Waste Management : Basics
Solid Waste : Basics
Waste is defined in various ways; some says
Waste means any unusable material which is generated due to anthropogenic activities and basically intended to be discarded; Any material that is not useful and not represent any economic value to its owner;
Some technical and Environmental people like us belief that waste is a valuable raw material located at a wrong place;
Waste is a resource – Example
The food wasted by us becomes a resource for our animals, cloths not of use for us become a resource to poor people, the excreta/faeces wasted from our body becomes resource for micro-organisms etc
Thus the eventual statement is NOTHING IS WASTE.
Types of Waste
Waste, though I don’t like using this word but need to use the terminology to explain the real meaning and importance of waste.
Waste can be broadly categorized into 3 main categories; Solid, Liquid and Gaseous waste.
As you can see in the diagram; liquid waste basically consists of effluent discharged from industries and sewage discharged from domestic and commercial sectors. The waste consist of 80% liquid i.e. water and is treated in ETP (Effluent treatment Plant) and STP (Sewage treatment plants). ETP and STP will be discussed in water pollution section of the tutorial.
Gaseous waste consists of the emission from stacks (chimney) of industries, household and commercial areas (generator). It is also contributed by fugitive emissions; emissions of gases or vapors from pressurized equipment due to leaks and other unintended releases of gases, mostly from industrial activities.
The gaseous waste mainly because by fuel combustion thus consists primarily; carbon dioxide, carbon monoxide, oxides of sulphur and nitrogen, smoke, heat etc.
Solid waste is further categorized into 5 classes because of its characteristics and Government Rules for their disposal in India;
- Municipal Solid Waste - from household and commercial establishment
- Plastic Waste - from household and commercial establishment
- Biomedical Waste – from hospitals, clinics and dispensaries etc
- Hazardous Waste – from industries
- e-waste – electronic waste from any sector
As per the Indian Government Rules, the above mentioned wastes were earlier managed and treated under Rules given in blue box:
But now, MoEFCC has introduced new rules which has superseded all these rules in Year 2016 (March-April).
The rules are now called:
- Solid Waste Management Rules, 2016
- Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016
- Bio-Medical Waste Management Rules, 2016
- E-Waste (Management) Rules, 2016
- Plastic Waste Management Rules, 2016
Point to remember:-
- Biomedical waste becomes a part of Municipal solid waste after proper sterilization of waste. Example cotton, pads, cloths etc after sterilization (autoclaving) can be dumped as municipal solid waste. However; most of the bio-medical waste is incinerated to avoid any contamination.
- Paper, packing materials, cloths, food waste (non-contaminated) waste from industries also comes under municipal solid waste.
- You all must take care when you write the name of these rules, no alteration in placement of brackets and year.
- And also all these Rules comes under Environment (Protection) Act, 1986.
Municipal Solid Waste (MSW)
Municipal Solid Waste (MSW)
Have you ever wondered, why is the solid waste called Municipal Solid Waste?
The solid waste is managed by Municipalities thus the word Municipal is added to the solid waste and also it only accounts for urban waste; waste coming from rural areas is not accounted in this waste.
“Municipal solid waste" includes commercial and residential wastes generated in municipal or notified areas in either solid or semi-solid form excluding industrial hazardous wastes but including treated bio-medical wastes (more detailed definition in Rules)
MSW is released by many sources, as far as management is concern the major source of MSW are:
- Household – the waste generated from residential areas which consist of food waste, paper, plastics, glass, metals, cloths etc
- Commercial – the commercial solid waste basically consist of cartons, packing material, thermocol, plastics etc
- Institutional – institutes also generate majority of dry waste paper, plastic etc
- Agricultural – it consist of crop processing and packaging waste
- Animal waste - fish market, slaughter house waste, poultry and farm waste etc
- Construction & Demolition Waste (C&D) – cement, iron, sand etc
MSW – per capita generation in India
MSW – per capita generation
Per capita waste generation gives you the kilogram of waste generated by individual in a day. Though the values are average but it gives fair idea about the waste generation and its relation to urbanization and cost of living.
The figures given in table categorize the waste generation among low, high and middle income countries. The waste generation rates were highest for high income countries and are predicted to be high; due to power to purchase, higher packaging products and higher standard of living.
