ABUBAKAR TAFAWA BALEWA UNIVERSITY

BAUCHI

PRODUCTION OF BIODIESEL FROM ‘ZOBO’ (HIBISCUS SABDARIFFA L.) SEED OIL

A PROJECT

SUBMITTED TO THE CHEMISTRY DEPARTMENT

SCHOOL OF SCIENCE AND SCIENCE TECHNOLOGY

ABUBAKAR TAFAWA BALEWA UNIVERSITY BAUCHI

IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF A BACHELOR OF TECHNOLOGY, B.TECH. (HONS)

DEGREE IN INDUSTRIAL CHEMISTRY

BY

ADULOJU ABIMBOLA

04/15281/1

SEPTEMBER 201I.

CERTIFICATION

This project titled "Production of biodiesel from “Zobo (Hibiscus Sabdariffa L.) Seed Oil" was

conducted by Aduloju Abimbola O. (04/15281/1) and duly supervised and approved by Dr. I.Y

Chindo having met the requirement for the award of the degree of Bachelor of Technology in

Industrial Chemistry.

Dr. I.Y Chindo(Supervisor) Signature Date

External Examiner Signature Date

Dr. H.M. Adamu (Program Coordinator) Signature Date

ii

DEDICATION

This thesis is dedicated to my parent for their timeless support throughout the course of my study

and for everything they have done in my life right from my childhood to this stage of my life.

Their support, parental love, care and advice were my driving force throughout my years of

academic study. Love you Dad and Mum.

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ACKNOWLEDGEMENT

All thank is due to the Almighty, the Beneficent, the Merciful for sparing my life till this time.

I wish to start by acknowledging my mentor, my supervisor, and Uncle Dr. I.Y Chindo. I wish

to thank you sir for your constructive criticism, patience and understanding. May God continue

to guide and protect you and your family.

I also wish to acknowledge the following individuals who contributed immensely towards the

accomplishment of this work; Eleazar David, Ismail, Samson Olarinoye, Abdulrasheed

Abdulkareem and as much people that I cannot mention, I don’t know how to thank you all for

your support. I pray to God Almighty to bless and reward you abundantly and increase you. To

my dear Deborah Adio, thank you for being there for me.

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TABLE OF CONTENTS

CERTIFICATION ………………………………………………………… ii

DEDICATION …………………………………………………………….. iii

ACKNOWLEDGEMENT ………………………………………………… iv

TABLE OF CONTENTS………………………………………………….. v

LIST OF FIGURES ……………………………………………………….. ix

LIST OF TABLES ………………………………………………………… x

ABSTRACT ……………………………………………………………….. xi

CHAPTER ONE: INTRODUCTION

1.1.0 BRIEF HISTORY OF BIODIESEL ………………………………... 1

1.2.0 BIODIESEL: A TRANSESTERIFIED VEGETABLE OIL ………… 2

1.2.1 IMPORTANCE OF BIODIESEL ………………………………. 3

1.2.2 CAN BIODIESEL REPLACE PETRODIESEL? …………………… 4

1.3.0 FATS AND OILS …………………………………………………… 5

1.4.0 FATTY ACIDS …………………………………………………… 5

1.5.0 QUALITY PARAMETERS ……………………………………… 7

1.6.0 LITERATURE REVIEW………….…………………………………10

1.6.1 HIBISCUS SABDARIFFA L. ….....................................................10

1.6.2 THE FOOD USES AND VALUE OF ZOBO……………………….11

1.7.0 AIM AND OBJECTIVES OF RESEARCH ………………………… 12

CHAPTER TWO: MATERIALS AND METHODS

2.1.0 COLLECTION OF SAMPLES ……………………………………… 13

2.2.0 SOLVENTS AND REAGENTS ……………………………….. 13

2.3.0 MOISTURE CONTENT ……………………………………………... 13

v

2.4.0 n-HEXANE EXTRACTION ……………………………………….14

2.5.0 PHYSICAL PROPERTIES OF OIL ……………………………….. 14

2.5.1 COLOUR …………………………………………………………… 14

2.5.2 SMELL …………………………………………………………. 15

2.5.3 TEXTURE …………………………………………………………. 15

2.5.4 SPECIFIC GRAVITY………………………………………………….15

2.5.5 VISCOSITY………..…………………………………………………..15

2.5.6 DENSITY……………………………………………………………..16

2.6.0 CHEMICAL PROPERTIES OF OIL ………………………………..16

2.6.1 FREE FATTY ACID ……………………………………………. 16

2.6.2 ACID VALUE …………………………………………………… 17

2.6.3 PEROXIDE VALUE ……………………………………………. 17

2.6.4 SAPONIFICATION VALUE ……………………………………. 18

2.6.5 IODINE VALUE ………………………………………………….. 19

2.7.0 PREPARATION OF FATTY ACID METHYL ESTER …………….20

2.8.0 FUEL QUALITY PARAMETER TESTS ………………………. 21

2.8.1 FLASH PONT ………………………………………………….. 21

2.8.2 POUR POINT ………………………………………………….. 21

2.8.3 CLOUD POINT ………………………………………………….. 22

2.8.4 DENSITY …………………………………………………………. 22

2.8.5 CALORIFIC VALUE …………………………………………… 23

2.8.6 KINEMATIC VISCOSITY …………………………………….. 23

2.8.7 CETANE NUMBER ……………………………………………. 24

2.8.8 FLAME TEST …………………………………………………... 25

2.8.9 COMBINED GAS CHROMATOGRAPHY-MASS SPECTROMETRY

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……………………………………………………………………………….25

