Chapter 21: Waste Management — II: Safe Disposal of Waste
It is seven in the morning in a housing colony, and three bins stand together at the gate. One is marked ‘dry’, one ‘wet’, one ‘others’. A boy comes down with the night’s rubbish in a single bag — potato peels, a torn plastic packet, a broken bulb, wet tea leaves, a newspaper. He stops, because the bag will not go into any one of them. So he does something that takes ninety seconds and changes everything that happens next. The peels and tea leaves go into the wet bin, the packet and the newspaper into the dry bin, the broken bulb into the third. The peels will be turned into compost and returned to the colony’s garden. The newspaper and the packet will be sold on, shredded, remade. Only the bulb needs careful handling. Almost nothing from that bag will now travel to a landfill. Had he tipped the whole bag in as it was, the wet peels would have soaked the paper, the glass would have cut through the packet, and the entire mixture — worth something as five separate things — would have been worth nothing at all.
Diagram
Fig. 21.A1 Caption: Ninety seconds at the bin decides whether a day’s waste becomes compost, raw material or landfill. Brief: Illustration of a single household bag at the top splitting into three labelled bins — ‘dry’, ‘wet’, ‘others’ — with the contents named in the opener shown falling into the correct bin; arrows point downward from bag to bins and onward from each bin to its destination (compost heap, recycling, careful disposal); do not show any waste being burnt.
21.1 Methods Of Safe Disposal Of Waste
How Much Waste, And Why It Is Growing
According to the Ministry of Environment, Forest and Climate Change, solid waste generation in India is growing at the rate of 4% per year. On that rate it is estimated to rise to 165 million tonnes by 2030. The cause is not one thing but two working together — rapid economic growth, and changing consumption patterns.
Those two causes are worth separating. Growth means more households buying more goods; changed consumption means each good arrives wrapped, sealed and packed in material that is thrown away within minutes of purchase. A city can therefore see its waste rise faster than its population.
To face this, India needs long-term waste management strategies rather than daily clearing. With the Swachh Bharat Abhiyan, India aims for a cleaner and more sustainable future. The mission aims to identify, test, validate and deploy technologies that treat waste to generate electricity, recycle materials and extract resources of value.
The first step towards effective waste management is proper segregation of waste at source — that is, in the home or shop where the waste is made, not later at a dump. This is what enables recycling and resource recovery. Active community participation and Public-Private Partnerships promote responsible practices. Finally, government investment in infrastructure for waste treatment technologies, such as composting plants and energy-from-waste plants, is the need of the hour.
21.1.1 Segregation
Segregation of waste means dividing the waste into different categories like dry and wet, or biodegradable and non-biodegradable. It is done before the waste is disposed of, because once the categories are mixed they cannot be cleanly pulled apart again.
Dry waste consists of waste that does not decay and is non-biodegradable. It includes wood and related products like timber, sawdust, home and office furniture and household junk, along with aluminium foils, tetra packs, plastic products, broken crockery, steel utensils and glass.
Wet waste comprises waste that is organic in nature and is biodegradable, which means it can be decomposed or broken down by living organisms. It includes kitchen waste from homes and from eating establishments — vegetable and fruit peels, stale food, and rotten fruits and vegetables.
What Segregation Actually Achieves
Separating the two streams changes what happens to all the waste that follows. The gains the chapter records are these. (a) There is a reduction in the volume of waste that reaches landfills, because whatever can be composted or recycled never travels there. (b) Air and water pollution is considerably reduced, since less material is left to rot in the open or to be burnt. (c) It becomes easier to apply different processes of waste disposal such as composting, recycling and incineration, each of which needs a clean single stream to work on.
In fact, segregation of waste is the key to effective waste management. Every method described later in this chapter assumes that someone, somewhere, has already separated the material.
The Two Great Divisions
Waste can be segregated as biodegradable and non-biodegradable, meaning material that living organisms cannot break down. Biodegradable waste includes organic waste — kitchen waste, vegetables, fruits, flowers, leaves from the garden, and paper.
Non-biodegradable waste can be further segregated into three kinds, and the third and fourth of these need real care in handling. (a) Recyclable waste, which includes plastics, paper, glass and metal, and which can be treated and fed back into manufacturing. (b) Toxic waste, which includes old medicines, paints, chemicals, bulbs, spray cans, fertilizers and pesticide containers, batteries and shoe polish. (c) Soiled waste, which is hospital waste such as cloth soiled with blood and other body fluids.
Toxic and soiled waste must be disposed of with utmost care. They are the smallest part of the heap by volume and the most dangerous part of it by effect, which is exactly why they must not be allowed to travel with the rest.
