Technical talk is describing various technologies about solid waste treatment and safe disposal :Detailed explanation of waste to energy treatment plant principle, operations and unit processes have been summerized.
2. Introduction
Global and Indian Scenario
Sources of Generation and waste classification
Methods for waste to treatment
Technical aspects: Process and principle
Impact on environment and health
References:
3. Waste to Energy(WTE) Technologies recover the energy from waste.
It is a processing of generating energy in the form of electricity and
heat from the municipal solid waste.
MSW includes: residential, industrial, institutional, C&D, agricultural
etc.
According to the confederation of European waste to energy
plants(CEWEP) Europe treats 50 million ton of waste at WTE plant,
generates an amount of energy that can supply electricity for 27
million people and heat for 13 million people.
1ton MSW can generate up to 750 kWh. Ash 10% of original volume.
4. Apprx.100000MTonnes of waste is generated per day world wide, production
of this waste is expected to be approximate 27 billion tonnes/year by 2050,
1/3 of this waste which will come from Asia( major countries China+ India)
Current status of MSW waste generation in urban India is 62million tonnes
annually , 80% of this waste is disposed of indiscriminately at dump yard in an
unhygienic manner.
Waste generation rate in Urban India will become 0.7kg per person per day by
2025, 4-6 times higher than in 2012. Current-0.2-0.45kg/capita/day on an avg.
This waste has a potential of generating 439MW of power,1.3million cubic
meter of biogas per day or 72 MW of electricity from Biogas and 5.4 million
metric tonnes of Compost.
Morover, 62 million tonnes annual generation of MSW requires 3,40,000
cubic meter of landfill space everyday (1240 hectare per year) if continues to
be dumped.
5. MSW generation Current trends:
CPCB and municipal authority have so far only set up of 349 compost plant,
210 Biomethanation plants, 59-RDF plants, 25 -waste to energy plants in the
country in which many of them above are not even working)
68% of the MSW generated in country is collected in which 28% is treated by
municipal authority merely 19% of the total waste generated is currently
treated, remaining waste is disposed off at dump sites/landfill sites untreated.
7. Solid Waste Types
Municipal solid waste commonly known as trash or garbage, refuse or rubbish
is a waste type consisting of everyday items we consume and discard.
It predominantly includes food wastes, yard wastes, containers and product
packaging and other inorganic wastes from residential, commercial,
Institutional and industrial sources.
Organic waste –food scrapes, wood, rubber, canteen or cafeteria wastes, news
papers, tires, furniture etc.
Municipal solid waste does not include industrial wastes, agriculture waste and
sewage sludge.
Biodegradable waste-food and kitchen waste, green waste, paper (can be
recycled);
Recyclable material-Paper, glass bottles, cans, metals, certain plastics, etc.;
Inert waste- dirt, rocks, debris, C & D waste
Composite waste-waste plastics, tetra packs, waste closing
8. Medication or drugs,
E-waste,
paints,
chemicals,
light bulbs or fluorescent tubes,
spray cans,
fertilizers and pesticides and their containers,
batteries,
shoe polish materials.,
Waste is solid substances generated as a result of human activities, and, being no
longer of value for the respective economic, physiological or technological
process, are removed from it.
Waste to energy recovery plant
waste-to-energy plant converts solid waste into electricity and/or heat - an
ecological, cost-effective way of energy recovery. The energy plant works by
burning waste at high temperatures(850) and using the heat to make steam. The
steam then drives a turbine that creates electricity.
.
10. Soil contamination-due to Soil acidity
Water contamination-Ground and
surface water contamination by leachate
generated by waste dump .
Air contamination-due to release of to GHG
by landfill.(CO2,CH4,N2O,HFC,SF6,PFC)
12. Severe illnesses, including encephalitis and dengue fever, have been attributed
to disease-carrying mosquitoes originating from scrap tire piles.
Illegal dumping can impact proper drainage of runoff, making areas more
susceptible to flooding when wastes block ravines, creeks, culverts, and
drainage basins.
In rural areas, open burning at dumpsites containing chemicals may
contaminate wells and surface water used as sources of drinking water.
Dumpsites that caught fire, either by spontaneous combustion or, more
commonly.
