Resource-Recovery.pdf for bachelor im CE

Note of Solid waste management

1. Chapter 6
RESOURCE RECOVERY

2. Introduction
What is resource recovery in solid wastes?
•Resource recovery is the selective extraction of disposed materials for a specific
next use, such as recycling, composting or energy generation in order to extract
the maximum benefits from products, delay the consumption of virgin resources,
and reduce the amount of waste generated.
•Resource recovery is a process of recovering energy and reusable materials from
solid waste before their decomposition or landfill.
•Million tones of solid waste is generated everyday due to industrial and domestic
activities and this solid waste was land filled or decomposed earlier without being
reused or extracting the materials that could have been reused.
•Principle of 3R (Reduce, Reuse, Recycle) were followed to tap the hidden energy
potential of the resources by reusing and recycling the materials to the extent
possible.

3. Introduction
•The same principle of 3R is followed here with the following hierarchy:
-Reduce the material consumption
-Reuse the materials
-Recycle the materials
-Incinerate with energy recovery
-Landfill or Decompose
•The effectiveness of informal waste recovery may be enhanced through appropriate
equipment design.
•The public sector may consider involvement in waste recovery and/or leasing of waste
recovery rights.
•Composting is a promising area of resource recovery.
•Landfill gas recovery may be a promising approach to energy recovery.

4. Flow of material in society
•Inputs
-Resources from earth
-Scarp material
-Materials recovered
•Operation
-Processing
-Waste generation
•Outputs
-Produced after consumed
-Dispose of this material as SW or other wastes
-Collect the material in sufficient quantities for energy production
-Collect the material to recycle back into the industry

5. Flow of material in society

6. Waste minimization:
Waste minimization:
•Reduction in resources use
•Selectivity in resources actually required
•Avoiding certain types of resources especially generates hazardous wastes
Way of waste minimization (types)
1. Input change (resource management)
•Less quantity material
•High quality material
•Process modification
•Less hazardous /toxic material
•Easily reusable

7. Waste minimization:
2. Process change: (design and manufacturing management)
•Clean processes and clean technology
•Cost and compatibility of any new equipment
•Producing less waste during the production process
•Good house keeping
•Materials handling and logistic
•Equipment maintenance
•Prevention of emission
•Waste segregation and storage
•More in house recycling of waste materials
•Processing and / or sale of waste as by products

8. Waste minimization:
3. Product change : (product management and marketing)
•Light weighting
•Product substitution, egplastic for glass, steel for aluminum in beverage cans
•Single material construction as opposed to composite products
•Larger containers , economy size items, bulk purchase
•Less sales packing, especially double packing
•Ease recycling
•Extraction by recyclable category
•Ease of disassembly
•Reusable, returnable products
•Better quality longer life and more reliable products

9. Waste minimization:
How can house hold reduce the amount of discarded waste ?
•Buy items that are reusable rather than disposable
•Reuse product containers and purchase beverage in refillable bottles, or use
concentrates
•Select product that are durable, repairable
•Buy bulk or larger sizes
•Avoid containers made of mixed materials
•Compost yard wastes and / or food wastes,/ or use a worm farm
•Buy fresh rather than pre-packed fruit and vegetables
•Donate usable but unwanted items to friends or charities
•Buy products that contain less toxic substances

10. Material recovery facility (MRF)
•Recovery understand as process in which the refuse is collected for further or again useful
purpose.
•Materials can be recovered from:
-drop-off centers
-buy-back centers
-pre-costing
-door to door collection
1.Drop-off centers:
-Locations in neighborhood where commingled or segregated waste are collected from
community
--simple multi container center where one can drop normally inorganic wastes like paper,
plastics, glasses and metal
-Should be simple and not confusing
-May be designed as elegant containers attracting users and matching landscapes

11. Material recovery facility (MRF)
2. Buy back centers
•Provide monetary incentive (kabadias in Nepal)
•An egg against a kilo waste (was a popular slogan in Kathmandu)
3. Pre costing
•For batteries or like waste (cost is added while selling and returned deposited money
when back after use)
•Beer and soft drink bottles are example
4. Door to door collection (scavengers)

