixing ratios was lower than methane yield of PM as a single substrate.In the co-digestion of VR and CD,the largest SEI of 18.8%was obtained at the mixing ratio of VR:CD=1:3,meanwhile,the highest cumulative methane yield of 258.9 mL/gVS was reached at the mixing ratio of VR:CM=1:3,higher than methane yield of VR and PM as a single substrate.Methane yield of co-digestion of pretreated VR mixing with dung was higher than methane yield of co-digestion of VR mixing with dung,however,the latter possesses higher SEI.Finally,the application of VR in semi-continuous AD was studied.Semi-continuous system with VR,PVR,PM,VR:PM=1:3,and PVR:PM=1:3 as substrates were operated at different organic loading rate(OLR)of 1,2,3,and 5 gVS/(L·d).As the results showed,in the semi-continuous AD systems,pretreatment of VR prompted AD efficiency of VR but not improved the co-digestion of VR and PM.In addition,the methane yield of co-digestion of VR mixing PM was higher than the methane yield of VR and PM as a single substrate.This study has attempted to enhance the methane production performance of vinegar residue by laying a good foundation for its effective utilization in future.