Rodents, insects, and other vermin attracted to open dumpsites may also pose
health risks. The health risks associated with illegal dumping are significant for
rag pickers and residents living nearby
Areas used for illegal dumping may be easily accessible to people, especially
children, who are vulnerable to the physical (protruding nails or sharp edges) and
chemical (harmful fluids or dust) hazards posed by wastes.
(Source: Illegal Dumping Prevention Guidebook. US EPA. EPA905-97-001)
13. 1. Segregation at source-Reduce, Reuse, Recycles,
2. Collection and transportation
3. Treatment and Energy Recovery-Waste which can be heated, converted processed
into gas, fuel and electricity.
4. Scientific land filling for inert, hazardous and Toxic.
Criteria for selection of WTE technology
1. Waste characterization-type ,quantity and waste content.
2. Environment and health-CO2 control, DXNs control, Emission control, landfill
control.( Air, water and land pollution overall)
3. Economy-cost control, profit and growth, relative capital cost, O &M.
4. Energy and efficiency – energy recovery, high efficiency, utilization and safe.
Power generation- Efficiency(50-60% based on VOC)
14. 3 E’s Technology selection Criteria
Environment
Economy
Energy
• Emissions control
• Minimize Landfill
Cost Vs. Benefit
Social & Financial
Energy recovery
Efficiency
Selection of waste to energy technology is based on scale of waste to be processed,
existing emission norms, energy recovery and economic factors
15. Waste to energy recovery
Stock pallet waste- furnaces-Burn- Heat-steam-Turbine-Electricity, Components:
furnaces, turbines, heat exchanges boilers, generators etc.
The technology options available for processing the Municipal Solid Waste(MSW)are
based on either Bioconversion or thermal conversion
The Bioconversion process is applicable to the organic fraction of wastes, to form
compost or to generate biogas such as methane (waste to energy) residual
sludge(manure).
Various technologies are available for composting such as aerobic, anaerobic & vermi-
composting.
The thermal conversion technologies are incineration with or without heat recovery,
pyrolysis and gasification, plasma pyrolysis and pelletization or production of Refuse
Derived Fuel(RDF).
17. Technologies for conversion of WtE
Waste to energy technologies recover energy from organic fraction of waste using either
biochemical or thermo chemical processes
Waste
Thermo chemical
Biochemical
Crushing, compressing,
pelletizing
Incineration
Conventional/
Plasma gasification
Pyrolysis
Biomethanation
Fermentation
Refuse derived fuel
Flue gas/steam
Syngas
Syngas & Bio-oil
Biogas
Ethanol
Mechanical
Electricity
Chemicals
Hydrogen
Transport fuel
Feed stock for
thermal process
Heat
Concept Process Energy carrier Application
18. Incineration
• Incineration involves combustion of
waste at very high temperatures in the
presence of excess oxygen
• Results in the production of ash, flue gas
and heat energy
• Incineration is feasible for unprocessed
or minimum processed refuse besides for
the segregated fraction of the high
calorific waste
Advantages
• Immediate reduction in volume and weight
by about 90% and 75% respectively
• Stabilization of waste
• Energy recovery
Challenges
• Management of dioxins and furans formed
in incineration
Incineration is a maturated technology for processing and energy recovery from waste
19. Gasification
• Gasification is thermo chemical conversion of
carbonaceous fraction of waste into syngas (CO,
H ,2 CH4 and CO )2 in oxygen deficient
environment and at high temperatures (650-
1600°C)
• Inorganic fractions present in the waste
converted to ash and can be safely land filled
• Syngas can be used for variety of applications
such as generation
chemicals, hydrogen
electricity, Bio fuels,
Advantages
• Immediate reduction in volume and weight
• Environment friendly
• Energy efficient
Challenges
• Higher initial cost compared to incineration
• Skilled labour is required
Gasification is more efficient and environmental friendly technology than incineration
for conversion waste into energy
20. Plasma gasification
• Plasma is an ionized gas where the atoms of the
gas have lost one or more electrons and have
become electrically charged
• Waste introduced into the plasma field, where
intense heat breaks down the waste molecules
into simple compounds
• Waste converted into fuel gases with high
calorific value and inert solid slag in the
temperature range 1200 – 2000 C0
Advantages
• Immediate reduction in volume and weight
• Converts waste to inert vitrified slag
• Suitable for low calorific value waste
Challenges
• Expensive compared to
conventional gasification
• Skilled labor is required
Plasma gasification is an emerging waste to energy technology for processing of variety
of waste such as MSW, medical waste, agro waste etc.