12. MRF as SW Processing Techniques
1.waste minimization
2. operation change
3. material change
4. process modification or equipment
modification
5. volume Reduction
6. component separation
a. size reduction, glass crusher, wood
grinders ,
b. size separation or screening
c. density separation or air classification
d. magnetic / electric separation
e. materials handling
7. MRF>>> material separation system
a. automatic bottle sorting system
b. Treatment
8. role of technicians /engineers
a. what, why , how , >>>>resources recovery
from SW

13. Material recovery facility MRF
Unit operation in MRF
Processing technique helps to:
•Improve efficiency of SW disposal (increase density)
•Recover resources (separation)
•Preparation for recovery of conversion products (eg. Shredding, incinerate,
composting)
Processes used:
•Mechanical volume reduction by compaction
•Thermal volume reduction
•Manual or mechanical component separation (usually labourintensive )

14. Material recovery facility MRF
•Tipping floor: An unloading
area for vehicles that are
delivering MSW to a transfer
station or incinerator.
•Conveyor belt: A conveyor
belt or a conveyor is a
continuously-moving strip of
rubber or metal

15. Figure: Separation Tank

16. Material recovery facility (MRF)
Size reduction Hammer mill (shredding MSW)
Shear Shredders aluminum, tyres etc.
Tub grinders for yard waste
Size separation Reciprocating types screen, trommel screen, disc screen, vibrating
screen
Density separation Air classifier ,inertial separation, floatation, heavy
media separation
Electric and
magnetic field
separation
Separation of plastic, ferrous
Magnetic separation ,electrostatic separation, eddy current
separation
Materials handling Conveyors, storage bins, forklift, loaders (front end)trucks
appropriate types
Belt conveyers, pneumatic conveyors

17. Material recovery facility (MRF)
1.Mechanical size and shape alteration
•Alteration of size and shape
•Equipment used
•Hammer mill
•Shredder
•Roll crusher
•Grinders
•Chippers

18. Material recovery facility (MRF)
2. Mechanical component separators
•To separate recoverable material
•Vibrating screen
•Trommel (rotating drum)
•Disc screen
3. Air classification (density separation)
•to separate heavier and lighter material
4. Magnetic and electro magnetic
separators
•to separate ferrous and non ferrous
material
•Incinerated is install ferrous separation
is required to reduce combustion
residue
•Eddy current ( for aluminum) where
electromagnetic induction takes place
•Electrostatic separation for glass ,
plastic and paper through
•separating bad conductor, poor
conductor and conductor of electricity
5.Drying and dewatering
•For wet solid waste and sludge
•Required for incineration the waste
convection , conduction driers

19. Material recovery facility (MRF)
Separation process
•Picking
•Screening
•Air classification
•Magnets
•Optical separation
•Eddy current (induced voltage produced current)
•Floatation (selective solid separated by using attach gas bubbles)

23. Various methods of resources recovery
1.Bio gas
a. From land fills
b. Anaerobic composting –biogas plants
Use bringing the heat to central heating
system for heating building
Steam to generate electricity
2.Compostingused as
Soil conditioner
Improved fertilizer quality
3. Incineration:(heat recovery)
4. Pyrolysis: (application of heat in anoxic
environment)
•Iron aluminum glass can be recovered
5. Recycling:
Saving of resources for economical
reasons
Environmental conservation
Employment (economy)

24. Recovery Process in Nepal
Organic waste recycling
1. Use for animal feeding
(directly, from hotels restaurant),
processed feed (bone meal for chicken)
2.Composting
• Bhaktapurcompost plant (not operated properly) (3 tons/day)
• At house hold level/ community level
• Anaerobic digestion –slaughter house waste
3.Use as energy source
• Directly burning the waste for energy (agro bi-products)
• Conversion to briquette (agro waste)
• Converted to biogas (animal waste)

25. 1. Paper recycling (there is more than 25000 tones per yrconsumption
only 20 % available for recycling)
2. Bone carving goods comb, buttons, decorative
3. Hair use for brush goods
4. Roofing , straw mats, and foot wear from straw etc

26. Paper recycling
•In developed countries paper waste is large fraction in composition
•Paper recycling process includes
-pulp preparation (paper fibers are separated in water and impurities are removed
by screening or centrifugal screening
-De-inking washing and floatation of the pulp in water and thickening
-helps to separates ink particles from paper pulp. Bleaching may be done to improve
the brightness of paper
-Paper making: the pulps are spread over the fabric belt ,dewatering through
gravity and vacuum suction
•Recycling process reduces water consumption by 60%, energy consumption by
40%, air pollution 74% and water pollution by 35 %
•Wastewater from recycle plant requires treatment
•Vrikutikagajudhyagand everestpaper mills using recycle paper in nepal
•Nepali kagajalso used as recycled paper

