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Effects of microbial pretreatment on ethanol-methane co-conversion efficiency of sorghum straw
Received:September 15, 2021  
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KeyWord:composite microbial system MC1;sorghum straw;ethanol;methane;energy yield
Author NameAffiliationE-mail
CAO Yanzhuan College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
SU Wan College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
FAN Wenhua College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
BU Yushan College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
LIU Fenwu College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
NIE Du College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China  
LI Jiajia Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin 300191, China aepi_ljj@126.com 
CUI Zongjun College of Agronomy, China Agricultural University, Beijing 100193, China  
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Abstract:
      The production and utilization of biofuels can reduce human dependence on fossil energy. Straw is rich in lignocellulose and is an important raw material for biofuel production. However, its structure is compact and complex, and thus it is difficult to biodegrade. Therefore, pretreatment is needed to improve the energy conversion efficiency. In this study, the degradation characteristics of sorghum straw under different treatment times were analyzed by pretreating sorghum straw with MC1, and the bioenergy conversion efficiency was compared between methane fermentation only and combined fermentation of ethanol and methane. The results showed that MC1 could effectively degrade sorghum straw, and the weight loss rate of straw pretreated for 5 d reached 39.64%. The concentrations of soluble chemical oxygen demand and volatile fatty acids in the hydrolysate reached maximum levels of 8.10 g·L-1 and 2.92 g·L-1, respectively. When the pretreated straw produced methane only, the methane yield of the 5 d pretreatment system was the highest, reaching 180.68 mL·g-1 VS, which was 60.56% higher than that of untreated straw. When ethanol-methane co-production and fermentation of pretreated straw was conducted, the ethanol and methane yields of the 5 d straw pretreatment system were the highest at 79.18 g·kg-1 VS and 239.50 mL·g-1 VS, respectively, which were 173.78% and 138.74% higher than those of untreated straw, respectively. The total energy yield was 11 947.04 kJ·kg-1 VS, which was 2.45 times higher than that of untreated straw. The total energy yield of ethanol-methane co-fermentation of sorghum straw was approximately 8.21%~65.06% higher than that of methane fermentation only, which further indicates that MC1 pretreatment and ethanol-methane co-fermentation are effective means to improve the energy conversion efficiency of sorghum straw.