ALKALINE PEROXIDE MECHANICAL

PULPING OF OIL PALM FRONDS VASCULAR

BUNDLE FIBRES

by

OWOLABI FOLAHAN ABDULWAHAB

TAIWO

Thesis submitted in fulfilment of the requirements

for the degree of

Doctor of Philosophy

November 2016

ii

ACKNOWLEDGEMENT

Prima facea, I am grateful to almighty Allah (SWT) for granting me good health and

well-being that were necessary to complete this study. I am glad for the opportunity to thank

the many people who have encouraged and supported me as I worked toward completion of

this dissertation.

I am grateful to my research supervisors, Dr. Arniza Ghazali, for her pragmatic

supervision and also to my co-supervisors: Prof. Dr.Wan Rosli Wan Daud and Associate Prof.

Abbas Fadhl Mubarek AlKarkhi for their valuable contributions to my Ph.D research study.

I am eternally grateful for the kindness and support of Prof. Dr. Othman Sulaiman and

the wife Prof. Rokiah Ashim both in private and official capacity. My sincere thanks also go

to Associate Prof. Dr. Leh Cheu Peng, Dr. Mazlan Ibrahim, En. Abu Mangsor Mat Sari, (Pak

Abu) for their support and encouragement, while not forgetting the beautiful pieces of advice

and guide given by my mentor Dr. Rushdan Ibrahim. May almighty Allah reward you all

accordingly and abundantly.

My appreciation also goes to Dr. Wan Noor Aidawati Wan Nadhari, Dr. Rohaizu

Roslan, Dr. Khadijah Olateju, Dr. Abdullah Abdurhman Dr. Fahmi Awwalludin and Ustaz

Ajijolakewu for their contributions in this thesis draft.

I owe my brother Surv. (Alh.) Bashir Olayinka Kadiri, Engr. (Alh.) Mohammed

Hassan Bello and Mr. Salawu a debt of gratitude for their unflagging support to my family

throughout my journey away from home. I thank my fellow lab mates for the stimulating

discussions, for the sleepless nights we were working together before deadlines, and for all

the fun we had over the years.

