Solid Waste Management

The year 2020 has opened a Pandora’s Box of natural and man-made disasters for the world. Most of these are a consequence of utter callousness and negligence by humankind. Rapid urbanization and industrialization have led to exploitation of limited natural resources and land. It has also led to severe pollution problems. As a result of this, efficient solid waste management is one of the greatest challenges the world faces today.

Solid waste management could be described as the collection, treatment and disposal of generated waste. Better understanding of waste and keeping abreast with the latest technologies allows us for efficient waste management by reusing, recycling and upcycling of solid waste.

Despite all the available technologies there are several challenges faced for effective solid waste management like administration, social problems, and financial sustenance.

With the uncontrolled rise of industrialization and human population, the rate of waste generation has grown exponentially. Over the past few decades, any material that served its purpose would be disposed off without a second thought and eventually end up at a municipal dumping site – unsegregated. This lack of segregation and appropriate disposal /  treatment has led us to one of the greatest crises we face today. So how do we tackle the Goliath that is solid waste management today? Currently, many countries seek innovative solid waste management strategies that are low cost, easy to implement, decentralized, effective and can be implemented with ease in the existing situation. Not just this, all solid waste management strategies must be able to cope with and accommodate the possibility that waste generation may still keep increasing in the future.

With rapid urbanization and archaic solid waste management strategies, the country is facing a massive solid waste management challenge. India has a population of roughly 1.3 billion out which nearly 440 million people live in urban localities. A cumulative total of 62 million tonnes of municipal solid waste is being generated in India per annum. Only 43 million tonnes (MT) of the waste is collected out of which a staggering 75% of segregated waste is dumped in landfill sites.

The honourable Prime minister’s ‘Swacch Bharat Abhiyaan’ aims to drive the country’s citizens, municipalities and industries towards being more environmentally responsible and encouraging them to move towards sustainable waste management. Solid Waste Management (SWM) today is an intrinsic component of keeping our cities, towns and villages clean. However the biggest obstacle in this system is the lack of discipline in waste segregation the most critical component in ensuring the rapid conversion of landfill garbage into composted material. Poor waste segregation has led to rapid saturation of land filling sites, along with a plethora of related issues.

Improper solid waste management has known to have a plethora of environmental impacts but apart from that it also has health and financial impacts as well.
Untidy surroundings- Due to improper or delayed waste collection, poor or no segregation, improper treatment and disposal by municipal solid waste management teams, the waste piles end up emitting foul odor, attracts insects and stray animals which becomes nuisance for the society at large.

Health risk- Improper solid waste management can affect the health of waste disposal workers, rag pickers, people living & working in nearby vicinity. The exposure to pathogens, toxic gases, or harmful chemicals can lead to various infections, skin irritation, and respiratory issues.

Disease carrying vectors- Inappropriate dumping of organic material leads to rotting under unhygienic conditions. Such a place attracts pests and becomes their breeding ground. Such pests become vectors for disease carrying germs present in the waste that can lead to an epidemic outbreak.

Soil and groundwater pollution- When the organic waste degrades it releases moisture laden with organic and inorganic load known as leachate. It is highly nutrient rich and hard to degrade. This leachate can mix with various toxic compounds waste oils and chemicals. The leachate from landfills continually percolates into the ground and can contaminate soil as well as ground water, rendering it polluted. This is one of the glaring examples of how improper solid waste management can irreversibly affect our natural resources.

Toxic gases- Gases like hydrogen sulphide from anaerobic decomposition, accidental burning of refrigerant gases, hazardous wastes like pesticides, heavy metals, cleaning solvents, radioactive materials, e-waste and plastics mixed up with paper can produce dioxins, furans, polychlorinated biphenyls, and other gases. These gases are hazardous, corrosive and a bane to all living organisms.

Impact on Animals and aquatic life- Consumption of plastic or any toxic garbage can lead to death amongst stray animals and birds. Chemicals released through leachate can travel to nearby waterways can be toxic to aquatic life.

The usual practice of waste disposal at landfill site is unloading of waste and piling it up till there is no further space available. We have understood how an inefficient solid waste management can impact our health, environment and incur us with financial loss. It becomes necessary to operate the allocated landfill site efficiently to minimize health risk, make the process cost effective and increase the capacity of landfill and resource recovery at much higher rate.

Decentralised segregation and disposal of waste comes first and foremost when one thinks of any solid waste strategy. The biggest hindrance in societies today is the lack of willingness to do something so simple and straight forward. If every person could efficiently segregate and reuse, upcycle, recycle and reduce their own waste, it would only be a matter of time before our waste management woes would be halved!

