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Embodied Energy of Fired Bricks: The Case of Uganda and Tanzania

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This paper evaluates the embodied energy of fired/burned bricks as one of the major construction materials in East African countries. Production processes of bricks by artisans, and small- and medium-scale manufacturers are explained. Embodied energy of brick walls is also calculated and the key factors in the energy efficiency of brick kilns are discussed in detail. Low quality, high material waste and excessive energy waste during production and handling are highlighted as the major issues associate with traditional manufacturing processes of burned bricks in Uganda and Tanzania. The results reveal that small clamp kilns lose up to 3.5 times more energy through their cooling surfaces compared to large kilns. The results also indicate that clamp fired bricks are up to 60% more energy intensive than generic bricks and the embodied energy of artisan brick walls is 35% more than standard brick walls with comparable thicknesses. Improving kiln construction and production methods, educating artisan producers, replanting tress, providing alternative renewable energy sources, and design improvements to control fire intensity and air circulation in brick kilns are some of the recommendations to improve the energy efficiency and mitigate the environmental impacts of fired bricks in East African countries.
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Embodied Energy of Fired Bricks:
The Case of Uganda and Tanzania
Arman Hashemi1, Heather Cruickshank2
1 Centre for Sustainable Development, Department of Engineering, University of Cambridge, UK.
a.hashemi@eng.cam.ac.uk
2 Centre for Sustainable Development, Department of Engineering, University of Cambridge, UK.
hjc34@cam.ac.uk
Abstract: This paper evaluates the embodied energy of fired/burned bricks as one of the major construction
materials in East African countries. Production processes of bricks by artisans, and small- and medium-scale
manufacturers are explained. Embodied energy of brick walls is also calculated and the key factors in the energy
efficiency of brick kilns are discussed in detail. Low quality, high material waste and excessive energy waste
during production and handling are highlighted as the major issues associate with traditional manufacturing
processes of burned bricks in Uganda and Tanzania. The results reveal that small clamp kilns lose up to 3.5
times more energy through their cooling surfaces compared to large kilns. The results also indicate that clamp
fired bricks are up to 60% more energy intensive than generic bricks and the embodied energy of artisan brick
walls is 35% more than standard brick walls with comparable thicknesses. Improving kiln construction and
production methods, educating artisan producers, replanting tress, providing alternative renewable energy
sources, and design improvements to control fire intensity and air circulation in brick kilns are some of the
recommendations to improve the energy efficiency and mitigate the environmental impacts of fired bricks in East
African countries.
Keywords: Embodied Energy, Life Cycle Assessment, Fired Brick, Burned Brick, East Africa, Uganda, Tanzania.
14th International Conference on Sustainable Energy Technologies SET 2015
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1. INTRODUCTION
Traditional construction methods and materials have historically been a sustainable response to housing
demands in developing countries. The production methods of locally manufactured materials in Uganda and
Tanzania have more or less remained unchanged during the last few decades. Brick walling is a major
construction method in both rural and urban areas of East African countries including Uganda (UBOS, 2010).
Fired/burned brick, however has negatively affected the local environment contributing to issues such as
deforestation, desertification, air pollution, excessive soil extraction and fuel crisis (Perez, 2009; CRAterre, 2005;
World Bank, 1989). This is mainly due to the excessive energy and material waste and inefficient production
processes of burned bricks which are mainly delivered by artisan producers (World Bank, 1989). Increased use of
energy intensive materials such as concrete and burned bricks has raised concerns over the long-term
environmental impacts of such trends in East Africa. The forestry cover in Uganda, for example, has reduced by
25% from 45% coverage in 1990 to around 20% in 2005. This means an annual deforestation rate of 1.7% which
is increasing year by year. Considering the current situation, Uganda’s forests could be vanished during the next
few decades (ILO, 2010).
Environmental impacts of buildings and products are evaluated using Life Cycle Assessment (LCA) method
(Figure 1). The total carbon footprint of buildings consists of the embodied carbon of building products plus the
operational carbon which is the energy consumption during building lifetime. The majority of the embodied carbon
of building products is linked to CO2 emissions from fossil fuels during extraction and manufacturing processes of
construction materials (Anderson & Thornback, 2012). The embodied carbon of building fabrics is becoming more
important due to increasing energy efficiency requirements which reduce the operational carbon of buildings
during their lifetime.
