Re-Drawing the Waste Disposal Preference Hierarchy Chart

By Olubukola Betty Olatoye
September 2009

The Author is a Project Coordinator with Berthys Easy Everyday Konsult in Sango-Ota, and a Fellow Member of the Institute of Chartered Chemists of Nigeria. → See also:

This research work identified waste segregation at source as a major step towards attaining waste recovery, which normally give rise to waste Reuse or Recycle. This, if considered will assist in ensuring that proper waste management method that will help to achieve minimal waste throw-away is adopted within various waste production systems. The incorporation of waste segregation at source into the waste disposal hierarchy will make it possible to do this, since it has been established by many researchers and authors that waste reuse and recycling is most significant in the proper management of wastes.

List of Acronyms and Abbreviations

SWSolid Waste
SWMSolid Waste Management
HCWHHealthcare Without Harm
INTOSAIInternational Organization for Supreme Auditing
MECPCMaster in Environmental Chemistry and Pollution Control
MIPANMember Institute of Public Analyst of Nigeria
MICCON     Member, Institute of Chartered Chemist
MNISPMember Nigeria Institute of Safety Professionals

Background of the Study

Technological advancement brought along the negative aspects of pollution, health, safety, environment and security problems in different dimensions (NISP/SHELL Manual, 2003).

Environmental problems are often particularly difficult to resolve due to its interrelation with other social issues. Other factors like employment levels, profit and environmental quality are closely associated and complex, thus arriving at solutions appears very difficult (Enger and Smith, 1992).

Normal economic forces was also observed to work against pollution control because it encourages cheaper methods resulting in greater gain but also unmanaged pollution, due to the preferred option of dumping wastes into rivers and other available places rather than installing a waste treatment facility. Though it is unreasonable to expect a totally unpolluted environment, and to hold the view that the natural resources have unlimited capacity, the equilibrium ethic view of a balance between total development and absolute preservation should be upheld (Enger and Smith, 1992).

It may not be possible to stop man from performing his different activities in an environment, the onus however lies on him to effectively control the nuisance emanating from such activities (Uchegbu, 2002).

Environmental Problems

The focus of this project is on how to be able to find reasonable and lasting solution to waste disposal method that will be adopted in various sectors where wastes are being generated, and has been bringing about improper or non-implementation of Sustainable Waste Management in the past.

Environmental Problems in Brief

When air emission, water effluent discharge and solid waste are discharged into an environment by anthropogenic activities, the particles from the air eventually settles onto soil, plants, house roofs, water and some inhaled by humans, and animals (Enger and Smith, 1992). The various components of the liquid effluent also gradually collects on soil, some are transported to other locations and penetrate the soil through percolation, eventually leading to the contamination of the surface and underground water (Umeh and Uchegbu, 1997).

In the same vein, the solid wastes also contaminates in this manner, by the dissolution, disintegration and biodegradation of their components. In addition to this, both the biodegradable and non-biodegradable parts of the solid wastes creates further nuisance, emits foul odour and serves as homes for disease-causing and disease-carrying organisms, vectors, rodents and bacteria, thereby bringing about various kinds of epidemic emergency situations in plants, animals and humans that comes in contact with them. All these make it important for legislative regulations to be formulated for environmental management by all stakeholders. The hazardous ones are dangerous to the health of living things generally and also to many non-living but useful components of the environment. The low biodegradable ones stays in the environment for long and continue to cause health and environmental problem before they finally degrade. The resulting problems ranges from making the ecosystem becomes imbalanced to shortening the life span of living things that come in regular contact with them, bringing about monumental losses (Umeh and Uchegbu, 1997).

According to Enger and Smith, (1992) the solid wastes generated in some part of Iowa was explored for conversion to a source of energy, but the idea was discouraged by the associated problems of cost of collection of solid wastes, the availability of an adequate supply of the solid waste in areas where the conversion plant is situated and the cost of technical problems involved in the construction and operation of plants that will eventually make use of this form of energy generated from solid waste as well as availability of markets for sales of other sorted portions of the waste, if this area is properly investigated, for use as an alternative source of generating energy, it may alleviate the problem of land to store large chunks of solid wastes, ameliorate energy production in localized areas and reduce the underlying problem of environmental medium contamination and pollution.


Is any substance or object which is supposed to be disposed or which is required to be disposed by the provisions of law. It can also be defined as products arising from human and animal activities that are discarded because they are no longer useful; they can be solids, liquids or gases (Uchegbu, 2002B). Wastes can also be substances or objects, which the holder discards or which are intending to be discarded by the holder. Wastes are also substances that cannot be put into further use, it is any material that is intended for disposal.(Basel convention proceedings, 2004). Though the Basel report made two main distinctions of wastes as general and hazardous wastes, it however listed about 47 categories of hazardous wastes under which many types of wastes generated within the health care sector falls.

