dry anaerobic digestion of municipal solid waste and digestate ...

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Biogas flow rate for 14 kW gas engine: 0.569 x 14 = 7.96 m 3 /h. This flow rate can be supplied by the proposed system, as it has flow rate of 8.33 m 3 /h. The detail of the commercially available gas engine is given in the Table B-4. 5. Use of the produced biogas The produced biogas can be used for various purposes like cooking, lighting and electricity production. The extent of use of the produced biogas for various purposes has been given in the Table B-5. Table B-5 Use of Produced Biogas (8.33 M 3 /H) for Various Purposes Purpose of use Specifications 3 Biogas flow required (m 3 Number of uses at /h) a time Stove burners 10 cm 0.28 30 Mantle Lamps 60 watts equivalent 0.195 42 House electricity 1 1000 watt/house 2 0.569 15 1 Electricity consumption of a house in US and Australia is 900-1100 watt (Elert, 2003) 2 For 1000 watt power production 3 Prakash et al., (2012) 6. Technical details of digestate management Digestate withdrawn from the reactor will not be stored because storage causes emission of GHGs as found from the results of this study (please refer to sections 4.4.2(i) and 4.4.3 (i). As the C/N ratio of digestate is within safe range to be applied on agricultural land (please refer to Figure 4.16 and Table 4.4), therefore, it will be sent to use for agricultural purposes. But before sending, its weight will be reduced by dewatering for easy management. Technical details of dewatering have been given below. i) Design of sand drying bed for dewatering digestate from proposed system Sand drying bed will be used to dewater digestate. The advantages of sand drying bed are low cost and simple. Quantity of digestate: 1400 kg/d Solid content of raw digestate: 6.5% Dewatering time: 10 days Depth of digestate layer on bed: 20 cm Calculation for area of sand drying bed Area of sand drying bed can be calculated from the loading of dry solids. Typical dry solids loading: 120 kg dry solids/m 2 -yr (Tchobanoglous et al., 2003) For a drying time of 10 d: 120/365 x 10 = 3.28 kg dry solids/m 2 Thus area needed for 3.28 kg dry solids = 1 m 2 Digestate produced as dry solids from proposed system = 1400 (kg/d) x 10 d x 6.5% dry solids = 910 kg dry solids 118
Area for 910 kg dry solids = 910 (kg dry solids)/3.28 (kg dry solids/m 2 ) = 277 m 2 Standard dimensions of drying beds are 6 m (wide) x 6 to 30 m (long) Therefore, 3 drying beds with dimensions of 6 m (wide) x 16 m (long) will be constructed to fulfill the digestate dewatering requirement of proposed system. Other considerations -Starting from the bottom to top, the bed will consist of 15 cm coarse gravel layer and 7.5 cm thick layer each of medium gravel, fine gravel and coarse sand. At the top, there will be a 15-25 cm layer of sand. -Digestate will be placed on bed in 20 cm layer. -The bed will be equipped with lateral drainage lines under it, which will consist of perforated 15 cm plastic pipes spaced 2 m apart and sloped at 2 percent. ii) Calculation for reduction of weight (%) by digestate dewatering Total amount of raw digestate: 1400 kg/d Solid content of raw digestate: 6.5% Solid content of dewatered digestate: 50% Leachate solid content: 2.0% TS in raw plant residues or digestate = 1400 * 0.065 = 91 kg Total weight of dewatered residues = X Total weight of leachate = Y We know that, X + Y = 1400 kg or X = 1400 – Y Eq. (i) Weight of TS added = Weight of TS removed or 91 = 0.50 *X + 0.02 * Y or 91 – 0.02Y = 0.5X or X = (91 – 0.02Y)/0.5 = X Eq. (ii) Comparing Eq. (i) and (ii), we have X = 131 kg Y = 1269 kg Weight reduction = (1400 - 131) * 100 = 90.6 % 1400 7. Size of the pump The size of the pump used in pilot-scale ITDAR is AE1N-200. The number 200 means theoretical delivery of the pump is 200 L/min. But in practice, its delivery (flow rate) was observed as 25 L/min probably due to viscosity of the reactor material. The pump head 119
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DRY ANAEROBIC DIGESTION OF MUNICIPA
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Abstract Global solid waste generat
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2.9 Characteristics of Digestates 3
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List of Tables Table Title Page 2.1
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4.20 Layout of conceptual decentral
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1.1 Background Chapter 1 Introducti
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The specific objectives of this res
