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Biodegradable waste is a type of waste that generally originates from plants or animal sources and has the capability of getting broken down by living organisms. Biodegradable waste include municipal solid waste, green waste, food waste, paper waste and biodegradable plastics. Other biodegradable wastes include human waste, manure, sewage, slaughterhouse waste.

Biodegradable Waste can be converted into useful products by composting, or energy by waste-to-energy processes such as anaerobic digestion and incineration. Anaerobic digestion converts biodegradable waste biogas and soil amendment. Incineration as well as biogas can be used to generate electricity and/or heat for district heating.

S4E: Strengths & Expertise
  • 20 years of vast experience in Bio-Degradable Waste Management
  • Waste management of Kitchen waste, Agriculture waste, Animal Dung, Night soil, Urban & Industrial Waste to generate energy through Anaerobic treatment methodology
  • Anaerobic treatment produces Bio-gas and highly enriched digested slurry
  • Bio-gas energy can be used for Thermal (Heating), Mechanical (Pumping) as well Electrical (Lighting)
  • Enriched digested slurry is used to produce rich vermi-compost, which is later used for producing organic food products.
  • Implementation of numerous projects for Waste management and Vermi composting in India

Technological Methods for setting up of waste-to-energy projects
   
  • Anaerobic Digestion/ Biomethanation
  • Combustion / Incineration
  • Pyrolysis / Gasification
  • Landfill Gas Recovery
  • Densification/ Pelletization
  • Plasma Arc Technology
 
Advantages of setting up of waste-to energy projects are :
  • The quantity of waste gets reduced by nearly 60% to 90%, depending upon the waste    composition and the technology adopted
  • Demand for land, which is already scarce in cities, for land filling is reduced;
  • The cost of transportation of waste to far-away landfill sites gets reduced; and
  • There is net reduction in environmental pollution
  • Apart from generating power from the waste, the slurry produced from biomethanation technology acts as a good fertilizer
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Bio-degradable Waste Management Program
 
Land Filling
  • Land filling is commonly used method to manage waste
  • Not suitable for recyclable and bio-degradable wastes
  • Disturbs surrounding environment by creating odour and germs
  • Requires properly designed huge land space far from the city or residential area.
  • Expensive transportation
  • Inefficient landfill gas recovery process yields only 30-40% of the total amount of gas actually generated.
  • Spontaneous ignition/ explosions may occur due to possible build up to methane concentrations in atmosphere.
 
Incineration
Incineration is a waste treatment process that involves the combustion of organic materials and/or substances at high temperatures known as ‘thermal treatment’ that converts the waste into incinerator bottom ash, flue gases, particulates, and heat, which can in turn be used to generate electric power.
Advantages:
  • Suitable for high calorific value waste (paper), hospital wastes
  • Thermal energy recovery for direct heating/ power generation
  • Relatively noiseless and odourless
  • Low land area requirement, can be located within city limits, which is reducing cost of waste transportation
  • Hygienic
Disadvantages:
  • Least suitable for high moisture content / low CV wastes and chlorinated wastes
  • Excessive moisture and inert content in waste affects net energy recovery
  • Auxiliary fuel support may be necessary to sustain combustion
  • Toxic metals may concentrate in ash
  • In addition to particulates, SO2 and NOx emission, chlorinated compounds, ranging from HCL to organo-compounds such as a dioxins and heavy metals are a cause for concern, which require elaborate pollution  control equipment
  • High capital costs. Land Filling
 
Anaerobic Digestion
Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen, used for industrial or domestic purposes to manage waste and/or to release energy. It is widely used as part of the process to treat wastewater. As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere.
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In this process, organic fraction of the wastes is segregated and fed to a closed container (biogas digester) where in the presence of methanogenic bacteria and under anaerobic conditions, it undergoes bio-degradation producing methane-rich biogas and effluent.
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Biogas mainly consists of methane (60-75%) and carbon dioxide (25-40%) besides small quantities of NH3 and H2S and has calorific value of about 5000 kcal/m3.
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Depending upon the waste composition, the biogas production ranges from 50-150m3/tones of wastes.
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The biogas can be utilized either for cooking / heating applications or for generating motive power or electricity through dual gas engines, low-pressure gas turbines or steam turbines.
   
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Why Anaerobic Digestion?
  • Generation of gaseous fuel
  • Can be done on a small scale
  • No external power requirement unlike aerobic treatment
  • Enclosed system enables all the gas produced to be collected
  • Green house gas emission to the atmosphere is avoided
  • Free from bad odour, rodent and fly menace, visible pollution and social resistance
  • Modular construction of plant and closed treatment needs less land area
  • Production of biogas and high-grade soil conditioner
Process of Converting Waste to Energy
  • Separated Bio-degradable waste is first taken to waste handling platform, from where all the waste taken to segregation chamber
  • All unwanted waste is separated and only useful bio-degradable waste is later sent to mixing chamber
  • Solid waste is crushed in crusher and mixture in mixing chamber and taken to pre-digestion chamber
  • Pre-digestion chamber activate solid-waste for further treatment by making bio-degradable waste pulp.
  • Pulp is now taken to main anaerobic chamber for final treatment
  • Bio-GAS energy is bi-product of this treatment, which is used for Thermal (Heating), Mechanical (Pumping) and Electrical (Lighting) purpose.
  • Digested Slurry is now taken to slurry-pit, where we separate recycle water and remaining slurry is odour-less, and completely safe for the environment.
  • The organic contents are high in remaining digested slurry, which we can directly use for making VERMI COMPOST.
 
Energy from Municipal Solid Waste (Bio-Degradable)

Solid waste generated at domestic level is the single largest component of all wastes generated in our country. A number of research studies have shown that somewhere 300 to 600 grams of solid waste is generated per person per day in our country.

http://www.s4e.co.in/images/spacer.gifEventually, Municipalities everywhere face the problems of waste collection, processing and disposal or treatment of voluminous solid waste produced by the cities. Moreover, the rains and humidity on the garbage promotes the bacterial multiplication and enhances the spread of infectious diseases. Due to their rich organic contents, the solid waste can be a good resource to produce manure & energy. It has been estimated that about more than 100 MW equivalent power could be generated from urban & municipal waste alone. This potential is likely to increase further with our economic growth.
Local Advantages
  • Reduces costs and risks associated with landfills
  • Additional source of revenue
  • Stimulates your local economy
  • Creates jobs
  • Money stays at home.
  • Reduces petroleum dependence
  • Helps meet alternative fuel mandates.
Environmental Advantages
  • Eliminate landfills- This process does not generate residual waste, thereby eliminating the need for new landfills
  • Ground water- Risk of contaminated ground water is eliminated
  • Render incinerators obsolete- Existing incinerator plants can be retrofitted into our process, eliminating the ash disposal and emissions problems inherent with incinerators.
  • Air and water emissions are below EPA standards-Recovered energy- The energy produced by the process (electricity or ethanol) is recovered from discarded materials.
Recent Developments in Municipal Waste Management
  • Notification of Municipal Solid Wastes (Management and Handling) Rules of 2000 necessitates all Class I cities to provide proper treatment and disposal facilities for MSW;
  • Twelfth Finance Commission has recommended that at least 50% of the grants provided to States for the ULBs should be utilized to support the cost of collection, segregation and transportation. Segregated wastes require relatively simpler and less expensive equipment and devices for conversion into energy;
  • Initiatives being taken under National Urban Renewal Mission are expected to give a major boost to the efforts for improving waste management in 60 large cities; and,
  • Hon’ble President of India has given a call for setting up waste-to-energy projects, like the one in Hyderabad, in all the cities of the country.
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