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The majority of household and veterinary practice waste is considered "solid waste," regardless of whether it's actually "solid" in physical form. The U.S. Environmental Protection Agency (EPA) defines solid waste as "any garbage or refuse, sludge from a wastewater treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including solid, liquid, semi-solid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, and from community activities." 

Solid wastes: - A "solid waste" is defined as any discarded material that is abandoned by being disposed of, burned or incinerated, recycled, or considered "waste-like." Solid waste can physically be a solid, liquid, semi-solid, or container of gaseous material. Solid waste includes garbage, construction debris, commercial refuse, sludge from the water supply or waste treatment plants, air pollution control facilities, and other discarded materials. Solid waste can come from industrial, commercial, mining, or agricultural operations, and from household and community activities. Solid waste does not include wastes such as solid or dissolved materials in domestic sewage, or source, special nuclear, or by-product material as defined by federal law. The management of solid waste can include source reduction, recycling, storage, collection, transportation, processing, and disposal.

As you can tell, "solid waste" is a broad category. It is further subdivided into subcategories as shown here.

 

In metro cities in India, an individual produces an average of 0.8 kg/ waste/ person daily. The total municipal solid waste (MSW) generated in urban India has been estimated at 68.8 million tons per year (TPY) (0.573 million metric tonnes per day (MMT/d) in the year 2008). The average collection efficiency of MSW ranges from 22% to 60%.

MSW typically contains 51% organic waste, 17%  recyclables, 11% hazardous, and 21% inert waste. However, about 40% of all MSW is not collected at all and hence lies littered in the city/town and finds its way to nearby drains and water bodies, causing choking as well as pollution of surface water. Unsegregated waste collection and transportation leads to dumping in the open, which generates leachate and gaseous emissions besides causes nuisance in the surrounding environment. Leachate contaminates the groundwater as well as surface water in the vicinity and gaseous emissions contribute to global warming.

Classification of Solid Waste: - Solid wastes are classified according to their sources and their types.

Commercial: This refers to solid waste containing leftover food, glasses, metals, ashes, etc, generated from stores, restaurants, markets, hotels, auto-repair shops, medical facilities, etc.

Residential: It includes solid waste from dwellings, apartments, etc… and it consists of leftovers such as food, fruit and vegetable peels, plastic, clothes, ashes, etc.

Municipal: This solid waste includes dust, leafy matter, building debris, treatment plant residual sludge, etc,  which is generated from various municipal activities such as construction and demolition, street cleaning, landscaping, etc.

Institutional: This type of solid waste mainly consists of paper, plastic, glasses, etc, which is generated from educational, administrative, and public buildings such as schools, colleges, offices, etc.

Open Areas: This solid waste includes waste from areas such as streets, alleys, parks, vacant lots, playgrounds, beaches, highways, recreational areas, etc.

Industrial: Solid waste mainly includes process wastes, ashes, demolition and construction wastes, etc, due to ongoing industrial activities.

Agricultural: Solid waste mainly consists of spoiled food grains and vegetables, agricultural remains, litter, etc, generated from fields, orchards, vineyards, farms, etc., etc

Ashes and Residues: These are the substances remaining from the burning of wood, coal, charcoal, and other combustible materials used for cooking and heating in houses, institutes, and small industrial establishments. When produced in large quantities, as in power generation plants and factories, these are classified as Industrial wastes. Ashes consist of fine powdery residue, cinders, and clinker often mixed with small pieces of metal and glass. Since ashes and residues are almost entirely inorganic, they are valuable in landfills.

Street Wastes: These refer to solid waste that is collected from streets, walkways, parks, and vacant plots which consist of paper, cardboard, plastic, leaves, and other vegetable matter. Littering in public places is indeed a widespread and acute problem in many countries. solid waste management must address this menace appropriately.

Garbage: This refers to animal and vegetable wastes resulting from the handling, sale, storage, preparation, cooking, and serving of food. Garbage comprising these wastes contains rotting organic matter, which produces an obnoxious smell and attracts rats and other vermin. Therefore, special attention is required in the storage, handling and disposal of this type of solid waste.

Bulky Wastes: These include large household appliances such as refrigerators, washing machines, furniture, crates, vehicle parts, tires, wood, trees, and branches. Since these household wastes cannot be accommodated in normal storage containers, they require a special collection mechanism.

Biodegradable and Non-Biodegradable Wastes: Biodegradable wastes mainly refer to substances consisting of organic matter such as leftover food, vegetable and fruit peels, paper, textile, wood, etc, which are 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. Below is the table showing the comparison between biodegradable and non-biodegradable wastes with their degeneration time. (Time required to break from complex to simple biological form ).

