5 Composition of solid waste

Dr. Logakanthi S

1.   Objectives:

After completing this module, you should be able

• To understand the various constituents of the municipal solid waste
• To gain knowledge about waste generation
• The understand the factors influencing waste composition
• To understand the status of municipal solid waste composition in India

2. Solid waste definition

Solid waste is defined differently in different countries. It most commonly connotes municipal solid waste (MSW). According to United States Environment Protection Agency the term “solid waste” means any garbage, refuse, sludge from a waste treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including solid, liquid, semisolid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, and from community activities, but does not include solid or dissolved materials in domestic sewage, or solid or dissolved materials in irrigation return flows or industrial discharges. In the United Kingdom it is commonly known as refuse or rubbish and is defined as waste from households, as well as other waste, which because of its nature or composition, is similar to waste from households. In India, solid waste is categorized into municipal wastes, hazardous wastes, medical wastes and radioactive wastes. According to Ministry of Environment, Forest and Climate Change, Government of India, MSW refers to commercial and residential wastes generated in a municipal or notified area in either solid or semi-solid form excluding industrial hazardous wastes but including treated bio-medical wastes.

3. Sources

Municipal Solid Waste can be broadly classified based on the nature of its composition as organic and inorganic waste. The World Bank report segregates this MSW based on its composition and source as under as most of the solid waste falls under these types. Most often inert material like construction debris also get mixed up with MSW.

Figure 1. Municipal Solid Waste in India (Image source, The Hindu, 4th July 2013)

Table 1. Composition of solid waste and its source of generation

In India, depending upon the source, MSW is further categorized into three types viz. household waste which arises from domestic areas from individual houses; commercial wastes which arise from individually larger sources of MSW like hotels, office buildings, schools, etc.; and municipal services wastes which arise from area sources like streets, parks, etc.

4.  Composition of Municipal Solid Waste

The rate of waste generation is an indicator of socio-economic development of a region. Many factors like economic development, cultural norms, geographical location, climate and energy sources, influence the composition of MSW. As a country urbanizes and population becomes economically well off, consumption of inorganic materials (such as plastics, paper, and aluminum) increases, while the relative organic fraction decreases. Generally, low and middle-income countries have a high percentage of organic matter (40-80%) in the urban waste stream. The material used for construction (example wood versus steel), fuel used for heating (example coal versus gas) etc., differs according to the geography and climate of the place there by influencing type of municipal solid waste generated. Figure 2 shows the MSW composition of the world in 2009 (World Bank, 2014). Table 2 below further highlights the composition of waste in the countries based on their income level, which reiterates the role of economic development on waste composition.

5.  Composition and state of Municipal Solid waste in India

India is in a rapid phase of urbanization with nearly 32% of the population of the country staying in the urban areas according to 2011 census. This rapid urbanization is putting immense demand on its resources, infrastructure and energy requirements. Adding to this is the rapidly growing volume of municipal solid waste, which is posing another serious challenge. The per capita waste generation refers to the amount of waste generated by one person in one day in a country. This is affected by the economic ability and hence is strongly correlated to the GDP of the country. The average per capita generation in India is 370 grams/day as against 2000g/day in USA and 700grams/day in China (Annepu, 2012). The per capita waste generation in the country is increasing at the rate of 1.3% per year. Cities in the Southern states of India generate highest per capita waste of 570grams/day. While the cities in the western states of the country produce the least amount of per capita waste of 440grams/day.

Figure 2. Global Solid Waste Composition (World Bank, 2014)

Table 2 Type of waste composition based on income level (World Bank, 2014)

Income Level	Organic(%)	Paper(%)	Plastic(%)	Glass(%)	Metal(%)	Other(%)
Low Income	64	5	8	3	3	17
Lower Middle Income	59	9	12	3	2	15
Upper Middle Income	54	14	11	5	3	13
High Income	28	31	11	7	6	17

The urban MSW in India contains 51% of organic matter, 17.5% of recyclables and 31% of inert waste. This high level of organic matter is at the waste dumps, which is after picking of certain percentage of recyclables by the informal sector from the source. Table 3. Depicts the composition of MSW in India

Table 3. Composition of MSW in India (Annepu, 2012)

MSW components	Materials
Compostables	Food waste, landscape and tree trimmings
Recyclables	Paper, Cardboard, Plastics, Glass, Metals
Inerts	Stones and silt, bones, and other inorganic materials

Presently there is no proper system of management of this waste. Firstly there is lack of storage and segregation of waste at source as people lack awareness and so do not participate in managing the waste. Secondly, there is no proper public system of waste collection from the primary sources and so municipal sanitation workers collect the waste thrown in streets and public open spaces on an irregular basis. Wastes are collected mostly using handcarts and tricycles and are stored in temporary storage spaces before being transported by motorized vehicles. These temporary storage spaces are usually concrete bins and small open spaces in the street corners. This further causes spillage of waste and littering of the area, as they are inadequate for volume of waste collected. The waste thus collected is transported through motorized vehicles to dumpsites, which are managed by sanitation workers who lack adequate training in handling them. This further adds to spillage of waste. Thirdly the dumpsites are not scientifically managed. Most often these dumpsites are located outside the city. The waste dumped there is just piled without compacting or covering with inert material as a result they emanate foul smell and are breeding grounds for pathogens and pests. Further, liquid seeping through the rotting organic waste called leachate pollutes underground water and poses a serious threat to health and environment. Thus, there is total lack of apathy to management of this waste (Asnani, 2006).

The composition of waste determines the type of waste management practice. Presence of large proportion of organic matter makes it suitable for aerobic and anaerobic digestion. However, for these processes to be effective it is essential to keep the raw material for the process free of inorganic material. This can be achieved by emphasizing on segregation at source, which at present is lacking. Other available options for the management of this waste include waste to energy process, composting, incineration, pyrolysis, sanitary landfill with gas recovery etc. A combination of methods along with increased awareness and strict regulation and implementation of the same is the only way to tackle this growing waste in the future.

6. Summary

• This lecture familiarizes about:
• Different constituents of MSW
• Waste generation rates at different countries Factors influencing waste composition

7. References

• Asnani, P. U. (2006), Solid waste management. India Infrastructure Report, 160-189
• World Bank (2014), Waste composition, Urban Development Seies- Knowledge paper
• Status of Solid waste in India, CPCB, http://www.cpcb.nic.in/divisionsofheadoffice/pams/Status_Municipal.pdf
• Annepu, Ranjith Kharvel (2012), Sustainable solid waste management in India, Columbia University, New York