"Sustainable Management of Waste"
Management of solid waste may be defined as the control of generation, segregation, storage, collection, transfer and transport, processing, and disposal of waste based on scientific principles. This includes all technological, financial, institutional, and legal and policy aspects involved for solving the whole spectrum of issues related with solid wastes. The term ‘waste’ usually relates to materials produced by human activity, and the process is generally undertaken to reduce their effect on the health and environment. Waste that is not properly managed can create serious health or social problems in a community
In many countries, solid waste management has become a top priority. Solid Waste Management (SWM) is a system for handling of all type of garbage. The end goal is to reduce the amount of garbage clogging the streets and polluting the environment. Climate change and effects of greenhouse gas emissions have made SWM, one of the most pressing environmental challenges globally as well as locally. It is well understood that inappropriate SWM practices, such as improper incineration and uncontrolled disposal of wastes are major contributors to greenhouse gas emissions.
Urban India generates about 47 million tons of solid waste (garbage) every year or about 1.3 lakh tons every day, according to a study by the Central Pollution Control Board (CPCB).
Based on the source of generation, solid waste can be classified into residential, commercial, institutional, industrial, agricultural etc. There are mainly two categories of wastes based on the type-biodegradable and non-biodegradable. This classification is based on physical, chemical and biological characteristics of wastes. Biodegradable wastes mainly refer to substances consisting of organic matter such as leftover food, vegetables and fruit peels, paper, textile, wood, etc, generated from various household and industrial activities. Because of the action of micro-organisms, these wastes are degraded from complex to simpler compounds. Non- biodegradable wastes consist of inorganic and recyclable materials such as plastic, glass, cans, metals, etc.
There are various functional elements associated with the management of solid wastes such as segregation, collection, transportation, processing and disposal which are given below:
Waste generation: Wastes are generated at the start of any process, and thereafter, at every stage as raw materials are converted into goods for consumption. The source of waste generation determines quantity, composition and waste characteristics.
Waste storage: Storage of waste after collection and before transportation to the processing/disposal site is an important functional component. The time of storage depends on the type of waste. For example, the biodegradable waste cannot be stored for long in a storage container because of its putrescible nature. There are many options for storage like plastic containers, conventional dustbins (of households), used oil drums, large storage bins (for institutions and commercial areas or servicing depots), etc.
Waste collection: Collection refers to mainly two aspects; collection from the source of generation to the next collection point and collection from that point to the large vehicles for transportation or to the transfer stations and finally to the processing plant/disposal area. Collection depends on the number of containers, frequency of collection, types of collection services and routes. Collection is done either directly through the municipal services to franchised services or contracts. Recently, collection of waste from the source to the next step is carried out by Self Help Groups (SHGs) in many cities in India, which is very common in the state of Kerala.
Transfer and transport: This functional element involves transfer of wastes from smaller collection vehicles to larger ones at transfer stations and the subsequent transport of the waste to disposal sites
Processing: Processing of waste is the most important functional component of SWM system, which leads to various types of resource recovery, recycling, energy generation, production of organic manure, etc. There are many processing techniques, which will be discussed in detail later.
Disposal of final rejects: Disposal of final rejects after resource recovery is one of the important functional components of SWM system. This is mainly achieved through construction of engineered sanitary landfill. Engineering principles are followed to confine the wastes to the smallest possible area, reduce them to the lowest particle volume by compaction at the site and cover them after each day’s operation to reduce exposure to vermin.
Solid waste composition
Climate has a major influence in SWM planning. In cold climates like in Srinagar, Shimla etc, drifting snow and frozen ground interfere with landfill operations, and therefore, trenches must be dug in summer and cover material stockpiles for winter use. Tropical climates, on the other hand, are subject to sharp seasonal variations from wet to dry season, which cause significant changes in the moisture content of solid waste, varying from less than 50% in dry season to greater than 65% in wet months. Collection and disposal of wastes in the wet months are often problematic. High temperatures and humidity cause solid wastes decompose far more rapidly than in colder climates.
In India usually a community storage system is practiced where individuals deposit their waste in bins located at street corners and at specific intervals. The containers generally are constructed of metal, concrete, or a combination of the two. Community storage may reduce the cost of waste collection, and can minimize problems associated with lack of onsite storage space. However, unless these community storage arrangements are conveniently located, householders tend to throw their wastes into the roadside gutters for clearance by street sweeping crews. Even where storage arrangements are conveniently located, wastes tend to be strewn around the storage area, partly due to indiscipline and partly as a result of scavenging of the wastes by rag-pickers and stray animals.
Commercial sector like shops, offices, hotels, etc. all use the community waste bins in most of the places and their wastes are also collected along with the household wastes except in a rare number of commercial complexes where they pay a negotiated fee to the Municipal Authorities for collecting waste from their premises.
The larger proportion of organic matter in MSW indicates the desirability of biological processing of waste. Though composting was a prevalent biological processing practice in India, in the past due to non-availability of adequate space in the urban centers and poor segregation of wastes, composting has been discontinued as a practice. Recently efforts are being taken to popularize waste segregation and composting.
Waste management is now gaining the importance it deserved from the policy makers because of its significance in making the quality of life better particularly at urban centers. The Ministry of Urban Development (MoUD) has approved a project to Centre for Environment and Development to set up a Centre of Excellence (CoE) on ‘Solid Waste and Waste Water Management ’. The basic objective was to develop the capacity of the institution to support the Urban Local Bodies (ULB) in the country on solid waste and waste water management related activities. The CoEs will work with selected ULBs to develop strategies and framework to implement activities.
At present three important concepts have emerged in the waste management-
1) Waste hierarchy - The waste hierarchy refers to the "4 Rs" concept (reduce, reuse, recycle and recover), which classify waste management strategies according to their desirability in terms of waste minimization. It remains the keystone of most waste minimization strategies. The main aim is to extract the maximum practical benefits from products and to generate the minimum amount of waste.
2)Polluter pays principle - It is a principle where the polluting party pays for the impact caused to the environment. Here, it refers to the requirement for a waste generator to pay for appropriate disposal of the waste.
3)Extended producer responsibility – EPR is a strategy designed to promote the integration of all costs associated with products throughout their life cycle (including end-of-life disposal costs) into the market price of the product. This means that firms which manufacture, import and/or sell products are required to be responsible for the products after their useful life as well as during manufacture.