ABSTRACT
Energy benchmarking and carbon footprint reduction opportunities in Portland cement
manufacturing processes in Nigeria are presented. Life Cycle Assessment (LCA) is
used to estimate the environmental impact of three cement manufacturing processes in
Nigeria. The energy consumption of the cement manufacturing processes are evaluated
using energy Benchmarking and Energy Savings Tool for cement (BEST-Cement).
BEST-Cement evaluates and compares the energy consumption of the cement
manufacturing processes in Nigeria to China (world largest producer of cement) and
International energy benchmark practices. Energy Conservation Supply Curves
(ECSC) were used to evaluate energy and emission reduction mitigations measures
through the application of energy efficient measures/technological changes. A list of 34
energy efficiency measures/technologies were applied as per the technological
requirement of each cement manufacturing process technology in constructing an
Energy Conservation Supply Curve (ECSC). The carbon footprint of 1 tonne of
Portland cement produced by the wet, semi-wet and dry cement manufacturing
processes in Nigeria estimated using the 100 years Global Warming Potential (GWP)
value are 871 kg of CO2 Eq, 694.45 kg CO2 Eq and 621 kg of CO2 Eq respectively per
tonne. The average technical potential for thermal and electrical energy savings for the
three cement manufacturing processes when compared to International cement
manufacturing energy benchmarks were 35% and 39.27%. When compared to Chinese
cement manufacturing energy benchmarks, the average technical potential for thermal
and electrical energy savings were 29% and 25.56% respectively. Results from the
Energy Conservation Supply Curve model, indicates that the cost-effective energy
efficiency potential for the wet cement plant in 2010 is 235,038 GJ/year, which
accounts for 6.87% of primary energy, for the semi-wet process it is estimated at
237,913GJ/year which accounts for 8.89% of primary energy and the dry cement plant
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estimated to be 374,055GJ/year which accounts for 14% of primary energy. The
reduction in carbon footprint emissions due to use of selected energy efficiency
measures/technological changes applied to the Conservation Supply Curves estimates
that a total of 12,362 tCO2Eq per year, 12,694 tCO2Eq per year and 20,502 tCO2Eq per
year are achieved for the wet, semi-wet and dry cement manufacturing processes in
Nigeria respectively.
TABLE OF CONTENTS
Cover page ……………………………………………….………….…….……….…i
Title Page………………………………………………….….………………………ii
Approval………………………………………………………………………………iii
Certification ……………………………………………….….……………………..iv
Dedication…………………………………………………………………………..…v
Abstract…………………………………………………..……….………………….vi
Acknowledgement…………………………………………..……………..…………viii
Table of Content…………………………………….………..……………………….ix
List of Figures…………………………………………………..…………..……….xii
List of Tables……………………………………………………………………..…xiv
CHAPTER ONE: INTRODUCTION………………………………………………1
1.1 Introduction………………………….………………………………….…………1
1.1.1 Cement………………………….……………………………….…………..1
1.1.2 Cement Standards…………………………….……………………,……….2
1.1.3 Cement manufacturing in Nigeria……………………………………..……4
1.1.4 Cement Manufacturing Process and Technologies……………….….……..5
1.2 Objectives…………………………………………………………….……….……8
1.3 Significance of Study……………………………………….……………….…….8
1.4 Scope of Study……………………………………………………………….……9
1.5 Limitations……………………………………………………………………….10
CHAPTER TWO: LITERATURE REVIEW…………………………………….11
2.1 Description of cement (Portland) production processing steps…………………………11
2.1.1 Raw material preparation………………………………………………….11
2.1.2 Clinker making (Pyro-processing or burning process step)……………….12
2.1.3 Cement making (cement finish grinding process step)……………………14
2.2 Cement manufacturing technologies…………………….……………………….14
2.2.1 Wet cement manufacturing process………………………………….…….15
2.2.2 Semi-wet/ semi-dry cement manufacturing process……………….……….15
2.2.3 Dry cement manufacturing process………………………………….……..16
2.3 Cement CO2 and GHG emission sources……………………………….….……..16
2.3.1 Direct GHG emissions from calcination……………………………..……17
2.3.2 Direct GHG emissions from fuel use…………………………………….…19
2.3.3 Direct GHG emissions from electricity……………………………….…..20
2.4 Life Cycle Assessment…………………………………………………..…………20
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2.5 Carbon Footprint………………………………………………………………….22
2.5.1 Process Analysis……………………………………………………………24
