The kinetics of anaerobic digestion of cattail by rumen microbes in a modified upflow anaerobic sludge blanket (UASB) reactor was systematically analyzed in this study. The Monod and first-order equations were combined to develop kinetic models to describe the substrate degradation, microbial growth and product formation. At an influent cattail concentration (volatile solids) of 12.1 g/L, hydraulic retention time of 0.75 day and solids retention time of 1.0-4.0 days, the concentration of reducing sugars was negligible, compared to the hydrolyzed cattail, indicating that the lignocellulosic hydrolysis was the rate-limiting step in the fermentation. The rate constant (k) of cattail degradation, true microbial growth yield (YEG) and the maintenance coefficient (m) were calculated as 1.50 day-1, 0.11 g/g and 0.103 g/(g h), respectively. The measured and estimated substrate degradation, microbial growth and product formation were in good agreement.
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