Solid wastes problems and benefits

Solid Wastes
Problems and Benefits
Watheq Naser Hussein
ISBN 9789922206356
First Edition 2020

II
Preface
Waste has a broad meaning with a common intent
regarding losses. What is meant by losses in this book is
not that thing which is hidden in a place, rather it has two
meanings, either to throw things that we don’t need while
they have some remaining life or when we use them either
totally or partially such as food, papers, and plastics….etc.
The waste arising as soon as the man was created, it is
growing with the growing of human community, the
complication of life and the diversity of living ways.
Due to the related problems of the waste accompanying
human life directly and on all the lives of the other
creatures, the needs are arising to manage the waste
problems. It is not merely treatments of wastes made man
stopped at this margin but he stepped further through
creating money or getting some of his purposes by some
treatments or Recycling to some types of wastes. In some
poor countries or those who lack the natural energy
sources or oils as well as for the rich countries recycling
and waste treatments to produce an energy sources are in
continuous development.
There are many books in the field of waste handling and
this book was edited based on the needs of our students of
energy department as well as it is planned to make it
compacted with useful information to the reader in an
acceptable manner, but, It could contain some prolonged
sections for necessity purposes. This book is composed of

III
nine chapters with some illustrative examples according to
the type of chapters and some questions at the end of
chapters.
In chapter one and two the waste definitions and its
composition were elucidated. Chapter three a very
important field of waste aspects using which is the
transformation to energy was handled with some illustrative
examples. Chapters four and five illustrated landfills and
some related aspects. Chapter six clarified the problem of
environment related to the hazardous waste. Chapter
seven clarified pyrolysis and gasification processes where
this field occupies an increasing attention. Chapter eight
tackled the chemical and bio processes based on waste as
a feed and this field represents a very important and
growing sectors in industry. Chapter nine demonstrated
planning and economic considerations of waste handlings,
It can be said why this chapter located at the end of this
book? This is to outline the problem first and look for the
ways to treat it. Some of the waste fields handling have not
been treated and could be included in the next editions if I
get extended days for life.
Any work according to my view is not perfect, so I don’t
allege that everything was done perfectly and to correct
any misunderstanding, I do appreciate any advice or
feedback from the reader to improve the coming edition.
Watheq Naser Hussein
wathq777@yahoo.com
met.watheq.naser@uobabylon.edu.iq

IV
May-2020
Dedication
To the Souls of My Parents...
To My Family
With Regards

I
Contents
Chapter One Introduction to Waste ……………..
1.1 What does waste mean? ………………………..
1.2 Management of solid wastes Documentation..
1.3 Documentation ……………………………………
1.4 Objective……………………………………………
Chapter Two Waste Materials Diagnosis ……….
2.1 Important properties of wastes ………..……...
2.2 Recovery prospects wastes .…….…………….
Chapter Three Waste as an Energy.…..……..…
3.1 Types of incinerators .……………………………
3.2 Combustion principles…………………………..
3.3 Boiler………………………………………………..
Chapter Four Landfills………………………………..
4.1 Introduction……………………….………………..
4.2 Types and components of landfill……………...
4.3 Classifications of landfill sites.........................
4.4 Factors affecting degradation inside landfills
4.5 Landfill components……………………………...
4.6 Landfill engineering ……………………………..
4.7 Landfill liners ……….……………………………
4.8 Compaction of wastes……………….…………..
4.9 Leachate management …………………………..
4.10 Advantages of bioreactor landfill .........…….
Chapter Five Landfill Gas Characteristics……….
5.1 Land fill Gas characteristics and composition…..
5.2 Composition of LFG ……………………………..
5.3 Anaerobic technology for producing syngas..
5.4 LFG as a renewable energy …………………….
5.5 Upgrading of biogas to natural gas …………..
5.6 Monitoring of landfill gas ……………………….
Chapter Six Environmental Pollution and
Hazards of MSW ………………………………………
1
1
3
5
6
9
12
16
34
40
51
62
73
73
80
82
82
86
88
89
91
92
93
97
98
100
109
113
114
115
121

II
6.1 Monitoring of landfill hazards……………..……
6.2 Monitoring of ground water ..………………….
6.3 LFG health effect .………………………………..
6.4 Emissions from other processes………………
6.5 Effect of Greenhouse Gas ………………………
6.6 Hospital/Biomedical wastes ……..…………..
6.7 Segregation, Packing, Transportation and
Storage................................................................
Chapter Seven Pyrolysis and Gasification .………
7.1 Pyrolysis .………………………………………….
7.2 Advantages of pyrolysis .....…………………..
7.3 Gasification ………………………………………..
7.4 Updraft gasification ……………………………..
7.5 Fluidized bed gasification .…………………….
7.6 Entrained flow gasification ……………………
7.7 Rotary kiln gasification ..……………………….
Chapter Eight Chemical and Bioprocesses ..……
8.1 Fossils and biomass ...…………………………..
8.2 Technological processes..……………………...
8.3 Biogas ………………………………………………
8.4 Syngas ..……………………………..……………..
8.5 Biorefinery products ..……………………………
Chapter Nine Economics and Planning of Waste
Treatments ……………….…………………………..
9.1 Introduction..………………………………..……..
9.2 Biogas concern..……..…………………………..
Index …………….……………………………………….
121
123
126
132
134
142
143
164
168
169
170
177
178
179
179
183
185
191
193
194
194
199
199
214
223

1
Chapter One Introduction to Waste
1.1 What does waste mean?
All the wastes arising from human and animal activities are
discarded as useless or unwanted which could be solid in
its shape or liquids. Plants in general, also give a waste
during its life cycle. Disposing of wastes is a natural
phenomenon occurring in the life, therefore, it is related
directly to the growing of human beings and the manner of
development. Due to development of agriculture, industry
and the wide steps or jumping in the heave of science and
its complications, the waste quantity is in steep and
continuous growing. As the waste dumped in an area, the
feasibility of risks appears. The lack of any plan for the
management of solid wastes thus led to the epidemic of
plague, the Black Death that killed half of the fourteenth
century Europeans and caused many subsequent
epidemics with high death tolls1
. It was not until the
nineteenth century that public health officials, who began to
realize that food wastes, had to be collected and disposed
of in a sanitary manner to control rodents and flies, the
vectors of disease. The relation between wastes
collections, dealing with it and the public health have an

2
intimate relation. For examples rats, flies and insects or
mosquito are finding a good shelter or living and production
in the dumps of wastes especially those types of open one.
Improper dumping or landfilling of wastes or garbage
especially when they lie near rivers or lakes may lead to
contamination of water with some materials or elements
that could be considered poisonous such arsenic, uranium,
copper……etc. Additionally, some elements such as Ca
and Mg ions could be leaked to the water source. Some of
odors or smells may also spread to the air to some
unaccepted limits. The nature and the policy of treating
wastes depend on many factors, such as the prosperity of
the community, the ability of the country, the location of
these wastes whether they are inside cities or outside. etc.
Landfills became popular in the 1920s as a means of
reclaiming swampland while disposing of trash, then in
1965, the Federal government of the United States enacted
the first Federal solid waste (SW) management laws. In
1976, the Resource Conservation and Recovery Act
(RCRA) was created for stressing recycling and hazardous
waste management, which likely was instigated by the
discovery of Love Canal2
. This proves that since the
creation of mankind, humans have generated waste. But

3
waste disposal was not a problem when we had a nomadic
existence; mankind simply moved away and left their waste
behind.
1.2 Management of solid wastes
In general there are four principal methods in dealing with
Municipal Solid Wastes MSW; the first one is recovery or
recycling of plastics, paper, metals, glass, rubber or
anything that can be reused to produced similar products,
the second is the recovery of energy by using wastes of
hydrocarbon or any material other than glass, metals,
ceramics….etc., as a combustible material, the third is
using the biodegradable materials such as some foods,
papers or some type of polymers under anaerobic or
aerobic conditions to produce some chemicals with a
power of producing energy and the fourth is the landfilling
process which includes any materials that does not lie in
the above categories. Engineering landfills with a standard
design conditions are used as a tomb for landfilling in order
to prevent leakage of any waste to the rivers or waters. As
a pre final step of disposal, a volume reduction of wastes
should be done including packing or screening in order to

4
reduce the volume and the space of the landfill or disposal
site.
The culture of the community plays a vital role in reduction
of wastes3
, reuse and recycling. The reduction of wastes
can be obtained by the optimization of using products, for
example the same bag can be used more than one period,
the same shoes can be wear more than one year as long
as it still keep its durability. In Iraq for example one of the
major waste components is the plastic and one of them is
disposable plastic bag which is used widely in daily
shopping, this bag could be substituted by a durable and
long lasting bag that reduces the huge quantity of plastic
bags. Another thing, is by reducing the exaggerated
procedures in packing some goods or electronics.
Awareness of the person by the government and giving
him the role of reducing the wastes quantity will contribute
to do the goal. Municipal solid wastes consist of various
materials4-6
e.g. paper, cardboard, plastics. metals, glass
and rubber. Many of these components are suitable for
recycling and reuse. The process involves separation and
collection of these materials, preparation of materials for
reuse and remanufacture7-8
. By selling such recovered

5
wastes much money can be earned, reduction in the loads
of disposal and handling. Parallel to recycling, combustion
of the combustible wastes will give good values of energy,
saving money for buying fuels and also will lead to a
reduction in load and handling of wastes.
1.3 Documentation
The first step is collection of wastes from houses or any
other place showing industrial or military activity that
produce wastes. Documentation need to answer: What is
the daily quantity of waste in a specified place? What type
of waste are there and do they vary with the seasons? How
many trucks, vehicles are carrying this quantity …etc.?
How many liters of fuels are needed for that task? How
many workers are needed? The second step is to compost
theses waste, this can be done according to the strategy of
the country and the extent of using wastes in economics.
The composting is based on means of exploiting those
wastes such as combustible and noncombustible or
recyclable material and none. Another question is how
long the wastes need to be sent either to the landfill, to the
recycling factory or to the combustor and what is the
adverse effect?

6
All these must be well documented for true planning.
1.4 Objective
The objective of this work is to give a compact and useful
source regarding the wastes and its existence in our life. Of
course, wastes need to be collected and to take further
steps on them; either landfilling, recycling or producing
useful energy. Dumping of wastes especially when they
are in contact with atmosphere could lead to problems
creations in air, smells and pollution directly or through
burning and the adverse effects on public health. Many of
such problems could be reduced by proper handling with
wastes. Therefore, some of the goals are to put some
discussions about all above in simplified, concise and in
useful manner.
Questions
1-what is the waste management?
2-on what factors treatment and management of wastes
depend on?
3-what is the benefit of recycling of waste? Is it suitable for
all wastes?
4-what type of waste treatment do you recommend?

7
References
1-Takele Tadesse. Solid Waste Management, by Ethiopia
public health, Ethiopia, 2004.
2-Young, Gary C. Municipal Solid Waste to Energy
Conversion processes, Economic, Technical and
renewable Comparisons published by John Wiley &
Sons, Inc., 2010.
3-Joseph T. Swartzbaugh and Donovan S. Duvall.
Recycling Equipment and Technology for Municipalities
Solid Waste, Material Recovery Facilities Noyes Data
Corporation USA, 1993.
4-Richard Porter and Tim Roberts. Energy Savings by
Wastes Recycling, Published by Taylor & Francis e-
Library, 2005.
5-Haghi, A.K. Waste Management, research advances
convert waste to wealth, Nova Science Publishers, Inc.,
2011.
6-https://www.wastereduction.gov.hk/sites/default/files/wr_
glass.pdf
7-Khan, Iqbal H. and Ahsan, Naved. Textbook of Solid
waste Management, CBS publisher, India, 2009.