27. •Plastic recycling is popular in developing countries rather than developed countries
•90th decades statics USA 1.6%, EUROPE 23 % and India 80%
The recycling process includes
•cleaning, washing and drying in sun
•Sorting by manually or using optical technology
•Size reduction to transport
Several industries in Nepal especially in KTM of PE pipes, PE sheets, PVC, footwear
,PE and PP pipes
•The potential of recycling is increasing with increasing of its uses
•Imports of plastic granular ,
•But cheaper granular from segregates wastes
•Lack of industries of recycling

28. Type General Product Recycle product
HDPE pipes, shopping bags, milk
pouches
pipes, bottles, waste
containers
LDPE plastic bags, plastic sheetstrash bags, waste storage
containers
PVC pipes, foot wear, floor matscontainers
PETE mineral water bottles bottles, carpet, furniture,
fiber fill for slipping
bags and jackets
PP noodle packing brooms, flower pots
battery case
PS loose fill packing egg cartoons, building
insulation, loose fill
packing

29. Recycling ferrous metals
Some statics
✔10 to 30% of ferrous scarp are used with molten iron ore in primary steel
works
✔100% scarp metal can be used in production of ingots in secondary steel
works
✔100% scarp metal can be used in heated and rolled to produce required
items
✔De-tinning –recovery of steel and tin from used cans
✔Recycling ferrous metals saves 90% raw material , 70% energy , 40% water
use , 86 % air pollution , 76 % wwproduction

30. •Aluminum is the most successful metal recycled as it save money
•The old utensils are recycled in Nepal

31. Recycling glass
•Flat glass and container glass
•Following step are involved in Process of glass recycling
✔Sorting (by colour)
✔Crushing to culets
✔Cleaning
✔Melting in furnace
✔Forming
✔Annealing (controlled cooling of mouldedand blown glass)
✔Recycled to produce container glass , fiber glass etc

32. Again we thing R in SWM
•Reduction
•Reduction in generation
•Reduction in amount of material
•Increase the life time
•Eliminate the need
•Reuse
•No transformation
•Recycle
•Use of the material as a source raw material, involves physical transformation
•Recovery
•Process to Recover useful material from mixed waste

33. Materials that have potentiality for recycling which need recovered
Recyclable Material Types of material or uses
Glass Clear , green, and brown glass bottles and containers
Ferrous metal Tin cans, white goods, and other metals
Non ferrous metal Aluminum , cooper, lead etc.
Yard waste, collected separatelyUsed to prepare biomass fuel, intermediate landfill cover
Organic fraction of MSW Used to prepare compost for soil applications
Construction and demolitionwastes Soil, asphalt, concrete, wood, drywall shingles, metals
Wood Packing materials pallets, scarps and used wood from
construction projects
Waste oil Automobile, and truck oil (lubricant) reprocessed for
reuse or fuel
Tires Automobile, and truck Road building materials
Lead acid batteries Automobile, and truck , batteries, shredded to recover
individual components such as acid plastic and lead

34. Recyclable MaterialTypes of material or uses
Aluminum Soft drink, beer cans
Paper
Old news paper
Newsstand and home delivered newspaper
Bulk packaging; largest single source of waste paper for recycling
High grading paper
Mixed paper
Computer paper, white ledger,
Various mixture of clean paper including news print, magazine, white and color long
fiber paper
Plastic
PETE/1
HDPE/2
PVC/3
LDPE/4
PP/5
PS/6
Multilayer and others
Mixed plastic
Soft drink bottles, salad dressing, vegetable oil bottles, photographic film
Milk jugs, water container, detergent and cooking oil bottles (gallon)
Irrigation pipes, food packing and bottles
Thin film packaging and wraps, dry cleaning, film bags, other film material
Closures and labels, for bottles, and containers , battery casing, bread and cheese
wraps cereal box liners
Packing for electronic and electrical components, loam cups, fast food containers,
tableware and microwaves plates
Multilayer packaging , ketchup and mustard bottles,
Various combinations of the above products

35. What are Conversion Technologies?
Conversion technologies refer to a wide array of state-of-the-art
technologies capable of converting unrecyclable solid waste into useful
products, such as green fuels and renewable energy, in an
environmentally beneficial way. These technologies may be thermal,
chemical, biological, mechanical, or a combination of processes, but do
not include incineration (waste combustion).
• Energy recovery is the process by which solid waste is converted into
feedstock materials or renewable energy. Energy recovery is happening
right now, powering homes and businesses, and it’s helping to address
our growing population’s biggest challenges: energy independence,
waste diversion, and climate change.