2.9.0 PREPARATION OF REAGENTS ………………………………. 25

2.9.1 0.14M NaOH …………………………………………………… 25

2.9.2 GLACIAL ACETIC ACID/CHLOROFORM (3:2 V/V) ………….. 26

2.9.3 SATURATED POTASSIUM IODIDE ………………………… 26

2.9.4 0.1N SODIUM THIOSULPHATE ………………………………..26

2.9.5 0.5M HCl …………………………………………………………… 26

2.9.6 0.5M ETHANOLIC POTASSIUM HYDROXIDE ………………….. 26

2.9.7 HANUS SOLUTION …………………………………………… 26

2.9.8 15% POTASSIUM IODIDE ……………………………………. 27

2.10.0 PREPARATION OF INDICATORS ……………………………… 27

2.10.1 1% STARCH INDICATOR …………………………………….. 27

2.10.2 PHENOLPHTHALEIN INDICATOR…………………………….... 27

CHAPTER THREE: RESULTS AND DISCUSSION

3.1 RESULTS ………………………..……………………………. 28

3.2 DISCUSSION…………………………………………………… 33

CHAPTER FOUR: CONCLUSION AND RECOMMENDATION

4.1 SUMMARY…………………………………………………………...35

4.2 CONCLUSION ……………………………………………………. 36

4.3 RECOMMENDATIONS …………………………………………….. 37

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LIST OF FIGURES

1. A TRYGLYCERIDE MOLECULE ……………………………… 2

2. THE MOLECULAR AND STRUCTURAL FORMULAE OF SOME

FATTY ACIDS ………………………………………………….. 6

3. ZOBO (HIBISCUS SABDARIFFA L.) ……..………………………... 10

4. SEPARATION OF BIODIESEL FROM GLYCEROL……………. 39

viii

LIST OF TABLES

1. CHEMICAL NAMES AND DESCRIPTIONS OF SOME COMMON

FATTY ACIDS ……………………………………………………. 6

2. MOISTURE CONTENT AND OIL RECOVERY OF HIBISCUS

SABDARIFFA L. SEED….…………………………………............29

3. SMELL, COLOUR AND TEXTURE OF HIBISCUS SABDARIFFA L.

SEED OIL……………………………………….………………. 30

4. A COMPARISON OF OIL QUALITY PARAMETERS OF HSSO AND

THOSE OF CITRULLUS LANATUS SEED OIL AND CASTOR SEED

OIL ………………………………………………………………… 30

5. RESULTS OF THE FUEL QUALITY PARAMETERS OF HSSO,

CPFAMES AND D2 ……………………………………………..40

6. COMPARISON OF THE RESULTS OF FUEL QUALITY PARAMETERS

OF HSFAMES WITH OTHER INVESTIGATED FAMES AND WITH

STANDARDS ……………………………………………………. 45

7. GC-MS ANALYSIS OF BIODIESEL FROM HIBISCUS SABDARIFFA

L…………………………………………………………………………46

ix

ABSTRACT

Due to the concern on the availability of recoverable fossil fuel reserves and the environmental problems caused by the use of those fossil fuels, the global energy concern has led to the search for alternative energy from the extensive consumption of fossil fuels. In this research the seed oil of ‘Zobo’ (Hibiscus sabdariffa L.) was investigated for its viability as a feedstock for biodiesel production. The oil quality characteristics of the seed oil were; iodine value (IV), 39.46 g iodine/100g oil, peroxide value (PV), 26 meq peroxide/kg oil, acid value (AV), 16.50 mg KOH/kg oil, saponification value (SV), 151.47 meqKOH/kg oil, free fatty acid (FFA), 8.29 % of oil, specific gravity (S.G), 0.904 g/ml oil and viscosity, 29.13 mm2/s at 30 °C. The oil was transesterified using ethanol and potassium hydroxide and the parameters were compared to that of petroleum diesel number 2 (D2). Fuel tests on the Hibiscus sabdariffa L. seed oil methyl ester gave a high cetane number, 68.2 and a high flash point of 317 °C. Other fuel properties of the biodiesel assayed were cloud point, pour point, viscosity, density and calorific value and the results were; -3 °C, -19 °C, 2.20 mm2/s, 871 kgm-3 and 124272 J respectively. The results obtained for the biodiesel was also compared with the American and European standards for biodiesel (ASTM D6751 and EN14214) and were found to fall within the acceptable limits, implying that Hibiscus sabdariffa L. fatty acid ethyl ester could be used alone or as blends with diesel D2 in diesel combustion engines in tropical regions like Nigeria. GC/MS analysis of the ethylated oil revealed the presence of 4 ethyl ester (palmitoic ethyl ester, linoleic acid ethylester, 9-octadecenoic acid ethyl ester, and ethyl-octadecanoate).

x

CHAPTER ONE

1.0 INTRODUCTION

1.1.0 BRIEF HISTORY OF BIODIESEL

The concept of biodiesel dates back to 1885 when Dr. Rudolf Diesel built the first diesel engine

with the full intention of running it on vegetative sources (Knothe, 2001). He first displayed his

engine at the Paris show of 1900 and astounded everyone when he ran the patented engine on

any hydrocarbon fuel available which included gasoline and peanut oil (Knothe, 2001). In 1912

he stated"...... the use of vegetable oils for engine fuels may seem insignificant today. But such

oils may in the course of time become as important as petroleum and the coal tar products of

present time” (Knothe, 2001). Since then, the requirements for an alternative internal combustion

engine fuel have grown increasingly. Whereas, in early years, it was sufficient for a fuel to

merely provide enough energy to gets the engine running. Now the fuel must also be non toxic,

biodegradable, come from renewable sources and minimize emissions of CO, NOx, unburned

hydrocarbons and CO2 (Ali and Hanna, 1994).

Today, the demand for alternative energy sources is frequent, because there is a progressive

decrease of the world’s petroleum (Knothe, 2001). Vegetable oil fuel or biodiesel is a potential

substitute for diesel fuel because it is made from renewable source (Ali and Hanna, 1994). In

addition, it can also be described as ‘carbon neutral’. This means that, the fuel produces no net

output of carbon in the form of CO2 (Knothe, 2001). This effect occurs because when the oil crop

grows, it absorbs the same amount of CO2 as it is released when the fuel is burnt (Knothe, 2001).

The American Society for Testing Material (ASTM) defines biodiesel as a fuel composed of

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monoalkyl esters of long-chain fatty acids derived from renewable vegetable oils or animal fats

meeting the requirements of ASTM D6751(Canakci and Sanli, 2008).

1.2.0 BIODIESEL: A TRANSESTERIFIED VEGETABLE OIL

In simple terms, biodiesel is the product obtained when a vegetable oil or animal fat

(triglyceride) is chemically reacted with an alcohol to produce fatty acid alkyl esters in a process

called transesterification (Arjun, 2008). A catalyst such as sodium or potassium ethoxide or any

alkoxide is required, with glycerol produced as a co-product.

Chemically, most vegetable and animal oils and fats are triglycerides- glycerol bound to 3 fatty

acids, as shown in Figure 1below.

Figure 1: A triglyceride molecule

Where R1, R2 and R3 represent the hydrocarbon chains of the fatty acyl groups of the triglyceride.

It is this triglyceride that undergoes a chemical reaction breaking down and replacing the

glycerin portion with an alcohol molecule. The glycerin is then converted to glycerol and falls to

the bottom where it is drained off leaving the biodiesel. This will be explained in detail in

subsequent chapters.

2

Biodiesel is currently undergoing a phase of active research all over the world today.

Researchers at all levels are exploring the use of various plants as feedstock for biodiesel

production. The plants that have so far being investigated for this purpose in Nigeria and various

parts of the world include rapeseed, sunflower, jatropha, castor plant, soybean, thevitia, nerfolia

etc (Arjun, 2008). The current research is therefore aimed at exploring the use of Hibiscus

sabdariffa L seed as a feedstock for biodiesel production.

1.2.1 IMPORTANCE OF BIODIESEL

There are five primary reasons why the development of biodiesel should be encouraged in

Nigeria as follows:

1. It provides a market for excess production of vegetable oils and animal fats.

2. It decreases the country’s dependence on petrodiesel (gasoline) which is currently being

imported.