8
8-Prasanna Kumar, WG et al. Waste Management
Treatment Technologies and Methods, first edition.
Published by Mahatma Ghandi National Council of Rural
Education, Hyderabad, 2019.
Further Readings
1-Bates M. Collection and Transport Special. Waste
Management World, January–February, 2004.
2-Bonomo L. and Higginson A.E. International Overview on
Solid Waste Management. Academic Press, London,
1988.
3-Waste Management Paper 26F. 1996. Landfill Co-
disposal (Draft). Department of the Environment, HMSO,
London.
4-Waste Management Planning. Principles and Practice.
Department of the Environment, HMSO, 1995.
5-Wheatley A. Anaerobic Digestion. A waste Treatment
Technology. Elsevier Applied Science, London, 1990.
6-Elagroudy Sherien, Mustafa A. Warith and Elzayat
Mohamed. Municipal solid waste management and
green economy. Published by Global young academy,
Belin, Germany, 2016.

9
Chapter Two Waste Materials Diagnosis
Generally speaking, wastes can be classified as1-3
;
1. food remaining 2. plastics 3. wood, grasses 4. metals
5. glasses 6. papers 7. building materials.
Another detailed classification can be found in table 2.1
below
Table 2.1. Sources of wastes
No Source Typical waste
generators
Types of solid wastes
1 Residential Single and
multifamily
dwellings
Food wastes, Paper,
cardboard, plastics,
textiles, leather, yard
wastes, wood, glass,
metals, ashes, special
wastes (e.g. Bulky items,
consumer electronics,
white goods, batteries, oil
tires) and household
hazardous wastes.
2 Industrial Light and heavy
manufacturing,
fabrication,
construction
sites, power and
chemical plants
Housekeeping wastes,
packaging, food wastes,
construction and
demolition materials,
hazardous wastes, ashes,
and special wastes, Spent
oils.
3 Commercial Stores, hotels,
restaurants,
markets, office
buildings, etc.
Paper, cardboard,
plastics, wood, food
wastes, glass, metals,
special wastes, hazardous
wastes

10
4 Institutional Schools,
hospitals,
prisons,
government
centers
Same as in commercial
5 Construction
and
demolition
New construction
sites, road repair,
renovation sites,
demolition of
buildings
Wood, Steel, concrete,
dirt, etc.
6 Municipal
services
Street cleaning,
landscaping,
parks, beaches,
other
recreational
areas, water and
wastewater
treatment
Industrial process wastes,
scrap
materials, off- specification
products, slag tailings
7 Processes Heavy and light
manufacturing,
refineries,
chemical plants,
power plants,
mineral
extraction and
processing
Industrial process wastes,
scrap
materials, off- specification
products,
slag, tailings
All of the above must be included as” municipal solid waste.”
Agricultures Crops, orchards,
vineyards,
dairies, feedlots,
farms
Spoiled food wastes,
agricultural
wastes, hazardous wastes
(e.g.
pesticides)
Depending on the type of waste which in turns depends to
some extents on the areas and on the living manner,
wastes can take the following classifications as in table 2.2:

11
Table 2.2. Composition of the wastes
Components Low income Middle income Upper income
1-Organics
Foods 40-85 20-65 6-30
Paper 1-10 8-20 20-45
Cardboard --------------- ----------------- 5-15
Plastics 1-5 2-6 2-8
Textiles 1-5 2-10 2-6
Rubbers ------------------- --------------------- 0-2
Yard Wastes 1-5 1-10 10-20
Wood ------------------ ------------------- 1-4
2-Inorganics
Glass 5 5 8
Aluminum 2 2 0
Dirt, Ashes 20 15 5
The main categories of the wastes can also divided to sub
classification as in table 2.3 below4
;

12
Table 2.3. Subdivision of the waste
constituents4
Material %by weight
newspaper 33
Mixed paper 41
Total paper 74
Glass bottles
Clear
brown
green
11
4
4
Tin cans 4
Aluminum 1
Plastic containers
Pet HDPE
1
1
Total commingled
container 26
Total 100
2.1 Important properties of wastes
Some properties of solid wastes such as physical,
chemical, biological are very important in diagnosis the
identity of the wastes. They are as follows3
;
1-specific weight. Is the quantity of solid waste per unit
volume (ton/m3
). This property is varied with its condition
such as, if the waste compact or not, the temperature and
the location also affect the specific weight. Determination of

13
specific weight can be determined by means of a cubical
container, usually 60*60*60 cm3
. The container is filled to
overflow with the waste taking care to keep
homogeneousity. The container is tamped thrice by lifting it
6 cm above the ground and dropping it squarely. After this
consolidation the top of the container is leveled. Finally, the
specific weight is calculated after weighing the container as
follows:
specific weight= (Wws-Wc)/Vc …………… 2.1
where Wws is the weight or mass of container with the
waste.
Wc is the container weight and Vc is the volume of the
container.
Table 2.4 shows specific weight for some types of wastes

14
Table 2.4 Specific weights of some solid wastes3
Waste type Range (ton/m3) Typical (ton/m3)
Food wastes
Paper
Cardboard
Plastics
Textiles
Rubber
Leather
Yard wastes
Wood
Glass
Tin Can
Silt/ash/dirt
0.2-0.4
0.05-0.1
0.04-0.06
0.05-0.07
0.05-0.07
0.1-0.15
0.1-0.2
0.05-0.15
0.15-0.3
0.1-0.2
0.1-0.2
0.6-1.5
0.29
0.09
0.05
0.06
0.06
0.13
0.16
0.1
0.23
0.15
0.15
1.20
2-moisture. Is the quantity of water in the wastes calculated
as a percentage based on either wet or dry basis3
? The
determination process is as follows; weighing a specified
quantity of solid wastes to give wh, then drying the sample
at 1050
C till constant weight to give wd, eventually the
moisture m is

15
m=(wh-wd)/wd …….2.2
In case of flammable waste, drying at 70-75 0
C is sufficient
while for biodegradable one about 40 0
C drying is sufficient.
Table 2.5 gives some values of the waste’s moisture.
Table 2.5 Specific weights of some solid
wastes3
Moisture content
Wastes component Typical
%
Range %
60
6
2
10
2
8
60
20
2
2
15
50-80
4-10
1-4
5-15
1-4
5-10
30-80
10-30
1-3
1-3
10-30
Food wastes
Paper and cardboard
Plastics
Textiles
Rubber
Leather
Yard Wastes
Wood
Glass
Metals
Slit/Ash/Dirt

16
3-field capacity. This property is very important because it
affects the leachate generation in the landfill. Moisture
available in solid wastes excess of its field capacity is
released later as leachate.
4-pearmabilty. This property is an indication for the ease of
a fluid (liquids or gases) movement inside the dump of the
wastes. It is affected by pores or voids and the
compactness of the wastes. It is better to collect samples
using the following criteria1-5
:
1-analyze the components of municipal solid waste by type
2-sorting and separation of each and every component is
necessary
3-the samples should include all seasons of the year
4-there are differences must be taken into consideration
such as luxury of the areas, some habits in wearing or the
nature of foods also give some identification to the wastes.
2.2 Recovery prospects of wastes
In this section the materials checked were aluminum,
plastics, paper, glass, rubber, metals (ferrous and non-
ferrous), waste oils, and solvents. These materials
aluminum, plastics, waste paper, glass, rubber and wood

17
have been selected for detailed analysis. These products
were considered to have the greatest additional potential
for energy savings. In the EEC (European Economic
Countries) countries, the recovery strategy and the
estimated values were given and fixed as can be seen in
table 2.6 below6
Table 2.6. Scheduling of the wastes quantities in EEC
Countries and the rated recovery values6
Physically
available for
further
recovery
Currently
recovered
Estimated
arising
Material
1.049
0.385
1.479
Aluminum
9.880
1.710
11.590
Plastics
16.065
12.00
28.068
Waste Paper
7.100
1.810
8.910
Glass
1.15
0.500
1.65
Rubber
19.500
0.500
19.500
Wood
1. For aluminum. The total arising's of aluminum in the
EEC in municipal and postconsumer wastes are
estimated as 1.5 million tonnes6
, 385 million tones are
currently recovered. The main end uses and current
recovery activity for aluminum are summarized in
table 2.7.

18
Table 2.7. Values of the recovered quantity of aluminum6
Aluminum – Main uses and recover activity
End Uses Processed Current recovery activity
Transport
Mechanical
Engineering
Electrical
Engineering
Construction
Chemical
Packaging
Consumer
Durables
Steel
alloys
Destructive
Uses
Pure aluminum – mainly
foil and principally in
packaging industry.
Casting alloys – aluminum
alloyed with silicon,
cooper, magnesium etc..,
for casting purposes.
Wrought alloys – are
rolled, drawn, extruded or
formed by some fabricating
method other than casting,
to produce sheet, wire,
forgings, extrusions or
tubes.
Other forms – use of
aluminum in alloys and
production of aluminum
chloride and explosives.
In- plant prompt scrap
recovery: High level of
recovery – approaching
100%
Process plant scrap
Recovery: High level of
recovery – approaching
100%
Recovery of old scarp:
Post-consumer scarp
(consumer durables,
capital goods, cars);
Recovery of post-
consumer waste widely
practiced.
Domestic and consumer
wastes (Packaging):
Recovery of packaging
from domestic and
commercial wastes at
very 10w level.
The recovery of waste aluminum is well established,
around 28% of the aluminum processed in Europe is
recycled metal. There is a very incentive to maximize
aluminum recovery as only 12% of consumption is

19
available from local mining production. There is a very high
level of recovery of prompt and process wastes. Many
conditions describe the final availability state of that
aluminum as a new condition. This new condition scrap is
clean scrap arising in-plant either from initial forming or
from final fabricating activities or it is available due to
rejections in some steps of processing. It could take any
shapes depending on the fabrication process or depending
on the producing sections for military or domestics…. etc.
For this type of new scrap, the economics of recovery are
highly favorable, why? Such scrap finds a ready market for
resale either to the primary or secondary metal industries
and recovery is thought to approach 100%. More than 60%
of the industry’s scrap waste is ‘new’ scrap. The
opportunities for further recovery of these wastes are very
limited.
When the wasted aluminum is old, recovery of such parts
needs some labors such as separation, cleaning or
chemical cleaning. In general, this type needs more labors
or energy consumption.
2. For plastics. The total arising’s of plastics in EEC in in
different areas are estimated as 11.6 million tons. About

20
1.7 million tons are currently recovered. Table 2.8 gives the
recovered quantity and the main uses of Plastics
Table. 2.8. The recovered quantity of Plastics and main uses6
Plastics – Main uses and recover activity
End Uses Processed Current recovery
activity
Building
Packaging
Electrical
products
Automotive
products
Furniture
Monomers are
chemically combined to
produce polymer resin
which may then be
compounded with
additives to change
properties, e.g. make
more rigid, flexible, heat
– resistant, opaque, etc.
Thermoplastic resins
provided to fabricators in
from of lattices, pellets
for shaping either by
injection moulding , blow
moulding, extrusion or
thermo – forming
Thermosetting: resins
provided in granular or
liquid from and are
usually processed by
compression, transfer
moulding casting or
calendaring
In-plant prompt scarp
recovery by resin
manufactures, high
level of recovery.
Process plant scarp
recovery: by
fabricators and
converters – or
independent
reprocesses high level
or recovery
Recovery of old
scarp:
post – consumer scarp
(consumer durables,
capital goods, cables):
low level of recovery.