36. Conversion technologies
Most conversion technologies can be described as having three
separate and distinct components: (1) front-end MSW preprocessing,
(2) the conversion unit, and (3) the energy/chemicals production
system. Front-end preprocessing is used to prepare the solid waste for
treatment by helping to separate and remove any recyclables.
• The level of preprocessing varies depending on technology.
Shredding, grinding, and/or drying the MSW may be required to create
a more homogeneous feedstock for some of the thermal technologies.
Alternatively, a water-based separation technique may be used in
biological processes. The energy production module can be a gas
turbine, boiler, or reciprocating engine for power production.

37. Utilizing conversion technologies
Utilizing conversion technologies to recover solid waste from disposal
can:
• reduce greenhouse gas emissions and other criteria pollutants;
• reduce dependence on land filling and imported fossil fuels;
• enhance recycling efforts

38. Conversion technologies
• Conversion technologies are an integral process in achieving a zero-
waste goal.
• These technologies not only create a beneficial product but also
potentially reduce greenhouse gas emissions and other air pollutants
This reduction is achieved through disposal and transportation
avoidance, as well as through fuel/electricity offsets.

39. Type of Conversion Tech
•Types of Waste Conversion Technologies Waste
•Conversion Process Steps
1. Mechanical pre-processing of the waste • Smaller particle size •
More uniformRemoval of contaminants • Lower moisture content (for
most thermal technologies)
2. Conversion process • Thermal or biological
3. Treatment of process outputs

40. Transformation
•Transformation means a process of reduction of waste by volume and
weight and recovering the energy from them.
•Typically waste transformations are used to improve the efficiency of
solid waste and management systems, to recover reusable and
recyclable materials, and to recover conversion products and energy
which include the following method they are -
1) Physical transformation
2) Chemical transformation
3) Biological transformation

41. Biological principle
1.Municipal refuse contains about 75% OM which can be converted
useful energy by combustion or other useful products
From conventional to sustainable SWM
• The basic objectives of it is to convert organic matter OM in to stable end
product.
• Why this is important?
-Return the organic matter to field ; reduce depletion of resources
-Arrest OM ; Reduce to pollute D/S of resource flow

42. Biological principle
1. General Nutritional requirement of microorganism
2. Type of microbial metabolism
3. Types of microorganism
4. Environmental requirements
5. Aerobic and anaerobic transformation
6. Process selection

43. Biological principle
Nutrient requirement of microbial growth
•To continue reproduce and function properly, an organism must have a
source of energy, and inorganic elements as nutrient
1. Source of energy
2. Nutrient and growth factors
carbon and energy sources usually called substrates, NPKS Ca Mg Fe Na Cl
are major nutrients Zn, Mn, molydebenumMo, selenium Se, cobalt, copper,
nickel etcare minor nutrients
•Growth factors are compound as constituent of organic
-cell material
-amino acid, purines, pyrimidines, vitamins

44. Classification of microorganism
Depending upon the use of energy sources and carbon the classification of microorganism
•Autotrophs carbon derived from CO2
•Heterotrophs carbon from organic
•Use light energy sources called Phototrophs
•Use energy from chemical reaction chemotrophs
Autotrophic
•Photo autotrophic light CO2
•Chemoautotrophic Inorganic oxidation reduction reaction CO2
Heterotrophic
•Photo heterotrophic light Organic carbon
•Chemo heterotrophic organic oxidation reduction reaction Organic carbon

45. Biological principle
2. Microbial nutrition and biological conversion processes
The main objective of BCP Conversion of OM in the waste into a stable
end product
•Chemoheterotrophic organism are primary importance. In SW
adequate amount of nutrients are available to support
•the biological conversion of the waste ( if needed addition is
necessary especially in industrial waste)