Flowchart
Fig. 21.A2 Caption: Every piece of waste belongs on one of these branches, and each branch has a different safe route. Nodes: waste → biodegradable (kitchen waste, vegetables, fruits, flowers, garden leaves, paper) → composting or biogas; waste → non-biodegradable → recyclable waste (plastics, paper, glass, metal) → recycling; non-biodegradable → toxic waste (old medicines, paints, chemicals, bulbs, spray cans, fertilizer and pesticide containers, batteries, shoe polish) → disposal with utmost care; non-biodegradable → soiled waste (hospital cloth soiled with blood and other body fluids) → disposal with utmost care
The waste is segregated before it is disposed of. In colonies, various types of dustbins are used to segregate glass, metals, paper and cloth, and each type is then handled separately — by reusing it, recycling it, or disposing of it in any other accepted waste disposal method.
The many categories a modern system separates are shown in Fig. 21.2, where each stream carries its own symbol so that a worker can identify it without reading a label.
Diagram
Fig. 21.2 Caption: The streams a waste system keeps apart, each with its own symbol. Brief: Reproduce the chapter’s icon chart of waste types — general, organic, hazardous, e-waste, medical, construction, food service, green, paper, secure shredding, cardboard, recyclables, plastics, glass, batteries, metals, oil, chemicals, light bulbs and textiles — each icon with its label beneath it, arranged in a grid.
Where The Work Falls
It should be the duty of each household to segregate domestic waste into different dustbins, biodegradable and non-biodegradable, and then to convert the biodegradable ones into other useful products like compost or biogas. Urban residential colonies should undertake collective efforts for the safe disposal of domestic waste, as well as of the sweepings from gardens and public parks. Those sweepings can be converted into compost and used for the maintenance of the same gardens and parks, so the material never leaves the colony at all.
Sorting out the reusable material from heaps of waste may often involve much manual labour. In a country like India, poor rag pickers make a living by sorting out reusable and recyclable items from discarded solids. In doing so they remove much of the waste from the garbage dumps, and pieces of metal, glass, rubber and plastics are taken out to be recycled into finished products.
21.1.2 Dumping
Dumping means placing waste on land. Two very different practices go by that name, and the difference between them is the difference between a hazard and a managed site.
Open Dumping
In open dumping, waste materials are dumped in open low lands far away from the city. This method is not environment friendly. However, it is the cheapest method and does not need much planning, which is why it survives.
The open pits spoil the sight of the area and become a breeding ground for mosquitoes, flies and insects, which are the carriers of harmful diseases. They give out foul odour. The burning of waste material in the open dumps pollutes the air.
Another danger of open dumping is what rain does to it. Rainwater could carry the harmful substances to the nearby streams, ponds or lakes, and if the water seeps down it could pollute the groundwater — the water stored in the rock and soil below, which is what wells and tube wells draw on.
Sanitary Landfill
In a sanitary landfill, the waste is packed and dumped daily at the site and is covered with earth, to prevent insects or rodents from entering into the landfill. The waste is then subjected to bacterial decomposition. Physical, chemical and biological reactions take place, generating different gases like carbon dioxide, methane, ammonia and hydrogen sulphide. These gases can be recovered and used to generate power, so the site produces energy while it settles.
Sanitary landfill is a way of disposing refuse on land without creating nuisances or hazards to public health or safety. The waste disposal is carried out with minimal environmental damage, and in areas already spoiled or in need of restoration — land that has already been damaged, rather than land still in good condition.
Diagram
Fig. 21.1 Caption: At a sanitary landfill the day’s waste is tipped, spread and then covered with earth. Brief: Photograph of a working sanitary landfill showing tipper trucks at the face, spread waste and an earth-moving machine placing cover material; label the covered earth layer.
The Five Phases Inside A Landfill
In a sanitary landfill a biological method of disposing of waste is used, and the buried waste passes through five phases in order. (a) In the first phase of operation, aerobic bacteria — bacteria that work in the presence of oxygen — deplete the available oxygen and cause the temperature to increase. (b) In the second phase, anaerobic conditions get established, meaning the oxygen is now gone, and this leads to the evolution of hydrogen and carbon dioxide. (c) Phase three establishes a population of bacteria and the beginning of methanogenic activity, which is the production of methane from the decomposition of organic matter. (d) In the fourth phase the methanogenic activity becomes stabilised, and the gas comes off at a steadier rate. (e) The fifth phase depletes the organic matter, and the system returns to an aerobic state.
Flowchart
Fig. 21.A3 Caption: The buried waste changes chemically for years after the last truck has left the site. Nodes: waste packed and covered with earth → phase 1: aerobic bacteria use up the oxygen, temperature rises → phase 2: anaerobic conditions establish, hydrogen and carbon dioxide evolve → phase 3: bacteria population builds, methanogenic activity begins, methane produced → phase 4: methanogenic activity stabilises → phase 5: organic matter depleted, back to an aerobic state
The advantages of sanitary landfill as opposed to open dumping follow directly from that cover of earth. (a) It is free from air pollution from burning, because nothing at the site is set alight. (b) The health problems are minimised, since flies, rats and other pests cannot breed in the landfill because of the covered wastes. (c) It is mostly free from fire hazards.