iii

TABLE OF CONTENT

ACKNOWLEDGEMENT ii

TABLE OF CONTENT iii

LIST OF TABLES xi

LIST OF FIGURES xiii

LIST OF ABBREVIATIONS xvii

LIST OF SYMBOLS xix

ABSTRAK xx

ABSTRACT xxii

CHAPTER 1 INTRODUCTION 1

1.1 General Background 1

1.2 Pulp and Paper Lignocellulose 2

1.3 Problem Statement 4

1.4 Research Objectives 5

1.5 Structure of Dissertation 6

CHAPTER 2 LITERATURE REVIEW 8

2.1 Current Overview of Global Pulp and Paper Industries 8

2.2 Pulp and Paper Production 16

2.3 Pulping Technique 16

2.4 Hybrid Form of Pulping: Chemi-Mechanical Pulping 20

2.5 New Techniques in Pulping 21

2.5.1 Bio-Pulping Technology: 22

iv

2.5.2 Organosolv Pulping 22

2.6 Alkaline Peroxide Mechanical Pulping (APMP) 23

2.6.1 Pre-Conditioning with Refinesr Chemical APMP (PRC-APMP) 24

2.6.2 Enzymology in APMP 26

2.7 Alkaline Peroxide Pulping (APP) 27

2.7.1 History of Alkaline Peroxide in Industrial Revolution 28

2.7.2 Chemistry of Alkaline Peroxide Pulping 29

2.7.3 System with Alkaline Peroxide Treatment of Lignocelluloses 31

2.7.4 APMP of Various Biomass 36

2.7.5 Alkaline Peroxide Treatment of Oil Palm Biomass 38

2.7.6 Production of Nanolaminates 42

2.8 Biomass 44

2.8.1 Properties of Pulp and Paper Making Fibres 45

2.8.2 Suitability of Non-Wood for Pulp and Paper 48

2.8.3 Types of Non-Wood Fibre 49

2.8.4 Agricultural Residues - Promising Alternative to Wood Fibre 50

2.8.4(a) Special Products from Agricultural Residue 52

2.8.5 Advantages of Using Agricultural Residues 52

2.8.5(a) Economic Viability 52

2.8.5(b) Environmental Challenges 53

2.8.5(c) Technological Simplicity 53

2.9 Plant Based Natural Fibres 54

2.9.1 Processing of Plant Based Natural Fibres 55

2.10 Oil Palm Biomass 57

v

2.10.1 Anatomy of OPF 59

2.10.2 Extraction of Oil Palm Biomass for Paper Making 60

2.11 Chemistry of Delignification 60

2.12 Correlation Between Bonding and Strength Properties in Paper 61

2.13 Bonding of Fibres in Paper 63

2.13.1 Inter-fibre Bonding in Paper 63

2.13.2 Van der Waal´s Interaction 64

2.13.3 Hydrogen-Bonding 65

2.14 Fibre Morphological Modification 66

2.15 Experimental Design for APMP of OPF 67

CHAPTER 3 EXPERIMENTAL METHODOLOGY

70

3.1 Introduction 70

3.2 Materials and Methods 72

3.2.1 Raw Material Preparation 72

3.2.2 List of Basic Chemicals Used in the Experiment 75

3.3 Characterisation of OPF Fibres 75

3.3.1 Morphological Analysis 76

3.3.1(a) Fibre Maceration and Measurement 76

3.3.1(b) Derived Values 77

3.3.2 Chemical Composition 77

3.4 Effect of AP on Extracted OPF Fibres 78

3.4.1 Preparation of Cooking Chemicals 78

3.4.2 AP Treatment of the OPF Vascular Bundle 78

vi

3.4.3 Refining Process 81

3.4.4 Pulp Screening 82

3.4.4(a) Preparation of Pulp Stock 83

3.4.5 Pulp Characterisation 84

3.4.5(a) Kappa Number 84

3.4.5(b) Determination of Residual Klason Lignin 86

3.4.6 Canadian Standard Freeness 86

3.4.7 Characterisation of the Extracted Cellulose 87

3.4.7(a) X-ray Diffraction Analysis 87

3.4.7(b) Fourier Transform Infrared (FT-IR) Spectroscopy 88

3.4.7(c) Thermogravimetric Analysis (TGA) 88

3.4.7(d) Scanning Electron Micrograph (SEM) 89

3.4.8 Fibre Quality Analyser (FQA) 89

3.4.9 Paper Formation 91

3.4.10 Paper Characterisation 92

3.4.10(a) Physical Properties of Handsheet 92

3.4.10(b) Handsheet Thickness 92

3.4.10(c) Grammage 93

3.4.10(d) Apparent Density 94

3.4.10(e) Optical Properties of Handsheet 94

3.4.10(f) Strength Properties of Handsheet. 94

3.4.10(g) Tensile Strength 95

3.4.10(h) Tear Resistance 96

3.4.10(i) Burst Strength 97

vii

3.4.10(j) Effect of AP Treatment and Reaction Duration 97

3.4.10(k) Scanning Electron Microscope (SEM) 98

3.4.11 Surface Modification of Handsheet 98

3.5 Study of Cooking Variables for APMP of OPF 99

3.5.1 Experimental Design 99

3.6 Regression Model Development 101

CHAPTER 4 DIMENSIONAL CHARACTERISATION OF THE OPF

VASCULAR BUNDLE FIBRES

103

4.1 Characterisation of OPF Vascular Bundle Fibres 103

4.2 Dimensional Analysis 104

4.3 Chemical Composition of OPF Vascular Bundle 109

4.4 Elemental Analysis and Microscopy 113

4.5 Conclusion 115

CHAPTER 5 EVALUATION OF AP PERCENTAGE TREATMENT

LEVEL AND REACTION DURATION ON THE

PROPERTIES OF THE RESULTANT PULP.