46. Types of microbial metabolism
Metabolism is the process (all the chemical process that occurs in a living
organism) as their metabolic type and their requirement of molecular oxygen
1.Obligate aerobic-aerobic respiration (accept molecular oxygen )
respiratory metabolism
2.Fermentative metabolism ; does not involve the participation of an
external electron acceptor (obligate anaerobic) absence of oxygen
3.Anoxic ; oxidisedinorganic compound function as electron acceptor for
some respiratory organism in the absence of molecular oxygen e.g. nitrate
and sulphate
4.Facultative anaerobic; can grow in either /or absence of molecular oxygen
1. True facultative (depends on oxygen)
2. Aero-tolerant anaerobic ( insensitive to the oxygen)

47. Types of microorganism
•Microorganism are commonly classified on the basis of cell structure as;
-Eucaryotes
-Eubacteria
-Archaebacteria
•Eubacteria & Archaebacteriaare primary importance in biological conversion of the organic
fraction of SW and generally referred as bacteria
•The Eucaryoticgroup includes plants and animal and protists, the important microorganism of this
types are ‘;
1. Fungi Yeasts(a microscopic fungus consisting of single oval cells that reproduce by budding, and
capable of converting sugar into alcohol and carbon dioxide.)
2. Actinomycetes
•Bacterial single cell
•Fungi multicellular
•Yeasts unicellular Actinomycetesintermediate properties between above two bacteria and fungi

48. Environmental requirement
•For biological conversion a favorable environment is necessary;
Temperature and pH are important environmental parameter for survival
and growth of microorganism
•The growth of microorganism is optimum in narrow range
•The survival is possible in boarder range
•If temperature increase 10 degc growth will be double until the optimum
temperature
•As temperature, the microorganism are
Psychrophilic 10 to 30 degc (15 degc)
Mosophilic20 to 50 degc (35 degc)
Thermophelic 45 to 75 deg c (55 deg c)

49. Environmental requirement
•pH range 6.5 to 7.5
•For optimum growth of bacteria moisture is necessary 50 to 60 %
•free from any types of heavy metal concentration, ammonia, sulfides
and other toxic constituent

50. Anaerobic biological transformation
pathway of OM of SWM to the production

51. Biological process selection
•Aerobic -simple
•Anaerobic -energy benefit
•Comparison of aerobic and anaerobic digestion process of MSW
Characteristics Aerobic process Anaerobic process
Energy use Net energy consumer Net energy production
End products Humus, co2, H2O Sludge CO2, CH4
Volume reduction Up to 50% Up to 50 %
Processing time 20 to 30 days 20 to 40 days
Primary goal Volume reduction Energy production
Secondary goal Compost production Volume reduction,
waste stabilization

52. CHEMICAL PROCESS FOR THE RECOVERY OF
CONVERSION PRODUCTS
• Chemical transformation process includes a number of hydrolysis
process
For recover of glucose,and other compounds such as synthetic oil, gas,
cellulose, acetate,Methanol alternative liquid fuel, Acid hydrolysis
•Methanol production from methane

53. CHEMICAL PROCESS FOR THE RECOVERY OF
CONVERSIONPRODUCTS
•The methane produce by the anaerobic digestion Converted to
methanol and a liquid fuel
•( cH4 +H2O>>>CO+ 3H2) endothermic reaction (heat absorb) biogas ,
methane (acid hydrolysis)
•Produce carbon monoxide and hydrogen gas
•CO+2H2>>>>>>CH3OH exothermic reaction (heat release) to form
methanol from fist reaction product

54. CHEMICAL PROCESS FOR THE RECOVERY OF
CONVERSION
PRODUCTS
Process Conversion product preprocessing
Acid hydrolysis Organic acids Separation of organic
fraction, particle size
reduction
Alkaline
hydrolysis
Organic acids Separation of organic
fraction, particle size
reduction
Various
chemical
conversion
process
Oil gas cellulose
acetate
Separation of organic
fraction, particle size
reduction

55. Composting (Aerobic)
Commonly used biological process
•Applied for yard waste, separated MSW, commingled MSW co-composting with waste
water sludge
•“Composting is the biological decomposition of biodegradable solid waste under
controlled predominantly aerobic conditions to a state that is sufficiently stable for
nuisance-free storage and handling and is satisfactorily matured for safe use in
agriculture”. ( General definition)
•“Composting is a decomposition process in which the substrate is progressively broken
down by a succession of populations of living organisms. The breakdown products of one
population serve as the substrate for the succeeding population. The succession is
initiated by way of the breakdown of the complex molecules in the raw substrate to
simpler forms by microbes indigenous to the substrate”(ecological definition). The process
steps includes
•Preprocessing of MSW
•Aerobic decomposition
•Product preparation marketing
•Windrow , aerated pile, in vessel are three principal method are used for the composting