3. It is renewable and does not contribute to global warming due to its closed carbon cycle.

4. The exhaust emissions (CO, unburned hydrocarbons, particulate emissions etc) from

biodiesel are lower than with fossil diesel.

5. Biodiesel has excellent lubricating properties than petrodiesel and hence reduces engine

wear.

In addition to these, biodiesel has some advantages over petrodiesel which include low toxicity,

superior flash point, biodegradability, negligible sulfur content etc (Knothe, 2001).

Consequently however, the production of biofuels has some disadvantages which include the

following;

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1 Biodiesel take a large expanse of area to grow. As a result good land suitable for other

crops gets diverted to biofuel species (Holbrook, 2001).

2 Biofuels may raise the price of certain foods, which are also used for biofuel such as

corn.5

3 As other plants are replaced, soil erosion will grow (Holbrook, 2001).

4 A lot of water is used to water the plants, especially in dry climates (Holbrook, 2001).

5 Sometimes the production of some biofuels actually leads to more greenhouse gas

emissions than they decrease such as in the case of rapeseed corn etc (Holbrook, 2001).

1.2.2 CAN BIODIESEL REPLACE PETRODIESEL?

Despite the upsides, however, experts point out that biofuels are far from a cure for our

addiction to petroleum. A wholesale societal shift from gasoline to biofuels given the number

of gas-only cars already on the road and the lack of ethanol or biodiesel pumps at existing

filling stations, would take some time (Ali and Hanna, 1994).

Another major hurdle for widespread adoption of biofuels is the challenge of growing

enough crops to meet demand, something skeptics say might well require converting just

about all of the world’s remaining forests and open spaces over to agricultural land (Ali and

Hanna, 1994).

“Replacing only five percent of the nation’s diesel consumption with biodiesel require

diverting approximately sixty percent of today’s soya crops to diesel production,” says

Mathew Brown, an energy consultant (Ali and Hanna, 1994).

4

1.3.0 FATS AND OILS

Fats and oils are primarily water- soluble, hydrophobic substances in the plant and animal

kingdom that are made up of one mole of glycerol and three moles of fatty acids and are

commonly referred to as triglycerides (Knothe, 2001).The properties of different fats and oils

depend upon the characteristics of the triglycerides of which they are mixtures and upon the

proportions of these triglycerides to one another (Knothe, 2001).Therefore, certain quality

tests has to be conducted on a fat or oil before being used for biodiesel production. Other

contaminants such as color and odor of bodies can in turn reduce the value of the glycerin

produced, and reduce the public acceptance of the fuel if the color and odor persist in the fuel

(Holbrook, 2001).

1.4.0 FATTY ACIDS

Fatty acids are component of both vegetable oil and biodiesel. They are ultimately consumed

in a wide variety of end use industries (rubber, plastics, detergents etc) (Canakci and Sanli,

2008).Fatty acids make up the greatest proportion of the current consumption of raw

materials in the chemical industry (Morton and Julia, 1987).

To describe precisely the structure of a fatty acid molecule, one must give the length of the

carbon chain (number of carbon), the number of double bonds and also the exact position of

these double bonds. Some common fatty acids usually found in most oils are shown in Table

1 below.

5

Table 1: Names and descriptions of some common fatty acids

Common Name CarbonAtom

Double Bonds

Scientific Name Sources

Butyric acid 4 0 Butanoic acid Butter fatCaprylic acid 8 0 Octanoic acid Coconut oilLauric acid 12 0 Dodecanoic acid Coconut oilMyristic acid 14 0 Tetradecanoic acid Palm kernel oilPalmitic acid 16 0 Hexadecanoic acid Palm oilStearic acid 18 0 Octadecanoic acid Animal oilOleic acid 18 1 9-octadecenoic acid Olive oilRicinoleic acid 18 1 12-hydroxy-9-

octadecenoic acidCastor oil

Linoleic acid 18 2 9,12-octadecadieoic acid

Grape seed oil

Gadoleic acid 20 1 9-eicosanoic acid Peanut oil, fish oil

The molecular and structural formulae of some fatty acids are also shown in Figure 2 below.

(9, 12 -octadecadieoic acid)

(Hexadecanoic acid)

Figure 2: The structures of some fatty acids

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1.5.0 QUALITY PARAMETERS

CALORIFIC VALUE: Calorific value or heating value is the amount of heating energy

released by the combustion of a unit value of fuels (Alptekin and Canakci, 2009).One of the

important determinants of heating value is moisture content. Air-dried biomass typically has

about 15-20 % moisture, whereas the moisture content also affects the rate of biological activity

on oils. Therefore high moisture is not desirable (Alptekin and Canakci, 2009).

POUR POINT: This refers to the temperature at which the oil in solid form starts to pour

(Alptekin and Canakci, 2009). In cases where these temperatures fall below the melt point, the

entire fuel system including all fuel lines and fuel tank will need to be heated (Alptekin and

Canakci, 2009).

CLOUD POINT: The temperature at which oil starts to solidify is known as the cloud point

(Alptekin and Canakci, 2009). while operating an engine at temperatures below oil’s cloud point,

heating will be necessary in order to avoid waxing of the fuel (Alptekin and Canakci, 2009).

FLASH POINT: The flash point of a diesel fuel is the minimum temperature at which the fuel

will ignite (flash) on application of an ignition source (Alptekin and Canakci, 2009). Flash point

varies inversely with fuel’s volatility. Minimum flash point temperature of about 1300Cis

required for proper safety and handling of diesel fuel (Alptekin and Canakci, 2009).

IODINE VALUE: This is the mass of iodine in grams that is consumed by 100g of a test

substance (Alptekin and Canakci, 2009). It is used in the determination of the amount of

unsaturation contained in fatty acids and other hydrocarbons. Many vegetable oils and some

animal fats are ‘drying’ or ‘semi drying’ and it is this which makes many oils such as linseed,

Tung and some fish oils suitable as the base for paints and other coatings (Alptekin and Canakci,

7

2009). But it is also this property that further restricts their use as fuels (Alptekin and Canakci,

2009).

VISCOSITY: Viscosity refers to the thickness of the oil, and it is determined by measuring the

amount of time taken for a given measure of oil to pass through an orifice of a specified size

(Alptekin and Canakci, 2009). Viscosity affects injector, lubrication and fuel atomization

(Alptekin and Canakci, 2009). Fuels with low viscosity may not provide sufficient lubrication for

the precision fit of the fuel injection pumps, resulting in leakage or increased wear (Alptekin and

Canakci, 2009).

PEROXIDE VALUE: Peroxide value is a measure of the peroxides contained in the oil. It is

used as a measure of the extent to which rancidity reactions have occurred in an oil or fat during

storage. The double bonds found in fats and oils play a role in autoxidation. Oils with a high

degree of unsaturation are more susceptible to autoxidation (a free radical reaction involving

oxygen that leads to deterioration of fats and oils which form off-flavors and off-odors)

(Alptekin and Canakci, 2009).

