1

AL AKHAWAYN UNIVERSITY IN IFRANE

SCHOOL OF SCIENCE & ENGINEERING

EGR 4402

Capstone Design

Valorization of waste coffee grounds into biodiesel

Final Report

Done by:

Chaima Boualdab

Supervised by: Dr. Samir El Hajjaji

Spring 2016

3rd of May

2

Acknowledgements

I would like to express my deepest and sincere gratitude to my supervisor Dr. Samir El Hajjaji

for his guidance and excellent supervision. I would like to thank him for the considerable amount

of time and energy he dedicated in order to have regular meetings at the chemistry lab where I

performed all the experiments that represent the core of my project.

I am also thankful to Mr. Abdellatif Ouddach, the lab technician, who was always available and

ready to help and provide me with the chemicals and equipment needed.

I extend my gratitude to Al Akhawayn University and to the School of Science and Engineering

for allowing me to have this great experience.

Last but not least, I owe my profound gratitude to my parents, whose support, prayers and love

helped me be where I am today.

Above all, I thank god, who enabled me with perception, power and motivation to be able to

present this project.

Supervisor’s Signature:

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3

Table of contents Abbreviations

List of figures

List of tables

Abstract

1. Introduction 1

1.1 What is biodiesel? 1

1.2 Biodiesel feedstocks 2

1.3 Biodiesel Production Process 2

1.3.1Transesterification procedure 2

1.3.2 Influence of reaction parameters 3

1.3.2.1 Alcohol to oil molar ratio 3

1.3.2.2 Amount of catalyst 4

1.3.2.3 Reaction time and temperature 4

1.4 Valorization of waste coffee grounds 4

2. STEEPLE analysis 6

3. Experimental results 7

3.1 Chemicals and Equipment use 7

3.2Materials and methods 8

3.2.1 Coffee 8

3.2.2 Oil Extraction 8

4

3.2.2.1 Effect of the solvent 11

3.2.2.2 Effect of water 12

3.2.2.3 Effect of time 13

3.2.2.4 Effect of wet SCG drying conditions 14

3.2.2.5 Effect of ultra-sonication 15

3.2.2.6 Optimized conditions 16

3.2.2.7 Optimized coffee oil extraction procedure 16

3.2.3 Biodiesel production 21

3.2.3.1 Conditions 21

3.2.3.2 Trial 1 22

i- Specification of reaction parameters 22

ii- Transesterification reaction 23

a- FFA content in coffee

oil 2

4

b-The presence of water in potassium methoxide solution 25

3.2.3.3 Trial 2 26

i- Specification of reaction parameters 26

ii- Transesterification reaction 27

3.2.3.4 Optimized biodiesel production from sodium methoxide as a

catalyst 28

i- Specification of reaction parameters 29

ii- Transesterification procedure 29

iii- Layer separation phase 30

3.2.4 Characterization and Quality test on Biodiesel 31

3.2.4.1 Thin layer chromatography test 31

3.2.4.2 Calorimetry 33

i-Principle of oxygen bomb calorimeter 34

ii-Calorimetry experiment 34

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3.2.4.3 Density 41

Conclusion 41

References 42

Appendix 43

iv

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Abbreviations

ASTM American society for testing material SCG Spent coffee grounds b.p. boiling point FFAs Free fatty acids min minutes NaOH sodium hydroxide KOH potassium hydroxide Rf retention factor rpm revolutions per minute temp. temperature TLC Thin layer chromatography MeOH Methanol EtOH Ethanol H3PO4 Phospohoric acid NaOMe Sodium Methoxide w. By weight v. By volume MG Monoglycerides DG Diglycerides

1

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List of figures

Figure 1: Example of biodiesel molecule: methyl oleate, C19H36O2 Figure 2: General reaction for transesterification reaction Figure 3: Vacuum filtration over cotton Figure 5: Ultra-sonication using an ultrasonic cleaner Figure 6: Oil extraction in a vessel under high pressure Figure 7: Oil extraction at atmospheric pressure Figure 8: Vacuum filtration over a sintered funnel Figure 9: Distillation under vacuum Figure 10: Soxhlet apparatus typically used in a solid-liquid extraction Figure 11: Oil preheating step

Figure 12: The chemical equation of the Transesterification reaction performed

Figure 13: Reaction mixture in the separatory funnel

Figure 14: Separation of layers of biodiesel and glycerin Figure 15: Layer separation of biodiesel, aqueous mixture and soaps

Figure 16: TLC test in progress

Figure 17: Compounds separation using TLC plate

Figure 18: Oxygen bomb calorimeter utilized in the determination of ΔHcomb

Figure 19: Oxygen bomb

Figure 20: Schematic of the oxygen bomb Figure 21: Oxygen bomb connected to the oxygen cylinder Figure 22: Schematic of the oxygen bomb calorimeter

2

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List of tables and Graphs

Table 1: Optimization of the coffee oil extraction procedure by using unused coffee and waste coffee

Grounds

Table a: Local coffee consumption in Ifrane’s cafés.

Table b: The effect of the solvent on the amount of oil extracted

Table c: The effect of the presence of water in SCG on the amount of oil extracted

Table d: The effect of heating time on the yield of oil extracted

Table e: Effect of wet SCG drying conditions on the yield of extraction

Table f: Effect of ultra-sonication on the yield of oil extracted

Table 2: Transesterification of coffee oil with MeOH as a catalyst

Table 3: Transesterification of coffee oil with NaOMe as a catalyst

Table 4: Scale-up of the transesterification of coffee oil with NaOMe as a catalyst

Table 5: Heat content of diesel and biodiesel

Table 6: Densities of coffee oil, biodiesel and diesel.

Graph 1: Results obtained in the optimization of coffee oil extraction with unused coffee

Graph 2: Results obtained in the optimization of coffee oil extraction with waste coffee grounds

Graph 3: Heating curve of benzoic acid

Graph 4: Heating curve of diesel

Graph 5: Heating curve of biodiesel

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Abstract

Biodiesel production is a topical field of research which has become a steadily growing industry

over the past decade. The importance given to biodiesel production can be explained by its

environmental benefits and the continual rise of oil prices. Biodiesel is then a promising solution

to the environmental degradation of our planet as it produces lower exhaust emissions when

compared to conventional fuels. As a matter of fact, it cuts down greenhouse gas emissions by

more than 52% compared to petroleum diesel.1 This alternative fuel can be made from renewable

sources such as animal fats, greases and vegetable oils. In this context, the purpose of this work is the valorization of waste coffee grounds as a starting

material for biodiesel production. Transesterification is the method used throughout, hence its

processes and downstream operations including oil extraction are described. Furthermore, several

tests that unveil the quality and perform a characterization of the produced biodiesel have been

applied and described as well. The goal of this work is to emphasize on the feasibility of conversion

of coffee oil, extracted chemically from waste coffee grounds collected locally, into a biofuel:

biodiesel.

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1. Introduction

1.1 What is biodiesel?

Biodiesel, often referred to as B100 in its pure form, is a biodegradable and environmental friendly

fuel that serves as an alternative to conventional fossil diesel. This clean renewable fuel can be

derived domestically through chemical processes from a variety of oils, fats and greases. Biodiesel

is defined by ASTM International as a mixture of long-chain monoalkylic esters from fatty acids

(Figure 1) obtained from renewable resources that can be readily used in diesel engines.2 Not only

does this latter meet most of the standard properties of petro-diesel, but it also has many

characteristics that makes it a very promising alternative source of energy.

