ENERGY AND CO2 EMISSION EVALUATION OF CONCRETE WASTE
POORIA RASHVAND
This project report is submitted as a partial fulfillment
Of the requirement for the award of the degree of
Master of Science (Construction Management)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
NOVEMBER 2009
iii
ACKNOWLEDGEMENT
I would like to express my deep gratitude for the constant guidance and
support from my supervisor, Dr Khairulzan Yahya, during the course of my graduate
study. His insight, suggestions and criticism contributed in large measure to the
success of this research. My thanks also goes to Mr Mukhtar Affandi abd ghani,
project manager of one of construction sites under my investigation and also Faculty
of Civil Engineering (FKA) for their support to conduct this work. Finally, my
greatest thanks and appreciation go to my family. A thousand thanks to my parents. I
thank my father for his unfailing wisdom and guidance, my mother for her caring
and strength, my brother, Payam for his friendship.
iv
ABSTRACT
A significant amount of solid wastes produced every year from construction
and demolition activities, and had caused significant pollution to the environment
and risen public concern. Therefore, the minimization of construction wastes has
become a critical issue in construction industry Concrete is the most commonly used
construction material in the world, and after water is the second most consumed
product on the planet. The huge popularity of concrete also carries environmental
costs, the most harmful of which is the high energy consumption and CO2 release
during the production. This paper investigates the amount of energy used and CO2
emission generated during the production of concrete. Furthermore to estimate the
total impact of both indicators based on concrete wasted generated on site. Data were
obtained through questionnaire survey and interview within the building construction
projects in U.T.M. These impact assessment were followed the life cycle assessment
(LCA) methodology. The results show that the production of the raw material and
the transports of the concrete are the main contributor to the total environmental load
. The highest impact value was generated during
the production of cement at
upstream level .the amount of energy used and CO2 emission by cement production
was about 70 percent of the total embodied energy and 95% of the carbon dioxide
emissions of concrete production and
Within the transportation operations, the
transportation of concrete is the largest contributor equal to 25% to 28% the
production of concrete and on the other hand 12% to 14% for CO2 emission.
v
ABSTRAK
Jumlah sisa pepejal daripada kerja pembinaan bangunan menyebabkan
pencemaran alam sekitar dan meningkatkan keprihatinan masyarakat awam akan
perkara ini. Oleh yang demikian, pengurangan akan sisa tersebut menjadi isu yang
kritikal dalam industri pembinaan. Konkrit merupakan bahan yang digunakan dalam
kerja pembinaan. Penggunaannya yang berlebihan menyebabkan kesan kepada
persekitaran iaitu pembebasan gas CO2 semasa proses penghasilannya. Kajian ini
menyiasat tenaga yang digunakan dan pembebasan gas CO2 semasa menghasilkan
konkrit. Kajian ini juga menganggar kesan bagi kedua-dua perkara tersebut. Data
diperolehi dengan dapatan soal selidik dan temu bual yang dilakukan di sekitar
projek pembinaan di UTM. Seterusnya penilaian kitar tenaga (LCA), di jalankan dan
keputusan mendapati penghasilan bahan mentah dan pengangkutan konkrit
merupakan penyumbang utama kepada beban persekitaran. Kesan tertinggi
diperolehi semasa penghasilan simen pada peringkat akhir. Jumlah tenaga yang
digunakan dan pembebasan gas CO2 oleh penghasilan simen ialah 70 peratus
daripada jumlah sebenar tenaga yang digunakan dan 95 % pembebasan gas karbon
dioksida. Dalam tempoh operasi penghantaran, iannya merupakan penyumbang
terbesar iaitu 25% ke 28 % bagi penghasilan konkrit dan 12 % ke 14 % bagi
pembebasan gas CO2.
vi
TABLE OF CONTENTS
CHAPTER
1.
2.
TITLE
PAGE
TITLE
i
DECLARATION
ii
ACKNOWLEDGMENT
iii
ABSTRACT
iv
ABSTRAK
v
TABLE OF CONTENTS
vi
LIST OF TABLES
ix
LIST OF FIGURES
xii
DIFINITIONS
xiii
INTRODUCTION
1.1 Introduction
1
1.2 Back ground of the study
2
1.3
3
Problem statement
1.4 Aim and Objectives of the study
4
1.5 Scope of the study
5
LITERATURE REVIEW
2.1 Construction and Demolition Waste
6
2.2 Environmental impact of concrete elements
8
2.2.1
Cement
12
2.2.1.1 Energy use in cement production
12
2.2.1.2 Air Emission from Cement production
13
vii
2.2.2 Aggregate
14
2.3 Concrete production
16
2.4 Environmental Impact of Transport Distance
17
2.5 Calculating the Concrete Waste
19
2.6 Recycling and land filling
19
2.7 Current Situation of Construction and
Demolition Waste in Asia
2.8 Practice on C & D waste management in Malaysia
3.
26
2.8.1
Construction sector’s waste profile
26
2.8.2
Policies and laws
27
2.8.3
Practices
28
2.8.4
Waste Management Stakeholders
28
2.8.5
Waste Management Technologies
29
METHODOLOGY
3.1 Introduction
30
3.2 Inventory result
31
3.3 System boundary
33
3.4 Data Collection
34
3.4.1
4.
22
Questionnaire survey
34
3.4.1.1 Questionnaire structure
34
3.5 Data analysis
35
3.6 Stages of the study
35
ANALYSIS AND DISCUSSION
4.1 Concrete waste
4.1.1
Concrete Slabs, Walls, Beams, and Columns
39
40
4.2 Assumptions
43
4.3 Concrete production
43
4.4 Cement Energy Demand
44
4.5 Aggregate Energy Demand
45
4.6 Energy for Wasted Cement and Aggregate
46
4.7 CO2 Emission
47
4.8 Admixture
49
viii
5.
4.9 Transportation
51
4.10 Transportation concrete to the site from concrete plant
52
4.11 Disposal Options
62
4.11.1 Recycling
63
4.11.2 Land filling
78
CONCLUSION
5.1 Introduction
79
5.2 Conclusion
79
5.3 Recommendation for future research
80
5.3.1
Concrete reabsorbs CO2
80
REFRENCES
82
APPENDICES A-B
88
ix
LIST OF TABLES
TABLE NO.
TITLE
PAGE
2.1
Typical Constitutes of Concrete
9
2.2
Main ingredients for the production of 1 kg cement
11
2.3
Energy demand in production of 1 Kg cement
13
2.4
Emissions to air by cement production
14
2.5
Energy demand and emissions generated in the production
15
of 1 kg gravel
2.6
Energy demand and emissions to air for the production
17
of 1 m3 of concrete
2.7
Process energy emissions calculations for recycled aggregate
2.8
Transportation energy emissions calculations
21
for recycled aggregate
22
2.9
Aggregate Recycling Emission Factor (MTCE/TON)
22
2.10
Amount of reused and recycled construction
waste materials on site
29
x
3.1
Vehicle Option
32
4.1
Cumulative quantity of ordering in construction no 1 (m3)
41
4.2
Different construction mixing design
44
4.3
Embodied Energy & CO2 Emission for One Cubic Meter of
56
Concrete Production(project 1)
4.4
Embodied Energy & CO2 Emission for Total Cubic Meter of
57
Concrete Production(project 1)
4.5
Embodied Energy & CO2 Emission for One Cubic Meter of
57
Concrete Production(project 2)
4.6
Embodied Energy & CO2 Emission for Total Cubic Meter of
58
Concrete Production (project 2)
4.7
Embodied Energy & CO2 Emission for One Cubic Meter of
58
Concrete Production (project 3)
4.8
Embodied Energy & CO2 Emission for Total Cubic Meter of
59
Concrete Production (project 3)
4.9
Embodied Energy & CO2 Emission for Total Cubic Meter of
61
Waste Concrete Production (project 1)
4.10
Embodied Energy & CO2 Emission for Total Cubic Meter of
61
Waste Concrete Production (project 2)
4.11
Embodied Energy & CO2 Emission for Total Cubic Meter of
62
Waste Concrete Production (project 3)
xi
4.12
Process Energy Data for the Production of
One Ton
of Virgin Aggregate
4.13
Transportation Energy Consumption, million Btu/ton-
4.14
Process energy emission calculation for
64
mile
Virgin aggregate (EIA, 2001)
4.15
4.17
67
Transportation Energy Emission Calculation for
Virgin Aggregate
4.16
65
68
Process Energy Emissions Calculations for Recycled
Aggregate (EIA2001)
71
Transportation Energy Emissions Calculations for Recycled
72
Aggregate (EIA2001)
4.18
Comparing recycling and virgin aggregate (84m3)
74
4.19
Comparing recycling and virgin aggregate (20m3)
75
4.20
Comparing recycling and virgin aggregate (20m3)
76
xii
LIST OF FIGURES
FIGURE NO.
TITLE
2.1
Cement life cycle
2.2
Difference in environmental impact from cement
PAGE
10
production between year 1995and 2005
12
2.3
Different distance in EP impact
18
2.4
C&D Waste Generation in Million Tons
23
2.5
Trend of National Account of Construction in Asia
24
2.6
Composition of total waste generation
27
3.1
General Flowchart for the concrete life cycle
33
4.1
Energy comparison between Virgin and Recycled Aggregate
77
4.2
CO2 emission between Virgin and Recycled aggregate
77
xiii
DEFINITIONS
Embodied energy: The sum of the energy used to manufacture a product from
cradle up to the product is ready to be delivered from the producer and of its
feedstock.
Emission: Release or discharge of any substances, effluents or pollutants into the
environment.
Environmental impact: A change to the environment, whether adverse or
beneficial, and the associated consequences for both humans and other ecosystem
components caused directly by the activities of product or service development and
production, wholly or partially resulting from an organization’s activities, products,
or services, or from human activities in general
Recycling: Recycling is used as a generic term for different forms of recycling. The
here included forms are; reuse, material recycling and combustion with heat
recovery.
Reuse: The material is used for about the same purpose as initially. Reuse might
imply upgrading or some renovation.
Recycling Potential: The environmental impact from production of that material the
recycled material will be a substitute for less the environmental impact from the
recycling processes and connected transport. In this thesis the environmental impact
is limited to embodied energy and use of resources. The recycling potential can
therefore shortly be described as a way to express so much of the embodied energy
and natural resources which, through recycling could be conserved.
CHAPTER I
INTRODUCTION
1.1
Introductions
The construction industry plays a vital role in meeting the needs of its society
and enhancing its quality of life. The industry remains as a major economic sector, thus
the pollution generated from construction activities continuously presents a major
challenge to implement environmental management in practice. The investigations
demonstrated that construction business is a large contributor to waste generation.
Environmental and human health impacts of materials are a hidden cost of our
built environment. Impacts during manufacture, transport, installation, use, and disposal
of construction materials can be significant, yet often invisible. A broad and complex
web of environmental and human health impacts occurs for each of the materials and
products used in any built landscape, a web that extends far beyond any project site.
Construction materials and products can be manufactured hundreds, even thousands, of
miles from a project site, affecting ecosystems at the extraction and manufacturing
2
locations, but unseen from the project location. Likewise, extraction of raw materials for
these products can occur far from the point of manufacture, affecting that local
environment. Transportation throughout all phases consumes fuel and contributes
pollutants to the atmosphere. Disposal of manufacturing waste and used construction
materials will affect still another environment. These impacts are “invisible” because
they are likely remote from the site under construction and the designer’s locale.
Parallel to rapid economic growth and urbanization in Asia, environmental
impacts from construction and demolition (C&D) waste are increasingly becoming a
major issue in urban waste management. C&D waste management in developing
countries in the Asian region is relatively undeveloped and emerging. Environmental
issues such as increase in volume and type of waste, resource depletion, shortage of
landfill and illegal dumping, among others are evident in the region. Furthermore, the
Asian countries have limited or no available data on C&D waste and the management
aspects, particularly with regards to their C&D waste generation and composition;
practices and policy, key actors and stakeholders’ participation. (Asian Institute of
Technology,2008)
1.2
Background of the study
Concrete is the most commonly used construction material in the world, and
after water is the second most consumed product on the planet. Each year worldwide the
concrete industry uses 1.6 billion tons of cement, 10 billion tons of rock and sand, and 1
billion tons of water. Every ton of cement produced requires 1.5 tons of limestone and
fossil fuel energy inputs (Mehta 2002). The huge popularity of concrete also carries
environmental costs, the most harmful of which is the high energy consumption and
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3
CO2 release during the production of Portland cement. While the resources for
aggregate and cement are considered abundant, they are limited in some areas, and more
importantly, mining and extraction of the raw materials results in habitat destruction,
and air and water pollution. (Mehta 1998).
Several measures can be taken to minimize the environmental and human health
impacts of concrete and some can result in improved performance and durability of the
concrete as well. Perhaps the most important strategy is to minimize the use of Portland
cement by substituting industrial by-products (e.g., fly ash, ground granulated blast
furnace slag, or silica fume) or other cementitious materials for a portion of the mix.
Recycled materials substituted for both coarse and fine natural aggregates will minimize
use of nonrenewable materials and the environmental impacts of their excavation.
