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

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The dimensions of the digester: 3 m (dia) x 9 m (height) Daily amount of waste to feed: 2000 kg/d 2. Preparation of correct feed mixture for dry anaerobic digestion The main purpose of this research was to prepare a correct feed mixture (in terms of C/N ratio and TS) for dry anaerobic digestion, which can reduce the problem of ammonia inhibition. To achieve that purpose, various feed mixtures were prepared, which consisted of different percentage of different types of waste (i.e. food waste, fruit and vegetable waste, waste paper and leaves). The detail of feed mixtures and their characteristics is given in Table B-2. Table B-2 Composition and Characteristics of Various Feed Mixtures Detail Unit Feedstock 1 Feedstock 2 Feedstock 3 Composition Food waste % FW a 42 40 45 Vegetable waste % FW 45 27 33 Fruit waste % FW 5 20 15 Leaf waste % FW 5 8 - Paper waste % FW 3 5 7 Characteristics Moisture % 79-84 75-85 81-86 TS (range) % 16-21 15-25 14-19 VS (range) %TS 79-90 80-90 84-88 C (avg.) %TS 51.30 52.10 51.20 TKN (avg.) %TS 1.92 1.63 1.61 C/N (avg.) - 26.72 31.96 31.80 Density (avg.) kg/m 3 1045 1000 1020 a Percentage based on fresh weight. Feedstock with C/N ratio 32 performed well and had 30% lesser ammonia accumulation than C/N ratio 27. Thus, feedstock with C/N ratio 32 is recommended for the proposed decentralized AD system, which can be prepared by mixing kitchen waste with 5-7% of waste paper as shown in Table B-2. 3. Calculation for methane or biogas yield Specific methane production = 320 L/kg VS (From pilot experiment, please see Table B-1) Methane production = volatile solids x specific methane production = 300 (kgVS/d) x 320 (L/kg VS) = 96000 L CH4/d or 96 m 3 CH4/d = 96 m 3 (CH4/d) x 100/48.12 (biogas/methane) = 200 m 3 biogas/d = 8.33 m 3 biogas/h 116
The flow rate of 0.569 m 3 biogas/h is required to convert the biogas into electricity for a gas engine of 1 kW (Prakash et al., 2012). Thus the flow rate of biogas produced from the proposed decentralized AD plant is sufficient to generate electricity. 4. Energy and electricity generation Energy balance of the pilot system has been calculated (Table B -3) based on the methodology given in Appendix E. Results of run 2 have been considered to calculate the electricity generation for real scale proposed decentralized AD plant. Table B-3 Surplus Energy of ITDAR During Various Runs of Experiment 2 Run Energy production (MJ/kg VS) Energy Consumption (MJ/kg VS) Feeding Heating and Shredding and Recirculation maintaining withdrawal thermophilic conditions Surplus energy (%) 1 20.60 1.29 0.28 2.09 4.149 62.02 2 18.21 1.16 0.26 1.68 2.76 67.77 3 15.98 1.21 0.27 1.18 2.50 67.75 Energy production: 18.21 MJ/kg VS (from pilot experiment 2, run 2, Table B-3) Energy available: 67% of produced (33% spent on operation of the plant) = 18.21 (MJ/kg VS) x 0.67 = 12.2 MJ/kg VS Input of proposed plant = 300 kg VS/d Energy produced = 12.2 (MJ/kg VS) x 300 (kg VS/d) = 3660 MJ/d = 3.66GJ/d We know that 1 GJ/d = 11.57 kW (1 J/s = 1 W) 3.66 GJ/d = 3.66 x 11.57 = 42.35 kW If efficiency of gas engine is 33% (Surroop and Mohee, 2012), then Electricity Generation = 42.35 x 33% = 13.97 kW Thus electricity of 14 kW will be generated by use of a 14 kW gas engine. Table B-4 Technical Detail and Availability of Gas Engine Description Specification Ranked power 14 kW (continuous operation) Voltage 400 V Current 27 A Approximate weight 800 kg Electrical efficiency 34.80% Biogas consumption < 0.5 m 3 /kWh Suppliers Address 1. EMAC International http://www.sino-cummins.com 2. http://www.alibaba.com/ Biogas flow rate for 1 kW gas engine: 0.569 m 3 /h (Prakash et al., 2012) 117
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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
Page 75 and 76: 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: Assumptions Size of the community:
Page 129 and 130: Area for 910 kg dry solids = 910 (k
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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