21.1.3 Plantation At Landfill Site
A landfill does not stop being a landfill when it is full, and the surface has to be held together. A vegetative cover should therefore be provided over the landfill site, in accordance with the following specifications. (a) Locally adapted non-edible perennial plants that are resistant to drought and extreme temperatures should be planted, so that nothing grown there enters the food chain. (b) The plants grown should be such that their roots do not penetrate more than 30 cm, which is about the length of a school ruler, and this condition should apply till the landfill is stabilised. (c) Selected plants should have the ability to thrive on low-nutrient soil with minimum nutrient addition. (d) Plantation should be made in sufficient density to minimise soil erosion.
Read those four together and the logic appears. Shallow roots keep the cover sealed, hardy plants survive without watering or feeding, and dense planting stops the covering soil from washing off the mound in the first heavy rain.
21.1.4 Municipal Waste Management
Household segregation is only useful if the city then keeps the streams apart. That work belongs to the municipal authorities, and it runs in four stages — collection, storage, transportation and community participation.
21.1.4.1 Collection Of Municipal Solid Wastes
To prohibit littering, the following steps should be taken by the municipal authorities. (a) Organising house-to-house collection of municipal solid wastes. (b) Devising collection of waste from slums and squatter areas, or from localities including hotels, restaurants, office complexes and commercial areas. (c) Bio-medical wastes and industrial wastes should not be mixed with municipal solid wastes. (d) Horticultural and construction wastes — the waste from gardens and nurseries, and the rubble from building work — should be separately collected and disposed of. (e) The waste should be segregated into biodegradable and non-biodegradable. (f) Waste, whether garbage or dry leaves, should not be burnt. (g) Stray animals should not be allowed to move around waste storage facilities.
21.1.4.2 Storage Of Municipal Solid Wastes
The following criteria should be taken into account while establishing and maintaining storage facilities. (a) Storage facilities should be set up by taking into account the quantities of waste generation in an area and its population density, and the facility is to be so placed that it is accessible to users. (b) These facilities are to be so designed that the wastes stored are not exposed to the open atmosphere, and are aesthetically acceptable and user-friendly. (c) Storage facilities or ‘bins’ should have an ‘easy to operate’ design for handling, transfer and transportation of waste. (d) Manual handling of waste should be avoided.
Two of these carry more weight than they seem to. A bin placed where people do not pass will not be used, however well designed; and a bin that cannot be emptied by machine forces someone to touch the waste by hand.
21.1.4.3 Transportation Of Municipal Solid Wastes
Vehicles used for transportation of wastes should be covered. This prevents the wastes from being scattered along the road. Waste should not be visible to the public, nor exposed to the open environment.
Diagram
Fig. 21.4 Caption: Colour-coded bins keep the dry, the wet and the rest apart from the moment of throwing. Brief: Photograph of a public three-bin unit, green, yellow and red, labelled ‘dry’, ‘wet’ and ‘others’; keep all three labels legible.
21.1.4.4 Community Participation In Segregation Of Municipal Solid Wastes
The municipal authorities should undertake a phased programme to ensure community participation in waste segregation. The word phased matters: a city cannot switch a whole population to three bins in one week, and a scheme that arrives faster than people can learn it ends with the streams mixed again in the vehicle.
21.1.5 Composting
Composting of waste is an aerobic method of decomposing solid wastes, that is, a method carried out in the presence of air. The organic wastes from households are made to undergo decomposition in such a way that bacteria and other micro-organisms break them down and produce a safe, clean and soil-like material called compost.
In India, both the manual as well as mechanical methods of composting are used, and the chapter names one of each.
Two Indian Methods
In the manual method used in rural areas, layers of vegetable waste and night soils — human waste collected from dry latrines — are alternated in a shallow hole dug in the ground. The mixture is turned regularly for about three months, which is what provides air to the mixture. The compost is then left for another month without turning, for the process to take effect. This method of composting is known as the Indore Method.
In the mechanical process, used in Bengaluru and adopted by other cities in the country, the waste material is placed in layers about one metre deep. The material is not turned at all, but it decomposes completely in about five months. This method of composting is known as the Bengaluru Method.
The contrast between them is a trade of labour against time. The Indore Method demands regular turning by hand and finishes in about four months in all, while the Bengaluru Method demands almost no handling and takes about five months. Both are aerobic, and in the Bengaluru Method the shallow one-metre layers are what let air reach the material without turning.
