JWKisekka 2010 Page i

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