21. Pyrolysis
• Pyrolysis is thermal decomposition of organic
fraction of waste in the absence of oxygen
• Pyrolysis is an endothermic process and usually
required heat is generated by burning of some
of the product gas in separate heater
• Pyrolysis produces three components:
Fuel gas: A mixture of fuel gases
Fuel oil: Consisting of tar, pitch, light oil etc.
Char along with the inert materials in the
waste feed
Advantages
•
Immediate reduction in volume and weight &
less space requirement
• Stabilization of waste
• Easy to operate
Challenges
• Pyrolysis oil is unstable & needs
further processing
• Energy is distributed in 3 fractions
Pyrolysis of waste plastics is an upcoming technology for conversion plastics to either
liquid fuels or chemicals
22. Hydrolysis and fermentation
• First step in conversion of cellulosic
fractions of waste to ethanol is hydrolysis
of cellulose and hemicellulose into simple
sugars using chemicals / enzymes
• Second step is fermentation of sugars into
ethanol followed by distillation
• Lignin is by a product in this process
Advantages
• Generation of drop-in bio-fuels
• Stabilization of waste
• Energy recovery
Challenges
• High capital and O & M Cost
• Convert only cellulosicand hemi cellulosic
fractions
• Conversion of polysaccharides to sugars is
complex
Major challenges in hydrolysis and fermentation are integration of hydrolysis and
fermentation into single step, and availability of low cost enzymes –Biochemical process
23. Refuse Derived Fuel(RDF)
• RDF is produced by removing recyclables and noncombustibles from waste
and producing a combustible material by shredding, compressing and
pelletization of remaining waste
• RDF is easily storable, transportable, and more homogeneous fuel for either
steam/ electricity
furnaces/boilers
generation or as alternate fuel in industrial
• RDF may also be utilized in co-processing in cement kilns, co-combustion in
coal fired power plants
Advantages
• High calorific value of the waste
Challenges
• Suitable for the areas where large
amount of combustible waste is being
generated
24. RDF process flow scheme
RDF is usually prepared in the form of pellet/ briquette/ fluff from dry high calorific
value combustible wastes
25. Handling and storage of waste: Bunkers, pallets, moving cranes,
storage units.
Waste incineration: Furnace, Boilers with HE and Air condensers,
closed loop of water supply feeding station.
Flue gas treatment unit: electrostatic precipitator, bag filters,
addition of lime and activated carbon process, emission control for
residue(APCR)
Fly ash Chamber and Bottom ash chamber:
Steam Turbine : High pressure turbines, generators, electricity
tower etc.
District heating system: part of steam used for community heating.
Leachte treatment unit: waste water and wet flue gas treatment.
Magnetic tray: On the bottom of furnace, recycled metals, vitrified
glass and other metals
29. Renewable resource
Reduces landfills
Protects clean water supplies
Reduces air pollution and smog
Reduces ground and surface water pollution
Reduces greenhouse gases
◦ Carbon dioxide
◦ Methane
30. Illegal Dumping Prevention Guidebook. US EPA. EPA905-97-001)
Global status report 2016 on 22nd conference of parties prepared by GABC(UNFCCC)
World green building trends summit 2016 on CO2 emissions.
CPCB.
MNRE
CPHEEO manuals on solid waste management, MOUD, New Delhi
NGT Guidelines for sold waste dumping and disposal.
MOEFCC reports on global climate change.
ADB DPR on Thane Municipal corporation and Vishakapattnam.
Solid waste management rules, Center for Environment and Development, Thiruvananthapuram
(CED),MOUD.
Energy Efficiency and Renewable Energy, Biomass Program: Biomass Basics, November 2006,
http://www.eere.energy.gov/biomass.
National Renewable Energy Laboratory, Biomass Research, November 2006, http://www.nrel.gov/biomass