Study On The Effect Of Additives And Ammonia Alkali Optimization On Anaerobic Co-digestion Of Ensiled Maize Straw

The anaerobic co-digestion characteristics and system stability of ensiled maize straw(EMS)were studied when the mixing ratio of EMS and cattle manure total solids(TS)was 3:7 while the inoculum was30% at 37±1 ?.The mass fraction of 4.5% Ammonium Hydroxide(AH)and 4%Na OH Sodium Hydroxide(SH)was used as the optimization and improvement for EMS on biogas production and system stability.At the same time,the data of experimental were fitted and estimated by the Modified Gompertz equation and Logistic function,which provided some reference and basis for the industrialization application of anaerobic co-digestion of EMS.Studied degradation process of digestion under the condition of Thermostatic,arriving at the following main reviews:1.Comparison of anaerobic co-digestion of EMS and dry corn stalk(DC)The biogas production characteristics of EMS(named as ME while in experimental which ensiled with no additive)were similar to that of DC after 24 months of silage,the difference was less than 1%,the biogas production rate of VS(volatile solid)increased by about compared with that of DC group,and the methane production rate of VS increased by about 2.63%.2.The anaerobic co-digestion experiments of different EMS and cattle manure:(1)Same points: They have the smaller in gas production,the cumulative of methane for example.The acidity of EMS is so high while the initial p H is less than 4and the initial Volatile fatty acid(VFAs)concentration is between 12~17g/L.Both of them had a big lag phase period and lasts about 13~17d,accounting for about 23~30% in cycles.The stability of the system is poor,and there are still some fluctuations in p H in the late stage of the experiment with the frequent fluctuation of VFAs and the low conversion rate.(2)Difference from the experiment of biochemical methane potential(BMP),Modified Gompertz equation and Logistic function fitting,the best performance of anaerobic co-digestion experiment came from the group of FA(1% formic acid in EMS)as the max accumulative methane production is about 204.02~209.86 m L·g-1 in TS with the max methane production rate is about 10.20~10.22 ml·g-1·d-1 in TS but less lag phase period about 12~14d.3.Effect of AH optimization on anaerobic co-digestion of EMS(1)The experimental group was stable.The fluctuation from p H was small and recovery was fast.VFAs and ammonia nitrogen(NH4+-N)concentration could keep in the level of suit to digest.The digestion rate of chemicals oxygen demand(COD)was far greater than the group of EMS.(2)Index of each experimental group was significantly and there was not clear lag phase period at all.The fitting result can be obtained that each of the tow model had a poor performance in the group AH-PA(3% Pichia anomala in EMS)as the correlation coefficient was 0.7148 and 0.6903.For other groups,Logistic function had a better performance though the min fitting coefficient appear in group AH-FA(0.9788).The digest lag phase period was 5~6d which came from the group AH-LB(3% lactobacillus buchneri in EMS).(3)The BMP of EMS was reduced by the treatment of AH to some extent.The AHFA group had the largest decline as the cumulative of gas production decreased by 63.71%.While the smallest decline came from the AH-PA as the cumulative of gas(CH4)and the rate of gas in TS/VS were 17.24%,22.22%,17.24% and 3.05%respectively.4.Effect of SH optimization on anaerobic co-digestion of EMS(1)The system has similar performance in terms of stability,p H,VFAs,NH4+-N,COD,lag phase period and so on.(2)In addition to group SH-LB and SH-ME(each of the fitting coefficients were greater than 0.99)of the two models for the SH optimization was not ideal.For group SH-LB and SH-ME,Logistic function had a better performance and the biggest lag phase period came from the group SH-LB(about 5~7d).(3)Each data of group SH-CB(3% cellulose in EMS)was higher than that of the group CB,the rate of methane production in VS was the biggest promote which was about 28.30% higher than it.Part of the index from the group SH-FA,SH-ME and SHPA were increased but others were not.Both index of group SH-LB were lower than group LB particularly the rate of methane production in TS decreased largest which was about 33.40%.5.Comparison of the effects of AH and SH optimization on the BMP characteristics of EMS under the same conditions(1)Generality: Both of the two optimization methods can significantly neutralize the acidity of EMS raw materials and the stability and efficiency of anaerobic digestion system is improved.The utilization and conversion rate of EMS were accelerated significantly either while the test period was shortened at the same times.(2)Differentia: In addition to AH-CB,AH-FA and AH-LB,the average of methane volume fraction of AH was slightly larger than CB,FA and LB while the other indexes were far lower than those in EMS were.However,the SH optimization from SH was different because of different raw materials.(3)The fitting effects of the two models on the group AH-PA and SH-PA are unsatisfactory,and the fitting effect of the Logistic function overall is better than that of the Modified Gompertz equation.The Logistic function is more suitable for AH than SH in anaerobic co-digestion.