(Mehta 2002)
1.3
Problem statement
In Malaysia, the construction industry generates a lot of construction waste
which cause significant impacts on the environment and increasing public
concern(Begum et al., 2005). Thus, the minimization of construction waste has become
a pressing issue. The source of construction waste at the project site includes materials
such as soil and sand, brick and blocks, concrete and aggregate, wood, metal products,
roofing materials, plastic materials and packaging of products. Concrete and aggregate is
the largest component with 65.8% of total waste generation (Begum et al., 2005). CO2
production has been directly linked to climate change and global warming and
governments have set specific targets to reduce national emissions. Production and
demolition of concrete in sites are of direct importance both in terms of the contribution
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4
to CO2 and energy. Environmental and human health impacts of materials are a hidden
cost of our built environment. Impacts during manufacture, transport, installation, use,
and disposal of construction materials can be significant, yet often invisible
1.4
Aim and Objectives
The aim of this research is estimate the impact of concrete waste in construction
sites in term of energy consumption and CO2 emission:
i.
To estimate the amount of energy used and CO2 emission for production of
concrete in addition with transportation to the site.
ii.
To determine the amount of concrete waste in construction sites.
iii.
To estimate the total energy and CO2 emission based on the different weight of
concrete waste on site.
iv.
`
To evaluate the disposal option of concrete waste.
5
1.5
Scope of the Study
The scope of this study is as the following:
i.
Areas of study were within the building construction in U.T.M
ii.
The impact indicator used in the study were limited to the energy usage and CO2
emission only. The evaluation of total impact will be based on the percentage of
concrete wastage on sites.
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6
CHAPTER II
LITERATURE REVIEW
2.1
Construction and Demolition Waste
Environmental life-cycle assessment is a “cradle-to-grave,” systems approach for
measuring environmental performance. The approach is based on the belief that all
stages in the life of a product generate environmental impacts and must therefore be
analyzed, including raw materials acquisition, product manufacture, transportation,
installation, operation and maintenance, and ultimately recycling and waste
management. (Mehta 2002).
Graham2003 described that construction activity is one of the major contributors
of CO2 emissions and other greenhouse gases to the atmosphere. Steel manufacture, for
example, is estimated to cause emission of approximately two tons of CO2 for every one
ton of steel produced, while cement manufacture causes approximately one ton of CO2
per ton of cement. Furthermore, four categories of environmental impact associated with
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7
construction activities include resource depletion; physical disruption; pollution; and
social and cultural effects (Graham, 2003).
The construction industry is seen as one industry which has direct relation with
development and where environmentally sound results should be achieved. It involves
preventing waste and stimulating the reclamation of construction and demolition waste,
which entail a reduction in the volume of waste produced during building activities, the
separation of waste materials and reducing pollutive emission into the environment
during production of building materials and the construction production process.(
Franklin Associates 1998).According to him, C&D waste is waste material produced in
the process of construction, renovation, or demolition of structures. These structures
include buildings of all types in residential and nonresidential as well as roads and
bridges. Components of C&D waste are typically concrete, asphalt, wood, metals,
gypsum wallboard, and roofing. In addition, construction industry is one of the major
contributors to the environmental impacts, which are typically classified as air pollution,
waste pollution, noise pollution and water pollution. Open burning of C&D waste at
construction sites is practiced in many rural areas as well as in many urban areas. The
same issue can be observed perhaps in most countries in Asia where the practice of open
burning is very evident. Moreover, aside from open burning, the most common
management practice for C&D waste is land filling, where the waste is dumped in
municipal solid waste (MSW) landfills, and on illegal dumping sites.
Moavenzadeh as cited in Ofori (2000), noted that many government and
organization has been accepted to consider environmental issues in the context of
sustainable development. National and local governments and authorities in urban areas
have attempted to meet the demand for housing and services through increased
construction. However, lack of awareness of resource-efficient construction practices
has resulted in excessive use of natural resources and generation of large amounts of
construction waste that is rarely recycled.
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8
C&D is an important resource which has the capability for recycling and reusing,
so paying attention to this fact can be useful in order to reduce the waste which sent to
landfill.landfilling is not the reasonable disposal option based on environmental issue
such as increase in volume and type of waste, resource depletion, shortage of landfill
and illegal dumping, among others are evident in countries. Environmental issues In
Hong Kong SAR, Poon et al. (2004) reported that the waste generated by the building
and demolition of construction projects assumes a large proportion of environmental
waste. While in Malaysia, the construction industry generates a lot of construction waste
which cause significant impacts on the environment and increasing public concern in the
urban areas (Begum et al., 2006). Moreover, data is not readily available on the current
structure of construction waste flows by the source of generation, type of waste,
intermediate and final disposal and the amount of waste reduced at source, reused or
recycled on-site or off-site. Moreover, potentially hazardous materials may be found in
C&D waste, these include asbestos-based materials (e.g. asbestos-cement flat sheet,
asbestos-cement corrugated sheets), lead-based materials (e.g. lead-based paint),
materials used for construction such as damp-proofing chemicals, adhesives; mercurycontaining electrical equipments, toxic materials among others.
2.2
Environmental Impact of Concrete Elements
Approximately 3.7 million tons of concrete were used in Sweden in buildings,
roads and other constructions in 2004.1 This makes concrete one of the most common
building materials on the market. The main ingredients in concrete are aggregate (7080 %), cement (10-20 %) and water (7-9 %), and to enhance specific characteristics,
chemical admixtures (less than 1 %) are added.
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9
Table2.1: Typical Constitutes of Concrete(Source: US.PCA,2006)
Constituent
Average Percentage
Portland Cement
9.3
Fly ash
1.7
Coarse aggregate
41
Fine aggregate
26
Water
16
Air
6
2.2.1 Cement
Cement is a hydraulic binder, which hardens when it is mixed with water. the
main constituents of cement are limestone and clay. As shown in Fig 2.1 to produce
cement, the limestone and clay are ground together. This raw material, called raw meal,
is fed into a rotating kiln either wet or dry. Dry material is more often used since this is
more energy efficient, as a wet kiln uses twice as much energy. The temperature in the
kiln is approximately 1450 °C. (Burström, 2001)
The calcinations process begins when the material passes from the kiln to the
calcinatory. In this heating process CO2 is released from the limestone to produce
cement clinker. The clinker consists of a mineral residue containing calcium oxide
(CaO), alone or together with iron (Fe), aluminium (Al) or silicon (Si). The chemical
process is: CaCO3 + heat > CaO + CO2. Most of the energy used in cement production
is used in the calcinations process.
The last step in cement production is the grinding together of the cement clinker
and gypsum. Gypsum is added to prolong the binding of cement. Other material may be
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10
added the cement, for example, bauxite or sand, to establish the required quality of the
final product. After finishing and packaging, the cement is transported to cement depots.
(Johansson, 1994)
Mining
Limestone
Clay
Grinding
Depot
Clinker
Kiln & Calcinatory
Transport
Gypsum
Grinding
Cement
Other
Figure 2.1: Cement life cycle(U.S. Geological Survey 2007).
Portland cement is the key ingredient in concrete, binding the aggregates
together in a hard mass. However, it is also the ingredient in concrete that produces the
greatest environmental burden. In 2006, more than 2 billion tons of Portland cement
were consumed worldwide, with 131 million metric tons (MMT) consumed in the
United States. This is a 16% increase over 2002. Ninety-nine MMT of cement were
produced in the United States and 32 MMT were imported, primarily from Canada,
Thailand, China, and Venezuela (U.S. Geological Survey 2007).
Major raw materials for cement include limestone, cement rock/marl, shale, and
clay. These materials contain calcium oxide, silicon dioxide, aluminum oxide, and iron
oxide in varying contents. Because these contents vary, the mixture of raw materials
differs among cement plants and locations. Typical proportions of raw materials for 1 kg
of Portland cement are shown in the table 2.2 in the following page (Lippiatt 2000).
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11
Table 2.2 Main ingredients for the production of 1 kg cement(lippiatt,2000)
Ingredient
Amount (kg)
Limestone
1.4
Sand
70
Gypsum
30
Jeannette Sjunnesson in 2005, has studied about the cement production and he
tried to compare cement production in 1995 by his finding in 2005,so that his finding is
as following:
The comparison clearly shows that the environmental load from cement
production has decreased during the last ten years (Figure 2.2). The Global Warming
Potential (GWP) has changed least, with a reduction of approximately 6 % and the
POCP (Photochemical Oxidant Creation Potential is related to the potential for VOCs
and oxides of nitrogen to generate photochemical or summer smog. It is usually
expressed relative to the POCP classification factor for ethylene) has the highest
reduction, approximately 80 %. The reduction in GWP is mainly because of the
replacement of a part of the fossil fuels to alternative fuels. Much waste is used as fuels
in cement production. The reason for the large reduction in (POCP) is probably that the
incineration of fuel and the cleaning of emissions have improved over the ten-year
period. Emissions of HC are 1 % of the emissions in 1995. The reason for the decrease
in Acidification Potential (AP is a consequence of acids (and other compounds which
can be transformed into acids) being emitted to the atmosphere and subsequently
deposited in surface soils and water. Acidification Potential (AP) is based on the
contributions of SO2, NOx, HCl, NH3 and HF to the potential acid deposition in the form
of H+ (protons)). is a more effective sulphur removal in the production). There was five
times as much Sulfur Oxides (SOx) emission from cement production in 1995 as in
2005. The reduction in Eutrophication Potential (EP is defined as the potential of
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12
nutrients to cause over-fertilisation of water and soil which in turn can result in
increased growth of biomass) is due to lower emissions of Nitrogen Oxides (NOx), of
which today’s emission is only 1/3 of that in 1995. The comparison can be done since
the system boundaries of the both studies are approximately similar. (Jeannette
Sjunnesson LUNDS TEKNISKA HÖGSKOLA,2005)
120%
100%
80%
60%
1995
2005
40%
20%
0%
EP
Figure 2.2:
AP
POCP
Difference in environmental impact from cement production
between year 1995and 2005 (Vold & Rønning, 1995, Jeannette
Sjunnesson,2005)
2.2.1.1 Energy Use in Cement Production
Cement production is an energy-intensive process using primarily fossil fuel
sources. Cement composes about 10% of a typical concrete mix but accounts for 92% of
its energy demand. Cement production requires the preprocessing of large quantities of
raw materials in large kilns at high and sustained temperatures to produce clinker. An
average of almost 5 million Btus is used per ton of clinker. In 2004, the cement sector
consumed 422 trillion Btus of energy, almost 2% of total energy consumption by U.S.
manufacturing (US,PCA 2003).
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13
Table below illustrates the average breakdown of fuel sources from four cement
manufacturing processes. It also provides a weighted average with total energy of 4,798
kJ to produce one kilogram of cement (Medgar, Nisbet, and Van Geem 2007).
Table 2.3: Energy demand in production of 1 Kg cement (Stripple, 2001,LCI
Data).
Energy
Amount
Coal
1.9 MJ
Coke
0.51 MJ
Diesel
0.03 MJ
Car tires
0.42 MJ
Bone meal
0.01 MJ
Electricity
0.48 MJ
TOTAL
3.35 MJ
2.2.1.2 Air Emissions from Cement Production
Portland cement manufacturing include different emission such as carbon
dioxide (CO2), particulate matter, carbon monoxide (CO), sulfur oxides (SOx), nitrogen
oxides (NOx), total hydrocarbons, and hydrogen chloride (HCl). Emissions is different
from type of cement, compressive strength, and blended constituents. CO2 emissions.
Worldwide, the cement sector is responsible for about 5% of all man-made emissions of
CO2, the primary greenhouse gas that drives global climate change (Humphreys and
Mahasenan 2002).
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14
Table 2.4: Emissions to air by cement production (Stripple, 2001,LCI Data).
Emissions to air
Amount
CO2
0.71 kg
CO
2.7 mg
NOx
0.7g
SOx
0.09g
CH4
2.6g
HC
1.3mg
2.2.2 Aggregate
Aggregate is the highest ingredient in concrete by 60% and 75% of the volume.
Aggregates can be mined or manufactured. Some are by-products of industrial processes
or post-consumer waste products. Natural fine aggregates are usually quarried natural
sand and coarse aggregates are either quarried or manufactured from crushed stone.
Sand and gravel are typically dug or dredged from a pit, river, or lake bottom. They
usually require minimal processing. Crushed rock, a manufactured aggregate, is
produced by crushing and screening quarry rock or larger-size gravel (Lippiatt 2000).
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15
Table 2.5: LCI Data for Energy demand and emissions generated in the
production of 1 kg gravel (Stripple, 2001).
Energy
Amount
Coal
9.6E-05 MJ
Oil
1.0E-03 MJ
Peat
1.1E-05 MJ
Natural gas
2.2E-05 MJ
Biomass fuel
1.1E-04 MJ
Electricity
2.4E-03 MJ
Emissions to air
Amount
Co2
0.07 g
Co
0.07 mg
Nox
0.6 mg
Sox
0.05 mg
Ch4
0.38 mg
The impact of aggregate production in both terms of manufacturing and CO2
emission are not significant. The considerable impact by the aggregate production refers
to dust in operations of mining and blasting, quarry roads, loading and unloading,
crushing, screening, and storage piles. Primary impacts of crushed rock, aside from
mining impacts, stem from fugitive dust released during crushing and screening
operations. Processing of aggregates, particularly the commonly used silica sand,
releases particulates into the air that can cause eye and respiratory tract irritations in
humans. The operation of mining equipment consumes energy and releases emissions
from internal combustion engines. Impacts from mining and quarrying aggregates are
discussed in greater detail in the stone and aggregates chapter. Energy to produce coarse
and fine aggregates from crushed rock is estimated by the PCA’s Life Cycle Inventory
to be 35,440 kJ/metric ton. The energy to produce coarse and fine aggregate from
uncrushed aggregate is 23,190 kJ/metric ton (Medgar, Nisbet, and Van Geem 2006).