Figure 1: Building Life Cycle
Yet, considering the negligible operational energy for space heating and cooling in East African low-income
housing, the embodied energy of construction materials is the main factor in evaluating the environmental impacts
of the low-income housing sector. The embodied energy of construction materials such as burned brick in
contrast is a major concern. Improving energy efficiency and reducing material wastes during production
processes could therefore reduce the overall greenhouse gas emission rates and mitigate the environmental
impacts of the construction industry. To this end, this study intends to evaluate the production processes of
fired/burned bricks produced by artisan, small- and medium-scale manufacturers in order to identify the key areas
for improvement.
2. METHODOLOGY
Literature review, and primary data gathered from site visits and photographic surveys in two East African
countries (Uganda and Tanzania) are the main methods of data collection for this paper. Available literature is
reviewed to assess the actual fuelwood consumption and brick sizes as well as production rates by artisans and
small- and medium-scale manufacturers in Uganda. Energy consumption and potential saving rates during
production processes are then calculated using the outcomes of the literature review. The embodied energy rates
of burned bricks and brick walling are also calculated and compared with other generic bricks/ brick walls using
the available data in the "Embodied Carbon: The Inventory of Carbon and Energy" developed by the University of
Bath (Hammond & Jones, 2011).
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3. WALLING METHODS AND MATERIALS
Figure 2 shows the main walling methods and materials during 2009/2010 in Uganda. Brick walling (either adobe
or fired) is the most common construction method in Uganda. More than 80% of houses in urban areas have brick
walls compared to around 50% in rural areas. Mud and poles walling is also very common particularly in rural
areas where more than 40% of homes are built with mud and poles. Overall, around 84% of all houses in Uganda
have brick walls compared to around 12% which are built with mud and poles (UBOS, 2010).
Figure 2: Main walling types during 2009-2010 (%).
Source of table: (UBOS, 2010)
Although burned brick is considered as a durable material, its high embodied energy makes it an environmentally
harmful material compared to other prevailing construction materials in East African countries. The very inefficient
production methods of kiln fired bricks, which mainly use local wood as their fuel, contribute to issues such as
deforestation and air pollution (Perez, 2009; CRAterre, 2005; World Bank, 1989). In fact wood is the main source
of energy particularly in rural Uganda. Two major reasons of deforestation in Uganda are cutting trees for
firewood, and charcoal, and for creating agricultural land (ILO, 2010). Fuelwood (firewood and charcoal) and
agricultural waste account for 93% of energy consumption in Uganda (The Government of the Republic of
Uganda, 2001). Around 95% of supplied wood in Uganda is used for energy generation (The Government of the
Republic of Uganda, 2001) including in the brick manufacturing industry (Figure 3). Around 91% of the required
energy for brick production is from firewood and the rest is from agricultural waste (World Bank, 1989).
Figure 3: Inefficient production processes and use of fuelwood contribute to deforestation, air pollution and fuel crisis (Uganda).
Source: The authors
4. PRODUCTION PROCESSES OF BRICK
Low quality, energy intensive traditional methods of brick production by artisans is a major concern which has
negatively affected the local environment in both Uganda and Tanzania. In the traditional production method
(Figure 3), unfired moulded bricks are prepared using local clay and water and are then left to dry out before
being fired in field kilns for 4-6 days using gradually intensified wood fire (Nyakairu et al., 2002; Batchelder et al.,
14th International Conference on Sustainable Energy Technologies SET 2015
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1985; Practical Action). Energy and material wastes are the two major issues associated with traditional
production methods of fired brick. One of the major issues is the lack of control over burning and fuel consumption
(Batchelder et al., 1985). Considerable energy is also wasted through hot exhaust gases during production
processes (World Bank, 1989).
Larger rectangular kilns and clamps can achieve better fuel efficiency thanks to lower heat losses due to the lower
volume to surface ratio. Cubic kilns are assumed to have four cooling faces (on the sides) and the heat losses
through the top and ground facing surfaces are considered separately (Practical Action). Table 1 shows the
common brick and kiln sizes in Uganda along with the cooling ratios and average wastes of different kilns. The
results of calculations reveal that a 1.5x2x2m brick kiln loses 3.5 times more energy through cooling surfaces
compared with a 6x6x4.3m kiln due to much higher cooling area/volume ratio. There is also a direct relationship
between the kiln sizes and the portion of under fired/ low quality bricks. According to World Bank (1989), around
46% of clamp fired bricks in a 3x3x3.1m kiln have low quality compared to 24% for a 6x6x4.3m clamp kiln. This is
while, according to Batchelder et al. (1985), smaller kilns provide a more uniform distribution of fire improving the
quality of final products. The latter requires more investigation to evaluate the relationships between kiln sizes and
overall waste and quality of bricks.