The Cradle To Cradle Idea
Composting returns material to the soil rather than to a hole in the ground, and there is a whole design philosophy built on that move. The Cradle to Cradle, or C2C, concept is a sustainable design philosophy that drives product development by modelling human industry on nature’s processes. It follows a biomimetic approach, meaning it imitates nature, and it views materials as nutrients circulating in cycles like natural ecosystems.
In this approach there are two types of nutrients. Technical nutrients are non-toxic, non-harmful synthetic materials that can be reused indefinitely without losing quality. Biological nutrients are organic materials that can safely return to the environment and decompose naturally.
Just like the nutrient cycles in nature, these nutrients would have a closed loop lifecycle. This ensures that all materials can be reused or safely returned to the environment. Beyond industrial design, C2C can be applied to urban environments, buildings and social systems, and the concept is gaining traction in India as the country seeks sustainable solutions to its environmental challenges.
Diagram
Fig. 21.5 Caption: In the cradle to cradle idea, nothing leaves the system — one loop returns to the soil and the other returns to the factory. Brief: Reproduce the chapter’s twin-loop figure — a green biological cycle running manufacturing → product → usage → abrasion and wear debris → compost → biological nutrient → organic agriculture or forestry → back to manufacturing, and a blue technical cycle running manufacturing → product → usage → collection → disassembly and separation → technical nutrient → back to manufacturing, with a dotted ‘direct reuse’ short-cut; arrows run clockwise in each loop and both loops meet at manufacturing.
Diagram
Fig. 21.3 Caption: Kitchen and garden waste being worked into compost. Brief: Photograph of workers turning a heap of vegetable and food waste with rakes at a composting site; show the layered heap and the turning tools.
21.1.5.1 Advantages Of Composting
The major benefits of composting are these. (a) It enhances soil nutrients and the water retention capacity of soils, so the ground holds more of the rain that falls on it. (b) It suppresses plant diseases. (c) It rejuvenates poor soils by adding humus, the dark decayed organic matter that gives a soil its fertility and its crumb. (d) It absorbs odours and degrades volatile organic compounds. (e) It prevents pollution, by preventing pollutants in storm water run-off from draining into water resources. (f) It checks soil erosion and silting on embankments. (g) It reduces cost, as there is no need for excess water, fertilizers and pesticides.
Notice how far that list travels from the dustbin. A method for handling kitchen waste ends up protecting a river from run-off and a field from erosion, because the compost holds both water and soil in place.
21.1.6 Incineration
In cities, vacant areas for disposal sites are not very many, so the incineration process is used for waste disposal by industries and municipalities. Where land is the scarce thing, a method that needs little of it becomes attractive.
Incineration is the process of controlled high temperature oxidation of primarily organic compounds that release thermal energy and produce carbon dioxide and water. In short, incineration involves burning of wastes at a very high temperature. The waste to be burnt is fed into an incineration chamber, or kiln, and combustion consumes and destroys the organic component.
Incineration is a useful technology to deal with large quantities of organic hazardous wastes that have high calorific value — that is, wastes that give out a great deal of heat when burnt — and that cannot be dealt with by other methods. By this method pathogenic organisms, the ones that cause disease, are killed, and the volume of the waste is reduced up to 50 per cent.
However, the incineration process has its limitations. (a) It is quite expensive. (b) It generates ash and combustion gases which have an adverse impact on human health and environment. (c) It consumes a significant amount of energy to achieve the high temperature it needs.
That last limitation is worth holding on to. A method that destroys waste by burning must itself be fed with energy, so the saving in land is paid for in fuel.
21.1.7 Waste To Energy (WtE)
Waste to Energy, written WtE, refers to the process of converting waste materials into usable energy, which could be electric power, heat or fuel. It uses industrial processes such as incineration, and biological processes such as fermentation and anaerobic digestion — breakdown by micro-organisms in the absence of air.
Different components of the waste contribute to energy production in different ways, and each is broken down by the route that suits its chemistry. (a) Hydrocarbons, found in organic materials like food waste, plastics and petroleum products, release energy when they are burned. Burning plastic waste, for example, generates heat, which can be converted into steam to drive turbines for electricity generation. (b) Carbohydrates, fats and oils, present in food waste and plant materials, are broken down into simpler compounds, producing biogas as a result of anaerobic digestion by microorganisms. (c) Cellulose, found in paper, cardboard and plant materials, is broken down into simpler sugars through microbial action or chemical processes. These sugars can then be fermented into ethanol or combusted to release energy. (d) Lignin, a component of wood, can be burned directly in incineration. (e) Nitrogen and sulphur compounds, present in proteins and other nitrogenous waste, can be transformed into energy during anaerobic digestion.