Energy sources are split evenly between diesel oil and electricity. Fuel consumption and
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16
environmental impacts of fuel combustion for transportation of aggregates can be
significant, as they are heavy and bulky materials. Using local or on-site materials for
aggregate can minimize fuel use, resource consumption, and emissions.
2.3
Concrete Production
Energy use and emissions of ready mix concrete vary widely by cement type and
use of pozzolanic constituents such as fly ash, silica fume or slag. Mixes with lower
cement content and higher percentages of other pozzolanic constituents have lower
embodied energy and lower emissions. A Life-cycle Inventory by the Portland Cement
Association of three different ready mixes supports this idea. One mix studied was a
standard 28-day compressive strength, 3,000 psi ready mix with 100% Portland cement.
The second mix replaced 25% of the cement with fly ash, and the third replaced 50% of
the Portland cement with slag cement. Key findings are (Medgar et al. 2007)
i.
Embodied energy for the standard PCC mix is highest at 1.13 GJ/m3 of concrete
and is lowest for the 50% slag cement mix at 0.73 GJ/m3.
ii.
CO2 emissions are highest for mix 1 at 211 kg/m3 and lowest for mix 3 at 112
kg/m3. CO2 reductions are even more substantial for mixes 2 and 3 because of
the additional savings of CO2 release from calcination of limestone, which
accounts for an average of 60% of CO2 emissions from the production of
cement.
iii.
Particulate emissions from cement production account for 70% of the total and
aggregate production for 30% of total particulate emissions for concrete. The use
of fly ash and slag lowers total particulate emissions.
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17
Table 2.6: Energy demand and emissions to air for the
production of 1m3 of typical concrete (Rydh et al., 2002)
2.4
Energy
Amount
Oil
15 MJ
Electricity
33 MJ
Emissions to air
Amount
CO2
1.5 kg
CO
0.86 g
NOx
2.3 g
SOx
3.3 g
CH4
1.7 g
HC
0.32 g
Environmental Impact of Transport Distances
Based on the investigation by Jeannette Sjunnesson,2005,he found that transport
distances is one of the main contributors to the total environmental impact from concrete
and in order to avoid this ,tried to show this important factor by evaluation the outcome
changes when the transport distances vary. As shown in Figure 2.3 the transport
operations stand for twice as much environmental impact as the raw material production.
If the transport distances are reduced by 40 % the environmental impact between raw
material production and transports becomes almost equal, only 10 % difference,.
(Jeannette Sjunnesson LUNDS TEKNISKA HÖGSKOLA,2005)
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18
EP (normal house building concrete 100% transport)
40
35
30
25
20
gPO4eqFU
15
10
5
0
Raw
material
Concrete Demolition Transports
EP (normal house building concrete 60% transport)
40
35
30
25
20
15
gPO4eqFU
10
5
0
Raw
material
Concrete Demolition Transports
Figures2.3 : Different distance in EP impact (Jeannette Sjunnesson, LUNDS
TEKNISKA HÖGSKOLA,2005)
`
19
2.5
Calculating The Concrete Waste
The amount of concrete waste, can be estimated if the material wastage level of
concrete is known. Recent research indicated that the average wastage level is about 4%,
which is considered the norm for the concreting trade. However, it could be reduced to
3% if careful material ordering and handling is applied. The amount of waste can be
estimated according to: (Cheung, 1993)
Concrete Waste = Quantity of Concrete Ordered - Quantity of Concrete Used
2.6
Recycling and land filling
The impact of the construction and demolition works to the environment waste
management for construction activities has been promoted (Shen et al., 2002). The
construction industry plays a vital role in meeting the needs of society and enhancing the
quality of life (Tse, 2001; Shen and Tam, 2002). However, the responsibility for
ensuring the construction activities and products in consistent with environmental
policies and needs to be defined and good environmental practices through reduction of
wastes need to be improved (EPD, 2002). Normally, the best way to deal with material
wastes is not to create it in the first place (Gavilan and Bernold, 1994).
The environmental situation resulted from construction has become a pressing
issue. According to the Environment Protection Department (EPD) (Chung, 2000), the
construction industry generated about 32,710 tones of construction wastes per year in
1998, nearly 15% above the figure in 1997. To manage such a huge quantity of
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20
construction wastes, must adopts a policy of disposing the waste to either land
reclamation or landfills. For decades, landfill has provided a convenient and costeffective solution to the wasteful practices of the industry (Mills et al., 1999).
According to Rogoff and Williams (1994), 29% of the solid-wastes in the USA
are construction wastes. Wong and Tanner (1997) pointed out that the landfills,
originally expected to last 40 to 50 years, would be filled up by 2010, even if there are
adequate outlets for construction materials. All these investigations demonstrate that
construction business is a large contributor to waste generation and that there is
significant potential for protecting the environment through managing construction
wastes properly.
When structures are demolished, the waste concrete can be crushed and reused in
place of virgin aggregate. Doing so reduces the GHG emissions associated with
producing concrete using virgin aggregate material. Virgin aggregates, which include
crushed stone, gravel, and sand, are used in a wide variety of construction applications,
such as road base, fill, and as an ingredient in concrete and asphalt pavement. Over 2
billion tons of aggregates are consumed each year in the US, with an estimated 5 percent
coming from recycled sources such as asphalt pavement and concrete. Unlike many of
the other materials for which EPA has developed GHG emission factors (e.g., aluminum
cans, glass bottles), concrete is assumed to be recycled in an “open loop” – i.e., concrete
is recycled into a product other than itself, namely aggregate. Therefore, the GHG
benefit of concrete recycling results from the avoided emissions associated with mining
and processing aggregate that concrete is replacing.
The GHG benefits of recycling are calculated by comparing the difference in
emissions associated with producing and transporting a ton of virgin aggregate versus
producing and transporting a comparable amount of recycled inputs (i.e., crushed
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21
concrete). The GHG emissions associated with these steps result from the consumption
of fossil fuels used in the production and transport of aggregate (combustion energy), as
well as the upstream energy (pre-combustion energy) required to obtain these fuels. The
calculation of avoided GHG emissions for concrete aggregate was broken up into two
components: process energy and transportation energy emissions. Tables present these
results, as well as the net GHG emission factor for recycling. The last part of this
research conducted in the same way.
Table 2.7: Process energy emissions calculations for recycled aggregate
(U.S.EIA,2001)
(a)
Fuel Type
Percent
of Total
Btu
Diesel Fuel
Total
`
(b)
Million Btu
used for
Aggregate
Production
(=0.0935 x a)
(c)
Fuelspecific
Carbon
Coefficient
(MTCE/
Million
Btu)
(e)
Process Energy
CO2 Emissions
(MTCE/Ton)
(=b x c)
(g)
Total
Transport
Process
Energy
Emissions
(MTCE/To
n)
100%
0.0935
0.0199
0.0003
0.0019
100%
0.0935
n/a
0.0006
0.0019
22
Table 2.8: Transportation energy emissions calculations for recycled aggregate
(a)
Fuel Type
Percent
of Total
a
Btu
(b)
Million Btu
used for
Aggregate
transport
(=0.0352 x a)
(c)
Fuelspecific
Carbon
Coefficient
(MTCE/
Million
Btu)
(e)
Transport Energy
CO2 Emissions
(MTCE/Ton)
(=b x c)
(g)
Total
Transport
Energy
Emissions
(MTCE/To
n)
Diesel Fuel
50%
0.0176
0.0199
0.0003
0.0004
National Average
50%
0.0176
0.0158
0.0003
0.0003
100%
0.0352
0.0357
0.0006
0.0007
Fuel Mix for
Electricity
Total
Table2.9: Aggregate recycling emission factor (Wilburn and Goonan, 1998)
(a)
(b)
(c)
Process
Transportation
Total
Energy Emission
Energy Emission
(a + b)
Recycle Manufacture
0.0006
0.0019
0.0025
Virgin Manufacture
0.0009
0.0037
0.0047
Total(Recycled- virgin)
-0.0003
-0.0019
-0.0021
2.7
Current Situation of Construction and Demolition Waste in Asia
This section highlights the overview of current situation of construction and
demolition waste in some selected Asian countries. As it shows by the following figures,
figure 2.4 illustrates C&D waste generation in million metric tons in Asian countries.
China has the highest waste generation in Asia, followed by Japan and South Korea.
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23
Vietnam estimated C&D waste generation includes part of sewage waste which is quite
minimal part of the total municipal solid waste. Currently, no data on C&D waste
generation at national level for Thailand, but in Bangkok Metropolitan Area (BMA)
tremendous amount of C&D waste is observed. Actual statistics of C&D waste
generation is illustrated in countries like Hong Kong SAR, India, Japan, South Korea,
Singapore, BMA Thailand, Taiwan and Vietnam. Most of the countries in Asia do not
have data and information on C&D waste generation. The C&D waste is included in the
Municipal waste. Countries with huge waste arising correlate with development
particularly the construction activities. (Asian Institute of Technology,2008)
Singapore(2003)
0.423
PRChina(2005)
200
Thailand(2005)
0.5
Taiwan(2004)
16,32
Malaysia(1994)
1.55
South
Korea(2000)
28.75
Japan(2000)
85
India(2001)
Hong
14.7
Kong(2004)
Vietnam(2004)
20.5
1.35
Fig. 2.4: C&D Waste Generation in Million Tons.
(Asian Institute of Technology,2008)
According to Central Pollution Control Board India, the total generation of waste
from construction industry is estimated to be 14.7 million tons per year (Pappu, 2006).
As illustrated in Figure 2.4, the amount of construction waste generated in India is less
compared with other countries, knowing that India has large geographical area which
might somehow correlate with the size of the country, the reason because the generated
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24
waste do not account the quantum amount renovation and demolition waste. In addition,
the reason also is that because most of the C&D waste is dumped anywhere e.g. in Pune,
India, C&D waste is dumped along the riverside haphazardly (Express India news,
2008).
As cited by Li et. al. (2004) generally urban development directly leads to the
increase of construction and demolition waste. Figure 2.5 depicts the construction
activity in Asia in terms of GDP from 2000 to 2006. Data source in the figure is
extracted from Key Indicators 2007 published by ADB. The trend in GDP from
respective Asian country contributed by the construction sector indicates construction
activities.
Fig. 2.5: Trend of National Account of Construction Sector in Asia (% GDP)
Source: Extracted from ADB Key Indicators 2007, Vol. 38
As illustrated in Fig 2.5, data results from literature review, interview and survey
sources indicated that construction regulation in most of the Asian countries is practiced
formally. Some countries consider only large size construction projects and middle end
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25
size projects with construction regulations. While regulation to demolished buildings is
still not yet recognize in most of the countries. Some of them like countries from
Indonesia, India, Malaysia and Thailand practiced demolition permit in an informal way,
meaning some cities and/or states (e.g. India) of these countries practiced it and some
does not. It depends also of the size of the construction project that require demolition
permit. No regulations are present on demolition activities at the moment in some
countries in Asia. Countries such as Nepal and Sri Lanka does not recognize demolition
permit. The unknown status indicates no data and information is available of this type of
permit regulations. (Asian Institute of Technology,2008)
Urban environmental management in the construction industry has been growing
rapidly in some countries in Asia. Attaining towards sustainable development, some
countries take efforts towards practicing environmental management system (EMS).
Research in Singapore and Hong Kong SAR highlighted that C&D waste imposes an
environmental burden. Construction industry has one of the highest resource uses and
responsible for waste pollution. Some international and local construction industries in
Singapore have already adopted the structured approach for improvement of the
environmental performance of construction by ISO 14000 EMS (Ofori, 2000). Another
case in Hong Kong where the local industry has been promoting measures such as
establishing waste management plans, reduction and recycling of C&D wastes,
providing in-house training on environmental management, and legal measures on
environmental protection.
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26
2.8.
Practices on C&D Waste Management in Malaysia
National/Local Government lead in the promotion of exercising reduce, reuse
and recycle practices on C&D waste management in Malaysia. National and local
government units for formulation, development and enforcement are National
Environment Agency, Ministry of Environment, Ministry of Construction, Building and
Construction Authority, Environmental Protection Department and other local
authorities e.g. Construction Department. These national/local authorities have waste
management plan, either individually or as part of a regional plan, that addresses C&D
waste issues.
2.8.1
Construction Sector’s Waste Profile
In Malaysia, the construction industry generates a lot of construction waste
which cause significant impacts on the environment and increasing public concern.
Thus, the minimization of construction waste has become a pressing issue.
The source of construction waste at the project site includes materials such as
soil and sand, brick and blocks, concrete and aggregate, wood, metal products, roofing
materials, plastic materials and packaging of products. The composition of total waste
generation is shown in Figure 2.6, which is percentage by weight. Concrete and
aggregate is the largest component with 65.8% followed by soil and sand (27%), 5%
from wood based materials such as timber, lumber, etc., 1.6% from brick and block, 1%
from metal products, 0.2% from roofing materials and 0.05% from plastic and
packaging products such as papers, cardboards, etc (Begum et al., 2006).