The average size of field kilns in Uganda is 2.4-3 metres (Batchelder et al., 1985). Despite higher fuel efficiency of
larger kilns, the width/length of country kilns should not be more than 4.5-6 metres mainly due to increases in total
fuel consumption, labour and costs. The overall process of production from clay moulding to finished product
takes around three weeks for 4,000 to 10,000 bricks. It takes an average of 5 weeks for 5 people to excavate,
mould and fire up to 9,000 bricks (Emerton et al., 1998). Around 60-75 metres of 4" to 8" dry wood (in addition to
woodchip and coffee/rice husks) is required to produce 20,000 bricks (Batchelder et al., 1985) and nearly 80% of
the required timber for fuel is provided from locally grown trees (Naughton-Treves et al., 2007).
Table 1: Brick kiln sizes and cooling ratios
Clamp
Kiln Size
(W x L x H)
(m)*
Brick/Block
Size (mm)*
Total
Surface
Area
(m2)
Cooling
Surface
Area
(m2)
Volume
(m3)
Mass
of
Bricks
(tonne)
Ratio:
Cooling
Area/Volume
Relative
Cooling
Area/Volume
energy
waste
Low
quality/
under
fired
portion*
1.5x2x2
228x111x76
20
14
6
~6.6
2.33
348%
-
3x3x3.1
290x140x90
55.2
37.2
27.9
31
1.33
199%
46%
4.5x4.5x4.3
290x140x90
117.9
77.4
87.1
98.6
0.89
133%
31%
6x6x4.3
290x140x90
175.2
103.2
154.8
180.4
0.67
100%
24%
* Source of information: (Batchelder et al., 1985; World Bank, 1989)
Firing the bricks creates a ceramic bond in a specific temperature (900-1200° C) which increases the strength of
the brick making it water resistant. Using the right amount of fuel is very important not only for fuel and cost
efficiency but also to provide the right temperature for bonding. Low temperature results in poor quality/bonding
while high temperature would either slump or melt the bricks. Controlling cold air flow thought the brick kiln is also
a key factor to make the kiln more energy efficient. Too much air circulation will cool down the bricks and wastes
the energy while too little air flow will stop the fuel from burning properly. Providing dampers and wind breaks to
control/protect the fire could greatly improve the fuel efficiency of kilns (Practical Action).
5. BRICK SUPPLIERS
Artisans, small- and medium-scale manufactures are the three major types of suppliers of bricks in Uganda (Table
2). Bricks produced by artisans take a larger share of the market compared to small- and medium-scale
manufactured bricks. The handmade bricks and blocks produced by artisans are suitable for single storey
buildings. The length of the bricks/blocks may vary between 220-295mm; the width between 100-150mm; and the
thickness between 60-130mm. The weight may also vary between 2.5 and 7.6 kg per brick/block. The final
sizes/dimensions of produced bricks and blocks in a lot may also vary greatly (World Bank, 1989). This, in fact
has been regarded as the major reason for extensive use of mortar (up to 30mm) in the construction of brick walls
(Perez, 2009).
Table 2: Brick production scales (World Bank, 1989)
Production scale
No. of bricks (per day)
Production process
Area
Artisans
1,000
Handmade, clamp fired
Rural areas
Small-scale
10,000
Semi-mechanised
Towns
Medium-scale
40,000
Mechanised
Industrialised areas with
high demand
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Firewood is mainly used by artisans for brick production. The firing period and temperature are kept low to save
as much wood as possible. This results in a rather poor quality bricks and blocks with compressive strengths of
usually lower than 8 N/mm2. Moreover the bricks which are within 300 mm from the external surfaces of the field
kilns have a very low quality and are not completely waterproof (Figure 4). The portion of the low quality bricks
produced using traditional methods varies between 25% and 45% of the entire production (World Bank, 1989).
Figure 4: Bricks within 300mm of the clamp kiln’s surfaces have a very low quality (Tanzania).
Source: The authors
Moreover, around 10-17% of materials is wasted during transportation, handling and construction processes on
site (Anderson & Thornback, 2012; World Bank, 1989) which has considerable impacts on the construction sites
(Figure 5). Material waste is in fact one of the major concerns which has negatively affected the overall
performance of the Ugandan construction industry. Improving the brick quality could, to some extent, address the
abovementioned issues.
Figure 5: High material waste during production and handeling (Tanzania).
Source: The authors
6. EMBODIED ENERGY OF FIRED BRICKS
Firewood along with coffee/rice husks are the main fuels used to produce burned bricks in Uganda and Tanzania.
