AGRICULTURAL WASTE TO FUEL USING MICROWAVE PYROLYSIS

Sharifah Mona Binti Abd Aziz Abdullah

Master of Science 2012

Pusat Khidmat Makiumat Akadea,.. UNIVERSTIT MALAYSIA SARAWAK

AGRICULTURAL WASTE TO FUEL USING MICROWAVE PYROLYSIS

SHARIFAH MONA BINTI ABD AZIZ ABDULLAH

L or

A thesis submitted In fulfillment of the requirements for the degree of Master of Science

(Environmental Chemistry)

L

Faculty of Resource Science and Technology UNIVERSITI MALAYSIA SARAWAK

2012

DECLARATION

I hereby declare that no portion of the work referred to this thesis has been submitted

in support of an application for another degree or qualification to this or any other

university or institution of higher learning.

(SHARIFAH MONA BINTI ABD AZIZ ABDULLAH)

Date:

ii

ACKNOWLEDGEMENT

I thank Allah the Most Merciful Most Gracious for His Guidance and kept me

in His Grace and far from astray, I am finally able to complete this thesis.

It is difficult to overstate my gratitude to my supervisor, Mdm Rafeah Wahi.

With her enthusiasm, inspiration, and her great efforts to explain things clearly and

simply, she helped to make my research work meaningful for me. Throughout my

thesis-writing period, she provided encouragement, sound advice, good teaching,

good company, and lots of good ideas. I would have been lost without her.

I owe a special debt of gratitude to both of my co-supervisor, Prof Dr Sinin

Harridan and Assoc Prof Dr Zainab Ngaini for their kind assistance with giving wise

advice, helping with various applications, and so on.

Special appreciation goes to the faculty members especially Hj Karni, Mr

Wahap and Mr Rajuna Tahir, for their endless assistance throughout my years in

UNIMAS.

I would like to acknowledge the support of research grant from Mdm Rafeah

Wahi (FRGS/02(04)/652/2007(17) by Universiti Malaysia Sarawak (UNIMAS) and

special thanks to Zamalah UNIMAS for the financial assistance

Most importantly, I wish to thank my parents, Abd Aziz Abdullah and Indon

binti Apong for their patience. They raised me, supported me, taught me, and loved

me.

Last but not least, my precious friends. Thank you for your endless love, joy

and care that you have brought into my life. My love will always be with you guys.

Thanks to Mohammad Nasaruddin bin Anis, Norizan Sebri, Anastasia Shera, Pang

Sing Tyan, Lau See Hung and Uma Devi Krishnan.

III

ABSTRACT

:; Agricultural wastes such as palm kernel (PK) shell, wood chip (WC) and sago waste

(SW) have a potential as alternative energy resources. These wastes produce abundant

volatile matter which can be converted to fuel through suitable treatment such as

microwave pyrolysis. A domestic microwave oven of 1000 W and 2450 MHz

frequency was modified to pyrolyzed PK, WC and SW at laboratory scale. PK, WC

and SW showed a maximum pyrolysis temperature at 289 °C, 280 °C (both after 5

min) and 390 °C (after 4 min) respectivel . Finding shows that the yield of bio-oils

was ranged from 9-15 wt%, 6-14 wt% and 3-16 wt% for PK, WC and SW

respectively. As for bio-char, the yield obtained was at 41-68 wt% (PK), 43-57 wt%

(WC) and 14-53 wt% (SW). The highest calorific value recorded for bio-oils are

27.19,25.99 and 21.99 MJ/kg for PK bio-oil (PKO), WC bio-oil (WCO) and SW bio-

oil (SWO) respectively. The GC-MS results indicated that PKO, WCO and SWO

were dominated by mixture of oxygenated hydrocarbon compound. A great range of

functional groups of alcohols, ketones, aldehydes and carboxylic acids were indicated

in IR spectrum. The bio-char obtained from PK, WC and SW has relatively high

calorific value of 29.04,24.89 and 25.99 MJ/kg respectively which is in the range

with lignite and sub-bituminous coal (24-30 MJ/kg). Esterification of PKO with

ethanol in the presence of sulphuric acid (as catalyst) has enhanced the quality of the

bio-oil. The process has successfully improved the odour of the bio-oil to a

presentable smell. The pH value increased from 3.37 to 5.09-5.12 and the calorific

value increased from 27.19 to 34.78-41.52 MJ/kg.