116

5.1 Introduction 116

5.2 Evaluation of the Pulp from AP Treatment of the OPF 117

5.2.1 Screened Pulp Yield 117

5.2.2 Kappa Number 121

5.2.3 Canadian Standard Freeness 126

5.3 Fibre Flexibility and Conformability 128

5.3.1 Effect of AP Concentrations on Pulp Fibre Fines Distribution 130

5.3.2 Effect of Cogenerated Fibre Fines 132

5.4 Morphology of Alkaline Peroxide Extracted OPF Fibres 135

viii

5.4.1 Thermal Characterisation of OPF APMP Pulp 136

5.4.2 X-Ray Diffraction 139

5.4.3 Correlation between FTIR, DTG and XRD 142

5.5 Effect of Alkaline Peroxide Concentration on Paper Apparent Density 147

5.6 Effect of AP Concentrations on the Strength Properties of OPF Paper 151

5.6.1 Strength and Apparent Density Correlation of OPF Vascular Bundle

Paper 158

5.7 Effect of AP Treatment on Inter Fibre Bonding Strength 163

5.8 Effect of AP Treatment on Optical Properties of OPF Paper 165

5.9 Surface Morphological Transformation of Paper from OPF 170

5.10 OPF VB APMP Pulp Network Enhancement 175

5.10.1 Effect of Nanocoating on Paper Printability 176

5.11 Conclusion 177

CHAPTER 6 OPTIMIZATION OF AP VARIABLES 180

6.1 Introduction 180

6.2 Statistical Output 183

6.3 Regression Model Development 187

6.4 Effect of Selected Independent Variables 193

6.4.1 Screened Pulp Yield 193

6.4.2 Kappa Number 197

6.4.3 Tensile Index 199

6.4.4 Burst Index 202

6.4.5 Tear Index. 205

6.4.6 Optical Properties 207

6.5 Elucidating the Correlative Effect of the Response Variables 212

ix

6.6 Optimization of Alkaline Peroxide Treatment 215

6.6.1 Confirmatory Experiment 217

6.7 Conclusion 219

CHAPTER 7 CONCLUSION AND RECOMMENDATION 221

7.1 Recommendation 223

REFERENCES 225

APPENDIX 267

LIST OF PUBLICATIONS

x

LIST OF TABLES

Page

Table 2.1 Annual Paper Production From Malaysian Paper Mills 15

Table 2.2 Common Pulping Method for Lignocellulosic Materials 18

Table 2.3 Active Radicals and Anions from H2O2 Decomposition

in Alkaline Medium

31

Table 2.4 Progress in the Development of AP Treatment System 33

Table 2.5 Physico-Chemical Properties of Some Non-Woods

Used For Papermaking

47

Table 2.6 Categories of Plant Based Natural Fibres 55

Table 3.1 Overview of the General Experimental Work 72

Table 3.2 List of the Chemicals Used in the Study 75

Table 3.3 RSM Experimental Design Summary for AP pulping of

OPF

99

Table 4.1

Data of Dimensional Properties from OPF Vascular

Bundle

104

Table 4.2 Comparison of Morphological Properties of Selected

Lignocellulosic Biomass

106

Table 4.3 Chemical Compositions of OPF VB and Selected

Lignocellulosices Biomass

110

Table 5.1 ANOVA for AP Level and Reaction Duration Effect on

the Properties of OPF VB Fibres Network

118

Table 5.2 Standard Error for the Kappa Number 123

Table 5.3 Crystallinity Index of the OPF Vascular Bundle Fibres 140

xi

Table 5.4 Assignments of FTIR Absorption Bands of OPF

Vascular Bundle Fibres.

145

Table 5.5 ANOVA for AP Treatment and Time Effect on Pulp

Network Strength Properties

148

Table 5.6 DMRT for AP Treatment on Pulp and Paper Properties. 162

Table 5.7 ANOVA for Effects of AP Concentration and Reaction

Duration on Paper optical properties.

169

Table 5.8 Paper Printability 177

Table 6.1 Experimental Design Matrix Result from Box–Behnken

RSM.

181

Table 6.2 ANOVA of the Pulp and Paper Properties of the OPF

Vascular Bundles Fibres

185

Table 6.3 Correlation among the APMP Variables 213

Table 6.4 Optimal Condition for APMP of OPF VB 216

Table 6.5 Responses at the Optimum Condition of APMP for OPF

VB

217

xii

LIST OF FIGURES

Page

Figure 1.1 Pulp and paper lignocelluloses biomass. 3

Figure 2.1 Oil palm biomass residues Source: (Dungani et al., 2013). 10

Figure 2.2 Schematic diagram of PRC-APMP process (Source:-Andritz

2004)

25

Figure 2.3 ANDRITZ MSD Impressafinesr for P-RC APMP. 26

Figure 2.4 Oil palm fibrous biomass wastes. 57

Figure 2.5 Schematic diagram of oil palm frond. 58

Figure 2.6: OPF Monochrome photography (Hashim et al., 2011). 59

Figure 2.7 Monomers of lignin. 61

Figure 2.8 Hydrogen bonding at the cellulose fibre surface with water. 65

Figure 3.1 Schematic diagram of OPF vascular bundle fibres. 70

Figure 3.2 Overview of the general experimental work. 72

Figure 3.3 Schematic transformation of leaveless OPF midrib to

vascular bundles.

