Research On The Methane Production And Pretreatment Of Tobacco Stalk

Tobacco stalk is an important economic crop widely planted in china,and the output accounts for 40%of the world's total tobacco production.A huge amount of tobacco stalk was abandoned directly or burned after the harvest of tobacco leaf.These treatment methods have brought enormous pollution risks to the environment.In contrast,anaerobic digestion(AD)is a more renewable and sustainable method,which can not only treat the waste,but also produce clean energy.In addition,the content of cellulose of tobacco stalk is in a considerable high range,which is preferred for AD.Therefore,this study systematically and comprehensively researches anaerobic digestion process and pretreatment of tobacco stalk.Firstly,the effect of nicotine on the methane production was been discussed and the results showed that the lower concentration of nicotine(?4%)had little effect on the methane production of glucose(P>0.05).But the nicotine at a concentration of 7%and 10%inhibited the anaerobic digestion of glucose,and the methane production decreased by 10.9%and 21.2%,respectively.This also proves that the nicotine content which were 0.076%,0.029%,0.015%of TS116,TS99,TS85 could be used as feedstock for anaerobic digestion.Central composite design(CCD)of response surface methodology(RSM)was used to determine the suitable feed to inoculum ratio(F/I)and organic loading(OL)of three kinds of tobacco stalks(TS116,TS99 and TS85)to optimize anaerobic digestion conditions.Results showed that the TS116 achieved the highest experimental methane yield(EMY)of 148.0 mL/g VS at F/I ration of 1.0 and OL of 20.1 g VS/L among the three kinds of tobacco stalks(129.1 mL/g VS of TS99,117.1 mL/g VS of TS85).So chose TS116 to carry out the follow-up researches,and F/I of 1 and OL of 20 g VS/L was set as the optimum anaerobic digestion conditions.Secondly,based on the results of RSM,6 kinds of different pretreatment methods were applied on TS116 to improve methane yield,including alkali hydrogen peroxide(AHP),NaOH,KOH,Ca(OH)2,HCl,and H2C2O4.Results showed that the AHP pretreatments and alkaline pretreatments could more efficiently improve the methane yield than acid pretreatments.The highest methane yield obtained was 350.7 mL/g VS from 7%AHP-treated TS116,which was 105.6%higher than untreated TS116,and the biodegradability(Bd)was 75.4%.The methane yield of 5%NaOH,7%KOH,3%Ca(OH)2,7%H2C2O4,5%HCl were 321.7 mL/g VS,309.7 mL/g VS,236.2 mL/g VS,206.5 mL/g,203.3 mL/g VS,respectively.All of them have significant improvements(p<0.05).At last,combining the conclusion above,this study carried out the anaerobic co-digestion of TS116,7%AHP-treated TS116 with pig,dairy,chicken manure at different ratios(5:0,4:1,3:2,2:3,1:4,0:5),respectively.Results showed that,pig manure was suitable for co-digestion with TS116,the optimum mixing ratio was 1:4(TS116:PM).The methane yield was 356.3 mL/g VS at this ratio.The co-digestion methane yield of 7%AHP-treated TS116 with pig manure at 1:4 was 397.2 mL/g VS,and showed synergetic effect.In summary,this study researched the anaerobic digestion performance of tobacco stalk systematically,and provided data reference for the utilization in future and theoretical basis for the practical application of tobacco stalk in AD process.