Waste generated pertaining to all zones
Bangalore generates around 3500 tonnes of municipal solid waste, with per capita generation of 0.4 kg/day of domestic waste. We provide an overview of zone-wise data of February 2013 on MSW per day at the Bangalore city, as shown in Fig. 5. Zone wise analysis indicates the variability of waste generated in each zone shown in Fig. 6. A quantum of waste generation in three zones (East, West, and South) is high compared to others. Also, the much lower waste generation in Yelahanka could be attributed to low economic activities.
Average MSW generated data about all zones are collected from BBMP and estimated methane emission using the IPCC default method and stoichiometric mass balance method, are discussed. Total ward-wise waste generated is 100792.10 MT per day. The calculation of methane emitting from zones during February 2013 at Bangalore was established on the amount of waste disposal and use of three independent methodologies, namely the Intergovernmental Panel on Climate Change (IPCC), experimental and the Stoichiometric method showing a massive difference in the total amount of estimated emissions. Table 1 indicated that stoichiometric estimation of emissions from waste is much higher than the Intergovernmental Panel on Climate Change determined value. Meantime, mismanagement of waste, either due to lack of adequate workforce of a vital functional element in waste management, creates serious health and environmental implications. Table 2 indicated that Intergovernmental Panel on Climate Change estimation of emissions from waste is much higher than the stoichiometric determined value. Reduction of waste generation is possible through reduced waste generation, segregation at source level, reuse, and recovery of waste. Generally, organic waste constitute (60–70%), composting and anaerobic digestion are treatment options, whereas inorganic waste (20–25%) is used for recycling. Remaining wastes that cannot be recycled are ultimately dumped in landfill sites. However, source segregation with treatment at ward levels (local levels) plays a significant role in minimizing organic fractions getting into dump site.
Table 1
Statistical analysis of Methane Emissions from solid waste generated per month across the zone
Zones Greater Bangalore Municipality BBMP | Total SW/month (tons) | Mean SW generated (tons/day) | Std deviation | Ward wise SW generated (tons/day) | CH4 Emissions (tons/day) |
IPCC | Stoichiometric |
East (44-wards) | 25317.36 | 904.19 | 33.66 | 20.55 | 32.55 | 320.99 |
West (44-wards) | 24385.64 | 870.92 | 48.90 | 19.79 | 31.35 | 309.18 |
South (44-wards) | 20142.81 | 719.39 | 41.13 | 16.35 | 25.90 | 255.38 |
Bommanahalli (16-wards) | 9075.55 | 324.13 | 52.56 | 20.26 | 11.67 | 115.07 |
Mahadevapura (17-wards) | 11238.56 | 401.38 | 29.75 | 23.61 | 14.45 | 142.49 |
R.R.Nagara (14-wards) | 4351.71 | 155.42 | 18.36 | 11.10 | 5.60 | 55.17 |
Yelahanka (11-wards) | 2594.03 | 92.64 | 12.66 | 8.42 | 3.34 | 32.89 |
Dasarahalli (8-wards) | 3686.43 | 131.66 | 9.69 | 16.46 | 4.74 | 46.74 |
Total | 100792.10 | 3599.72 | 246.71 | 136.54 | 129.59 | 1277.90 |
Table 2
Methane emission from solid waste generated per day across the zone
No. of Days | Total MSW Generated in Tons per day (198 wards) | CH4 Emissions (tons/day) |
Default Methodology, IPCC | Stoichiometric mass balance approach |
1 | 3321.23 | 119.56 | 1179.04 |
2 | 3578.44 | 128.82 | 1270.35 |
3 | 3544.48 | 127.60 | 1258.29 |
4 | 3730.72 | 134.31 | 1324.41 |
5 | 3674.68 | 132.29 | 1304.51 |
6 | 3604.77 | 129.77 | 1279.69 |
7 | 3684.87 | 132.66 | 1308.13 |
8 | 3639.01 | 131.00 | 1291.85 |
9 | 3643.06 | 131.15 | 1293.29 |
10 | 3571.99 | 128.59 | 1268.06 |
11 | 3708.40 | 133.50 | 1316.48 |
12 | 3610.59 | 129.98 | 1281.76 |
13 | 3597.66 | 129.52 | 1277.17 |
14 | 3666.78 | 132.00 | 1301.71 |
15 | 3694.97 | 133.02 | 1311.72 |
16 | 3584.03 | 129.03 | 1272.33 |
17 | 3445.72 | 124.05 | 1223.23 |
18 | 3719.34 | 133.90 | 1320.36 |
19 | 3718.83 | 133.88 | 1320.19 |