73

Figure 3.4 Sample of milled OPF vascular bundle fibres particles. 74

Figure 3.5 Sieve shaker machine and sieve plates. 74

Figure 3.6 Motorized laboratory press. 79

Figure 3.7 Schematic diagram for the alkaline peroxide mixing with

OPF.

80

Figure 3.8 Andritz Sprout Bauer single disc refinesr. 81

Figure 3.9 Somerville screener. 82

Figure 3.10 Glassed pulp disintegrator. 83

xiii

Figure 3.11 Canadian Standard Freeness tester. 86

Figure 3.12 Sherwood fibre quality analyzer. 90

Figure 3.13 Semi-automated laboratory Handsheet making machine. 91

Figure 3.14 Micro gauge of Précision Micrometer. 93

Figure 3.15 BrightimeterTM Micro S-5 brightness and opacity tester. 94

Figure 3.16 Frank PTI horizontal tensile testing machine. 95

Figure 3.17 Tear testing equipment. 96

Figure 3.18 Burst testing equipment. 97

Figure 4.1 Fibre dimensions. 105

Figure 4.2 SEM-EDX analysis of the raw OPF biomass. 114

Figure 5.1 Effect of AP concentration on yield with varying OPF VB-

AP reaction duration.

119

Figure 5.2 Reject percentage. 121

Figure 5.3 Effect of AP concentration and time on Kappa number. 123

Figure 5.4 Effect of chemical charge and time on CSF. 127

Figure 5.5 Graph of CSF and bulk estimating conformability of the

fibre.

128

Figure 5.6 Schematic diagram of the various crystallinity conditions of

AP fibres

130

Figure 5.7 Fibre length distribution of OPF pulp produced under optimal

condition.

132

Figure 5.8 Effect of AP concentration and time on cogenerated fines. 133

Figure 5.9 Scanning Electron Micrograph of OPF vascular bundle intact

surface and transformation to fibrillated mass after APMP

system.

135

xiv

Figure 5.10 TGA curves for OPF vascular bundle fibres. 137

Figure 5.11 DTG curve of the raw and extracted OPF VB fibres. 138

Figure 5.12 X-ray diffractometry patterns of APMP pulp from OPF

vascular bundles.

141

Figure 5.13 FTIR spectra of OPF VB fibres. 143

Figure 5.14 Effect of AP treatment on paper apparent density. 149

Figure 5.15. Effect of AP treatment duration on the tensile index of OPF

fibre web.

151

Figure 5.16 Effect of AP treatment duration on the burst index of OPF

fibre web.

153

Figure 5.17 Effect of AP treatment duration on the tear index of OPF fibre

web.

155

Figure 5.18 Correlation between paper apparent density and tensile

index.

159

Figure 5.19 Tensile energy absorption (TEA) at different AP

concentrations.

163

Figure 5.20 Effects of AP concentrations on ISO brightness. 166

Figure 5.21 Effect of AP concentrations and time on paper opacity. 167

Figure 5.22 SEM images of AP paper web at different AP concentrations. 171

Figure 5.23 Effect of EFB nanolaminate coating on OPF APMP paper

strength.

175

Figure 6.1 Normal percentage probability and studentized residual plots

for (A) Screened pulp yield and (B) Kappa number of

alkaline peroxide pulp.

190

xv

Figure 6.2 Normal percentage probability and studentized residual plots

for (C) tensile index and (D) burst index of alkaline peroxide

pulp and paper properties.

191

Figure 6.3 Normal percentage probability and studentized residual plots

for (E) tear index and (F) ISO brightness of alkaline peroxide

pulp and paper properties.

192

Figure 6.4 Normal percentage probability and studentized residual plots

for (G) Opacity of alkaline peroxide pulp and paper

properties.

193

Figure 6.5 3-D Response surface plot for screen yield.. 195

Figure 6.6 3-D Response surface plot for Kappa number. 198

Figure 6.7 3-D Response surface plot for tensile Index. 200

Figure 6.8 3-D Response surface plot for burst Index. 203

Figure 6.9 3-D Response surface plot for tear Index. 206

Figure 6.10 3-D Response surface plot for ISO brightness. 208

Figure 6.11 3-D Response surface plot of the paper opacity. 209

Figure 6.12 Optimum conditions for APMP of OPF VB. 218

Figure 6.13. Predicted vs experimental outcome at optimality. 219

xvi

LIST OF ABBREVIATIONS

ABS Alcohol Benzene Solubility

A.D. Anno Domini (Before Christ)