Combustible and Non-Combustible Wastes: These consist of waste generated from households, institutions, and commercial activities, excluding food wastes and other highly rotting materials. Typically, combustible materials consist of paper, cardboard, textile, rubber, garden trimmings, etc. Non-combustible materials consist of items such as glass, crockery, tin, aluminum cans, ferrous and non-ferrous materials, and dirt.

Abandoned Vehicles: This includes automobiles, trucks, and trailers that are abandoned on streets and other public places. However, abandoned vehicles have significant scrap value for the metal and their value to collectors is highly variable.

Dead Animals:  With regard to municipal wastes, dead animals are those that die naturally or are accidentally killed on road. Note that this category does not include carcasses and animal parts from slaughterhouses, which are regarded as industrial wastes. Dead animals are divided into two groups – large and small. Among the large animals are horses, cows, goats, sheep, pigs, etc. Small animals include dogs, cats, rats, etc. The reason for this differentiation is that large animals require special equipment for lifting and handling when they are removed. If not collected promptly, dead animals pose a threat to public health since they attract flies and other vermin as they decay. Their presence in public places is particularly offensive from an aesthetic point of view as well.

Farm Wastes: These wastes result from diverse agricultural activities such as planting, harvesting, production of milk, rearing of animals for slaughter, and the operation of feedlots. In many areas, the disposal of animal waste has become a critical problem, especially in feedlots, poultry farms, and dairies.

Hazardous Wastes: These solid wastes are defined as wastes of industrial, institutional, or consumer origin that are potentially dangerous either immediately or over a period of time to human beings and the environment. This is due to their physical, chemical, and biological or radioactive characteristics like ignitability, corrosivity, reactivity, and toxicity. Note that in some cases the active agents may be liquid or gaseous hazardous wastes. These are, nevertheless classified as solid wastes and they are confined in solid containers.

Typical examples of hazardous wastes are empty containers of solvents, paints, and pesticides. Certain hazardous wastes may cause explosions in incinerators and fires at landfill sites. Others such as pathological wastes from hospitals and radioactive wastes also require special handling. Effective management practices should ensure that hazardous wastes are stored, collected, transported, and disposed of separately, preferably after suitable treatment to render them harmless.

Sewage Wastes: The solid by-products of sewage treatment are classified as sewage wastes. They are mostly organic and derived from the treatment of organic sludge separated from both raw and treated sewage. The inorganic fraction of raw sewage such as grit and eggshells is separated at the preliminary stage of treatment. This is done so that it may entrain putrescible organic matter with pathogens and must be buried without delay. The bulk of treated, dewatered sludge is useful as a soil conditioner but is invariably uneconomical. Solid sludge, therefore enters the stream of municipal wastes, unless special arrangements are made for its disposal.

Solid Waste Management: - “Solid-waste management is the process of collecting, treating, and disposing of solid material that is discarded because it has served its purpose or is no longer useful. Improper disposal of municipal solid waste can create unsanitary conditions, and these conditions, in turn, can lead to pollution of the environment and to outbreaks of vector-borne disease—that is, diseases spread by rodents and insects.”

Solid waste management should be embraced by each and every household, including the business owners across the world. Industrialization has brought a lot of good things and bad things as well. One of the adverse effects of industrialization is the creation of solid waste.

According to Britannica,

“Solid-waste management, the collecting, treating and disposing of solid material that is discarded because it has served its purpose or is no longer useful. Improper disposal of municipal solid waste can create unsanitary conditions, and these conditions, in turn, can lead to pollution of the environment and to outbreaks of vector-borne disease—that is, diseases spread by rodents and insects.”

Every day, tonnes of solid waste are disposed of at various landfill sites. This waste comes from homes, offices, industries, and various other agricultural-related activities.

These landfill sites produce a foul smell if waste is not stored and treated properly. It can pollute the surrounding air and can seriously affect the health of humans, wildlife, and our environment. The following are major sources of solid waste:

Residences and homes where people live are some of the major sources of solid waste. The garbage from these places includes food wastes, plastics, paper, glass, leather, cardboard, metals, yard wastes, ashes, and special wastes like bulky household items such as electronics, tires, batteries, old mattresses, and used oil.

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Most homes have garbage bins where they can throw away their solid wastes and later, the bin is emptied by a garbage collecting firm or person for treatment.