2.5.2 Environmental Extended Input Output Analysis……………………………24
2.5.3 Hybrid Analysis……………………………………………………………25
2.6 Energy Benchmarking of Cement Production Process…………………………..25
2.7 Energy Conservation Supply Curve…………………………………………….…27
2.8 Assessment of Portland cement carbon footprint……………………………….….27
CHAPTER THREE: METHODOLOGIES……………………………………….32
3.1 Description of cement manufacturing plant……………………………….……..32
3.2 Conversion and assumptions…………………………………………….……….36
3.3 Energy benchmarking methodology……………………………………………. 37
3.4 Methodology for cement carbon footprint accounting…………………………..40
3.4.1 Establish the scope…………………………………………………………41
3.4.2 Boundary setting……………………………………………………………41
3.4.3 Collection of data…………………………………………………………..42
3.4.4 Allocation…………………………………………………………………..42
3.4.5 Assessing Uncertainty and Assessing data quality…………………………42
3.4.6 Calculating inventory result………………………………………………..45
3.5 Methodology for cement carbon footprint reduction…………………………….46
3.5.1 Cost of Conserved Energy………………………………………………….47
3.5.2 Cost Carbon Reduction……………………………………………………..47
3.6 Energy Efficient Measures and Technologies for reducing energy consumption
and carbon footprint of Cement………………………………………….…………..49
CHAPTER FOUR: RESULTS AND DISCUSSION………………….………….51
4.1 Result…………………………………………………………………………….51
4.2 Energy Benchmarking………………………………………………….…………55
4.1.1 Cement manufacturing process electrical energy consumption….…………56
4.1.2 Cement manufacturing process thermal energy consumption………………59
4.2 Carbon footprint……………………………………………………………….….62
4.2.1 Cement manufacturing carbon footprint process map………………………62
4.2.2 Cement manufacturing process carbon footprint mitigation
measures/technologies……………………………………………………… 65
4.2.2.1 Wet cement manufacturing process Energy Conservation Supply
Curve and carbon footprint
reduction………………………………………………………………65
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4.2.2.2 Semi-wet cement manufacturing process Energy Conservation Supply
Curve and carbon footprint reduction…………………………………68
4.2.2.3 Dry cement manufacturing process Energy Conservation Supply
Curve and carbon footprint reduction………………………………….71
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION………………75
5.1 Conclusion………..………………………………………………………………75
5.2 Recommendation…………………………………………………………………77
REFERENCE………………………………………………………………………………………………79
APPENDIX………………………………………………………………………….85
CHAPTER ONE
INTRODUCTION
1.1 Introduction
Climate change is increasingly being recognized as a major global challenge, and
many organizations and individuals are actively trying to quantify their impact and also
reduce Greenhouse Gas (GHG) emissions due to their activities (Doyle, 2009). It is widely
accepted that products and services that human beings utilize indirectly or directly generate
GHG emissions. The GHG emissions from anthropogenic sources are on the rise and thus
warming up the planet causing adverse change in weather conditions and patterns around
the world (GHG Schemes Addressing Climate Change, 2011). The extensive use of fossil
energy resources in world manufacturing industry contribute significant amount of GHG
emissions to the environment (World Energy Resources, 2013).
One of such manufacturing process that contributes to the generation of GHG
emission is cement manufacturing. Cement manufacture is a major mineral commodity
industry and cement production process is a highly energy intensive process (Ohunakin et
al, 2012). The energy consumed by world cement industry is estimated at about 2% of the
global primary energy consumption, which is equal to 5% of the total world industrial
energy consumption (Worrell et al, 2001). The world cement industrial sector is believed
to emit about 5% – 7% of the world total CO2 anthropogenic emissions (Schneider et al,
2011).
1.2 Cement
The British Standard (EN 197-1:2000, 2004) for cement defines cement as a
hydraulic binder, i.e. a finely ground inorganic material which, when mixed with water,
forms a paste which sets and hardens by means of hydration reactions and processes and
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which, after hardening, retains its strength and stability even under water. Cement is mostly
grey in colour and it is used majorly as a bonding agent in production of concrete: concrete
is a mixture of inert mineral aggregates, e.g., sand, gravel, crushed stones, and cement. It
is used majorly for civil construction. Portland cement is the most popularly and commonly
cement in use in the world (Bell, 2007).