ANOVA Analysis of Variance

AP Alkaline Peroxide

API Alkaline Peroxide Impregnation

APMP Alkaline Peroxide Mechanical Pulping

APP Alkaline Peroxide Pulping

BBD Box-Behnken Design

CCD Central Composite Design

CGF Cogenerated Fines Fibres

CMP Chemimechanical Pulping

CMR Chemical-Mechanical Refining

COD Chemical Oxygen Demand

CSF Canadian Standard Freeness Expressed in Terms of Millilitres

CWT Cell Wall Thickness

DF Degree Of Freedom

DPTA Diethylenetriaminepenta Acetic Acid

EC European Commission

EDTA Ethylene Diamine Tetra Acetic Acid

EFB Empty Fruit Bunches

FAO Stat Food and Agricultural Organization Statistics

FL Fibre Length

FT-IR Fourier Transform Infrared

H2O2 Hydrogen peroxide

HWS Hot Water Solubility

ISO International Standards Organization

KBr Potassium bromide

LD Lumen diameter

L/D Lumen Width/Fibre Diameter

LSC Light Scattering Coefficient

xvii

MOA Ministry of Agricultural

MPPMA Malaysian Pulp and Paper Manufacture Association

Mt Metric Ton

NaOH Sodium hydroxide

OPF Oil Palm Frond

OPF VB Oil palm fronds vascular bundles

OPFB Oil Palm Fruit Bunches

OPT Oil Palm Trunk

PSI Pounds Per Square Inch

PTI Paper Testing Instrument

PRC-APMP Pre conditioning with refinesr chemical in Alkaline Peroxide

Mechanical Pulping

R&D Research and Development

RR Runkel Ratio

RSM Response Surface Methodology

SEM Scanning Electron Microscopy

SPSS Statistical Package For Social Sciences

SS 1% Sodium hydroxide Solubility

TAPPI Technical Association of the Pulp And Paper Industry

TCF Totally Chlorine Free

TEA Tensile Energy Absorption

USA United States of America

VB Vascular bundles

WRV Water Retention Value

wt/wt Weight by Weight

http://clk.about.com/?zi=13/1tO&ity=indexSEM&o=4924&eng=CSE&zu=http%3A%2F%2Fchemistry.about.com%2Fod%2Fpressureconversions%2Fa%2FConverting-Atmospheres-To-Psi.htm%3Futm_term%3DConversion+Tables+KPA+to+PSI%26utm_content%3Dp1-main-3-title%26utm_medium%3Dsem-rel%26utm_source%3Dgoogle%26utm_campaign%3Dadid-86c65312-9959-42e2-a78e-13876ee597c5-0-ab_gsb_ocode-4924%26ad%3DsemD%26an%3Dgoogle_s%26am%3Dbroad%26q%3DConversion+Tables+KPA+to+PSI%26dqi%3Dwhat%2520is%2520the%2520full%2520meaning%2520of%2520psi%26o%3D4924%26l%3Dsem%26qsrc%3D6%26askid%3D86c65312-9959-42e2-a78e-13876ee597c5-0-ab_gsb

xviii

LIST OF SYMBOLS

oC Degree Celsius

Nm Nanometer

Mm Millimeter

µm Micrometer

ml. Millilitre

mN Millinewton

mN/m² Millinewton per square metre

g/m² Gramme per square meter

L Litre

Nm/g Newton meter per gramme

kPam2/g Kilopascal square meter per gramme

xix

PEMULPAAN MEKANIK PEROKSIDA BERALKALI BAGI BERKAS

VASKULAR PELEPAH KELAPA SAWIT

ABSTRAK

Penyelidikan ini mengkaji kualiti bagi pulpa dan kertas yang diperoleh daripada

rawatan peroksida beralkali (APMP) berkas vaskular pelepah kelapa sawit (OPF) dari

spesis Elaeis guineensis. Matlamat utama kajian ini adalah untuk mengkaji potensi

OPF VB sebagai sumber gentian bagi penghasilan pulpa melalui teknik APMP, yang

dijana melalui proses pemulpaan mekanik peroksida beralkali (APMP). Kesan

penskrinan bagi berkas vaskular OPF dirawat AP dilakukan pada kepekatan AP yang

berbeza. Kepekatan-kepekatan ini termasuk kepekatan AP rendah (1.0%: 1.5%; NaOH:

H2O2), sederhana (2.0%: 2.5%; NaOH: H2O2) and tinggi (4.0%: 5.0%; NaOH: H2O2).

