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| Effect of Pre-hydrolysis Time on Energy Consumption during Mechanical Size Reduction of Vegetable Wastes |
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| KeyWord:vegetable waste, pretreatment, pre-hydrolysis time, mechanical size reduction, energy consumption |
| Author Name | Affiliation | | SHAO Li-ming | Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China
2.Centre for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of P.R. China（MOHURD）, Shanghai 200092, China | | PENG Wei | Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China | | QIU Wei-jian | Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China | | HE Pin-jing | Institute of Waste Treatment and Reclamation, Tongji University, Shanghai 200092, China
2.Centre for the Technology Research and Training on Household Waste in Small Towns & Rural Area, Ministry of Housing and Urban-Rural Development of P.R. China（MOHURD）, Shanghai 200092, China |
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| Abstract: |
| Mechanical size reduction could improve anaerobic digestion efficiency of vegetable wastes, but might increase energy consumption. An experiment was designed to examine energy consumption of mechanical size-reduction of vegetable wastes after pre-hydrolysis by steeping the wastes in swill（initial pH=8） for different times（1 h, 2 h, 4 h, 8 h）. A knife grid size reduction device and a universal test machine were used to measure the energy consumption during size reduction of the pretreated vegetable wastes. After pre-hydrolysis for 1 h, 2 h, 4 h and 8 h, the maximum load of size reduction of vegetable wastes decreased by 0.07%, 4.85%, 16.28%, 12.55%, and the mass-based energy consumption reduced by -12.12%, 19.56%, 22.67% and 20.19%, respectively, as compared to the untreated control. There were no significant differences in the mass-based energy consumption and the maximum load of vegetable wastes between 4 h and 8 h of pre-hydrolysis, suggesting that it is unnecessary or uneconomical to extend pre-hydrolysis time over 4 h. The total contents of cellulose, hemicellulose and lignin in the wastes decreased by 10.99%, 11.88%, 23.61% at 1 h, 4 h and 8 h of pre-hydrolysis, respectively, with cellulose decreasing most. The hydrolysate pH decreased from 8.12 at the control to 7.31 at the 8 h pre-hydrolysis; TOC slightly increased from initial 984 mg·L-1 to 1009 mg·L-1 during the first two hours of pre-hydrolysis, and then decreased to 600 mg·L-1 at 8 h pre-hydrolysis. Component analysis showed that reduced energy consumption by pre-hydrolysis mainly resulted from weakened structural strength of plant tissues by imbibited water. |
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