Effect of pre-aeration and inoculum on the start-up of batch thermophilic anaerobic digestion of municipal solid waste |
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| Authors: | W Charles L Walker R Cord-Ruwisch |
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| Institution: | 1. College of Engineering, Nanjing Agricultural University, Nanjing, Jiangsu Province 210031, China;2. Department of Food Engineering, University of Agriculture, Faisalabad 38000, Pakistan;3. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China;1. Department of Molecular Biosciences and Bioengineering (MBBE), University of Hawai''i at Mānoa, 1955 East-West Road, Agricultural Science Building 218, Honolulu, HI 96822, USA;2. College of Agriculture, Forestry and Natural Resource Management (CAFNRM), University of Hawai''i at Hilo, 200 W. Kawili Street, Hilo, HI 96720, USA;1. Chemical Engineering Department, Universidad de Santiago de Chile, Ave. Lib. Bdo. O''Higgins, 3363, Santiago de Chile, Chile;2. Chemical and Environmental Engineering Department, Universidad Técnica Federico Santa María, Valparaíso, Chile;1. State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China;2. Research Center of Water Pollution Control Technology, Chinese Research Academy of Environment Sciences, Beijing 100012, China;3. School of Marine Science and Technology and Environment, Dalian Ocean University, Dalian, Liaoning 116032, China;4. Jilin Petrochemical Wastewater Treatment Plant, PetroChina Jilin Petrochemical Company, Jilin 132000, China;1. Acqua & Sole s.r.l., Manzola Fornace, Corteolona, PV, Italy;2. ENEA, Italian National Agency for New Technologies, Energy and the Environment, Water Management Section, Bologna, Italy;3. Department of Industrial Engineering, University of Padova, via Marzolo 9, 35131 Padova, Italy |
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| Abstract: | In this study, a short pre-aeration step was investigated as pre-treatment for thermophilic anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). It was found that pre-aeration of 48 h generated enough biological heat to increase the temperature of bulk OFMSW to 60 °C. This was sufficient self-heating of the bulk OFMSW for the start-up of thermophilic anaerobic digestion without the need for an external heat source. Pre-aeration also reduced excess easily degradable organic compounds in OFMSW, which were the common cause of acidification during the start-up of the batch system. Careful consideration however must be taken to avoid over aeration as this consumes substrate, which would otherwise be available to methanogens to produce biogas. To accelerate methane production and volatile solids destruction, the anaerobic digestion in this study was operated as a wet process with the anaerobic liquid recycled through the OFMSW. Appropriate anaerobic liquid inoculum was found to be particularly beneficial. It provided high buffer capacity as well as suitable microbial inoculum. As a result, acidification during start-up was kept to a minimum. With volatile fatty acids (VFAs-acetate in particular) and H2 accumulation typical of hydrolysis and fermentation of the easily degradable substrates during start-up, inoculum with high numbers of hydrogenotrophic methanogens was critical to not only maximise CH4 production but also reduce H2 partial pressure in the system to allow VFAs degradation. In a lab-scale bioreactor, the combined pre-aeration and wet thermophilic anaerobic digestion was able to stabilise the OFMSW within a period of only 12 days. The stabilised inert residual material can be used as a soil amendment product. |
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