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| Methanogenesis and digestate stability of three wetland plants treated by anaerobic digestion |
| Received:January 02, 2018 |
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| KeyWord:anaerobic digestion;wetland plants;methanogenesis;digestate stability;thermogravimetric analysis |
| Author Name | Affiliation | | XIA Song | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China | | FU Jia-qi | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China | | FU Yin-xuan | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China | | YAN Heng | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China | | CHEN Xiao-ping | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China | | WU Jiu-jiu | Insititute of Energy, Jiangxi Academy of Sciences, Nanchang 330096, China |
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| Abstract: |
| To investigate the potential of wetland plants for energy utilization, the characteristics of methane production by anaerobic digestion of three wetland plants were evaluated using an automatic methane potential test system (AMPTS). The methanogenic process and stability of digestate were further simulated and analyzed. The results showed that cumulative methane production of three wetland plants, Pennisetum sp., Myriophyllum verticillatum, and Eichhornia crassipes, reached 166.5 mL·g-1 VS, 159.4 mL·g-1 VS, and 236.9 mL·g-1 VS under mesophilic conditions, respectively, which were 29.6%, 18.3%, and 39.9% higher than their respective production obtained under room temperature within a 30-day digestion cycle (P<0.01). Moreover, a faster methane production rate, a shorter digestion cycle, and a higher volatile solids (VS) removal rate were achieved under mesophilic conditions. The characteristics of mesophilic digestate of the three wetland plants were investigated by thermogravimetry-differential scanning calorimetry (TG-DSC). Three weight losses were observed around 100℃, 250~350℃, and 400~600℃, and the total weight loss rate decreased with digestion time. The DSC profiles for the three wetland plants were characterized by two exothermic peaks (300℃ and 400~550℃). The peak intensity in the low temperature zone (300℃) for the three plants decreased across the entire digestion period. In the high temperature zone (400~550℃), the peak intensity of M. verticillatum decreased, whereas the intensity of Pennisetum sp. and E. crassipes increased across the entire digestion period. In addition, a right shift of high temperature exothermic peaks was observed in Pennisetum sp. and E. crassipes. These changes in profiles of TG-DSC implied a higher conversion of organic matter and a greater stability of digestate across the entire digestion period. The Cheynoweth equation was used to fit the methanogenic process of Pennisetum sp., M. verticillatum, and E. crassipes. The correlation coefficients of the models proved to be more than 0.95, and the difference ratio was between the predicted and measured values at 1.98%, 0.82%, and 0.32%, respectively (P>0.05). Our results indicated that production of methane by anaerobic digestion is an effective way to utilize wetland plants and is conducive to solving the secondary pollution of constructed wetland plants. |
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