Industries are known to be one of the biggest contributors to solid waste. They include light and heavy manufacturing industries, construction sites, fabrication plants, canning plants, power, and chemical plants.

These industries produce solid waste in the form of housekeeping wastes, food wastes, packaging wastes, ashes, construction and demolition materials, special wastes, medical wastes as well as other hazardous wastes.

Commercial facilities and buildings are yet another source of solid waste today. Commercial buildings and facilities, in this case, refer to hotels, markets, restaurants, godowns, stores, and office buildings.

Some of the solid wastes generated from these places include plastics, food wastes, metals, paper, glass, wood, cardboard materials, special wastes, and other hazardous wastes.

Institutional centers like schools, colleges, prisons, military barracks, and other government centers also produce solid waste. Some of the common solid wastes obtained from these places include glass, rubber waste, plastics, food wastes, wood, paper, metals, cardboard materials, electronics as well as various hazardous wastes.

Construction and demolition sites also contribute to the solid waste problem. Construction sites include new construction sites for buildings and roads, road repair sites, building renovation sites, and building demolition sites.

Some of the solid wastes produced in these places include steel materials, concrete, wood, plastics, rubber, copper wires, dirt, and glass.

The urban centers also contribute immensely to the solid waste crisis in most countries today. Some of the solid waste brought about by the municipal services include street cleaning, wastes from parks and beaches, wastewater treatment plants, landscaping wastes, and wastes from recreational areas, including sludge.

Heavy and light manufacturing plants also produce solid waste. They include refineries, power plants, processing plants, mineral extraction plants, and chemical plants.

Among the wastes produced by these plants, there are industrial process wastes, unwanted specification products, plastics, and metal parts, just to mention a few.

Crop farms, orchards, dairies, vineyards, and feedlots are also sources of solid waste. Among the wastes they produce are agricultural wastes, spoiled food, pesticide containers, and other hazardous materials.

This refers to hospitals and biomedical equipment and chemical manufacturing firms. In hospitals, there are different types of solid waste produced.

Some of these solid wastes include syringes, bandages, used gloves, drugs, paper, plastics, food wastes, and chemicals. All these require proper disposal or else they will cause a huge problem for the environment and the people in these facilities.

Due to improper waste disposal systems, particularly by municipal waste management teams, wastes heap up and become a menace. While people clean their homes and places of work, they litter their surroundings, which affects the environment and the community.

Improper waste disposal can affect the health of the population living nearby the polluted area or landfills. The health of waste disposal workers and other employees involved with these landfill facilities are also at a greater risk.

Exposure to wastes that are handled improperly can cause skin irritations, respiratory problems, blood infections, growth problems, and even reproductive issues.

This type of dumping of waste materials forces biodegradable materials to rot and decompose under improper, unhygienic, and uncontrolled conditions.

After a few days of decomposition, a foul smell is produced, and it becomes a breeding ground for different types of disease-causing insects as well as infectious organisms. On top of that, it also spoils the aesthetic value of the area.

Solid wastes from industries are a source of toxic metals, hazardous wastes, and chemicals. When released into the environment, the solid wastes can cause biological and physicochemical problems in the environment that may affect or alter the productivity of the soils in that particular area.

Toxic materials and chemicals may seep into the soil and pollute the groundwater. During the process of collecting solid waste, hazardous wastes usually mix with ordinary garbage and other flammable wastes making the disposal process even harder and riskier.

When hazardous wastes like pesticides, batteries containing lead, mercury, or zinc, cleaning solvents, radioactive materials, e-waste, and plastics mixed up with paper and other non-toxic scraps are burned they produce dioxins, furans, polychlorinated biphenyls, and other gases. These toxic gases have the potential of causing various diseases, including cancer.

Our carelessness with our waste and garbage also affects animals, and they suffer the effects of pollution caused by improperly disposed of wastes and rubbish.

Consuming Styrofoam and cigarette butts have been known to cause deaths in marine animals. Animals are also at risk of poisoning while consuming grasses near contaminated areas or landfills as the toxins seep into the soil.

There are different methods of solid waste management. The following are some of the recognized methods:

This is the most popular solid waste disposal method used today. Garbage is basically spread out in thin layers, compressed, and covered with soil or plastic foam. 

Modern landfills are designed in such a way that the bottom of the landfill is covered with an impervious liner, which is usually made of several layers of thick plastic and sand. This liner protects the groundwater from being contaminated because of leaching or percolation.

When the landfill is full, it is covered with layers of sand, clay, topsoil, and gravel to prevent seepage of water.