The effective calorific value of wood is highly dependent on the water content of the wood and therefore
seasonality factors are significant. On average, 0.5 m3 of wood is required to produce a tonne of clamp fired brick
(World Bank, 1989). Assuming a density of 0.56 g/cm3 (Kumar et al., 2011) and a lower heating value of around
17 MJ/kg (Musinguzi et al., 2012) for Eucalyptus wood, as the major fuel for artisan brick production (World Bank,
1989), an average of 4760 MJ is required to produce one tonne of burned brick. According to the Inventory of
Carbon and Energy ICEV2.0, the embodied energy value for “General simple backed clay products” and “General
Clay Bricks” is 3.0 MJ/Kg (Hammond & Jones, 2011). This means that the energy consumptions by artisans is 1.6
times more than the required energy for the production of generic fired bricks. Table 3 summarises the fuel
consumption and embodied energy of artisan bricks.
14th International Conference on Sustainable Energy Technologies SET 2015
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HASHEMI, CRUICKSHANK _PAPER 99 6
Table 3: Embodied energy of burned bricks
Product
Required equivalent
fuelwood per tonne of
product (m3)
Energy consumption per
tonne of product (MJ)
Energy consumption
compared to “General Clay
Bricks”
General Clay Bricks
Est. 0.315
3000
100%
Artisan/ Clamp Fired Bricks
0.5
4760
159%
The embodied energy values of artisan clamp fired brick walling and general clay brick walling are also calculated
in Table 4. According to the information provided by the World Bank (1989), artisan-produced brick and block
dimensions could vary greatly from 220 to 295 mm (length), 110 to 150 mm (width), and 65 to 130 mm (height).
An average of 20mm, 1:4 cement mortar with an embodied energy of 1.1 MJ/Kg (Hammond & Jones, 2011) are
assumed to calculate the embodied energy of artisan brick walling. It should be noted that mortar thicknesses of
up to 30mm (Figure 5) is normally considered to compensate for uneven sizes of bricks in Uganda (Perez, 2009).
According to the results, the embodied energy of 300 mm and 220 mm artisan brick walls are 1619 and 1067
MJ/m2, respectively. Assuming the same brick density and mortar thickness of 10 mm for a “General Clay Bricks”
with a dimension of 215x102.5x65 mm (UK standard brick dimensions), the embodied energy of a 215 mm solid
brick wall would be 791 MJ/m2 which is around 26% lower than the embodied of energy of a 220 mm artisan brick
wall. The per square metre embodied energy of the 300 mm artisan brick wall is around 100% and 50% higher
than the embodied energy of 215 mm General Clay Brick and 220 mm artisan brick walls, respectively.
The results also indicate that walls built with smaller bricks (e.g. 220x110x65 mm) have a lower embodied energy
compared to walls constructed with larger bricks (e.g. 300x150x130 mm). This is mainly due to the considerably
lower embodied energy of cement mortar compared to fired bricks. In other words, increased mortar to brick ratio
for smaller bricks reduces the total embodied energy per square metre of walls due to the much higher embodied
energy of fired bricks compared to mortar.
Figure 5: Mortar thicknesses of up to 30mm is normal for brick walling (Uganda)
Source: The authors
Table 4: Embodied energy of brick walls
Product
Brick size,
(mm)
Wall
thickness
(mm)
Embodied
energy of
material
(MJ/Kg)
Mass per
item/littre
(Kg)
Embodied
energy of
wall per m2
Embodied
energy of
(MJ/m3)
Relative
embodied
energy of
walls per
m2
Artisan
Clamp Fired
Brick/Block
300x150x130
300
4.76
7.6
1619
5398
205%
20mm Mortar
1.11
1.65
220x110x65
220
4.76
2
1067
4849
135%
20mm Mortar
1.11
1.65
General Clay
Brick
215x102.5x65
215
3
2
791
3677
100%
10mm Mortar
1.11
1.65
14th International Conference on Sustainable Energy Technologies SET 2015
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7. CONCLUSIONS
This paper discussed the production processes of fired bricks produced by artisans and small- and medium-scale
manufactures in Uganda and Tanzania. Low quality of bricks, high material wastes and excessive energy
consumption were identified as the major issues associated with traditional manufacturing processes of burned
bricks. The results indicate that the embodied energy of artisan clamp fired brick walling per square metre of the
wall is 35% more than generic brick walls with comparable thicknesses. The embodied energy of artisan bricks is
also around 60% more than the embodied energy of generic bricks. Yet, considering the high wastes and low
quality (and therefore lower durability and shorter lifespan of clamp fired bricks) it could be argued that the overall
environmental impacts of artisan bricks is much higher than generic bricks.