iv

SISA PERTANIAN KEPADA BAHAN BAKAR MENGGUNAKAN PIROLISIS

GELOMBANG MIKRO

ABSTRAK

Sisa pertanian seperti tempurung kelapa sawit (TKS), sisa kayu (SK) dan sisa sagu

(SS) mempunyai potensi sebagai sumber tenaga alternatif. Sisa-sisa ini mempunyai

kandungan bahan meruap yang tinggi dan boleh ditukarkan kepada bahan bakar

dengan menggunakan pirolisis gelombang mikro. Ketuhar gelombang mikro domestik

berkuasa 1000 W dan berfrekuensi 2450 MHz telah diubahsuai untuk pirolisis TKS,

SK dan SS pada skala makmal. TKS, SK dan SS masing-masing mencapai suhu

pirolisis maksimum pada 289 °C, 280 °C (kedua-duanya selepas 5 min) dan 390 °C

(selepas 4 min). Keputusan eksperimen menunjukkan hasil bio-oil adalah di antara

9-15 %, 6-14 % dan 3-16 % masing-masing bagi TKS, SK dan SS. Manakala untuk

bio-char, hasil yang diperolehi adalah di antara 41-68 % (TKS), 43-57 % (SK) dan

14-53 % (SS). Nilai kaloriftk bio-oil tertinggi adalah sebanyak 27.19,25.99 dan 21.99

MJ/kg masing-masing bagi TKS, SK dan SS. Data GC-MS menunjukkan bio-oil

daripada TKS. SK dan SS didominasi oleh campuran sebatian hidrokarbon

beroksigen. 1R spektrum menunjukkan julat kumpulan berfungsi bio-oil terdiri

daripada alkohol, keton, aldehid dan asid karboksilik. Bio-char yang dihasilkan

daripada TKS, SK dan SS mempunyai nilai kalorifik yang tinggi iaitu masing-masing

29.04,24.89 dan 25.99 MJ/kg. Nilai-nilai ini adalah dalam julat nilai kalorifik lignit

dan arang bate sub-bitumin (24-30 MJ/kg), Pengesteran bio-oil TKS menggunakan

etanol dan asid sulfurik (sebagai pemangkin) telah mampu menambah baik kualiti

bio-oil. Proses ini didapati mampu mengubah bau bio-oil asal kepada bau yang lebih

V

disenangi. Nilai pH bio-oil rneningkat daripada 3.37 kepada 5.09-5.12 dan nilai

kalorifik juga meningkat daripada 27.19 kepada 34.78-41.52 MJ/kg.