According to the Economists “wastes are material or substance, which is easier to throw away than to make further use of” (OECD, 2000).

National Waste Classification System

Wastes can be conveniently grouped accordingly using the following parameters:

Waste origin, waste form, legal definitions, industries generating the waste, process generating the waste, waste standard description or main or detailed compositions, waste properties, and label (INTOSAI, 2007). Some of the characteristics considered are found using mostcommon parameters like; Hazardous properties, Chemical and physical properties, Organic/inorganic, Generator, Composition. Usually, the authorities regulate waste more strictly than products, especially when waste is to be moved from one country to another. If a use can be found for a substance that has hitherto been treated as waste, the holder of the waste can face major difficulties in convincing the competent authorities that the substance is no longer waste, but a product that should be moved freely without restrictions however because of the various international laws available for officials and all stakeholders to use during decision making, some almost expired products which some waste generators intend to tactically export can be refused approval.

Classification of wastes can also be based on the composition and chemical or physical properties, depending on position of the decision maker, in the waste scenario, some waste definition and categorization will be more important than others, however for legislators, the distinction between hazardous and non-hazardous waste may be one important parameter, since legislation regarding hazardous waste is usually stricter than for non-hazardous waste. For a treatment plant, composition may be more important, simply because some types of waste are not treatable in that specific plant (INTOSAI, 2003).

International Classification Standards

In the 1980s, two international organizations developed classification systems for hazardous waste; they are the Basel Convention ( and the OECD (

The Basel Convention is an international diplomatic convention that has been ratified by most countries in the world and has thus become a de jurors standard. The convention governs international transport and disposal of hazardous waste and includes a list of 45 waste streams ("Y-numbers") and hazardous constituents that should be controlled.

OECD (The organisation for economic co-operation and development) is an international organisation that helps governments tackle the economic, social and governance challenges of a globalised economy. OECD has established a far more extensive list, which also includes non-hazardous waste.

With reference to traffic lights, waste is divided into three categories; green, amber and red. The green list includes non-hazardous waste products such as paper, plastics, glass and metals in their reduced state. The amber list includes most hazardous waste, while the red list is reserved for highly hazardous waste such as PCB, PCT, asbestos and lead containing anti-knock fuel additives. It is noteworthy to state that for a material in waste to be included in the green list, it has to be in a non-dispersible state. This means that powder and liquid or solutions may be considered hazardous even if the solid material itself is not hazardous. The Physical or chemical hazardous properties of some types of waste can be harmful to people, living organisms and/or the environment. For example, materials, which are flammable, toxic, explosive, corrosive, ecotoxic and infectious are classified as hazardous wastes.

Wastes Categorizations

The NISP/SHELL contractors training manual, (2003) made the following definitions for various categories of wastes.

Biological waste
That can biodegrade by the action of microorganisms e.g. wastes from man, animal, food processing, plants, abattoir, foods and beverages companies’ liquid effluents.
Non-Biological Waste
From non-biological matter, steel works, glass factories, construction sites, petrochemical plants, plastics and paint industry.
Gaseous Wastes
Particulates and other emissions from gas flaring, V.O.Cs, stack waste gases, cement dusts, stone crushing particles, lime dust, powder producing company, asbestos dust, acid fumes, cigarette company wastes, vehicle exhaust waste, cigarette smoking flames, generating plants and machineries in industries.
Liquid Wastes
Wastes in liquid form, containing both organic and inorganic compounds, dissolved and insoluble components and constituting the solution treated or untreated before eventual release into the public drain that will find its way into the streams, rivers and oceans.
Solid Wastes
This category include municipal garbage, refuse, sludge from water treatment plants and public drain packing, as well as all solid materials generated from industrial, commercial, mining, agricultural operations and households communal activities, this comprises of waste slags, broken bottles and other items, can, paper, wrappers, rags, kitchen remnants, fish and meat, inedible parts, etc.
Domestic Wastes
These are wastes from homes.
Commercial Wastes
Are wastes from markets, abattoirs, filling stations, guesthouses, restaurants and hotels etc.
Municipal Wastes
Are wastes from road cleaning, public drains, and from those removed from homes and commercial places like markets, abattoirs, and other commercial generators.
Industrial Wastes
Wastes from industrial activities.
Hazardous Wastes
Are wastes that are dangerous to human health, other organisms and the environment, they are usually very toxic, corrosive, reactive, explosive or ignitable and capable of causing diseases. They are usually treated further to a safe state before disposal. They can be further differentiated as dangerous, infectious, carcinogenic, radioactive or nuclear wastes e.g. hospital wastes, inflammable liquids, leaded sludge, pesticides, wood, pulp and paper industries wastes with sulphite preservatives, photographic wastes with cyanides, laboratory wastes, wastes of toxic chemicals and spent oils from generating sets. (Oshibanjo, 2004).
Non-Hazardous Wastes
They are not harmful to human, animal or plants but they however constitute a nuisance and can degenerate to hazardous waste. They also harbor diseases and vectors and some affect the ozone layers thereby bringing about more exposure of inhabitants to UV rays.

