calorific value of selected multipurpose tree species used for woodfuel in uganda's dryland...
DESCRIPTION
A dissertation report of a study conducted to determine the energy content of Mangifera indica, Senna spectabiilis and Artocarpus heterophyllus used for woodfuel following the increased scarcity of traditionally preferred woodfuel species.TRANSCRIPT
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CALORIFIC VALUE OF SELECTED MULTIPURPOSE TREE SPECIES
USED FOR WOODFUEL IN UGANDA’S DRYLAND REGIONS
BY
JAMES WILLIAMS KISEKKA
SUPERVISOR: DR. JUSTINE NAMAALWA JJUMBA
SPECIAL PROJECT REPORT SUBMITTED TO THE FACULTY OF FORESTRY AND
NATURE CONSERVATION IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE AWARD OF A BACHELOR OF SCIENCE DEGREE IN FORESTRY,
MAKERERE UNIVERSITY.
©MAY 2010
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DECLARATION
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DEDICATION
With utmost love, this work is dedicated to my beloved family; The Kisekka family of KKingo
and Kasango, Masaka: to The Walugembe family of Kadebede, Kampala: and to my dear friends
Peter, Patrick, Michael, Eddie, Musa, Eve and Stella.
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ACKNOWLEDGEMENT
The list of people I ought to thank for this work is actually endless!! But the contribution of the
following individuals deserves mention.
First and foremost, my Parents Mr. Franklin Kisekka Kiswa and Miss Aisha Nyakaishiki Masika:
for their love, guidance and sowing the seed of responsibility in me. Mr. Paul Walugembe: for his
guidance and unwavering support; both morally and materially.
I am also indebted to Mr. Ndawula J. (of FFNC) for his technical advice especially in developing
the concept, to Mr. Katongole and Mr. Ssemwanga (both of Dept. of Animal Science, Faculty of
Agriculture) for their guidance throughout the analytical tests, to Mr. Karsten Bechtel (of
CREEC) for his guidance and technical support, and to the Chairman and residents of Katugo
village, Nakasongola district, for their hospitality and support during my sample collection.
Special thanks go my friends particularly Peter SSekiranda, Michael Wamuntu, Patrick Onyanga,
Musa Kagimu, Evelyn Namukasa and Stella Muwa Openyto for their invaluable support
especially at times when I desperately needed it most, and for their encouragement even when
progress seemed way too distant from me.
My sincere gratitude is extended to my supervisor; Dr. Justine Namaalwa Jjumba for her
guidance during the formulation of this manuscript and finally for approving my work. Above all
to God the Almighty who grants me the ability and strength to wake up every morning.
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TABLE OF CONTENTS
DECLARATION ........................................................................................................................... ii
DEDICATION .............................................................................................................................. iii
ACKNOWLEDGEMENT ............................................................................................................ iv
TABLE OF CONTENTS ............................................................................................................... v
LIST OF TABLES ...................................................................................................................... vii
LIST OF FIGURES ................................................................................................................... viii
ACRONYMS ................................................................................................................................. ix
ABSTRACT .................................................................................................................................... x
CHAPTER ONE: INTORDUCTION .......................................................................................... 1
1.1 Background ............................................................................................................................ 1
1.2 Statement of the Problem ....................................................................................................... 2
1.3 Objectives and hypothesis ...................................................................................................... 3
1.3.1 General objective ............................................................................................................. 3
1.3.2 Specific objectives ........................................................................................................... 3
1.3.3 Hypothesis tested ............................................................................................................. 3
1.4 Justification ............................................................................................................................ 3
CHAPTER TWO: LITERATURE REVIEW ............................................................................. 5
2.1 Defining Drylands .................................................................................................................. 5
2.2 Extent of Uganda‟s Drylands ................................................................................................. 5
2.3 Forest and Woodland Degradation in the Drylands ............................................................... 7
2.3 Wood Fuel .............................................................................................................................. 8
2.4 Fuelwood Scarcity .................................................................................................................. 9
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2.5 Calorific Value ..................................................................................................................... 10
2.5.1 Higher or Gross Calorific Value ................................................................................... 11
2.5.2 Lower or Net Calorific Value ........................................................................................ 11
2.5.3 Determination of Calorific Value .................................................................................. 12
3.1 Description of the Study Area .............................................................................................. 14
3.1.2 Economic activities ....................................................................................................... 14
3.2 Field Procedure .................................................................................................................... 14
3.3 Laboratory Procedure ........................................................................................................... 16
3.4 Data Analysis ....................................................................................................................... 17
CHAPTER FOUR: RESULTS AND DISCUSSION ................................................................ 18
4.1 Mean NCV for the three Species .......................................................................................... 18
4.3 Comparison between NCV of different Species .................................................................. 19
LIST OF REFERENCES ............................................................................................................ 23
LIST OF APPENDICES .............................................................................................................. 28
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LIST OF TABLES
Table 1: NCV for the three species ................................................................................................ 18
Table 2: Analysis Of Variance (ANOVA) for NCV for the three species ..................................... 18
Table 3: Multiple comparison between the species ....................................................................... 19
Table 4: Comparison between NCV of different Species .............................................................. 20
Table 5: T-test Results for the Comparison between the Mean NCV for the tested species. and
Oven dry wood ............................................................................................................................... 21
Table 6: T-test Results for the Comparison between the Mean NCV for the tested species and E.