Advantage: If landfills are managed efficiently, it is an ensured sanitary waste disposal method.

Constraint: It requires a reasonably large area.

This method involves the burning of solid wastes at high temperatures until the wastes are turned into ashes. Incinerators are made in such a way that they do not give off extreme amounts of heat when burning solid wastes. 

Incinerators that recycle heat energy through furnaces and boilers are called waste-to-energy plants. These waste-to-energy systems are more expensive to set up and operate compared to plain incinerators because they require special equipment and controls, highly skilled technical personnel, and auxiliary fuel systems.

This method of solid waste management can be done by individuals, municipalities, and even institutions. The good thing about this method is the fact that it reduces the volume of waste up to 20 or 30% of the original volume.

Advantage: The volume of combustible waste is reduced considerably by burning waste. In the case of off-site pits, it is an appropriate method to minimize scavenging.

Constraint: It can cause smoke or fire hazard and also emits gaseous pollutants.

Recycling or recovery of resources is the process of taking useful but discarded items for the next use. Plastic bags, tins, glass, and containers are often recycled automatically since, in many situations, they are likely to be scarce commodities.

Traditionally, these items are processed and cleaned before they are recycled. The process aims at reducing energy loss, consumption of new material, and reduction of landfills. The most developed countries follow a strong tradition of recycling to lower volumes of waste.

Advantage: Recycling is environmentally friendly.

Constraint: It is expensive to set up, and in most emergencies, there is limited potential.

Due to a lack of adequate space for landfills, biodegradable yard waste is allowed to decompose in a medium designed for the purpose. Only biodegradable waste materials are used in composting. 

It is a biological process in which micro-organisms, specifically fungi, and bacteria, convert degradable organic waste into substances like hummus. This finished product, which looks like soil, is high in carbon and nitrogen. Good quality environmentally friendly manure is formed from the compost that is an excellent medium for growing plants and can be used for agricultural purposes.

Advantage: Composting is environmentally friendly as well as beneficial for crops.

Constraint: It requires intensive management and experienced personnel for large-scale operation.

This is a method of solid waste management whereby solid wastes are chemically decomposed by heat without the presence of oxygen. It usually occurs under pressure and at temperatures of up to 430 degrees Celsius. The solid wastes are changed into gasses, solid residue of carbon and ash, and small quantities of liquid.

Advantage: This will keep the environment clean and reduce health and settlement problems.

Constraint: The systems that destroy chlorinated organic molecules by heat may create incomplete combustion products, including dioxins and furans. These compounds are highly toxic in the parts per trillion range. The residue it generates may be hazardous wastes, requiring proper treatment, storage, and disposal.

Challenges of Solid Waste Management: - The second largest populated country in the world, India faces various hindrances to its development. Solid Waste Management is of critical concern and needs attention. Whereas many developed countries are searching for ready-made sustainable waste management solutions, India has created institutions to take on the big challenge of formal research on the topic.

The current waste management practice in India involves collecting waste from sources through a community collective bin system, after which it gets transported to a low-lying landfill system with intermediate processing of Municipal Solid Waste (MSW). The open dumping practice is leading to various problems like pollution and health hazards. Both surface and groundwater are affected by this; in fact, groundwater is in a critical state. Current procedures are not ideal, hence, the solid waste management crisis.

As pointed out, statistics show that in 2001 India generated 46 million tonnes of waste and by 2048 this number is predicted to reach an estimated 125 million tonnes, making India the largest waste contributor to the world.

According to Dr. Kumar, the major problems affecting solid waste management are unscientific treatment, improper collection of waste, and ethical problems. This in turn leads to hazards like environmental degradation, water pollution, soil pollution, and air pollution.

Explaining the options and challenges for India to battle its waste management crisis, Dr. Kumar talked about technologies pursued in developed countries such as bio-composting and incineration – converting waste to energy. Recycling should be followed with a parallel emphasis on source segregation and quality-cost ratio control. Finally, he also brought up optimum methane capturing as one of the possible solutions.

In concluding his presentation, Dr. Kumar shared several recommendations. In essence, the current philosophy calls for sustainable, cost-effective (and risk-based), as well as integrated approaches to better manage risks and recover resources from waste.

He later interacted with the audience and answered queries on the presentation. All in all, Dr. Kumar provided an adequate view of various aspects of the Indian economy and its difficulties in overcoming its present challenges. India has come a long way in marking itself in the field of scientific research. It has achieved a lot yet still has more to achieve in terms of finding solutions for both local as well as international problems.

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