Kesan-kesan bagi pembolehubah heterogen pemulpaan peroksida beralkali (APMP)

(masa pememasakan, kepekatan natrium hidroksida dan kepekatan hidrogen

peroksida) terhadap sifat-sifat pulpa dan kertas (hasil penskrinan, nombor Kappa,

indeks tegangan, indeks koyakan, indeks kepecahan, kecerahan ISO dan kelegapan),

telah dikaji untuk menentukan keadaan operasi yang optimum. Kaedah permukaan

sambutan (RSM) menggunakan rekabentuk Box-Behnken menunjukkan gentian-

gentian berkas vaskular OPF adalah sebandigan degan gentian kayu lembut dan kayu

keras yang digunakan sebagai pulpa komersil dalam pembuatan kertas. Keputusan

setara menunjukkan bahawa biojisim OPF VB yang melalui proses APMP

menghasilkan pulpa terskrin dalam anggaran 45% - 63%. Analisis statistik

menunjukkan aras bererti bagi kesan kepekatan AP terhadap semua sifat-sifat pulpa

dan kertas yang dikaji pada aras keyakinan 95%, degan sokongan imej melalui

xx

mikroskopi imbasan elektron (SEM). Model-model regresi yang dibentuk

menunjukkan keadaan operasi optimum telah dicapai melalui 2.35% NaOH, 5.00%

H2O2 dan tindakbalas antara OPF VB-AP pada 53.41 minit masa masakan. Keputusan

ini adalah hasil pulpa maksimum yang diskrin (53.39%), dengan keputusan maksimum

bagi sifat-sifat kertas (cth., indeks kepecahan, indeks koyakan, indeks tegangan,

kecerahan ISO dan kelegapan) iaitu 6.55 kPam2/g, 6.22 mNm2/g, 9.92 Nm/g, 28.50%

and 99.71%, masing-masing beserta 80.27 nombor Kappa. Berkas vaskular OPF telah

menunjukkan potensinya sebagai gentian alternatif dan sumber bahan mentah bagi

penjanaan pulpa dan kertas melalui pemulpaan mekanik peroksida beralkali yang

mesra alam lagi ekonomik.

xxi

ALKALINE PEROXIDE MECHANICAL PULPING OF OIL PALM

FRONDS VASCULAR BUNDLE FIBRES

ABSTRACT

This study investigates the quality of pulp and paper obtained from alkaline

peroxide (AP) treatment of oil palm (Elaeis guineensis) fronds (OPF) vascular bundle

or OPF VB. The principal aim of this study is to assess the potential of OPF VB as raw

material and fibre source for pulp production via Alkaline Peroxide Mechanical

Pulping (APMP). Screening effect of AP treated OPF VB fibres was carried out at

different AP concentrations. These concentrations include AP prepared at low (1.0%:

1.5%; NaOH: H2O2), medium (2.0%: 2.5%; NaOH: H2O2) and high (4.0%: 5.0%;

NaOH : H2O2) concentrations. The effects of heterogeneous APMP variables (i.e.,

cooking time, sodium hydroxide concentrations and hydrogen peroxide

concentrations) on the pulp and paper properties (screened pulp yield, Kappa number,

tensile index, tear index, burst index, ISO brightness and opacity), were studied to

determine the optimum operating conditions. Response Surface Methodology (RSM)

using Box-Behnken design was used to explore the effect of selected variables on the

different responses. Results indicated that the vascular bundle fibres compare

favourably with the softwood and hardwood fibres used as commercial pulp for paper

making. The results equally revealed that the biomass was pulpable with AP liquor and

subsequent refining, resulting in screened pulp yield ranging from 45% to 63%.

Statistical analysis shows significant effect of AP concentrations on all of the pulp and

paper properties at 95% confidence level, in line with the morphological changes

acquired from Scanning Electron Microscopy (SEM). Regression models show that the

xxii

optimal operating conditions of the AP were found to be 2.35 % NaOH, 5.00 % H2O2

and a 53.41 minutes cooking time. This results in maximum screened pulp yield

53.39% paper strenght value i.e., burst index, tear index, tensile index, ISO brightness

and opacity were 6.55 kPam2/g, 6.22 mNm2/g, 9.92 Nm/g, 28.50 % and 99.71%,

respectively with 80.27 Kappa number. The OPF VB fibres were shown to be a

potential alternative fibrous raw material for pulp and paper application and this was

made possible via the environmentally compatible and economic APMP process.