SAPONIFICATION VALUE: Saponification value represents the number of milligrams of

KOH or NaOH required to saponify1.0 g of fat under the conditions specified (Alptekin and

Canakci, 2009). It depends on the kind of fatty acids contained in the fat. This parameter is also

important in judging oil as it allows for comparison of the average fatty acid chain length

(Alptekin and Canakci, 2009).

ACID VALUE: This is the mass of KOH in milligrams required to neutralize the free fatty acids

present in 1.0g of the oil. The acid value is the measure of the extent to which the triglycerides in

8

the oil have been decomposed by lipase or other action. The decomposition is accelerated by heat

and light (Alptekin and Canakci, 2009).

CHROMATOGRAPHY: The term chromatography refers to a general method of separation in

which a mixture is partitioned between a stationary phase and a mobile phase. The moving phase

may be a vapor or a liquid, the stationary phase is a solid or liquid phase coated onto a solid

(Waheed and Zafar, 1980).

All the techniques depend on the same basic principle, that is variation in the rate which different

components of a mixture migrate through a stationary phase under the influence of the mobile

phase. The rate of migration varies because of difference in distribution ratios. Chromatography

now embraces variety of processes which are based on different distribution of sample

components between two phases; thermally stable volatile organic and inorganic compounds are

separated using Gas Chromatography as a technique of choice.

9

1.6.0 LITERATURE REVIEW

1.6.1 HIBISCUS SABDARIFFA L.

Hibiscus sabdariffa commonly referred to as ‘Zobo’ in hausa, “ishapa” in Yoruba, belongs to

malvaceae family. It is an erect, mostly branched, annual shrub. Stems are reddish in color and

up to 3.5 m tall. Leaves are dark green to red, alternate, glabrous, long-petiolate, palmately

divided into 3–7 lobes, with serrate margins containing short-peduncles (Morton and Julia,

1987).

Figure 3: Hibiscus sabdariffa L.

Hibiscus has more than 300 species which are distributed in tropical and subtropical regions

around the world. (Morton and Julia, 1987). (Fig. 3), commonly named as “red sorrel” and

“zobo” Detailed studies on their use as a feedstock for biodiesel production are very limited,

especially in Nigeria.

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1.6.2 THE FOOD USES AND VALUE OF ZOBO

Many parts of Hibiscus sabdariffa L. including the seeds, leaves, fruits and roots are used in

various foods. Among them, the fleshy red calyces are the most popular (Duke, 1983). They are

used fresh for making wine, juice, jam, jelly, syrup, gelatin, pudding, cakes, ice cream and

flavors and also dried and brewed into tea, spice, and used for butter, pies, sauces, tarts, and

other desserts (Duke, 1983). The calyces possess pectin that makes a firm jelly (Duke, 1983).

The young leaves and tender stems of “zobo” are eaten raw in salads or cooked as greens alone

or in combination with other vegetables and/or with meat (Duke, 1983). They are also added to

curries as seasoning. They have an acid, rhubarb-like flavor (Duke, 1983). The red calyces

contain antioxidants including flavonoids, gossypetine, hibiscetine and sabdaretine (Duke, 1983).

The fresh calyces are also rich in riboflavin, ascorbic acid, niacin, carotene, calcium, and iron

that are nutritionally important (Duke, 1983). The seeds, are high in protein, can be roasted and

ground into a powder then used in soups and sauces (Duke, 1983). The roasted seeds can be used

as a coffee substitute. The young roots are edible, but very fibrous (Duke, 1983).

1.6.3 MEDICINAL USES OF Hibiscus sabdariffa L.

Hibiscus sabdariffa L. is used in many folk medicines. It is valued for its mild laxative effect and

for its ability to increase urination, attributed to two diuretic ingredients, ascorbic acid and

glycolic acid (Watt and Breyer-Brandwijk, 1962). Because it contains citric acid, it is used as a

cooling herb, providing relief during hot weather by increasing the flow of blood to the skin's

surface and dilating the pores to cool the skin (Watt and Breyer-Brandwijk, 1962). The leaves

and flowers are used as a tonic tea for digestive and kidney functions (Watt and Breyer-

Brandwijk, 1962). The heated leaves are applied to cracks in the feet and on boils and ulcers to

speed maturation (Watt and Breyer-Brandwijk, 1962). The calyces and seeds are diuretic,

11

laxative and tonic (Watt and Breyer-Brandwijk, 1962). The ripe calyces, boiled in water, can be

used as a drink to treat bilious attacks (Duke, 1983). A lotion made from Hibiscus sabdariffa L.

leaves is used on sores and wounds (Watt and Breyer-Brandwijk, 1962).

1.7.0 AIM AND OBJECTIVES OF RESEARCH

1.7.1 AIM:

The aim of this research is to explore the use of transesterified Hibiscus sabdariffa L. seed oil as

a feedstock for biodiesel production.

1.7.2 OBJECTIVES:

The objectives of this research are:

i. To carry out the extraction and transesterification of Hibiscus sabdariffa L. seed oil.

ii. To carry out the physicochemical characterization of the oil and the resulting esters.

iii. To compare the results of the esters with those of other investigated oils from literature

and with standards.

12

CHAPTER TWO

2.0 MATERIALS AND METHODS

2.1.0 COLLECTION OF SAMPLES

The Hibiscus sabdariffa L, (zobo) seeds were obtained from Muda Lawal market in Bauchi, and

were ground to powder in mortar in preparation for extraction.

2.2.0 SOLVENTS AND REAGENTS

The reagents used were of Analar grade obtained from a vendor of Eagle Scientific, BDH

chemicals limited Sigma-Aldrich Laboreh Chemikalein Gmbh, Germany.

The reagents and solvents include the following: starch, n-hexane, magnesium sulphate,

magnesium silicate, iodine, ethanol, phenolphthalein, glacial acetic acid, potassium iodide,

sodium thiosulphate, sodium hydroxide, hydrochloric acid etc.

The diesel D2 used as a control for the entire test was obtained from ATIL filling station,Yelwa

Bauchi.

2.3.0 MOISTURE CONTENT DETERMINATION

A small portion of the crushed Hibiscus sabdariffa L. Seed prepared for extraction was placed in

a dried and weighed crucible. The crucible with the sample was placed in a temperature

adjustable oven at 100 °С, heating and weighing at 50 mins intervals until the weight of the

sample remained constant. The crucible and its content were then allowed to cool, and the

moisture content determined using the formula shown below:

13

Percentage moisture = Wi−Wf

Wi×100

Where:

Wi = initial weight of sample (before drying)

Wf = final weight of sample (after drying).

2.4.0 n-HEXANE EXTRACTION

Using hot extraction, 80 g of the ground seed was loaded into a soxhlet extractor together with n-

hexane and the extraction carried out for 8 hours until it was certified that the oil was almost

completely extracted. The oil was then filtered using fluted Whatmann No.2 filter paper under

gravity to remove impurities such as anti bump granules, sand e.t.c present the hexane was

recovered using a rotary evaporator and the residual solvent evaporated in the fume cupboard.