Generally there are two types of Portland cement, they are the Ordinary Portland
Cement (OPC) and the Blended Cement (BC), which is available as slag or Portland
Pozzolana cement. (PPC). The Ordinary Portland cement contains mixture of clinker and
gypsum ground to a very fine powder while the BC is manufactured by blending a mixture
of Ordinary Portland cement with Pozzolana materials (Fly Ash) to form PPC or with slag.
The mixing proportions of OPC and the Pozzolana materials or slag is not less than 15%
and not more than 35% by weight of cement (Pofale and Wanjari, 2014).
1.2.1 Cement Standards
Cement standards vary considerably with regional and climate conditions across
the globe, this is due to the type of raw materials available, economic and industrial
development of a nation .This has led to significant variations in composition and national
standards of cement made in different countries. There are two major standards, they are
the C150 of American Society for Testing and Materials (ASTM) and BS EN197-1:2000
of the British Standards Institution (BSI) standards (Yahaya, 2009). The BS EN 197-
1:2000 describes 27 types of cement which are divided into 5 groups, as shown in Table
1.1
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Table 1.1 Cement Types
Types of Cement Clinker % Other Constituents
CEM I Portland 95 – 100
CEM II Portland – slag 65 – 94 Blast furnace slag
Portland – silica 90 – 94 Silica fumes
Portland – Pozzolana 65 – 94 Pozzolana
Portland – fly ash 65 – 94 Fly ash
Portland – burnt shale 65 – 94 Burnt Shale
Portland – limestone 65 – 94 Limestone
Portland – composite 65 – 94 Additives mix
CEM III Blast – furnace 5 – 64 Additives mix
CEM IV Pozzolanic 45 – 89 Additives mix
CEM V Composite 20 – 64 Additives mix
British Standard EN 197-1:2000, (2004).
Nigeria cement industry majorly produces Ordinary Portland Cement (OPC) and
they are regulated by the Standards Organization of Nigeria (SON) (Clean Development
Mechanism, 2006). SON grades Ordinary Portland cement types available in the country
under a new regulatory regime which is tagged “NIS 444-1” summarized in the Table 2.2
Table 1.2 The Standard Organization (SON) Portland cement grading “NIS 444-1”
No: TYPE USE/APPLICATION REMARKS
1 CEM I & II
32.5R
This grade is only to be used for
finishing works in a building such as
plastering.
This grade is also
called 32.5N or 32.5. It
is also the lowest grade
2 CEM II
42.5R
This grade will be used for molding
blocks and casting works such as
columns, beams and slabs
This grade is also
called 42.5N or 42.5
3 CEM I 52.5R This grade will be used for bridge
construction.
This grade is also
called 52.5N or 52.5
Franca (2014)
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These grading numbers indicates the minimum compressive strength gained by the
cement-sand mortar mix in 28 days. 32.5 Grade signifies that 28 days strength of the
cement will not be less than 32.5 N/mm2 and similarly for other grades as well (Rao et al.,
2010).
1.2.2 Cement manufacturing in Nigeria.
In Nigeria, the cement manufacturing sector has been steadily growing coupled
with the aggressive privatization embarked upon by the Federal Government of Nigeria.
Data obtained from the Cement Manufacturers Association of Nigeria (CMAN) shows
cement plants in Nigeria in Table 2.3 as at 2009.
Table 1.3 Cement plant locations, capacities and cost of installation
Company Name Location Production
Capacity(tonnes)
Cost of
installation/Expansion(USD)
Lafarge WAPCO Ewekoro 2,000,000 130,000,000
Lafarge WAPCO Shagamu 1,000,000 NA
Lafage WAPCO Lakatabu 2,000,000 600,000,0000
Dangote Cement Grp Ibese 6,000,000 1,020,000,000
Dangote Cement Grp Obajana 6,000,000 1,200,000,000
Dangote Cement Grp Obajana 5,000,000 1,000,000,000
AVA Cement Edo 300,000 NA
Benne Cement Benue 3,000,000 400,000,000
Dangote Cement Grp Benue 1,000,000 200,000,000
Unicem Calabar 2,500,000 840,000,000
Ashaka Cement Gombe 1,000,000 150,000,000
Source: Bafuwa, 2011. NA = Not available.