21
Since talking is about recycling, therefore, emphasis should
be focused on thermoplastics since it has a wide
application and uses.
There are some limitations regarding the plastics recycling:
a. Thermoplastics have many origins depending on raw
materials and solvents, therefore, they must be separated
before refabricating processes, otherwise some problems
may appear in the future with the produced products.
b. Thermosets are excluded in recycling process since
these products cannot be remolded under heat or
pressure. In general, the dirtier plastics, the wetter and the
more mixed plastics will give bad quality and greater cost
for converting.
Rubber is considered as one of polymer products and it
has a valuable waste recovery such that for every 1.6
million tons of wastes there is 0.5 million tons are
recovered. As the case with many of wastes, the age of the
product and the effects of weather such as the heat or the
sun, exposure to rains especially the acidic have a
pronounced effects on the composition and the physical
statue of the wasted rubber. Some of the rubbers can be

22
used directly as a mean to produced energy by combustion
process.
3. For Paper. This type of waste compromising all types
represents the largest compounds of Municipal solid waste
(MSW)6
. The percentage of this type of waste in European
countries is about 10-45%. Figure 2.1 shows some types of
paper wastes. About 40% of waste was recovered6
.
a. Mixed

23
b. Carton / Cardboard
c. Other packaging

24
d. News paper
Figure 2.1. a-d different types of
paper waste
Table 2.9. shows some properties and uses of paper
and the recovery process5
as can be seen below:

25
Table 2.9. Recovery of waste paper6
Waste paper and board – Main uses and recover activity
End Uses Processed Current recovery activity
Newsprint
Other
printing and
writing paper
packaging
paper and
board
Construction
paper and
board
household and
sanitary paper
Mechanically produced
pulp is used mainly in
products not designed
for permanent use, e.g.
newspaper and
magazine.
Chemical pulp (e.g.
kraft pulp) is stronger
than mechanical pulp
and is used extensively
in brown paper
manufacture (e.g. carrier
bags. Corrugated board.
etc.)
Writing paper can be
made from all qualities
of pulp. Tissues are
made from chemical
pulp. Board manufacture
utilities a high proportion
of waste paper often in
laminate structure.
In-plant prompt waste
recovery: high level of
recovery.
Process Plant
recovery by:
manufactures converts
and printers’ high level
of recovery.
Recovery of old
waste-newspapers,
fiber board containers
fixed waste paper from
domestic trade and
industrial Sources: high
level of recovery from
industry and commerce
variable level of
recovery from domestic
sources but generally
not high.
Paper wastes are also considered either new which gives
a clean, homogeneous pulps and accepted by the
manufacturer of the recycling process or old which has
many uses knowing that the old paper in general suffers

26
from fungi or decay which must be taken into consideration
before recycle process as well as some chemical
processes in removing colures for papers having colored
shapes.
4. For Glass. Glass is available in the wastes in several
forms; bottles, jars…etc. It has many applications such as
medicine, scientific laboratories, domestic applications and
so on. In general, glass consists of 70% or above silica
(SiO2) and a small percentage of soda ash (Na2CO3) or
potash (K2CO3) and lime (CaO). The occurrence and
supplies of all these components are abundant,
widespread and cheap throughout the world. Glass is
chemically inert. It does take up some space when buried
at landfills but remains stable and will not release any toxic
substance into the environment. Unlike metals and paper,
there is very little economic advantage in using recycling
glass versus virgin materials, the incentive to use waste
glass and the price offered by the overseas market are
inevitably low and can hardly cover the collection and
transport cost. The total arising of glass in EEC is about 9
million tons of which 1.8 tons are currently recovered4
.

27
Table 2.10 below shows some details of glass wastes and
its recovery6
.
Table 2.10. Glass wastes and its recovery6
Glass – Main uses and recover activity
End Uses Processed forms Current recovery
activity
Flat glass
(windows etc.)
Containers
(packaging and
industrial)
Domestic
(household and
ornamental)
Glass fiber
Miscellaneous
(safety, optical,
laboratory,
hygienic and
pharmaceutical,
illumination, etc.)
Main types of processed
glass
o lead – alkali-silica
('flint' glass, crystal
glass)
o borosilicate glass
(good thermal
characteristics)
o aluminosilicate glass
(good chemical
resistance)
o aluminoborsilcate
glass (low thermal
expansion, high
chemical resistance)
Produced as flat glass,
hollow glass and glass
fiber.
Prompt waste in glass
manufacture: high
level of cullet
recovery.
Process waste from
glass using industries:
high level of recovery
of uncontaminated
cullet
Recovery of post-
consumer waste:
Cullet in domestic and
trades wastes (mainly
packaging): generally
low level of recovery.
In Hong Kong government encouraged8
crushing the waste
glass container to form a glass sand which will replace
natural river sand as an engineering material for the
production of suitable construction materials such as eco-
pavers (Figure 2.2). There are also other applications in

28
certain public works (such as reclamation and earth works
including site formation, backfilling and road sub-base) that
may absorb recycled glass materials as fill material.
Figure 2.2. Glass sand8
Wood is available also as a waste as in the forests or
directly as a waste from homes, in general the production
of wood in EEC is about 19.5 million tones 0.5 million tones
are currently recovered4
, this represents a small value.
Some of wood can also be blended with some polymers
and with other additives to be used in fabricating some
objects such as furniture. Nevertheless, the main usage of
wood waste and yarn is to produce energy through
combustion process as will be shown lately.

29
5. Hazardous Waste. Many of the hazardous materials are
metals, batteries with some harmful metals as parts of
them, some organics cleaning solutions, pesticides, paints,
some thinners for paints, used motor oils….etc. some of
these wastes can be recovered or treated to be used in
another form, while the rest cannot. More discussion will be
given to the hazardous waste in the coming chapters.
Questions
1-what types of factors that affect the diversity of
wastes?
2-in the specifying weight of waste determination, do the
shape and dimensions of the wastes as a unit affect
such determination?
3-which type of waste is better for using as a substrate
for collecting gases; that type with high permeability
value or with low one? Why?
4-make a comparison between the cases of using a new
aluminum and plastics in industry and the recovered
one.

30
References
1-Takele Tadesse. Solid Waste management; lecture
notes, Produced in collaboration with the Ethiopia Public
Health Training Initiative, The Carter 2004 Center, the
Ethiopia Ministry of Health, and the Ethiopia Ministry of
Education.
2-Gary C. Young. Municipal Solid Waste to Energy
Conversion Processes Economic, Technical and
Renewable Comparisons, edited by John Wiley & Sons,
Inc., 2010.
4-Joseph T. Swartzbaugh and Donovan S. Duvall.
Recycling Equipment and Technology for Municipal Solid
Waste, Material Recovery Facilities, edited by Noyes
Data Corporation USA, 1993.

31
6-Richard, Porter and Tim, Roberts. Energy Savings by
Wastes Recycling, Published by Taylor & Francis e-
Library, 2005.
7-Haghi, A.K. Waste Management, research advances
convert waste to wealth, Nova Science Publishers, Inc.,
2011.
8-https://www.wastereduction.gov.hk/sites/default/files/wr
_glass. pdf

32
Further Readings
1-APME. Good practices guide on waste plastics recycling,
a guide by and for local and regional authorities.
Association of Plastics Manufacturers in Europe, Brussels,
Belgium, 2004.
2-Atkinson W. and New R. Kerbside collection of
recyclables from household waste in the UK. Warren
Spring Laboratory, Report No. LR 946, National
Environmental Technology Centre, Harwell, 1993.
3-Basta N., Fouhy K. and Moore S. Prime Time for Post-
consumer Recycling. Chemical Engineering, February,
1995.
4-Campbell M.C. Non-ferrous metals recycling, Recycling
Technology Newsletter. Natural Resources Canada,
Ottawa, Ontario, Canada, 1996.
5-Crittenden B. and Kolaczkowski S. Waste Minimization:
A Practical Guide. Institution of Chemical Engineers,
Rugby, 1995.
6-Everett J.W. and Peirce J.J. Curbside Recycling in the
USA: Convenience and Mandatory Participation. Waste
Management and research, 11, 49–61, 1993.

33
7-Holt G. Opportunities and Barriers to Metals Recycling.
Recycling Advisory Unit, National Environmental
Technology Centre, AEA Technology, Harwell, 1995.
8-Williams, Paul T. Waste Treatments and Disposal, 2ed
,
John Wiley & Sons, Ltd. 2005.
9-https://mpra.ub.uni-muenchen.de/71518/MPRA Paper
No. 71518, posted 22 May 2016.

34
Chapter Three Waste as an Energy
As stated earlier, MSWs are composed of several
materials, some of them are combustible, i.e., having a
specified heating value when they are burned (such paper,
plastics, yards, wood….etc.) while the rest are not, where
this type has no power to be burned such as metals,
glasses, plasters….etc.
One of the main uses of wastes is to produce energy in
what is termed waste to energy WTE, hence giving heating
services or an electricity, for example. According to US
WTE industry, on the average, combusting one ton of
MSW in a modern WTE power plant generates a net of 550
kilowatthours1
which equals to importing one barrel of oil.
The combustion of MSW in WTE facilities reduces US
greenhouse gas emissions GHG by 40 million ton of CO2.
Table 3.1 gives a comparison of the gas emissions among
several energy sources. By inspecting table 3.1, there are
great differences between the MSW emissions and the rest
which gives the vantages to the wastes as a source of
energy especially by knowing that the total cost of burning
the MSW is too low compared to other sources.