56. Composting
•The composting technologies –windrow, aerated static pile, in-vessel
composting and anaerobic processing (EPA, 1989 and 1995) –vary in
the method of air supply, temperature control, mixing/turning of the
material, time required for composting, and capital and operating
costs. Besides these general categories of composting technologies,
there are also some supporting technologies, which include sorting,
screening, and curing.

57. Composting
Quality of compost
depends on
•Composition of input
material
•Condition available for
composting
•Extent of
decomposition
Factors in composting:
Particle size and particle size
distribution
25 to 75mm
Seeding and mixing requirements1:5 partial decompose SW
Mixing and turning of compost
Total oxygen requirement
Moisture content
Temperature and temperature control
To prevent caking, drying, channeling
50 % initial oxygen
50 to 60 %
50 to 55 degc
Carbon/ nitrogen ratio 25 to 50 by mass
pH 7 to 7.5
Area (land) requirement 50 ton/d 1.5 to 2 acre

58. Four main components:
•organic matter,
•moisture,
•oxygen, and
•bacteria.

59. Biochemical reaction in composting
•Latent phase : time required to acclimatize the microorganism and
colonize in the new environment
•Mesophilic phase : rise the temperature due to biological
process. Mesophilic bacteria start working on the waste rising the
temperature up to 45 degc
•During this growth phase microorganism starts to increasepopulation
(multiplying)

60. Biological Succession

61. Composting (Aerobic)
•Nutrient balance
•C/N ratio is most important
•P important
•S, Ca trace element Less important
•C/N ratio 20 to 40 (for better result 25 to 30)

62. Composting (Aerobic)
material Nitrogen
(% dry weight)
C/N ratio
Night soil 5.5-6.5 6-10
Urine 15-18 0.8
Blood 10-14 3
Animal tank age - 4.1
Cow manure 1.7 18
Poultry manure 6.3 15
Sheep manure 3.6 22
Pig manure 3.8 -
Horse manure 2.3 25
Raw sewage sludge 3.8 11
Digested sludge 2.3 -
Activated sludge 5 6
•C/ N ratio of waste composition

63. Composting (Aerobic)
material Nitrogen (% dry weight) C/N ratio
Non legume vegetable waste 2.5-4 11-12
Mixed grasses 2.4 19
Potato tops 1.5 25
Wheat straw 0.3-0.5 128-150
Oats straw 1.1 48
Saw dust 0.1 200-500
News paper 50-200
Vegetable trimming 12-20
Food scraps 18
Fruit peeling 1.52 34.8
Corn stalks 60
Dry leaves 30-80
Tree bark
100-130
•C/ N ratio of waste composition

64. Composting (Aerobic)
Method of composting
•Windrow composting
•Static pile
•In vessel composting
-Plug flow
-Continuous
•Community and home composting
-Bin composting
Temperature and pH ranges in composting

65. Windrow composting
•Oldest method: First time in India studied by America (Howard and associates ) in 1930
•2 to 3 feet deep trench and successive layer placed of biodegradable waste
•Rows of compost heap is created on a rigid surface in ventilated area
•8 to 10 feet htand 20 to 25 ‘ width
•For high rate windrow composting 6’ to 7’ htand 14 to 16 feet width
•Preferable cover for rain water and odour
•Processed by , shredding, screening, moisture content,
•Turn twice a week
•Maintain temperature slightly above 55 degc
•Three to four week for composting and another three or four week for curing without turning
•Offensive odor during turning
•Suitable in temperate (tropical and semi tropical area)

68. Aerated static pile composting
•Developed in US Department of Agriculture research services at Beltsville ,
Maryland
•Sometime called Beltsville method or ARS process
•Ht7 to 8 feet
•A layer of compost is often placed in top
•Each pile is usually provided air blower, disposable corrugated plastic, drainage
pipe is used for air supply
•Intermittent air supply
•Time required three to four week for composting and next four week for
maturation (cured)
•Cover for prevent odour
•Dewatering required bulking agent to maintain porosity usually by wooden chips