grandis ............................................................................................................................................ 21
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LIST OF FIGURES
Figure 1: Map of Uganda Showing Extent of Drylands ................................................................... 6
Figure 2: Woodland Cleared for Farming and Woodfuel in Katugo ............................................... 7
Figure 3: Simplified Diagram Showing Components of a Bomb Calorimeter .............................. 12
Figure 4: Samples from A. heterophyllus (A), M. indica (B) and S. spectabilis (C). .................... 16
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ACRONYMS
CREEC: Centre for Research in Energy and Energy Conservation
Dept.: Department
DF: Degrees of Freedom
ESD: Energy for Sustainable Development
FAO: Food and Agricultural Organisation
FFNC: Faculty of Forestry and Nature Conservation
Fig.: Figure
GCV: Gross Calorific Value
Kcal: Kilo calories
Lab.: Laboratory
MAAIF: Ministry of Agriculture, Animal Industry and Fisheries
MEMD: Ministry of Energy and Mineral Development
MJ: Mega Joule
MWLE: Ministry of Water Lands and Environment
NCV: Net Calorific Value
NEMA: National Environment Management Authority
Sig.: Significance
Std.: Standard
Temp.: Temperature
Wt.: Weight
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ABSTRACT
Wood quality (dependent on its energy content) plays a crucial role in selecting a species for use
as fuelwood, and fuelwood users prefer long-burning woods with a high calorific output. In this
study, the calorific values of Artocarpus heterophyllus, Senna spectabilis, and Mangifera indica;
multipurpose tree species reported to be used for woodfuel in Uganda‟s Dryland regions was
assessed, with an aim of determining which of them is a better energy source, and ascertaining
whether it is worth using those species as energy sources.
The mean Net Calorific Values (NCV) of the 3 species were found to be 6939, 5444 and 4742
Kcal/kg respectively. The result of a One-way Analysis of Variance revealed a significant
difference (P = 0.000) in mean NCV for the 3 species, and a One sample T-test indicated that the
NCV for A. heterophyllus (p = 0.000) and S. spectabilis (p = 0.005) but not Mangifera indica
(p= 0.197) is significantly higher than the NCV for Eucalyptus grandis. The T- test also revealed
a significant difference between the Average NCV previously reported for oven-dry wood by
other researchers and the values obtained for A. heterophyllus (p = 0.000) and S. spectabilis (p =
0.009) but not for Mangifera indica (p= 0.713).
Basing on the outcome of this study, it is therefore recommended that the three species be
promoted for cultivation in both home-gardens and energy plantations, that factors which may
affect their quality as energy sources be studied, and that research be done about other candidate
species for energy production.
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CHAPTER ONE: INTORDUCTION
1.1 Background
Wood is the main source of energy for over two billion people, particularly for households in
developing countries, and it provides more than 14% of the world‟s total primary energy (FAO,
2007). The energy derived from wood fuel is called wood energy; which corresponds to the
calorific value of the wood species (FAO, 2007) and is also dependant on the genetic character
and biochemical composition of that particular species (Kataki and Konwer, 2002).