1

CHAPTER 1

1 INTRODUCTION

1.1 General Background

Pulp and paper demand and consumption are a function of the level of

development and civilization of the humanity. This implies that the more developed

a nation is, the more the rate of pulp and paper consumption. The demand for pulp

and paper fibre resources is largely determined by the society’s dependence on

paper, paper boards and other related products for human welfare. The Directorate

General of Manufacture Based Industry (DGMB), Ministry of Industry Indonesia

reported that global demand for paper has grown by 2.1% annually (Adi et al., 2016).

Pätäri et al., (2016) reported that an increase in the global population would lead to

the enhancement of paper needs. According to the report, the global population and

economic growth predominantly focusing on developing and emerging countries is

expected to increase by 1.3 billion inhabitants by 2030. Hence, industries such as pulp

and paper is expected to brace up to the sustainability of the sector. Presently, despite

an increasing transition to digital media usage, the global pulp and paper industry still

enjoys the benefit from an increased pulp based product consumption (Ajani, 2011;

Lovins & Cohen, 2011). The Paper consumption kg/capita as of 2014 was: North

America (221); EU (56); Japan (215); China (75); Korea, Taiwan, Hong Kong,

Singapore & Malaysia (159); Latin America (47) and Africa (8). On average, each

person consumed 57 kg of paper in 2014 (RISI, 2016). This level of per capita

consumption is due to some factors, which include; the economic growth; increasing

2

literacy rate; changing demographics with higher urbanization (Huang 2016). Other

factors include increasing living standards, aspirations for changing lifestyles and

growth of mass communication, which demands for high-quality paper and paper

products (Goryakin et al. 2015).

It is projected that by 2021, the global paper production would rise to 521

million tonnes per annum. Out of this projected figures, 177 million tonnes (44%) is

expected to originate from Asia while the remaining 225 million tonnes (56%) would

come from elsewhere (Perkins & Rawski, 2008).

1.2 Pulp and Paper Lignocellulose

Wood has been the primary paper fibre for less than a century, with paper pulp

demand being predominantly used as writing-printing paper, newsprint and industrial

paper (packaging and wrapping paper, and paper board) (Holik, 2012). Global paper

demand has resulted in two out of every five trees cut for pulp, , which is one of the

main reasons for the destruction of forests worldwide (Middleton, 2013). Wood

sourced pulp and paper has been characterized by a heavy-duty industrial process to

turn wood into paper (Main, et al., 2015). Wood pulping processes release large

amounts of dangerous pollutants, such as chlorine, dioxin and furans into the air and

water bodies (Udohitinah & Oluwadare, 2011). As forests diminish and public opinion

to save forests grows, there is increasing interest in alternative fibre crops (Laftah and

Wan Abdul Rahman, 2016). Fig. 1.1 shows the common sources of lignocellulose used

in pulp and paper industries (Leponiemi, 2008).

3

Lignocellulose biomass contain cellulose, hemicellulose, lignin and extractives

with the ratio of these components varying depending on the species of wood. While

some of the fibres are virgin fibres, some are obtained from- recycle papers and non-

wood fibres. The management of the forest biodiversity is a concept towards the

preservation of some characteristic flora and fauna in the tropical region (Kozuka,

2013).

Figure 1.1 Pulp and paper lignocelluloses biomass.

Traditionally wood has been considered as the major raw biomass for paper

making. Countries with limited forest size and limited plantation area like China are

more prone to the used of non-wood as raw material for paper making (Carlsson et al.,

2009; Ai & Tschirner, 2010; Mossello et al., 2010). There is significant growth of

regional imbalances in the fibre supply globally due to shortage supply of virgin pulp.

4

The continued rivalry in the fibre demand for pulp and paper, housing and wood for

fuel has equally contributed to the reduce dependency of pulp and paper industries on

virgin pulp (Carlsson et al., 2009; Ai & Tschirner, 2010; Mossello et al., 2010). Sequel

to this development, agricultural residues, such as cereal straws of wheat, rice, barley

and lately empty fruit bunches (introduced by EKO paper mills Malaysia) has been

gaining increasing interest as fibrous source of raw materials in the pulp and paper

industries (MPOB, 2012). In fact, utilisation of the agricultural residue as raw material

for pulp and paper making would ameliorate the persistence waste management

problems.