Flowchart
Fig. 21.A4 Caption: What a waste-to-energy plant does depends entirely on what the waste is made of. Nodes: sorted waste → hydrocarbons in food waste, plastics and petroleum products → burned → heat → steam → turbine → electricity; sorted waste → carbohydrates, fats and oils in food waste and plant materials → anaerobic digestion → biogas; sorted waste → cellulose in paper, cardboard and plant materials → microbial action or chemical process → simpler sugars → fermented to ethanol, or combusted → energy; sorted waste → lignin in wood → burned directly in incineration → heat; sorted waste → nitrogen and sulphur compounds in proteins and nitrogenous waste → anaerobic digestion → energy
Every one of those five routes begins with a sorted material. A plant cannot ferment a bag that also contains glass, and it cannot digest a heap that also contains batteries. This is why the chapter began with segregation and not with the machinery: the technology at the end of the line is only as good as the sorting at the start of it.
21.2 Reduce-Reuse-Recycle Waste
Safe disposal deals with waste that already exists. The three R’s ask a different question: how much of it needed to exist at all. Waste can be effectively managed by using the following three R’s of waste management. (a) Reducing the waste, so that less of it is made in the first place. (b) Reusing the waste, so that an article is used again as it is. (c) Recycling the waste, so that the material is treated and sent back into manufacturing.
The order is not accidental. Each R catches what the one before it could not, and only what escapes all three has to be dumped, burnt or buried.
Diagram
Fig. 21.6 Caption: The three R’s of waste management, drawn as a loop because each one feeds the next. Brief: Reproduce the chapter’s triangular figure with ‘reduce’, ‘reuse’ and ‘recycle’ set along the three sides, joined by broad arrows running continuously around the triangle in one direction.
21.2.1 Reducing The Waste
The waste can be reduced by making use of the following methods, and all three of them act inside the factory rather than at the bin. (a) Change of process: in industries, changes can be made in the production process to reduce waste generation. This reduction can be achieved either by changing the material used to finish the product, or by using the input materials more efficiently in the production process, or both. (b) Waste concentration: by using scientific techniques such as precipitation and evaporation, the amount of liquid waste can be reduced. Incineration can be used to get rid of inflammable wastes. (c) Segregation of waste: first of all, non-hazardous waste is separated from hazardous waste rather than dumping them together. Then the small amount of hazardous waste can be treated, and we can dispose of the large amount of non-hazardous waste in the traditional ways.
The third method repeats a lesson from earlier in this chapter at a different scale. Mixing a little hazardous waste into a great deal of harmless waste does not dilute the danger — it multiplies the quantity that now has to be treated as dangerous.
21.2.2 Reusing The Waste
In our houses and in industries, many materials are discarded as wastes. These materials have some value, for instance glass, metal pieces, rubber, wood fibre and paper products.
In developing countries like India, some of the waste materials such as old glass bottles, steel tyres and tin cans are reused. Shoes or chappals are made from old tyres, water bags are made from leather, and lamps are made from tin cans.
Many waste collectors roam about in residential areas and industrial units to collect solid wastes. They segregate them and supply them to specialised artisans, who make utility articles from such material and make a living from their skill. In this way, waste collectors help in making new production processes, and they reduce the burden of waste disposal.
The clearest example of the idea is a place people travel to see. A beautiful garden, the Rock Garden, has been created by Nek Chand in Chandigarh using waste products like tin cans, bottles and broken pieces of crockery.
Industrial Reuse
Some solid wastes from the industry can be utilised directly, with no treatment at all. Fly ash, the fine ash carried up with the flue gases when coal is burnt in power plants, is used to manufacture cement. Bricks are made from fly ash. Fly ash is also used in making roads and in filling up low-lying areas.
21.2.3 Recycling Of Waste
Besides reusing the materials by using physical processes, we also use the recycling process, in which the waste is treated before it is used in a manufacturing process. Reuse keeps the article; recycling keeps only the material and destroys the article.
In India, we have tonnes of bagasse from sugarcane during a particular season. Bagasse is the dry fibrous matter left after the cane has been crushed for its juice, and it is used in the manufacture of paper pulp. This helps to save trees which are normally used for making paper pulp. Bagasse is also used for making packaging material for dairy products. The paper industry also recycles pieces of wood from the furniture industry, used and discarded cloth, and used paper.
The Plastic Problem
Plastics are recycled by plastic manufacturers. About 80 per cent of the plastic waste is recycled in India, which is about 0.75 million tonnes a year.
Plastic is non-biodegradable, and the reason lies in its chemistry. The bonds of carbon in plastic are impossible to break down through a physical or chemical process, so plastic has to be incinerated, recycled or buried in landfills. There is no fourth route, and no natural one.
The plastic bags which are extensively used in India are made from recycled plastic. These recycled plastic bags are harmful, because the melting of plastic and plastic products breaks some polymer chains — the long chains of repeating units that plastic is built from — into smaller units which are harmful.