MEMD (2007) reported that Uganda‟s current energy demand is largely met by biomass
accounting for about 93% of the total energy supplied, and this is expected to continue in the
foreseeable future. McKendry (2002) reports that Biomass is a term for all organic material that
stems from plants (including algae, trees and crops). It is produced by green plants converting
sunlight into plant material through photosynthesis and includes all land- and water-based
vegetation, as well as all organic wastes. In Uganda, about 18 million and 500,000 tonnes of
firewood and charcoal respectively are consumed annually, and this has caused degradation of
forests as wood reserves are depleted at a rapid rate in many regions (MEMD, 2001).
MEMD (2004) revealed that about 45% of the charcoal into Kampala (the major urban centre in
Uganda) came from the dry land districts of Nakasongola, Masindi and Luwero, while 6% was
from Kamuli district. This is in line with previous studies, for example ESD (1995); Kalumiana
and Kisakye, (2001); MWLE (2002a), that rank Nakasongola, Masindi and Luwero districts
among the main charcoal sources in Uganda, the other districts being Hoima, Kayunga, Kibaale,
Kiboga and Apac; all of which are in the dryland region.
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1.2 Statement of the Problem
Wood quality is ideally expected to play a crucial role in selecting a species for use as fuelwood,
and, high density and high heat of combustion are among the desirable characteristics of quality
fuelwood (Goel and Behl, 1996). Marcelo et al. (2008) reported that durability and high heat of
combustion is related to high density, and that fuelwood users prefer long-burning woods with a
high calorific output.
In the past, fuelwood producers and specifically charcoal producers would selectively select tree
species with high density. These species included Combretum spp, and Acacia spp, among
others. Given the increased demand for forest products as a result of population increase, the
preferred tree species are continuously becoming scarce. A study done in Nakasongola and
Kamuli by Bagabo et al. ( 2008 ) revealed that there is a tremendous decrease in tree cover, as
well as an increased scarcity of the preferred species for charcoal, this leading to an
indiscriminate harvesting of tree species including fruit trees such as Artocarpus heterophyllus
and Mangifera indica. Also, Senna spectabilis is one of the other tree species that are now used
for fuelwood in the dry lands. This stimulates a research gap on the energy efficiency of such
species as they may continuously be exploited for fuelwood.
This research, therefore, is aimed at determining the calorific value of each of the three tree
species.
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1.3 Objectives and hypothesis
1.3.1 General objective
The main objective of this research is to investigate and document the calorific values of A.
heterophyllus, M. indica and S.spectabilis.
1.3.2 Specific objectives
Specifically, the study aimed at;
1. Determining the Net Calorific Values of the three species
2. Assessing the differences in the net calorific values of the three species
3. Comparing the net calorific values of the three species with known preferred fuelwood
species
1.3.3 Hypothesis tested
Ho: There is no difference in the Net Calorific Values of the selected species
1.4 Justification
This study will culminate in documentation of the calorific values of the three species; which will
be used for academic purposes, and also to stimulate research about other multipurpose tree
species that are used as wood fuel. The results of the study will be used by both political and
social initiatives to inform the local communities about whether or not it is worth using the three
species as wood fuel sources, and also to advise them (local community) about which of those
species is the best source of wood fuel.
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Basing on the calorific values of each species, recommendations will be made about whether or
not to promote them for cultivation in fuelwood plantations and/or home-gardens, as a step
towards ensuring sustainable production of fuelwood, and hence prevent further degradation of
forests.
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CHAPTER TWO: LITERATURE REVIEW
2.1 Defining Drylands
Jama and Zeila (2005) define drylands as arid, semiarid and hyper-arid areas in which annual
evapo-transpiration exceeds rainfall and in which agricultural productivity is limited by poor
availability of moisture. For this study, the definition of drylands by Okullo et al. (2005) which
refers to a dryland as „anywhere in Uganda that rainfall is a problem because of amount,
distribution and unreliability,‟ will be adopted. Drylands occupy 41% of the earth‟s land surface,
are home to 35% of its population (Mortimore et al., 2009), and are characterized by low (100-
600 mm annually), erratic and highly inconsistent rainfall levels (IFAD, 2000).
More than 30% of the world‟s drylands are found in Africa where they cover 65% of the
continental landmass (1.96 billion ha), in 25 countries. In eastern and central Africa, the Arid and
Semiarid Lands (ASALs) occupy significant areas; 75% of Kenya, 50% of Ethiopia and
Tanzania, 30% of Uganda and 20% of Rwanda (Jama and Zeila, 2005).
