Waste Generation 01

Waste Generation

Presently in India, about 960 million tonnes of solid waste is being generated annually as by-products during industrial, mining, municipal, agricultural, and other processes. Of these ∼350 million tonnes are organic wastes from agricultural sources; ∼290 million tonnes are an inorganic waste of industrial and mining sectors and ∼4.5 million tonnes are hazardous in nature. Advances in solid waste management resulted in alternative construction materials as a substitute for traditional materials like bricks, blocks, tiles, aggregates, ceramics, cement, lime, soil, timber, and paint.

To safeguard the environment, efforts are being made for recycling different wastes and utilize them in value-added applications. In this paper, present status on generation and utilization of both non-hazardous and hazardous solid wastes in India, their recycling potentials, and environmental implication are reported and discussed in detail.

Factors Affecting Waste Generation

Hierarchy of waste management

In this hierarchy first preference is given to waste reduction/generation and least preference is given to Disposal without processing.

1.   Waste Minimization

• It is the most desirable activity, Because the community doesn’t incur expenditure for waste handling, recycle and dispose of waste that is never created and delivered to the waste management system.
• Waste can be minimized by-
• Adopting industry standards for manufacturing and packing by using less material.
• Passing of laws to minimize the use of VIRGIN materials in consumer products.
• Levying of fees for SWM services.
• Penalties for over a waste generation.
• Using of virgin materials encourage recycling. (E.g.: Soda Bottles)
• Sorting of waste at onsite reduces rejects.

2.   Recycling/Sorting

• Dry Recycling materials.
• Biowaste and garden waste
• Bulky waste
• Hazardous material in the Household waste
• Construction and Demolition waste
• Commingled Municipal Solid Waste

Centralized Sorting

• Hand sorting (Rag Pickers) in INDIA.
• Mechanical sorting by Magnetic & Electric Field separation
• Density separation
• Size separation

In Case of manual sorting, care must be taken to ensure that sorters are protected from all disease pathways and work in hygienic conditions.

3.   Processing 

Rejects from recycling are sent for Biological or Thermal treatment, which will yield

• Gas or
• Energy or
• Compost

Municipal SW with more calorific value is generally treated by thermal process to yield high energy.

4.   Transformation

After processing rejects are subjected to following transformation process,

1. Mechanical Transformation
2. Shredding
3. Composting
4. Thermal Transformation
5. To reduce volume
6. Detoxification Transformation-
7. Autoclaving
8. Hydroclaving
9. Microwaving
10. Encapsulation
11. Chemical

5.   Disposal

Waste i.e. final rejects are disposed as landfills.

Solid Waste Generation Rate

• Determination of the generation rate of solid waste is important to obtain data in order to determine waste volume and for subsequent solid waste management.
• Factors to consider for the purpose of determining the solid waste generation rate are:

1. Measures of Quantities

2. Statistical Analysis

3. Expression of Unit Generation

4. Methods Used to Determine Generation Rate

5. Typical Generation Rate

6. Factors Affecting Generation Rates

1. Measures of quantities

(1) Volume measurement

(2) Weight measurement

Be careful in volume measurement because we need to distinguish wastes which are compacted and loosened.

Volumes must be related to either degree of compaction of the waste or the specific weight of the waste under the conditions of storage.

Weight is the most accurate basis for records regardless of whether the waste is loose or compacted.

2. Statistical Analysis

It is necessary to have some statistical base for solid waste management

system development.

This includes placement of containers, programming the collection program

and allocation of vehicle type.

3. Expression of Unit Generation

In addition to knowing the source and composition of solid waste, it is

important to have uniform units of expression.

(1) Residential and Commercial – kilogram per capita per day (Kg/c/d)

(2) Agricultural –Kilogram per hectare per year (kg/ ha/ year)

4. Methods Used to Determine Generation Rate

(1) Load count analysis: Basically, involves counting of the individual loads and the corresponding waste characteristics (types of waste, estimated volume) over a specified time period. If possible, weighing the load will be very important.

(2) Weight -volume analysis: Measuring the volume of the truck and weight of each load will give ample data (specific weight of the various forms of solid waste).

(3) Material balance analysis: The technique is expensive; it is used to: draw a system boundary round the unit to be studied; identify what occurrences affect generation rates; identify the rate of generation associated with different activities using the data available; determine the quantity of waste generated, stored and collected.

5. Typical Generation Rate

This is the rate found by conducting a large survey very representative for a nation, state or locality.

6. Factors Affecting Generation Rates

Factors that affect the generation rate of solid waste include:

• geographical location – related primarily to the different climate that can influence both the amount generated and collection operation.
• season of the year
• frequency of collection
• characteristics of population
• extent of salvage and recycling
• legislation
• public attitude

Waste Composition

The composition of wastes includes the following:

• The major constituents are paper and decomposable organic materials.

• Metal, glass, ceramics, textile, dirt and wood form part of the composition and their relative proportion depends on local factors.

• Average proportions of the constituents reaching the disposal sites are consistent and urban wastes are fairly constant although subject to long-term consistent and urban wastes are fairly constant although subject to long-term changes such as seasonal variations.

Waste Composition

Physical Composition

Knowing the physical composition of solid waste is important for the selection and operation of equipment facilities, to assess the possibility or feasibility of energy recovery and to design disposal facilities.

Its analysis may contain individual component study, moisture content study and density.

Chemical Composition

It is very important to study the nature and value of solid waste to plan different disposal and recovery options.

These studies include the assessment of moisture content, volatility, ash content, etc. The moisture content of municipal solid wastes varies depending on the composition of the waste, the season of the year, humidity, and weather conditions.

Composition of solid waste depends on the local factors such astime of the year or season

• habits of the community
• educational status
• economic status
• geographical location and
• population size.