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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
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iii
iv
V
vii
xii
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xv
xvi
I
4
5
6
7
8
9
10
12
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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
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