vi

Pusat Khidmat Maklumat Akademib Ur1IVERSTTt MALAYSIA SARAWAK

TABLE OF CONTENTS

DECLARATION

ACKNOWLEDGEMENT

ABSTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF ABBREVIATIONS

LIST OF SYMBOLS

CHAPTER 1

INTRODUCTION

1.1 Research background

1.2 Statement of problem

1.3 Justification of study

1.4 Research objectives

1.5 Scope of study

CHAPTER 2

LITERATURE REVIEW

2.1 Biomass

2.2 Biomass components

2.3 Properties of biomass

2.4 Agricultural wastes

Page

ll

iii

iv

V

vii

xii

X111

xv

xvi

I

4

5

6

7

8

9

10

12

vii

2.5 Agricultural waste reutilization 13

2.5.1 Biochemical conversion 13

2.5.2 Thermochemical conversion 14

2.6 Pyrolysis 15

2.6.1 Classification of pyrolysis by heating rate 16

2.6.2 Classification of pyrolysis by heating method 17

2.7 Microwave heating 19

2.8 Microwave pyrolysis of agricultural wastes 21

2.9 Pyrolysis products 23

2.9.1 Pyrolytic oil (bio-oil) 23

2.9.1.1 Characteristics of bio-oil 24

2.9.1.2 Composition of bio-oil 26

2.9.2 Pyrolytic char (bio-char) 28

2.9.3 Pyrolytic gas 31

2.10 Upgrading of bio-oil 33

CHAPTER3

MATERIALS AND METHODS

3.1 Agricultural waste samples 36

3.2 Characterization of the agricultural wastes 39

3.2.1 Proximate analysis 39

3.2.2 Ultimate analysis 41

3.2.3 Calorific value analysis 41

3.2.4 Thermogravimetric analysis (TGA) 42

3.2.5 Fourier Transform Infrared Spectroscopy (FTIR) 42

Vlll

3.3 Microwave pyrolysis experiments 43

3.3.1 Modification of the household microwave oven 43

3.3.2 Experimental setup

3.3.3 Experimental procedure

3.3.4 Temperature measurement

3.4 Product yield

3.4.1 Bio-oil yield

3.4.2 Bio-char yield

3.4.3 Gases yield

3.5 Analysis of pyrolysis product

43

44

45

46

46

46

47

47

3.5.1 Bio-oil analysis 47

3.5.2 Bio-char analysis

3.6 Esterification of bio-oil

3.6.1 Analysis of esterified bio-oil (EO)

CHAPTER 4

48

48

49

MICROWAVE PYROLYSIS OF AGRICULTURAL WASTES: OPERATING CONDITIONS AND PRODUCT YIELDS

4.1 Results and discussion

4.1.1 Raw materials characteristics

4.1.2 Microwave pyrolysis experiment

4.1.3 Product yield

4.2 Conclusion

51

51

55

59

62

ix

CHAPTER 5

BIO-OILS FROM MICROWAVE PYROLYSIS OF AGRICULTURAL WASTES

5.1 Results and discussion 63

5.1.1 Calorific value 63

5.1.2 pH value 65

5.1.3 Infrared (IR) spectra 66

5.1.4 Gas Chromatography Mass Spectrometry (GC-MS) 70

5.2 Conclusion 80

CHAPTER 6

BIO-CHARS FROM MICROWAVE PYROLYSIS OF AGRICULTURAL WASTES

6.1 Results and discussion 82

6.1.1 Proximate analysis

6.1.2 Ultimate analysis

6.1.3 Calorific value

6.1.4 Infrared (IR) spectra

6.1.5 Scanning Electron Microscope (SEM)

82

85

86

88

91

6.2 Conclusion 93

CHAPTER 7

ESTERIFICATION OF BIO-OIL FROM MICROWAVE PYROLYSIS

7.1 Results and discussion 95

7.1.1 Esterification of bio-oil 95

X

7.1.2 Physical properties of esterified bio-oil (EO) 100

7.2 Conclusion 102

CHAPTER 8

GENERAL CONCLUSION AND RECOMMENDATION

8.1 Conclusion 103

8.2 Recommendations 105

REFERENCES

APPENDIX A

APPENDIX B

APPENDIX C

APPENDIX D

106

114

118

129

135

XI

LIST OF TABLES

Page

Table 2.1 The main operating parameters for pyrolysis 16 processes

Table 2.2 The properties and characteristics of wood bio-oil 24

Table 3.1 Parameter for esterification 49

Table 4.1 Chemical characteristics of agricultural wastes 51 samples

Table 4.2 Maximum temperature (Tmax), heating time and 57 heating rate (R) of PK, WC and SW in inert atmosphere

Table 4.3 Yield of microwave pyrolysis products (without 5 60 wt% char)

Table 5.1 Calorific value of PKO, WCO and SWO at different 63 heating time

Table 5.2 pH value of PKO, WCO and SWO at different 65 heating time

Table 5.3 The main functional groups of PKO, WCO and SWO 66 determined by the FTIR analysis

Table 5.4 Chemical composition of PKO 75

Table 5.5 Chemical composition of WCO 77

Table 5.6 Chemical composition of SWO 79

Table 6.1 Ultimate analysis of PKC, WCC and SWC at 85 different heating time

Table 6.2 Calorific value of PKC, WCC and SWC at different 87 heating time

Table 7.1 Comparison of PKO and EO after esterification 101

xii

LIST OF FIGURES

Page

Figure 2.1 Schematic diagram of temperature distribution, heat 19 transfer and mass transfer in the conventional and microwave heating of wood

Figure 3.1 Palm kernel shell sample 36

Figure 3.2 Wood chip sample 36

Figure 3.3 Sago waste sample 36

Figure 3.4 Microwave pyrolysis of agricultural wastes for 38 conversion into fuel material

Figure 3.5 Modified household microwave oven and the quartz 44 reactor attached to the oven

