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close this bookCommunity Participation - Solid Waste Management in Low-Income Housing Projects: The Scope for Community Participation (HABITAT, 1989, 54 p.)
View the document(introduction...)
View the documentGuidelines for the instructor
View the documentIntroduction
View the documentI. Waste management in human settlements
View the documentII. Waste collection
View the documentIII. Storage of waste
View the documentIV. Waste disposal-methods
View the documentV. Resource recovery: handling and dealing in waste
Open this folder and view contentsVI. Recycling examples
View the documentGlossary
View the documentBibliography
Open this folder and view contentsAnnexes
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IV. Waste disposal-methods

There are four methods of disposing of household waste:

· Land application (dumping);
· Composting;
· Incineration;
· Resource recovery (see chapter V).

These options are all practiced by low-income residents. Community participation in waste disposal is, therefore, first a question of organization and motivation and, only secondly, a matter of knowledge. In slum areas where no waste-disposal service exists, individual households often bury waste in small pits in the garden, while others burn their waste regularly on the plot. Composting occurs especially where agricultural plots are found. Finally, many recoverable materials are collected by scavengers and waste dealers in every city.

The sharp contrast between the tidiness of individual houses and the untidiness of their surroundings is very common in squatter areas and often reflects the lack of co-ordination and co-operation between dwellers. A collective neighbourhood clean-up campaign can have a dramatic effect, because the results are so visible and pleasant. It might persuade residents that collective responsibility for the environment is worthwhile, and this would provide a natural basis for co-operation between the neighbourhood and the authorities, if the municipality can be persuaded to remove collected waste.

Alternatively, the possibilities of resource recovery can be a first incentive to participate in a waste-collection system. Separation of certain materials at source, such as glass, paper and kitchen refuse, requires co-operation from residents and gives a start to the sharing of responsibility.

Land-fill applications

Controlled dumping of municipal waste is a safe and efficient method of waste disposal that, in the long run, renders the waste harmless and allows the land to be used again for other purposes. Controlled dumping prevents harmful environmental effects and is a relatively cheap method of waste disposal. However, it requires a great deal of land located at some distance from settlements, and this might be difficult to find. It also demands great quantities of soil to cover the dumped waste.

The following requirements for landfill should be looked into:

· Site conditions;

Preferably a big existing excavation, quarry site or a shallow waterlogged area which has to be filled. Avoid soils with good natural drainage.

· Soil requirements;

A lot of soil is required to be spread over each layer of 2-3 metres of waste (soil amount is 10 per cent (20-30 cm) of waste amount).

· Hazardous waste;

Leachate of industrial or other poisonous material must be avoided. Production of anaerobic gas might occur after some years in wet material;

· Future use;

The future bearing capacity for construction may be rather low. Natural compacting will continue for years. Filled land cannot be used for agriculture but sometimes for forestry of parks.

Despite the simplicity of the approach, it is applied in very few cities in developing countries. What takes place instead is indiscriminate and uncontrolled dumping. This is very harmful environmentally as the waste may include dangerous chemical products, and leaching occurs with risks to groundwater. Since such dumps usually also become the homes of a large scavenger-community, the health implications are serious.

In certain areas (e.g., Guayaquil in Ecuador) landfill is used to make seashore/swamps habitable. Roads require, however, large deposits of sand, so as to attain the necessary stability.

Composting

Composting has long been used in agriculture, but its application to the digestion of urban waste has only recently been developed. It is essentially a process by which organic matter (food, leather, wood, paper etc.) decays. Inorganic matter, such as sand, metal and glass, does not decay and is, therefore, unaffected by composting. In low-income housing areas, as much as 90 per cent of waste might be compostable.

Composting can be done in small quantities and is, therefore, a waste-disposal method that is possible even at the neighbourhood level or at the transfer-depot site. The composting process might take a month, and composting can be turned into a profitable business for holders of small vegetable plots and nurseries for potted and garden plants. Composting needs air, humidity and warmth. Stacked waste with lots of kitchen waste needs to be turned regularly, in order to allow the air to reach the micro-organisms which digest the organic matter and break it down into harmless components. When the waste pile or ridge is turned every week, this might be sufficient in a warm climate. With sufficient air access, the smells will be minimal.


Figure

The Chinese aerobic-composting system consists of a 2 x 2 m pile, with bamboo or PVC pipes at the bottom of the pile in both directions. Where those pipes cross, vertical (chimney) pipes are placed. When the pile is 1.7 metres high, the outside is plastered with mud, and all pipes are extracted (see drawings). After two months, the pile can be dismantled, and inorganic and large parts can be separated, before the residue is used as compost.

Incineration

Generally speaking, refuse contains 25-60 per cent water and 15-50 per cent combustible material, such as plastic, plant material and wood. The rest is non-combustible (sand, stone, metal, glass etc). During burning, hot gas is produced, containing carbon dioxide and a great number of acid gases. Some materials, such as paint, plastics, rubber and synthetic textiles, produce toxic fumes. All of these are harmful and constitute air pollution. Ashes will correspond to 15-30 per cent of the original weight of the refuse.


Figure

The burning or incineration of waste is commonly done for sites where no collection is done or is possible. In the case of small hospitals or clinics, burning is advisable, for destroying bandages and other septic remains. The burning has to be done in a proper incinerator, to ensure complete combustion. The burning is achieved by the use of paper, cardboard and timber remnants.

For household incinerators, sufficient quantities of dry paper, cardboard and timber are required, and wet materials that can be composted should, therefore, not be placed in the incinerator. The burning of waste in bins or masonry receptacles in the backyard are examples.

What about neighbourhood incinerators to get rid of some of the waste in dense residential areas? The following aspects must be taken into consideration.

· Burning dry materials (filling in the incinerator);
· Composting wet materials (separation);
· Possibility to remove ashes (special tools, gratings etc.);
· Air inlet and smoke outlet (rainy season function);
· Avoid flying ashes in regions with thatched roofs or dry grass areas;
· Plastics and paints produce poisonous fumes when burnt at low temperatures.


INCINERATOR FOR SMALL HEALTH CENTRE

Resource recovery

The final option, resource recovery, is of great potential for developing countries and can be practiced at the community level. This approach is, therefore, explained in detail in the following chapter.

QUESTIONS:

1. In the disposal of refuse, what should the community undertake in co-operation with the municipality and what can it solve atone?

2. If municipalities will have towered costs and reduced volume in waste disposal, owing to community participation, what can the community demand in return?

· Expenses of transfer depots;
· Sorting equipment;
· Market skills and selling points;
· Cleaning of depots;
· Supply of dustbins/vehicles;
· Wages of collectors, cleaners, transporters;
· Price guarantees for recycled materials;
· Elimination of taxes;
· Land for commercial waste-related activities.

TASK:

Design a composting area in an urban context. Calculate the amount of organic matter and allow for a two-month composting period, using:

(a) The Chinese method;
(b) The ridge method.

Include transport, storage, sieving, packing etc.

QUESTIONS:

1. What will be the economic incentive for the population to separate waste at the household level?

2. What would be the best location of the transfer depot in the settlement area?

3. If selling/buying depots are set up in a settlement, how would it be possible to discourage or incorporate freelance scavengers whose operations would otherwise reduce the economy of the selling/buying points?