The results of this paper also reveal that small kilns can lose between 1.33 and 3.48 times more energy through
their cooling surfaces compared with large clamp kilns. Up to 46% of the entire production of small kilns is also
under fired, low quality bricks which increases the wastes and breakage rate during handling, transportation and
construction on site. It should be noted that burned bricks are one of the major consumers of firewood in East
African countries contributing to issues such as deforestation, air pollution, excessive soil extraction and other
negative environmental impacts. Improving brick quality and reducing material wastes help to mitigate the
negative environmental impacts of fired bricks. Improving the production methods and energy efficiency of brick
kilns could also reduce the embodied energy of burned bricks. In this respect, following are recommended to
mitigate the environmental impacts of bricks:
a) Encourage the use of unfired bricks/ adobe instead of burned bricks;
b) Encourage replanting trees used for fuel;
c) Provide alternative renewable energy sources as a replacement of fuelwood;
d) Educate artisans to use larger rectangular clamp kilns which are more energy efficient;
e) Provide means to control fire intensity and improve air circulation in kilns to reduce energy consumption
and achieve higher quality bricks;
f) Improve the design of kilns and develop affordable heat recovery systems for field kilns to reduce heat
losses through radiation and hot exhaust gases.
8. ACKNOWLEDGMENTS
This work is funded through an EPSRC research programme, Energy and Low Income Tropical Housing, Grant
number: EP/L002604/1.
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... Pollutants associated with clamp kiln technology include particulate matter (PM), sulfur dioxide (SO 2 ), carbon dioxide (CO 2 ), nitrogen dioxide (NO 2 ), nitrogen oxide (NO), carbon monoxide (CO), metals, tropospheric ozone (O 3 ), total organic compounds (TOC) (including ethane, fluorides, methane, volatile organic compounds [VOCs], as well as hazardous air pollutants [HAPs] etc. (Akinshipe, 2013;Assadi et al., 2011;Guttikunda et al., 2013;Hashemi and Cruickshank, 2015;Skinder et al., 2014;USEPA, 1997). These pollutants have been linked to many cases of severe health problems in humans and animals, as well as damage to vegetation, agriculture and land cover (Assadi et al., 2011;Croitoru and Sarraf, 2012;Guttikunda and Khaliquzzaman, 2014;Haack and Khatiwada, 2007;Pariyar et al., 2013;Pokhrel and Lee, 2014). ...
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The quantification of atmospheric emissions from clamp kilns in the clay brick industry has met with limited success globally. The complex configuration of clamp kilns using coal or other carbonaceous fuels and uncertainties regarding kiln combustion conditions, has proven to be a hurdle in measurement of emissions and standardization of process and energy metrics. To enable quantification of these metrics, a model kiln was designed to simulate operating conditions and configuration similar to transverse slice of a typical full-scale clamp kiln, but with lower capacity (20,000 to 35,000 bricks per cycle). Hourly measurements of flue gas at extraction duct were recorded for thirteen firing cycles obtained from various source factories, each lasting 8-14 days, for SO2, NO2, NO, PM, CO and CO2 emissions in the extraction stack. A statistical mean efficiency for model kiln emissions capturing and channelling capacity was calculated from sulfur mass balance results of batches that lie within 95% confidence interval of assumed true mean (100%) to give 84.2%. Final emission factors (mean ± standard deviation) were quantified as 22.5 ± 18.8 g/brick for CO, 0.14 ± 0.1 g/brick for NO, 0.0 g/brick for NO2, 0.14 ± 0.1 g/brick for NOx, 1.07 ± 0.7 g/brick for SO2, 378 ± 223 g/brick for CO2; 0.96 ± 0.5 g/brick for PM10; as well as 1.53 g/brick for hydrocarbons. Energy analysis indicate that a significant reduction of 0.9 MJ/kg (36%) in energy use could be achieved by clamp kiln operators, thereby reducing input costs, and significantly reducing atmospheric emissions.
... As traditional un-stabilised earth construction (adobe or wattle & daub) has become less popular [3,4], it has been largely replaced by higher demand for fired clay bricks. The demand for firewood to fuel brick kilns is a leading cause of deforestation in Uganda [5]. There is hence a need for affordable construction materials that can capitalise on abundant, locally available resources in a sustainable way. ...