2.2 Extent of Uganda’s Drylands
Uganda‟s drylands occupy what is commonly referred to as the “cattle corridor”, an area
stretching from the North-East (the rangelands from Moroto and Kotido), through Luwero and
South to Masaka and Mbarara (through Central to South-East of the country). It covers many
districts stretching from Kotido, Moroto and Katakwi in the North-East through Nakasongola and
parts of Luwero in the Central to Rakai, Mbarara and Ntugamo (Fig.1). These areas are mainly
rangelands and they cover approximately 84,000 sq. km. (about 40%) of the total land area. In
these areas, semi-arid and dry sub-humid conditions prevail. They receive low and unreliable
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rainfall (450 - 800 mm) and drought is a common recurrent phenomenon, thus the vegetation is
sparse (Okullo et al., 2005). The drylands are considered to be the second most fragile ecosystem
in Uganda, after the highlands.
Figure 1: Map of Uganda Showing Extent of Drylands (Okullo et al., 2005)
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2.3 Forest and Woodland Degradation in the Drylands
As in many other parts of the developing world, deforestation in Uganda has reached an
advanced cumulative stage (Bashaasha et al., 2001). The extraction of fuelwood is the major
driver of forests and woodland degradation in the drylands (Okullo et al., 2005). Figure 2 shows
a woodland area that has been cleared of almost all the trees. Wood energy has been used for
thousands of years for cooking and heating. In many of the world‟s developing countries, it
remains the primary source of energy for the rural poor and in much of Africa total consumption
of woodfuel is still increasing, largely as a result of population growth (FAO 2008). Jama and
Zeila (2005) also recognised the phenomenal growth in the number of people living in East
African drylands, and that this occurs within the context of static or even contracting natural
resource base.
Figure 2: Woodland Cleared for Farming and Woodfuel in Katugo
Village, Nakasongola District
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The decline in indigenous and preferred tree species for fuelwood has led to an indiscriminate
harvesting of trees, including fruit trees (Bagabo et al., 2008). However, Buyinza and Teera
(2008); Buyinza et al. (2008) pointed out tree-farming as one of the possible approaches to
increase the supply of fuel wood. Also, MAAIF (2000), MWLE (2001), and MWLE (2002b) all
are supportive of the promotion and adoption of agroforestry (managing trees together with
agronomic crops and /or animals) as a strategy for eradicating poverty and combating the
degradation of natural resources (like forests and woodlands) in dry lands. In this regard,
Multipurpose trees; defined by Huxley and Van Houten (1997) as woody perennials that are
purposely grown to provide more than one significant contribution to the production or service
function of the land-use system that they occupy, are promoted.
2.3 Wood Fuel
Fuel is a combustible substance containing carbon as the main constituent which on proper
burning (combustion) gives large amounts of heat that can be used economically for domestic
and industrial purposes. In other words, any source of heat is termed as fuel (Senapati, 2006).
Combustion is used over a wide range of outputs to convert the chemical energy stored in
biomass into heat, mechanical power, or electricity using various items of process equipment, e.g.
stoves, furnaces, boilers, steam turbines, turbo-generators, etc. (McKendry, 2002). A high
calorific value is one of the desirable characteristics of a good fuel (Pahari and Chauhan, 2006
and Sivasankar, 2008).
Wood fuel refers to all types of lignocellulosic material derived directly and indirectly from
plants, trees, shrubs, and herbaceous plants grown in forest as well as non-forest lands and used
for fuel purpose. The main components of wood fuels are firewood, charcoal and wood derived
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fuels like black liquor, methanol and ethanol (Lefevre et al., 1997). According to Lefevre et al.
(1997), fuelwood is the wood in rough produced from forests as well as non-forests and used
solely for fuel purposes. It includes twigs, branches, wood chips, pellets and power derived from
natural or other forest or even non forests area (e.g. home garden), industrial wood residues and
recovered wood. Charcoal is a solid residue derived from carbonization, distillation, pyrolysis
and torrefaction of wood (from trunks and branches of trees) and wood by-products using pit,
brick and metal kilns. It also includes charcoal briquettes made from wood-based charcoal.
