A novel bioethanol and biogas coupling fermentation system integrated with the pretreatment of a
cellulolytic microbial consortium was proposed to treat cassava distillage. In the present study, 8 batches
of ethanol fermentation integrated with 7 batches of biogas fermentation were successively proceeded.
The recycled water after two-stage of anaerobic digestion was reused for raw material mixing in the later
7 batches of ethanol fermentation, whereas only tap water was used in the first batch. It was found the
ethanol yield, starch utilization ratio, fermentation time can be kept steady at about 12.6%(v/v), 90% and
48 h respectively during the recycling process, which were very close to those of the conventional
process using tap water. The organic substrates, volatile fatty acids, total and ammonia nitrogen reached
steady states after 2-5 batches of recycling, while the total ion and alkalinity revealed a little decrease
tendency with the increment of the recycling batches. Further, the total methane yield and methane
producing velocity of each recycling batch in the proposed coupling system could reach 180e206 L and
40e45 L CH4 L1 d1 (litres of methane generate per litre of reactor volume per day) respectively, which
was 16.1e32.9% and 25e40.6% higher than those of the original one. In addition, the total mass yield
obtained by the combination in the proposed coupling system was 317 g ethanol plus 68.7 g methane/kg
cassava, and 8.3% higher energy was generated compared with the original system. In conclusion, the
insertion of a biological pretreatment step into the proposed coupling system revealed obvious superiorities
and applicable potential.
A novel bioethanol and biogas coupling fermentation system integrated with the pretreatment of acellulolytic microbial consortium was proposed to treat cassava distillage. In the present study, 8 batchesof ethanol fermentation integrated with 7 batches of biogas fermentation were successively proceeded.The recycled water after two-stage of anaerobic digestion was reused for raw material mixing in the later7 batches of ethanol fermentation, whereas only tap water was used in the first batch. It was found theethanol yield, starch utilization ratio, fermentation time can be kept steady at about 12.6%(v/v), 90% and48 h respectively during the recycling process, which were very close to those of the conventionalprocess using tap water. The organic substrates, volatile fatty acids, total and ammonia nitrogen reachedsteady states after 2-5 batches of recycling, while the total ion and alkalinity revealed a little decreasetendency with the increment of the recycling batches. Further, the total methane yield and methaneproducing velocity of each recycling batch in the proposed coupling system could reach 180e206 L and40e45 L CH4 L1 d1 (litres of methane generate per litre of reactor volume per day) respectively, whichwas 16.1e32.9% and 25e40.6% higher than those of the original one. In addition, the total mass yieldobtained by the combination in the proposed coupling system was 317 g ethanol plus 68.7 g methane/kgcassava, and 8.3% higher energy was generated compared with the original system. In conclusion, the
insertion of a biological pretreatment step into the proposed coupling system revealed obvious superiorities
and applicable potential.
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