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27
1.16%
1%
0.20%
5%
0.05%
concreteand
aggregate
soilandsoil
27%
woodmaterial
65.80%
brickandblocks
metalproduct
Figure 2.6: Composition of total waste generation (Begum et al., 2005).
2.8.2
Policies and laws
In the case of Malaysia, few regulating bodies’ in some municipalities or cities
which deal with construction waste management, namely Local Authorities Ordinance
(LAO), Local Authorities Cleanliness by law (LAC), Natural Resources and
Environment Ordinance (NREO). Existing regulations are concerned with waste flow
generation, transportation and disposal. Different Municipalities in Malaysia has a
numbers of provisions that are available to regulate the management of construction
waste (Tang & Larsen 2004, Chong, Tang & Larsen 2001 cited in Lau & Whyte, 2007).
Existing provisions are currently not put in place due to the fact that the C&D waste
management is yet informal. Furthermore in 2007, Department of National Solid Waste
Management under Ministry of Housing and Local Government is in the process of
formulating policies in addressing to C&D waste. The department is still new. C&D
waste is categorized as another unit of waste, and not included in the municipal waste
category (source: interview with officer at Ministry of Housing and Local Government,
Malaysia,2008).
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28
2.8.3
Practices
Sustainable Building in South East Asia (SBSEA), a sub-regional forum for
discussion among stakeholders and relevant institutions - to overcome the challenges
and obstacles in implementing Sustainable Building Construction (SBC). SBSEA is
designed to support local, national and regional initiatives of sustainable building and
construction (SBC). It brings together different stakeholders. The forum is a dialogue for
contribution to sustainable development in the region and options for supporting and
promoting SBC (http://www.cibklutm.com). Partners and collaborators for this event are
the International Council for Research & Innovation in Building and Construction
International
Initiative,
for
Sustainable
Built
Environment
United
Nations,
Environmental Programme United Nations, the host country Institution and Sustainable
Building & Construction Initiative World Green Building Council.
2.8.4
Waste Management Stakeholders
Malaysian Stakeholders Participation on C&D waste management includes
developers, contractors, construction industry, research institutes, local authority and
government and NGOs. Large contractors give some awards for 3R to the Project
managers, site supervisors and also workers. Construction waste disposal charge in
Bangi, Selangor Area (local) in average RM 50 or US$ 15 per ton.
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29
2.8.5
Waste Management Technologies
In 2007, Malaysia has sanitary landfill for C&D wastes; however, the status of
the facility is still weak as it needs participation from construction practitioner. Reuse
and recycle of concrete and aggregate and construction wood waste A study done by
Begum et al. (2006) of the project sites in Malaysia, construction waste materials
contain a large percentage of reusable and recyclables. Estimated 73% of the waste
materials in the project site are reused and recycled. Table 2.9 shows the amount of
reused and recycled waste materials on the site.
The highest amount of reused and recycled materials is concrete and aggregate,
comprising 67.64% of the total reused and recycled material. It is followed by soil and
sand, wood, brick and block, metal products and roofing materials. The practice reuse
and recycling of construction waste materials is common on the site of one of the project
sites. (Begum, 2006).
Table 2.10: Amount of reused and recycled construction waste materials on site
(Begum et al., 2006)
Amount of reused and recycled
`
Construction Waste Material
Tonnage
Percentage
Soil and Sand
5400
27.33
Brick and block
126
0.64
Concrete and aggregate
13365
67.64
Wood
810
4.00
Metal products
54
0.27
Roofing material
5.4
0.03
Total
19760.4
100
30
CHAPTER III
RESEARCH METHODOLOGY
3.1
Introduction
This research methodology will explain how the objective of this study can be
achieved. This chapter describes the method used in carrying out this study. This study
was carried out first through the literature search and will follow by questionnaire
survey. Subsequently, data being analyzed and their results and inference will be
presented. This environmental assessment follows the standard protocol of life cycle
assessments, LCA, (ISO 14040-14043). LCA was used as a method to evaluate the
environmental impact from the entire life cycle of a product, from “the cradle to the
grave”. Here life cycle inventory (LCI) data were collected from existing LCA reports,
environmental reports. The results are presented both per kg material for each raw
material and per functional unit (FU) (see APPENDIX B – Inventory tables) which is
equivalent to 1 m3 of concrete. The data reported included, energy, and CO2 emissions
to air for each stage in the manufacturing. All fuels, energy and emissions associated
with transportation were reported separately. The ready mixed concrete for super
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31
structure building represents in this study with the strength levels 20 MPa (3,000
psi).There would be some assumption that describe in Analyzing and Discussion part.
Finally this paper shows the comparison of different way of disposal by land filling or
recycling and data sources used to develop greenhouse gas (GHG) emission factors for
recycled concrete, and land filling presented are the latest in a series of emission factors
developed by the U.S. Environmental Protection Agency (EPA).
3.2
Inventory result
The goal of the inventory phase is to determine quantities of all materials,
energy, and CO2 pollutants that contribute to the product or system being investigated.
These data must be assembled for all life cycle stages. For example, since concrete
consists of cement, water, aggregate, and chemical admixtures, a concrete wall has these
life cycle stages.
The data for production of cement and other ingredient of concrete collected
from the last research by (Jeannette Sjunnesson,2005) which collected from various
ingredients utilized in cement production in Cementa AB’s report. Data for aggregate
production is taken from an existing LCA report.(Stripple, 2001) .Data for admixture
were taken from an EPD by the European Federation of Concrete Admixture
Associations (EFCA). Data on transportation modes ,Transportation of cement,
aggregates, and other constituent materials to ready-mix plant and distances for raw
materials are primarily from NTM (Natverket for Transporter och Miljon, 2005).The
transports for the raw materials and concrete produced are by trucks; either heavy trucks
or medium heavy trucks except for the transport of cement to depot which is not
consider in this research,. Cement and admixtures are both transported by heavy trucks.
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32
Aggregate by a medium heavy truck. Ready- mixed concrete is transported in a liquidconcrete carrier, which is assumed to have the same characteristics as a medium heavy
truck. Data for vehicle transportation in APPENDIX A – LCI data. All transport
distances are as following table :
Table 3.1: Vehicle Option (Jeannette
Sjunnesson,2005)
Transported goods
Vehicle
Distance(KM)
Cement (to concrete plant from depot)
Heavy truck
50
aggregate (to concrete plant)
Medium heavy
20
Super plasticizer (to concrete plant)
Heavy truck
50
Concrete (from concrete plant)
Medium heavy
100
Comparison of disposal options i.e.
land filling and recycling was also
conducted by using data sources of emission factors developed by the U.S.
Environmental Protection Agency (EPA) such as greenhouse gas (GHG) emission
factors for recycled concrete, and land filling. To calculate the benefit of recycling
concrete to displace virgin aggregate the following steps were done: Step 1: Calculate
the emissions for virgin production of aggregate, Step 2: Calculate the emissions
associated with processing and delivering a comparable amount of recycled concrete to
be used in place of virgin aggregate, Step 3: Calculate the difference in emissions
between recycled and virgin scenarios.For the calculation of this emission factor, in this
thesis assumed that virgin aggregates must be transported 30 miles to the end user. For
the calculation of this emission factor, assumed that recycled aggregate (waste concrete)
must be transported 15 miles to the end user.
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33
3.3
System boundaries
The phases of the life cycle of concrete included in this study are shown in
Figure 3.1. The use of water as a raw material is excluded since water is not regarded as
a limited resource. To get a fair picture of the environmental impact of concrete, the
time-frame must be sufficiently long. However, the carbonization of concrete will not be
taken into consideration since the duration of this process is too long for this study.
T
T
R
R
A
A
N
N
Cement
Aggregate
S
Water
Admixture
Concrete
S
P
P
O
O
R
R
T
T
On site
Disposal of
concrete
waste
Figure 3.1: General Flowchart for the concrete life cycle Jeannette Sjunnesson
(Jeannette Sjunnesson,2005)
`
34
3.4
Data Collection
Data was collected from various sources including literatures and actual site
investigation. A set of questionnaire was distributed to the selected construction sites.
Interview sessions were also conducted from selected respondents to obtain their
professional views.
3.4.1 Questionnaire Survey
The questionnaire survey was carried out to gather information from the three
construction sites in U.T.M. these questionnaires were distributed by manual and
followed by interviews session.
3.4.1.1 Questionnaire structure
The questionnaire was structured into three sections:
Section A: To obtain information about the respondent’s background
Section B: To survey the level of wastage in construction sites
Section C: To survey the different mixing design
Section D: To survey the disposal option
The sample of questionnaire used for the survey in this project is shown in Appendix A.
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35
3.5
Data analysis
Upon the collection of questionnaire, every type of the data received under
different question will be separated to answer different study objectives. The data will
be analyzed manually by using the LCI and EPA data and which mentioned in this
chapter. for calculation the wastage of concrete level, there is formula(Cheung, 1993)
Concrete Waste = Quantity of Concrete Ordered - Quantity of Concrete Used
Analysis was also conducted in term of the environmental impact based on two
impact indicators i.e. energy and CO2 due to the quantity of the concrete waste
generated. The analysis on the disposal option of the concrete waste was also discussed.
3.6
Stages of the study
Three stages of the action were formulated for the approach of the study. Stage 1
comprises of a search on literatures on and surrounds of the subjects. Stage 2 comprise
of the interviewing involving the key stakeholders seeking on the data and information
of the particular of the study. Stage 3 comprises of analysis the finding, making
conclusion and recommendations based on the founded information from the stages 1
and 2.In stage 1, in depth literature reviews were conducted related to the interest of the
study. This stage involve of a search on the ‘review of the current concrete wastage
issues in construction industry sites. Stage 2 comprises of interview and questionnaire
survey involving the key personnel of stakeholders. The target respondents were
identified by their qualification. In the questionnaire there are three sections which start
by finding the amount of concrete wasted in construction site in U.T.M by asking for
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36
quantity of ordering and cumulative of work done for the concrete for super structures.
The second part consists of amount of ingredient for making of concrete in 1 m3 from
aggregate, water, cement and admixtures. The third part would ask about the disposal of
concrete in different situation such as Recycling or Land filling and Incineration. The
questionnaire could be found in Appendix “B” which consists of 3 sections. This list is
provided for completeness of the project report. The use of this list for any other
purposes is strictly prohibited. At stage 3 the analysis of data and information’s gathered
from the survey were done.
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37
Literature review
¾ Literature search using books and
journals
¾ Study and explore the concrete
wastage level in construction sites
¾ Study and explore the causation of
concrete waste
¾ Questionnaire survey distributed to
3 construction sites in U.T.M
¾ The objectives were to:
ƒ
Questionnaire survey
ƒ
ƒ
ƒ
To estimate the amount of
energy used and CO2 emission
for production of concrete
To estimate the total energy
and CO2 emission based on the
different weight of concrete
waste on sites.
To evaluate the disposal option
of concrete waste.
To determine the amount of
concrete waste in construction
sites.
Data Analysis and discussion
¾ The data will be analyzed
manually by using the table which
mentioned in this chapter.
Conclusion and Recommendation
¾ Conclude the finding
¾ Recommendation for improvement
and suggestion for further
research.
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38
CHAPTER IV
ANALYSIS AND DISCUSSION
This chapter discusses the presentation of data from a record of data collected,
the analysis, interpretation and discussion of the results obtained through the survey
research implemented.
The purpose of data preparation is to present the data, to have a feel of the data,
and to get the data correct and ready for analysis. The process of analysis began by
summarizing and rearranging the raw data into appropriate format which ease for further
analysis.
The interpretation of data must clear and appropriate involved explaining the
meaning of data collected and making inference. To ease the process of analysis, the
following terminology has been adopted throughout the analysis:
`
39
There are three sections in the questionnaire which start by calculating the
amount of concrete wasted in construction site in U.T.M by asking for quantity of
ordering and cumulative of work done for the concrete for super structures.
The second part consists of amount of ingredient for making of concrete in 1 m3
from aggregate, water, cement and admixtures. The third part would ask about the
disposal of concrete in different situation such as Recycling or Land filling and
Incineration. The questionnaire could be found in Appendix “B” which consists of 3
sections. This list is provided for completeness of the project report. The use of this list
for any other purposes is strictly prohibited.
4.1
Concrete Waste
The first analysis was to find out the amount of concrete wasted in construction
sites. The amount of concrete waste can be estimated if the material wastage level of
concrete is known. Recent research indicated that the average wastage level is about 4%,
which is considered the norm for the concreting trade in this guideline. However, it
could be reduced to 3% if careful material ordering and handling is applied.
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40
4.1.1
Concrete Slabs, Walls, Beams, and Columns
Portland cement concrete, typically referred to as “concrete,” is a mixture of
Portland cement (a fine powder), water, fine aggregate such as sand or finely crushed
rock, and coarse aggregate such as gravel or crushed rock. Ground granulated blast
furnace slag (slag cement), fly ash, silica fume, or limestone may be substituted for a
portion of the Portland cement in the concrete mix.