Figure 3.6 Schematic diagram of the microwave pyrolysis reactor 44

Figure 4.1 TGA curves of different agricultural waste samples at 54 heating rate of 10 °C/min

Figure 4.2 Temperature evolution during microwave treatment of 56 PK, WC and SW samples

Figure 4.3 Temperature evolution of raw PK and PK mixed with 58 5 wt% char

Figure 4.4 Temperature evolution of raw WC and WC mixed with 58 5 wt% char

Figure 4.5 Yield of bio-oil obtained from current study and in the 62 literature

Figure 5.1 IR spectra of PKO at different heating time 68

Figure 5.2 IR spectra of WCO at different heating time 69

Figure 5.3 IR spectra of SWO at different heating time 70

Figure 5.4 Gas chromatograms of PKO 71

Figure 5.5 Gas chromatograms of WCO 72

Figure 5.6 Gas chromatograms of SWO 73

X111

Figure 6.1 Proximate analysis of PKC 83

Figure 6.2 Proximate analysis of WCC 83

Figure 6.3 Proximate analysis of SWC 84

Figure 6.4 IR spectra of PK and PKC at different heating time 89

Figure 6.5 IR spectra of WC and WCC at different heating time 89

Figure 6.6 IR spectra of SW and SWC at different heating time 90

Figure 6.7 Morphological structure of PKC, WCC and SWC at 92 different heating time (magnification 1000x)

Figure 7.1 Gas chromatogram of PKO 96

Figure 7.2 Gas chromatograms of EO 96

Figure 7.3 IR spectra of PKO and EO 99

xiv

LIST OF ABBREVIATIONS

PK Palm kernel shell

WC Wood chip

SW Sago waste

PKO Bio-oil of palm kernel shell

WCO Bio-oil of wood chip

SWO Bio-oil of sago waste

PKC Bio-char of palm kernel shell

WCC Bio-char of wood chip

SWC Bio-char of sago waste

FTIR Fourier Transform Infrared

GC-MS Gas Chromatography-Mass Spectrometry

W Watt

MHz Mega Hertz

HHV Higher heating value

K Kelvin

PAHs Polycyclic aromatic hydrocarbons

SEM Scanning electron microscopy

TGA Thermogravimetric analysis

T Temperature

R

EO

S. D

Heating rate

Esterified bio-oil

Retention time

Standard deviation

xv

LIST OF SYMBOLS

Tan S Loss angle

Complex permittivity

Dielectric constant

Dielectric loss

xvi

CHAPTER 1

INTRODUCTION

1.1 Research background

Research on biomass as renewable energy sources is growing importance in respond

to the great demand of energy, the depleted of fossil fuel and the environmental

concerns on green house gases and other emissions. In Malaysia, agricultural and

forestry residues are the main biomass resources which are abundantly available.

Currently, the conventional way to dispose or utilize these wastes is by combustion or

landfilling. In fact, wastes generated from the palm oil mills such as palm kernel and

palm fibre are traditionally used as solid fuels for steam boilers (Md Kawser and

Farid, 2000). However, the problems associated with the burning of these wastes are

the emissions of dark smoke and higher levels of dust emission into the atmosphere,

thus an efficient and environmental friendly alternative are required (Yusoff, 2006).

Agricultural wastes such as palm oil waste, sago waste and wood waste are rich in

volatile matter and therefore can be converted into usable energy sources when

subjected to suitable treatment. Thermochemical conversion such as pyrolysis is a

potential alternative route of biomass to produce liquid, carbon rich solid residue and

gases fuels synchronously. In pyrolysis process, agricultural wastes undergo thermal

decomposition in an oxygen-free environment (Doshi et al., 2005). The proportion of

liquid, solid and gases products formed is dependent on the operating parameters such

I

as reaction temperature, heating rate, heating time, biomass properties and the

experimental equipment employed (Bridgwater et al., 1999; Dominguez et al., 2008).

The pyrolysis products are of wide applications and economic values. The liquid (bio-

oil) has high energy density and is easy to store and transport. It can be used both as

an energy source and a raw material for chemical production (Bridgwater et al.,

1999). The carbonaceous residue (bio-char) can be burnt as fuel and with an

appropriate porous structure and surface area, it also can be upgraded to activated

carbon (Yaman, 2004). The gas (syngas) can be used in power generation or for the

production of derived liquid fuels such as methanol, dimethyl ether and synthetic

diesel (Lv et al., 2007).