21.2.4 The Indore Model Of Waste Treatment
By adopting a comprehensive, integrated approach to waste management, Indore, the cleanest city of India for seven consecutive years, has set a benchmark for sustainable urban living. It has done so by five measures working together. (a) Segregation at the source, by a mandatory waste segregation policy requiring households to separate waste into wet, meaning biodegradable, and dry, meaning recyclable, categories. (b) Door-to-door waste collection, which ensured timely and efficient collection and prevented littering and illegal dumping. (c) Waste processing and disposal, with a state-of-the-art waste processing facility capable of handling 1,000 metric tons of waste daily, including a 15 MW waste-to-energy plant and a 200 TPD, or tons per day, composting plant. These facilities enabled the city to process and dispose of waste more effectively, leading to a substantial reduction in landfill usage and minimising the environmental impact of waste disposal. (d) Public awareness and participation, which resulted in increased community involvement and support for the waste management programme. (e) Strict monitoring and enforcement to ensure compliance with waste management rules, which, combined with regular inspections and penalties, proved to be effective in maintaining the city’s cleanliness.
A megawatt, written MW, is a measure of the rate at which electricity is generated, and 15 MW is a modest but real supply for a city — produced here from material that would otherwise have been buried.
That one-fifth is not a figure the plant can reach on its own. A composting plant can only take wet biodegradable waste, so the 200 tons a day exist because households were required to separate wet from dry before collection. The mandatory segregation policy and the composting capacity are therefore the same measure seen at two ends of the line — remove the first and the second stands idle.
21.2.5 Case Study: Roads From Plastic Waste
A Government of India Order in November 2015 made it mandatory for all road developers in the country to use waste plastic, along with bituminous mixes, for constructing roads. Bitumen is the black, sticky binder that holds the stone of a road surface together. The order was made to overcome the growing problem of plastic waste disposal in the country.
The technology for this was developed by the ‘Plastic Man’ of India, Prof. Rajagopalan Vasudevan, Professor of Chemistry at Thiagarajar College of Engineering, Madurai. The plastic waste items that can be used for road construction include plastic carry bags, plastic cups, and plastic packaging for potato chips, biscuits and chocolates — that is, exactly the thin, light plastic that is hardest to collect and least worth recycling.
How The Mix Is Made
The plastic waste material is first shredded to a particular size using a shredding machine. The aggregate mix is heated at 165 °C and transferred to the mixing chamber, and the bitumen is heated to 160 °C to result in good binding. The resulting mix is then used for road construction.
Flowchart
Fig. 21.A5 Caption: Waste plastic becomes part of a road surface without any new machinery being needed. Nodes: collected plastic carry bags, cups and packaging → shredding machine → shredded plastic of a set size → aggregate heated to 165 °C → mixing chamber → bitumen heated to 160 °C → good binding → mix laid as road surface
The advantages accrued from this method are these. (a) The process is easy and does not need any new machinery, so existing road plants can use it. (b) For every kilo of construction material, 50 g of bitumen is used and 1/10th of this is plastic waste, which reduces the amount of bitumen being used. (c) The road construction process is eco-friendly, with no toxic gases being released. (d) Plastic waste helps increase the strength of the road, reducing road fatigue. (e) These roads have better resistance to rain water and cold weather. (f) Since a large amount of plastic waste is required for a small stretch of road, the amount of waste plastic strewn around gets tremendously reduced.
Five grams sounds like nothing, and that is the point of doing the arithmetic. A road is built in tonnes, not in kilos, so every tonne of mix takes 5 kg of shredded carry bags off the ground and saves 5 kg of bitumen, which is itself a petroleum product. The chapter’s own claim — that a small stretch of road swallows a large amount of plastic — is what these two numbers look like when they are scaled up.
Diagram
Fig. 21.7 Caption: A stretch of road built with waste plastic in the bituminous mix. Brief: Photograph of a surfaced road with a roadside board stating that the road is made from waste plastic; keep the board legible and show the road surface in the foreground.
What Doing This Properly Adds Up To
If done in the proper manner, waste management not only eliminates the surrounding wastes but also reduces the intensity of the greenhouse gases like methane and carbon monoxide which are emitted from accumulated wastes. Greenhouse gases are the gases that trap heat in the atmosphere, and a heap of rotting waste is a steady source of them.
The depth of the existing landfills will also be curbed, thereby cutting down whatever is toxic to the environment. The number of fossil fuels will also get reduced in this manner, leading to a cleaner and a greener environment.
That last point closes the loop this chapter has been drawing. Waste that becomes compost replaces fertiliser, waste that becomes energy replaces fuel, and waste that becomes road material replaces bitumen — so material treated as worthless at the bin turns out to be standing in for something the country would otherwise have had to dig up.
