es_200_3_assignment-1.pdf

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Environmental Studies:Science and Engineering

By

Dr. Anurag Garg28 July 2011



2

Energy Savings Of Recycling

5 – 8 timesTextiles

3 – 5 timesPlastics

350 times Aluminum cans

30 timesTin cans

30 timesGlass containers

4.3 timesOffice paper

2.6 timesNewspaper

Relative energy needed to

manufacture versus energy

generated from EfW incineration

Material



3

Relative Composition of Household Waste in

Low, Medium and High-income Countries

1500 - 27001000 - 1300800 - 1100Calorific value, kcal/kg

100 - 170170 - 330250 - 500Specific weight , kg/m3

5 - 2040 - 6040 - 80Moisture content, %Physical and

chemical

properties

2 - 1015 - 5015 - 60Other, %

2 - 101 - 51 - 5Rubber, leather, %

4 - 101 - 101 - 10Glass, %

3 - 131 - 51 - 5Metal, %

2 - 102 - 61 - 5Plastics, %

15 - 4015 - 301 - 10Paper, %

20 - 3020 - 6540 - 85Organic (putrecible), %

High-

income

countries

Medium-

income

Low-

income

countries

Parameter

Contents



4

Comparison of MSW in 7 OECD and Asian Countries

http://maps.grida.no/go/graphic/municipal_solid_waste_composition_for_7_oecd_countries_and_7_asian_cities



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7

Waste

processing

methods

Biological

processes

Composting

Anaerobic

digestion

Compost

Biogas and

digestate

Gasification/

Pyrolysis

Thermalprocesses

IncinerationHeat, gaseous

emissions and

ash

Producer gas, solid

fuel and tar

Major outputs

Major treatment processes for MSW and end products



8

Biological Processes

• Composting9Composting is a process in which the organic

fraction of MSW is decomposed by microbes

under controlled aerobic condit ions.

9 As a result, a stabilized product (also calledcompost) is produced that can be used as soilcover at landfil ls or conditioner.

9Using composting process, the volume of the

compost can be reduced by around 50%.

9Composting process can be done in two ways:Windrow and in-vessel.



9

Windrow Composting Compost



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Biological Processes…..

• Composting…..9Sometimes, sewage sludge or agricultural

residues are also added with MSW. This is called‘co-composting’.

9Composting can also have negative impacts:

Water pollution may exist if moisture content is

very high (> 65%)

Odor is another major problem from

composting sites using open windrow method.



11

Home Composting

Which wastes? Non-woody yard

wastes are the most appropriate.

Holding Units Turning Units

Which wastes? Non-woody yard wastes areappropriate. Kitchen wastes without meat,bones or fatty foods can be added to thecenter of a pile if it is turned weekly andreaches high temperatures.



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Vermicomposting• Vermicomposting is a method of preparing compost

with the help of earthworm.

• Vermicomposting is a simple biotechnological

process of composting, in which certain species of

earthworms are used to enhance the process of wasteconversion and produce a better end product.

• The process is faster in comparison to conventional

composting.



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Biological Processes…..• Anaerobic digestion (Biomethanation)9 If the organic waste is buried in pits under

anaerobic conditions, it will be decomposed byanaerobic bacteria.

9Thermophilic digestion is much faster and leadsto the energy recovery through biogas generation.

9Biogas contains 55 – 60% CH4 and 35 – 40% CO2.

9There is a litt le experience in treatment of solidorganic waste in India.



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Thermal Treatment Processes

• Incineration9 It is a thermal process in which combustible

portion of MSW is oxidized at high temperaturesof around 1000°C.

9 Incineration can reduce municipal refuse by about80 - 90% volume.

9The major residue formed after the processinclude (bottom and fly ash) that may containheavy metals.

9 In addition, gaseous emissions like CO2, NOx,dioxins etc. are also of major concern.



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Desirable Range of Important Waste Parameters

for Technical Viability of Energy Recovery

25-30C/N ratio

> 40%Organic volatile

matter

> 50%Moisture contentDecomposition of organic matter by

microbial action

Biochemicalconversion

Anaerobic

digestion/ Bio-

methanisation

> 1200 kcal/kgCalorific value

< 35%Total Inerts

< 15%Fixed carbon

> 40%Organic/volatile

mater

< 45%Moisture contentDecomposition of

organic matter by

action of heat

Thermo-chemical

conversion

o Incineration

o Pyrolysis

o Gasification

Desirable

range

Important

waste

parameters

Basic principleWaste

treatment

method



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Pre-treatment Methods

• Shredding– Used for size reduction of waste components

– Shredding refers to the actions of cutting and tearing

– Hammer mills is the most common type of equipment usedfor processing MSW into a uniform or homogeneous mass.

• Baling

– Compacting solid waste into the form of rectangular blocks or bales is called baling.

– MSW bales are typically 1.5 m3 in size and weigh roughly 1kN.

– Bales are produced by compacting the solid waste under highpressures (~ 0.7 MPa)

– Solid waste compaction ratio can be expressed in terms of compaction ratio.

Compaction ratio = initial volume/ final volume



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Landfilling

• This is the oldest and most widely used

method for waste disposal.

• Land disposal may be done in two

ways:9Open dumping

9Sanitary landfilling



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Landfilling……

• Sanitary landfilling has three key

characteristics:

9Waste is placed in an organized manner.¾Waste material is spread and compacted.

¾The waste is covered each day with a layer of compacted

soil.

9Provisions for capturing the landfill gas (CH4 and

CO2 – two major constituents) are made.

9Proper leachate (wastewater generated from a

landfil l site) collection system is also present.