Fuelwood and charcoal are, according to MEMD (2001), the main sources of energy for the
domestic use in Uganda. Fuelwood is mainly used by people in rural areas while charcoal is more
popular among urban dwellers.
2.4 Fuelwood Scarcity
Fuelwood occupies an enviable place for providing many people especially the poor and rural
households with a primary source of energy (Shackleton, 1998). Wood consumed annually for
energy in sub-Saharan Africa increased from 1500 mill. m3 to 3500 mill. m
3 between 1950 and
2002 (Moyini and Muramira, 2002), and many regions are presently facing severe shortages of
fuel wood, fodder and food primarily due to increasing human and livestock populations and crop
production using little or no external inputs (FAO 2003).
Teplitz-Sembitzky (2006) reported that while massive unsustainable fuelwood harvesting has
contributed to the decimation of natural woodlands, large-scale clearing of forests and woodlands
is in most part done for agricultural purposes (cattle grazing, planting of crops) or on account of
commercial logging. Bagabo et al. (2008) reported that in the past fuelwood producers and
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charcoal producers in the dry land region would selectively select tree species with high density
because these burn for a longer time. But due to the increasing demand for woodfuel as a result of
population increase, the preferred tree species are continuously becoming scarce thereby leading
to an indiscriminate harvesting of tree species including fruit trees, that has resulted into a
tremendous decrease in tree cover. This situation warrants the need for corrective efforts like tree
planting, as recommended by previous researches.
2.5 Calorific Value
Calorific value is defined as the quantity of heat liberated by the complete combustion of one unit
of a fuel in oxygen (Pahari and Chauhan, 2006, Sivasankar, 2008, and Senapati, 2006). Calorific
value is the most important property of a fuel which determines its energy value (Erol et al.,
2010). It is a characteristic for each substance, and is measured in units of energy per unit of the
substance, usually mass. According to Kataki and Konwer (2002), the calorific value of wood
varies between 17 and 20 MJ/kg (about 4000 and 4700 Kcal/kg) for oven-dried wood, and
depends on the elemental composition and genetic make-up of a given species. According to
Jacovelli (2009), the calorific value of wood, on an oven-dry mass basis varies surprisingly little
at 4700Kcal/kg, while Bekele and Mulugeta (2004) reported an average NCV of 4577 Kcal/kg
for Eucalyptus grandis; which is, according to Jacovelli (2009), the tree species that is most
preferred for cultivation for fuelwood production in Uganda. Calorific values are of two types;
Higher Calorific value and Lower Calorific Value.
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2.5.1 Higher or Gross Calorific Value
Hydrogen is found to be present in almost all fuels and when the calorific value of a fuel is
determined experimentally, hydrogen is converted into steam. If the products of combustion are
condensed to room temperature (25oC), the latent heat of condensation of steam is also included
in the measured heat. The total value calculated is known as Higher or Gross Calorific Value
(HCV/GCV)and may be defined as the total amount of heat liberated when one unit of the fuel is
burnt completely and the combustion products are cooled to room temperature (Senapati, 2006).
2.5.2 Lower or Net Calorific Value
In actual practice, during combustion of a fuel the water vapors escape as such along with hot
combustion gases and thus are not condensed. Hence a lesser amount of heat liberated. This is
called Lower or Net Calorific Value (LCV/NCV) and may be defined as the amount of heat
liberated when one unit of fuel is burnt completely and the combustion products are allowed to
escape. Thus, LCV = HCV – Latent heat of water vapor formed.
Fuels should be compared based on NCV because GCV includes the heat content of the water
vapor, yet many appliances cannot use that heat. The NCV therefore allows for comparison to be
made about fuels, especially when gaseous fuels are used. However, for liquid and solid fuels this
is less an issue so these are often compared on GCV (Senapati, 2006).
Calorific values of solid and liquid fuels are usually expressed in Calories per gram (Cal/g) or
Kilocalories per kilogram (Kcal/Kg) or British thermal Units per pound (B.Th.U/lb) (Pahari and
Chauhan, 2006). But the S1 units are kcal/kg.
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2.5.3 Determination of Calorific Value
Calorific value of fuels is determined by use of a bomb calorimeter. A known mass of the fuel is
burnt and the quantity of heat produced is absorbed in water and measured. Then the quantity of
heat produced by burning that mass of the fuel is calculated (Pahari and Chauhan, 2006).
