This document discusses various waste-to-energy technologies, including thermo-chemical and bio-chemical conversion methods. It begins by introducing waste-to-energy as a process of generating energy from treated waste in the form of electricity or heat. Major thermo-chemical conversion methods discussed include incineration, combustion, gasification, and pyrolysis. Bio-chemical methods examined are microbial fuel cells, biomethanation, and biogas production from landfills. The document provides details on the processes involved in each method and their advantages/limitations. It aims to review waste-to-energy technologies that could help address environmental issues from waste and fossil fuels in India.

1. WASTE TO ENERGY TECHNOLOGY
REVIEWS IN INDIA
Haritha M
Assistant Professor
Dept. of Civil Engg.
1

2. Introduction
 Form of energy recovery
 Process of generating energy in the form of electricity or
heat from primary treatment of waste
 Waste-to-Energy means the use of modern combustion
technologies to recover energy, usually in the form of
electricity and steam
 New technologies -reduce the volume of the original waste by
90%, depending upon composition and use of outputs
2

3. Why we go for WTE?
 Can address two sets of environmental issues at one
stroke
 Land use and pollution from landfills
 Environmental perils of fossil fuels
 Quite expensive
 Some can be applied economically
3

4. Major Constraints in WTE
 Still a new concept in the country
 Lack of financial resources with Municipal
Corporations/Urban Local Bodies
 Most of the proven and commercial technologies in respect of
urban wastes are required to be imported
 Lack of conducive policy guidelines from State Governments
in respect of allotment of land, supply of garbage and power
purchase
4

5. Limitations of WTE
 Waste low energy density than fossil fuels-cost of energy
production increased-energy efficiency reduced
 Locating the waste processing plant near the waste resources
reduce problem
 Incomplete burning of waste - production of noxious gases, such
as carbon monoxide and nitrogen oxides.
 Solution-control the process to minimise their production.
 Countries where WTE industry not established-the cost of
converting waste to energy is higher than in other countries.
5

6. WTE Technologies
Thermo-chemical
conversion methods
Incineration
Combustion
Gasification
Pyrolysis
Bio-chemical
conversion methods
Microbial fuel cell(MFC)
Biomethanation
Biogas production from
landfills
6

7. THERMO –CHEMICAL
CONVERSION METHODS
7

8. Incineration
 Incineration is a thermal process - combustible components
thermally oxidized to produce heat energy
 Other products include bottom ash, fly ash, and flue gas, in
which are found a number of regulated pollutants
8

9. Incineration(contd..)
 Bottom ash is that component of the fuel not
converted to gas
 Comprised of inorganic materials -metal oxides and
unburned carbon ,remains in the char bed until
removed from the bottom of the combustor
 Smaller ash particles -entrained in the flue gas
removed along with VOCs &SVOCs and acid gas
constituents
9

10. Incineration(contd..)
 Several processes - removal of particulates from the
flue gas before released into atmosphere.
 Flue gas clean-up units commonly found in MSW
incineration plants include either a dry or wet acid gas
removal unit or scrubber, and a bag house
 For additional clean-up of the flue gas, carbon and/or
lime can be injected into the gas stream in the bag
house
10

11. Combustion
 Combustion is one of the oldest ways to convert fuel to
useful energy
 Combustion of biomass is a process in which oxygen reacts
with carbon in the fuel and produces carbon dioxide, water
and heat
 Gaseous combustion products include nitrogen oxidants,
carbon monoxide and aromatic compounds
 In a combustion reactor or furnace, raw material reacts with
oxygen in high temperature (> 800 °C) 11

12. Combustion(contd..)
 Initial step drying-followed by pyrolysis and gasification
 Final step : combustion where overall efficiency is highly
dependent on temperature, available O2 and raw material
properties
 Can be utilized to produce heat for households and for
industrial processes
 Simple example combustion of hydrogen and oxygen into
water vapour
12

13. Combustion(contd..)
 High-temperature exothermic redox chemical reaction between a
fuel and an oxidant usually atmospheric O2
 Combustion processes can be divided to batch and continuous
processes
 In households, wood-stove is a conventional batch combustion
process
 Combustion can also produce gaseous and liquid fuels
 Ash - utilized as fertilizer
 A complicated sequence of elementary radical reactions
13