35
Table 3.1. Comparisons of air emissions of various
energy sources1
Fuel Air Emissions kg/MWh
CO2 SO2 NOx
MSW* 2.45 379.66 0.36
Coal 2.72 1020.13 5.90
Oil 1.81 758.41 5.44
Natural gas 0.77 514.83 0.04
*Note that the emissions are based on incineration a way from
other ways of using MSW such as CH4 production.
Example 3.1. Assume that the generated electricity of
ton of waste is 550 kilowatt-hours, what was the heating
value of kilogram of waste? What were the emitted
gases per kg of wastes?
Solution
1-550 *1000 (J/sec). hour*3600 sec/hour ≈2*109
J/ton
=2* 106
J/Kg
Requirement 2 will be left to the reader to get the kg of
emitted gases by using table 3.1
Notice; It is assumed that the combustion process or
each kg of wastes has no losses.
Example 3.2. With respect to example 3.1, can you
represent the combustion process by a balanced
equation?
Answer. No, due to absence of any information about
the combusted material composition.
In 2002 US WTE facilities generated a net 13.5*109
kWh of
electricity greater than all other renewable energy sources

36
with the exception of hydroelectric power and geothermal
power as can be shown in table 3.2 below;
Table 3.2. Values of generated electricity for renewable
energy sources1
Energy source KWhx109generated % of renewable
energy
Geothermal
WTE
Landfill
Wood/biomass
Solar thermal
Solar photovoltaic
Wind
13.52
13.50
6.65
8.37
0.87
0.01
5.3
28.0%
28.0%
13.8%
17.4%
1.8%
0.0%
11.0%
Total 48.22 100.0%
Focusing on table 3.2 reveals that WTE of MSW is
profitable for several reasons; the first that we cannot
eliminate the MSW from our life since it represents a
natural state of the life career; the second, it costs only
collection, transportation and sorting and no importing or
using complicated technological instruments in dealing with
it ,while the third reason lies in that WTE facilities needs a
small area of plant erection and working, for example
100000 m2
of land are needed to treat 3 million tons of
wastes. WTE process can be done using direct method
such as combustion process of waste or indirect by

37
collection of the produced gases by other methods.
Combustion of waste can be done by incinerator.
In many countries, landfill is the main route to dispose of
wastes. It was found since the beginning of human living
on earth. Useful gases and energy could be wasted by this
route. Incineration is needed for combusted wastes which
is the oxidation of the combustible material in the waste to
produce heat, water vapor, nitrogen, carbon dioxides2,3
and
others ,depending on the composition of the wastes as well
as to reduce the quantity of wastes. These flue gases are
emerged at a temperature of 1000-12000
C and must be
cooled before sending them to the cleaning unit. The best
solution for cooling is to raise the temperature of the
feeding water of a boiler (using waste heat). There are
some factors affecting incinerator4
such as efficiency. The
efficiency of incinerators is measured by measuring the
unburnt materials or the flue gases and the ash in the
bottom. There are important parameters must be taken into
consideration regarding the design of incinerator , such as
combustibility, temperature, turbulence and the resistance
time for combustion process. The combustibility of a
material in the incinerator is termed buy calorific value.

38
Generally, a value of 2500 kcal/kg or more is preferred for
incineration. Excess air affects this value of energy and
selecting of the appropriate quantity is very economical in
use. There must be also a compromise between the
quantity of the burnt waste and the moisture content since
as the moisture increases, waste quantity should increase
to keep the temperature of the incinerator within the
working limit. For proper working of incinerator, turbulence
of air and mixing with the wastes should be kept by swirling
of air current to insure a good conditions of burning to take
place. In some cases, rotating kiln makes the same
purposes. In some small incinerators raking is required in a
regular interval to keep mixing. To insure complete
combustion process, there must be a residence time that
fulfills such a task. It can be maintained by adjusting the
frequency of ash removal, for other cases adjusting the
speed of the kiln can give the required intent. There are
some advantages of incineration as follows2
:
1. location of incinerator is close to the waste collection site
which save money in transportation and collection.
2. incineration process evolves no methane which is a
greenhouse gas that contributes to warming of the global.

39
3. waste incineration is a source for energy recovery to
produce steam for electrical power stations or providing hot
water for district heating, by this conserving of valuable fuel
resources.
4. the bottom ash residues can be used for materials
recovery or as secondary aggregates in construction. A
worked example, for incineration can be given below:
Example 3.3
Assume that an incinerator processes a 2500 ton of
waste with a calorific value of 10 MJ/kg, how many
houses this quantity will sustain an electric current
assuming that the electricity generation is 30%
efficiency?
Solution:
2500*103
kg*107
MJ/kg=2.5*1013
J
2.5*1013
J*0.3=7.5*1012
J
The average daily consumption of electricity in US is
about 30 kWh=1*108
J
Then the number of houses =7.5*1012
J/1*108
J
=75000 houses
Comment; can you compare this value based on Iraq?

40
In return incinerator has disadvantages:
1. capital investment is too high and the pay back could
take much time.
2. incinerator is designed to give some calorific value which
could not be kept in touch along the time.
3. incineration process still gives a solid residue which has
to be managed.
4. although the incineration process -in general- complies
with environmental legislation, there still a concern about
the emitted levels and its effect on health.
3.1 Types of incinerators
There are several types of incinerators according to the
incinerator institute of America that divides them to nine
classes depending on the use and size and on the type of
wastes as given in tables 3.3-3.44

41
Table 3.3. Classification of wstes3 used in incinerators
T
y
p
e
Major Components Approx..
Composition
(%by wt)
Non-
Compos
ition
Solids
Btu
Value/Ib
Requirement
for Auxiliary
fuel (Btu per
Ib of waste
Recommen
d-ed
Minimum
Input (Btu
per Ib of
waste)
0 Trash highly
combustible (paper,
wood, cardboard
cartons, and up to
10% treated papers,
plastics or rubber
scraps)
source: commercial
and industrial
Trash 100
Moisture
Content 10
5 8500 0 0
1 Rubbish
combustible waste,
paper, Cartoon,
rage, wood scraps
combustible floor
sweepings, Source:
Domestic
commercial and
industrial
Rubbish 80
Garbage 20
Moisture
Content 25
10 6500 0 0
2 Refuse Rubbish
and garbage
sources: Domestic
Rubbish 50
Garbage 50
Moisture
Content 50
7 4300 0 1500
3 Garbage animal and
vegetable waste
Sources: Hotels,
restaurants,
markets,
institutional,
commercial and
clubs.
Garbage 65
Rubbish 35
Moisture
Content 70
5 2500 1500 3000
4 Animal Solids and
Organics carcasses,
oranges, solid
organic wastes
Sources: Hospitals,
laboratories,
Animal and
human
tissue 100
Moisture
Content 85
5 1000 3000 8000
(5000
primary)
(3000
secondary)

42
abattoirs,
animal pounds etc.
5 Gaseous, Liquid, or
Semi – liquid
industrial process
wastes
Variable Depend
ent on
major
compon
ents
Variable Variable Variable
6 Semi – solid and
solid combustibles
requiring hearth,
retort, or grate
equipment
Variable Depend
ent on
major
compon
ents
Variable Variable Variable

43
Table 3.4. Standard of construction and performance for
different types of incineratores4
Class Subject
I Portable packaged completely assembled, direct
incinerators having not over 5 ft3 storage capacity or 25
Ib/hr burning rate suitable for type 2 waste.
IA Portable packaged or job assembled, direct–feed
incinerators having a primary chamber volume of 5 to
15 cu ft or a burning rate 25 Ib/h of type 3 waste.
II Flue – fed single chamber incinerators with more than 2
cu ft burning area for type 2 waste. This incinerators
type is served by one vertical flue functioning as a chute
for both charging waste and carrying the products of
combustion to the atmosphere. Usually installed
apartments or multiple dwellings.
IIA Chute-fed single chamber incinerators for apartments
building with more than 2cu ft burning area suitable for
type 1 or 2 waste. Not recommended for industrial
installation. In this incinerator separate flue for carrying
the emissions to atmosphere is provided.
III Direct – feed with a burning rate of 100 Ib/h and suitable
for burning type 0, 1, or 3 waste
IV Direct – feed with a burning rate of 75 Ib/h more suitable
for burning type 3 waste.
V Municipal incinerators suitable for type 0, 1, 2 or 3
waste or combination of these. Rated in tons per hour or
tons per day.
VI Crematory and pathological incinerators suitable for
types 4 waste.
VII Designed for specific by – product waste, type 5 or 6

44
Some examples of incinerators are Mass fired, RDF
(Refuse Derived Fuel) fired, fluidized bed type.
Mass Fired Incineration: Mass fired combustion systems
are designed to incinerate the municipal solid wastes as
collected without or with very little prior processing. The
energy produced by mass fired combustion system
depends upon the composition of municipal solid waste. A
typical mass fired incinerator is shown in figure 3.1
RDF Based Incineration: In RDF fired combustion system,
processed solid waste refuse derived fuel (RDF) is burnt.
Various components e.g. metals, glass and other
noncombustible materials are removed to produce RDF.
Since RDF is more homogeneous, the system is better
controlled for combustion and more energy is recovered.
Fluidized Bed Incineration: A fluidized bed type combustion
system includes a steel vertical cylinder, lined inside with
refractory bricks, and has a sand bed. Air nozzles called
tuyeres are provided to inject air at high pressure. Fig.3.2
shows a typical fluidized bed incinerator. Solid fuel (or
RDF) is injected into the cylinder, auxiliary fuels such as
natural gas or oils may be used initially to increase the

45
temperature of the bed up to operational level which is
about 14501o 17500
F. This system can also be used for
burning of sewage sludge and other chemical wastes.
Figure 3.1. Mass Fired Incinerator4
Figure 3.2. A Typical Fluidized Bed incinerator

46
The waste characteristics which is suitable for
incineration can be represented by figure 3.3, a ternary
diagram which shows the analyses of the combustible
waste4
. The shaded area represents the most suitable
waste for combustion without the requirement of
auxiliary fuel.
Figure 3.3. Suitability of solid wastes for combustion2.
A typical modern incineration unit can be shown by
figure 3.4

47
Figure 3.4. A typical Incinerator2
An incinerator is divided into the following part:
1. waste delivery, bunker and feeding system.
The waste is delivered by any suitable transportation
means according to the distance between collection and
sanitary and according to the quantity, i.e., by train,
vehicle…etc. The delivered wastes are variable and have
more than one type that they may have very different

48
combustion properties which would influence incinerator
performance. The bunker is large enough to allow for
storing the waste4
. Therefore, the bunker can be designed
to hold about 2–3 days equivalent of weight of waste which
would be typically 1000-3000 tons of waste. Longer periods
of storage are undesirable due to the rotting of the waste
and consequent bad odors.
2. furnace
Figure 3.5. shows the furnace4
Figure 3.5. Furnace in the incinerstor4
During the start-up of the incinerator, auxiliary burners are
used to raise the temperature of the gases to initiate waste

49
combustion. The waste is fed into the furnace usually by an
independently controlled ram. In the furnace the waste
undergoes three stages of incineration4
:
a. drying and de-volatilization;
b. combustion of volatiles and soot;
c. combustion of the solid carbonaceous residue.
As the waste enters the hot furnace, the waste is heated up
via contact with hot combustion gases, pre-heated air, or
radiated heat from the incinerator walls, and initially
moisture is driven off in the temperature range 50–100°C.
The water content of waste is very important since heat is
required to evaporate the moisture, thus more of the
available calorific value of the waste is lost in heating up
the wet waste and so less energy is available. In addition,
the rate of heating up of the waste, and therefore the rate
of thermal decomposition, will also be affected by the water
content of the waste. Water contents of municipal solid
waste can vary between 25 and 50%. As long as the
moisture is removed, thermal decomposition of the wastes
is the next step which produces some volatiles,
combustible gasses and vapors. The combustion of

50
volatiles to produce the flames of the fire takes place
immediately4
.
3. heat recovery
The emitted gas of the combustion zone is at a
temperature of 750-10000
C, this temperature can be used
in a boiler to evolve steam or to use heat in another places
and to cool the gases to be used as a cleaning means.
4. emissions Control
There must be emitted gases due to combustion
processes; dust, acidic gases such as hydrogen chloride,
hydrogen fluoride and sulphur dioxide, and heavy metals
such as mercury, cadmium and lead. In addition, the
combustion efficiency is controlled by limits on the
emission of carbon monoxide and organic carbon above
the surface of the waste on the grate and in the combustion
chamber above the grate. Table 3.5 gives the typical
concentration ranges for emissions before any gas clean-
up treatment for a range of European municipal solid waste
incineration plant.