A simple sketch of the bomb calorimeter is shown in Figure 3. It consists of a strong cylindrical
stainless steel bomb in which the combustion of the fuel is carried out. The bomb has a lid, which
can be screwed to the body of the bomb as to make a perfect gas tight seal. The lid is provided
with two stainless steel electrodes and an oxygen inlet valve. To one of the electrodes, a small
ring is attached. In this ring, a nickel or stainless steel crucible can be supported. The bomb is
placed in a copper calorimeter which is surrounded by an air jacket and a water jacket to prevent
heat loss by radiation. The calorimeter is provided with an electrically operated stirrer and a
Beckmann‟s thermometer; sensitive enough to read up to 0.01oC (Senapati, 2006).
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Figure 3: Simplified Diagram Showing Components of a
Bomb Calorimeter (Easto and Mcconkey, 1985)
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CHAPTER THREE: METHODS AND TOOLS
3.1 Description of the Study Area
The study was carried out in Nakasongola district, which is one of the major sources of charcoal
used in the Kampala (MEMD, 2004). Nakasongola district is located at the centre of Uganda at
latitudes 055oN and 140
oN, and longitudes 31
o55‟E and 32
o50‟E, covering an area of 3510 sq.
Kms (about 1.46 % of the country‟s total surface area), and is one of the cattle corridor districts
characterized by drought. Topographically, the district is generally flat with minimal altitudinal
differences. 6.8 % of the district is open waters while 4.5 % is covered by wetlands (NEMA,
2004).
3.1.2 Economic activities
According to NEMA (2004), about 70 % of the district population derives their livelihood
through direct exploitation of Natural resources. This includes fishing, charcoal production and
agriculture. Such a large percentage puts a lot of stress on the quality and quantity of the
environment and Natural resources moreover with no rejuvenation strategies. The district was
reported to contribute about 30% of the charcoal consumed in Kampala (MEMD, 2004). Further,
increased indiscriminative harvesting of tree species for fuelwood has also been reported in the
district (Bagabo et al., 2008).
3.2 Field Procedure
The landscapes for consideration included home gardens for A. heterophyllus and M. indica; and
woodlands and/or bush-lands for S. spectabilis. Five standing trees per species were randomly
selected regardless of their age since age has been reported to have no effect on the calorific
value of most trees (Puri et al.,1994; Bekele and Mulugeta ,2004)
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For each selected tree, the first branch of 6 –10 cm diameter was cut- a method used by Kataki
and Konwer (2002), using a panga. From each branch, a disc of about 5cm thickness was cut. The
discs from the same tree species were packed in a polythene bag, and then taken to a local
carpentry workshop from where a cuboid was cut from the centre of each disc. The cuboids were
cut in such a way that they contained both the heartwood and sapwood - as in Kumar et al.
(2009), and Munalula and Meincken (2009), and were not of the same dimensions because the
reason for their cutting was to facilitate their transportation to the laboratory where the analytical
tests were carried out.
Each disc was packed in a polythene bag that was then coded for easy identification. Coding was
done in such a way that each code was a combination of the tree number and first letter of the
species name from which the sample was taken. For example, A1, M1, and S1 were the codes for a
sample taken from the first tree of Artocarpus heterophyllus, Mangifera indica and Senna
spectabilis respectively, as in Fig.4.
The samples were then transported to the Animal Sciences Laboratory at the Faculty of
Agriculture, Makerere University, where the analytical tests were carried out.
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C B
Figure 4: Samples from A. heterophyllus (A), M. indica (B) and S. spectabilis (C).
3.3 Laboratory Procedure
The laboratory procedure followed was as described by Easto and Mcconkey (1985).The samples
were dried in an oven for 48 hours at 110 oC, and then pulverized using a crusher. Powder from
each sample was then pressed to form a briquette using a briquetting press.