21.3 Summary
- Solid waste generation in India is growing at the rate of 4% per year and is estimated to rise to 165 million tonnes by 2030, because of rapid economic growth and changing consumption patterns.
- With the Swachh Bharat Abhiyan, India aims for a cleaner and more sustainable future, and the mission works to identify, test, validate and deploy technologies that treat waste to generate electricity, recycle materials and extract resources of value.
- Effective waste management begins with segregation at source, supported by community participation, Public-Private Partnerships and government investment in composting plants and energy-from-waste plants.
- Segregation of waste means dividing waste into categories such as dry and wet, or biodegradable and non-biodegradable.
- Dry waste does not decay and is non-biodegradable, and includes timber, sawdust, furniture, household junk, aluminium foils, tetra packs, plastic products, broken crockery, steel utensils and glass.
- Wet waste is organic and biodegradable, and includes kitchen waste such as vegetable and fruit peels, stale food and rotten fruits and vegetables.
- Segregation reduces the volume of waste reaching landfills, considerably reduces air and water pollution, and makes composting, recycling and incineration possible, which is why it is the key to effective waste management.
- Non-biodegradable waste is further divided into three kinds.
- Recyclable waste — plastics, paper, glass and metal.
- Toxic waste — old medicines, paints, chemicals, bulbs, spray cans, fertilizer and pesticide containers, batteries and shoe polish.
- Soiled waste — hospital waste such as cloth soiled with blood and other body fluids, and toxic and soiled waste must both be disposed of with utmost care.
- Households should segregate domestic waste and convert the biodegradable part into compost or biogas, and colonies should compost their garden and park sweepings for use in the same gardens.
- Waste collectors and rag pickers remove much reusable and recyclable material from garbage dumps by hand, and so reduce the burden of waste disposal.
- Two very different practices are called dumping.
- Open dumping places waste in open low lands away from the city; it is cheapest and needs little planning, but it spoils the landscape, breeds disease-carrying insects, gives foul odour, pollutes air when burnt, and lets rainwater carry harmful substances into streams, ponds, lakes and groundwater.
- In a sanitary landfill the waste is packed, dumped daily and covered with earth, then decomposed by bacteria, generating carbon dioxide, methane, ammonia and hydrogen sulphide, which can be recovered to generate power.
- A sanitary landfill disposes of refuse on land without creating nuisances or hazards to public health or safety, with minimal environmental damage, and in areas already spoiled or in need of restoration.
- Waste in a sanitary landfill passes through five phases: aerobic bacteria use up the oxygen and raise the temperature; anaerobic conditions evolve hydrogen and carbon dioxide; methanogenic activity begins and methane is produced; that activity stabilises; and finally the organic matter is depleted and the system returns to an aerobic state.
- Compared with open dumping, a sanitary landfill is free from air pollution from burning, minimises health problems because pests cannot breed in the covered waste, and is mostly free from fire hazards.
- A landfill site is given a vegetative cover of locally adapted, non-edible, drought-resistant perennial plants whose roots do not penetrate more than 30 cm, which thrive on low-nutrient soil and are planted densely enough to minimise soil erosion.
- Municipal waste management runs in four stages.
- Collection — house-to-house collection, collection from slums, squatter areas and commercial establishments, keeping bio-medical, industrial, horticultural and construction wastes separate, segregating waste, not burning it, and keeping stray animals away from storage facilities.
- Storage — facilities sized to the waste generated and the population density, accessible, enclosed, user-friendly, easy to operate, and designed so that manual handling is avoided.
- Transportation — vehicles must be covered so that waste is not scattered, visible to the public or exposed to the open environment.
- Community participation — a phased programme by the municipal authorities to involve people in segregation.
- Composting is an aerobic method of decomposing solid waste, in which bacteria and micro-organisms break down household organic waste into a safe, clean, soil-like material called compost.
- In the Indore Method, layers of vegetable waste and night soil are alternated in a shallow hole, turned regularly for about three months, then left for another month without turning.
- In the Bengaluru Method, a mechanical process, waste is placed in layers about one metre deep and decomposes completely in about five months without being turned at all.
- Composting enhances soil nutrients and water retention, suppresses plant diseases, rejuvenates poor soils with humus, absorbs odours, degrades volatile organic compounds, keeps pollutants in storm water run-off out of water resources, checks soil erosion and silting on embankments, and reduces cost by removing the need for excess water, fertilizers and pesticides.
- The Cradle to Cradle concept models industry on nature by treating materials as nutrients in a closed loop, dividing them into technical nutrients that can be reused indefinitely and biological nutrients that return safely to the environment.
- Incineration is the controlled high temperature oxidation of primarily organic compounds, releasing thermal energy and producing carbon dioxide and water; it kills pathogenic organisms and reduces waste volume up to 50 per cent, but is expensive, generates harmful ash and gases, and consumes significant energy.
