Changing composition of USW and its impact
In the last 20 years the composition of the wastes generated both at the residence levels as well as the city level has changed significantly. Tables 1 and 2 show the generation rates and physical composition of Bangalore MSW collected from different types of waste generators. MSW recorded, comprises of wastes generated from residences, markets, hotels and restaurants, commercial premises, slums, street sweepings and parks. Residences contribute 55% of total of wastes, which is highest among all sources (TIDE, 2000). Waste generated from hotels and eateries form about 20%, fruit and vegetable markets contribute about 15%, trade and commerce about 6% and from street sweeping and parks about 3%, . The slum areas contribute only 1% of total. This is because the slum population and area in Bangalore is low in comparison to other cities and towns. Table 2 shows the waste composition of Bangalore comprising predominantly fermentables (72%), and paper and cardboard (11.6%).
The high wet and fermentable waste content of Bangalore MSW requires its daily removal from places of generation. In a decentralized system, wastes gathered from primary collection by handcarts may be subject to immediate treatment by aerobic composting or biomethanation within the locality or ward. This will avoid transportation costs of around Rs1000-1500/t and thus will be more sustainable and economic. In the past a significant component of the wastes placed in open street bins were rapidly sought by rag-pickers who removed the recyclables. The impact of this is presented in Figures 1a, 1b and 2, which show that the percentage of organic waste will quickly increase in MSW from primary collection point to the time it reaches the dump site due to multilevel recovery of recyclable wastes. This also changes the extent of decomposable component of the wastes and presents various other forms of environmental implications (Chanakya and Sharatchandra, 2005). As the wastes gradually becomes enriched with easy to decompose materials, it also becomes easily amenable to anaerobic fermentation processes that convert the organic matter within to CO2 and CH4, the latter being a greenhouse gas. From 1988 to 2000 there is a reasonable change in waste composition: fermentables, paper and plastic has content increased by 7%, 3% and 0.2%, respectively.
Table 1: MSW generation in Bangalore
| Source |
Quantity (t/d) |
Composition (% by weight) |
| Domestic |
780 |
55 |
| Markets |
210 |
15 |
| Hotels and eatery |
290 |
20 |
| Trade and commercial |
85 |
6 |
| Slums |
20 |
1 |
| Street sweeping and parks |
40 |
3 |
| Source: Chanakya and Sharatchandra, 2005 |
Table 2: Physical composition of MSW in Bangalore
| Waste type |
Composition (% by weight) |
| Domestic |
Markets |
Hotels and eatery |
Trade and commercial |
Slums |
Street sweepings and parks |
All sources |
| Fermentable |
71.50 |
90 |
76 |
15.6 |
29.9 |
90 |
72 |
| Paper and cardboard |
8.39 |
3 |
17 |
56.4 |
2.49 |
2 |
11.6 |
| Cloth, rubber, PVC, leather |
1.39 |
|
0.33 |
3.95 |
0.54 |
0 |
1.01 |
| Glass |
2.29 |
|
0.23 |
0.65 |
8.43 |
0 |
1.43 |
| Polythene/plastics |
6.94 |
7 |
2 |
16.6 |
1.72 |
3 |
6.23 |
| Metals |
0.29 |
|
0.26 |
0.38 |
0.23 |
0 |
0.23 |
| Dust and sweeping |
8.06 |
|
4 |
8.17 |
56.7 |
5 |
6.53 |
| Source: TIDE, 2000 |
Figure 1a: Composition of USW immediately after being places in bins (Rajabapaiah, 1988)
Figure 1b: Composition of USW after ragpickers sort and recycled materials (Rajabapaiah, 1988)
Figure 2: Composition of USW found at the dumpsites (TIDE, 2000)
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