In conventional pyrolysis, the system was performed using fixed bed, fluidized bed,

circulating fluidized bed and powder-particle fluidized bed, in which samples are

heated externally by using electrical heating (Yaman, 2004). Conventional heating

have certain limitations such as heat transfer resistance, heat losses to surrounding,

utilization of portion of heat supplied to biomass materials and damage to reactor

walls due to continuous electric heating (Salema and Ani, 2010). Furthermore, long

heating duration results in an undesired or secondary reaction.

The latest development in the pyrolysis study is the microwave heating method where

the microwave energy is deposited directly inside the material which creates

instantaneous heat (Huang et al., 2008). In previous studies, microwave heating has

been applied to various kind of biomass pyrolysis such as coal (Monsef-Mirzai et a!.,

1995), oil shales (El Harfi et al., 2000), plastic wastes (Ludlow-Palafox and Chase,

2001), sewage sludge (Dominguez et al., 2006; Menendez et al., 2002), wood block

2

(Miura et al., 2004), corn stover (Yu et al., 2009), coffee hulls (Dominguez et al.,

2007), rice straw (Huang et al., 2008), and pine sawdust (Wang et al., 2009).

In conventional heating the heat is transferred into the material through convection,

conduction and radiation of heat from the surface of the material. In contrast,

microwave energy is delivered directly into materials through molecular interaction

with the electromagnetic field, thus obtain a more uniform distribution of heat

compared with conventional heating (Huang et al., 2008; Yu et al., 2009). Uniform

distribution of heat results in easier temperature regulation and hence better control of

the process and the desired end products (Yu et al., 2009). In addition, microwave

heating provides volumetric heating mechanism at improved heating efficiencies

which saves energy compared to conventional techniques (Appleton et al., 2005).

Other than that, microwave pyrolysis could prevent the secondary reactions of

volatiles product, thus produced high quality of bio-oil with less polycyclic aromatic

hydrocarbons (PAHs) compared to those bio-oil obtained from electrical furnace

(Dominguez et al., 2006). Study on microwave pyrolysis of rice straw also reported

that the bio-oil product was highly alkylated, oxygenated and less hazardous PAHs

content (Huang et al., 2008). However, significant concentrations of PAHs in bio-oil

were reported when the input power of microwave increased from 300 to 900 W (Yu

et al., 2009).

Similar to other studies, the bio-oil produced has undesirable properties such as high

viscosity, poor heating value, corrosiveness and poor stability (Junming et al., 2008).

These properties will cause problems for direct use by thermal devices. Hence, bio-oil

3

requires upgrading processes in order to improve its quality before being used as a

replacement for conventional fuels. Esterification solves the problem related to

corrosivity, high viscosity, high water content, low calorific value and instability of

bio-oil (Doshi et al., 2005). It is a potential route to convert carboxylic acid in the bio-

oil into ester by reacting them with alcohol. Previous studies claimed that this method

has improved the viscosity, corrosivity, calorific value and chemical stability of bio-

oil as a fuel (Doshi et al., 2005; Zhang et al., 2006; Junming et al., 2008).

In this study, microwave heating technique has been applied for conversion of

agricultural wastes into energy sources. A modified microwave oven with input power

of 1000 W and frequency of 2540 MHz was used to perform pyrolysis of three

different types of wastes namely palm kernel shell, wood chips and sago waste. This

study examined the feasibility of microwave pyrolysis of palm kernel shell, wood

chips and sago waste to produce valuable liquid (bio-oil), solid (bio-char) and gases

fuel. The physical and chemical characteristics of bio-oil and bio-char products were

also determined to assess the potential of these products as a fuel. The upgrading of

bio-oil through esterification has been performed to convert the carboxylic acid in the

bio-oil into ester by reacting them with alcohol. The physical and chemical properties

of the esterified oil were analyzed to assess the effectiveness of esterification to

improve the quality of the bio-oil.

1.2 Statement of problem

Malaysia is a developing country with the need of sustains and stable energy supply

for its industries. The depletion of fossil fuels reserves is estimated within 40-50 years

4

Pusat Khidmat Makiumat Akademc;. UNNERSITI MALAYSIA SARAWAK

thus, lead to the exploration of alternative energy sources (Koh and Hoi, 2003).