69. Aerated static pile composting
•A layer of mulching is provided surrounding the heap(stack) to stop
blowing waste
•Maintaining temperature
•Drainage layer at bottom of heap

71. In vessel composting
•Composted in side or enclosed container or vessel
•shape circular or rectangular, horizontal or vertical
•Circular rotating
•Plug flow reactor (first in first out)
•Dynamic (mechanically mixed ) minimized odour, easy to maintain
the environment, temp, air,
•Time required 1 to 2 weeks but virtually 4 to 12 week

72. Community and home composting
•Make as simple as possible
•Less effort
•Low investment
•Aesthetic
•Types
-Bin / barrel (drum)
-Rotating drum
-Pit composting

73. Bin composting
•Continuous feeding
•100 liters is sufficient for family of 5-7
•Holes are provided for aeration the waste
•For inoculation, dairy products are not fed
•To meet C/N ratio rice husk, ash, or saw dust may need to be added
•Moisture content need to be maintain
•to prevent insect attraction meat and dairy product are not fed

74. Issues in the implementation of composting facilities
1. Production of odour
2. Presence of pathogens( public health issues)
3. Presence of heavy metal
4. Desired material for quality compost
Major cause of odour
1.Low C/N ratio
2.Environment
-Poor temperature control
-Excessive moisture
-Poor mixing of waste

75. Thermal processing
•Thermal processing of solid waste can be defined as the conversion of
wastes into gaseous, liquid and solid production, with or without
energy valorization (Tchobanoglouset al., 1993).
•THERMAL PROCESS

76. Incineration
•Incineration is a chemical reaction in which carbon, hydrogen and other
elements in the waste mix with oxygen in the combustion zone and
generates heat.
•The air requirements for combustion of solid wastes are considerable. For
example, approximately 5000 kg of air is required for each tonneof solid
wastes burned.
•Usually, excess air is supplied to the incinerator to ensure complete mixing
and combustion and to regulate operating temperature and control
emissions. Excess air requirements, however, differ with moisture content
of waste, heating values and the type of combustion technology employed.
•The principal gas products of combustion are carbondioxide, carbon
monoxide,water, oxygen and oxides of nitrogen.

77. Reason for incineration
•Reduces the volume 85 % to 95 %
•Chemical transformation of organic fraction of MSW
•Recovery of energy in the form of heat

78. Incineration
•The terms incinerator are synonymous with “combustor” or
“combustion systems”.
•the incinerators of today have a much higher degree of process
control
•Major components of MSW are CHONS
•The end products of combustion are CO2, H2O, N2 and small amount
of SO2 and ash
•Depending upon the composition of MSW several other end product
are also produced

79. •Combustions with exactly the amount of oxygen needed for complete
combustion is known as stoichiometric combustion
•Excess air combustions
•Gasification is the partial combustion under sub-stoichiometric
condition

80. Major elements that constitute solid wastes and
the end products of combustion

81. Recovery of thermal conversion products
• Conversion of solid wastes into (Releases of heat energy)
–Gaseous liquid, solid conversion products
System can be categorized as their air requirement
–stoichiometric combustion (amount of oxygen needed exactly)
• Mass fired
• RDF fired
• Fluidized bed
• Gasification (partial combustion sub stoichiometric )
–Combustible gas Containing CO, H2, gaseous hydrocarbon
• Pyrolysis (thermal process in completely absence of oxygen)

82. Types of combustion
Mass fired combustions
•Un-separated commingled waste is used
•Mixed waste is burned without prior sorting and separating
•External energy like diesel may be required to fire the waste
•Where heat content is very low additional energy may be required for
combustion
•Heat recovery is considered in most of the system
•Moisture content of MSW is important as it diminishes gross calorific value
of the waste

83. Types of combustion
RDF fired combustion
•RDF is produced from non-hazardous waste materials, typically consisting of
combustible components like plastics, paper, textiles, and wood
•RDF is produced by shredding and sorting non-combustible materials from MSW and
processing the remaining combustible materials into a uniform fuel.
•MSW prepared for combustions in the form like
-Shredded
-pellet
-Cubes
The advantages are
•Fair consistency in energy content
•High efficiency in combustion
•Comparatively smaller size of incinerator is required
The main limitation is pre sorting and processing cost

84. Fluidized bed
Fluidized bed combustion (FBC) is a
combustion technology used to burn
solid fuels for combustion.
•Fluidized bed combustion (FBC) is a
method of burning solid fuels in a bed
of inert particles suspended and
fluidized by a flow of gas (usually air)
through the bed.
•This process offers several advantages
over traditional combustion methods,
such as enhanced fuel flexibility,
improved combustion efficiency, and
reduced emissions of pollutants.