Concrete with 21 MPa strength is used in applications such as residential slabs
and basement walls, while strengths of 28 MPa and 34 MPa are used in structural
applications such as beams and columns. Portland cement concrete products like beams
and columns are modeled based on volume of concrete (e.g., a functional unit of 1 ft3),
while basement walls and slabs are modeled on an area basis (e.g., a functional unit of 1
ft2). The amount of concrete required depends on the dimensions of the product (e.g.,
thickness of slab or wall and surface area). Above-grade walls are typically 15 cm (6 in)
thick. Basement walls are 20 cm (8 in) thick, slabs 10 cm (4 in) thick, and a typical
column size is 51 cm by 51 cm (20 in by 20 in). Manufacturing data for concrete
products are taken from the Portland Cement Association’s LCA database.
Based on the information obtained from different construction sites, the table 4.1
received for Construction No 1.
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41
TABLE4.1: Cumulative quantity of ordering (m3)
in Construction No 1
`
TARIKH
G25
14/01/09
18
28/02/09
25
07/03/09
22
14/03/09
65
21/03/09
161
31/03/09
133
07/04/09
24
14/04/09
14
21/04/09
99
28/04/09
181
30/04/09
56
07/05/09
11
14/05/09
60
31/05/09
97
07/06/09
50
14/06/09
108
21/06/09
94
30/06/09
98
07/07/09
37.5
14/07/09
111
21/07/09
8
31/07/09
185.5
TOTAL
1728 M3
42
In this construction site no 1 the amount of concrete poured base on the plan
dimensions is 1644.845 M3
So the amount of wastage for construction no 1 is:
(1) Cumulative quantity of ordering (m3)=1728 M3
(2) cumulative work done (m3) =1644 M3
(3) wastage (m3) =84
(4) actual wastage percentage : 5 %
The amount of concrete waste indicated that the average wastage level is about
5%, which is considered 1% more than the norm for the concreting trade.
The amount of wastage for construction no 2 is:
(1)Cumulative quantity of ordering (m3) =370 M3
(2) Cumulative work done (m3) =350 M3
(3) Wastage (m3) =20 M3
(4) Actual wastage percentage: 5.5 %
The amount of concrete waste indicated that the average wastage level is about
5.5%, which is considered 1.5% more than the norm for the concreting trade.
The amount of wastage for construction no 3 is:
(1)Cumulative quantity of ordering (m3) =500 M3
(2) Cumulative work done (m3) =480 M3
(3) Wastage (m3) =20 M3
(4) Actual wastage percentage: 4 %
`
43
The amount of concrete waste indicated that the average wastage level is about
4%, which is considered equal the norm for the concreting trade.
4.2
Assumptions
Several assumptions were made to calculate the LCI of concrete.
i.
The functional unit for concrete is one cubic yard
ii.
Distances to the concrete plant are 100 km (60 miles) for Portland.
iii.
Road transportation is assumed in all cases, which is conservative from an
energy consumption and emissions standpoint (i.e. higher energy and emissions
than rail or barge transportation).
4.3
Concrete production
Mixing the aggregate and admixtures together with concrete paste makes
concrete. The admixture can be added differently, for example, before transport or
before casting or already during cement production, depending on what kind of effect is
to be achieved. The concrete paste is cement mixed with water and it is the binder in the
concrete. Its characteristics are controlled by the ratio of water to cement, the w/c ratio.
`
44
If the concrete is mixed and worked up appropriately the strength of the concrete is
determined by the w/c ratio.
Based on the information obtain from this research, the mixing design of the
concrete are as following:
Table 4.2: Different construction mixing design
Concrete mix
Ready Mixed Concrete
description
Construction No 1
Construction No 2
Construction No 3
28 day comp. strength
3,000 psi
3,000 psi
3,000 psi
Portland cement(Kg)
361
300
320
Slag cement
0
0
0
Fly ash
0
0
0
Silica fume
0
0
0
Water
180
180
180
Coarse aggregate
990
1000
830
Fine aggregate
777
827
970
Total
2308
2307
2300
4.4
Cement Energy Demand
Based on the information obtained from construction site the amount of cement
which used in this construction sites is 1728 M3 * 361 Kg/M3= 623808 Kg cement
and based on the table 2.3 in order to produce 1 Kg cement 3.35 MJ energy needed so
that for the amount of total ordering concrete is equal to
3.35 MJ/Kg * 623808 Kg = 2089756 MJ = 2089.7 GJ (construction no 1)
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45
3.35 MJ/Kg * 111000 Kg = 371800 MJ = 371.85 GJ (construction no 2)
3.35 MJ/Kg * 160000 Kg = 536000 MJ = 536 GJ (construction no 3)
4.5
Aggregates Energy Demand
In aggregate production diesel is used in internal transports. All of the crushing
machines are driven by electricity. In the extraction of gravel a wheel loader is used to
excavate the gravel, while the internal transports use lorry loaders. Inventory results for
macadam and gravel production based on the table 2.5 is 0.067 MJ/Kg.
So for project 1, for 1767 Kg/m3 aggregate the energy required is:
0.067 MJ/Kg * 1767 Kg/m3 = 118.4 MJ/m3= 0.118 GJ/m3
1728 m3 (concrete ordering) * 1767 Kg/m3 (aggregate) = 3053376 Kg (total aggregate)
Total Energy demand = 0.118 GJ/m3 * 1728 m3 = 204 GJ
Total Energy demand = 3053376 Kg * 0.067 MJ/Kg = 204 GJ
So for project 2, for 1827 kg/m3 aggregate the energy required is
0.067 MJ/kg * 1827 Kg/m3 = 122.4MJ/m3 = 0.122 GJ/m3
370 m3 (concrete ordering) * 1827 m3 = 675990 kg (total aggregate)
Total energy demand = 0.122 GJ/m3 * 370 m3 ~45 GJ
So for project 3, for 1800 Kg/m3 aggregate the energy required is
0.067 MJ/Kg * 1800 Kg/m3 = 120.6 MJ/m3= 0.12 GJ/m3
500 m3 (concrete ordering) * 1800 Kg/m3 (aggregate) = 900000 Kg (total aggregate)
Total Energy demand = 0.12 GJ/m3 * 500 m3 = 60 GJ
Total Energy demand = 900000 Kg * 0.067 MJ/Kg ~ 60 GJ
`
46
4.6
Energy for Wasted Cement and Aggregate
Based on the amount of cement which wasted, the energy demand is:
Project 1
Wasted cement for 84 M3 = 30324Kg
Energy demand for production of this amount =
3.35 MJ/Kg * 30324 Kg = 101585.4 MJ = 101.6 GJ
Energy for wasted cement/energy for total cement =101.6 / 2089.7 = 0.04 = 4%
Based on the result, 4 % extra energy wasted for production of wasted cement
And also for production of wasted aggregate also:
Wasted aggregate = 84 m3 * 1767 kg/m3 = 148428 kg
Energy demand = 148428 Kg * 0.067 MJ/Kg = 99451 MJ= 10 GJ
Energy for wasted aggregate/energy for total aggregate = 0.04 = 4%
Based on the result, 4 % extra energy wasted for production of wasted aggregate
Project 2
Wasted cement for 20 M3 = 6000Kg
Energy demand for production of this amount =
3.35 MJ/Kg * 6000 Kg = 20100 MJ ~ 20 GJ
Energy for wasted cement/energy for total cement =20 / 371.85 = 0.055 = 5.5%
Based on the result, 5.5 % extra energy wasted for production of wasted cement.
And also for production of wasted aggregate also:
Wasted aggregate = 20 m3 * 1827 kg/m3 = 36540 kg
Energy demand = 36540 Kg * 0.067 MJ/Kg = 2448 MJ= 2.44 GJ
Energy for wasted aggregate/energy for total aggregate = 0.055 = 5.5%
Based on the result, 4 % extra energy wasted for production of wasted aggregate
`
47
Project 3
Wasted cement for 20 M3 = 6400Kg
Energy demand for production of this amount =
3.35 MJ/Kg * 6400 Kg = 21440 MJ ~ 21.5 GJ
Energy for wasted cement/energy for total cement =21.5 / 536= 0.04 = 4%
Based on the result, 4 % extra energy wasted for production of wasted cement.
And also for production of wasted aggregate also:
Wasted aggregate = 20 m3 * 1800 kg/m3 = 36000 kg
Energy demand = 36000 Kg * 0.067 MJ/Kg = 2412 MJ ~ 2.4 GJ
Energy for wasted aggregate/energy for total aggregate = 0.04 = 4%
Based on the result, 4 % extra energy wasted for production of wasted aggregate
4.7
CO2 Emission
CO2 is the chemical formula for carbon dioxide, a gas which exists in relatively
small amounts (380 parts per million or ppm) in our atmosphere.
Based on the table above total Co2 emission for production of cement is:
623808 Kg * 0.71 Kg = 442903 Kg (project 1)
111000 Kg * 0.71 Kg = 78810 Kg (project 2)
160000 Kg * 0.71 Kg = 113600 Kg (project 3)
And also CO2 Emission for wasted cement production is
Project 1
30324 Kg * 0.71Kg = 21530 Kg
Which means 21530/442903 = 0.04 = 4 %( extra CO2 emission)
`
48
Project 2
6000 Kg * 0.71 Kg = 4260 Kg
Which means 4260/78810 = 0.055 = 5.5 % (extra CO2 emission)
Project 3
6400 Kg * 0.71 Kg = 4544 Kg
For aggregate CO2 Emission:
Based on the table by LCI data, the amount of CO2 Emission for 1 Kg aggregate is 0.9 g
So based on this information, CO2 emission for production of total aggregate is:
3053376 Kg * 0.9 g = 2748038 g ~2748 Kg (project 1)
675990 Kg * 0.9 g = 608391 g ~ 608 Kg (project 2)
900000 Kg * 0.9 g = 810000 g = 810 Kg (project 3)
And on the other hand CO2 emission for wasted aggregate is:
Project 1
148428Kg * 0.9 g ~ 133 Kg
So that the extra CO2 Emission is
133 Kg/ 2748 Kg = 0.04 = 4 %
Project 2
36540Kg * 0.9 g ~ 33 Kg
So that the extra CO2 Emission is
33 Kg/ 608 Kg = 0.055 = 5.5 %
Project 3
36000Kg * 0.9 g ~ 33 Kg
So that the extra CO2 Emission is
`
49
33 Kg/ 810 Kg = 0.04 = 4 %
4.8
Admixture
Daratard admixture is a ready-to-use aqueous solution of modified salts of
hydroxylated carboxylic acids. Ingredients are factory pre-mixed in exact proportions to
minimize handling, eliminate mistakes and guesswork. One Liter weighs approximately
1.17 kg (9.8 lb/gal). In all construction sites in U.T.M, the only admixture which in used
was Daratard. Based on the information by EFC (Environmental Declaration Super
plasticizing Admixtures, 2002), for 1 kg Daratard 16 MJ energy consumed for
production and also 0.69 kg CO2 emission for 1 kg Daratad. And based on the
information given by site project 1, for 400ml Daratard for 100 kg cement used. So that
for 1 m3 concreting
Project 1
361 kg (cement) = 1444ml Daratard = 1.44 L
1 liter Daratard = 1.17 kg
1.44 liter Daratard = 1.7 kg
1kg Daratard = 16 MJ/kg >>>>>1.7 kg Daratad = 27 MJ = 0.027 GJ
So based on this information for total concreting (1728 m3)
0.027 GJ * 1728 m3 = 47 GJ
Wasted = 0.027 * 84 m3 = 2.268
Project 2,
410 ml for 100 kg cement
`
50
300 kg (cement) = 1.23 L = 1.44 kg
Energy: 1.44 kg * 16 MJ/kg = 23 MJ = 0.023 GJ
Total concreting = 370m3 * 0.023 GJ =8.5 GJ
Wasted = 0.023 GJ * 20m3 = 0.46 GJ
Project 3,
400 ml for 100 kg cement
320 kg (cement) = 1.28 L ~ 1.5 kg
Energy: 1.5 kg * 16 MJ/kg = 24 MJ = 0.024 GJ
Total concreting = 500 m3 * 0.024 GJ =12 GJ
Wasted = 20 m3 * 0.024 GJ = 0.48 GJ
Emission by admixture
Based on the information by EFC data, for 1 kg admixture, 0.69 kg CO2 emission
produced. So that
For 1 m3 concreting = 1.7 kg Daratard * 0.69kg = 1.173 kg
For total concreting = 1728 m3 * 1.173 kg = 2027 kg (project 1)
For 1 m3 concreting = 1.44 kg Daratard * 0.69kg = 1 kg
For total concreting = 370m3 * 1kg = 370 kg (project 2)
For 1 m3 concreting = 1.5 kg Daratard * 0.69kg ~1 kg
For total concreting = 500 m3 * 1kg = 500 kg (project 3)
For wasted concreting = 84 m3 * 1.173 kg = 98.5 kg (project 1)
For wasted concreting = 20 m3 * 1.173 kg = 23.5 kg (project 2)
For wasted concreting = 20 m3 * 1.173 kg = 23.5 kg (project 3)
`
51
4.9
Transportation
Project 1
1m3 cement= 361 kg/m3
0.361 ton/m3 *50 KM * 0.6 MJ/tkm = 10.83 ~ 0.01GJ(1m3 of Cement production)
1m3 aggregate = 1767 Kg/m3
1.767 ton/m3 * 20 KM * 1.9 MJ/tkm = 67 MJ ~0.067 GJ(1m3 of Aggregate production)
1m3 admixture = 1.7 kg
0.0017 ton/m3 * 50 KM * 0.6 MJ/tkm = 0.051 GJ(1m3 of Admixture production)
So for 1 m3 of concrete production, the transportation will have 0.128 GJ energy
consumption and for total production 221.2GJ
Also for CO2 emission:
0.361 ton/m3 *50 KM * 0.048 kg/tkm = 0.86kg(1m3 of Cement production)
1.767 ton/m3 * 20 KM * 0.14 kg/tkm = 5 kg(1m3 of Aggregate production)
0.0017 ton/m3 * 50 KM * 0.048 MJ/tkm = 0.004 GJ(1m3 of Admixture production)
So for 1 m3 of concrete production, the transportation will have 5.86Kg CO2 emission
and for total production 10133Kg
Project 2
1m3 cement= 300 kg/m3
0.3 ton/m3 *50 KM * 0.6 MJ/tkm = 9 = 0.009GJ(1m3 of Cement production)
1m3 aggregate = 1827 Kg/m3
1.827 ton/m3 * 20 KM * 1.9 MJ/tkm = 69.4 MJ ~0.0694 GJ
1m3 admixture = 1.44 kg
0.00144 ton/m3 * 50 KM * 0.6 MJ/tkm = 0.0432 GJ
So for 1 m3 of concrete production, the transportation will have 0.1216 GJ energy
consumption and for total production 45GJ
Also for CO2 emission:
0.3 ton/m3 *50 KM * 0.048 kg/tkm = 0.72kg(1m3 of Cement production)
`
52
1.827 ton/m3 * 20 KM * 0.14 kg/tkm = 5.1 kg(1m3 of Aggregate production)
0.00144 ton/m3 * 50 KM * 0.048 kg/tkm = 0.0034 kg(1m3 of Admixture production)
So for 1 m3 of concrete production, the transportation will have 5.82Kg CO2 emission
and for total production 2154.6Kg
Project 3
1m3 cement= 320 kg/m3
0.320 ton/m3 *50 KM * 0.6 MJ/tkm = 9.6 ~ 0.0096GJ(1m3 of Cement production)
1m3 aggregate = 1800 Kg/m3
1.8 ton/m3 * 20 KM * 1.9 MJ/tkm = 68.4 MJ ~0.0684 GJ
1m3 admixture = 1.5 kg
0.0015 ton/m3 * 50 KM * 0.6 MJ/tkm = 0.045 GJ
So for 1 m3 of concrete production, the transportation will have 0.123 GJ energy
consumption and for total production 61.5GJ
Also for CO2 emission:
0.32 ton/m3 *50 KM * 0.048 kg/tkm = 0.768kg(1m3 of Cement production)
1.8 ton/m3 * 20 KM * 0.14 kg/tkm = 5 kg(1m3 of Aggregate production)
0.0015 ton/m3 * 50 KM * 0.048 kg/tkm = 0.0036 kg(1m3 of Admixture production)
So for 1 m3 of concrete production, the transportation will have 5.76Kg CO2
emission and for total production 2882Kg
4.10 Transportation concrete to the site from concrete plant
Project 1
2308kg/m3 ~2.3 ton
`
53
2.3ton * 100 Km * 1.9 MJ/tkm = 437 MJ = 0.437 GJ
So the energy required for 1728 m3 total concreting:
1728m3 * 0.437GJ = 755 GJ
Based on the finding, the wastage amount is 84 m3
Therefore 84 m3 * 0.437 GJ ~ 36.7
That 36.7/755 = 4.8%
Project 2
2307 kg/m3 ~ 2.3 ton
Energy required for 370 m3 total concreting:
370 * 0.437 = 161 GJ
Therefore 20 m3 * 0.437 GJ = 8.74
That 8.74/161 = 0.055 = 5.4%
Project 3
2300 kg/m3 = 2.3 ton
Energy required for 500 m3 total concreting:
500 * 0.437 = 218.5 GJ
Therefore 20 m3 * 0.437 GJ = 8.74
That 8.74/218.5 = 0.04 = 4%
CO2 Emission to air by transportation
Project 1
Based on LCI data, the amount of CO2 emission for 1tkm is equal 0.14kg
2.3ton * 100 Km * 0.14 Kg/tkm = 32.2 kg (for 1 m3 of concrete)
Total concreting: 1728 m3 * 32.2 kg/m3 = 55641.6 kg
Based on the amount of wastage, we have:
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54
84 m3 * 32.2 kg/m3 = 2704.8 kg
Percentage of wastage = 2704.8 / 55641.6 = 4.8 %( extra CO2 emission)
Project 2
Total concreting: 370m3 * 32.2kg/m3 = 11914 kg
Based on the amount of wastage, we have:
20 m3 * 32.2 kg/m3 = 644 kg
Percentage of wastage = 644 / 11914 = 5.5 %( extra CO2 emission)
Project 3
Total concreting: 500m3 * 32.2kg/m3 = 16100 kg
Based on the amount of wastage, we have:
20 m3 * 32.2 kg/m3 = 644 kg
Percentage of wastage = 644 / 16100 = 4 %( extra CO2 emission)
Based on the different quantity of ordering concrete on site, three construction
sites have different total embodied energy and CO2 emission. Based on the table 4.2 for
1 m3of concrete mixing design, although all the construction sites have the same
strength quality (3,000 psi for 28 days), it is acceptable to see the differences in
percentage of mixing design for concrete with the same characteristic. So that it is the
reason in tables 4.3,4.5,4.7 by having 1 m3 concreting, there is different embodied
energy and CO2 emission.
For example for Construction No 1,based on the amount in table 4.2,the amount
of cement for 1m3 concreting is 361kg/m3 which provide 1.2 GJ/m3 embodied energy
and 256 kg/m3 CO2 emission, on the other hand construction no 2 has 300 kg/m3 cement
for 1m3 of concreting so that the embodied energy based on the table 4.5 is 1 GJ/m3 and
`
55
213kg/m3 CO2 emission. For construction no 3,320 kg/m3 cement is equal to 1.07GJ/m3
embodied energy and 227kg/m3 CO2 emission. Base on the tables 4.2 and comparison
with the tables 4.3,4.5,4.7 it can be understandable that even with this different mixing
design, it’s the cement production that make this different bigger in terms of embodied
energy and CO2 emission. Aggregate production, transportation material to the plant,
concrete plant operation and admixture production are mostly the same for 1 m3
concreting.
In order to get the fair picture of impact of concrete to the environment in terms
of embodied energy and CO2 emission tables 4.4,4.6,4.8 shows the total concreting in 3
different construction site. In construction no 1,1728 m3 is the cumulative quantity of
ordering of concrete in which 2988.7 GJ energy consumed to produce this amount and
457811 kg CO2 emission produced. In this construction, Portland cement manufacturing
with 2089.7 GJ energy consumption and 442903 kg CO2 emission is the highest amount
which is equivalent to 70% of total energy consumption and 95 % of total CO2
emission. More ever, there is another considerable amount by transportation of concrete
to the site ,which is about 755 GJ that is more than the other mixing production and
concrete plant operation value. The transportation of concrete to the site is 25% of total
energy consumption and 10% of total CO2 emission of total concrete production. So
based on the distance which assumed 100 km for the transportation of concrete to the
site, it can be significant if this distance reduced. There is the same scenario for the rest
two construction sites. In construction no 2, the cumulative quantity of ordering is
370m3 that cement manufacturing by 371.85 GJ embodied energy and 78810 kg CO2
emission is the highest between the other manufacturing process. In construction no 3,
500 m3 is the total quantity of ordering in which cement by 536 GJ and 113600 kg CO2
emission is in top between the other manufacturing process. As it appears, by increasing
the amount of concreting, it’s the cement manufacturing which make this gap bigger and
bigger.
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56
As can be seen ,although the cement composes about 10 % of the total concrete
mix design but account for 70 % of the total embodied energy. The highest energy
demand in production of 1 kg cement is coal in which consumed 1.9 MJ energy. Besides
that, cement also is the highest in terms of CO2 emission between the other composers.
Based on the calculation above, it is about 95 % of the carbon dioxide emission in
concrete production were produced by cement manufacturing.
Table 4.3: Embodied Energy & CO2 Emission for One Cubic Meter of Concrete
Production
Concrete mix description
`
Ready mix concrete project 1
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
1.2
256
Aggregate production
0.118
1.57
Transporting materials to
Plant
0.128
5.86
Concrete plant operations
0.247
N/A
Admixture production
0.027
1.173
Total
1.72(GJ/m³)
264.6(kg/m3)
57
Table 4.4: Embodied Energy & CO2 Emission for Total Cubic Meter of Concrete
Production
Concrete mix description
Ready mix concrete project 1
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
2089.7
442903
Aggregate production
204
2748
Transporting materials to
Plant
221.2
10133
Concrete plant operations
426.8
N/A
Admixture production
47
2027
Total
2988.7(GJ/m³)
457811(kg/m3)
Table 4.5: Embodied Energy & CO2 Emission for One Cubic Meter of Concrete
Production
Concrete mix description
`
Ready mix concrete project 2
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
1
213
Aggregate production
0.122
1.65
Transporting materials to
Plant
0.1216
5.82
Concrete plant operations
0.247
N/A
Admixture production
0.023
1
Total
1.51(GJ/m³)
221.47(kg/m3)
58
Table 4.6: Embodied Energy & CO2 Emission for Total Cubic Meter of Concrete
Production
Concrete mix description
Ready mix concrete project 2
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
371.85
78810
Aggregate production
45
608
Transporting materials to
Plant
45
2154
Concrete plant operations
91.4
N/A
Admixture production
8.5
370
Total
561.75(GJ/m³)
81942(kg/m3)
Table 4.7: Embodied Energy & CO2 Emission for One Cubic Meter of Concrete
Production
Concrete mix description
`
Ready mix concrete project 3
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
1.07
227
Aggregate production
0.12
1.62
Transporting materials to
Plant
0.123
5.76
Concrete plant operations
0.247
N/A
Admixture production
0.024
1
Total
1.58 (GJ/m³)
235.38(kg/m3)
59
Table 4.8: Embodied Energy & CO2 Emission for Total Cubic Meter of Concrete
Production
Concrete mix description
Ready mix concrete project 3
Energy(GJ/m³)
CO2 Emission(kg/m3)
Portland cement
Manufacturing
536
113600
Aggregate production
60
810
Transporting materials to
Plant
61.5
2880
Concrete plant operations
123.5
N/A
Admixture production
12
500
Total
793(GJ/m³)
117790(kg/m3)
In order for better understanding of the importance impact of concrete waste in terms
of embodied energy and CO2 emission for concrete production, the tables below show this
waste amount from production until the transportation of concrete to the site. As it shows the
construction no 1, 84 m3 of concrete wasted that based on the table 4.9,144.71GJ embodied
energy consumed and 22253.7 kg CO2 emission produced by this amount of waste that
compare to the total concreting for 84m3, 3743.7GJ energy and 513452.6 kg CO2 are the
impacts of concreting in which these numbers include the wasted amount. So this amount of
waste is about 4% of total embodied energy and CO2 emission.
In table 4.9 Portland cement manufacturing by 101 GJ embodied energy is the
considerable amount between the others. Based on the table 4.6 the total embodied energy
for Portland cement manufacturing was 2089.7 GJ that 101 GJ wasted energy is included in
that amount. So minus these amount will give us the ideal amount which must be consumed
to produce the cement( 2089.7 GJ – 101 GJ = 1988.7 GJ).so 101 GJ is about 4.8 % extra
energy consumed to produce the cement. It’s the transportation operation to the plant as can
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60
be seen in tables 4.9,4.10,4.11 that have the second important amount compared to the other
manufacturing.
Based on the table 4.9 transportation of concrete to the plant has 36.7 GJ energy
consumption and 2704.8 kg CO2 emission which compare to the to the total concreting is
about 5% extra energy and CO2 emission. For construction no 2,wasted concrete is 20 m3
which 20 GJ extra energy used to produced the Portland cement which compare to the total
energy for cement manufacturing in this construction site is (371.85GJ – 20GJ = 351.85).so
about 5% extra energy consumed for cement manufacturing.
For construction no 3 also 4% extra energy consumed for cement production. Also
the same calculation can be done to see the differences in CO2 emission, in construction no
1, 21530 kg CO2 emission produced which compare to the total CO2 emission, its 4.8 %
extra CO2 produced. Which for the rest construction sites are as following, construction no 2
is 5 % and construction no 3 is 4% extra CO2 emission produced. Transportation of concrete
to the site also is considerable in which for construction no 1, 755 GJ energy compared to
36.7 GJ for wasted which is about 4.5 % extra energy consumption and for CO2 emission is
4.8% extra CO2 emission.
