DISPOSAL OPTIONS AND SELECTION CRITERIA
The most common disposal option practised currently in many countries is either uncontrolled dumping or dumping with moderate control. The environmental costs of uncontrolled dumping include breeding of disease causing vectors (e.g., flies, mosquitoes and rodents), pollution, odour and smoke.
1 Disposal options
(i) Uncontrolled dumping or non-engineered disposal: As mentioned, this is the most common method being practised in many parts of the world, and India is no exception. In this method, wastes are dumped at a designated site without any environmental control. They tend to remain there for a long period of time, pose health risks and cause environmental degradation. Due to the adverse health and environmental impact associated with it, the non-engineered disposal is not considered a viable and safe option.
(ii) Sanitary landfill: Unlike the non-engineered disposal, sanitary landfill is a fully engineered disposal option in that the selected location or wasteland is carefully engineered in advance before it is pressed into service. Operators of sanitary landfills can minimise the effects of leachate (i.e., polluted water which flows from a landfill) and gas production through proper site selection, preparation and management. This particular option of waste disposal is suitable when the land is available at an affordable price, and adequate workforce and technical resources are available to operate and manage the site.
(iii) Composting: This is a biological process of decomposition in which organisms, under controlled conditions of ventilation, temperature and moisture, convert the organic portion of solid waste into humus -like material. If this process is carried out effectively, what we get as the final product is a stable, odour-free soil conditioner. Generally, the option of composting is considered, when a considerable amount of biodegradable waste is available in the waste stream and there is use or market for composts.
(iv) Incineration: This refers to the controlled burning of wastes, at a high temperature (roughly 1200 - 1500 C), which sterilises and stabilises the waste in addition to reducing its volume. In the process, most of the combustible m aterials (i.e., self-sustaining combustible matter, which saves the energy needed to maintain the combustion) such as paper or plastics get converted into carbon dioxide and ash. Incineration may be used as a disposal option, when land filling is not possible and the waste composition is highly combustible. An appropriate technology, infrastructure and skilled workforce are required to operate and maintain the plant.
(v) Gasification: This is the partial combustion of carbonaceous material (through combustion) at high temperature (roughly 1000 C) forming a gas, comprising mainly carbon dioxide, carbon monoxide, nitrogen, hydrogen, water vapour and methane, which can be used as fuel.
(vi) Refuse-derived fuel (RDF): This is the combustible part of raw waste, separated for burning as fuel. Various physical processes such as screening, size reduction, magnetic separation, etc., are used to separate the combustibles.
(vii) Pyrolysis: This is the thermal degradation of carbonaceous material to gaseous, liquid and solid fraction in the absence of oxygen. This occurs at a temperature between 200 and 900 C.
2 Selection criteria
With the help of proper frameworks and sub-frameworks, we can assess the effectiveness
of each of the waste disposal options. While a framework represents an aid to decision-making
and helps to ensure the key issues are considered, a sub-framework explains how and why the
necessary information should be obtained (Ali, et al 1999). A framework contains a list of issues and questions pertaining to the technical, institutional, financial, social and environmental features of a waste disposal system to assess the capacity of a disposal option to meet the requirements. For example, an appraisal of waste disposal option must include the following:
(i) Technical: This feature, involving ef fi c i en t and effective operation of the technology
being used, evaluates the following components of a SWM system:
omposition of wastes, e.g., type, characteristics and quantity.
Existing practices, e.g., collection, transport, and recycling process.
Siting, e.g., location of disposal site, engineering material, etc.
Technology, e.g., operation, maintenance, technical support, etc.
Impact, e.g., anticipated by-product, requirement for their
treatment and disposal, etc.
(ii) Institutional: This involves the ability and willingness of responsible agencies to
operate and manage the system by evaluating the following:
structures, roles and responsibilities, e.g., current institutional frameworks.
operational capacity, e.g., municipal capacities, local experience and staff training.
incentives, e.g., management improvement and waste disposal practices.
innovation and partnership.
(iii) Financial: This assesses the ability to finance the implementation, operation and
maintenance of the system by evaluating the following:
financing and cost recovery, e.g., willingness to raise finance for waste management.
current revenue and expenditure on waste management.
potential need for external finance for capital cost.
(iv) Social: This helps in avoiding adverse social impact by evaluating the following:
health and income implication.
public opinions on the existing and proposed system.
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