Currently municipal bodies in India have begun enforcing compulsory segregation of waste and have encouraged people to handle their own biodegradable waste. Read more about this here

Landfills are the most basic solid waste management strategies that have been used for the past few decades. However poor and ignorant implementation of this strategy has had disastrous consequences for most countries. The reasons for failure range from inappropriate allocation of land, to exponential increase in garbage dumped everyday. The greatest reason however, is the non-segregation of waste.

Waste can basically be divided into two categories:

1. Biodegradable waste
2. Non- biodegradable waste

There are various waste fractions generated from different source and different activities. These are primarily divided into organic and non-organic waste. The entire premise of effective solid waste management is based on the effective segregation of waste. The waste fraction that are biodegradable are known as organic like food and kitchen waste, garden waste, market waste food industries, wood processing, agricultural waste etc.  and the waste that are non-biodegradable are known as non-organic waste like construction waste, health care waste, e- waste, plastic waste, metal waste etc.

From the perspective of global solid waste management outlook, it is evident that countries with high per capita income tend to have increased waste generation while developing countries tend to generate less waste. Hence it is clear that urbanization, lifestyle and high income level has some influence on the quantum of waste generation. The treatment process for waste fraction depends on the type of waste. In many countries the organic waste generation can be as low as 50% of the municipal waste generation to as high as 80% of it in developing countries.

The load of organic waste, moisture content and density of waste is higher in countries with low per capita incomes when compared to countries with high per capita incomes, whereas the consumption of paper, plastic and packaging waste is much higher in high income countries. Municipal waste is a mixture of organic and non-organic waste. The source of the waste also varies between residential waste, industrial waste, commercial waste, construction and demolition waste, agriculture and biomedical waste.

Organic / Biodegradable waste – waste from food preparations, vegetables, flowers, dry leaves, grass clippings, tree branches, animal waste, fish waste, Agriculture waste.

The three factors that govern the success of a sanitary landfill are its Location, construction and land distribution.

Location– The accessibility of the site is of utmost importance. The landfill site should be nearby  a majority of the waste collection spots. The area of land chosen should be able to accomodat incoming garbage for a minimum of 40 – 50 years.

Construction– Landfill are not just dumping yards, they require the creation of leachate seepage outlets from underneath the piles. Ideally toxic leachate must be treated before it is disposed off.  Accumulation of toxic / flammable gases within the piles could be trigger for fires or gas seepages. Necessary vents must be added to piles. Physical boundaries need to be constructed to disallow the entry of stray animals.

Land distribution–  A detailed plan of land area usage with time needs to be made. Provision of space for transportation of garbage needs to be kept in consideration as well.

It is estimated that almost seven to ten billion tons of waste is generated per year around the world. The rate of resource consumption is directly proportional to waste generation. The three steps towards efficient solid waste management are: reduce, reuse and recycle. Firstly reduce the production of waste wherever possible, reuse whatever can be used again or recycle the non usable waste to valuable products.  An efficient solid waste management strategy can be described as one where the maximum treatment of biodegradable waste is carried out in cohesion with recycling & upcycling of generated non biodegradable waste.

Biological Treatment

Biological treatment in solid waste management entails the use of living organisms to degrade organic biodegradable waste. The various methods are

1. 1. composting,
   2. vermicomposting,
   3. anaerobic microbial digestion
   4. microbial submerged and solid state fermentation.

Composting technology for Biological Solid Waste Management

Composting technology is a process where organic waste is decomposed by microorganisms under controlled conditions to obtain a nutrient rich product known as compost. This compost can be used as an excellent soil amendment product which improves the quality of top soil used for gardening and farming. Composting helps in creating a valuable product from waste, reducing the volume of garbage directed towards municipal landfills, reduces the risk of vector born epidemics, helps conserve natural resources and is one of the most valuable solid waste management strategies that show a lot of flexibility in implementation. Composting is one of the few solid waste management strategies that can be implemented at individual, community and city level. Different composting processes can be implemented as part of a city’s solid waste management strategies are carried out based on type of waste and volume of the waste.

Use of Traditional Pits

Traditional pits are probably the first known methods of composting carried out as a part of solid waste management. The greatest advantage the method is it requires no infrastructure and minimum expenditure. However they do require a lot of space and run a disadvantage of taking unto 2-3 weeks for decomposition. With the average housing society producing unto 100 kgs of waste everyday and having no spare space to accommodate a composting pit, using this technique as a solid waste management strategy in a city is just not practical. It may be feasible in rural localities where space is not a constraint.  A few more disadvantages include malodour formation, toxic leachate creation and increased pestilence are other issues that are often encountered in this process. Aerating these pits need frequent manual intervention which is an extremely cumbersome process. Incomplete degradation due to ineffective indigenous microbes also is a frequently encountered issue.