20 | 3612.93 | 130.07 | 1282.59 |
21 | 3720.65 | 133.94 | 1320.83 |
22 | 3607.94 | 129.89 | 1280.82 |
23 | 3650.82 | 131.43 | 1296.04 |
24 | 3471.45 | 124.97 | 1232.37 |
25 | 3493.83 | 125.78 | 1240.31 |
26 | 3540.13 | 127.44 | 1256.75 |
27 | 3478.88 | 125.24 | 1235.00 |
28 | 3475.91 | 125.13 | 1233.95 |
Total | 100792.10 | 3628.52 | 35781.20 |
ESTIMATION OF CARBON STORED IN MAVALLIPURA LANDFILL
Insitu waste sample collection
Estimating the carbon stored in the buried organic matter in the Mavallipura landfill site has been carried out. Using hand auger, the solid waste samples were collected at two different locations in the Mavallipura landfill, as shown in Fig. 7. Auger drilling operation using a 150mm diameter is carried out in a landfill site. The purpose of the auger drilling operation was to characterize the municipal solid waste visually, retrieve bulk samples of debris from different depths, and varying degrees of degradation and age.
The changes in the composition of MSW should form essential criteria for any waste management system. Hence, the data available on the MSW composition of the from different borehole A & B has been collected and analyzed. MSW composition mainly depends on several factors such as cultural traditions, food habits, socio-economic and climatic conditions. It also varies from place to place. Studies are carried in the Mavallipura landfill site with a 100kg MSW sample. The collected MSW sample is sorted physically in various ingredients, such as paper, fiber, metals, soils, glass, and miscellaneous waste on a sorting platform. The individual components are separated and weighed. From Fig. 8, the observed Municipal solid waste comprises 8 to 10% yard waste (garden waste), 20 to 21.9% of paper, cardboard waste in landfill, indicating recycling activities of paper and cardboard at the source itself. 35 to 39% of plastic might be due to the urbanization, and increased use of plastic carry bags, 9 to 9.7% miscellaneous wastes (includes textile, rubber, leather, and other) and 16 to 16.8% metals and glass products are effectively recycled by segregation at sources itself.
Solid waste samples were collected at two different locations in the Mavallipura landfill. Samples were collected for every half meter interval (0-0.5m, 0.5-1m, and so on) until 6m depth. The solid waste sample's first half-meter was discarded as it contained the soil cover mixed with the upper layer of waste. Samples were collected in the plastic bags, sealed and labeled, then brought back to the laboratory, and determined all the samples' moisture content. The rest of the samples were spread out for air drying in the room, as shown in Fig. 9. They were further dried at 65°C in an oven, and then the various components were manually separated and weighed. The soil component was separated using sieves of different sizes into three fractions, namely < 2.36 mm but > 1.18 mm, < 1.18 mm but > 600 µm, and < 600 µm. The slightest bit (< 600 µm) was used to determine the TOC analyzer's carbon content.
In-situ testing’s
Temperature Test
Temperature of the MSW material is recorded as soon as the waste is brought to the surface and attempt made to evaluate the age of MSW material, newspaper, magazines, or other documents can provide general information on the age of the MSW in the landfill at the location of the bore
From the Fig. 10 shows the temperature tended to increase with depth. Due to the heterogeneity of material. The highest temperatures for landfills were generally reported at mid-waste elevations with temperatures decreasing near the top. The temperatures near the top undergo variations similar to seasonal temperature fluctuations, whereas the temperatures at greater depth generally follow stable trends. Initial decomposition of wastes in a landfill occurs under aerobic conditions. Anaerobic conditions prevail upon depletion of oxygen at the bottom of the landfill. However, the trend shows some variations due to the heterogeneity of the waste.