Conference Paper
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Interlocking Stabilised Soil Blocks (ISSB) are an emerging construction material in Uganda that offer a more sustainable, locally produced alternative to fired clay bricks. Rice husk waste is an under-utilised by-product from rice production in Uganda, and its ash offers potential for lowering the Portland cement requirement of ISSB whilst maintaining mechanical properties. As a prelude to laboratory testing of ash sources accompanied by on-site production and testing of ISSB, a pilot study was carried out to characterise an industrial source of ash. The recently developed R3 heat release test was used to determine ash reactivity. The physical and chemical characteristics of the ash indicate that the industrial combustion process used was sub-optimal. However, its heat release performance suggests it has sufficient pozzolanic reactivity to deserve consideration for use as a supplementary cementitious material in ISSB production.
... Clamp kiln technology has, however, been globally branded as a polluting, energy inefficient 1 "Green Bricks" is a term used to describe bricks that have been processed, dried and ready to be fired. technology; and its usage has since been discontinued in most developed nations of the world (Akinshipe, 2013;Hashemi & Cruickshank, 2015;Raut, 2003;Irm, 2011;Skinder, et al., 2014;World Bank, 1997). ...
Conference Paper
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In previous papers we reported on the measurement of emissions from a model kiln designed to simulate clamp kilns used for firing clay bricks. The model kiln simulates the operating conditions and configuration similar to a transverse slice of a typical full-scale clamp kiln, but with a lower capacity (20 000 to 35 000 bricks per firing cycle). In South African clamp kilns, the primary source of energy is coal, both as internal fuel i.e. fuel contained within the bricks, and as ignition fuel at the bottom of the clamp. The latter is typically 25% to 35% of the total fuel used. In this paper, we report on a trial to use locally available liquidified petroleum gas as a substitute for the ignition fuel in order to reduce emissions from clamp kilns. Measurements were taken of emissions for particulate matter, sulfur dioxide, carbon monoxide, carbon dioxide and nitrogen oxides. Although apparatus malfunction caused incomplete measurements over the 12 day trial, corrected results indicate reductions of approximately 10% in particulate matter emissions, 41% in NOx emissions, 87% in carbon monoxide emissions, 7% in carbon dioxide emissions and a 19% increase in SO2 emissions. The increase in SO2 emissions is not commensurate with reductions in fuel sulfur input, indicating retention of sulfur in the brick.
... Moreover, rapid urbanisation and growing housing demand are some of the other current challenges of the country [7]. Currently, embodied energy of construction methods and materials seems to be the major challenge which requires immediate attention to mitigate negative environmental effects of the construction industry [8,9]. Adobe, cob, rammed earth, wattle and daub (also known as mud and poles), burned bricks, stabilised earth blocks; and concrete are the most common walling materials used in many developing countries including Uganda [10,11,12,13,14]. ...
Article
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This paper evaluates the effects of thermal insulation on thermal comfort in low-income tropical housing in Uganda. Dynamic thermal simulations are conducted to assess the effects of wall, roof and floor insulation strategies. 96 combination scenarios are simulated for various geometries, insulation and construction methods. Adaptive approach is used to evaluate the conditions within the case study buildings. The results indicate that external wall insulation improves thermal comfort in all conditions whereas internal wall and floor insulation may deteriorate the conditions. Roof insulation is the most effective strategy to reduce the risk of overheating. Due to the effectiveness of roof insulation and marginal improvements of external wall insulation, especially for brick walls, wall insulation may be disregarded when used in conjunction with roof insulation.
Article
As the world is witnessing vast pollution during material production, construction and demolition processes of buildings there is a need to seek for alternative materials that will reduce the environmental impact. The present study borrows inspirations from termite’s technique to create a material for constructing a naturally cemented mound structure. The studied termite mound was built from a mix of soil particles and termites saliva containing mucopolysaccharides and cellulase enzyme that digests cellulose into beta-glucose or shorter polysaccharides and oligosaccharides. These polysaccharides are found to be a source of soil stabilization and gluing property. In the process to mimic termites’ activities clay bricks were produced from a mix of clay soil and cassava flour in a form of hot cassava paste as a source of polysaccharides at 1.5%, 3%, 4.5% and 6% weight of soil. Brick samples created presented an optimal value at 1.5% cassava flour with compressive strength higher than that of burnt clay bricks at 4.28 MPa.
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Die Hauptexkursion verfolgte das übergeordnete Ziel, neben physiologischen, ökologischen, kulturellen und sozialen insbesondere raumwirtschaftliche Muster und Strukturen Ugandas und Ruandas (dabei insbesondere sowohl der Hauptstadtregionen bzw. der Hauptstadtagglomerationen rund um Kampala (Uganda) und Kigali (Ruanda) als auch der Peripherien abseits dieser Orte) auf zahlreichen Maßstabsebenen aufzuzeigen, zu beschreiben, zu erklären und im besten Falle bewerten zu können.