The oil was weighed and the percentage oil recovery calculated on dry matter bases as shown

below;

Percentage recovery = weigh t of oil

weigh t of sampleon drymatter basis×100

2.5.0 PHYSICAL PROPERTIES OF OIL

32.5.1 COLOUR

The Hibiscus sabdariffa L. seed oil colour was determined by visual observation.

2.5.2 SMELL

14

The smell of the oil was identified by perceiving with the nose.

2.5.3 TEXTURE

The texture of the oil was determined by hand feeling.

2.5.4 SPECIFIC GRAVITY

An improvised specific gravity bottle was washed, rinsed with acetone and dried in the oven.

The bottle was cooled at room temperature in a desiccator and the weight of the empty bottle

determined using an electronic weighing balance. The weight of the bottle filled with water was

recorded. Then the water was poured out and the bottle was rinsed with acetone and dried in the

oven. The same procedure was repeated with the Hibiscus sabdariffa L. seed oil and the specific

gravity was computed as follows;

Specific gravity = W 3−W 2

W 1

Where;

W3= weight of bottle + oil

W2= weight of empty bottle

W1= weight of equal volume of water

2.5.5 VISCOSITY

The viscosity of the Hibiscus sabdariffa L. seed oil was obtained using a viscometer. The oil was filled to the mark on the viscometer, same as the water. The time of flow of the oil and the water were determined using the equation below.

Viscousity = ts - tw

tw

Where; ts = time of flow of sample.tw = time of flow of water.

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2.5.6 DENSITY

The density of the Hibiscus sabdariffa L. seed oil was obtained by weighing a known volume (17.6g) of the oil, where the density was determined using the equation below.

Density = W2 –W1

VWhere; W2 = Weight of beaker and oil.

W1 = weight of empty beaker.

V = Volume of the oil.

2.6.0 CHEMICAL PROPERTIES OF OIL

2.6.1 FREE FATTY ACID (FFA)

Reagents

i. Methanolii. Phenolphthalein indicator

iii. 0.14 M NaOH

Procedure

The method used for the determination was that of the British standards institute no. 684

(AOAC, 1975).

A 1.0 g portion of the Hibiscus sabdariffa L. seed oil was placed in a 250 ml conical flask and

warmed. 25ml of methanol was added with thorough stirring, followed by 2 drops of

phenolphthalein indicator and a drop of 0.14 M NaOH solution. The contents were then titrated

with 0.14 M NaOH solution until a light pink color which persisted for 1 minute was observed.

The end point was recorded and used to calculate the FFA as shown below;

FFA (as oleic) = Titre × M ×28.2

weigh t of sample

Where;

M = Molarity of the base.

16

28.2 is a constant in calculation.

2.6.2 ACID VALUE (AV)

Reagents

i. Methanolii. Phenolphthalein indicator

iii. 0.14 M NaOH

Procedure

The method used for the determination was that of the British standards institute no. 684

(AOAC, 1975).

A 1.0 g portion of the Hibiscus sabdariffa L. seed oil was placed in a 250 ml conical flask and

warmed at 10oC. 25 ml of methanol was added while thoroughly stirring, followed by the

addition of 2 drops of phenolphthalein indicator and a drop of 0.14 M NaOH solution. The

contents were then titrated with 0.14 N NaOH solution until a light pink color, which persisted

for 1 minute was observed. The endpoint was recorded and used to calculate the acid value as

shown below;

Acid value = % FFA (as oleic) x 1.99

2.6.3 PEROXIDE VALUE (PV)

Reagents

i. Saturated potassium iodide solutionii. Glacial acetic acid

iii. Chloroformiv. 0.1 N Sodium thiosulphate

Procedure

The method used was that of the British standards institute no. 684 (AOAC, 1975).

17

A 1.0 g portion of the Hibiscus sabdariffa L. seed oil was placed in a 250 ml conical flask and 30

ml glacial acetic acid/chloroform (3:2 V/V) was added. The contents were shaken until they

dissolved. 1.0 ml of saturated potassium iodide was added followed by the addition of 0.5 ml

starch indicator. This was titrated with 0.1 N Na2S2O3 until the dark blue color just disappeared.

Blank determination was also carried out and the peroxide value calculated as shown below;

PV (mEq/kg oil) = (S−B ) ×1000 × N

W

Where;

S= titre volume of sample

B= titre volume of blank

N= normality of sodium thiosulphate solution

W= weight of oil sample

2.6.4 SAPONIFICATION VALUE (SV)

Reagents

i. 0.5 M hydrochloric acid

ii. Ethanol potassium hydroxide solution (0.5 M in 9 5 % ethanol)

iii. Phenolphthalein indicator

Procedure

The method used was that of the British standards institute 1995 (AOAC, 1975).

A 1.0 g portion of Hibiscus sabdariffa L. seed oil was placed in a 250 ml conical flask and 25 ml

of 0.5 M ethanol potassium hydroxide solution was added.

A reflux condenser was attached and the flask content refluxed for 30 minutes on a water bath at

30oC while swirling until it simmered. The mixture was then titrated against 0.5 M HCl using

18

phenolphthalein indicator while still hot. A blank determination was also carried out under the

same conditions and the saponification value calculated as shown below;

SV =(B−S ) ×28.05

W

Where;

B = titre value of blank

S = titre value of sample

W = weight of oil

2.6.5 IODINE VALUE (IV)

Reagents

i. Anhydrous chloroformii. Hanus solution

iii. 15 % potassium iodideiv. 0.1 N sodium thiosulphatev. 1.0 % starch indicator

Procedure

Several methods are available for iodine value determination but Hanus method (Association of

Analytical Chemist.1975) was used in this work (AOAC, 1975).

A 1.0 g portion of Hibiscus sabdariffa L. seed oil was placed in a 250 ml conical flask followed

by 30 ml Hanus solution and the flask stopped. The flask content was mixed and kept in the

drawer for 30 mins. It was then titrated against 0.1 N Na2S2O3 until the solution became light

yellow. 2.0 ml of 1.0 % starch indicator was added and the titration continued until the blue color

just disappeared. A blank determination was also carried out under the same conditions and the

IV calculated as thus;

19

IV = (B−S ) ×12.69 × N

W

Where;

B= blank titre

S= sample titre

N= normality of Na2S2O3

W= weight of oil

12.69 is a constant in the calculation.

2.7.0 PREPARATION OF FATTY ACID METHYL ESTER (FAMES)

Reagents

i. 5 ml of 95 % methanolii. 0.3 g KOH

iii. 15 ml CPSOiv. Anhydrous MgSO4

Procedure

The method used was that developed by the biodiesel team (AOAC, 1975). Methanol (10 ml)

was added to KOH (0.3 g) in a conical flask with slight heating at 30oC and slow stirring until

complete dissolution was achieved.