Figure 1: Example of biodiesel molecule: methyl oleate, C19H36O2.

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1.2 Biodiesel feedstocks

Biodiesel can be produced from a range of organic and renewable raw materials. These latter

include either fresh or waste vegetable oils, oilseed plants, animal fats or algae oil. Different potential raw materials are then available for biodiesel production, however, edible oils

are currently the most used. The widely used oils are rapeseed oil (mainly in the European Union,

>80%), soybean oil (USA, Brazil), sunflower oil (France, Spain) and palm oil (Asia and Central

America).3 The availability of these edible oils explains their popularity in biodiesel production.

Since cost also matters in biodiesel production and edible oils account for food materials, the use

of non-edible vegetable oils has been considered and studied with promising results. In this regard,

technologies are also being developed to exploit cellulosic materials such as leaves, biomass

derived from waste, etc. Also, 26 species of plants containing oil in their seeds are reported to be

sources for biodiesel production. The most significant examples are: castor oil plant, cotton,

tobacco, karanja, jatropha, etc.3 These oils make a good alternative to edible oils if the problem of

water requirement related to their use are neglected. Used edible oils are another potential raw material for biodiesel production. They are called to

solve the problem of competition with food and cost concern. Besides, using the waste edible oil

for biodiesel production can help solve the twin problem of energy shortage and environmental

pollution. 3 For example, coffee oil falls within this category.

Another feedstock are animal fats. Their advantage is their competitive price.3

Lastly, with their high oil content (20% to 50%), microalgae have also been recognized to have

great potential for biodiesel production. The cultivation of microalgae does not require much land

but requires high levels of water, nutrients, minerals and CO2 for their growth. 3

1.3 Biodiesel Production Process

1.3.1 Transesterification procedure Basic transesterification is the most preferred method employed in biodiesel production. This

chemical process is a reaction between a triglyceride (a triester) and an alcohol with low molecular

weight (usually methanol or ethanol); during this process the ester is transformed into another one

through interchange of the alkoxy moiety. Transesterification is an equilibrium reaction and the

presence of a catalyst (usually NaOH or KOH) is favorable as it accelerates considerably the

equilibrium achievement.

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The chemical equation representing transesterification is as follows:

O

O

O

R1

R2

R3

O

O

O

Triglyceride

R4O

R4O

R4O

R1

R2

R3

O

O

O

O

O

O

Glycerin

+

BIODIESEL

+Catalyst

H

H

H

Alcohol

heat

R4O H3

Figure 2: General reaction for transesterificationreaction.

Typical conditions: R1,R2,R3 = long alkyl chains;

R4 = CH3; catlalyst = KOH or NaOH; heat = 60°C.

In the transesterification of vegetable oils, a triglyceride reacts with an alcohol in the presence of a

catalyst thus producing a mixture of shorter esters (called “biodiesel”) and glycerol as a co-product.

Mechanistically, the process is a sequence of three consecutive and reversible equations where di-

and mono-glycerides are formed as intermediates. Besides, these products can be observed in a

reaction mixture when the transesterification reaction is not completed yet.

Other purification steps are necessary after the transesterification in order to ensure the product

complies with stringent international standards and specifications known as ASTM D6751 in the

USA and EN14214 in Europe (Appendix).

1.3.2 Influence of reaction parameters

The transesterification reaction requires the specification of reactants’ quantities based on

the oil’s quantity to be used. This is done by determining first the exact alcohol to oil molar ratio.

1.3.2.1 Alcohol to oil molar ratio

According to the work performed by H. D. Hanh et al., 4 the use of methanol as the alcohol, KOH

as the catalyst and alcohol to oil molar ratio of 6:1 resulted in a 90% conversion from triolein oil.

The ratio of oil to alcohol of 1:6 can be explained by the fact that an excess of alcohol is necessary

since the reaction is reversible. The excess plays a role in driving the equilibrium of

transesterification towards the direction of ester formation.4

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1.3.2.2 Amount of catalyst The amount of catalyst also affects the yield of conversion in the transesterification procedure. The

conversion increases by increasing the amount of catalyst from 0.5%w. to 1.5%w. But, an increase

from 1.5%w. to 2.5%w. resulted in inversed results as it promoted soap formation. However, the best

yield that was obtained by H. D. Hanh et al. was by using an amount of KOH of 3%w.4

1.3.2.3 Reaction time and temperature It is proven that the percentage of conversion of the reaction keeps increasing to reach its maximum at

60min. The conversion percentage remains nearly constant afterwards. Also, the temperature of

50°C is defined as the minimum as any temperature below would make the oil viscous. Yet, the

maximum temperature used without evaporating the methanol is 65°C.5

1.4 Valorization of waste coffee grounds Coffee production and consumption have known a significant rise during the last decades.

Currently, 8.5 million tons of coffee beans are being consumed yearly worldwide.6

According to the international coffee organization the demand is predicted to reach 10.55 million

tons a year by 2020, in other words an increase by nearly 25% over the coming 5 years. 6

Concerning Morocco, the average annual coffee consumption is around 27 000 tons, which

represents a per capita consumption of 0.9 kg. This Moroccan consumption accounts for only 0.32%

of the world consumption.

As for the local consumption, a survey was conducted to gather the monthly coffee consumption of

the cafés in Ifrane. The following table summarizes the information gathered:

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Café Consumption (kg/month)

La paix 120

Salon de thé 40

Forest 50-60

Beathoven 60

Café marché 60-90

Igloo 30

Vittel 200

Akhawayn(marché) 30-60

Itrane 80

Salam 72

Crystal Palace

60

Café marché -(a)

Café Slawi -

Café timedikin 1 -

Café timedikin 2

AUI Sodexo

AUI Newrest

-

15

100

Total 917-927

(a) Undisclosed

Table a: Local coffee consumption in Ifrane’s cafés.

The survey made shows that a quantity of 917 kg to 927 kg of coffee is being consumed each

month locally in Ifrane.

It goes without saying that more coffee consumption implies equally an increase in the amount of

coffee waste generated. Thus, solutions viable economically and technically and which address this

waste management are needed. The complex composition of waste coffee grounds and their

encompassment of various chemical compounds suggest their possible use in many applications.7

For example, they can be composted or incinerated when not buried in a landfill. However these

low-value applications could be complemented or replaced by a more interesting one: the

conversion of their residual oil into biodiesel. Spent coffee grounds, SCG, have a significant oil

content (10-20 %w.)7

which can be retrieved and used for biodiesel production. Therefore, the

exploitation of SCG is a win-win process as it will solve the twin problem of their disposal and

global energy shortage. The goal of the capstone project described herein is to prove the feasibility of the conversion of

coffee oil, extracted chemically from waste coffee grounds collected locally, into a biofuel:

biodiesel.

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2. STEEPLE analysis This project will certainly be very beneficial to the society as it is one great way to introduce

biodiesel as a good and affordable biofuel in Morocco. It has societal and ethical implications which include the following: Social and Economical: It may help café owners to raise their revenues by for instance producing

biodiesel from their own waste coffee grounds generated daily.

Alternatively these owners could equally generate a moderate income

simply by selling their unexploited waste coffee grounds to a biodiesel

producer.

Technological: It could potentially develop a new technology to better valorize waste

coffee grounds generated in cafés and households.