Moisture content Test
At each depth, the moisture content of the MSW material is estimated by dry gravimetric moisture content: ratio of the mass of water in a waste sample to the mass of solids in the waste sample, expressed as a percentage. During the moisture content determinations, the temperature was maintained at 60° C to avoid combustion of volatile materials. From the Fig. 11 shows the moisture content tended to increase with depth. The moisture content increase with depth due to the degradation. The increase in moisture content may be also contributed to increasing in moisture content withholding capacity of MSW due to the disintegration of particles after degradation.
Unit Weight Test
In Mavallipura landfill, using the in-situ method of measuring the unit weight by replacing the waste with calibrated gravel. The weight of waste removed from a 0.5-1.0m length of the borehole was measured and the volume of the material was evaluated by backfilling the 0.5-1.0 m interval with gravel of known unit weight. The unit weight of MSW is expressed as a kN/m3. Figure 12 shows the unit weight profile with depth ranging from a low unit weight of 3.8 kN/m3 near the surface and the highest value of approximately 8.4 kN/m3 at a depth of 6 m. The unit weight tended to increase with depth.
pH Test
The acidity or alkalinity of an MSW sample can be expressed on the pH scale. The unit of the scale is called pH value. This scale runs from 0 to 14 pH values. The neutral point in this scale is at pH 7.0. All values above pH 7.0 represent alkalinity and all values below 7.0 denote acidity. The degree of alkalinity increases as values go above pH 7.0 and the degree of acidity increases as the pH decreases below 8.0. Figure 13 shows a pH variation of 8.3 to 8.9. pH is controlled principally by a series of chemical reactions. The important reaction is the degradation of organic materials to produce carbon dioxide and a small amount of ammonia. These dissolve in the leachate to form ammonium ions and carbonic acid. The carbonic acid dissociates with ease to produce hydrogen cations and bicarbonate anions which influence the level of pH of the system. Additionally, pH is also influenced by the partial pressure of the generated carbon dioxide gas that is contact with the leachate.
TOC Test
The typical height of solid waste dumping is 6m from the above ground level and the deposit consisted of uncompacted waste. By using Total organic carbon (TOC) analyzer, total organic carbon expressed in percentage was evaluated with respect to depth. From Fig. 14 shows that carbon stored in organic matter is increasing with depth from approximately 2% at 1.0 m depth to 23% at 6m depth. Similarly, the total carbon content of MSW in other countries has been reported to be the same range of 15.74 to 29.67 % being identified for Taiwan [20]. These ranges are considered to be more representative of a heterogeneous material obtained from an MSW In-situ testing.
Volume of Mavallipura landfill
The total volume of municipal solid waste in the Mavallipura landfill was determined by measuring the landfill area and average depth. A GPS tracker (Garmin) with an altitude display was used to measure the dumpsite's perimeter. The perimeter of the dumpsite is 867 m, and it encloses an area of 59,828 m2 (Fig. 15(a)). Based on the contour map, the landfill's average vertical depth is 17m—typical Mavallipura landfill site sketch (Fig. 15(b)). The uncompacted waste dump area at the top level is about 875m2; the volume is estimated for each respective depth till 6m, and the carbon stored in each layer is determined. Mass of the MSW in landfills above the ground level is calculated based on the density and volume with respective each layer. Carbon stored in the uncompacted waste is calculated based on the carbon content obtained from the TOC analyzer and mass of MSW stored in a landfill with respective layers. The carbon stored in the uncompacted waste, as shown in Table 3.