Thesis
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The quantification of atmospheric emissions from clamp kilns in the clay brick industry has met with limited success globally. The complex configuration of clamp kilns using coal or other carbonaceous fuels, as well as the uncertainty regarding kiln combustion conditions, has proven to be a hurdle in measurement of emissions and standardization of clamp kiln conditions. To enable measurement and quantification of emission and energy metrics, a model kiln was designed to simulate operating conditions and configuration similar to a transverse slice of a typical full-scale clamp kiln, but with a lower capacity (20 000 – 35 000 bricks per firing cycle). The model kiln design ensures the adequate confinement and extraction of flue gases with the aid of a bifurcated fan forcing the draft through a horizontal extraction stack where monitoring occurs. The model kiln design, which comprise two adjacent sealed sides and two partially enclosing and sliding galvanized steel doors, provides adequate spacing for ‘packing’ and ‘un-packing’ of bricks and sufficient oxygen for combustion, while still ensuring minimum losses of emission via the semi-enclosed sides. Concurrent firing and hourly monitoring of flue gases in the flue duct was conducted for fourteen batches of bricks over 8 – 14 days using varying brick products and energy inputs from eleven South African brick factories that utilizes clamp kiln as firing technology. The model kiln was tested for its suitability in firing bricks that are similar to conventional South African clamp kilns, as well as its effectiveness in the capturing and channelling of flue gases through to the stack vent where monitoring of the flue gases took place. Hourly readings are recorded for process parameters, SO2, NOx, NO, NO2, CO and particulate matter (PM) concentrations in the extraction stack. PM size-segregated mass measurement was conducted to produce PM1, PM2.5, PM4, PM10, and PM15 fractions. SO2 monitoring results were also compared to mass balance calculations, using the analysis of sulfur in the coal to indicate that the model kiln design is effective in capturing emissions and standardizing emission factors, as well as providing an effective energy analysis tool for clamp kilns. A statistical mean efficiency for the model kiln emissions capturing and channelling capacity was calculated from sulfur mass balance results of the batches that lie within 95% confidence interval of the assumed true mean (100%) to give 84.2%. Therefore, 15.8% of emissions were considered to escape from underneath the semi-enclosed sides. Final emission factors (mean ± standard deviation) were quantified as 22.5 ± 18.8 g/brick for CO, 0.14 ± 0.1 g/brick for NO, 0.0 g/brick for NO2, 0.14 ± 0.1 g/brick for NOx, 1.07 ± 0.7 g/brick for SO2, 378 ± 223 g/brick for CO2, 0.96 ± 0.5 g/brick for PM10; as well as 1.53 g/brick for hydrocarbons (calibrated to propane emissions) and 0.96 g/brick for PM15, PM4, PM2.5 and PM1. Various kiln technologies were ranked from lowest to highest potential for atmospheric pollution based on available emission metrics as follows: Zig-zag < Vertical shaft < South African Clamps < US coal-fired < Fixed chimney Bull’s trench < Tunnel < Asia Clamps < Down draft < Bull’s trench. Energy analyses indicate that a significant reduction of 0.9 MJ/kg (36%) in energy use could be achieved by the South African clamp kiln industry, thereby reducing cost of input, and significantly reducing the quantity of atmospheric emissions. In addition, chemical reactions and thermodynamic processes occurring in the firing chamber of brick kilns were qualitatively linked to the amount and type of pollutant emissions released at different periods during a firing cycle. The sensitivity of brick kiln emission concentrations and process metrics to these reactions and processes was utilized to proffer emission control measures. These measures are aimed at reducing energy consumption; improving the clay material processing and drying technique; monitoring chemical constituents of input materials in order to eliminate less favourable options; monitoring firing temperature to modify firing process; as well as altering the combustion and firing process in order to favour chemical and thermodynamic processes that will result in the release of lower emissions. Screening dispersion modelling results was additionally employed in recommending the extent of impact zones from the clamp kiln area for small kilns (500 m), medium kilns (1000 m) and large kilns (2000 m). A general reduction in most pollutant emissions was observed when the external fuel (coal) was replaced with a locally available alternative, propane gas. CO, CO2, NOx/NO and PM10 indicated 87%, 7%, 41% and 10% reduction in emissions respectively, during propane gas firing. SO2 emission, however, indicated a 19% increase, which may be attributed to lower energy consumption that alters the complex thermodynamic reactions in the model kiln. Only CO and NOx/NO emissions provided significant reduction in emission rates to support the notion that substituting the external coal with propane gas will result in significant reduction in atmospheric emissions. PM10 and CO2 emission rate do not provide significant reduction to validate this notion, while SO2 emission rate analysis is inconclusive and may require further research.