A small pellet was obtained from each briquette, weighed using an electric digital weighing
balance and then placed in a crucible. The crucible carrying the pellet was placed in the bomb,
and the electrodes were connected using a fuse wire of a known calorific value. A piece of cotton
thread was then used to connect the fuse wire to the pellet. A small quantity of distilled water was
put into the bomb to absorb the vapors formed by the combustion and to ensure that the vapor
A
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produced is condensed. The top of the bomb was then screwed down, and compressed oxygen
slowly administered to the bomb until the pressure was 30 atmospheres. The bomb was then
placed in the calorimeter of a known energy equivalent, and then two litres of water poured into
the calorimeter such that the bomb was submerged but its terminals remaining above the water
level. The energy equivalent for the Gallen Kamp Autobomb (model CAB001.ABI.C) used for
the Calorific Value determination in this study was 2418.
The calorimeter was then closed, the external connections to the circuit made, and a high
precision thermometer immersed in the water. The water was then stirred by a motor-driven
stirrer, and its stable temperature taken after five minutes. The charge was then fired at the end of
the fifth minute. The maximum temperature attained by the water was recorded, and the calorific
value of the pellet then calculated from the formula;
Mass of the pellet * NCV of the pellet = (energy equivalent of the bomb* corrected temperature
rise*specific heat of water)-calories of the fuse wire.
The lab procedure and the results obtained are summarized in appendix 1.
3.4 Data Analysis
A One-way Analysis of Variance (ANOVA) was used to determine if there was significant
variation in the NCV of the three species. One sample T-tests were used to determine if there was
a significant variation between the mean values described for oven-dry wood and other species in
the literature and those obtained for the three species.
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CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Mean NCV for the three Species
The results for mean NCV obtained for the three species are shown in Table 1.
Table 1: NCV for the three species
Species Mean NCV (Kcal/ kg)
Artocarpus heterophyllus 6939
Mangifera indica 4742
Senna spectabilis 5444
Mean NCV 5708
The NCV obtained for the three species revealed that Mangifera indica had the lowest mean
NCV while Artocarpus heterophyllus had the highest mean. The One-way ANOVA revealed that
there was a significant difference (p= 0.000) in the mean NCV at 95% confidence interval
(Tables 2 and 3).
Table 2: Analysis Of Variance (ANOVA) for NCV for the three species
Source of variation Sum of Squares DF Mean Square F Sig.
Between species 12591592.133 2 6295796.067 69.960 .000
Within species 1079893.600 12 89991.133
Total 13671485.733 14
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Table 3: Multiple comparison between the species
The differences could be attributed to the differences in the genetic makeup of the species as also
earlier suggested by Kataki and Konwer (2002).
The high NCV for Artocarpus heterophyllus implies that the species would be a more preferred
choice for Fuelwood as compared to Mangifera indica and Senna spectabilis. Also, Senna
spectabilis is better than Mangifera indica.
However, A. heterophyllus being a fruit tree, it‟s cultivation for fuelwood may not be a priority
among people in the dryland areas. This leaves S.specatabilis as the next best alternative for
cultivation as an energy crop, because it‟s NCV fairly high, and it has less competing uses as
compared to A. heterophyllus.
4.3 Comparison between NCV of different Species
A comparison was made between the NCV for the target species and the values prior recorded for
either individual species or a group of species (Table 4)
(I) species (J) species Mean Difference
(I-J)
Std. Error Sig.
A.heterophyllus M. indica 2197.000 189.727 0.000
S. spectabilis 1495.200 189.727 0.000
M. indica A.heterophyllus 2197.000 189.727 0.000
S. spectabilis -701.800 189.727 0.003
S. spectabilis A.heterophyllus 1495.200 189.727 0.000
M. indica 701.800 189.727 0.003
JWKisekka 2010 Page 20
Table 4: Comparison between NCV of different Species
Species Mean NCV (Kcal/ kg)
Tested Values Reviewed Values
Artocarpus heterophyllus 6939
Mangifera indica 4742
Senna spectabilis 5444
Aggregated study spp 5708
E. grandis
(Bekele and Mulugeta,2004) 4577
Aggregated species
(Jacovelli, 2009) 4700
Aggregated species.(Harker et al.,1984) 4300 - 6210
Acacia Cyclops, Acacia erioloba,
Eucalyptus cladocalyx, Pinus patula,
Vitis vinifer
(Munalula and Meincken ,2009)
4462 – 4546
The NCV for Artocarpus heterophyllus and Senna spectabilis were relatively higher than the
values reported for E. grandis and the aggregated species. Mangifera indica was on the other
hand in range of the reported values.