The urbanization is directly been linked to solid waste production. India’s per capita waste generation ranges between 200 – 870 grams/day and never exceeds 1 kg even for the metro cities. The per capita figures for four metro cities are given in table below:
As per recent report published by CPCB, India generates approximately 1,43,449 TPD (tons per day) of solid waste from 31 States. Out of this 1,17,644 TPD is collected by the urban local bodies and only 32,871 TPD of waste goes for treatment. Maximum waste generation is been recorded for Maharashtra followed by West Bengal and Uttar Pradesh. There is an annual increase of 1.3% in waste generation.
As per Central Public Health and Environmental Engineering Organisation; Solid waste in India largely consist of organic fraction in a range of 40% - 60%. As per study done by Sharholy et al., 2008; The composition of municipal solid waste at generation sources and collection points was determined on a wet weight basis and it consists mainly of a large organic fraction (40%–60%), ash and fine earth (30%–40%), paper (3%–6%) and plastic, and glass and metals (each less than 1%). The C/N ratio ranges between 800 and 1000 kcal/kg.
Urbanization & Waste generation
Urbanization & waste generation
As discussed previously, we will again see some points which prove that urbanization and waste generation are directly related. Many studies done by sociologists, environmentalist and economist have found a direct relation of urbanization with waste generation. Urbanization can be simply understood as economic growth, economic independence to spend and higher standard of living.
For Example: my good income give me independence to buy more cloths, eat outside, change products as and when required and buy more for luxury. Imagine the load of waste we produce when we eat pizza; count number of cloths you feel are not worth wearing when you have money to buy new cloths etc.
Waste generation rate generally increases with increase in GDP. Increase in GDP increases the purchasing power of a country which in turn causes changes in lifestyle, food habits and the consumption pattern etc. High income countries generate more waste per person compared to low income countries due to the difference in lifestyles.
As per census, 2011 a trend has been noticed in the population increase and urban population increase. In 2011, urban population increase was recorded to be 32% however the total population increase was 18%. This is because of higher rural urban drift i.e. the migration of people from rural to urban areas and growing income of people already in urban areas. This all plays very important role in the waste generation scenario which directly increases with increase in urban population.
Chemical Characteristics of Waste
A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.
Proximate analysis is done for the combustible components of MSW which includes four parameters:
- Moisture (drying at 105 0C for 1 h)
- Volatile combustible matter (ignition at 950 0C in the absence of oxygen)
- Fixed carbon (combustible residue left after Step 2)
- Ash (weight of residue after combustion in an open crucible)
Example for the average values of these parameters is given in the table. Food waste consists of maximum moisture content, 5% ash, 4% carbon and 20% volatiles. The parameter plays important role in deciding the thermal methods of waste treatment.
Fusing point of ash
Fusion temperate of ash is the temperature at which the ash resulting from the burning of waste will form a solid (clinker) by fusion and agglomeration. The typical range of this temperature is 1100-1200 0C.
The parameter is important to see the behaviour of fuel (solid waste) is subjected to high temperature.
The ultimate analysis of waste involves the determination of chemical composition of waste. The test evaluate the percentage of Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur and ash present in waste. The parameter is again important to study the gases that will be released if the waste is used as a fuel. The determination of halogens is often included in an ultimate analysis.
The results are used to characterize the chemical composition of the organic matter in MSW. They are also used to define the proper mix of waste materials to achieve suitable C/N ratios for biological conversion processes. The general composition ranges are given in the pie chart.
The major chemical constituent of waste after moisture is carbon followed by oxygen. Nitrogen and sulphur are generally in traces.
Energy content or calorific value and often said as heating value is one of the most important parameter. It refers to the amount of heat 1 kg of waste will produce when it undergo combustion. The parameter plays very important role when waste is treated in Waste-to-energy plants foe electricity generation.
The parameter is determined commercially by using a full scale boiler as a calorimeter and by instrument called bomb calorimeter in laboratory.
Most of the data on the energy content of the organic components of MSW are based on the results of bomb calorimeter tests.
The typical value of calorific values of different variety of waste is given in Table. Plastics, rubber, textiles give really high calorific value but not segregated in India. MSW can give a calorific value of 11000 KJ/Kg if processed properly.
Mixing of waste makes paper, plastic, textile etc wet and thus consume more processing and energy if used in waste to energy plant for energy generation.
Biological Characteristics of Waste
Biological Characteristics of Waste
Though the biological content is seldom studied in waste management and treatment, but can be considered for choosing specific technical methodology.