14. Combustion(contd..)
 Quality of combustion can be improved by the designs
of combustion devices, such as burners and internal
combustion engines
 Further improvements are achievable by catalytic
converters
14

15. Gasification
 Controlled partial oxidation of a carbonaceous material
achieved by supplying less O2 than the stoichiometric
requirement
 central process between combustion and pyrolysis -proceeds
at temperatures ranging between 600 and 1500 0C
 widely used to produce commercial fuels and chemicals
 striking feature -ability to produce a reliable, high-quality
syngas product used for energy production
15

16. Gasification(contd..)
 Conventional fuels such as coal and oil, wastes :petroleum
coke, heavy refinery residuals, municipal sewage sludge
successfully used in gasification operations
 Process uses an agent, either air, O2, H2 or steam to convert
carbonaceous materials into gaseous products.
 First, the biomass is heated to around 600 degrees
 The volatile components, such as hydrocarbon gases,
hydrogen, CO, CO2, H2O and tar, vaporize by various
reactions 16

17. Gasification(contd..)
The remaining by-products are char and ash
For this first endothermic step, oxygen is not required
Second step, char is gasified by reactions with oxygen, steam
and hydrogen in high temperatures
endothermic reactions require heat, which is applied by
combusting some of the unburned char
Main products of gasification are synthesis gas, char and tars
17

18. Gasification(contd..)
 Gas mainly consists of CO, CO2,H2
 synthesis gas -utilized for heating or electricity
production
 Used for the production of ethanol, diesel and
chemical feedstocks
18

19. Pyrolysis
 Pyrolysis is thermal decomposition occurring in the absence
of oxygen
 First step in combustion and gasification processes followed
by total or partial oxidation of the heated material
 In the first step, temperature is increased to start the primary
pyrolysis reactions
 Volatiles are released and char is formed
 Finally pyrolysis gas is formed
19

20. Pyrolysis(contd..)
 The main product of slow pyrolysis is char or charcoal
 In slow pyrolysis biomass is heated to around 500 degrees for 5 to 30min
 Fast pyrolysis results mainly in bio-oil
 The biomass is heated in the absence of oxygen and the residence time
is 0.5 to 5s
 Vapors, aerosols and char are generated through decomposition
 After cooling bio-oil is formed
 The remaining non condensable gases used as a source of energy for the
pyrolysis reactor 20

21. BIO-CHEMICAL
CONVERSION METHODS
21

22. Microbial Fuel Cell(MFC)
 Devices that can use bacterial metabolism to produce
an electrical current from a wide range organic
substrates
 Electrons produced by the bacteria from these
substrates are transferred to the anode and flow to the
cathode linked by a conductive material containing a
resistor, or operated under a load
22

23. MFC (contd..)
23

24. MFC (contd..)
 Metal anodes consisting of non corrosive stainless steel mesh can
be utilized
 Copper is not useful due to the toxicity
 Most versatile electrode material is carbon, available as compact
graphite plates, rods, granules etc..
 (K3[Fe(CN)6]) electron acceptor in MFC
 Advantage of ferricyanide :low over potential using a plain
carbon cathode, resulting in a cathode working potential close to
its open circuit potential.
 Disadvantage: insufficient reoxidation by oxygen, which requires
the catholyte to be regularly replaced. 24

25. MFC (contd..)
 Can produce enough electricity to power ocean monitoring
devices
 Can work in marine settings when the anode is buried in
anaerobic marine sediments and cathode installed above the
sediment in the O2 rich water
25

26. Biomethanation
 Organic fraction of the waste is segregated and fed into a
closed container ie,biogas digester
 Digester- segregated waste undergoes biodegradation in
presence of methanogenic bacteria & under anaerobic
conditions, producing methane-rich biogas &effluent
 Biogas used either for cooking/heating applications, or for
generating motive power or electricity.
26

27. Biomethanation(contd..)
 Four key biological and chemical stages of anaerobic
digestion:
o Hydrolysis
o Acidogenesis
o Acetogenesis
o Methanogenesis
 Hydrolysis: can be merely biological (using hydrolytic
microorganisms) or combined: bio-chemical (using
extracellular enzymes), chemical (using catalytic reactions)
as well as physical (using thermal energy and pressure) in
nature
27