Table 3
Carbon stored in solid waste dump above the ground level
Above GL Depth, m | In-situ density, kN/m3 | Mass of MSW Stored in landfill, metric tons | Carbon content obtained from TOC analyzer, % | Carbon stored in landfill, metric tons |
1 | 4.02 | 1157 | 2 | 23.14 |
2 | 4.5 | 1245 | 5 | 62.25 |
3 | 5.8 | 1552 | 7.5 | 116.4 |
4 | 7.0 | 2168 | 12 | 260.16 |
5 | 7.45 | 2327 | 16 | 372.32 |
6 | 8.0 | 2562 | 23 | 589.26 |
Total Estimated MSW carbon stored above the ground level | 1423.53 |
Due to the physical nature of solid waste present in the landfill, it is tough to conduct the boring and sampling below the ground level. Hence, the total volume is calculated based on the contour map. The total volume of landfill below the ground level is 52714 m3, assuming the bulk unit weight is 8kN/m3, the carbon content is 23%. The total Mass of MSW stored is 42171 metric tons, and the total carbon stored in MSW is 9699metric tons below the Mavallipura landfill is estimated. Finally, the sum of the net amount of standing stock carbon deposited above and below dump is 11122.53 metric tons.
Global Carbon Sequestration from Mavallipura landfill
Carbon sequestration from MSW buried in the Mavallipura landfill on a global scale was estimated by using Eq. 5.
Cseqi = Gi x LFfri x CSFm (5)
Gi is the mass of MSW generated in the Mavallipura landfill is 600metric tons per day; LFfri is the fraction of waste generated in Bangalore buried in landfills; CSFm is the carbon stored factor is 0.302 based on the EPA's guidelines.
Global carbon sequestration due to MSW burial in the Mavallipura landfill is estimated to be 10x106 tons per year. Only stored carbon associated with paper, plastic, wood, and yard. etc., was considered.
Barlaz [21] reported the global carbon sequestration of MSW burial in the US landfill is estimated to be 118.7x106 per year. Bogner [22] determined the carbon sequestration of MSW burial in the US landfill was found to be 31.6x106 tons per year.
Carbon sequestration is one of the significant factors that should be considered in comparing the environmental benefits and liabilities associated with the MSW landfills in specific and MSW management strategies in general. Other factors include gaseous emissions from MSW decomposition and the equipment used for MSW landfill operation, energy consumed during MSW landfill construction and maintenance, and methane's potential recovery for energy. Hence, appropriate treatment options are necessary to treat the municipal solid waste's organic fractions to reduce Greenhouse Gas Emissions. Decentralized treatment options of converting to energy or composting would provide a better solution by converting the waste to wealth.
METHANE PRODUCTION FROM MAVALLIPURA LANDFILL
IPCC Default Method
The methodology was adapted from IPCC [23]. Methane emission for Bangalore waste was estimated as
Methane emission = 1227.5 x 0.80 x 0.6 x 0.200 x 0.77 x 0.5 x 16/12 = 63 Gg/yr
Obtained methane emission is used to calculate energy and power generation using a density of methane at standard conditions was taken as 0.7167 kg/m3 and calorific value (lowest) as 9,000 kcal/m3. Energy production for one-year adopting a gas collection of 80 % is 2,375 TJ, and the corresponding power generated is calculated as 75 MW.
LandGEM model
Mavallipura landfill methane emission is calculated based on the landfilled waste data for the period 2007 to 2013. The amount estimation of generated methane is the landfill site (1,022,000 Mg/year), annual acceptance rate, and concentration of total non-methane organic compounds (4,000 ppmv as hexane) and the years of waste acceptance. Figure 16 illustrates the drift of methane gas emissions in different years of Mavallipura landfill site projects. Results revealed that the amount of annual waste generation in the Mavallipura landfill, in the range of 1, 10,000 tons to 2,20,000 tons from the open landfill to closure landfill.
Over time, the landfill scenario has been changing. With a drastic increase in waste generation rates, scarcity of land availability, and GHGs issues, there is a unique need to modify the existing landfill design aiming at the energy and power generation from waste with less requirement of the area. The calculations of methane emitting from landfill during 2007–2013 at the Mavallipura landfill were establish on the amount of waste disposal and use of three independent methodologies, namely, Intergovernmental Panel on Climate Change (IPCC), and LandGEM showing a minor difference in the total amount of estimated emissions.