Waste Management, Types and Classification of Wastes
According to the Basel Convention, waste is defined as substances or objects which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of the law.
Waste is therefore known by several terms such as rubbish, trash, refuse, garbage, junk or litter that clearly suggest they are unwanted and useless. In reality, however, the term ‘waste’ is a subjective term true only to a specific individual, time and place.
This is because what is waste to a person, at a given time or place could be a valuable resource to another person at another time or place. There are many methods for waste management, some existing over a long period of time, others emerging.
The choice of a technique at any given time depends on several factors including type of waste involved, cost of management options and available technology, personnel and infrastructure required by each technique.
The available methods can broadly be divided into two categories, namely traditional and emerging methods. The traditional methods include indiscriminate disposal, open burning, composting, sanitary landfill and incineration while the emerging methods include those methods that lead to waste recycling, source reduction and bio-remediation of contaminated sites.
Types and Classification of Wastes
Waste is classified using several criteria. On the basis of state, waste could appear in the form of gas, liquid or solid while on the basis of fate, it could be bio-degradable or non-bio-degradable.
Biodegradable waste is further divided into compostable (materials that are easily broken down to smaller substances by the action of microorganisms such as bacteria e.g. food substances) and combustible (materials though could be broken down, the process of bacterial activity is very slow for which reason it is often preferable to burn them e.g. wood).
Non bio-degradable materials on the other hand are substances that cannot easily be broken down by bacterial activities. These are divided into recyclable (materials that can be reprocessed using existing technologies at an economic cost, e.g. metals, plastics) and non-recyclable (materials that cannot be reprocessed at any economic cost by available technologies, e.g. concrete).
Waste is also classified on the basis of risk they pose to health into hazardous and non-hazardous waste. Hazardous wastes are potentially dangerous and pose great threats to public health or the environment.
Waste is classified hazardous on the basis of its ignitability (i.e. flammable with a flash point less than 60° C), reactivity (unstable, generates toxic or explosive gases and / or liquids when in other substances), corrosivity (pH <2 or >12.5) and / or toxicity (contain contaminants that are harmful to human health and the environment).
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Examples include inflammable petroleum products, infectious waste, pathological waste, sharp objects, pharmaceutical waste, genotoxic waste, chemical waste, heavy metals, pressurized, containers, radioactive waste and thousands of specific substances listed by the US Environmental Protection Agency as hazardous substances under different codes.
Non-hazardous waste includes all other wastes not classified as hazardous irrespective of source. Examples include most degradable municipal waste.