The properties include studies on cellulose, hemicellulose and lignin content. It also considers fats, sugars, proteins etc in waste.
Impacts of Municipal Solid Waste
Impacts of Municipal Solid Waste
After discussing the physical, chemical and biological character of solid waste; we should now discuss why we are concern??
Why we are worried about waste when we don’t think before throwing it here and there? The answer is very clear that it must be affecting our life and health. Let’s discuss some of the important impacts of waste on environment as well as health.
Improper solid waste management deteriorates public health, degrades quality of life, and pollutes local air, water and land resources. Indiscriminate dumping of wastes and leachate from landfills contaminates surface and groundwater supplies and the surrounding land resources.
Some episode of major health disasters have been correlated with solid waste like it clogs sewers and drains and leads to floods (Mumbai 2006); insect and rodent vectors are attracted to MSW and can spread diseases such as cholera, dengue fever and plague (Surat 1994); Open burning of MSW on streets and at landfills emit pollutants in air (22,000 tons/year of air pollutants into the lower atmosphere of Mumbai city) and Green house gases (methane) emissions from landfills (methane has 21 times more global warming potential than carbon dioxide)
Open Burning of MSW
Open burning is the burning of any matter in such a manner that products of combustion resulting from the burning are emitted directly into the ambient air without passing through an adequate stack, duct or chimney or pollution control devices. The practice is generally followed by
- Waste-pickers for recovery of metals from mixed wastes
- In MSW bins by municipal workers or residents to empty the bins
- Plastic wastes by street dwellers in winters for warmth at night
In addition to open burning of wastes, landfill fires are also common at every landfill due to the build-up of heat inside waste beds due to decomposing organic matter. Methane is released from landfills due to anaerobic decomposition of material, it is a flammable gas. It catches fire as lot of heat is produces from the waste decomposition. For example in Pimpri-Chinchwad, Nashik and Vishakhapatnam landfills. Sometimes, these fires continue for weeks.
Dioxins and Furans are known carcinogenic agents (cancer causing agaents) in case of long term exposure, released when plastic burns at low temperature in streets especially in winters. One of the studies done by National Environmental Engineering Research Institute (NEERI) in 2010 found very high levels of contaminants in air due to open burning of waste and from the landfills in Mumbai. The data is referred in pie chart; maximum concentration of carbon monoxide was recorded due to incomplete combustion of waste in open dumps. Excess of particulates and hydrocarbons were also notices in the lower atmosphere.
Water Pollution due to MSW
Solid waste clogs drains and pollute river in every possible way. The floating matter of solid waste restricts the flow of rivers and slowly releases contaminants in surface water. Together with the threat to surface water, solid waste also pose problems to ground water quality.
Unsanitary landfills can contaminate ground and surface water resources when the leachate produced percolates through the soil strata into the groundwater underneath or is washed as runoff during rains. Leachate is generally a strong reducing liquid formed under methanogenic (anaerobic) conditions, generally contains organic chemicals and heavy metals leached from inorganic wastes. High concentration of Lead (Pb), Cadmium (Cd), Chromium (Cr) and Nickel (Ni) is found in leachate, characterized as toxic for drinking water. Due to its reducing properties (gain of electrons), during percolation through soil strata, it reacts with Iron (Fe) and Manganese (Mn) species underground and reduces them into more soluble species, thus increasing their concentrations in groundwater.
Inhalation of bioaerosols, smoke and fumes produced by open burning of waste, can cause health problems. Toxic materials present in solid waste cause respiratory and dermatological problems, eye infections and low life expectancy.
A less observed side effect of improper SWM in India is the introduction of heavy metals into the food chain through compost from mixed waste. The compost made from the mixed solid waste, introduce heavy metals into the food chain and lead to a phenomenon called “Biomaginification”. Biomaginification is defined as the process whereby the tissue concentrations of a contaminant (heavy metals) increases as it passes up the food chain through two or more trophic levels.
This can damage CNS, circulatory system, liver and kidney dysfunction, anemia, stomach and intestinal irritation and psychological and developmental changes in young children.
Quality of Life
The Global Development Research Center (GDRC) defines Quality of Life (QOL) as the product of the interplay among social, health, economic and environmental conditions which affect human and social development. QOL reflects the gap between the hopes and expectations of a person or population and their present experience. Uncollected waste on the streets, acts as a breeding ground for street dogs, stray animals and other disease vectors. During the rainy season, come across the unpleasant experience of having to walk in ankle height waters mixed with rotting MSW.
