Disposal Options And Selection Criteria of Solid Waste

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.

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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.