Biogas Production And Characteristics Of Maturity During Anaerobic Co-digestion Of Spent Mushroom Substrate And Dairy Manure Or Kitchen Waste

As the largest mushroom producing and consuming country in the world,the production of spent mushroom substrate(SMS)increases rapidly.SMS resource disposal become an important issue.The current disposal strategy of SMS is by burning,spreading on land,burying,composting with animal manure,or landfilling.There are still few studies on energy utilization.In this study,dairy manure(DM)and kitchen waste(SKW)were co-digested with SMS with different mixing ratios,respectively.The methane production and microbial community resulting from co-digestion were evaluated.(1)Batch test was conducted on SMS alone at 1%TS,3%TS,5%TS,respectively.Results showed that SMS is a suitable feedstock for anaerobic digestion.The highest methane yields were all obtaine at 1%TS of three kinds of SMS.The methane production and maturity increased as TS becomed lower.(2)The methane production obtained using different ratios(4:0,3:1,1:1,1:3,0:4),based on two total solids(TS),of SMS and DM as co-substrates in anaerobic digestion for biogas production were evaluated.Results of 3%TS was better than that of 5%TS.At 3%TS,the highest methane yield was obtained with 3:1 ratio of three kinds of SMS.While at 5%TS,the results showed differences among different kinds of SMS.The highest methane production was obtained with 3:1 and 1:1 ratio for the SMS of F.velutipes(SFv)and P.erygii var.tuoliensis(SPt),respectively.But for the SMS of P.eryngi(SPe),the results of co-digestion were no better than that of SMS mono-digestion.Positive synergistic effect was found in most co-digetsion of DM and SMS.Besides,the mono-digestion of SPt at 3%TS showed a strong cellulose decomposing ability.While the stronger hemicellulose decomposition of co-digetion implied that adding DM as a co-substrate can not only improve system buffering capacity but also speed up composting into humus.The main route of producing methane was tropic acid in co-digestions of SMS with DM.The bacterial community was similar at the phylum level in the samples of different SMS/DM reaction ratios.The phyla Firmicutes and Bcteroidetes were dominant in all treatments.Methanosaetaceae was shown to be the predominant methanogens present during the co-digestions.(3)The methane production obtained using different ratios(4:0,3:1,1:1,1:3,0:4),based on two total solids(TS),of SMS and SKW as co-substrates in anaerobic digestion for biogas production were evaluated.At 3%TS,the methane production decreased as the proportion of SMS increased.And the highest methane production of three kinds of SMS were all obtained with 1:3 ratio.At 5%TS,the co-digestions of 1:3 ratio were all failured.Specificly,3:1 ratio was better than other ratios for the SMS of SFv and SPt while 1:1 ratio was more suitable for the SMS of SPe.The concertration of VFAs at 5%TS was higher than that at 3%TS,indicating that the proportion of SKW over 50%would inhibit the process of methane production and the maturity,which resulted in the low maturity of system.The bacterial community was similar at the phylum level in the samples of different SMS/SKW reaction ratios.The phyla Firmicutes and Bcteroidetes were dominant in all treatments.