Biomass such as agricultural wastes is the most potential renewable energy sources in

Malaysia. Agricultural (palm oil, rice, sugarcane, sago) and forestry industry (timber)

generated significant amount of wastes annually. In fact, 31.94 million tonnes of

wastes are generated from palm oil industries in 2005, as reported by Nasrin et al.

(2008). One of the most common routes for conversion of biomass into energy is

pyrolysis. Pyrolysis of biomass not only allows for higher energy recovery from the

waste but also generates a wide spectrum of products. Most published work on the

pyrolysis has dealt with conventional heating system. Salema and Ani (2010) claimed

that conventional heating have certain limitations such as heat transfer resistance, heat

losses to surrounding, utilization of portion of heat supplied to biomass materials and

damage to reactor walls due to continuous electric heating. Furthermore, long heating

duration results in an undesired or secondary reaction. Thus, microwave assisted

pyrolysis is being developed as an alternative for pyrolysis of biomass. Microwave

heating offers unique advantages such as rapid, uniform, and selective heating of

microwave radiation, and there is no direct contact between the microwave source and

the heated material, which is not attained by conventional heating (Huang et al., 2008;

Yu et al., 2009). Besides, microwave pyrolysis generates low proportions of

hazardous compounds particularly the polycyclic aromatic compounds in the bio-oil

produced (Dominguez et al., 2003; Huang et al., 2008). On the other hand, bio-oil

from conventional pyrolysis has been proven to contain high proportion of these

compounds (Dominguez et al., 2003; Dominguez et al., 2006; Menendez et al., 2002;

Menendez et al., 2004).

5

1.3 Justification of study

The present research examines a microwave pyrolysis of three types of samples

namely palm kernel shell, wood chip and sago waste using modified microwave oven

with input power of 1000 W. To date there has been only few studies on microwave

pyrolysis of palm kernel shell and wood waste was conducted and no studies on

microwave pyrolysis of sago waste particularly on the temperature profile and the

yield of pyrolysis product have been published so far. Therefore, this study can

provide information on conversion of these three types of waste into energy via

microwave pyrolysis. The yield of pyrolysis products were investigated as a function

of heating time. This study also provides information on the characteristic of bio-oil

and bio-char products as fuels. Furthermore, upgrading of bio-oil through

esterification was conducted to improve the quality of bio-oil produced.

1.4 Research objectives

The main objective of this study is to convert agricultural wastes namely palm kernel

shell (PK), wood chips (WC) and sago waste (SW) into solid and liquid fuels via

microwave pyrolysis. Specific objectives are:

i. To determine the yield of liquid (bio-oil), solid (bio-char) and gases

produced from microwave pyrolysis of PK, WC and SW at different heating

time.

ii. To conduct chemical characterization on the bio-oils and the bio-chars

produced from microwave pyrolysis and further evaluate their quality as a

fuel.

iii. To improve quality of bio-oil through esterification process.

6

1.5 Scope of study

In this study, a modified microwave oven with input power of 1000 W and frequency

of 2540 MHz was used to perform pyrolysis. The scope of study involves the

measuring of chemical characteristics for PK, WC and SW samples in order to

evaluate the potential of these samples as energy sources. This research also studied

the temperature evolution of PK, WC and SW during microwave pyrolysis. The yield

of bio-oil, bio-char and gases product from microwave pyrolysis was determined for

each of the agricultural waste samples. In this study, the bio-oils are the main interest

as it contains various chemical with specific high quality and added value application.

In terms of application, bio-oil and bio-char are easy to store and transport as

compared to gaseous fuels. Hence, this research emphasize on the characteristics of

bio-oils and bio-chars products and their potential as liquid and solid fuel. The

physical properties of the bio-oil such as pH, calorific value and density were

investigated. The chemical characteristic of bio-oil particularly on the bio-oil

compounds was analyzed using Fourier Transform Infra Red Spectroscopy (FTIR)

and Gas Chromatography Mass Spectrometry (GC-MS). The bio-char produced from

microwave pyrolysis was characterized by proximate analysis, ultimate analysis,

calorific value, FTIR analysis and Scanning Electron Microscope (SEM) analysis.

Esterification of bio-oil was conducted and the chemical and physical properties of

esterified bio-oil were compared with the original bio-oil.

7