Environmental: It will promote the use of an unexploited renewable energy source that

reduces greenhouse gas emissions significantly.

Political: If this project is applied in all cafés in Morocco, it will help enhance the

eco-friendly image of our country in the world. This is particularly

important now given that Morocco will be hosting the COP22

conference in November 2016.8

Legal: This project could be extended to all cafés in Morocco providing there

are no legal constraints.

Ethical: This project could be seen as one way to tackle the issue of second-hand

coffee brewing that is allegedly practiced by some cafés in Morocco.

Though this practice is not widely spread, it raises grave ethical

concerns.

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3. Experimental results

3.1 Chemicals and Equipment used

Methanol used was 99.5% pure and supplied by VWR. Hexane was 99% pure and supplied by Sigma Aldrich. Phenolphthalein was supplied by Sargent-Welch, USA., and was used as a 1% solution in ethanol.

Potassium permanganate (KMnO4) supplied by Sargent-Welch, USA, was used as a 1% solution in

4% NaOH for the TLC staining bath. Potassium hydroxide, 86% pure,was supplied by Fluka, Switzerland. Sodium sulfate was supplied by J.T.Baker, USA. Sodium methoxide solution in methanol, 5.4M (30 %w.) was provided by Acros Organics, USA.

Ethyl acetate was supplied by Sigma Aldrich. Silica gel was supplied by Fluka, Switzerland.

Phosphoric acid solution used in the washings of biodiesel was made from an 85% phosphoric acid

supplied by Fluka, Switzerland. Medical grade oxygen used in bomb calorimetry measurements was supplied by Maghreb Oxygen,

Morocco.

Oil samples were centrifuged in a 5500 rpm Hettich zentrifugen centrifuge, model EBA 30 or in a

2700rpm clay Adams/ Becton Dickinson centrifuge, model 420227. All reactions were heated and stirred by using a digital stirring hotplate with external platinum probe.

Either a VWR VMS-C7 advanced series, or a DLab MS-H280-pro. Weights were measured either with a readability of 0.01g with an AND balance, model EK610i, or

with a readability of 0.05g with a KERN balance, model KB10K0.05N or with a readability of

0.0001g,with an OHAUS balance model AS120. Vacuum distillations and vacuum filtrations were performed by means of piston-powered vacuum

pump capable of generating a pressure of 0.85 atm and an air flow of 38 l/min. Water content in waste coffee grounds was determined accurately at 100°C with of a VWR oven,

model 1300U.

Occasionally, coffee samples were mixed with hexane by means of a VELP scientifica vortex shaker,

model Zx3.

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Ultrasonication was performed with a Branson ultrasonic cleaner, model 1210-EMT

(50W, 47 kHz).

The TLC plates are made of a silica gel matrix supported on plastic (polyethylene terephthalate) and

were supplied by Fluka, Germany. Heat contents were measured by means of a Parr 1344EE oxygen bomb calorimeter.

3.2. Materials and methods

3.2.1. Coffee During the four first experiments, unused coffee supplied by brand “carrefour”, type “Pur Arabica,

Moulu, Doux” was used for the sole purpose of determining the optimized conditions for oil extraction.

These optimized conditions could then be applied in the oil extraction on waste coffee grounds (residual

coffee capsules of SCG) collected from “La Paix”, a local café in Ifrane. The SCG were dried at a

temperature of 150°C for 2 hours prior to their use throughout the rest of the experiments.

3.2.2. Oil Extraction Production of biodiesel from SCG is a two-stage sequence. The first stage is the oil extraction; the second

one is a transesterification reaction. Multiple experiments were conducted in order to identify the most

adequate operating conditions to perform the oil extraction procedure. Throughout these experiments, coffee

grounds supplied by “carrefour”, “Pur Arabica, Moulu, Doux“were used. Table 1, Graph 1 and Graph 2 report the results obtained in the different optimizations performed.

They will be referred to in the following sections.

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Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of oil

extracted

(g/100g

coffee)

1 Unused

coffee,(a) 10 g

Acetone

50 mL

5 60°C 160 7.5

Hexane

50 mL 8.8

2 30 14.8

3 70°C 10.5

4 0

5 Waste coffee

grounds

wet,(a)(b) 10g

Hexane

50 mL

5 70°C 30 1.58(c) / 4.4(d)

6 Waste coffee

grounds dry,(a)

10g

10 10.9(e)

7 60 7.5(f)

8 90 7.9(f)

9 Waste coffee

grounds dry,(g)

300g

Hexane

1500 mL

0 30 9.48/10.30

(a) supplied by Carrefour, type “Pure Arabica, Moulu, Doux” (b) water content : 64% w. (c) based on the amount of wet coffee used (d) based on the actual coffee content (36% w.). (e) drying : 100°C, 4h. (f) drying : 100°C, 24h. Loss of yield presumably caused by excessive drying. (g) water content : 62.97% w. Drying : 150°C, 2h. Origin: La Paix.

Table 1: Optimization of the coffee oil extraction procedure by using unused coffee and waste coffee

grounds.

10

(g/1

00

g c

off

ee)

Am

ou

nt

of

oil

extr

act

ed

16 14 12 10

8

6

4

2 0

14.8

10.5

7.5 8.8

1 2 3 4

Entry from table 1

Graph 1: Results obtained in the optimization of coffee oil extraction with unused coffee.

Am

ou

nt

of

oil

extr

act

ed

(g/1

00g

co

ffee

)

12 10

8

6

4

2

0

10.9 9.48

7.50 7.90

4.40

1.58

5 6 7 8 9

Entry from Table 1

Graph 2: Results obtained in the optimization of coffee oil extraction with waste coffee grounds.

The two graphs are a visual representation of the results presented in Table 1.

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3.2.2.1. Effect of the solvent Two solvents were tested in order to evaluate their suitability in the oil extraction procedure. The two

solvents tested were hexane (C₆H₁₄) and acetone ((CH₃)₂CO). In a 100mL round-bottom flask, 20g of

unused coffee was mixed with 50mL of acetone (Table a, entry 1); in a second flask another 20g of

coffee was mixed with 50mL of hexane (Table a, entry 2). Both flasks were irradiated with ultrasounds

for 5min to promote a faster diffusion of the oil in the solvent. Each flask was then fitted with a water

condenser and heated for 30min at 60°C. Finally, a vacuum filtration over cotton (Figure 3) followed

by a centrifugation (7000 rpm, 5 min) afforded a clear coffee oil solution free of any solid. This solution

was heated at 70°C to evaporate the solvent and get the solvent-free oil.

The retrieved oil was then weighed and the extraction yield calculated. As Table a shows, acetone

and hexane gave a yield of 7.5% and 8.8% respectively. So hexane was the solvent that enabled to

get a higher oil recovery. Therefore, hexane is the solvent which was selected to perform further

extractions throughout this work.

Figure 3: Vacuum filtration over cotton.

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Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of

oil extracted

(g/100g

coffee)

1 Unused

coffee

coffee,(a)

10g

acetone, 50

mL

5 60°C 160 7.5

2 hexane , 50

mL 8.8

(a) supplied by “Carrefour” , type”Pure Arabica, Moulu, Doux”

Table b: Effect of the solvent on the amount of oil extracted.

