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

More documents

Recommendations

Info

Concentration of VFA and pH (Figure 4.9 and 4.10) are reverse of each other. A low pH supports the production of VFA (acidogenic activity), whic h in turn suppresses VFA consumption (methanogenic activity). This could be explained by our results also. iii) VFA to Alkalinity ratio (VFA/Alk ratio) VFA/Alk ratio is a good indicator of digester functioning. With OLR of 4.55 kg VS/m 3 /d, this parameter remained between 0.35-0.45 for most of the time (Figure 4.11). This is a good range of VFA/Alk ratio for a working digester. But at OLR 6.4 kg VS/m 3 /d, the average value of VFA/Alk ratio increased to 0.53, which is still acceptable for an operating digester. The detailed data is provided in Appendix D, Table D-1. However, at OLR of 8.5 kg VS/m 3 /d, VFA/Alk ratio increased to very harmful range (0.67 -0.78), because at VFA/Alk ratio of 0.8, significant pH reduction and digester failure happen (Khanal, 2008). The trend of VFA/Alk ratio almost followed the trend of VFA concentration (Figure 4.10), except at the beginning (day 54), where VFA concentration increased but VFA/Alk ratio did not follow it. It was because the system had high buffering capacity or alkalinity. Hence, rise in VFA concentration did not show any adverse effect on this ratio and hence system performance. VFA/Alk ratio 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 OLR 4.55 OLR 6.4 OLR 8.5 51 71 91 111 131 151 Time (days) Figure 4.11 VFA/Alk ratio in ITDAR during continuous loading 4.3.3 Effect of organic loading rate on performance parameters of ITDAR i) Gas production rate Gas production rate (GPR) increased in OLR 6.4 and 8.5 kg VS/m 3 /d with an average value of 6.37 and 7.55 L/Lreactor vol./d respectively as compared to OLR 4.55, where it was 5.01 L/Lreactor vol./d. Figure 4.12 shows biogas production rate of ITDAR as L/Lreactor vol./d during different stages of continuous loading phase. The biogas contained 47-49% methane in all the runs (variation is not significant, Appendix D, Table D-2), therefore, the trend of methane production rate for three OLRs was also similar to GPR, i.e., 2.4, 3.07 and 3.6 L/Lreactor vol./d respectively. It can be noted that at the end of OLR 4.55 and 6.4 kg VS/m 3 /d, the GPR becomes stable. This is related with stable pH and VFA concentration of the system at the mentioned time. 76
The increase in GPR was almost linear with increase in OLR during first two runs. But, during run 3 (i.e. OLR 8.5 kg VS/m 3 /d), the GPR did not increase with the same rate as that of OLR. This could be explained by drastic increase in VFA/Alk ratio (o r drop in alkalinity) during that run. However, this effect of overloading could be alleviated by further acclimatizing the reactor under those conditions. ii) VS removal and Specific methane production (SMP) The VS removal was the highest in OLR 4.55 kg VS/m 3 /d. Thus, in terms of digestate quality, the best results on kg VS basis were shown at OLR of 4.55 kg VS/m 3 /d as shown in Table 4.3 and Appendix D, Table D-2. These results are similar to those obtained by Montero et al., (2008). They obtained VS rem oval of 80% in a thermophilic system operating at OLR of 4.42-7.50 kg VS/m 3 /d and 25-30% TS. The VS removal decreased as OLR was increased. GPR (L/Lreactor vol./d) 9 8 7 6 5 4 3 2 OLR 4.55 OLR 6.4 OLR 8.5 51 71 91 111 131 151 Time (days) Figure 4.12 Gas production rate of ITDAR during different OLRs The highest methane production per unit weight of volatile solids added (also called specific methane production, SMP) occurred at OLR of 4.55 kg VS/m 3 /d (330 L CH 4/kg VS added) whereas it was 20% lower for OLR 8.50 kg VS/m 3 /d. However, methane production by all the runs of this study (provided in Appendix D, Table D-2) is in line with the methane yield values found in literature. Table 4.3 Percentage of VS Removal and Specific Methane Production in ITDAR OLR (kg VS/m 3 VS Inlet VS Outlet VS Loss SMP /d) (kg VS) (kg VS) (%) (L CH4/kg VS) 4.55 121.60 26.86 77.90 330 6.40 116.90 28.66 75.48 320 8.50 62.95 20.70 67.00 266 The SMP reported by various authors through dry anaerobic digestion of OFMSW at thermophilic conditions is in the range of 230-340 L CH4/kg VS added ( Gallert and Winter, 1997; Pavan et al., 2000; Montero et al., 2008; Bolzonella et al., 2003). Similarly, SMP reported for a mixture of maize silage and barley straw under thermophilic dry anaerobic digestion was 182 L CH4/kg VS added (Mumme et al., 2010). 77
Page 1 and 2:
DRY ANAEROBIC DIGESTION OF MUNICIPA
Page 3 and 4:
Abstract Global solid waste generat
Page 5 and 6:
2.9 Characteristics of Digestates 3
Page 7 and 8:
List of Tables Table Title Page 2.1
Page 9 and 10:
4.20 Layout of conceptual decentral
Page 11 and 12:
1.1 Background Chapter 1 Introducti
Page 13 and 14:
The specific objectives of this res
Page 15 and 16:
scale plants of the two processes i
Page 17 and 18:
acetogens play their part to run th
Page 19 and 20:
In dry anaerobic digestion, recycli
Page 21 and 22:
process is inhibited and at that po
Page 23 and 24:
eported, which increased with time,
Page 25 and 26:
acids and increased downfall of pat
Page 27 and 28:
performance of a poorly mixed (1 rp
Page 29 and 30:
conventional low-solid system at th
Page 31 and 32:
supply of the nutrients missing in
Page 33 and 34:
2.6.2 Single-stage continuous syste
Page 35 and 36: single stage systems are DRANCO, Va
Page 37 and 38: of the solid content around 23% TS
Page 39 and 40: Substrate Feed TS (%) Reactor Type
Page 41 and 42: Second is that it has a high water
Page 43 and 44: 2.9 Characteristics of Digestates D
Page 45 and 46: For instance, Mumme et al., (2010)
Page 47 and 48: Comparison of liquid and solid dige
Page 49 and 50: 2.10 Management Aspects of Anaerobi
Page 51 and 52: Figure 2.11 Changing parameters dur
Page 53 and 54: amount of anaerobic fermentation re
Page 55 and 56: 3.1 Inoculum and Simulations of Was
Page 57 and 58: ed pump, water circulating jacket,
Page 59 and 60: the reactor was increased from 35°
Page 61 and 62: parts (wt/wt bas is) of digestate c
Page 63 and 64: Sand drying bed (SDB) is simple, ea
Page 65 and 66: 3.4.4 Estimation of GHG emissions i
Page 67 and 68: d) Calculation methods i) CH4 emiss
Page 69 and 70: Table 3.5 Analytical Methods for Va
Page 71 and 72: Biogas production 100X (NmL) Specif
Page 73 and 74: (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: the VFA concentration increased to
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 and 128: The flow rate of 0.569 m 3 biogas/h
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
show all

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

Create successful ePaper yourself

Delete template?

Save as template?