51
Table 3.5. The range of emitted gases after the boiler and
before the gas clean up.
Emission Units Range
Total dust
TOC
Hydrogen chloride
Hydrogen fluoride
Carbon monoxide
Sulphur oxides
Nitrogen oxides
Cadmium + thallium
Mercury
Other heavy metals
Pb, Sb, As, Cr, Co, Cu, Mn, Ni, V, Sn
Dioxins and furans (PCDD/PCDF)
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
mg/m3
ngTEQ/m
3
1000-5000
1-10
500-2000
5-20
5-50
200-1000
250-500
<3
0.05-0.50
<50
0.5-10
3.2 Combustion principles
Whether the wastes are combusted in normal case
(outdoor) or in incinerator or boiler, oxygen or air is the
necessary combustion means to give heat and smokes or
gases as the products of the combustion process. The
most combustible materials are carbon and hydrogen and
they are found in the solid, liquid and gas material. Oil for
example and gas are the main combustible material due to
their chemical structure composed of C and H atoms.
Other elements are also having the chance to be available
in the wastes in some proportions, table 3.6 shows such

52
elements and Table 3.7 displays the chemical reactions of
combustion.
Table 3.6. Elements and Compounds Encountered
in Combustion 5
Substance Molecular
symbol
Molecular
weight
Form Density@70
°F (Ib/ft3)
Carbon
Hydrogen
Sulfur
Carbon monoxide
Oxygen
Nitrogen
Nitrogen atoms
Dry air
Carbon dioxide
Water
Sulfur dioxide
Oxide of nitrogen
Hydroxide
Chloride
C
H2
S
CO
O2
N2
N2atm
CO2
H2O
SO2
NO2
HCl
12.0
2.0
32.1
28.0
32.0
28.0
28.2
29.0
44.0
18.0
64.1
-
36.5
Solid
Gas
Solid
Gas
Gas
Gas
Gas
Gas
Gas
Gas/liquid
Gas
Gas
Gas
-
0.0053
-
0.0780
0.0846
0.0744
0.0748
0.0766
0.1170
0.046
0.1733
-
0.1016
These reactions result in complete combustion, that is, the
elements and compounds unite with all the oxygen with
which they are capable of entering into combination. In
actuality, combustion is a more complex process in which
heat in the combustion chamber causes intermediate
reactions leading up to complete combustion.

53
Table 3.7. Chemical reactions in combustion process5
Combustible Reaction
Carbon
Hydrogen
Sulfur
Carbon monoxide
Nitrogen
Nitrogen
Nitrogen
Chlorine
C+O2=CO2
3H2+O3=3H2O
S+O2=SO2
2CO+O2=2CO2
N2+O2=2NO
N2+2O2=2NO2
N2+3O2=2NO3
4Cl+2H2O=4HCl+O2
It could some other transformations of products in table 3.6
to other forms depending on kinetic of combustion process
and on thermodynamics. Most of these gases have
detrimental effect to human, animal and plants or to the
globe as a whole if they were emitted in more than
allowable limit. Therefore, one of the problems of WTE
facility is to check emissions of gases and even the quality
of the ash.
The energy content of the organic components in municipal
solid waste
can be determined by6
:
 a full-scale boiler as a calorimeter
• by using a laboratory bomb calorimeter

54
• by calculation if the elemental composition is
known.
The moisture in the wastes leads to loss of energy also, it
must be free of ash and moisture. Moisture content is a
highly important also, a highly variable characteristic of
waste materials. The moisture content of MSW is generally
around 25% but, has been observed to vary from 15 to
70%. This variation may be due, for example to seasonal
variations in precipitation, the nature of the waste (e.g.,
grass clippings vs. paper) and the method of storage and
collection (e.g., open vs. closed containers/ trucks). The
moisture content can be calculated usually by two
methods:
1. In the wet -weight method of measurement: the moisture
in a sample is expressed as a percentage of the wet weight
of material.
2. Dry-weight method, it is expressed as a %age of the dry
weight of the material.
Wet- weight Moisture content is expressed as follows –see
chapter two-:
m=(wh-wd)/wd x100% ………….2.2

55
where:
m= wet- mass moisture content, %
wh= initial mass of sample as delivered, kg
wd= mass of sample after drying, kg
The energy values on dry basis can be obtained from the
following in case there is a humidity portion:
Energy as a dry in kJ/kg= energy as discarded*(100/(100-
% moisture))………………………3.1
If it is intended to be given for ash free as well, then:
Energy as a dry in kJ/kg= energy as discarded*(100/(100-
%moisture-%ash)) ………………...3.2
The following example shows how energy of waste is
calculated
Example 3.4. Estimate the energy content of a solid
waste sample with the data given in table 3.8 below
Solution
Adding fourth column to table 3.8 above to give table
3.9. below, assuming that we have 100 kg as a

56
sample, then the energy content for 1 kg is
1474000kJ/100kg=14740 kJ/kg.
Now if it is assumed that 21% moisture is available
in this sample, then the energy content for a dry
basis (eq.3.1) is
14740*(100/(100-21))=18658 kJ/kg (compare this
value with 1474000), what does it refer too?
(Comment).
If for example the sample contains some ash in its
constituent; say 5%, then the energy as a dry basis
and ash free is:
=14740*(100/ (100-21-5)) =19919 kJ/kg.
Table 3.8. Composition and energy content
for MSW sample.
Component Percent
by
weight
Energy
kJ/kg
Food wastes 15 4650
Paper 45 16750

57
Card board 10 16300
Plastics 10 32600
Garden
trimmings
10 6500
Wood 5 18600
Tin cans 5 700
Table 3.9. Continued of table 3.8
Component Percent
by
weight
Energy
kJ/kg
Total energy, KJ (Based
on
100-Kg sample)
Food wastes 15 4650 69750
Paper 45 16750 753750
Card board 10 16300 163000
Plastics 10 32600 326000
Garden trimmings 10 6500 65000
Wood 5 18600 93000
Tin cans 5 700 3500
Total 100 ------- 1474000
For the case in which the energy content for individual
component is not available, then the elemental composition
of the wastes is required. By knowing such analysis, the
higher energy content can be estimated using Dulongs’
formula which takes the form:

58
Energy in kJ/kg=33960C+141890[H2-O/8] +9420S+23N
…....3.3
where C, H, O, N refer to carbon, hydrogen, oxygen and
nitrogen components in weight percent.
DuLong's formula expresses heating value (or energy) in
terms of major solid fuel or waste constituents, their
heating value, and corresponding mass fractions.
The non-combustible materials in the feed, mainly glass
and metals, will end up mostly in the bottom ash. If it is
assumed that the ash leaves the grate at a specified
temperature and a reasonable value for the specific heat of
ash, the corresponding heat loss to inorganic materials fed
with the combustibles is estimated. Accordingly, the effects
of noncombustible on the heating value can be expressed
as follows:
Heating value of mixed MSW = (heating value of
combustibles) *Xcomb-(heat loss due to water in feed)
*XH2O - (heat loss due to glass in feed) * X glass- (heat
loss due to metal in feed) *X metal …………3.4

59
Example 3.5
The composition of simulated MSW is as given in the box
below6
:
Newsprint, representing the paper/cardboard in MSW=35%
Hardwood mulch, representing wood in MSW=17%
Polyethylene, representing plastics in MSW=14%
Animal feed, representing food waste in MSW=5%
Silica, representing glass in MSW=1%
Iron, representing metals in MSW =8%
Water, representing moisture in MSW=20%
Solution: with the values of energy content from
reference7
, the energy value for such waste can be
estimated as:
(0.35 +0.17) *19+0.14*45+0.05*30=17.7 MJ for every kg
of such type of waste.
It should be note that the calorific value or energy value
when calculated by the bomb method, then the value is the

60
higher heating value HHV. This value considered the
product water is in condensed phase which is in contrary to
lower heating value LHV in which water product is in vapor
phase.
Example 3.6
The hydrogen content of MSW is 6.86%, if the moisture
content is found to be 55%, what is the energy content
of 1 kg of this waste6
?
Solution
6.86%*0.45=31.0 g of hydrogen or 15.5 mole H2=15.5
mole H2O on combustion. The released heat of
condensation is 15.5 mole H2*44000 kJ/mol=0.7 MJ (the
value of 44000 kJ/mol represents the heat of
vaporization of water)
Example 3.7
In this case, HHV and LHV of starch in presence and
absence of moisture will be handled, Calculate the LHV for
two samples of starch (C6H10O5) containing 10 and 80%
moisture by weight respectively. HHV of starch is 16.6 MJ

61
kg-1
and Heat of Condensation of water to 55°C is 2.445 kJ
kg-1
Solution
1.Write equation for combustion of starch C6H10O5 + 6O2 →
6CO2 + 5H2O
2. Calculate the LHV of dry starch
a.1 mole starch (monomer) produces 5 moles of water,
molecular weight of starch monomer is 162, water is 18
c.162 kg starch produces 5 × 18 = 90 kg water
d.1 kg starch produces 90/162 = 0.556 kg water
e. LHV of dry starch =16.6 MJ kg-1
starch – (0.556 kg water
kg-1
starch × 2.445 MJ kg-1
water) =15.2 kJ.kg-1
3.LHV (10%moisture) =15.2 × 0.9 –2.445 × 0.1= 13.5 MJ
kg-1
fresh matter
4.LHV (0.8 moisture) =15.2*0.2-2.445*0.8=1.09 MJ kg-
1
fresh matter

62
3.3 Boiler
A boiler7-9
burns fuel to produce heat that converts water
into steam and the steam distribution system takes the
steam from the boiler to the point of use. Boilers
consume much of the fuel used in many production
facilities. The boiler is thus the first place to look when
attempting to reduce natural gas or oil consumption.
Companies are continually searching for fuels less
expensive than coal, fuel oil and gas. Municipal wastes
are inexpensive to be used as fuel comprising
hydrocarbons, pulp mill liquor, sawdust, food processing
waste…etc. Using waste as a fuel in a boiler has the
advantage of reducing the problem of disposals and to
get a continuous source of fuel. Some samples of waste
analysis are given below in table 3.10
Table 3.10. Examples of Composition of
Non-traditional Fuels9
Fuel Sulfur
(S)
Hydro
gen
(H)
Carbon
(C)
Component
Oxygen (O)
Moisture
(H2O)
ASH Heating
Value
(Btu/lb)
Pine bark
(dry basis)
Natural gas
Fuel oil
No.6
0.1%
-
12.0
5.6%
23.3
10.5
53.4%
74.72
85.7
37.9%
1.22
0.92
50%
-
2.0
2.9
%
0.76
%N2
9.030
22.904
18.270

63
Cake
breeze
Bagasse
Municipal
garbage
(metal
removed)
0.6
-
0.1
0.4
0.3
2.8
3.4-
6.3
80.0
23.4
23.4-
42.8
0.5
20.0
15.4-
31.3
7.3
52.0
19.7-
31.3
0.08
11.0
1.7
9.4-
26.8
11.670
4.000
3100-
6500
Generally, there is a good practice when we deal with coal,
gas or fuel oil as a boiler fuel, but with a new fuel, there are
some questions arise10
;
 How high in the combustion chamber should the
new fuel be injected into the boiler? (This is critical
in burning municipal waste.)
 What kind of problems will the ash or residue
create?
 What modifications are needed to burners?
 How will the new fuel be transported to and within
the facility?
 What storage problems can be expected?
 How regular will the supply be?
There are some things have to be taken into consideration
such as the need to have some kinds of backup boiler if the
waste fuel is not available. A second major factor is the
political climate. It is necessary to determine what

