MSW composition

The composition of urban waste stream as its generation is constantly changing due to the same factors mentioned above, however, factors such as income, lifestyle and residence type (urban vs. rural) and seasons affect greatly to variation in composition. MSW affluent is often divided into six main categories:

organic, paper, plastic, glass, metals and others (see Table 4). Waste managers agree that generally that categorization of MSW is sufficient for planning purposes (Hoornweg & Bhada-Tata, 2012, p. 16; Letcher & Vallero, 2011, pp.

111,112; Williams, 2005, p. 80).

Even though the author recognizes that MSW should be classified as specifically as needed according to the waste treatment technologies in place, in this study the classification mentioned above was chosen because is sufficient for the development of the planning tool.

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Table 4. Types of MSW and Their Sources.

Note: Retrieved from: What a Waste: A Global Review of Solid Waste Management, 2012, p. 16, table 9.

Copyright © 2012 The World Bank Group, All Rights Reserved.

Non-municipal waste

Even though, non-municipal wastes are out of the boundaries of the present research is important to clearly identify them because they can be often found mixed with MSW in developing countries.

The largest and most representative waste stream with those characteristics is Construction and Demolition (C&D). Due to its high volume, municipalities around the world often does not contemplate its collection and disposal. Instead, municipalities have in place separate management systems for this waste stream.

However, C&D is a rich material in soil, gravel and clay content and other useful materials that can be recycled and reuse for landfill engineering (e.g. to build landfill cells, for capping to cover the final site) for road ways, car parks and landscaping (Williams, 2005, pp. 113-114). In developing countries C&D waste is approximately 10-15% of the total waste matrix, meanwhile in high income economies C&D has a much larger portion and can reach levels up to 50% of the total waste generation (United Nations Environment Programme, 2011, p. 292).

Likewise, other non-MSW types are: healthcare waste, agricultural waste, and other processes waste from ICI sector (Industrial, Commercial and Institutional sector), because they are different in composition than household waste. In some cities of the world, those wastes are collected mixed with the MSW stream, and end up being disposed all together, generating negative impacts to the environment and human health. Municipalities in developed economies do not attend those kinds of wastes, but in developing and emerging economies where the waste legislation is less severe, those wastes are not well separated from the MSW waste stream (Hoornweg & Bhada-Tata, 2012, pp. 16-17; United Nations Environment Programme, 2011, pp. 294-296).

Therefore, due to the difference in waste legislation among countries regarding non-municipal waste types, they won’t be taken into consideration in the present research. Only the wastes that follow the working definition of MSW will be

Type Sources

Bio waste Food waste, yard waste (leaves, grass, brush), wood, process residues Paper

and cardboard

Paper scraps, cardboard, newspapers, magazines, bags, boxes, wrapping paper, telephone books, shredded paper, and paper beverage cups. Strictly speaking, paper is organic but unless it is contaminated by food residue, paper is not classified as organic.

Plastic Bottles, packing, containers, bags, lids and cups.

Glass Bottles, broken glassware, light bulbs, colored glass.

Metals Cans, foil, tins, non-hazardous aerosol cans, railings, bicycles.

Special waste bulky items, consumer electronics, white goods, batteries, oils and tires

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considered, the ones are listed in the table 1 under the column municipal waste types and the broad classification can be found in the Table 4.

Variation in waste composition in the cities of the world

Figure 4. MSW composition by income 2010.

Note: Retrieved from: What a Waste: A Global Review of Solid Waste Management, 2012, p. 19, fig. 8.

Copyright © 2012 The World Bank Group, All Rights Reserved.

When analyzing the municipal waste composition worldwide according the countries' wealth (see Figure 4), two important trends can be seen. On one hand, it seems that, the lower the country’s income, the higher the content for organic material present in MSW. So that low income countries has the highest average of organic content being this 64% of the MSW matrix, middle-income has 54-59%, and high–income has only 28% respectively. On the other hand, as the wealth of the economies increases, more diverse the MSW composition becomes. So that, whereas the organic portion decreases, the paper and inorganic portion increases, becoming paper, plastic, metal and glass (recyclables) more than half of the MSW.

Similarly, when analyzing the MSW composition by regions same trends are present and similarities among regions are apparent. Municipal waste in AFR MENA and EAP tend to have nearly 60% of organic portion, 30-35% of paper, plastic and others wastes, and only 5-8% of glass and metal (Hoornweg & Bhada-Tata, 2012).

LAC and SAR have nearly the same amount of organic portion, 54% and 50%

respectively, however, in SAR region the composition is clearly different than all the other regions. In SAR the second biggest portion after organics are other wastes with a participation of 37%, this figure is clearly in disproportion with other regions, when this waste type does not exceed in any case 17%. Paper, plastic, metal and glass, all together do not exceed 13%. In LAC, paper, plastic and other wastes are about 40% and only 2% and 4% metal and glass, which seems to be align with the other regions trends (Hoornweg & Bhada-Tata, 2012).

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EAC municipal waste is the most diversified matrix after OEDC has less than half of organic portion and the portion of paper and inorganics is similar to the OEDC distribution. In OEDC countries, organics are just 27% and paper is the highest portion with 32% and inorganics are the remaining 40% (Hoornweg & Bhada-Tata, 2012).

United Nations (2010, pp. 11) as well as many other waste manager experts point out that, accurate data of volume and quantities of waste types, are essential to plan an effective waste strategy. However, all of them recognizes the lack of reliable and compatible data and constant monitoring in the sector are an important drawback. Waste statistics are often incompatible or simply non-existent en many cities of the world, including many cities from developed nations.