In 2014, Nigeria became the largest cement producer and consumer of cement in
the Sub-Saharan Africa region, with an estimated production capacity and consumption
rate per annum of 28.3 million MT and 18 million MT respectively (Aithnard, 2014).
5
Dangote Cement Plc an indigenous company is the largest producer of cement in Africa
with cement plants spread across the continent, followed by Lafarge Cement Plc in
production capacity. Based on a report by Renaissance Capital (Sterling, 2013), a leading
investment bank in Nigeria, Nigeria is set to maintain this position as investors invest over
the medium term. With the current trend of investment it is predicted that cement
production capacity in the country will peak in 2020 at just under 50 million tonnes per
annum.
1.2.3 Cement manufacturing processes and technologies
Cement production processes were developed to achieve complete burning of
cement raw materials majorly limestone (CaCO3) in a process called calcination (Worrell
and Galitsky, 2004). Calcination is the process of decarbonising and sintering of limestone
and other additives (shale, iron ore e.t.c) at a very high temperature usually around 1400 o
C to produce clinker. Clinker is the major material used in production of cement. The
calcination and sintering of limestone and other additive takes place in a kiln system and
the calcination process is a huge source of GHG emission in cement production process
(Huntzinger and Eatmon, 2009).
Different manufacturing technologies have been developed to achieve complete
burning of limestone and other addictive, with the aim of reducing energy consumption
and GHG emissions from the process. They are categorised as the wet cement
manufacturing process, semi-wet/semi-dry cement manufacturing process and dry cement
manufacturing process (Nisbet and VanGeem, 1997). Three of the cement manufacturing
processes mentioned above are available and in full operation in Nigeria.
6
The differences that set the wet, semi-wet and dry cement production process apart,
can be observed in cement raw material preparation method prior to calcination in the kiln.
In the wet process, 27% to 38% w/w of water is added to clinker raw materials to form
thick slurry and same in the semi-wet process 11% to 17% w/w of water is added to clinker
raw material. The water addition is in percentage of the dry raw materials used. The dry
process is based on the preparation of a fine powdered clinker raw materials through
grinding, after which the raw material is dried using the exhaust of the Kiln system. The
choice of the process is mainly based on the chemical homogeneity of the available raw
materials (Worrell and Galitsky, 2004).
With the cement market still expanding, increase in cement production in Nigeria
will invariably lead to increased energy consumption and more GHG emissions from
Nigeria’s cement industry. As such, there is a need to measure, estimate, and establish
current level of energy consumption and GHG emission from cement manufacturing
process utilized in Nigeria. The level of energy consumption and the amount of GHG
emissions from cement manufacturing processes in Nigeria, can be established through
energy benchmarking and carbon footprint estimation.
Energy utilization efficiency is a major determinant of the profitability of
manufacturing system (Fadare et al., 2010). Energy benchmarking serves as valuable tool
for improving our understanding of energy consumption pattern of manufacturing process
and helps in setting acceptable bases for comparing local energy consumption of a
particular product or system to internationally established best practices (Ruth et al., 2001).
GHG emission associated with the type of energy utilized by the cement manufacturing
process can be estimated by establishing the carbon footprint of cement.
7
Carbon footprint evaluation is an effective means of measuring the Carbon Dioxide
(CO2) and other GHG impact of a product, process or organization on the climate
(Weidmann, 2009). According to Wu (2011), it as an indicator of climate performance,
helping to identify major GHG emission sources and potential areas of improvement. When
they are calculated for products, they are called product carbon footprints. The evaluation
of the product, processes or organizational carbon footprints help government and
environmental NGOs to set acceptable safety limits by which cement factories should
operate. It also give the collective citizenry an opportunity to know the carbon content of
products they consume and therefore take collective decision on production, utilization and
eventual disposal of such product.
The energy and carbon footprint reduction opportunities in cement
manufacturing processes can be explored through the construction of Conservation Supply
Curves (CSCs). Conservation Supply Curves (CSCs) were developed to describe and
compare the different options for energy conservation in a transparent way (Fleiter et al.,
2009). CSC is a tool for investigating the technical potential and economics of the energy
conservation measures. The use of Conservation Supply Curves in selecting energy
efficiency measures and technological changes to apply in reducing energy consumption
in cement industries across the globe are well studied (Hasanbeigi et al., 2013). Thirty four
energy efficiency measures/technologies are identified and used in constructing the
Conservation Supply Curves. The quantity of GHG emissions reduced and the cost of
implementing such energy efficiency measures/technologies is reported in the study.