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20

Estimation of Landfill Area

• Estimate how many hectares of land would be required for asanitary landfi ll, under thefollowing conditions:9 Design life of the site = 30

years

9 MSW generation rate = 25N/person/day

9 MSW compacted unit weight =5 kN/m3

9 Average fill depth = 10 m

9 Community population = 50,000

9 MSW to cover ratio = 4:1 (20%

of volume for cover)

• Solution

The quantity of MSW generatedper year = 25 x 50000 x 365 =

4.56 x 105 kN/yr The volume of compacted refuse

= 4.56 x 105/ 5 = 91250 m3/yr

The addit ional volume for soilcover = 91250/4 = 22813 m3/yr

Total required volume = 91250 +22813 = 114063 m3/yr

The area required = volume/depth

= 114063/10

= 11406 m2

/yr Total landfi ll area required

= 11406 x (30 yrs)/ 104 ha

= 34 ha



21

MSW Composition (present-transit-future

phase) in Asian Developing Countries



22

MSW Disposal Methods (present-transit-future

phase) in Asian Developing Countries



23

Mechanical Biological Treatment

• Generic term for an integration of severalprocesses

• Objective:

9Part stabilize the waste prior to landfill ing;

9Biologically process a segregated 'organic rich'component of the waste and

9Produce a segregated high calorific value wasteto feed an appropriate thermal process to uti lizeits energy potential.



24

Track Record

• Originated in Germany

• The largest European markets for establishedMBT plant are in Germany, Austria, Italy,

Switzerland and the Netherlands.

• There are over 70 MBT facilities in operation in

Europe, with over 40 MBT facilities operating

in Germany.



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Advantages of MBT

• MBT reduces the volume of waste

• It reduces the cost of managing the landfil l

• It reduces the production of methane and thereby

the impact on climate change.

• Solid recovered fuel produced has a higher calorificvalue than untreated residual waste.

• Good quality metals can be recovered for recycling.



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MSW

Manual, Partial

Mechanical

Segregation

High moisturized

biodegradable

fraction

Anaerobicdigestion

Composting

Recyclables

Inert/other

remains

RDF

Energy

recovery

Landfill

Compost

agriculture and/

landfill cover soil

Scavengers/waste

pickers

General approach to the Mechanical- Biological Treatment in Asia

(Source: Visvanathan et al., 2005)



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Waste Management Practice

(as % of total MSW) (Giust i, 2009)



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Main Environmental Impact of MSW Management

(Giusti, 2009)

Significant

contribution

of CO2

SpillsCO2, SO2, NOx, dust,

odour, noise, spills

SpillsWaste

transportation

Small GHG

emissions

Vermin,

insects

Bacteria, viruses,

Heavy metals,

PAHs, PCBs

Bioaerosols, dust,

odour

Bacteria,

viruses, HM

Land

spreading

Small GHG

emissions

Some

visual

effect

Minor impactCO2, CH4, VOCs,

dust, odour,

bioaerosols

LeachateComposting

GHG

emissions

Visual

effect

Fly ash, slagSO2, NOx, N2O, HCl,

HF, CO, CO2,

dioxins, furans,

PAHs, VOCs,

odour, noise

Fall-out of

atmospheric

pollutants

Incineration

Worst option

for GHG

emissions

Visual

effect;

vermin

HM, organicsCO2, CH4, odour,

noise, VOCs

Leachate

(HM,

organics)

Landfilling

ClimateLandscapeSoil Air Water Activ ity



29

Assignment – 1

Please read the instructions carefully:

• There are TWO problems in Assignment 1 (Max. marks = 7). The

weightage of first problem is 4 marks and the second one is 3

marks.

• The assignment has to be submitted by Monday (1st August) in

the class.

• If one fails to submit by Monday, then the other submission date

is Thursday (4th August). The student will be awarded 70% of the

total marks that he/ she secures out of 7 (max. marks).

• On submitt ing after 4

th

August till the last class of the currentsemester, one will get a maximum of 40% marks of the total

marks that he/ she secures out of 7 (max. marks). After last date

of instruction (8th September), no assignment will be accepted.



30

Problem – 1

• A town with a population of 1,00,000 generates the solid wasteat a rate of 0.55 kg/person/day. Suppose the mixed solid wastecontains 20% (by weight) paper. After segregation, 80% of thetotal paper present in mixed stream is recovered and can be

supplied to a nearby cement manufacturing plant for using asco-fuel with coal (calorific value of coal = 20 MJ/kg). Themanufacturing plant produces 0.5 million tonnes of cement per annum (1 tonne = 1000 kg). The calorif ic value of the wastepaper is 15 MJ/kg. The total input energy requirement for 1 kg of

cement production is 4.5 MJ. At the most, the cement producer can fulfi ll 10% of the total input energy requirements from thesegregated waste paper. Using the above data, calculate:

¾ How much paper waste is produced annually. Is this quantitysufficient to provide 10% of the total input energy in cement

production? If not, how much energy can be supplied by segregatedwaste paper (express as percentage of total input energy).

¾ Also calculate how much coal savings can be achieved annually byusing waste paper as co-fuel.



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Problem – 2

• Estimate the land area

required annually to dispose

a city waste (total wastegeneration = 7000 tonnes/

day) having the

characteristics shown in

Table. The compacteddensity of waste is 5 times of

that ‘as received’ waste.

Assume average fill depth =10 m and MSW to soil cover

ratio = 4:1 905Tin cans

2405Wood

10510Garden

trimmings

6510Plastics

5010Cardboard

8545Paper

29015Food waste

Typical

uncompacted

density

(kg/m3)

% by

mass

Component

es_200_3_assignment-1.pdf

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