- Waste to Energy converts waste into electric power, heat or fuel, using incineration and biological processes such as fermentation and anaerobic digestion, with hydrocarbons, carbohydrates, fats and oils, cellulose, lignin, and nitrogen and sulphur compounds each yielding energy by a different route.
- The three R’s of waste management are reducing, reusing and recycling the waste.
- Waste is reduced by change of process in industry, by waste concentration using precipitation and evaporation, and by separating non-hazardous from hazardous waste.
- Waste is reused directly, as old tyres, leather, tin cans and glass bottles are, as in the Rock Garden created by Nek Chand in Chandigarh, and as fly ash is in cement, bricks, roads and land filling.
- Waste is recycled after treatment, as bagasse is into paper pulp and dairy packaging, and as plastic is by manufacturers.
- About 80 per cent of India’s plastic waste is recycled, about 0.75 million tonnes a year; plastic is non-biodegradable and its carbon bonds cannot be broken physically or chemically, so it must be incinerated, recycled or landfilled, and recycled bags are harmful because melting breaks polymer chains into smaller harmful units.
- Indore, the cleanest city of India for seven consecutive years, combines mandatory segregation at source, door-to-door collection, a facility handling 1,000 metric tons daily with a 15 MW waste-to-energy plant and a 200 TPD composting plant, public participation, and strict monitoring and enforcement.
- A Government of India Order of November 2015 made the use of waste plastic with bituminous mixes mandatory for road developers, using technology developed by Prof. Rajagopalan Vasudevan at Thiagarajar College of Engineering, Madurai; shredded plastic is mixed with aggregate at 165 °C and bitumen at 160 °C, and for every kilo of construction material 50 g of bitumen is used, of which one-tenth is plastic waste.
- Waste management done properly reduces greenhouse gases such as methane and carbon monoxide from accumulated waste, curbs the depth of existing landfills, and reduces the use of fossil fuels.
Flowchart
Fig. 21.A6 Caption: Everything in this chapter is one decision made early — whether the waste is separated before it leaves the house. Nodes: waste generated → reduce at source (change of process, waste concentration, separating hazardous from non-hazardous) → what remains → segregated? no → open dumping (landscape spoiled, disease carriers, foul odour, polluted air and groundwater); segregated? yes → biodegradable → composting (Indore Method or Bengaluru Method) → compost → back to soil; segregated? yes → non-biodegradable → recyclable → reuse or recycling → back to manufacturing; segregated? yes → non-biodegradable → combustible or high calorific value → incineration and waste to energy → electric power, heat or fuel; residue after all routes → sanitary landfill → covered daily, five phases of decomposition → gases recovered → power
What This Chapter Cannot Tell You
The 4% growth rate and the 165 million tonne figure for 2030 are national numbers, and a national number hides everything inside it. A metropolitan city, a district town and a village generate different quantities of different kinds of waste, and none of them will be growing at exactly the country’s average rate.
The chapter names the methods of disposal but gives no measure of how much of India’s waste actually reaches each of them. We are told what a sanitary landfill, a composting plant and an incinerator do, not what share of the day’s rubbish arrives at one.
The Indore figures describe the capacity of one city’s facility on one date. They tell us what is possible where segregation is enforced; they cannot tell us how many other cities have reached it, or what happens to the waste in those that have not. ## 21.4 Check Your Concepts
- Look carefully at Fig. 21.2.
- Why are medical waste, chemicals and batteries shown as streams separate from general waste?
- What does this figure not tell you about the waste a town produces?
- The chapter states that about 80 per cent of India’s plastic waste is recycled, and that this recycled quantity is about 0.75 million tonnes a year. Using only these two figures, work out roughly how much plastic waste India generates in a year, showing each step of your working.
- The Indore Method and the Bengaluru Method are both aerobic, but only one of them involves turning the material. Explain how air still reaches the waste in the Bengaluru Method, and say what each method is trading away in return for the other’s advantage.
- Incineration reduces the volume of waste up to 50 per cent and needs very little land, which is why cities use it, yet it consumes a significant amount of energy to reach its high temperature. Explain the trade-off a city makes when it chooses incineration instead of a sanitary landfill.
- What do you mean by segregation of waste? How does it ensure safe waste disposal?
- What is meant by open dumping of waste? Why is open dumping not considered an environment friendly method?
- How is waste disposed of in a sanitary landfill?
- What service is indirectly done by the rag-pickers for the disposal of waste?
- State three steps that should be taken by the municipal authorities for the safe disposal of solid waste.
- Give a reason for each of the following:
- Recycling of waste to produce paper can reduce deforestation.
- Sugarcane waste can be recycled into useful products.
- We should avoid using polythene carry bags.