64
government agencies must give their approval before a
particular plan can be put into effect. In the case of
municipal refuse, political problems have probably delayed
more projects than technical difficulties, especially where
intermediate storage has been seen as a problem.
Illustrative Case9
In this illustration the cost of different types fuels will be
shown. A company is using process steam at rates that
sometimes reach 300,000 lb/h. The company has a gas
fired boiler performing this job. In another side there is a
local company sending a significant quantity of combustible
wastes to the landfill. A company engineer has suggested
that these wastes might be used as a replacement source
of fuel. His preliminary study has indicated that this usage
of waste as fuel will be acceptable to EPA and to other
local and federal authorities, that the other companies will
buy into this solution, and that there will be no negative
environmental aspects to such usage. The study showed
three alternatives to be viable:
(1) Continue buying gas and sending the waste to the local
landfill;

65
(2) Construct two boilers, one for waste and capable of
efficient operation
from 90,000 to 200,000 lb/h, and one burning coal with an
efficient operating range of 30,000 to 100,000 lb/h;
(3) Construct a single waste-fired boiler with an efficient
capacity of 210,000 to 300,000 lb/h, and charge $15.00/T
for burning acceptable industrial wastes, estimated at
30,000 T/yr from nearby companies.
The first step is to determine the details and costs of each
alternative. Alternative 1, the present system, uses
purchased gas and has costs of trash hauling and landfill
fees added to the usual operation and maintenance of the
boiler. Gas presently costs $5.00/million Btu. Present gas
costs are $2,500,000/yr. This represents about 50 x 1010
usable Btu/yr. The company presently produces 40,000
tons of combustible waste per year. This waste has been
analyzed and found to contain 16% ash by weight and to
have a heating value of 6390 Btu/lb as fired. It is estimated
that a waste-fired boiler of the type contemplated would
have an efficiency of 75%. The usable heat content of this
waste is therefore 6390 Btu/lb x 2000 lb/T x 40,000 T x
0.75 = 38.3 x 1010 Btu/yr, an amount which would need to

66
be supplemented by some other energy source to meet the
needs of the plant. This waste is presently transported to a
landfill at a cost of $1.25/T and then landfilled at $2.50/T
tipping fee. Waste hauling costs for this company are not
expected to increase, but landfill costs are expected to
increase 30%/yr for the next 5 years and 10%/yr thereafter.
These same rates will hold for any ash that is landfilled.
Alternative 2, the two-boiler combination, avoids the gas
cost and all of the cost of waste haulage and waste
landfilling. This alternative, however, causes the company
to incur the initial capital cost of the boilers and higher
operating and maintenance costs than under the present
system. In addition, there is the cost of hauling and
landfilling the ash. The coal to be used has a heating value
of 12,780 Btu/lb and an ash content of 9.6%. The coal
boiler efficiency is estimated as 82%, giving the effective
heating value of the coal as 21 million Btu/T. The amount
of coal needed is calculated from (50–38.3) x 1010
Btu/(12,780 Btu/lb x2000 lb/T x 0.82 efficiency) = 5580
T/yr. Coal costs are projected to be $55.00/T for the near
future. Ash comes from the waste and from the coal; the

67
amount from the waste is 40,000 x .16 = 6400 T/yr; the
amount from the coal is 5580 T x 0.096 = 536 T/yr.
Alternative 3, the large waste-fired boiler, avoids the gas
cost and all of the waste haulage and landfilling expense
but incurs a larger capital cost. This alternative will help
pay for itself with the revenue generated from industrial
customers in addition to the company costs it avoids. This
revenue is estimated as 30,000 T/yr x $15.00/T, or
$450,000/yr. This alternative, however, has ash haulage
and landfilling costs. Since the total amount of waste
burned per year is 70,000 T, the ash to be disposed of is
70,000 T x0.16 = 11,200 T/yr.
Table 3.11 summarizes these costs. In addition to these
costs, a complete analysis would require the depreciation
schedule for each item of capital equipment, the required
after-tax rate of return, and any cost inflation that is
anticipated. With all of these data, the alternatives could be
easily analyzed in one or more spreadsheets. To complete
the analysis, it can be necessary to do a number of
sensitivity analyses testing the sensitivity of the results to a
range of different likely cost scenarios.

68
Table 3.11. Costs of Waste-burning Boiler Alternatives
Present
system
Two boilers One big boiler
First Cost None $12.500.000 $14.000.000
Annual costs
Gas $2.500.000 $0 $0
Coal 0$ $306.900 $0
Boiler
Maintenance
$50.000 $300.000 $250.000
Waste
Transportation
$50.000
(40.000 T x
$1.25)
$0 $0
Waste
Landfilling
(First year)
$100.000
(40.000 T x
$2.20)
$0 $0
Ash
Transportation $0
$8.700
(6940Tx$1.25)
$14.000
(11.200Tx$1.25)
Ash Landfilling
(First year)
$0
$17.350
(6940Tx$2.25
$28.000
(11.200Tx$2.25)
Annual
Revenues
Waste from
other
companies
$450.000
(30.000Tx$15.00/T)
Questions
1-Assume that the generated electricity of a ton of waste is
550 kilowatthours1
what was the heating value of kilogram
of waste?

69
2-What are the benefits of MSW and what distinguishing
features from other sources?
3-There are some factors affecting incinerator, what are
they?
4-Describe the process of using some factors to use
incinerator efficiently?
5-Do a selection of appropriate location of an incinerator?
6-Determine the amount of air required for complete
combustion of 1000 kg of a waste having chemical
composition as C60H95O40N. Determine also the energy
content for this type of waste
7-Find approximate chemical formula of the organic
component of the sample composition of a solid waste as
set out in the following table. Use chemical composition
obtained to estimate energy content of this solid waste.

70
References
1-Haghi, A. K. Waste Management: Research advance to
convert waste to wealth, Nova Science Publishers, Inc.
2011.
2-Willliams, Paul T. Waste Treatment and Disposal, 2nd
edition, by John Wiley & Sons, Ltd 2005.
waste Management, CBS publisher, India,2009.
5-Hecklinger, R. S. “Combustion.” The Engineering
Handbook, CRC Press, Inc., Boca Raton, FL, 1996.

71
6-Takele Tadesse. Solid Waste management; lecture
notes, Produced in collaboration with the Ethiopia Public
Health Training Initiative, The Carter, 2004.
7-Clifford Jones, J. Thermal Processing of Waste, 1st
ed.,
2010.
8-Thispe S.S., Sheng C., Booty M.R., Magee R. S., Bozelle
J.W. Chemical makeup and physical evaluation of
synthetic fuel and methods and methods of heat content
evaluation for studies of MSW incineration, Fuel 81 211-
217, 2002.
9-Capehart, Barney L., Turner, Wayne C. and Kennedy,
William J. Guide to Energy Management, Fifth Edition,
The Fairmont Press 2006.
Further readings
1-Belgiorno, V., De Feo, G., Rocca, C. D. & Napoli, R.M.A.
Energy from gasification of solid wastes, Waste
Management 23, 1-15, 2003.
2-Autret, E., Berthier, F., Luszezanec, A. & Nicolas, F.
Incineration of municipal and assimilated wastes in France:
Assessment of latest energy and material recovery

72
performances, Journal of Hazardous Materials B139, 569-
574, 2007.
3-Institution of Mechanical Engineers. Energy from waste,
A wasted opportunity? United Kingdom, 2007.
4-Klein, A. Gasification: An alternative process for energy
recovery and disposal of Municipal Solid Wastes. MS
Thesis, Columbia University, 2002.
5-Niessen, W. Combustion and Incineration Processes,
Marcel Dekker Inc., 2002.
6-Radian International LLC. A Comparison of gasification
and incineration of hazardous wastes, DVN 99.803931.02,
Austin, Texas, 2000.
7-https://mpra.ub.uni-muenchen.de/71518/MPRA, Paper
No. 71518, posted 22 May 2016.

73
Chapter Four Landfills
4.1 Introduction
The Municipal Solid Waste MSW in the last step must be
disposed in an engineered landfill and never in open or
unsanitary dumps. Sanitary landfills for municipal solid
waste (MSW) are essential for the disposal of waste and
unused residues from processing plants or other facilities
when they cannot be further processed or recycled.
Landfills could be the place for other process of waste
management such as biological or thermal treatments. So,
landfills will always be needed in many solid waste
management (SWM) systems. The rules direct that landfill
sites meet the specifications as given in table 4.1. Table1
4.1 describes in detail site selection, facilities at the site,
and specifications for landfilling, pollution prevention; water
quality and ambient air quality monitoring; planting at the
landfill site; closure of the landfill site; post closure care;
and special provisions for hilly areas.

74
Table 4.1. Criteria for identifying suitable land for landfill
sites1
Place Minimum siting distance
Habitation
Rivers, lakes, bodies of
water Non meandering
water (canal, drainage, and
so forth)
Highway or railway line
Coastal regulation zoning
Earthquake zone
Flood-prone area Airport 20
kilometers
500 meters
200 meters
30 meters
300 meters from center line
Landfill site not permitted
500 meters from fault line fracture
Landfill site not permitted
20 kilometers
Solid wastes that is disposed of in a landfill decomposes by
physical, chemical and biological processes2
. Physical
decomposition of a waste occurs mainly due to rinsing
action caused by the movement of water inside the landfill
and within the wastes. Chemical decomposition of wastes
includes hydrolysis, sorption, desorption, precipitation,
dissolution and ion exchange of waste components.
Biological decomposition of wastes occurs due to bacteria
effect. The organic materials occurring in waste can be
classified into broad biological groups represented by
proteins, carbohydrates and lipids or fats. Carbohydrates
are by far the major component of biodegradable wastes
and include cellulose, starch and sugars. Proteins are large

75
complex organic materials composed of hundreds or
thousands of amino acids groups. Lipids or fats are
materials containing fatty acids. Accordingly, landfill could
be considered as a biochemical reactor from another view.
The major advantage associated with landfilling of wastes
is the low cost of landfill compared with other disposal
options and the fact that a wide variety of wastes are
suitable for landfill. As it was referred to that all the wastes
treatments finally, they find their way to landfills. For
example, incineration bottom and fly ashes are disposed of
in landfill sites. The collection and utilization of landfill gas
as a fuel for energy generation is also an advantage.
However3
, landfill achieves a lower conversion of the
wastes into energy with about one-third less energy
recovery per ton from landfill gas than incineration. This is
mainly due to the conversion of the organic materials in the
waste into non-combustible gases and leachate and
general losses from the system. Increasingly, there is an
emphasis on regarding the modern landfill as a fully
designed and engineered process with high standards of
management. There are some expected problems from
landfills that lacks modern engineering construction such
as the feasibility of gas explosion, pollution due to leakage

76
of gases, leakage of leachate, bacterial growth…etc. These
draw backs are magnified in their effects if they are located
near the inhabitants.
Although many of the processes thought to occur within
landfill have not been proven, the presence of predicted
intermediate products and end products of degradation,
together with the presence of relevant enzymes, lead us to
conclude that the degradation of organic wastes in the
landfill environment is similar to the degradation of organic
materials in other anaerobic environments. There are three
stages of decomposition of waste inside landfill2
:
1. aerobic decomposition.
2. facultative or non-methanogenic
3. anaerobic decomposition
Aerobic decomposition of wastes is caused by the
acetogenic-aerobic microorganisms, this is the first stage of
decomposition which starts soon after the wastes are put in
the landfill. This type of decomposition is concentrated near
the surface of the landfill due to increased concentration of
oxygen near at that site. It is expected that some of the

77
reactions deeper are started as long as oxygen is available
and they will stop with oxygen depletion.
Biodegradable fraction + oxygen (with microorganism)
→partially biodegradable material+CO2+H2O+heat.
Therefore, the temperature of the landfill increases, CO2
concentration increases too which could lead to the
formation of acidic environment inside the landfill.
Facultative decomposition
As soon as the oxygen is depleted by the former method,
facultative microorganisms become dominant initiating the
second level or the facultative (or non-methanogenic)
decomposition. This stage produces high concentrations of
volatile fatty acids VFA, ammonia, hydrogen and carbon
dioxide.
Biodegradable fraction + oxygen (with facultative
microorganism)→ partially biodegradable material +CO2
+ H2O
As can be detected from above reaction CO2 is still
evolved and the leachate will become more acidic (5.5-
6.5)2
.