According to the wikipedia encyclopaedia website accessed in October, under the municipal solid waste definitions, wastes are categorised as follows:

Industrial Solid Waste
Wastes resulting from a variety of industrial processes, that is a process where a new, physical product is manufactured from a set of input materials. Mining and electric power generations are usually included in the industrial category for the purpose of classifying solid waste.
Residual Solid Waste
Is a subset of industrial wastes that many U.S. States regulate separately from miscellaneous industrial waste. Residual wastes are wastes or "residue" that are left over from a specific process. Residual wastes tend to be fairly homogenous in composition, have a relatively lower environmental impact compared to most industrial solid wastes. Residual wastes often have a mineral composition. One example of a residual waste is Flue Gas Desulphurization (FGD) waste from elecric power generation. Because residual wastes are fairly consistent, many states allow the generators of these wastes to dispose of them in captive landfills that are designed only for that particular residual waste.
Construction and Demolition Debris (C&DD)
As the name suggests, waste that are the result of the construction and/or demolition of roads, buildings or other physical structures. Traditionally these wastes are allowed to be disposed in their own class of landfills because it was believed that they did not pose a serious threat to the environment. Construction and demolition debris landfills were constructed using less stringent standards than general solid waste landfills however, abuses of the system and new data showing adverse environmental impacts from C&DD landfills, have led to increasing regulations on the disposal of C&DD.
Infectious Wastes
May include things like hospital waste, animal carcassas, or any other waste with the potential to spread infectious diseases.
Asbestos Wastes
Many people are suprised to find that many States do not regulate asbestos the way they regulate most other hazardous wastes, this is because asbestos is fairly inert, chemically, and when buried in the ground poses a minimal environmental threat. In fact, asbestos was commonly used to filter beer in the brewing industry. The primary health threat from asbestos comes from inhaling the microscopic fibers deep into the lung tissue and mesothelium Since the airborne threat is contained once asbestos is buried, many states allow asbestos to be disposed in landfills with general solid waste, provided the waste is handled with extra safety procedures, this is also the practice in Nigeria. 
Are residues from the burning of wood, charcoal and coke for cooking and heating in houses, institutions and small industries. Ashes consist of a fine powdery residue, cinders and clinker, often mixed with small pieces of metal and glass.
The remaining part of the solid wastes produced from households, commercial establishments and institutions are called rubbish.
Bulky Wastes
Are large household appliances such as cookers, refrigerators and washing machines as well as furniture, crates, vehicle parts, tyres, wood, trees and branches. The bulky metallic wastes are sold as scrap metal but some portion is disposed in sanitary landfills.
Street Wastes
This includes paper, cardboard, plastic, dirt, dust, leaves and others.
Slaughter House wastes
This includes liquid and solid wastes; it consists of non-edible organs, stomach contents, dung, bones and sludge from wastewater treatment.
Hospital wastes
These are generated wastes during the diagnosis, treatment immunization of human beings or animals. It may include wastes like sharps, soiled materials, disposables, anatomical wastes, cultures, discarded medicines, chemical wastes etc. the wastes are in the form of disposable syringes, swabs, bandages, body fluids, human excreta, etc. this waste is highly infectious and can be a serious threat to human health if not managed in a scientific manner. It has been roughly estimated in India that of the 4kg of waste generated in a hospital, at least 1kg would be infected waste (i.e. 25%).
Bio-medical Wastes
These are any solid and/ or liquid waste including its container and any intermediate product, which is generated during the diagnosis, treatment or immunization of human beings or animals or in research pertaining thereto or in the production or testing thereof. Biomedical waste consists of human anatomical waste like tissues, organs, body parts, animal wastes generated during research, from veterinary hospitals, microbiology and biotechnology wastes, waste sharps, hypodermic needles, syringes, scalpels, broken glass, discarded medicines and cyto-toxic drugs, soiled waste such as dressing, bandages, plaster casts, material contaminated with blood, tubes, catheters, liquid waste from any of the infected areas, incineration ash other chemical wastes.
Table 1 · Waste Categorization by Delta Environmental Logistics Ltd 2004
Class Waste Group Examples of Waste
A Mineral waste, oil with less than 1% Halogens and Sulphur Diesel oil, Fuel oil, Spent lubricants, oil filter
B Organic Chemical waste with Halogen and Sulphur Chloroform, freon, tetrachlo, Tirchlor, transformers, PVC waste
C Liquid Organic Chemical waste without Halogen, with high Calorific value Acetone, Alcohols, Benzene, Vegetable oils etc
D Drill cuttings OBM cuttings and OBM sludge
H Organic Chemical waste without Halogens and Sulphur. Paints, Oil emulsion organic acids etc
M Waste containing Mercury Batteries, Fluorescent tubes
T Water containing Pesticides Insecticides, Fungicides
X Inorganic Chemical waste Acids, Inorganic Salts
Z Inorganic Chemical waste Clinical, Medical wastes, Batteries, Packages, tyres, NORM, Printer cartridges