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61
Table 4.9: Embodied Energy & CO2 Emission for Total Cubic Meter of
Waste Concrete Production
Concrete mix description
Ready mix concrete project 1
Waste
Energy(GJ/m³)
Portland cement
CO2 Emission(kg/m3)
101
21530
10
133
10.75
492.2
Concrete plant operations
20.7
N/A
Admixture production
2.26
98.5
Transportation of concrete to the site
36.7
2704.8
Manufacturing
Aggregate production
Transporting materials to
Plant
Total
144.71(GJ/m³)
22253.7(kg/m3)
Table 4.10: Embodied Energy & CO2 Emission for Total Cubic Meter of Waste
Concrete Production
Concrete mix description
Ready mix concrete project 2
Waste
Energy(GJ/m³)
Portland cement manufacturing
CO2 Emission(kg/m3)
20
4260
Aggregate production
2.44
33
Transporting materials to
2.43
116.4
Concrete plant operations
4.94
N/A
Admixture production
0.46
23.5
Transportation of concrete to the site
8.74
644
Plant
Total
`
30.26(GJ/m³)
4433(kg/m3)
62
Table 4.11: Embodied Energy & CO2 Emission for Total Cubic Meter of Waste
Concrete Production
Concrete mix description
Ready mix concrete project 3
Waste
Energy(GJ/m³)
Portland cement
CO2 Emission(kg/m3)
23.5
4544
Aggregate production
2.4
33
Transporting materials to Plant
2.46
115.2
Concrete plant operations
4.94
N/A
Admixture production
0.48
23.5
Transportation of concrete to the site
8.74
644
Manufacturing
Total
4.11
3178(GJ/m³)
4715.7(kg/m3)
Disposal Option
Concrete waste from construction and demolition is an environmental concern,
but great strides have been made in the last decade to lessen the waste burden through
reuse of concrete debris. Concrete is estimated to account for 67% by weight of
construction and demolition waste—the largest single component (U.S. EPA 1998).
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63
4.11.1 Recycling
When structures are demolished, the waste concrete can be crushed and reused in
place of virgin aggregate. Doing so reduces the GHG emissions associated with
producing concrete using virgin aggregate material. Virgin aggregates, which include
crushed stone, gravel, and sand, are used in a wide variety of construction applications,
such as road base, fill, and as an ingredient in concrete and asphalt pavement (USGS
2000). The GHG benefits of recycling are calculated by comparing the difference in
emissions associated with producing and transporting a ton of virgin aggregate versus
producing and transporting a comparable amount of recycled inputs (i.e., crushed
concrete).
To calculate the benefit of recycling concrete to displace virgin aggregate, the following
steps were necessary:
Step 1: Calculate the emissions for virgin production of aggregate.
Step 2: Calculate the emissions associated with processing and delivering a comparable
amount of recycled concrete to be used in place of virgin aggregate.
Step 3: Calculate the difference in emissions between recycled and virgin scenarios.
Step 1. Calculate the emissions for virgin production of aggregate.
For project 1
Based on the table 4.12 and the amount of concrete waste, the calculation as following:
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64
Table 4.12: Process Energy Data for the Production of One Ton of Virgin Aggregate (EPA 1998)
Fuel
(a)
(b)
(c)
Combustion
energy
Million Btu/ton
Precombustion energy
Million Btu/ton
Total energy
Million Btu/ton
Process energy
Coal
0.0007
0.00000
0.0007
Distillate fuel oil
0.0248
0.0046
0.0293
Residual fuel oil
0.0024
0.0004
0.0028
Gas
0.0029
0.0004
0.0033
Gasoline
0.0003
0.0015
Electricity
0.0013
0.0110
0.0000
0.0110
Total
0.0429
0.0056
0.0486
84 m3 = concrete waste
1767 kg/m3 * 84 m3 = 148428 kg (total aggregate waste)
148.428 ton * 0.0486 million btu/ton =7.2 million Btu
7.2 million btu / 0.0009478 million btu = 7596.5 MJ ~ 7.6 GJ
Project 2
20 m3 = concrete waste
1827 kg/m3 * 20 m3 = 36540 kg (total aggregate waste)
36.54 ton * 0.0486 million btu/ton =1.77 million Btu
1.77 million btu / 0.0009478 million btu = 1867.5 MJ ~ 1.86 GJ
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65
Project 3
20 m3 = concrete waste
1800 kg/m3 * 20 m3 = 36540 kg (total aggregate waste)
36 ton * 0.0486 million btu/ton =1.75 million Btu
1.75 million btu / 0.0009478 million btu = 1846 MJ ~ 1.84 GJ
Transportation:
For the calculation of this emission factor, we assumed that virgin aggregates
must be transported 30 miles to the end user.
Table 4.13 : Transportation Energy Consumption, million Btu/ton-mile(US,EIA,2001)
Transportation
energy
Transportation
energy
Transportatio
n
Transportation
energy
Diesel fuel
(Million btu/tonmile)
Distance
(million
btu/ton)
30
0.0610
15
0.0305
(Joule/kg-km)
Virgin aggregate
3800
0.0020
Recycle
aggregate
3800
Project 1
148.428ton aggregate * 0.0610 million btu/ton = 9 million btu
9 million btu / 0.0009478 million btu = 9552.7 MJ ~ 9.5 GJ
So that the energy required producing the virgin aggregate is:
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66
7.6 GJ + 9.5 GJ = 17.1 GJ
Project 2
36.5 ton aggregate * 0.0610 million btu/ton = 2.23 million btu
2.23 million btu/0.0009478 milion btu = 2351 MJ ~ 2.3 GJ
So that the energy required producing the virgin aggregate is:
1.86 GJ + 2.3 GJ = 4.16 GJ
Project 3
36 ton aggregate * 0.0610 million btu/ton = 2.2 million btu
2.2 million btu/0.0009478 milion btu = 2321 MJ ~ 2.32 GJ
So that the energy required producing the virgin aggregate is:
1.84 GJ + 2.32 GJ = 4.16 GJ
CO2 emission by production of virgin aggregate
Based on the information by EIA 2001, the amount of production rate for virgin
aggregate is 0.9 g for 1 Kg aggregate.
`
67
Table 4.14: Process energy emission calculation for Virgin aggregate(U.S.EIA,2001)
Million Btu
used for
aggregate
production
Process Energy
CO2 emission
(MTCE/TON)
Process
energy CH4
emission
(MTCE/TON)
3.16
0.0015
<0.0001
<0.0001
<0.0001
Distillate
Fuel
60.42
0.0293
0.0006
<0.0001
0.0006
Residual Fuel
National
Average
5.68
0.0028
0.0001
<0.0001
0.0001
Fuel Mix for
Electricity
22.61
0.0110
0.0002
<0.0001
0.0002
Coal Used by
Industry
(NonCoking Coal
1.40
0.0007
<0.0001
<0.0001
<0.0001
Natural Gas
6.74
0.0033
<0.0001
<0.0001
<0.0001
100
0.0486
0.0009
<0.0001
0.0009
Gasoline
Total
Project 1
So we have 84 m 3 wastage, and
84m3 * 1767 kg = 148428 kg aggregate
148.428 ton * 0.0009MTCE/ton = 0.133 MTCE ~ 132.5 kg
Project 2
20 m3 * 1827 Kg = 36540 kg
36.540 ton * 0.0009 MTCE = 0.03 MTCE ~ 32.6 kg
`
Total process
Percentage
of total
BTu
Fuel type
energy
emission
(MTCE/TON)
68
Project 3
20 m3 * 1800 Kg = 36000 kg
36 ton * 0.0009 MTCE = 0.032 MTCE ~ 32 kg
CO2 emission by transportation of virgin aggregate:
Based on the information by the table below, the transportation of virgin
aggregate will:
Table 4.15: Transportation Energy Emission Calculation for Virgin aggregate(US.EIA,2001)
Fuel type
Percentage of
Total Btu
Million Btu
used for
aggregate
transport
Transportation
Energy CO2
emission
(MTCE/TON)
Transport
energy CH4
emission
(MTCE/TON)
Total
transport
energy
emission
(MTCE/TON)
Diesel Fuel
100
0.1869
0.0037
<0.0001
0.0037
Total
100
0.1869
0.0037
<0.0001
0.0037
Project 1
148.428 ton * 0.0037MTCE/ton = 0.55MTCE ~ 545.5 kg
So that the total emission by CO2 for producing and transporting of virgin aggregate is:
545.5 kg + 132.5 kg = 678 kg
Project 2
36.540 ton * 0.0037MTCE/ton = 0.134 g ~ 134 kg
134kg + 32.6 kg= 166.6kg
`
69
Project 3
36 ton * 0.0037MTCE/ton = 0.133 MTCE ~ 132 kg
So 132kg + 32 kg = 164 kg
Step 2: Calculate the emissions associated with processing and delivering a comparable
amount of recycled concrete to be used in place of virgin aggregate.
Recycle:
Project 1
Based on the table 4.16
148428 kg = 148.428 ton
148.428 ton * 0.0352 million btu/ton= 5.22 million btu
1 mega joule = 0.0009478 million btu
5.22 million btu/ 0.0009478 = 5507 MJ ~ 5.5 GJ
Project 2
36.540 ton * 0.0352 million btu/ton= 1.28 million btu
1.28 million btu/ 0.0009478 = 1350 MJ ~ 1.35 GJ
Project 3
36 ton * 0.0352 million btu/ton= 1.26 million btu
1.26 million btu/ 0.0009478 = 1329.5 MJ ~ 1.33 GJ
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70
Transport:
Project 1
Based on the table 4.16
148.428ton aggregate * 0.0305 million btu/ton = 4.5 million btu
4.5 million btu / 0.0009478 million btu = 4776.3 MJ ~ 4.77 GJ
So that the energy required recycling the waste aggregate is:
4.77 GJ + 5.5 GJ = 10.27 GJ
Project 2
36.540 ton aggregate * 0.0305 million btu/ton = 1.11 million btu
1.11 million btu / 0.0009478 million btu = 1171 MJ ~ 1.17 GJ
1.17 GJ + 1.35 GJ = 2.52 GJ
Project 3
36 ton aggregate * 0.0305 million btu/ton = 1.1 million btu
1.1 million btu / 0.0009478 million btu = 1158.5 MJ ~ 1.16 GJ
1.16 GJ + 1.33 GJ = 2.49 GJ
As we can see, by recycling of wasted concrete can be useful by almost 2 times
more saving energy than producing virgin aggregate.
`
71
Table 4.16: Process Energy Emissions Calculations for Recycled Aggregate(US.EIA2001)
(a)
Fuel Type
Diesel Fuel
Total
Percent
of Total
Btu
(b)
Million Btu
used for
Aggregate
transport
(=0.0352 x a)
(c)
Fuel-specific
Carbon
Coefficient
(MTCE/
Million Btu)
(e)
Transport Energy
CO2 Emissions
(MTCE/Ton)
(=b x c)
(g)
Total
Transport
Energy
Emissions
(MTCE/Ton)
(=e + f)
50%
0.0176
0.0199
0.0003
0.0004
50%
0.0176
0.0158
0.0003
0.0003
100%
0.0352
0.0357
0.0006
0.0007
CO2 emission by Recycling aggregate
Based on the table 4.16, CO2 emission by recycling the wasted aggregate is
about 0.6 g for 1 kg aggregate. So that the amount is as following:
148.428 ton * 0.0006 MTCE/ton = 0.089 MTCE~ 89 kg (project 1)
36.540 ton * 0.0006 MTCE/ton = 0.021 MTCE ~ 21 kg (project 2)
36 ton * 0.0006 MTCE/ton = 0.0216 MTCE = 21.6 kg (project 3)
CO2 emissions by transportation of recycle aggregate:
Based on the table 4.17, CO2 emission by transporting recycling the wasted
aggregate is about 1.9 g for 1 kg aggregate. So that the amount is as following:
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72
Table 4.17: Transportation Energy Emissions Calculations for Recycled Aggregate(EIA2001)
(a)
Fuel Type
Percent
of Total
Btu
(b)
Million Btu
used for
Aggregate
Production
(=0.0935 x a)
(c)
Fuel-specific
Carbon
Coefficient
(MTCE/
Million Btu)
(e)
Transport Energy
CO2 Emissions
(MTCE/Ton)
(=b x c)
(g)
Total
Transport
Process
Energy
Emissions
(MTCE/Ton)
(=e + f)
Diesel Fuel
100%
0.0935
0.0199
0.0019
0.0019
Total
100%
0.0935
n/a
0.0019
0.0019
Project 1
148.428 ton * 0.0019 MTCE/ton = 0.282 MTCE ~ 282 kg
So the total amount of CO2 emission by transportation and recycling aggregate is as
following:
282 kg + 89 kg = 371 kg
Project 2
36.540 ton * 0.0019 MTCE/ton = 0.069 MTCE ~ 70 kg
Total amount of CO2 emission by transportation and recycling aggregate:
70 kg + 21 kg = 91 kg
Project 3
36 ton * 0.0019 MTCE/ton = 0.068400 g ~ 68.4 kg
Total amount of CO2 emission by transportation and recycling aggregate:
68.4 kg + 21.6 kg = 90 kg
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73
The above calculations show the benefit of recycling of concrete waste to
displace virgin aggregate by comparing the emission of both virgin aggregate production
and recycling aggregate. In these comparison transportation also included which
assumed 30 miles for virgin aggregate and 15 miles for recycled aggregate. There are 3
tables for 3 different construction sites. Based on the table 4.18, construction no 1 by
84m3 concrete waste need 7.6GJ embodied energy to produce this amount of aggregate
as a virgin aggregate but if this amount of aggregate after the waste tried to be recycle, it
seems by 5.5 GJ embodied energy has reasonable amount compared to produce it from
virgin. Table 4.19 and table 4.20 show that Construction No 2 and No 3 which are
almost the same by 1.86GJ embodied energy for production of virgin aggregate and 1.35
GJ for recycling process, because they have the same wastage (level of 20m3).For the
energy consumed by transportation factor, as shown in table 4.18 the recycling has more
benefits with two times more saving than producing. Tables 4.19 and table 4.20 also
show the same finding in which 2.3 GJ energy consumed for transportation of aggregate
to the place while another 1.17GJ was for recycling. It also the same for the CO2
emission by transportation where it produced approximately 1.5 to 2 time more saving
in CO2 emission.