The alcoholic KOH was added to 15 ml of Hibiscus sabdariffa L. seed oil while it was stirring

slowly and heating at 30oC. The speed of the stirring was increase and allow to stir for few hours

until sign of separation was identified. The mixture was then slowly transferred to a separating

funnel and allowed to stand for 1 hour. Two layers became distinct and the glycerol layer (the

lower layer) was drained off. Magnesium silicate was added to the FAMES, swirled and allowed

to settle down in the separating funnel after which it was run off. This washing process was

repeated until the product was moisture free. The yield was calculated as shown below;

20

% yield of biodiesel = weigh t of biodiesel

weigh t of Hibiscus sabdariffa seed oil× 100

2.8.0 FUEL QUALITY PARAMETER TESTS

2.8.1 FLASH POINT (FP)

Apparatus

i. Thermometer (reading in °С)ii. 100 ml conical flask

iii. Hot plate

Procedure

An improvised method was used for this determination. A 5 ml portion of the biodiesel was

poured into a test tube set on a clamp and a hot plate, it was then heated at slow constant rate

(specify rate) on the hot plate. The flash point was taken at the lowest temperature when an

application of the test flame caused the vapor above the sample to ignite. This was also carried

out for the control, diesel D2 and the test sample, Hibiscus sabdariffa L. seed oil.

2.8.2 POUR POINT (PP)

Apparatus

i. Thermometer (reading in °С)ii. Cylindrical test tube

iii. Ice bathiv. Clamp stand

Procedure

An improvised method was used for this determination (Abayeh and Ugah, 2007).

The cylindrical test tube was filled with the biodiesel to the 5.0 ml mark and clamped with a

wooden clamp bearing a thermometer. The sample was then allowed to cool below 0°С in the

ice/salt bath. At this point it was removed and tilted on the clamp and the set up observed at

21

intervals. The lowest temperature at which the biodiesel was observed to flow was recorded as

the pour point. The same procedure was repeated for diesel fuel, D2.

2.8.3 CLOUD POINT (CP)

Apparatus

i. Thermometer (reading in °С)ii. Cylindrical test tube

iii. Ice bathiv. Clamp stand

Procedure

An improvised method was used for this determination (Abayeh and Ugah, 2007).

The cylindrical test tube was filled with the biodiesel to the 5.0 ml mark and clamped with a

wooden clamp bearing a thermometer. The test tube was placed in the ice/salt bath and the set up

inspected at intervals for cloud formation. The temperature at which a distinct cloudiness was

observed to appear at the bottom of the test tube was recorded as the cloud point of the biodiesel.

The test was carried out for Hibiscus sabdariffa L. seed oil and diesel D2.

2.8.4 DENSITY

Apparatus

i. Beakerii. Electronic weighing balance

Procedure

The weight of a small empty bottle was determined using an electronic weighing balance. The

bottle was then filled to the brim with the biodiesel and the weight of the bottle and the biodiesel

22

determined. This procedure was repeated with the diesel D2, and the density was calculated

using the formula shown below:

Density (ρ) =W 2−W 1

V

Where;

W 2=Weight of bottle + Sample

W 1=Weight of empty bottle

V=Volume of Sample

2.8.5 CALORIFIC VALUE (CV)

Apparatus

i. Burner (a locally made lamp)ii. Beaker(100 ml)iii. Wickiv. Thermometer (reading in o C)v. Stop Clock

Procedure

An improvised method was used for this determination (Abayeh and Ugah, 2007).

The wick was positioned in the locally made lamp. The weight of the empty lamp with 10 ml of

the biodiesel was taken. The wick was lit and the biodiesel was used to heat the beaker

containing 10 ml of water for 10 minutes after which the temperature of the water was recorded.

The same procedure was repeated for diesel D2 and the calorific value/content determined using

the formula

Calorific value = MCѲ

Where;

23

M = Mass of water

C = Specific heat capacity of water

Ѳ = Temperature rise of water after 10minutes

2.8.6 KINEMATIC VISCOSITY

Apparatus

i. U-tube Viscometerii. Pipette filleriii. Thermometeriv. 1.0L measuring cylinder

Procedure

The viscometer was placed in the 1.0L measuring cylinder filled to mark with water and

regulated to the appropriate temperature. The tube was then filled up to a graduation mark over

the left storage bulb with the biodiesel. The biodiesel was then sucked up to fill the higher

storage bulb in the right left of the tube and then released. The time taken for the biodiesel to

flow from the upper mark to the lower was observed and calculated. The kinematic viscosity of

the biodiesel calculated using the formula below:

Kinematic viscosity (Υ) = Absolute Viscosity (η)

Density (ρ)

Absolute Viscosity (η) = t−¿¿

Where;

t = time of flow of the sample

t0 = time of flow of the reference (water in this case)

The same procedure was repeated using diesel D2 and water, which was taken as the

reference.

24

2.8.7 CETANE NUMBER (CN)

The parameter was determined based on the formula proposed by Demirbas 1998 as there was no

enough biodiesel to carry out the test. The formula is given below

CN = 46.3+ 5458SV

−0.225 IV

Where;

SV =Saponification value of the oil

IV =Iodine value of the oil

2.8.8 FLAME TEST

Apparatus

i. Wickii. Watch glassiii. Test tube

Procedure

The wick was dipped in the test tube containing 5.0 ml of the biodiesel and then placed on a

watch glass. The wick was then lit and allowed to burn. The rate of burning, the color of the

flame werecolor of the flame was noted and recorded. The same procedure was repeated using

diesel D2.

2.8.9 COMBINED GAS CHROMATOGRAPHY-MASS SPECTROMETRY

The components of the ethylated oil were identified by a combined gas chromatography-mass

spectrometry (GC-MS) using GCMS-QP 2010 Shimadzu, Japan carried out at NARICT, Zaria.

This was achieved by injecting 8µL into a GCMS interfaced to a computer library search. The

GC column oven temperature (70o C, injecting temperature (250o C), flow control mode (linear

25

velocity), total flow (40.8 mL/min) column flow (1.80 mL/min), pressure (116.9 kpa), linear

velocity (49.2 cm/sec), purge flow (3.0 mL/min), and split ratio (20.0) were employed for this

analysis

2.9.0 PREPARATION OF REAGENTS

2.9.1 Preparation of 0.14 M NaOH

NaOH (1.4 g) was dissolved in a small quantity of distilled water and the solution transferred

into a 250 ml volumetric flask and made to the mark with distilled water.

2.9.2 Preparation of glacial acetic acid/chloroform (3:2 V/V) solution

Glacial acetic acid (150 ml) ad chloroform (100 ml) was mixed in a 250 ml volumetric flask and

the resultant solution kept for use.

2.9.3 Preparation of saturated potassium iodide solution

Excess potassium iodide was dissolved in a 250 ml volumetric flask containing distilled water

until it was ensured that the crystal no longer dissolves.