Windrow composting

For a large volume of organic waste, windrow process is preferred where the waste is stacked in form of rows of elongated pile. The pile dimensions are usually maintained at 4 to 6 feet in height and width of 14 to 16 feet. Aeration is provided through vented pipes. It can be used for municipal solid waste management at a rural level and for composting agricultural residue. The greatest advantage with this technique is that it does not require elaborate infrastructural inputs. Handling difficulties remain the same as those faced in composting pits.

Bin composting

This method deals with composting small volume of waste at the source itself usually at household or housing society level. The waste collection and composting happens in a perforated bin to allow aeration. The number and size of these bins can be increased depending on the quantum of the waste. They may be required to be turned manually or come equipped with a motor to overturn the waste when required. With proper moisture maintenance and aeration, bin composting is relatively cost effectively and user friendly method of community level biological solid waste management.

In vessel composting

This method involves the composting of waste material inside a vessel under controlled conditions. There is better provision for mixing, airflow and temperature control which helps in accelerating the composting process in this method. This method is usually used for solid waste management at a community level.

Thermocomposting machines offer advantages of complete physical containment as compared to pots and pits. They rapidly reduce the moisture content in the organic waste thereby taking care of the odour as well as promoting aerobic decomposition. If locally made, the cost of employing this technology is substantially reduced. Disadvantages: Relatively expensive.  The resulting compost from these machines tends to of sub optimal quality due to which a curing technique (close to a week) needs to employed, which increases the processing time by a week. They are more prone to breakdown due to the use of cheaper raw materials. They therefore require frequent servicing, ultimately increasing the input cost.

Vermicomposting

Vermicomposting is carried out using combination of earthworms and microorganisms for degradation of organic waste under controlled conditions. This method is usually employed for the biological solid waste management of agro-waste. Earthworms being higher life forms have the heightened capability of digesting complex lignocellulosic matter. The feces of earthworms has this organic matter broken down into much simpler forms, making it easy for microbes to further breakdown into compost. The end product obtained is high quality vermicompost . The drawback with vermicompost is it requires lot of monitoring for the environmental conditions and food material. The excessive worms obtained from this process can be used at nutritious feed for fishes. Vermicompost still remains one of the most efficient solid waste management techniques in gardening and agriculture management today.

Anaerobic Digestion

The term anaerobic digestion itself explains that the microbial degradation of the biodegradable waste occurs in the absence of oxygen. The system is also known as biomethanation or biogas formation as anaerobic digestion produces gases such as methane and carbondioxide as its end product. Methane is a combustible gas that is valuable as it can be used as a renewable source of energy. Anaerobic digestion is one of the most important methods of solid waste management strategies because it is a solution to the ongoing global energy crises. A major set back of anaerobic digestion is the major investment in infrastructure and the complexity of the process.

Thermochemical conversion

Thermochemical conversion is converting the process of converting lignocellulosic waste material into an energy source by subjecting it to heat treatment. The advantage of this solid waste management technique is its substrate non-specificity. The disadvantage is relatively high investments in infrastructure and energy expenditure. Most common methods for thermochemical treatment are:

Pyrolysis– Pyrolysis is decomposition of organic material between temperatures of 300 to 600 C in absence of oxygen under controlled conditions. The duration of the heating process defines the final output. Charcoal , oil and gases are obtained at varying concentrations and are used as energy sources.

Gasification– In gasification, the heating of organic material is carried out above 750 C with a  very low supply of oxygen and for a very short duration, converting the organic waste into various useful gases like hydrogen, methane and carbon monoxide which can be used in various industrial processes and as fuel as well. This solid waste management strategy is highly capital intensive as well as energy intensive.

Combustion –This is common burning process where organic material is combusted in presence of oxygen to use as an energy source for heat generation. Around 97% of world’s bioenergy production is achieved through this solid waste management strategy.

Incineration– Incineration is a combustion process inside a furnace under controlled conditions. The furnace is constructed using bricks that can sustain high combustion temperature and the walls are insulated to avoid heat loss from the furnace. The Heat generated in the system can be used as a source of energy to generate steam using boilers. Electricity generation can also be achieved if a turbine is installed at the plant.

Recycling is the process of converting waste into objects of renewed value to prevent waste of materials, reduce wasteful consumption of virgin raw materials, energy, pollution by decreasing the need for disposal of waste that is not degradable. Recycling is intrinsic to waste reduction today. It has numerous economic as well as environmental benefits as well.