8
This work will study the energy consumption pattern of the cement manufacturing
processes and carbon footprint of cement manufacturing processes in Nigeria.
1.5 The objectives are to:
1) Benchmark energy consumed in the production of 1 tonne of Portland cement by
the wet, semi-wet and dry cement manufacturing process in Nigeria and compare
energy consumption with cement manufacturing energy benchmark practices
reported in China and the World.
2) Generate carbon footprint process map and identify the process with highest carbon
footprint, thus the highest technical potential for improvement.
3) Apply the concept conservation supply curve in selecting carbon footprint
mitigating energy efficiency measures / technologies that cut across the three
manufacturing process under study.
4) Estimate the average GHG emission from the three cement manufacturing process
in Nigeria.
1.6 Significance of study
This study evaluates the carbon footprint of Portland cement produced in Nigeria
by conducting a Life Cycle Assessment (LCA) of cement manufacturing processes, making
use of data from comprehensive cement production report from the wet, semi wet and dry
cement manufacturing processes under the operation of Lafarge Cement Plc in Nigeria.
As emissions from our cement plants increase due to production increase or system
inefficiencies, there is a need to quantify and compare current performances in order to
determine if our production systems are functioning optimally. Calculating organisational
9
or product energy use and carbon footprint is one way of establishing performance, and the
first step towards improvement.
This study provides a simplified eight step carbon footprint reporting and
accounting standard adapted from the Greenhouse Gases Product Accounting and
Reporting Standard, of World Resource Institute (WRI) and World Business Council for
Sustainable Development (WBCSD). The study also benchmarks the energy consumed in
each of cement processing step. Completing an energy benchmark exercise helps a
company or organization understand where they are as a company or organization on their
energy consumption level, where they want to be and help establish major deliverables and
milestones that will help reduce energy consumption level to compete favourable.
1.7 Scope of study
This study will consider wet, semi-wet and dry cement processes for cement
manufacturing in Nigeria. The following cement processing steps are identified; Quarry
and Crushing process step, raw meal (grinding and homogenization) process step, pyroprocessing
process step and cement finish grinding process step. They are analyzed under
the wet, dry and semi-wet cement manufacturing process.
The current energy consumption by the three cement manufacturing processes will
be benchmarked and compared against the energy benchmarks of world largest producer
of Cement “China” and World energy benchmarks for cement manufacturing processes.
The Energy Benchmarking and Energy Savings Tool (BEST) for cement is a process based
tool developed by the Lawrence Berkeley National Laboratories used to benchmark current
technology performance (Hasanbeigi et al., 2012).
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The carbon footprint emitted per tonne of Portland cement produced from the three
cement manufacturing process mentioned are established for current cement
manufacturing technologies. The carbon footprint of cement produced by processes
mentioned above are carried out by bottom-up process analysis method of estimation. The
GHG Protocol for Product Accounting and Reporting Standard and the Publicly Available
Specification (PAS) 2050 created by the British Standard Institute (BSI) and co-sponsored
by Carbon Trust, are standards adhered to in establishing the carbon footprint of cement.
The Conservation Supply Curve (CSC) is used in selecting energy efficiency
measures/technologies which would be applied across cement production processing steps
of manufacturing processes enumerated above. A Microsoft Excel Spreadsheet is used in
conducting Life Cycle Assessment analysis and computations. Energy and emission
conversion factors were obtained from the National Renewable Energy Laboratory’s US
Life Cycle Inventory Database (NREL) and are applied in conducting life cycle assessment
of cement manufactured by the afore mentioned processes.
1.8 Limitation of studies.
There are five processing steps identified in the manufacturing of cement. The
cement packaging process step is not included in the study. The scope 3 emissions are not
estimated in the work, the cost of electricity, cost of fuel and cost of carbon reduction
technologies utilized are reported in Naira. The fuel used in both wet and dry cement
manufacturing process in the pyro-processing process step is natural gas and the fuel used
in the semi-wet pyro-processing process step is fuel oil. The base year of analysis for the
study is 2010.
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