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Shubiao Wu

Effect of liquid digestate recirculation on biogas production and fermentation kinetics for anaerobic digestion of cattle manure

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  • Shubiao Wu
  • Jiaxi Li, China Agricultural University
  • ,
  • Wei Li, China Agricultural University
  • ,
  • Renjie Dong, China Agricultural University

The effect of recirculating the liquid fraction of digestate on the mesophilic anaerobic digestion of cattle manure was investigated using laboratory-scale continuous stirred tank reactors. The hydraulic retention time (HRT) of 40 d was employed. Recirculation was implemented after the anaerobic digestion process was stable at the organic loading rate of 3.0 g/(L·d). However, the recirculation eventually caused the accumulation of organic and inorganic substances, which led to the inhibition of hydrolysis and methanogenesis. The daily biogas yield was decreased by 22.4% when the liquid fraction of digestate was recirculated to substitute 50% of the tap water used for feedstock dilution. The concentrations of ammonia and volatile fatty acids did not reach the inhibitory levels. However, the accumulation of refractory organics, which were more pronounced in the recycling reactors, led to the decrease of methane production. According to the results of kinetic analysis, the microbial anabolism was promoted by the recirculation. The results indicate that choosing a proper recirculation rate and adopting reasonable pretreatment measures are indispensable to avoid the negative influence caused by the accumulation of potentially harmful substances. The proposed approach will lower the amount of generated effluents, and the product of anaerobic digestion with this method will contain high solid content, which will decrease the transportation costs and the storage capacity requirements.

TidsskriftNongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery
Sider (fra-til)241-246
Antal sider6
StatusUdgivet - 25 okt. 2015
Eksternt udgivetJa

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