Article
In this paper, thermal characterization of four Ugandan woody biomass species was carried out in order to ascertain their suitability for gasification for small-scale biopower generation. The analyses and tests covered the aspects of proximate analysis, ultimate analysis, heating value, Thermogravimetric Analyses (TGA), ash melting and chemical composition. Eucalyptus grandis revealed ideal properties that make it the most promising wood specie for gasification applications. Furthermore, the low ash content in E. grandis significantly minimizes the possibilities of ash deposits on the gasifier and heat exchanger surfaces. The high fixed carbon in Terminalia glaucescens, Acacia hockii and Combretum molle makes these species ideal for charcoal making (pyrolysis). Due to high ash melting temperatures demonstrated by these samples, their pyrolysis and gasification can therefore take place with minimal worry of the ash related problems.
Article
The age and height wise variations in the fuel properties (basic density, calorific value, proximate and elemental parameters) of three short rotation forestry species i.e., Eucalyptus hybrid, Acacia auriculaeformis and Casuarina equisetifolia have been investigated. The fuel properties parameters were evaluated from the test samples of different age from 2 to 6 year and the samples obtained from three different height of trees i.e., stump height, diameter at breast height and top. A marginal increase in the calorific value with the age of tree (2–6 years) was found in all the species, the variation being significant in E. hybrid and C. equisetifolia. The basic density values were also found significantly different in E. hybrid and C. equisetifolia at lower ages (2–6 years). However, when the results were analyzed along the tree height, the calorific values were found to decrease along the stem length towards the tree-top in A. auriculaeformis and C. equisetifolia. The ash content in general was found to be higher in the top portions of the trees, and the same was found significantly higher in case of A. auriculaeformis. There was no particular trend observed for volatile matter content and the fixed carbon content with age. The fuel properties of lower age trees were compared with that of a mature tree (20 years of age) of same species. In general, the fuel properties of mature trees were found to be better than trees of lower age.
Article
In Uganda, Precambrian rocks have undergone extensive weathering and erosion, and are locally altered to form considerable clay deposits. We have studied the geochemical, mineralogical, and sedimentological characteristics of clay deposits from central Uganda to determine their composition, source rocks, deposition, and possible use in local industry. Samples were collected from the Kajjansi, Kitiko, Masooli, and Ntawo deposits (near Kampala), all of which are currently used for both industrial and tra-ditional brick, tile, and pottery manufacture. The deposits are widely scattered individual basins, with clays deposited under la-custrine and alluvial environmental conditions, and were all found to belong to the sedimentary group. The clays are composed of silt–sand fractions and predominantly consist of kaolinite and have a relatively high Fe 2 O 3 content. The studied deposits are chemically homogeneous, except for the samples richer in sand fraction, which have higher SiO 2 and K 2 O values. The chemistry of the studied samples, compared to European clays, shows that they need elaborate treatment to render them suitable for ceramics production. An analysis of the chemical and mineralogical composition of the clays has demonstrated that, taken as a whole, they possess characteristics satisfactory for brick production.
Article
Woodfuels are the most heavily used energy source in sub-Saharan Africa. We analyzed the ecological impacts and modes of access of five user groups (domestic consumers, gin distillers, brick manufacturers, charcoal producers, and tea companies) drawing biomass energy from natural forests in western Uganda. While domestic consumers use the most species for fuelwood (>50), their consumption is likely sustainable because they generally harvest fast-growing species from fallows on their own land or their neighbors’. Charcoal producers prefer old-growth hardwood species and are responsible for the greatest loss of natural forests. They access forests by finding landholders who, either willingly or through coercion, allow trees on their lands to be cleared. The impact of charcoal production is exacerbated by a license system that undervalues natural forests and rewards rapid harvests across large areas. The tea industry consumes mainly eucalyptus wood (Eucalyptus spp.) from corporate plantations, but they indirectly create pressure on natural forests by hiring immigrants who subsequently settle in and clear forest remnants. If such practices continue, forest remnants will soon be exhausted, leaving Kibale National Park as the last natural forest in the region. Forest remnants are a vital source of water, medicinal plants, and energy for local citizens and to protect them from over-exploitation, policy makers should target the charcoal and tea industry for reform. Support for local land management institutions governing access to fallows and successional forests will inevitably enhance the policy interventions.
A guide to understanding the embodied impacts of construction products, Construction Products Association
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The Present Economic Value of Nakivubo Urban Wetland, Uganda. IUCN -The World Conservation Union
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Interlocking Stabilised Soil Blocks, Appropriate earth technologies in Uganda
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