2.9.4 Preparation of 0.1 N sodium thiosulphate solution

Sodium thiosulphate (1.98 g) was dissolved in a small quantity of distilled water. It was then

transferred into a 250 ml volumetric flask and made to the mark with distilled water.

2.9.5 Preparation of 0.5 M HCl

26

Concentrated HCl (10.8 ml) was measured into a 250 ml volumetric flask containing some

quantity of distilled water and was made up to the mark with distilled water.

2.9.6 Preparation of 0.5 M ethanolic potassium hydroxide solution

KOH (10 g) was weighed, dissolved in a small quantity of 95 % ethanol and made up to the mark

with 95 % ethanol in a 250 ml volumetric flask.

2.9.7 Preparation of Hanus solution

Iodine (3.3 g) was dissolved in a small quantity of glacial acetic acid and made up in a 250 ml

volumetric flask with glacial acetic acid. The solution was heated on a hot plate and stored in a

brown stoppered bottle in the dark.

2.9.8 Preparation of 15 % potassium iodide solution

Potassium iodide (15 g) was dissolved in a small quantity of distilled water and made up to the

mark in a 100 ml volumetric flask with distilled water.

2.10.0 PREPARATION OF INDICATORS

2.10.1 Preparation of 1% starch indicator solution

Soluble starch (1.0 g) was weighed and mixed with water in 100 ml beaker and warmed water

(50 ml) was added while stirring. The solution was heated until a clear solution resulted. It was

then made to the 100 ml mark with water, allowed to cool and used immediately.

2.10.2 Preparation of phenolphthalein indicator

Phenolphthalein (1.0 g) was weighed and dissolved in 100 ml of absolute alcohol.

27

CHAPTER THREE

3.0 RESULTS AND DISCUSSION

3.1 RESULTS

Results for the moisture content of three different samples of Hibiscus sabdariffa L. seed sample

is shown in Table 2.

Table 2: Moisture content and oil recovery of Hibiscus sabdariffa L. seed

Weight of sample before drying(g)

Weight of sample after drying(g)

Percentage moisture (%)

5.85.95.7

5.55.55.7

5.176.705.17

The result of the moisture content of the three different samples all fall within the long period of (5-7 %) moisture content. The percentage oil content (12.83%) is low as shown in Table 4.

The results of the odour, color and texture of Hibiscus sabdariffa L. seed oil is presented on table

3. A comparison of oil quality parameters of Hibiscus sabdariffa L seed oil with those of

Citrullus lanatus seed oil and castor seed oil presented in Table 4.

Table 3: Odour, color and texture of Hibiscus sabdariffa L. oil

28

Extract (sample) Odour Color TextureABC

PleasantPleasantPleasant

Darkish-brownDarkish-brownDarkish-brown

ViscousViscousViscous

29

Table 4: A comparison of oil quality parameters of Hibiscus sabdariffa L. and those of Citrullus lanatus seed oil and castor seed oil.

Parameters Hibiscus sabdariffa L. seed oil

Citrullus lanatus seed oil (CLSO)

Castor seed oil (CSO)

Moisture % 5.68 4.91 4.15Oil recovery %Color

12.83Darkish-brown

43.32Yellow-brown

33.20Amber

OdorSpecific gravity g/mlViscosity mm2/sDensity g/mlAcid value mgKOH/g oilPeroxide Vale meq/kgIodine value g/100gSaponification value meq/kgFree fatty acid %

Pleasant0.904

30°С, 29.130.967

16.502639.46

151.478.29

Pleasant0.86040°С, 10.73N.A0.5018.7558.42115.94N.A

N.A0.96028°С, 9.4247N.A1.148N.A87.72175-187N.A

N.A = Not Available

Fig. 5: Separation of biodiesel from glycerol.

The biodiesel yield was worked out to be 33.3%, this is extremely low, However, it still fall

within the requirement for the yield of biodiesel in oil which is 20 % of the oil.

30

Prior to use as a commercial fuel, the biodiesel must be analyzed in the laboratory to ensure that

it meets the ASTM specifications. The results of some of these parameters that were analyzed are

shown in Table 5 below. Comparison of the results of fuel quality parameters of HS FAEES with

other investigated FAEES and with standards is shown in Table 6.

Table 5: Results of the fuel quality parameters of Hibiscus sabdariffa L., and D2

Fuel properties Hibiscus sabdariffa L.

D2

Kinematic viscosity (30°С), mm2/s

33.44 2.65

Density, kgm-3 871 835Flash point, °CCloud point, °CPour point, °CCetane number*Calorific value, JFlame test

317-3

-1973.45

12472Burns slowly withA dark and thick smoky flame

1400-2-12188Burns vigorously with a dark and thick smoky flame

*CN = 46.3 + 5458/SV -0.225 IV. Source (Demirbas, 1998.)

31

Table 6: Comparison of the results of fuel quality parameters of HS FAEES with other

investigated FAEES and with standards

Parameter HS FAEES

TN FAEES

S FAEES

D2 ASTM D6751 Limits

EN 14214 limits

Density, g/cm3

Kinematic viscosity, mm2/sFlash point, °CCloud point, °CPour point, °CCalorific value, JCetane number*

0.871033.44

317-3-191247273.45

0.88113.00

1207.7-3.816204NA

0.88455.75

168-5NANA56

0.83502.65

1400NA12188-

0.8200 min1.9-6.0

130minNANANA47min

0.86-0.93.5-5.0

>101NANANA51min

*Demirbas 1998 min = minimum

HSFAEES= Hibiscus sabdariffa L. seed fatty acid ethyl ester

TNFAEES=Thevitia nerifolia fatty acid ethyl ester

SFAEES= Soybean fatty acid ethyl ester

D2=Diesel fuel

N.A= Not Available

The result of fuel properties of ethyl esters of Hibiscus sabdariffa L. seed oil are compared with soy oil and Thevitia nerifolia ethyl esters, diesel fuel, ASTM D6751 and EN 14214 standards in Table 6.

Table 7 shows the GC-MS analysis result of the biodiesel from Hibiscus sabdariffa L.

32

Table 7: GC-MS ANALYSIS OF BIODIESEL FROM HIBISCUS SABDARIFFA L.

Peak no. Retention time (mins)

% peak Area

% peak height

Masses of fragment ions (M/Z) (% abundance). Proposed Identity

1 16.017 22.16 25.63 88(100),101(50),55(20),57(18),284(18),70(17),241 (15),239(12),213(5),115(M+,3)

Palmitic acid, ethyl ester (Hexadecanoic ethyl ester).

2 17.558 37.55 31.83 81(100),67(90),95(80),55(60),41(45),109(30),262(25),308(15),123(12),121(12),135(10),164(5),178(4),220(M+,3)

Linoleic acid, ethyl ester (9,12-octadecadienoic acid ethyl ester).

3 17.633 37.51 31.50 55(100),69(65),83(61),88(60),97(55),98(45),43(45),101(41),57(35),264(25),266(18),222(17),123(13),180(10),310(M+,10)

9-octadecenoic acid, ethyl ester (E)-9-octadecenoic acid ethyl ester).