`
74
Table4.18: Comparing recycling and virgin aggregate (84m3)
Wastage for project 1
Energy emission by
Virgin aggregate
Recycle aggregate
7.6 GJ
5.5 GJ
9.5 GJ
4.77 GJ
132.5 kg
89 kg
545.5 kg
282 kg
Production
Energy emission by
Transportation
CO2 emission by production
CO2 emission by
Transportation
`
75
Table4.19: Comparing recycling and virgin aggregate (20m3)
Wastage for project 2
Energy emission by
Virgin aggregate
Recycle aggregate
1.86 GJ
1.35 GJ
2.3 GJ
1.17 GJ
32.6 kg
21 kg
134 kg
70 kg
Production
Energy emission by
Transportation
CO2 emission by production
CO2 emission by
Transportation
`
76
Table 4.20: Comparing recycling and virgin aggregate (20m3)
Wastage for project 3
Virgin aggregate
Recycle aggregate
Energy emission by
1.84 GJ
1.33 GJ
2.32 GJ
1.16 GJ
32 kg
21.16 kg
132 kg
68.4 kg
Production
Energy emission by
Transportation
CO2 emission by production
CO2 emission by
Transportation
`
77
18
16
14
12
10
8
6
4
2
0
Energyemissionby
Production
Energyemissionby
Transportation
Total(GJ/M3)
Figure 4.1: Energy comparisons between Virgin and Recycled Aggregate
1600
1400
1200
1000
800
Total(kg/M3)
600
400
200
0
CO2emissionby
Transportation
CO2emissionby
production
Figure 4.2: CO2 emissions between Virgin and Recycled aggregate
`
78
4.11.2 Land filling
Typically, the emission factor for land filling is comprised of four parts: landfill
CH4, CO2 emissions from transportation and landfill equipment operation, landfill
carbon storage, and avoided utility emissions. However, as with other inorganic
materials for which EPA has developed emission factors, there are no CH4 emissions, or
avoided utility emissions associated with land filling concrete. Studies have indicated
that over time, the cement portion of concrete is capable of absorbing CO2. (Gadja, John
2001) .based on the CO2 emission which occur by the time elapsing after concrete land
filling, it could be difficult to obtain the data for this impaction so that, these emissions
were estimated at 0.01 MTCE per ton of concrete land filled( Landfill data obtained
from FAL 1994). based on the same underlying data that was used for other materials in
the EPA 2002 report.
Project 1
84 m3 (total waste concrete) = 2.3 ton
2.3 ton * 0.01 MTCE = 0.023 MTCE
0.023 MTCE * 84 m3 = 1932 kg
The total emission is 1932 kg
Project 2
20 m3 (total waste concrete) = 2.3 ton
0.023 MTCE * 20 m3 = 460 kg
Project 3
20 m3 (total waste concrete) = 2.3 ton
0.023 MTCE * 20 m3 = 460 kg
`
79
CHAPTER V
CONCLUSION
5.1
Introduction
This chapter is intended to give an overall conclusion of this study. The aim and
objectives of this study which established earlier would be confirmed in this chapter by
reviewing the information gathered through the literature review and questionnaire
survey. None the less, there are some recommendation are given to readers for further
research and reading.
5.2
Conclusion
This study shows that it is the raw material production (concerning GWP)
together with the transportation operations and concrete plant operations that are the
`
80
main contributors to the environmental impact of concrete .In concrete; cement is the
most energy intensive of all the materials used. Even though it only makes up about 10
to 20 percent of an entire concrete mixture, it is responsible for up to 70 percent of the
total embodied energy and 95% of the carbon dioxide emissions of concrete. Cement is
the most energy intensive, and therefore has the greatest environmental impact, of the
constituent materials of concrete. However, cement only represents 10% to 15% of the
total mass of concrete.
Based on the finding in recycling and producing virgin aggregate, it shows that
Recycling of wasted concrete can be useful by 1.5 to 2 times more saving energy and
CO2 emission than producing virgin aggregate
5.3
Recommendation for future research
Although land filling is the easiest and safe way to release the wasted concrete, it
has considerable disadvantage which appear long years after land filling. Based on the
limited time for doing this research, the finding due to land filling is not sufficient based
on the following reason:
5.3.1 Concrete Reabsorbs CO2
During the life of a concrete structure, the concrete carbonates and absorbs the
CO2 released by calcinations during the cement manufacturing process. Once concrete
`
81
has returned to fine particles, full carbonation occurs, and all the CO2 released by
calcinations is reabsorbed. A recent study indicates that in countries with the most
favorable recycling practices, it is realistic to assume that approximately 86% of the
concrete is carbonated after 100 years. During this time, the concrete will absorb
approximately 57% of the CO2 emitted during the original calcinations. About 50% of
the CO2 is absorbed within a short time after concrete is crushed during recycling
operations.
`
82
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88
APPENDIX A
Calculations and LCI data for cement production
The amounts of the various ingredients utilized in cement production have been
collected from Cement AB’s report. The three main ingredients are limestone, sand and
gypsum. Information used in calculations for LCI data for cement production is
presented below.
Table A.1 Main ingredients for the production of 1 Kg Cement
Lime stone
1.4 Kg
Sand
70 g
Gypsum
30 g
The impact of sand production is the same as that of gravel production (Table
A.4). Fuels used in the production of cement are coal and coke. The emissions from the
use of these fuels are presented as a total sum in the production of the cement (Table
A.2) at the factory. Emissions from the production and distribution of these fuels are
calculated separately and both coal and coke are regarded as coal (Table A.2).
Transports of the raw material to the location of cement production are not taken
into consideration since most of the raw materials are usually situated in the vicinity of
the cement production facility. LCI data for cement production is presented in Table A.2
`
89
Table A.2 LCI data for the production of 1 kg cement
Limestone
Sand
Gypsum
Production of cement
Total
Energy
Coal
2.89E-06
Oil
3.14E-05
1.88
3.14E-05
Coke
0.50
Natural gas
6.73E-07
Peat
Diesel
Biofuel
0.506
6.73E-07
3.26E-07
0.0249
1.88
3.26E-07
5.01E-04
0.0254
3.26E-06
3.26E-06
Car tyres
0.416
0.416
Bone meal
0.0109
0.0109
0.432
0.478
704
714
Electricity
0.0458
7.23E-05
2.26
0.00220
4.80E-04
Emissions to air (g)
CO2
`
0.0394
90
Table A.3 LCI data for the production of 1 kg gypsum
Unit
Material use
Explosives
g
0.2
Gypsum
kg
1
Energy use
Electricity
MJ
1.59E-02
Diesel
MJ
1.66E-02
CO
g
4.98E-03
CO2
g
1.31E+00
HC
g
3.45E-03
NOx
g
2.26E-02
Particles
g
1.67E-03
g
2.56E-03
Emissions to air
SO2
`
91
Table A.4 LCI data for the production of 1 kg gravel (sand)(StrippleStripple, 2001)
UNIT
Energy
Biomass fuel
MJ
1.08E-04
Oil
MJ
0.00104
Peat
MJ
Coal
MJ
9.59E-05
Natural gas
MJ
2.23E-05
Uranium
MJ
0.00348
Hydropower
MJ
0.00113
Electricity
MJ
0.0024
CO2
g
0.0728
SO2
mg
0.0467
NOx
mg
0.597
Dust
mg
0.0231
CO
mg
0.0736
HC
mg
0.044
CH4
mg
0.376
1.08E-05
Emissions to air
`
92
Table A.5 LCI data for the production of 1 kg chemical admixture
Unit
load
Raw Material
crude oil (feedstock)
kg
0.091
natural gas (feedstock)
kg
1E-04
water
kg
7.4
Energy
Coal
MJ
1.7
Crude oil
MJ
3.2
Natural gas
MJ
8.2
Electricity
MJ
2.9
CO2
kg
0.69
CO
g
2.1
HC
g
2.2
CH4
g
1.2
Methanol
g
1.1
NOx
g
3.5
SOx
g
6.6
Emissions to air
Calculations and LCI data for concrete mixing
In the fabrication of concrete only electricity is used, 32.7 MJ/m3, while oil is used for
heating the plant, 1.5E-05 MJ/m3 concrete.83 Information used in calculations for LCI
data for concrete mixing is presented below.
Oil
Energy content of oil: 39 GJ/m3 (average)
`
93
Emissions for oil production, distribution and usage are taken from Table B.1.
Electricity, Swedish average
Emissions for electricity production are taken from Table B.1.
Table B.1 LCI data for the mixing of 1 m3 of concrete
Unit
Energy
Oil
MJ
1.51E-05
Electricity
MJ
32.7
Emissions to air
`
NOx
g
0.491
SOx
g
0.426
CO
g
0.589
HC
g
0.0949
CO2
kg
0.256
CH4
g
1.6
NH3
g
0.0072
94
LCI data for Transports
B.3 the transportation vehicles used in the study is heavy trailers
Heavy trailer
Unit
total weight
ton 60
total load
ton 40
Diesel Mk1
l/10km
4.9
MJ/tkm
0.6
%
70
Energy demand (fossil)
Load capacity
Emissions to air per tkm
CO2
g
48
CO
g
0.045
B.4 the transportation vehicles used in the study is medium heavy trailers
Medium Heavy Trailer
Unit
total weight
ton
24
total load
ton
14
Diesel Mk1
l/10km
3.5
MJ/tkm
1.9
%
70
CO2
g
0.14
CO
g
0.13
Energy demand (fossil)
Load capacity
Emissions to air per tkm
`
95
B.5 Process Energy Emissions Calculations for Virgin Aggregate (U.S.EIA,2001)
(a)
Fuel Type
Percent
of Total
a
Btu
(c)
Fuel-specific
Carbon
Coefficient
(MTCE/
b
(e)
Process Energy
CO2 Emissions
(MTCE/Ton)
(=b x c)
Million Btu)
(g)
Total Process
Energy
Emissions
(MTCE/Ton)
(=e + f)
Gasoline
3.16
0.0015
0.0192
<0.0001
<0.0001
Distillate Fuel
60.42
0.0293
0.0214
0.0006
0.0006
Residual Fuel
5.68
0.0028
0.0214
0.0001
0.0001
0.0110
0.0158
0.0002
0.0002
0.0007
0.0251
<0.0001
6.74
0.0033
0.0138
<0.0001
<0.0001
100
0.0486
n/a
0.0009
0.0009
National Avera
Fuel Mix for 22.61
Electricity
Coal Used by
1.40
Industry (NonCoking Coal)
Natural Gas
Total
`
(b)
Million Btu
used for
Aggregate
Production
(=0.0352 x a)
96
A
Appendix
B
Faculty
F
of civil
c
engineeering
University
U
T
Technology of Malaysiaa
Skud
dai,Johor
PRIV
VATE AND COFIDEN
NTIAL
SUR
RVEY QUE
ESTIONNA
AIRE
R
RESEARCH
H TITLE:
Energ
gy and CO22 Emission Evaluation
E
of Concretee Waste
OBJECTIV
VE:
i.
To determine
d
the amount off concrete waaste in construction sites
ii.
To estimate
e
the amount of energy useed and CO2 emission for
f productioon of
concrete
P
PROFILE
OF
O STUDENT:
N
Name:
Pooriia Rashvandd
C
Course:
Masster in Consttruction Mannagement
S
Supervisor:
Dr
D Khairulzaan
E
Email:
poory
ya_rashvandd@yahoo.com
m
H
H/phone:
0177804523
`
`
97
All data compiled are solely for academic purposes would really appreciate if you could
complete the questionnaire within 5 days. I shall collect back the questionnaire once
completed. Thank you for your cooperation and interest in making this research success.
Section A
This section aims to obtain information on the background of the respondent.
Profile of respondent:
Name of company
Company stamp
Designation
Type of construction:
Concrete frame design
Steel frame design
`
98
Section B
The question will refer to amount of concrete which ordered.
Different order for concrete:
Beams:
Density (kg/m3)
Grade:
Cumulative quantity of ordering (m3)
Cumulative work done (m3)
Columns:
Density:
Grade:
Cumulative quantity of ordering (m3)
Cumulative work done (m3)
Slab:
Density:
Grade:
Cumulative quantity of ordering (m3)
`
Cumulative work done (m3)
99
Section C
Design mix
Density:
Ingredients in terms of percentage or Kg for 1m3
Percentage %
Ingredients
Aggregate
Fine aggregate
Sand
Rock
Coarse aggregate
Gravel
Cement Aggregate
Water
Admixtures
Mineral admixtures
Slag
Fly ash
Silica fume
Chemical admixtures Super plasticizer
`
Weight(kg)