This all affects the quality of life and to the aesthetic value of environment.
Impact on climate change
Solid waste management is the third largest emitter of anthropogenic methane in the world, contributing to 3% of the world’s overall green house gas emissions. Methane as discussed earlier has 21 times more global warming potential than carbon dioxide; thus can cause global warming at a large scale. In India, MSWM is the second largest anthropogenic methane emitter.
Largest green house gas emitter among activities which do not add to the economical growth of the country; the statements says that most of the activities that release green house gases are beneficial for economy example industries, mining, dams etc whereas solid waste management is one activity which release excess of GHGs with no economic benefit.
Anoxic conditions inside landfills result in the anaerobic digestion of organic wastes which produces methane as the final gaseous product. Due to anaerobic reactions, landfills emit methane throughout their life time and also for several years after closure.
Land Degradation and Scarcity
Ministry of Finance in 2009, estimates a requirement of more than 1400 sq.km of land for solid waste disposal by the end of 2047 if MSW is not properly handled. This area is equal to the area of Hyderabad, Mumbai and Chennai together. This gives us an India about how big the problem of solid waste disposal is!
Regional approach for landfill, common dumping site for MSW from a cluster of ULBs, regional landfills make it easy to share financial and human resources between ULBs and facilitates proper sanitary landfill disposal of wastes. As per the record approx. 1900 ha of land in Indian States is presently under landfills. Imagine, the condition when we don’t have land for houses and are expected and compelled to use land for solid waste dumping. Moreover the land used for dumping waste gets permanently damaged and infertile for any further use.
With this we end our basics tutorial on solid waste or must say municipal solid waste. In next tutorial we will continue with the Municipal Solid Waste Management, treatment and disposal techniques.
Solid Waste Characterization
Solid Waste Characterization
Waste characterization means analysing the physical, chemical and biological characteristics of waste. The process is rarely done in India; but plays very important role in selecting the correct technology for waste treatment and disposal.
Example – if you have kitchen waste i.e. all organic origin and you select a technology of incineration/combustion then you have to spend more energy on evaporating the moisture content of waste rather than getting benefit in form of energy.
The waste characterization is broadly classified into physical, chemical and biological properties.
Physical Properties of waste
The physical properties can be observed or measured without changing the composition of matter.
Specific Weight (Density)
Specific weight is defined as the weight of a material per unit volume (e.g. kg/m3, lb/ft3). Usually it refers to un-compacted waste (waste should not be compacted, as compaction will change its density). It varies with geographic location, season of the year, and length of time in storage.
Waste is compacted to reduce the volume this make storage and transportation efficient. As you can see in the picture; only 90 kg of loose waste can be stored in 1 cubic meter however after compaction around 440 kg can be stored in per cubic meter space. This reduces the land requirement in landfill and also in transportation.
Example - Food wastes has density in a range of 130-480, paper and plastics in range 40 – 130 kg m3
The moisture in a sample is expressed as percentage of the wet weight of the MSW material. It is very important for deciding the treatment technology. Food waste consists of 50-80% of moisture content while paper and plastics consist of only 4-10 % of moisture content.
The approximate ranges of various solid waste is given in the table below:
Particle Size and Distribution
The size and distribution of the components of wastes are important for the recovery of materials, especially when mechanical means are used, such as trommel screens and magnetic separators.
The size of waste components can be determined using the following equations:
Sc = L ; Sc = (L+w)/2; Sc = (L+w+h)/3
Sc : size of component, mm ; L : length, mm ; W : width, mm ; h : height, mm
Field capacity of waste is defined as the total amount of moisture that can be retained in a waste sample subject to the downward pull of gravity. Field capacity is critically important in determining the formation of leachate in landfills. It varies with the degree of applied pressure and the state of decomposition of wastes, but typical values for un-compacted wastes from residential and commercial sources are in the range of 50 - 60%.
Technically, in solid waste management the permeability can be defined as rate of diffusion of liquid and gas through solid waste. The permeability (hydraulic conductivity) of compacted solid waste is an important physical property because it governs the movement of liquids & gases in a landfill. The property is very similar to one we study in case of soil, only difference is; here we are talking about solid waste rather than soil.
Permeability depends on -
- Pore size distribution (the size of pores in waste)
- Surface area (area exposed to flow of liquid)
- Porosity (total macro and micro pores in waste)