4

5

17.851

19.007

5.94

2.84

7.41

3.63

88(100),101(55),43(40),55(28),55(28),57(22),70(17),89(12),312(12),269(11),213(10),115(8),60(M+

,5)

55(100),41(88),81(71),67(70),69(42),83(37),68(36),95(35),79(34),99(25),121(M+, 15)

Ethyl n-octadecanoate (octadecanoic acid, ethyl ester).

unknown

From the table, it can be observed that the retention time from peak no. 1 to peak no. 5 steadily increase from 16.017-19.007 min. The proposed identities of the components shows the presence of ethyl ester, but the last component does not show any semblance to the identities in the GC-MS library.

33

3.2 DISCUSSION

From Table 2, it can be observed that the moisture content of Hibiscus sabdariffa L. seed (5.17

%) is quite high compared to those of Citrullus lanatus seed oil (4.91%) and castor seed oil (4.15

%) but shows that the seed is within the range (5-7%) of the long term storage period seed,

implying that the seed can be stored for a long time without deteriorating.

The average oil recovery of Hibiscus sabdariffa L. seed oil (12.8 %) which is quite low as

compared to those of Citrullus lanatus and castor seed oil (Table 4). This would be a great

disadvantage in the use of Hibiscus sabdariffa L. compared to other oils with respect to the oil

price and the oil yield. The oil recovery for Hibiscus sabdariffa L. (12.83%) is low compared to

Citrullus lanatus seed oil (43.32) and Castor seed oil (32.20). The oil was observed to be

odourless, this is one of the qualities required of a good commercial oil. The free fatty acid

(FFA) value normally indicates the condition of the oil. It is often calculated as oleic acid

because British Standards Institute expresses it as the most abundandant acid in the oil. The FFA

value obtained for Hibiscus sabdariffa L. (8.29%) as compared to NAFDAC standard (6.0%) is

high and therefore, does not support good value as edible oil. (Christie, 1982). The specific

gravity of Hibiscus sabdariffa L.oil as obtained was 0.904. this falls within the value 0.89-0.92

reported for edible oil (Odufoye, 1998).The acid value, peroxide value, saponification value, and

the iodine value are obtained as 16.50, 26, 151.47, and 39.46 respectively, the implication of

these values are that the oil will require acid pretreatment because of its high acid value, it could

easily become rancid because of its high peroxide value. The biodiesel properties such as;

kinematic viscousity (33.44 mm2/s), density (871 kgm-3), flash point (317 oC), cloud point (-3oC),

pour point (-19oC), cetane number (73.45), calorific value (12472 J), all fall within acceptable

values for biodiesel production.

33

The GC/MS analysis performed on the ethylated oil revealed that most of the free fatty acids

(FFA) were successfully ethylated except for component 5 (unknown identity) with retention

time of 19.007 min. from the summary of the GCMS analysis for Hibiscus Sabdariffa L.

ethylated oil, the following fatty acid esters identities are proposed:

Component 1 with retention time of 16.017 min (base peak) may be palmitoic ethyl ester,

component 2 with retention time of 17.558 min (base peak) may be linoleic acid ethyl ester,

component 3 with retention time of 17.633min (base peak) may be 9-octdecenoic acid ethyl

ester, componetnt 4 with retention time of 17.851min (base peak) may be ethyl n-octadecanoate,

component 5 with retention time of 19.007 is unknown.

34

CHAPTER FOUR

4.0 SUMMARY, CONCLUSION AND RECOMMENDATION

4.1 SUMMARY

In this work, the seed oil of ‘Zobo’ (Hibiscus sabdariffa L.) was evaluated for the first time for

its viability as a feedstock for biodiesel production. The oil quality characteristics of the seed oil

were; iodine value (IV), 39.46 g iodine/100g oil, peroxide value (PV), 26 meq peroxide/kg oil,

acid value (AV), 16.50 mg KOH/kg oil, saponification value (SV), 151.47 meqKOH/kg oil, free

fatty acid (FFA), 8.29 % of oil, specific gravity (S.G), 0.904 g/ml oil and viscosity, 29.13 mm2/s

at 30 °C. The oil was transesterified using ethanol and potassium hydroxide and the parameters

were compared to that of petroleum diesel number 2 (D2). Fuel tests on the Hibiscus sabdariffa

L. seed oil methyl ester gave a high cetane number, 68.2 and a high flash point of 317 °C. Other

fuel properties of the biodiesel assayed were cloud point, pour point, viscosity, density and

calorific value and the results were; -3 °C, -19 °C, 2.20 mm2/s, 871 kgm-3 and 124272 J

respectively. The results obtained for the biodiesel was also compared with the American and

European standards for biodiesel (ASTM D6751 and EN14214) and were found to fall within the

acceptable limits, implying that Hibiscus sabdariffa L. fatty acid ethyl ester could be used alone

or as blends with diesel D2 in diesel combustion engines in tropical regions like Nigeria. GC/MS

analysis of the ethylated oil revealed the presence of 4 ethyl ester (palmitoic ethyl ester, linoleic

acid ethylester, 9-octadecenoic acid ethyl ester, and ethyl-octadecanoate).

4.2 CONCLUSION

The preliminary investigation indicates that Hibiscus sabdariffa L. seed oil is an economically

non-viable oil source because of its low oil content (12.83%). The oil quality parameters shows

35

that the oil is composed of moderately long chain fatty acids with a moderate degree of

unsaturation, thus low susceptibility to oxidative rancidity making it a good feedstock for

biodiesel production.

After transesterification which yielded 33.3 wt % biodiesel, the fuel quality parameters of the

FAEES also indicates that the fuel can be used in tropical regions like Nigeria. It has high flash

point making it free from fire hazards associated with fuel during storage and transportation. All

of the tested fuel quality parameters conform to standards for biodiesel fuels. The result of the

flame test also showed the advantage biodiesel has over petrodiesel as it shows a relative

decrease in the emission of greenhouse gases especially associated with petrodiesel.

In conclusion, from all the results obtained in this research, it was seen that Hibiscus sabdariffa

L. seed can serve as a good feedstock for biodiesel production. It was also seen that the resultant

fatty acid methyl ester can be used alone in diesel engines or as blends with petrodiesel as it

satisfies all the fuel quality parameters tested.

4.3 RECOMMENDATIONS

The result obtained in this research provides some important information that could be exploited

for potential use of the seed oil in biodiesel production. It is therefore recommended that further

researches be carried out to determine if the ethyl ester could also be used in diesel engines or as

blends with petrodiesel.

It is also recommended that researches be diversified in the field of biodiesel production. Nigeria

today is blessed with a variety of plants both edible and non edible which has not been exploited.

Therefore researchers should intensify their efforts in exploring the use of these plants as this

36

will reduce the nation’s dependence on petrodiesel and provide job opportunities in the labour

market.

37

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