28. Biomethanation(contd..)
 Acetates and hydrogen produced in the first stages can be
used directly by methanogens
 Acidogenesis: further breakdown of the remaining
components by acidogenic (fermentative) bacteria
 Here VFA’s are generated along with CO2,NH3,H2S as well as
other by-products
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29. Biomethanation(contd..)
 Acetogenesis: simple molecules created through the
acidogenesis phase are further digested by acetogens to
produce acetic acid as well as CO2 & H2
 Methanogenesis:methanogenic archaea utilise the
intermediate products of the preceding stages and convert
them into CO2,CH4,H2O
 The remaining, non-digestible organic and mineral material,
which the microbes cannot feed upon, along with any dead
bacterial residues constitutes solid digestate.
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30. Biogas Production from Landfills
 Landfilling -primary method of disposal of municipal solid
waste and debris in the U.S. and many countries
 If left undisturbed, landfill waste produces significant
amounts of gaseous byproducts, consisting of CO2 &
CH4(greenhouse gases)
 increase the risk of climate change when they are released
unimpeded into the atmosphere
 CH4 -useful source of energy
30

31. Biogas Production from
Landfills(contd..)
 Landfill gas captured via collection system-consisting
of series of wells drilled into the landfill and connected
by a plastic piping system
 Gas burned directly in a boiler as a heat-energy source
 Biogas cleaned by removing water vapour and
sulphur dioxide, it can be used directly in internal-
combustion engines, or for electricity generation
31

32. Case Study(Solapur,Maharashtra)
Methodology
The municipal waste used in research was brought directly from the
waste dumping site
 MSW -high moisture content; it was contaminated and heterogeneous
in composition
 MSW -dried to reduce the moisture content in the material and shred
for size reduction
 waste was segregated manually for removal of recyclable materials,
stones and inorganic constituents
waste again separated through magnetic separation for removal of
ferrous and non-ferrous materials
MSW was shredded, classify and powdered 32

33. Case Study (contd..)
Before pelletization, municipal waste has to be processed for
size reduction, adding binder agents and reducing the
moisture content
 secondary shredding was carried out and pellets were
prepared by using PVC pipe size (2 inch X 15 cm)
 pellets were prepared by using starch as a binding agent
Calorific value of the pellet samples was measured by using
the acid digestion method and energy content was calculated
33

34. Case Study (contd..)
Results
 Municipal wastes -cheapest and easily available biomass
wastes, with no cost
 Calorific value of MSW after pelletization is high as
compared to parent composition waste
 MSW pellets :compact, economical have tremendous
market potential in non-coal producing zones
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35. Review on WTE technology in
India
35

36. Conclusion
 Serve the dual purpose of managing solid waste and
generating energy from waste.
 Help in reducing green house gas emission thus preventing
global warming
 Helps in conserving land as land filling of waste requires
larger surface areas
 Earth Engineering Center at Columbia University and
National Environmental Engineering Research Institute have
decided to set-up Waste-to-Energy Research and Technology
Council (WTERT) in India
 responsible management of wastes based on science and best
available technology not on ideology and economics that
exclude environmental costs seem to be inexpensive now but
very costly in the future 36

37. References
1 .Boukelia and Mecibah(2012)“Solid waste as a renewable source of energy:
Current and future possibilities” International Journal of Energy and
Environmental Engineering
2.Mehtab Singh Chouhan et.al(2012) “Review on waste to energy potential in
India”
3.Chauhan Janardan Singh(2014) “International Journal of Chem Tech Research
4. R.Sunderesan et.al (2010) “Waste to Energy Generation from Municipal Solid
Waste in India”
5. Bary Wilson et.al(2013) “ A Comparative Assessment of Commercial
Technologies for Conversion of Solid Waste to Energy”
6.A.Bosmans et.al (2012) “The crucial role of waste to energy technologies in
landfill mining:a technological review”
7. Houran Li et.al (2007) “A state of art review on microbial fuel cells: A
promising technology for waste water treatment and bioenergy”
8. Preeti Jain et.al (2014) “Studies on Waste-to-Energy Technologies in India & a
detailed study of Waste-to-Energy Plants in Delhi”
9.M.Y Azwar et.al (2014) “Development of biohydrogen production by
photobiological, fermentation and electrochemical processes: A review”
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38. THANK YOU
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