3.2.2.2. Effect of water

The next important matter to be investigated was the effect of the presence of water in SCG on the oil

extraction yield. To this end, coffee oil was then extracted from both dried and wet SCG. 10g of SCG

were dried in an oven for 5 hours at a temperature of ca. 90 °C prior to the oil extraction procedure. We

could then calculate the water content which was found to be 64.8%w. Once dried, the SCG was mixed

with 50 mL of hexane, the previously selected solvent, and the mixture was irradiated for 5 min by

using ultra-sonication. Finally, the mixture was heated for 30min at 70°C to evaporate the solvent. The

extraction yield calculated was 10.9% (Table a, entry 1).

The same conditions were set for the second experiment (Table a, entry 2) except this time a

sample of wet SCG was used instead of a dried one. The results were surprisingly low: 4.4% based

on the actual coffee content (36% w.), and 1.58% based on the amount of wet coffee used.

In conclusion, the SCG have to be dried prior to their use as they afford a greater oil extraction

yield.

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Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of

oil extracted

(g/100g

coffee)

1 Waste

coffee

grounds,

wet,(a)(b) 10g

hexane , 50

mL

5

70°C

30 1.58(c) / 4.4(d)

2 10.9(e)

(a) supplied by “Carrefour”, type “Pure Arabica, Moulu, Doux”.

(b) water content : 64% w.

(c) based on the amount of wet coffee used

(d) based on the actual coffee content (36% w.).

(e) drying : 100°C, 4h.

Table c: Effect of the presence of water in SCG on the yield of extraction.

3.2.2.3. Effect of time

The next investigation dealt with the extraction time. It is quite relevant to know whether or not

the change of heating duration during the extraction step has an effect on the amount of oil

extracted. One flask containing SCG and hexane was heated for 60min while another one

containing the same amount of SCG and hexane was heated for 90 min. The SCG used were dried

in the oven prior to the experiment for 24 hours at 100°C. After the heating and filtration of the

content of each flask, the amounts extracted were then compared to eventually find that the yield

corresponding to the flask heated for 90min was 7.9%, while the one heated for 60min had a yield

of 7.5% (Table c, entries 1-2). These results lead to the conclusion that the heating time during

the extraction step is relevant.

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Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of

oil extracted

(g/100g

coffee)

1 Waste

coffee

grounds,

dry,(a)10g

hexane , 50

mL

5

70°C

60

7.5(b)

2 90 7.9(b)

(a) supplied by “Carrefour”, type “Pure Arabica, Moulu, Doux”. (b) based on the actual coffee content (36% w.).

Table d: Effect of heating time on the yield of oil extracted.

3.2.2.4. Effect of wet SCG drying conditions The drying time of the wet SCG should be taken into consideration as harsh drying conditions

result in yield loss. When the SCG were dried for 4h, the extraction yield was 10.9% (Table c,

entry 1), while it decreased to 7.9% and 7.5% when dried for 24h (Table d, entry 2 and 3). This

loss can be explained by the fact that the oil evaporated while drying the SCG.

Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of

oil extracted

(g/100g

coffee)

1

Waste

coffee

grounds,

dry,(a)10g

hexane , 50

mL

5

70°C

30 10.9(b)

2

10

60 7.5(c)

3 90 7.9(c)

(a) supplied by “Carrefour”, type “Pure Arabica, Moulu, Doux” (b) drying : 100°C, 4h. (c) drying : 100°C, 24h. Loss of yield presumably caused by excessive drying.

Table e: Effect of wet SCG drying conditions on the yield of extraction.

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3.2.2.5. Effect of ultra-sonication The effectiveness of the sonication step was the last thing left to check in order to finalize the

optimized conditions for the oil extraction step. Sonication is the very first step in the oil

extraction procedure, and is meant to promote a faster diffusion of the oil in the solvent by

means of ultrasounds.

The principle of this technique is to subject the SCG sample to ultrasonic waves (frequency:

40 kHz in our case) which will propagate in alternating high pressure (compression) and low-

pressure (rarefaction) cycles. During rarefaction, high-intensity sonic waves create small

vacuum bubbles or voids in the liquid, which then collapse violently (cavitation) during

compression, creating very high local temperatures. This phenomenon is thought to be helpful

in getting the oil out of the solid. Two experiments were then performed in parallel, again

providing the same conditions and only varying the sonication time. The first flask containing

unused coffee and hexane was mixed by using sonication for 5 min, then it was heated at 70°C

for 30 min (Table d, entry 1). The second flask containing the same amount of unused coffee

and hexane as the first one was not subjected to ultra-sonication. That flask was directly heated

at 70°C for 30 min (Table d, entry 2).

After the heating and filtration steps amounts of oil extracted were compared in each procedure.

The extraction yield using the sonication was 14.8% while it was 10.5% without sonication.

Therefore, the sonication step is definitely useful.

Entry Coffee used Solvent Sonication

time (min)

Temp. Extraction

time (min)

Amount of

oil extracted

(g/100g

coffee)

1 Unused

coffee,(a)10g

hexane , 50

mL

5

70°C

30 14.8

2 0 10.5

(a) Supplied by “Carrefour”, type “Pure Arabica, Moulu, Doux”

Table f: Table effect of ultra-sonication on the yield of oil extracted.

16

The apparatus employed to carry ou the sonication is shown in Figure 5.

Figure 5: Ultra-sonication using an ultrasonic cleaner.

3.2.2.6. Optimized conditions The optimization of the coffee oil extraction procedure allowed to draw many conclusions. They

are as follows: SCG should be dried prior to their use.

Excessive drying causes a loss in the oil extraction yield; therefore it should be done as

quickly and gently as possible. The solvent to be used is hexane. Extraction time should be 30 min (ideally 90 min) and extraction temperature should be 70°C. A preliminary ultra-sonication step is essential. Its time should be set to 10 min.

3.2.2.7. Optimized coffee oil extraction procedure After determining the optimized conditions for oil extraction, the next stage aimed at applying

these latter in order to produce a relatively important quantity of coffee oil that is to be used as the

raw material for biodiesel production. Hence, an experiment performed by scaling up the amounts

used previously; all quantities were increased 30 times fold (Table 1, entry 9).

Therefore, following paragraphs describe in details the optimized process conditions of oil

extraction.

17

Because using dried SCG affords a higher yield than wet SCG, the sample to be used throughout

the next experiment was dried for 2h at 150°C. The water content in the SCG was found to be

62.97% w. (Table 1, entry 9).

The first step in the oil extraction procedure is to actually weigh the appropriate amounts of coffee

grounds and solvent. A quantity of 300.00 g of waste coffee grounds (collected from the local café

La Paix) and 1500mL of hexane are used. In order to make the task of measuring 1500mL of

hexane easier, the density (ρ) of hexane was employed, to determine the desired mass and simply

add it to the flask containing 300.00g of waste coffee grounds

(ρ (hexane) gmLVdm 2.9821500mL

g655.0,

mL

g 0.655 ).

Unfortunately, ultra-sonication was impossible during this experiment as the ultra-sonication

machine available in the chemistry laboratory was much smaller than the flask used. Thus, swirling

was performed manually to mix the flask’s content. If possible, a preliminary ultra-sonication step

should definitely be performed and its time should be set to 10 min as it was proven earlier to be

effective.

The oil extraction time and temperature are then set to 30 min and 70°C respectively, as stated in

the optimized conditions determined previously. The flask was closed tightly by means of a glass

stopper wrapped with parafilm in order to prevent the solvent from evaporating. The flask was then

placed in a bain-marie to ensure a fast and homogeneous heating of the large flask used (Figure

6).