Fig 1
Fig 1 · Hierarchy of Waste Management Treatment Options

Waste Reduction

Source Reduction involves the use of materials cautiously to eliminate wastages to as low as practicably possible. It can also be done by reducing the amount made available for the production of a product or for use during any activity like while treating and attending to patients in the Hospital.

It is a management style that ensures more efficient practice, by eliminating excessive use of materials, applying proper control of inventory, improving facility monitoring and management, Incorporating new materials to substitute for material that is being excessively wasted and finally by improving housekeeping. (Delta Environmental Logistic Ltd. 2004; Uchegbu, 2002; Opara, 2002; Uchegbu, 2002B).

Waste Recovery for Reuse and Recycle

Waste Recovery is the process of getting back part of a waste stream.


Waste Recycling is done where it is sure that there is no heavy metal contamination and also if there are no biological contaminations, then part of the waste can be recovered via sorting (separation into components after generation) or segregation (separation into components as it is being generated using color coded containers or labeled containers at source) and converted to usable materials for use in another production process as raw material. e.g. food wastes used as Compost or manure for use as alternative to chemical fertilizers in farms i.e. as raw material for another production (Uchegbu, 2002B). (Note, recovery can be done by extraction too, if dealing with liquids before recycling in another process.)


Having ensured that no form of contamination exist in the waste, the waste recovered via Extraction, Sorting or Segregation can then be reused for the same production purpose (Uchegbu, 2002B).
Also extraction can help to recover part of the wastes for reuse as energy.

Waste Management

Combining the definitions of Alo, (2006) and Osibanjo, (2003) waste management is the various activities from generation of waste to final disposal. It involves, strategic measures taken in the generation, characterization, quantification, storage, handling, collection, transportation, and disposal of wastes. It also covers managerial, technological and remediation measures involved in the corrective actions of existing waste practices as well as the continuous plan towards ensuring sustainable waste management within a locality e.g. Hospital Waste management in Lagos metropolis.

Elements of Waste Management Principle

Inventorization, Minimization, Composition, Segregation, Sorting, Waste Disposal, Treatment, Reduction, Recover (Recycle and Re-use), Sustainable Waste management, Hierarchy of Waste Management Options.

Environmental Effect of Improper Management of Wastes

When air emissions, water effluent discharges and solid wastes are discharged into the environment, the particles from the air eventually settles onto soil, plants, house roofs, water and some inhaled by humans and animals while some are transported far away from the source of pollution, the various components of the liquid effluent also gradually collects on the soil, transported to other locations and penetrates soil through percolation, all these also leads to the contamination of the surface and underground water.

In the same vein, the solid wastes also contaminates in this manner, by the dissolution, disintegration and biodegradation of the components, in addition to this, the solid wastes emits foul odour and serve as homes for diseases causing vectors, rodents and bacteria, thereby bringing about various kinds of epidemic emergency situations in plants, animals and human that comes in contact with them. Water, Air and Soil pollution makes these chemicals to enter the water cycle, food chain, bioaccumulate in humans and other living organisms especially those consumed eventually by man, making it possible to cause cancer and many other life reducing diseases. It also pollutes the environment leading to erratic weather conditions, heat waves, ozone layer depletion, melting of Arctic and the Antarctic ice, bringing about imbalances in the various ecosystems (Uchegbu, 2002, 2002B; Opara, 2002).