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scale plants of the two processes i
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acetogens play their part to run th
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In dry anaerobic digestion, recycli
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process is inhibited and at that po
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eported, which increased with time,
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acids and increased downfall of pat
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performance of a poorly mixed (1 rp
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conventional low-solid system at th
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supply of the nutrients missing in
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2.6.2 Single-stage continuous syste
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single stage systems are DRANCO, Va
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of the solid content around 23% TS
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Substrate Feed TS (%) Reactor Type
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Second is that it has a high water
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2.9 Characteristics of Digestates D
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For instance, Mumme et al., (2010)
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Comparison of liquid and solid dige
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2.10 Management Aspects of Anaerobi
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Figure 2.11 Changing parameters dur
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amount of anaerobic fermentation re
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3.1 Inoculum and Simulations of Was
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ed pump, water circulating jacket,
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the reactor was increased from 35°
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parts (wt/wt bas is) of digestate c
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Sand drying bed (SDB) is simple, ea
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3.4.4 Estimation of GHG emissions i
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d) Calculation methods i) CH4 emiss
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Table 3.5 Analytical Methods for Va
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Biogas production 100X (NmL) Specif
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(i.e. 5.2 and 3.04 respectively, pl
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getting affected with the presence
Page 77 and 78: feedstock 2 is considered as a sudd
Page 79 and 80: 8.0) at most of the above said time
Page 81 and 82: Table 4.2 Surplus Energy of ITDAR D
Page 83 and 84: VFA 100 X (mg/L) VFA/Alk ratio 200
Page 85 and 86: the VFA concentration increased to
Page 87 and 88: The increase in GPR was almost line
Page 89 and 90: Based on our results, the best oper
Page 91 and 92: Based on this property of digestate
Page 93 and 94: Table 4.5. With curing of digestate
Page 95 and 96: application (after curing) in CH 4
Page 97 and 98: digestion, etc. Moreover, mixing of
Page 99 and 100: Figure 4.20 Layout of conceptual de
Page 101 and 102: Chapter 5 Conclusions and Recommend
Page 103 and 104: 5.2 Recommendations Following are t
Page 105 and 106: References Abdullahi, Y. A., Akunna
Page 107 and 108: Cengel, Y.A. (2003). Heat Transfer
Page 109 and 110: Forster-Carneiro, T., Pérez, M., R
Page 111 and 112: Kaparaju, P., Buendia, I., Ellegaar
Page 113 and 114: Liu, C., Yuan, X., Zeng, G., Li, W.
Page 115 and 116: Paavola, T. and Rintala, J. (2008).
Page 117 and 118: Stroot, P. G., McMahon, K. D., Mack
Page 119 and 120: Zeshan, Karthikeyan, O. P. and Visv
Page 121 and 122: Fruit and vegetable Waste Closer to
Page 123 and 124: Figure A-5 Sand drying bed for dewa
Page 125 and 126: Assumptions Size of the community:
Page 127: The flow rate of 0.569 m 3 biogas/h
Page 131 and 132: = 280 m 3 /d x 0.000717 tons/m 3 (D
Page 133 and 134: Table C-1 Operational Parameters of
Page 135 and 136: Run Time GPR % CO2 % CH4 Methane Yi
Page 137 and 138: Appendix D Data of Phase II Pilot E
Page 139 and 140: Table D-3 Characteristics of Feed a
Page 141 and 142: Methodology Methodology for for Ene
Page 143 and 144: Q = Heat transfer rate or heat loss
Page 145: Calculation of GHG Emission Potenti
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