18

Figure 6: Oil extraction in a vessel under high pressure.

Even though this setup proved safe when used, its design, is fairly dangerous. This is because of

the buildup of pressure caused when heating the solvent in a closed system. Therefore, a new setup

was designed with safety in mind (Figure 7).

Figure 7: Oil extraction at atmospheric pressure.

19

After the oil extraction step, comes the filtration. Vacuum filtration over a sintered funnel was

used (Figure 8). However, after completing the filtration, some solid that inadvertently fell in the

flask were still present in the oil. So another filtration was required. This time it was done over

cotton wool, but it turned out to be very slow. So, another vacuum filtration over a sintered funnel,

was performed again, by using this time a two-neck 1L round-bottom flask (the purpose behind

using vacuum filtration instead of a gravity filtration is to speed up the process). This filtration

went very smoothly.

Figure 8: Vacuum filtration over a sintered funnel.

Finally, the solvent was evaporated to be left with coffee oil only. This step was performed by

distillation at 70°C, either at atmospheric pressure or -better- under vacuum. During this step the

hexane collected was recycled (Figure 9).

20

Figure 9: Distillation under vacuum.

The amount of oil collected was 40.50g which corresponds to an extraction yield of 13.50%. However,

the presence of residual hexane in the oil obtained was suspected (slight odor of hexane vapors in the

oil), so the distillation at 100°C was prolonged. This step reduced the yield down to 10.28%. In order to make the oil extra pure, the hexane-free oil obtained in the previous step was centrifuged

for 3min. This allowed the removal of a small, viscous and jelly-like fraction. This step reduced

the yield down to 9.48% (Table 1, entry 9). Note that a second trial on this oil extraction

procedure, done by using the setup shown in (Figure 7), afforded a yield of 10.30% (Table 1,

entry 9). The final resulting oil is a brownish liquid with a concentrated coffee smell. Ideally, this oil extraction setup should be performed by using a “Soxhlet apparatus” (Figure 10). In this apparatus, SCG would be placed in a thimble located in an extraction chamber. The flask

would be containing our solvent that will travel up the distillation arm when heated and fills the

extraction chamber that contains the SCG where the extraction happens. Once the chamber is filled,

the siphon arm will automatically evacuate the solvent along with the extracted coffee oil to the

flask. The process is then repeated infinitely. The role of the condenser here is to make sure that

the solvent vapors are driven back to the extraction chamber.15

21

Figure 10: Soxhlet apparatus typically used in a solid-liquid extraction.10

3.2.3. Biodiesel production

3.2.3.1. Conditions Throughout these experiments, transesterification is the reaction used for its multiple advantages

over any other procedure for biodiesel production. This chemical reaction is a reaction between

triglycerides, contained in this case in the oil extracted previously from SCG (collected from “La

paix”), and an alcohol which has to have a low molecular weight. Methanol (MeOH) was favored

over Ethanol (EtOH), because it is the smallest alcohol which makes it react faster with the

triglyceride than any other alcohol. Moreover, MeOH is less hygroscopic and is more affordable.

Potassium hydroxide was the first catalyst used as it dissolves much faster than sodium hydroxide.

These conditions were tested and modified until the optimized conditions could be determined.

The time and temperature of the reaction will be set to 1h and 60°C respectively. These parameters

were chosen based on the literature. [4] [5]

22

The general chemical equation of the transesterification reaction performed is shown in Figure

Figure 11: The chemical equation of the Transesterification reaction performed

3.2.3.2 Trial 1

i- Specification of reaction parameters

The experiment shown in Table 2 is performed on 12g of oil. The other reactants’ quantities are

defined based on the oil’s quantity and the appropriate equivalents:

Reactant Molecular

Weight (g/mol)

Density Equivalents Quantity n (mmol)

Oil

920(a)

- 1 12 13.04

MeOH 32.04

0.7918 18 7.52 234.72

KOH - - 8.6%w. 1.20 -

(a) Estimate based on the average molecular weight of soybean oil

Table 2: Transesterification of coffee oil with MeOH as a catalyst.

Normally, 6 mol equivalents for MeOH, should be sufficient but as a precaution to prevent a quick

jellification of glycerin, a larger amount of MeOH 18 mol equivalent was used in order to keep the

glycerin diluted.

Calculations are as follows:

The quantity of MeOH (i.e. 18 mol equivalents):

MeOH

oil

oilMeOHoilMeOHMeOHMeOH M

M

mMnMnm )18()18(

23

gmMeOH 52.704.32)18920

00.12(

The quantity of KOH:

gpurityKOH

mwm oilKOH

KOH 20.1%86

00.12%6.8

%

.%

ii- Transesterification reaction

After determining the appropriate quantities of each reactant and the catalyst, the oil was preheated

in a 100mL round-bottom flask at a temperature of 60°C in order to reduce its viscosity and

improve its miscibility with the methoxide solution (Figure 11).

The methoxide solution was prepared by mixing the assigned amounts of methanol and potassium

hydroxide in a vial fitted with a stir bar. The vial was then placed in a bain-marie at 40°C over a

stirring hot plate to promote and accelerate the solubility of KOH in methanol.

The methoxide solution was then added to the oil and the reaction mixture was heated at 60°C for

an hour under vigorous stirring.

Figure 12: Oil preheating step.

24

Finally, the reaction mixture was transferred to a separatory funnel in order separate the layers of

biodiesel and glycerin (Figure 12). Unfortunately, the first trial to make biodiesel was unsuccessful

as no layer separation between biodiesel and glycerin occured.

Figure 13: Reaction mixture in the separatory funnel (see foreground). An attempt to improve the result was made by adding 40mL of a 1% H3PO4 solution in order to

neutralize potential soaps and the basic catalyst that would have been causing the absence of layers.

However, the absence of layer separation persisted. Consequently, investigating the reason why

biodiesel production may have failed was necessary. The potential causes that lead to the failure of the

reaction may be a high percentage of FFAs and/or the presence of water in the potassium methoxide

solution. Appropriate experiments were conducted in order to verify these hypothesizes.

c- FFA content in coffee oil

In order to determine if the presence of FFAs in the coffee oil is playing a role in soaps formation

during the biodiesel production reaction, a titration of a sample of the oil was performed to calculate

the FFA content.

25

Trial 1:

In a 250mL Erlenmeyer flask, 1.01g of oil is mixed along with 50.00mL of EtOH (ethanol here is

used as a mean to get KOH and the oil miscible). Several drops of phenolphthalein which serves

as an indicator in acid-base titration are then added. The flask was placed in a hot bath at 38°C

under vigorous stirring in order to mix perfectly ethanol and oil.

Then, a 0.0810 M KOH solution in ethanol was placed in a 50mL burette. The burette is then

opened gently in order to add the KOH solution into the flask drop wise. As soon as a pink

coloration of the solution is noticeable (which indicates the complete neutralization of the acid),

the burette is closed and the amount added of KOH solution is recorded: V1=1.58mL.

The amount of KOH solution needed to react with the acid in the oil sample is equivalent to the

amount of FFAs.

Blank Trial:

In this trial, the same procedure is repeated but with no oil. Its purpose is to get the amount of KOH that may have reacted with ethanol instead of FFA’s. The amount recorded was: V0 =0.30mL.

