The Study Of Establishment And Rebalancing Acidification System In High Loading Corn Stover Anaerobic Digestion

It is of great significance for corn stover energy conversion and environmental protection through increasing organic loading of corn stover anaerobic digestion and maintaining stable biogas producing and anaerobic digestion system.This study was conducted with corn stover to be feedstock with mesophilic(37±1℃)and semi continuous anaerobic digestion.Starting with total solid(TS)was 8% initially,loading feedstock every 10 d and increasing TS gradually with 1% gradient was conducted to establish high loading corn stover anaerobic digestion system.TS would be replaced through adding different ratios of cattle manure(20%,30% and 40%)to make it restore producing biogas in acidification system,then preventing acidification and make sure the optimal cattle manure to corn stover in preventing acidification system.Utilizing 16 S r RNA sequencing technology to analyze bacteria and archaea diversities of optimal biogas producing biogas period,acidification period and biogas recovering period.The result showed that the TS methane production rate was 39.4 m L/g,when total solid was 8%,meanwhile the content of volatile fatty acid(VFA)was 1872.2 mg/L and p H value was 7.05.The TS methane production rate was highest,59.4 m L/g,when increasing TS to 13%,meanwhile the content of VFA was 2726.5 mg/L and p H value was 6.90.The system was acidified,when increasing TS to 15%,and biogas production was stopped on the 4th day.Meanwhile,the TS methane production rate was only 2.2 m L/g with highest VFA,11485.7 mg/L,and lowest p H value,5.13.The replacing volume of 30% cattle manure was the optimal biogas production,TS methane production rate was 29.2 m L/g with content of VFA,4722.7 mg/L,and p H was 6.71,Adjusting the ratios of cattle manure and corn stover which can prevent acidification 1:1 ratio of cattle manure to corn stover was the best after the optimal bioagas production stage of anaerobic digestion and before the critical point of acidificationThe predominant bacteria of optimal biogas production period,acidification period and recovering biogas period were the same in phylum level,they were Firmicutes(50.98%,16.84% and 48.01%),Chloroflexi(31.34%,29.74% and 9.32%)and Bacteroidete(7.86%,29.80% and 32.12%),respectively.Significant difference was found of different digestate in bacterial genus level.The predominant bacteria was Ruminofilibacter(14.32%)in optimal biogas production period.The predominant bacteria were Clostridium(25.72%)and Caproiciproducens(9.06%)in acidification period.The predominant bacteria were Prevotella(24.15%)and Ruminiclostridium(11.62%)in acidification period.The predominant of archaea in three periods’ digestate of phylum level were Euryarchaeota(52.84%,70.65% and 76.42%)and Bathyarchaeota(31.07%,19.48% and 12.83%,respectively.The predominant of archaea in three periods’ digestate of genus level were Methanosaeta(38.63%,31.19% and 23.79%),Methanobacterium(8.05%,31.27% and 36.46%)and Methanosarcina(1.23%,1.11% and 10.64%),respectively.The predominant of bacteria in three periods’ digestate of phylum level were the same,but with significant difference in abundance.The predominant of bacteria of genus level were different.There was no significant difference in archaeal phylum and genus level,but with significant abundance.A speculation can be made that the acidification process was significant correlated with microbial composition,Clostridium and Caproiciproducens in special.In conclusion,increasing TS gradually and establishing high loading corn stover anaerobic digestion system can confirm the critical point of acidification and the optimal volume of cattle manure loading about rebalancing acidification system.Replacing only corn stover through cattle manure loading cattle manure can prevent acidification and get the high-efficiency operating state after optimal biogas production period.Adding cattle manure suitably can recover acidification system and prevent acidizing.The variation of composition and abundance of bacteria and archaea in optimal period,acidification period and recovering producing biogas period was studied through high throughput sequencing technology.