The one sample T-test revealed that there was a significant difference between the NCV for the
aggregated species and those for Artocarpus heterophyllus and Senna spectabilis. There was
however no significant difference with Mangifera indica. A similar trend was observed for E.
grandis (Tables 5 and 6).
JWKisekka 2010 Page 21
Table 5: T-test Results for the Comparison between the Mean NCV for the tested species.
and Oven dry wood
Species Test Value = 4700
t DF Sig. (2-tailed) Mean Difference 95% Confidence Interval of
the Difference
Lower Upper
A. heterophyllus 16.738 4 0.000 2239.200 1867.78 2610.62
M.indica 0.395 4 0.713 42.200 -254.19 338.59
S.spectabilis 4.734 4 0.009 744.000 307.62 1180.38
Table 6: T-test Results for the Comparison between the Mean NCV for the tested species
and E. grandis
Test Value = 4577
Species t DF Sig. (2-
tailed)
Mean
Difference
95% Confidence Interval of
the Difference
Lower Upper
A. heterophyllus 17.658 4 0.000 2362.200 1990.78 2733.62
S. spectabilis 5.516 4 0.005 867.000 430.62 1303.38
M. indica 1.548 4 0.197 165.200 -131.19 461.59
A. heterophyllus has a higher NCV compared to the other species, implying that is the best option
for fuelwood on the basis of calorific value. However, its use as a fruit tree may outweigh its use
as a fuelwood source. This puts S. spectabilis at a better competitive advantage than other species
if comparison is to be made with E.grandis; the tree species most cultivated for fuelwood in
Uganda today, but research has to be done about its growth characteristics in relation to
E.grandis.
JWKisekka 2010 Page 22
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
Renewable energy will continue to play a central role in energy supplies especially in the
developing countries, particularly in Asia and Sub-Saharan Africa, in the future given the high
population growth rates. The demand for fuelwood is, therefore, expected to continuously
increase. Hence, it is imperative to continuously devise and sustain natural resource production
methods that will sustainably produce wood for energy generation.
The large (and continuously increasing) quantity of fuelwood required for energy production can
only be sustained if farmers produce their own fuelwood rather than rely on the continuously
diminishing natural vegetation. In fact, as population increases and the supply of fuelwood from
natural forests declines, on farm fuelwood production is the best way out. Thus, since all wood
can burn, it is important that only those trees/woody species that will give substantially high
energy out puts should be recommended for incorporation into the agroforestry systems.
Tree species that are suitable for charcoal and fire wood production should be identified, and land
owners/farmers should be trained on how to plant and manage those tree. On that regard,
therefore, the three species studied under this research can be used for energy production since
their calorific value (energy content) was found to be significantly high – even higher than that
for the preferred species like Eucalyptus grandis. Such species can be promoted for growing in
energy plantations and home-gardens. However, factors such as their growth rates and effect on
the environment, which may affect their quality as energy sources ought to be studied. Also,
research has to be done about other candidate species for energy production in a bid to create a
sound and concrete ground for comparison.
JWKisekka 2010 Page 23
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LIST OF APPENDICES
Appendix I: Data Sheet for the Lab. Results
Lab
Code
Sample
Description
Wt (kg) Initial
Temp
Final Temp Temp Rise Calories of
Wire
Kcal/kg
8614 A1 0.000536 27.44 28.67 1.23 9 6509
8615 A2 0.000562 27.79 28.99 1.2 8.1 7274
8616 A3 0.000582 26.95 28.14 1.19 8 7020
8617 A4 0.000543 26.26 27.43 1.17 8.2 6782
8618 A5 0.00056 28.22 29.4 1.18 8 7111
8619 M1 0.000576 25.02 26.13 1.11 8.4 4990
8620 M2 0.000543 28.03 29.16 1.13 8.8 4928
8621 M3 0.000501 28.15 29.2 1.05 8.4 4514
8622 M4 0.000557 26.42 27.57 1.15 9 4811
8623 M5 0.000603 25.58 26.83 1.25 10 4468
8624 S1 0.00056 26.95 28.06 1.11 8.3 5306
8625 S2 0.000503 26.92 28 1.08 8 5907
8626 S3 0.000522 27.67 28.79 1.12 8.4 5695
8627 S4 0.000505 28.05 29.14 1.09 8.4 5282
8628 S5 0.000553 28.44 29.6 1.16 9 5030