%01.299.101.1

1.56)30.059.1(0810.0

99.1

)(% 11

oil

KOHKOH

m

MVVCFFA

Therefore, the FFA percentage is 2.01% which is not a very important percentage and therefore

can be neglected. Consequently, the failure of the first biodiesel production attempt cannot be

linked to the presence of FFAs in the coffee oil.

d- The presence of water in potassium methoxide solution:

The products of the reaction between KOH and MeOH contains water. The equation of the reaction

is as follows: )(2)(3)()(3 linMeOHsl OHKOCHKOHOHCH

Where potassium methoxide (− +) is the active catalyst of the reaction as it interacts with the

triglycerides. However, water, could be responsible for the formation of FFAs and soaps during

the reaction.

26

Therefore, in order to check this hypothesis, a second trial is performed to produce biodiesel. The

transesterification experiment is then performed once again, but this time, instead of using

KOH/MeOH, a commercial sodium methoxide solution was used. This solution was prepared by

its manufacturer according to the following equation:

)(2)(3)()(3 2/1ginMeOHsl HNaOCHNaOHCH

The advantages of using this type of catalyst are the facts that it is totally water-free and that it is

completely soluble in methanol.

3.2.3.3 Trial 2

i- Specification of reaction parameters

The transesterification reaction was performed on 6.00g of oil. Table 3 indicates the quantities

used.

Reactant Molecular

Weight (g/mol)

Density Equivalents Quantity n (mmol)

Oil

920(a)

- 1 6 6.52

MeOH 32.04

0.7918 30 6.26 195.65

KOH - - 2.5%w. 0.50 -

(a) Estimate based on the average molecular weight of soybean oil

Table 3: Transesterification of coffee oil with NaOMe as a catalyst. Again, normally 6 equivalents is enough for MeOH, but as a precaution to prevent a quick

jellification of glycerin, and based on the previous attempts made, 30 equivalents were used as an

additional excess of MeOH was proven to be necessary to keep the glycerin more diluted. Calculations are as follows:

Amount of NaOMe:

gmwm oilNaOMeNaOMe 15.000.6%50.2.%

27

28

But since we are using NaOMe with a concentration of 30%w.

ggmNaOMe 50.0%3015.0 Amount of MeOH:

MeOH

oil

oilMeOHoilMeOHMeOHMeOH M

M

mMnMnm )30()30(

g26.6041.32)30920

00.6(

ii- Transesterification reaction

After the specification of the exact amounts of reactants to be used, the 6.00g of oil were then

preheated at a temperature of 60°C in order to reduce its viscosity. Then, in a vial the sodium

methoxide solution was prepared by mixing 6.26g of MeOH and 0.50g of NaOMe. Note that here

neither stirring nor heating is necessary as sodium methoxide and methanol mix instantly.

The sodium methoxide solution is then added to the oil and the reaction mixture is heated at 60°C

for an hour under vigorous stirring.

Finally, the reaction mixture is transferred to a separatory funnel to separate the layers of biodiesel

and glycerin. An extra portion of methanol was poured in the funnel to prevent a quick jellification

of the mixture caused by glycerin. As no layer separation occurred, 25mL of hot water was added

to the mixture. This was done in order to induce the layer separation as glycerin is water soluble

while biodiesel is not. This technique was successful as the separation of layers (alkyl esters from

glycerol) occurred afterwards (Figure 13).

29

Figure 14: Separation of layers of biodiesel and glycerin.

The hypothesis has been checked. The presence of water has a detrimental role. Therefore, the use

of sodium methoxide ensures better results than the KOH/MeOH solution by avoiding the soaps’

formation of soaps and FFAs.

Unfortunately, since the amount of the crude biodiesel produced was very small the experiment

could not be carried on. The right conditions for producing biodiesel being now determined. The amounts of reactants can be

scaled up in order to produce a larger amount of biodiesel. This way the possibility of running a

characterization and quality test on the biodiesel produced is possible.

3.2.3.4 Optimized biodiesel production from sodium methoxide as a catalyst After performing two trials to produce biodiesel, the initial conditions initially set were modified.

As sodium methoxide proved to be a more effective catalyst that ensures a good phase separation.

The experiment described in Table 4 used the optimized conditions using 28.11g of coffee oil.

Biodiesel

Glycerin

30

i- Specification of reaction parameters

Reactant Molecular

Weight (g/mol)

Density Equivalents Quantity n (mmol)

Oil

920(a)

- 1 28.11 30.55

MeOH 32.04

0.7918 30 29.36 916.50

NaOMe

(30%w.) - - 2.5%w. 2.34 -

(a) Estimate based on the average molecular weight of soybean oil

Table 4: Scale-up of transesterification of coffee oil with NaOMe as a catalyst.

Calculations are as follows: Amount of NaOMe:

gmwm oilNaOMeNaOMe 70.011.28%50.2.%

But since we are using NaOMe with a concentration of 30%w.

ggmNaOMe 34.2%3015.0

Amount used of MeOH:

MeOH

oil

oilMeOHoilMeOHMeOHMeOH M

M

mMnMnm )30()30(

g36.29041.32)30920

00.28(

ii- Transesterification procedure

Right after determining the quantities of reactant, flask containing the oilis placed in an oil bath at

a temperature of 60°C in order to decrease its viscosity and promote afterwards the mixing of

methanol and oil layers. In parallel, the sodium methoxide solution is prepared by mixing 29.34g

of sodium methoxide with 2.33g of methanol in a large test tube. The sodium methoxide solution

is then added to the oil. Then the reaction mixture is heated for an hour at a temperature of 60°C

under continuous vigorous stirring.

31

iii- Layer separation phase

The flask content is transferred to a separatory funnel. After waiting for 15min without observing

any layer separation, 25mL of hot water was added to the mixture. This was done in order to induce

the layer separation. The layer separation finally occurred. The biodiesel layer was separated from

the glycerin and placed in a clean separatory funnel. Then 25mL of 10% phosphoric acid solution

was added to it in order to neutralize the basic catalyst. The washed biodiesel layer is then pipetted

out and transferred into test tubes to be centrifuged. After extracting the test tubes from the

centrifuge, three layers could be observed (Figure 14).

Figure 15: Layer separation of biodiesel, aqueous mixture and soaps.

The washed biodiesel fractions were collected and placed in a beaker, and the amount was

weighed. The quantity of crude biodiesel was 18.16g which gives a product yield of 64.60%.

After evaporating the methanol and residual water at 150°C under vacuum, and getting rid of

some residual solids by decantation. The yield decreased to 58.24%. Note that the maximum possible yield of conversion from coffee oil is 75%11 as the oil used is not

exclusively composed of triglycerides. However, the obtained product yield of 58.24% could

definitely be subject to improvement. Better optimization of the conditions for biodiesel

production including the washing techniques would lead to better results. Unfortunately, due to

time constraints, optimization of conditions were not possible.

32

3.2.4 Characterization and Quality test on Biodiesel As stated before, other purification steps are still necessary after the transesterification. However,

several preliminary tests were performed in order to have an idea about the characterization and

quality of the biodiesel produced.

The following are some tests that will be performed on the produced “Biodiesel”:

Thin layer chromatography

Heat content determination

Density determination The European (EN14214) and American (ASTM D6751) international standards (Appendix)

provide the possible tests to reveal the quality of the produced biodiesel. Unfortunately, only

the density test was performed due to lack of resources.