78
Anaerobic Decomposition
Under this stage the methanogenic bacteria become
active giving methane, carbon dioxide and water. This
process is slow but it lasts for many years. The
generated VFA earlier will be consumed by
methanogenic bacteria to give methane and CO2 such
as;
4H2+CO2=CH4+2H2O
VFA→CO2+CH4
In this stage by consumption of organic acids, the pH value
increases which leads to make the leachate less
aggressive. Nitrogen and hydrogen sulphide gases are
also could be available due to denitrification caused by the
microbial action and sulfate reducing bacteria for the two
gases respectively. The methane quantity generated is
affected by several parameters, such as, pH, temperature,
the level of compactness. For best yield of gas, a
temperature of 30-350
C and pH of 6.5-7.5 are typical and a
period of about six months to several years. Figure 4.1
shows a generalized steps of biodegradation process3
.

79
Figure 4.1. Biodegradation steps3

80
4.2 Types and components of landfills
Depending on the land used for landfill and the methods for
waste disposals, landfills are classified into2
:
1. Trench Landfills. This type of landfills has a wide use
in wastes disposals where in this type the wastes are
deposited inside a trench under the normal level of
the ground (figure 4.2). The sides and bases of these
landfills are lined to prevent leakage.
Figure 4.2. Trench landfill
2. Area landfills. This type of landfills are held on the
surface of the ground, figure 4.3. By this type, the
wastes are deposited on the ground and then buried
or covered by soil or suitable material.

81
Figure 4.3. Area landfills
3. Slope landfills. This type is erected in the hill areas
and in an angle of about 30-350
C as can be seen by
figure 4.4.
Figure 4.4. Slope landfills

82
4.3 Classification of landfill sites
The Regulations classify landfills into three types:
• sites for inert waste
• sites for non-hazardous waste
• sites for hazardous waste.
It is an offence to landfill waste in the wrong type of site.
The effect of this was to outlaw co-disposal, i.e. the
landfilling of hazardous industrial waste mixed with
biodegradable non-hazardous waste.
4.4 Factors affecting degradation inside landfills
There are some factors affecting the degradations of the
landfill’s components, such as:
 Characteristics of site. Landfill sites with waste
depths exceeding 5m tend to develop anaerobic
conditions and greater quantities of landfill gas.
Less than 5 m depth creates aerobic conditions
which allows oxygen to penetrate and produces
lower quantity of gas. Covering the landfill
contributes to create anaerobic conditions, hence
gas production. Also, rapid covering of the waste
will reduce the chance of rainfall increasing the

83
moisture content of the waste, which in turn
reduces the initial rate of biodegradation3
.
 Waste characteristics. Not all organics are
biodegradable and as it was stated earlier wastes
are composed of several components some of them
are not biodegradable, see Figure 4.54
.
Figure 4.5. Biodegradability of organic substances in
anaerobic digestion processes4
 Moisture content of the waste. The waste
biodegradation process requires moisture and is in
fact a major factor in determining the production of
landfill gas and leachate. Moisture are either inherent
with the wastes or due to humidity of the weather and
the rain fallings as well as the existence of the ground

84
water and the feasibility of some leakages. It was
found that the rate of biodegradation depends on the
moisture or the water and it increases with its
quantity.
 Temperature. The temperature range indicates the
type of microorganisms which are reactive. Initially
aerobic bacteria may increase the temperature up to
levels of 80°C if the waste is left well aerated as the
micro-organisms break down the waste to produce
methane and carbon dioxide. However, compacted
waste achieves lower temperatures due to the lower
availability of oxygen. The majority of landfill sites have
temperatures between 30 and 35°C during the main
landfill gas generation phase. If the site is cold then
significantly less gas is produced than at higher ambient
temperatures. Chaiampo et al.5
have monitored the
temperature changes with depth throughout a 20 m
deep municipal solid waste landfill in Italy. They showed
that the first 1-2 meters were in the temperature range
of 10–15°C, but the temperature increased to 35–40°C
at the 3–5 m depth and to 45–65°C in the 5-20 m depth
region. They equated the temperature regions with the

85
mesophilic bacteria in the 1-5 m range and thermophilic
bacteria in the deeper layers.
Acidity. The acidity of the landfill site influences the
activity of the various microorganisms and therefore
determines the rate of biodegradation. The pH of a
typical landfill site would initially be neutral, followed
by acidic phases, the pH falls to as low as 4 when
organic acids are produced from waste degradation
by the acetogenic micro-organisms. The resultant
organic acids provide the nutrients for the
methanogenic bacteria and as the acids are
consumed, the pH rises. The methanogenic bacteria
are most active in the pH range 6.8–7.5, if the pH
rises or falls outside this optimum range, then gas
production is significantly reduced. The formation of
organic acids and a drop in pH is an essential step3
in the waste biodegradation process, in that the
organic acids provide the nutrients for the main gas
generation phase IV micro-organisms, the
methanogens.

86
4.5 Landfills Components
Landfill site is composed of several elements, such as2
:
1. Cell. Deposition of wastes in one operational period is
termed cell. This period could be one day, therefore, the
received quantity of wastes defines the cell.
2. Daily cover. Waste material with a daily cover of soil in
thickness2
of 15-30 cm. Other materials could also be used
such as yard or composts. The cover material prevents
surface run off from entering into the wastes so as to
reduce the leachate formation. This has some advantages
in preventing odors, birds menace, disease spreads and
isolation the danger if for example fire is ignited as well as
the aesthetic view.
3. Lift: A 'lift' is the height of cells. Usually lifts are provided
in a landfill. Height of each Lift varies from 2 to 4m,
depending upon the cell volume.
4. Bench: A 'Bench' is provided in the above ground
landfills when the height of wastes deposited is more than
10 to 20m. lt is provided after each lift or after every
alternate lift and it increases the stability of the landfill
slope, Benches also facilitate surface drainage.

87
5. Leachate Collection System: Leachate' is produced
when surface water infiltrates into a landfill. The water
squeezed out from the wastes during its compaction and
consolidation also mixes with the leachate. It carries
numerous contaminants in it. Leachate must be carefully
collected through a suitably designed leachate collection
system. It should be treated before its release on the
ground or to sewage system.2
6. No confined gas can be emitted from landfill, see table
4.1. For the case of energy production or using in industry,
these gases have to be exploited by designing a system to
transport these gases to other uses. Environmental
considerations are very important because such gases can
exceeds their safe limits and either auto ignited or burned6
.
Table 4.1. Typical components of landfill gas6
Component Percent (volume basis)
Methane 45-65
Carbon dioxide 40-60
Nitrogen 2-5
Oxygen -1
Sulfides 0-1
Ammonia -1
Hydrogen 0-0.2
Carbon monoxide 0-0.2
Trace constituents 0.01-0.64

88
7. Final cover. When the landfill if full to its capacity, the
cover is needed, it could comprise the gas collector,
impermeable liner…etc. as well as showing the aesthetic
side of the landfill.
4.6 Landfill engineering
There are some design steps that are necessary to erect
landfill besides to that mentioned early. Most modern
landfills are now designed as containment landfills and
therefore the major design considerations relate to the
design of the containment system, this may vary according
to local and national policy and according to the landfill
location6
. Some countries strategies give the pollution of
the ground water much attention and knowing the sites for
the ground water and making maps for these sites for
future information in order to check the possibility of finding
the suitable landfill site. The general layout of a landfill
facility varies from site to sit. Figure 4.5 shows the typical
suggested plan for landfill. For any landfill, there are some
requirement in selection of site;
1. It must be close to the roads.

89
2. Security facilities to prevent any robberies or to prevent
unauthorized persons.
3. It must contain a weight bridge for daily weighing the
wastes.
4. There must be gas storage facilities.
5. There must be a laboratory for analyzing and checking
the landfill working regularly.
6. It must be provided with a unit for treatment, circulation
the leachate or to dispose of it.
7. It must be provided with all facilities that enables the
staff to repair, maintain equipment and the landfill.
4.7 Landfill liners
The design and engineering of landfill liners have received
much attention in recent years6
. Two fundamental types of
lining material are available natural (e.g. clay, shale) and
synthetic liners, also known as flexible membrane liners
(FMLs) or geo membranes. Combination of the two types
allows the construction of composite and multiple liners.
Natural liners such as clay have the advantage of inherent
attenuation capacity (a relatively high ion-exchange
capacity will inhibit, for example, the migration of heavy

90
metals), they are relatively stable in the presence of a wide
range of organic and inorganic compounds but they are
more permeable than FMLs. Conversely, FMLs have little
or no inherent attenuation capacity, are sensitive to organic
solvents, but are relatively impermeable7
Figure 4.5. Plan for layout of landfill
For much of the developed world6
, the simple composite
liner is considered as the minimum requirement, while in
the USA and increasingly within Europe, multiple liner
systems in which multiple barriers with protective layers,
and monitoring layers are preferred. However, multiple-
layer systems do not necessarily provide enhanced
environmental protection. After loading with waste,

91
multiple-liner systems have been known to slip due to
sheer forces, with resultant failure of containment. There is
also considerable debate concerning the relative merits of
monitoring or drainage layers; it can be argued that this
facility allows the recognition of containment failure and
remedial action to be taken before serious pollution occurs.
Table 4.2 outline lining performance6
.
Table 4.2. Performance of landfill lining6
Type of
liner
Best case Average case Worst case
Geo
membrane
alone
Compacted
soil alone
Composite
2500 (2holes ha-1)
115
(K=10-10m s-1)
0.8 (2holes ha-1,
k=10-1 m s-1
Poor contact)
25000
(20holes ha-1)
1150
(k=10-10 m s-1)
47
(20 holes ha-1
k= 10-9 m s-1
Poor contact)
75000
(60 holes ha-1)
11500
(k=10-10 m s-1)
770
(60 holes ha-1
k = 10-8 m s -1
Poor contact)
K is the coefficient of permeability
4.8 Compaction of wastes
After filling the cell with the waste by any suitable machine,
compaction process is started where leveling and
compaction to about 30-50 cm is done. This process of
compaction should be continued till getting the required
density. Subsequent compaction can also be achieved
through plying the trucks over completed cells2
.

