i. Garbage:

It includes peels of fruit and vegetables, leftover food articles, garden litter, etc. It is organic in nature and can biodegrade quickly.

ii. Rubbish:

It includes waste paper, glass and pottery pieces, plastic goods, rubber goods, polythene bags, cloth rags, etc. These are mostly inorganic in nature.

iii. Ash:

It is the main source of solid domestic waste, which is generated due to the burning of wood, coal and dung cakes in the kitchen.

iv. Sewage:

It includes the waste water from kitchen and bathrooms.

Domestic waste is often seen lying in the streets and along the roads in heaps. This makes the environment unhygienic and it can be the breeding ground for mosquitoes and other harmful organisms. The per capita domestic waste in India is about 400 g per day, while it is more than 3000 g per day in the developed countries. In the rural and urban areas, the composition of domestic waste varies greatly.

2. Industrial Waste:

Almost all types of industries process raw materials to produce finished consumable goods. In this process any leftover material, which is of no use, is called industrial waste.

It includes general factory rubbish, packing waste, demolition and construction waste, damaged parts of machines and tools, etc. This can cause toxicity in the air, water and soil. It is harmful to human beings and the environment. The waste generated by some of the industries is given below:

i. The mining and metallurgical industries can generate coal ash, rocks of no value, furnace slag, metallic scrap, etc.

ii. The chemical industries generate acids, toxic gases, oils, alkalis, and many types of synthetic materials.

iii. The main waste material from oil refineries and petrochemical industries are petroleum gases, hydrocarbons, oils and other toxic organic chemicals.

iv. The cement factories generate suspended particulate matter (SPM) in the form of coarse and fine particles, which can pollute the air. This can cause respiratory disorder.

v. The waste from the industries are cellulose fibre, paper scraps, bleaching powder, alkalis, etc. About 40 per cent wood or bamboos used in the paper mills generally go waste.

vi. The construction companies use a variety of construction material like cement, sand, bricks, stone, wood, limestone, etc. for construction of buildings. The waste is released in the form of debris.

3. Agricultural Waste:

The waste generated during the various processes of crop production and livestock rearing is called agricultural waste. It is generally of the following types:

i. Plant remains:

It includes husk and straw, wood and rubber waste, cotton and tobacco waste, coconut waste products, nutshells, etc. These are common plant remains or crop residue produced during agricultural practices.

ii. Animal waste:

Heaps of animal waste (excretory) that are left unattended emit a foul smell and are the breeding ground for many harmful microorganisms. Managing the huge amount of animal waste generated in rural areas is a major task.

iii. Processing waste:

Food crops are processed for the preparation of rice from paddy, flour from wheat and jowar, dal from pulses, edible oils from oilseeds,
etc. Huge quantity of husk and cakes are produced as waste. Improper handling may degrade the environment and harm the health of people involved in the process.

Agriculture includes ploughing, sowing, harvesting, threshing, winnowing, poultry farming, dairy farming, etc. Threshing and winnowing are waste generating activities of agriculture. Modern agricultural practices use chemical fertilisers, pesticides, insecticides, weedicides, fungicides and herbicides on a large scale to enhance crop production. Excessive use of agrochemicals is harmful for crops and environment.

4. Municipal Waste:

The waste generated in a municipal area is managed by the Municipal Committee/Board/Corporation of the concerned area. It includes domestic waste, community waste and commercial waste. These are collectively called municipal solid waste (MSW).

The waste collected from educational institutions, hospitals, sweeping of the streets, lanes and roads are called community waste. Sewage is the foul smelling liquid material containing mostly waste organic matter from towns and cities which is carried off in the underground drains.

Commercial waste is generated from the business establishments, such as shops, offices, godowns, departmental stores, market, etc. They include packing materials, paper, spoiled or discarded goods, etc. The waste can be organic or inorganic. Fish and vegetable markets also generate large amount of waste every day.

5. Biomedical Waste:

The wastes generated from the medical activities are hazardous to human beings and the environment. Waste generated in hospitals, pathological laboratories, and clinics are called biomedical waste. They include syringes, needles, blades, scalpels, empty plastic bottles, polythene bags, gloves, tubes, expired medicines, pathological wastes (blood, tissues, body parts, and body fluids), waste from surgery and autopsy. They are both toxic and hazardous.

Biomedical waste-falls under two main categories infectious and non-infectious wastes. The infectious waste contains large number of pathogens. They are dangerous. Most biomedical wastes are non-infectious, which get mixed with infectious waste. Biomedical wastes are more hazardous than most of the other wastes.

6. Nuclear Wastes:

Radioactive wastes from the nuclear power and weapon industries a matter of great concern. The most important waste is the spent nuclear fuel, which is composed of unconverted uranium as well as Plutonium and other radioactive elements.

The waste remains radioactive for thousands of years. Sometimes radioactive materials leak from the nuclear plants in the case of accidents. There is no safe method for permanent disposal of radioactive wastes.