3.2.4.1 Thin layer chromatography test

The TLC test, which stands for Thin Layer Chromatography, is performed in order to test

qualitatively the purity of the biodiesel produced, or in other words to have an idea on how many

compounds are present in our product. This technique is used to separate compounds by using in the present case a plastic plate coated

with silica. A small amount of the substance to be tested is spotted at the bottom of the plate which

is then placed in a jar containing a solvent mixture. Only the bottom of the plate is put in contact

with the solvent which will rise up through the plate by capillary action. As the solvent reaches the

spot, each component will have its own solubility degree and will then move at different speeds

thus creating the separation desired.

Once the solvent reaches the top of the plate, this latter is removed, soaked in water then placed in

a staining bath and once again rinsed with water. The compounds’ separation is then visualized. Two spots of coffee oil and two spots of biodiesel are placed at the bottom of the plate (using a

capillary tube) in order to check whether impurities present in biodiesel are actually originating

from the oil used. The bottom of the plate is then placed in a solvent mixture of ethyl acetate/hexane

with a ratio of 15%/85%v. 29mL of solvent are used, i.e. 25mL of hexane and 4mL of ethyl acetate

(Figure 15). These specific conditions were inspired from a literature report.12

33

Figure 16: TLC test in progress.

Once the solvent reaches the top of the plate the latter is taken out, left to dry and then washed with

water and placed in a 1% KMnO4 solution as the staining bath, and is once again washed with

water. The separation of compounds was immediately visualized as seen in Figure 17.

The retention factor, Rf, is calculated by dividing the distance between the solvent front and the

origin over the distance that the center of each spot has traveled.

Figure 17: Compounds separation using TLC plate

After analyzing the obtained result, the biodiesel and triglycerides spots could easily be identified.

34

Also the existence of mono-glycerides, diglycerides and FFAs in the coffee oil, was revealed.

Consequently, the same compounds are present in the biodiesel, though not at the same

concentration.

An attempt to purify the coffee oil was made by using the same TLC test procedure, only this time

with a different acetate/hexane ratio. The ratio used was 5%/95%v. The high percentage of hexane

used is explained by the fact that triglycerides are more soluble in hexane compared to the other

impurities (MG, DG, FFA, caffeine…). And the goal of this experiment is to separate triglycerides

from the impurities. However, the plate obtained was exactly the same as the one obtained

previously. Which means that this technique wouldn’t be suitable for oil purification.

3.2.4.2 Calorimetry

The heat content ΔHcomb is an important parameter when characterizing any fuel. The oxygen bomb

calorimeter allows the measurement of the heat combustion for a specific reaction.

When a fuel undergoes combustion, the equation corresponding to the reaction is:

)( 222 OHCOOFuel

Therefore, a bomb calorimetry experiment is performed in order to determine the heat of

combustion of the produced biodiesel and then compare it to that of conventional diesel.

The following is the equation to be used for the calculation of heat of combustion of the appropriate

compound:

sample

cal

m

TC combH

Where: combH is the heat of combustion in kJ/g

calC is the heat capacity of the calorimeter in kJ/°C

T is the change of temperature in °C

samplem is the mass of the sample in g

i- Principle of oxygen bomb calorimeter

35

The oxygen bomb calorimeter (Figure 18), is a very well insulated container which prevents the

heat exchange between its interior and the environment. Simply said, the reactants are enclosed

inside the calorimeter, then the combustion reaction is launched, and the resulting rise in

temperature is measured. That temperature difference is the value that enables to calculate the heat

released during the reaction.14

Figure 18: Oxygen bomb calorimeter utilized in the determination of.9

The oxygen bomb (Figure 19) in its turn is where exactly the reactants are enclosed. This latter is

an explosive-proof steel container that can withstand high pressure changes while the reaction is

being measured. The bomb is usually placed in a bucket filled with water that is placed inside the

calorimeter. The heat released during the reaction is then propagated in the bomb calorimeter then

to the water which is in contact with a very sensitive thermometer that gives precise readings of

the instant change of temperature.14

36

Figure 19: Oxygen bomb16.

ii-Calorimetry experiment

The purpose of this experiment is to determine the heat of combustion of the produced biodiesel

and compare it to the conventional diesel.

As stated before the equation that used is the following:

sample

cal

m

TC combH

The first consists in determining the heat capacity of the calorimeter ( calC ). To do so, a reactant

for which we already know precisely the heat of combustion ( combH ) is used. High purity benzoic

acid is the compound that is usually used for this purpose. It-s combH is known to have a value of

-26.453 kJ/g. A pellet of 1g of benzoic acid is then used as the reactant of the reaction launched

inside the bomb calorimeter.

First, a nickel ignition wire is placed through two holes designated in two rods linked to the sample

holder. The two rods will be later connected to the electrical terminals of a 19V voltage source

which will cause a short circuit when turned on. The purpose of creating this short circuit is to heat

the wire, which will in turn ignite the fuel.

The pellet of benzoic acid weighs exactly 1.01g. This latter is placed in the sample pan shown in

Figure 20. The seal of the bomb which contains the sample of benzoic acid is then placed into the

sample pan and the bomb is then closed tightly (Figure 20).

Figure 20: Schematic of the oxygen bomb.11

37

The oxygen bomb is then filled with 99% medical grade oxygen as the second reactant. The oxygen

cylinder’s tubing is linked to the oxygen inlet of the bomb and is then filled (Figure 21).

Figure 21: Oxygen bomb connected to the oxygen cylinder.

The bucket of the calorimeter is filled with 2000mL of distilled water and the bomb is then placed

gently in the bucket by using specified tongs. The +/- terminals are then connected to the ignition

wires. The calorimeter seal, which embeds a mechanical stirrer for the purpose of making the

temperature of the water homogeneous, is then placed to close the calorimeter. The probe of a

digital thermometer with a precision of 0.1°C is then fitted (Figure 22).

38

Figure 22: Schematic of the oxygen bomb calorimeter.11

The temperature is recorded before and after the launch of the reaction. Once the temperature is

stable, the reaction is started. The reaction is launched at time t = 8min.

The data collected is presented in Graph 3.

Graph 3: Heating curve of benzoic acid.

Now that the temperature change during the reaction is calculated, we can then calculate the heat

capacity of the calorimeter is calculated as follows:

C

kJ

T

mHC benzbenz

cal

54.9

)00.158.17(

01.1)453.2(

The heat capacity of the being now known, determination of the heat contents of diesel and

biodiesel samples can be done.

Heat content of diesel:

The same experiment, under the same conditions, was performed by using a sample of diesel. The

sample used was weighed (1.00g). The temperature was then recorded and the data collected i is

shown in Graph 4.

39

Graph 4: Heating curve of diesel.

The heat of combustion can be now calculated directly:

01.1

)2.188.24(54.9

sample

calcomb

m

TCH

)/(34.62 gkJHcomb

40

Heat content of biodiesel:

To determine the heat content of the produced biodiesel, the same experiment, under the same

conditions, was be performed by using a sample of biodiesel. Again, the sample to be used was

weighed (1.01g). The temperature was then recorded and the data collected in for biodiesel

calorimetry is shown in Graph 5.

Graph 5: Heating curve of the combustion of diesel.

The heat of combustion can be now calculated directly:

00.1

)2.2200.26(54.9

sample

calcomb

m

TCH

)/(25.36 gkJHcomb

Table 5 compares the heat contents of biodiesel and diesel.