92
4.9 Leachate management
There are several means for treating leachate such as
aerated lagoon, the rotating biological contractor, air
stripping, and reed beds. The continuing debate in leachate
management is whether or not to add water to sites or to
allow water infiltration. In the US, there is an approach
called” dry tomb” in which the design and management of
landfills must be in such a way as to minimize liquid
infiltration into the waste. This principle is contrary to that
engendered by the sustainable landfill and fail safe landfill,
in that with the dry tomb approach a final storage quality
waste will not be produced, and there will always remain
future pollution potential. While it may be possible to
ensure effective containment and capping in the short-term
(measured in tens of years), ultimate long-term failure
(measured in tens or hundreds of years) of lining and
capping systems must be anticipated. The arguments for
sustainable landfill design with moisture control are
considerably stronger6
.

93
4.10 Advantages of bioreactor landfill
If bioreactor landfill is compared to the old one “dry tomb”
the following can be seen:
1-the time of treatment is shorter, years vs. decades.
2-the toxicity is lower due to action of aerobic and
anaerobic conditions.
3-the produced land fill gas is increased compared to the
old landfill.
4-due to increase of the waste density, a 15-30 % of landfill
space is gained8
.
Questions
1-What is the difference between landfill and incinerator?
2-What criteria should be taken to choose landfill over
others means used in waste treatments?
3-Describe the auto ignition possibility of some emitted
gases and what solution you give to solve this problem?
4-What are the advantages-disadvantages in using landfill.
5-Does landfill affect global warming?
6-By using a chemical reaction expression for aerobic
digestion, can you calculate the emitted gases by

94
stoichiometric balances like any other chemical reaction?
Comment
7-Is landfill suitable to your country compared to other
means of waste managements?
References
1-Da Zhu, P. U. Asnani, Chris Zurbrügg, Sebastian
Anapolsky and Shyamala Mani. Improving Municipal
Solid Waste Management in India, The International
Bank for Reconstruction and Development / The World
Bank 1818 H Street, NW 2008.
3-Williams, Paul T. Waste Treatment and Disposal, 2nd
edition, by John Wiley & Sons, Ltd 2005.
4-Karagiannidis Avraam. Waste to Energy, Springer-Verlag
London Limited 2012.
5-Chaiampo F., Conti R. and Cometto D., Morphological
Characterization of MSW Landfills, Resources,
Conservation and Recycling, 17, 37–45, 1996.

95
6-Hester R.E. and Harrison R.M. Waste Treatment and
Disposal, the Royal Society of Chemistry 1995.
7-P.J. McKendry. Proceedings of the Fourth International
Landfill Symposium, Sardinia, 1993.
8-Dubois Edgard and Mercier Arthur. Energy Recovery,
Nova Science Publishers, Inc. 2009.
Further readings
1-Bagchi A. Design Construction and Monitoring of Landfill.
John Wiley & Sons Ltd, New York, 1994.
2-Blakey N., Archer D. and Reynolds P. Bioreactor landfill:
a microbiological review. In, Christensen T.H., Cossu R.
and Stegmann R. (Eds.), Sardinia 95, Fifth International
Landfill Symposium (Cagliari, Sardinia, October 1995),
CISA-Environmental Sanitary Engineering Centre,
Cagliari, Sardinia, 1995.
3-Brown K.A. and Maunder D.H. Exploitation of landfill
gas: A UK perspective, Water Science and Technology,
30, 1994.

96
4-Christensen T.H., Cossu R. and Stegmann R. (a).
Landfilling of Waste: Barriers. E & FN Spon, London,
1996.
5-Christensen T.H., Kjeldsen P. and Lindhardt B. (b). Gas
generating processes in landfills. In, Landfilling of
Waste: Biogas, Christensen T.H., Cossu R. and
Stegman R. (Eds.), E & FN Spon, London, 1996.
7-Diaz L.F. and Savage G.M. Developing Landfill. Waste
Management World, International Solid Waste
Association, Copenhagen, July–August, 2002.
8-Yang Rong, Xu Zengguang and Chai Junrui. A Review of
Characteristics of Landfilled Municipal Solid Waste in
Several Countries: Physical Composition, Unit Weight,
and Permeability Coefficient, Pol. J. Environ. Stud. Vol.
27, No. 6 (2018).

97
Chapter Five Landfill Gas Characteristics
Landfill gas LFG is composed mainly of methane , carbon
dioxide and some volatile organics or hazardous air
pollutants. The formation of LFG is taking place in early
stages and at higher rate than the traditional landfill. It is
interesting to say that the LFG formation period is short
because the degradation process is decreased due to
depletion of the wastes vs. time progressing. Generally, the
produced quantity of LFG is more than the old landfill
configuration. The usage of LFG produced by the new and
old landfills in the energy sector is about 10% of potential
use1
. The US Department of Energy estimates that if the
controlled bioreactor technology was applied to 50 percent
of the waste currently being landfilled, it could provide over
270 billion cubic feet of methane a year, which is
equivalent to one percent of US electrical needs.

98
5.1 Landfill gas characteristics and composition
Table 5.1 below gives the composition of the LFG1
.
Table 5.1. Characteristics and identity of the LFG
Constituent Relative
Specific
Gravity
Concentrati
on Landfill
Gas
Notes
Air
1
NA Forms explosive
mixture with methane.
Methane
0.554
40-70% Explosive: LEL 5% in
air: UEL 15% in air.
Carbon Dioxide
1.520
30-60% Forms weak acid.
Asphyxia
Hydrogen Sulfide
1.19
800ppm Forms strong acid
Toxic: PEL= 10, STEL =
15
Water Vapor
0.62
100%
saturated
Forms acids with
hydrogen sulfide and
carbon dioxide
Benzene
2.8
30 ppm Flammable
Toxic: PEL 1.0 ppm
STEL 5 ppm
Toluene
3.1
300 ppm Toxic: PEL 100 ppm
STEL 150 ppm
Organic Acids GT2 Traces Odorous
Organo sulphur
Compounds
GT1.5 50 ppm Odorous
LEL= lower explosive limit; UEL = upper explosive limit; STEL = short-term-
exposure limit; PEL =permissible exposure limit.1,2
During the methanogenic stage, LFG can be expected to
have a heating value of 18.6 MJ/m3
under good conditions.
This value represents 50% of that of natural gas1
. It must
be mentioned that the heating value is function of many

99
factors such as the waste age, the conditions in the landfill,
its type and others.
Returning back to table 5.1, there are large number of risks
associated with the escape of landfill gas, including health
risks, explosion risks, and risks associated with
atmospheric pollution. The question arises, what is
happening to these gases when the landfill is closed?
Upon3
closure and capping of a landfill, the primary route of
landfill gas migration (via the waste surface) is
considerably restricted. Although it has been shown that
gas can migrate through clay relatively easily, the landfill
cap creates a barrier to hinder the escape of the gases but
there will be an increasing pressure within the waste which
push the gas to escape from the least area of resistance.
The migration of gas beyond landfill boundaries has been
the cause of a number of hazardous4
(explosion-related)
incidents, one of the most notable within the UK resulting in
destruction of a bungalow at Loscoe in Derbyshire5
.

100
5.2 Composition of LFG
Microbiological effect of the waste has the main
responsibility to produce LFG, methane, carbon dioxide
and other traces. Table 5.2 shows the compositions of the
LFG.
Table 5.2. Composition of LFG1
Component Percent (volume basis)
Methane 45-65
Carbon dioxide 40-60
Nitrogen 2-5
Oxygen -1
Sulfides 0-1
Ammonia -1
Hydrogen 0-0.2
Carbone monoxide 0-0.2
Trace constituents 0.01-0.6
The type of bacteria and the availability of a suitable
substrate affect the quality of LFG. Methane represents
about 55% of LFG while 40-45% of LFG is carbon dioxide.
Methane is the most reduced organic molecule. In other
words, no further conversions to simpler organic molecules
are possible once methane has been produced. It is
produced as an end product of anaerobic metabolism.
Over 550 trace gases have been identified to date, and
doubtless more will yet be discovered. The trace

101
components have chemical or physical properties that
differ significantly from the bulk gases1
. Also, it is known
that some of these trace components, when present above
threshold concentrations, cause physiological effects and
thus have potential health impacts.
The quantity of liberated or formed methane can be found
by two methods; the first method is theoretical one based
on the stoichiometry and the balanced chemical reaction
assuming that the conversion is 100% which is not straight
forward all the time. Assuming that the biodegradable
waste material is of the form CaHbOcNdSe then by the action
of microbiology degradation, the following reaction is
applicable:
CaHbOcNdSe+fH2O=gCH4+hCO2+yNH3+xH2S or in
another form
…..Buswell equation.
Using this method, the estimated yield of the landfill gas is
440 L/kg wet waste with a composition of 53% methane
and 46% CO26
. El-Fadel et al.7
reported based on the

102
stoichiometric method that the estimated methane yield is
in the range of 220-270 L/kg dry waste after complete
decomposition. In the experimental approach1
, the landfill
gas yield can be obtained from laboratory scale studies.
The amount of biogas produced by biodegradation of MSW
can be measured in the laboratory. The biodegradation of
MSW can be controlled and enhanced by manipulating
environmental factors such as pH, temperature, moisture,
nutrients, etc. The range of methane yield from lab scale
studies varies from no generation to 107 L CH4/kg dry
waste.
Example 5.1
Given the following formula C6H9.6O3.5N0.28S0.2 which
represents a biodegradable food as a solid waste.
Calculate the moles of product and their percent
assuming that the conversion is 100%?
Solution
By direct reaction in presence of bio effects we can write;
C6H9.6O3.5N0.28 S0.2+f H2O= gCH4+hCO2+yNH3+xH2S
To find the unknown quantities, a material balance will be

103
used and as follows;
C material balance
6=g+h …. 1
O material balance
9.6(3)+f=2h ….2
N material balance
0.28=y ……3
H material balance
9.6+2F=4g+3y+2x ……4
S material balance
0.2=x …….5
Solving these five equations will give g, h, f while y and x
are easily obtained.
This will be left to the reader as a training as well as using
another route using Buswell equation.
Example 5.2
Estimate the theoretical volume of gas that will be
generated in a sanitary landfill by anaerobic digestion of

104
1000 kg of MSW having approximate chemical formula
for its organic portion as C90H150O80N.
Solution
It is assumed complete conversion of biodegradable
organic waste to CO2 and CH4 by anaerobic digestion in
the landfill will take place. The total theoretical volume of
gas may be estimated using Buswell equation:
CaHbOcNd+(4a-b-2c+3d)/4)H2O= (4a-b-2c-3d)/8 CH4+(4a-
b-2c+3d)/8 CO2+dNH3
For the given waste’s composition, a=90, b = 150, c= 80,
d= 1, we can obtain therefore,
C90H150O80N+13.25H2O=43375CH4+46.652CO2+NH3
using molecular weight for each substance, i.e., for the
above waste formula it is 2524 kg/kmol so:
From 1000 Kg of wastes therefore, (i) The weight of
methane (CH4) gas that will be produced out of 1000 Kg
of waste (694/2524) *1000=274.96 Kg also the weight of
Co2 is 812.79kg /1000 kg of waste

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