Waste Disposal Practices in Nigeria

The following are methods of disposal presently being operated in Nigeria; Open air burning, available land dumping, public drain dumping, approved dumpsites dumping, incineration, non - separation or non -segregation, segregation, waste Audit, recycling, reuse, sorting (UNEP- Chemical, 2002; Basel, 2004; LAWMA, Bulletin, 2007).

Research Work on Waste Management

ADB, 2006 worked extensively on solid wastes and recommended waste segregation in many areas. INTOSAI, 2003 worked on various categories of wastes and recommended waste segregation to ensure reduction of waste finally disposed.

From the study of the literature review, it can be deduced that reuse and recycling were seen as positive and important waste management measures, recommended in all areas where wastes are generated, be it in the domestic, production or service provision sectors.

Though waste reduction was mentioned, however, much emphasis was not placed on it, irrespective of its hierarchy in the waste treatment available methods. Segregation, at source was the major method recommended for HCWM according HCWM draft, 2007, while sorting after generation was also encouraged for some type of waste; Domestic and Industrial waste, when it is known to be safe to do so ADB, 2006.

Fig 2
Fig 2 · The Waste Hierarchy
for Proper Waste Disposal

Segregation at source was the major method for achieving reuse and recycling as well as other appropriate waste recovery measures. In view of this, it can be proposed that segregation at source, being the major route towards achieving waste reuse and recycling should be incorporated into the waste treatment hierarchy as well as sorting.

The following are summaries of advantages of waste segregation at source as compared to source reduction;

Source segregation helps to generate revenue and the effect is easily quantifiable, whereas source reduction cannot accurately help to reduce cost of production, running a system or cut in domestic spending.
The hierarchy of waste figure can thus be drawn as shown on figure 2.


Waste management to ALARP is important to achieve appropriate management system, incorporating waste segregation into the waste disposal preference hierarchy will assist in explaining the best practicable option to adopt in specific system.


Official waste audit should be undertaken and training of environmental and waste auditors should be undertaken. Implementation, monitoring and evaluation of the WM plan must be thought of along with the policy formulation. Professionals should be consulted or employed during the formulation, implementation, monitoring and evaluation processes. Consideration for environmental issues should be the major factor that managers should use while choosing a management style. Professionals must be assigned to monitor waste in Facilities to be able to discover lapses. Monitoring of the Wastes using a cradle-to-grave method is the generally practiced and acceptable norm that must be followed. Waste that can be recycled are generated within many facilities and segregation at source should be made obligatory to be able to estimate the various wastes categories generated within a system especially the recyclable portion. Various methods of waste recycling (like waste-to-energy, LFG exploitation and Organic fertilizer production from some types of wastes) should be explored.

International standards relevant to the management of waste within and outside the African setting should be consulted to be able to adequately address WM issues. Monitoring of transit point to prevent illegal access to wastes should be done to prevent health and environmental hazards incidences.

For effective management the cooperation among waste generators and environmental agencies with coordination among the various persons and corporate bodies involved in the control of waste activities must be established. Governments at national, state and local levels need a comprehensive guideline on solid waste management; currently the policy in existence is not adequate and specific enough. A nationwide consultation which, may start from individual states that will address waste management issues should be organised to give room for the various concerned stakeholders to list and analyse the impacts of improper was management and proper mitigation measures for the country. Extensive research on waste and waste management should be funded at various levels and done for adequate period to be able to have reliable data bank that will be useful for effective management of the generated wastes. Curriculum of various categories of students should contain WM topics, while staff training on a post-graduate course on WM should be sponsored. Combination of available treatment technologies should always be explored for proper waste management and treatment before final collection at the transit point by LAWMA officials and before final disposal into landfills.

Due to the non-static nature of man, free will is very difficult to change, thus gradual readjustment will be needed to convince workers to adjust to a particular type of waste management method, which is not time or cost effective, trying to get people to obey instruction may be difficult to implement and monitor, but proper monitoring and training can help to achieve this faster, especially when workers know the cost reduction inherent in proper segregation, which will not involve jeopardizing their health status as in the case when trying to reduce materials used and is not clearly possible when using a source reduction method that cost will be reduced in a service and sales environment as compared to a production setting. This situation is compounded with the multi-dimensional facet of environmental issues that need the various inputs of seasoned professionals in varieties of interconnected professions, following the waste hierarchy in a dogged way may thus draw back proper waste management, because the peculiarity of a particular system must be considered before making decision of recommending the most appropriate waste management method. Finally, segregation at source will help to get and identify recyclable generated wastes without contamination, which will in turn be used to generate revenue in a safe waste-to-wealth collaborating venture.



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