Fuel combH

Diesel 62.34

Biodiesel 36.25

Table 5: Heat content of diesel and biodiesel.

According to literature, the heat content of biodiesel is expected to be lower than the one of

biodiesel by approximately 10%.17

However, in this case it is measured to be lower by about 42%.

This anomaly can only be explained by a faulty thermometer probe.

41

3.2.4.3 Density

The density of the produced biodiesel was determined to check if it is compliant with the European

specifications. It was calculated by using the following equation ρ V

m . 10.00mL of biodiesel

were weighed using a balance with a readability of 0.0001g. The weighed mass was 8.9176g. So,

the density was ρ 33 /8.891/89176.0

00.10

9176.8mkgcmg

V

m . When compared to the

European specifications (EN14214) (Appendix) the density obtained fits in the specified range.

Sample Density (kg/m3)

Coffee oil 841.20

Biodiesel 831.80

Diesel 845.20

Table 6: Densities of coffee oil, biodiesel and diesel.

42

Conclusion

Biodiesel is a viable and promising solution to the environmental pollution which results from

conventional fuels’ combustion and to the increasing world energy demand. The use of SCG as

one of the various feedstocks for biodiesel production can be considered as a solution to these

problems. Biodiesel production and commercialization have been already successfully introduced

in many countries where USA, Brazil and Germany are the leaders.13 Throughout this work I proved the feasibility of biodiesel production by using SCG as a starting

material. I was able to identify the optimized conditions for oil extraction from SCG. The results

show that SCG should be dried as quickly and gently as possible prior to their use. The extraction

time should be set to 30 mins at a temperature of 70°C, and the solvent to should be hexane. Finally,

the sonication step was proven to be effective as it affords a better yield. For the transesterification

reaction, the use of sodium methoxide ensures better results than KOH/MeOH solution. The obtained yield of biodiesel production is 58.24%. And the highest yield of oil extraction from

unused coffee is 14.8%. Hence, by extrapolating, a minimum of 51 L/month of biodiesel could be

generated locally, this quantity provides enough energy to power an AUI van (fuel economy: 12.1L

diesel/100km) to have a return trip from the campus to Rabat (418km). By extension, 1.7

million/year of biodiesel could be generated nationally and 0.54 billion L/year could be generated

worldwide.

43

References

1 http://www.afdc.energy.gov/vehicles/diesels_emissions.html

2 A.C. Ahmia, et al, Raw material for biodiesel production. Valorization of used edible oil,

Revue des Energies Renouvelables, Vol. 17, No. 2, 2014, 335-343.

3 D. Bajpai, et al, Biodiesel: Source, Production, Composition, Properties and Its Benefits,

Journal of Oleo Science, Vol. 55, No. 10, 2006, 487-502.

4 Amish P. Vyas. et al, Effects of Molar Ratio, Alkali Catalyst Concentration and Temperature

on Transesterification of Jatropha Oil with Methanol under Ultrasonic Irradiation,

Chemical Engineering Department, Nirma University, 2011.

5 D. Darnoko, et al, Kinetics of palm oil transesterification in a batch reactor, Journal of

the American Oil Chemists' Society, 2000, Vol. 77, No. 12, 2000, 1263-1264.

6 Consommation du café dans les pays non membres de l’Organisation internationale du Café.

(2009, March 11)

7 Caetano, et al, "Valorization of Coffee Grounds for Biodiesel Production"

8 http://www.africanews.com/2015/12/23/morocco-to-host-cop-22/

9 The Soxhlet Extractor explained. (http://www.campbell.edu/faculty/jung/soxhlet.ppt)

10 http://glossary.periodni.com/glossary.php?en=Soxhlet+extractor

11 http://www.scielo.br/img/revistas/bjpp/v18n1/a14tab01.gif

12 Nívea De Lima Da Silva, et al, Investigation of Biofuels Properties, State University

of Campinas.

13 The world's biggest biodiesel producers in 2014, by country (in billion liters), 2014.

14 http://www.science.uwaterloo.ca/~cchieh/cact/c120/calorimetry.html

15 http://chemlab.truman.edu/

16 http://www.parrinst.com/products/oxygen-bomb-calorimeters/6200-isoperibol-calorimeter/

17 http://www.dartmouth.edu/~pchem/75/Bomb.html

44

Appendix

EN14214 quality standards for biodiesel

Parameter Method Limits Units

Ester content DIN EN 14103 ≥ 96.5 % w.

Density at 15°C DIN EN ISO 12185 860-900 kg/m3

Viscosity at 40°C DIN EN ISO 3104 3.5-5.0 mm2/s

Flash point DIN EN ISO 3679 ≥ 120 °C

Cold Filter Plugging Point DIN EN 116 - °C

Sulfur DIN EN ISO 20884 ≤ 10 ppm

Organic matter (10%) DIN EN ISO 10370 ≤ 0.3 % w.

Octane IP 498 ≥ 51.0 -

Sulfur ash ISO 3987 ≤ 0.02 % w.

Water DIN EN ISO 12937 ≤ 500 ppm

Total contamination DIN EN 12662 ≤ 24 ppm

Copper corrosion DIN EN ISO 2160 no 1 grad corrosion

Oxidation stability (110 °C) DIN EN 14112 ≥ 6 hours

Acid number DIN EN 14104 ≤ 0.5 mg KOH/g

Iodine number DIN EN 14111 ≤ 120 g iodine / 100 g

Linolenic acid methyl ester DIN EN 14103 ≤ 12.0 % w.

Methanol DIN EN 14110 ≤ 0.20 % w.

Free glycerol ≤ 0.020 % w.

Mono – glycerides ≤ 0.80 % w.

Di – glycerides DIN EN 14105 ≤ 0.20 % w.

Triglycerides ≤ 0.20 % w.

Total glycerol ≤ 0.25 % w.

Phosphorus DIN EN 14107 ≤ 10.0 ppm

Metals I (Na + K) ≤ 5.0 ppm

Metals II (Ca + Mg) DIN EN 14538 ≤ 5.0 ppm

45

ASTM D6751 quality standards for biodiesel

Parameter Method Limits Units

Flash point, closed cup ASTM D93 ≥ 93 °C

Water and sediment ASTM D2709 ≤ 0.05 % v.

Kinematic viscosity at 40°C ASTM D445 1.9 - 6.0 mm2/s

Sulfated ash ASTM D874 ≤ 0.02 % w.

Sulfur ASTM D5453 S15 grade : ≤ 0.0015 % w.

S500 grade : ≤ 0.0500

Copper strip corrosion ASTM D130 no 3 max -

Alcohol content

(one of the following must be met)

Methanol Content EN 14110 ≤ 0.20 % v.

Flash Point, Closed Cup D93 ≥ 130 °C

Cetane number ASTM D613 ≥ 47 -

Cloud Point ASTM D2500 -a °C

Carbon residue ASTM D4530 ≤ 0.05 % w.

Acid number ASTM D664 ≤ 0.50 mg KOH/g

Free glycerin ASTM D6584 0.02 % w.

Total glycerin ASTM D6584 0.24 % w.

Phosphorus ASTM D4951 ≤ 10 ppm

Vacuum distillation end point ASTM D1160 360 °C

Oxidation stability EN 14112 ≥ 3 hours

Calcium & Magnesium (combined) EN 14538 ≤ 5 ppm (a) Must be reported to customer