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Pretreatment of lignocellulocics-rich cattail by rumen microorganisms to enhance anaerobic digestion performance

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  077075.(doi:10.13031/2013.22873)
Authors:   Zhenhu Hu, Zhiyou Wen
Keywords:   Anaerobic digestion; Kinetics; Lignocellulose; Rumen microorganisms; Upflow anaerobic sludge blanket (UASB)

Cattail is a lignocellulosic aquatic plant and has been extensively used in constructed wetlands for the treatment of wastewater and contaminated soil. It is also a renewable biomass resource containing 34.8% cellulose, 22.6% hemicellulose and 10.5% lignin. Anaerobic digestion of cattail could reduce disposal of this waste material and produce renewable energy. However, due to low recalcitrant nature of cellulosic nature, the digestibility of cattail was very low in conventional digesters. The organisms contained in animal rumen are one of highest efficient ecosystems to digest lignocellulose. In this study, rumen microorganisms collected from a fistulated goat were used as inoculums in batch and continuous artificial rumen reactors to improve cattail digestibility. In batch culture, anaerobic degradation tests were carried out in 250-ml serum bottles and a degradation efficiency of 60% with volatile fatty acid yield of 0.35 g/g dry cattail was obtained in 120 h fermentation at 39oC. In the continuous culture, a modified upflow anaerobic sludge blanket (UASB) was applied as artificial rumen reactor to improve the digestibility. At operation conditions of temperature 39±1oC, pH 6.8±0.2, hydraulic retention time 0.75 day, and solids retention time 1 day to 4 day, the modified UASB achieved a 60-65% of substrate degradation efficiency with 11.1 g COD products/L-d at loading rate of 15 VS/L-d. The reaction rate constant (k) of cattail degradation, true microbial growth yield (Y), and the maintenance coefficient (m) in the continuous reactor were evaluated as 1.50 day-1, 0.11 g/g, 0.103 g/g h, respectively. These results suggest that the application of artificial rumen reactor could effectively improve cattail digestibility.

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