1. Current rate of waste generation

Greater Bangalore is the administrative, cultural, commercial, industrial, and knowledge capital of the state of Karnataka, India with an area of 741 sq. km. and lies between the latitude 12°39’00’’ to 13°13’00’’ N and longitude 77°22’00’’ to 77°52’00’’ E. Bangalore city administrative jurisdiction was redefined in the year 2006 by merging the existing area of Bangalore city spatial limits with 8 neighbouring Urban Local Bodies (ULBs) and 111 Villages of Bangalore Urban District. Bangalore has grown spatially more than ten times since 1949 (~69 square kilometers to 716 square kilometers) and is the fifth largest metropolis in India currently with a population of about 9 million. Bangalore city population has increased enormously from 65,37,124 (in 2001) to 95,88,910 (in 2011), accounting for 46.68 % growth in a decade. Population density has increased from as 10732 (in 2001) to 13392 (in 2011) persons per sq. km. The per capita GDP of Bangalore is about $2066, which is considerably low with limited expansion to balance both environmental and economic needs (Ramachandra et al., 2012a).

Spatial increase in city area and increase in population, has increased the total amount of Municipal Solid Waste (MSW) from 650 tonnes per day - tpd (1988) to 1450 tpd (2000). The current estimates indicate that about 3000 - 4000 tons of MSW is produced each day in the city-the daily collection is estimated at 3600 tpd (Ramachandra et al., 2012).  The increase in the per capita generation from 0.16 (1988) to 0.58 kg/d/person (2009) is due to the changes in consumption pattern. Changes in composition are noticed in recent time with increasing quantity of waste.

2. Composition of solid waste

Usually municipal solid waste can be broadly categorized into organic or inorganic waste using major components of solid waste composition. Organic waste is also known as wet waste whereas inorganic waste is also known as dry waste. Inorganic waste includes both recyclable and non-recyclable materials whereas organic waste includes all the waste components, which can degrade in natural environment like left over food, vegetable and fruit peel. Municipal solid waste is heterogeneous mixture of solid materials which does not have any use to society. Food waste, plastic, paper, rubber or leather, glass and textiles are the common MSW components. Source wise solid waste composition is shown in Table 3. Waste composition changes with source of generation, but most of the sources generated a major fraction (>70%) of organic waste. It is evident that Indian waste has more of organic than inorganic constituents, except slums and commercial places.

Solid wastes generated in Indian cities mainly composed of organic fraction and are biodegradable. It generally includes degradable (paper, textiles, food waste, straw and yard waste), partially degradable (wood, disposable napkins and sludge) and non-degradable materials (leather, plastics, rubbers, metals, glass, ash from fuel burning like coal, briquettes or woods, dust and electronic waste) (Jha et al., 2008; Visvanathan, 2004).

Table 3: Physical composition of MSW in Bangalore

Major portion (72-79%) of municipal solid waste is organic  (Ramachandra, 2009; Ramachandra 2011; Sathiskumar et al., 2001; Ramachandra et al., 2012; Sharholy et al., 2007; GOI,1995) and contribution of inorganic component is gradually changing and is likely to show further changes in the future.  The biodegradable fraction is quite high, arising from the practice of using fresh vegetables in India.  The plastic and metal contents are lower than the paper content and do not exceed 1% except in metropolitan cities.  This is mainly because large-scale recycling of these constituents takes place in most medium and large cities. The composition of MSW at generation sources and collection points determined on a wet weight basis consists mainly of a large organic fraction (70-75%), ash and fine earth (5-8%), paper (10-14%) and plastic, glass and metals (each less than 3-5%) (Ramachandra et al., 2012).  Paper waste generally falls in the range of 3-7%, when the waste reaches the disposal site (Asnani, 1998).  The organic fraction is high (>80%) in many pockets within many South Indian cities like Chikkamagalur and is largely represented by vegetable, fruit, packing and garden waste (Chanakya, et al., 2009).  Physical composition of MSW in Bangalore is having paper 8%, Textiles 5%, plastic 6%, metals 3%, glass 6%, ash fine earth and others 27% and compostable matter is about 45% (CPCB 1999, Sharholy et al., 2008). Bangalore organic waste mainly consists of vegetable and fruit wastes, its percentage contribution ranges between 65 to 90% (Rajabapaiah, 1988; TIDE, 2000; Ramachandra, 2009; Chanakya et al., 2009). Many studies had been conducted in academic institution to know the waste composition. Studies compiled in Table 4 show that organic fraction ranges from 72.5 (Sathiskumar et al., 2001), 79.6 (Ramachandra et al., 2012) and 88% (Rajabapaiah, 1995).

3. Factors/variables of changes in quantity and composition

Waste quantity and composition depends upon various factors such as country, topography of the area, different seasons, food habits, commercial status and activities of the city (Jha et al., 2008; Thitame et al., 2009; Ramachandra 2009) and standard of living. The relative percentage of organic waste in MSW is generally increasing with the decreasing socio-economic status; evident from rural households as well as low and mid income urban households generate more organic waste than urban households.

Table 4: Studies on waste composition (%) of Bangalore