85. The working of an incinerator
Five major components
1. Waste delivery and feeding system
2. The furnace and combustion chamber
3. Grating and air supply system
4. Heat recovery system
5. Pollution control system

86. Waste delivery and feeding system
•Waste delivery bunker (at least 4 days waste storing capacity)
•A weighing bridge is provided to keep the record of waste input
•A crane system is provided to mix the waste and load into the furnace
through chute (charging)
•Slight negative pressure is created in the feeding area to keep the
odourwithin the delivery bunker

87. Furnace and combustion chamber
•Incinerator may have one or more furnaces to burn the waste
properly
•The flexibility is sought to increase efficiency, reduce heat loss during
and initial firing and continue the job even at the time of maintenance
•When MSW is charged into the furnace through charging chute the
waste will be heated up by hot combustion air and radiated heat from
the incinerator wall

88. Furnace and combustion chamber
•The moisture is driven of the heat of 50 –100 degC
•The waste then undergoes thermal decomposition of organic fraction
generating volatile matter , combustible gases and vapour
•It is then ignited and gives flame
•The volatile materials comprised of 70 to 90 % may be found in the
form of H2 CO2 CH4 , and other higher molecular weight hydrocarbons

89. Furnace and combustion chamber
•De-volatilization (volatile substances are removed or driven off from a
material) takes wide place in wide range of temp 200-750 degC
•Most of the compounds will be disintegrated within 425 –550 degc
•Temperature for complete burning needs 750 –1000 degc
•The temperature should not go beyond 1200 degC to avoid
accumulation of ash fusion leading to slag formation
•Furnace wall is lined with silicon carbide to keep the heat within limit

90. Furnace and combustion chamber
•Typical mean residence time of these gases in the chamber is 2-4 s
•After de-volitizationstage the residue consist of carbonaceous char
and the inert material . It takes 30 –60 minutes for complete burning
of these residues
•The bottom ash is quenched in water trough which may be land filled
or used in road construction

91. Grating and air supply
The two main purpose of grating
•To spread the waste
•To supply adequate air from beneath
•Air draft is supplied from below to burn the waste properly
•Ashes are discharged at the end in to a water quench trough at the bottom
•Theoretically determination of air required may be calculated using stiochimetricequation
•Approximately 1.25 to 2.25 times theoretically quantity of air is required
•Excess air supply helps to burn the waste but excess air increases volume of flue gas and reduce
temperature affecting the efficiency
•Secondary air is injected from above to minimize formation of pollutants like high molecular weight
hydrocarbons

92. Heat recovery
•The flue gas cleaning system may not tolerate the temperature of 250
degree c –300 degree c. Therefore flue gas must be cooled
•Boilers are provided with steel tubes through which water flows to
generate stream
•After waste is combusted in the incineration chamber, the heat
generated can be utilized to produce steam in the boiler.
•This steam can then be used to drive turbines, generating electricity or
to provide heat for various industrial processes.
•The boiler essentially acts as a heat exchanger, transferring the thermal
energy from the combustion process to the water to produce steam.

93. Heat recovery
•The temperature around boiler should not drop less than 200 degC as the HCl
and H2 SO4 gases in the flue gas may corrode boiler tubes
•Two method of heat recovery: water wall combustion chamber or waste heat
boiler or the both
•Efficiency in heat recovery system is limited by two factor
-Deposition of flue gas particulates on the tube surface
-Corrosion of tube surface
•Deposition of fly ash , soot volatilized, metal compounds , etc
•The adherence is determined by the presence of molten salts such as Ca, Mg,
Na sulphates, oxides, bisulphates, chlorides etc

94. Pollution Control
•Emission control-guided by environmental legislation standards
•Total particulate matter, dust, acidic gases-HCl, HF, SO2, heavy
metals-Hg, Cd, Pb, CO, Organic Carbon

95. Environmental control system
Several impact on environment
•Gaseous and particulate emission
•Solid residues
•Liquid effluent
Some time the cost of recovery is far below than cost of environmental
control system

96. THANK YOU!