1.3 Problem Statement

Currently, due to the shortage of wood fibres and economic outlay the use of

non-woods in pulp and paper production in several available and wood deficiency

countries have been gaining increasing attention. Despite the noticeable deficiencies in

the use of non-woods with respect to woods (Fazeli et al., 2016), agro wastes have been

receiving increasing considerations as source of natural cellulose fibre in agro-based

industries including pulp and paper industries. This development is as a result of

imminent environmental instability in the area of biodiversity. Since the introduction

of agro waste as alternative to wood in pulp and paper manufacture, biomass such as

corn stalks (Daud et al., 2016), wheat and rice straws (Reddy and Yang, 2015), have

been used for commercial pulp and paper making. Many research reported on the use

of EFB for pulp and paper (Dermawan et al., 2014; Daud and Law, 2010; Ghazali et

al., 2012), leaving the oil palm (Elaeis guineensis) fronds vascular bundle fibres yet

fully investigated.

5

A number of methods of fibre extraction have been assessed in the literature

(Daud and Law, 2010; Reddy and Yang, 2015), most of, which operate at high

temperatures and pressures and a few of them releasing environmental hazardous

effluents. Pulping industry has been reported as the second largest polluting industry

after mining (Singh et al., 2014). Air contaminants released from pulping include

particulate matter, sulphur dioxide, and total reduced sulphur (TRS) compounds. To

counteract the pollution issue, adoption of an eco-friendly technique with economic

criteria is needed. To this date, Alkaline Peroxide Mechanical Pulping (APMP) is the

best known technique that not only fit the aforementioned criteria but is also flexible

in its operational size and quality of pulp as the end-product quality. Since the

introduction of alkaline peroxide mechanical pulping by Cort and Bohn in the late 80s,

many Kraft mills in China had been converted to an APMP system (Ghazali, 2006) and

research continue to flourish around the use of various non-wood material, except the

oil palm frond, OPF. This study therefore delves into the Alkaline Peroxide Mechanical

Pulping of OPF VB by accomplishing the following objectives:

1.4 Research Objectives

a) To study the chemical and morphological properties of fibre residing the OPF

vascular bundle.

b) To study the thermal, morphological and chemical changes in the AP- treated

OPF vascular bundle by the use of TGA, SEM and FTIR of the extracted fibres

respectively.

6

c) To further characterize the effect of the alkaline peroxide treatment on the

strength, optical and morphological properties of the handsheet from the AP-

treated OPF vascular bundle fibres.

d) To develop regression model using RSM via Box Behnken design of experiment

to determine the most improved and enhanced OPF pulp and paper properties.

1.5 Structure of Dissertation

The thesis consists of seven chapters that employ the use of instrumental

analysis, empirical and statistical modelling approach to determine the suitability of

OPF vascular bundle fibres as an alternative source of fibre for pulp and paper products.

Therefore in this dissertation:

Chapter 2: reviews the literature on the use of alkaline peroxide in pulp and

paper making. The suitability of non-wood and agricultural residue for pulp and paper

was enumerated. Furthermore more light on the benefit of the utilization of the

statistical tool in developing and optimizing the pulping condition for pulp and paper

production brought to the fore.

Chapter 3: contains all the experimental approaches undertaken in this study

and gives an insight to the various tools used to analyze the obtained result.

Chapter 4: reports the result of analysis and Characterisation of the OPF

vascular bundle fibres.

7

Chapter 5: presents the outcome of the preliminary investigation of the alkaline

peroxide treatment duration and level effects on the pulp and paper properties of the

oil palm fronds vascular bundle fibres.

Meanwhile, Chapter 6: presents the result of the combined effects of three

independent variables (hydrogen peroxide concentrations, sodium hydroxide

concentration and cooking time) on the pulp and paper properties of the OPF vascular

bundle fibres using Box Behnken model of the Response Surface Methodology (RSM)

for experimental design. The chapter reports the analysis and process optimization

modelling of the alkaline peroxide treatments on the pulp and paper properties.

The work is wrapped up in Chapter 7 by evaluation of the extent in , which the

objectives had been achieved as well as recommendations for future research to

overcome the identified challenges pertinent to APMP of OPF VB.

8

CHAPTER 2

2 LITERATURE REVIEW

2.1 Current Overview of Global Pulp and Paper Industries

Pulp and paper mills are big business around the world, generating $563.6

billion in revenue during 2013 (Singh et al., 2014). The global paper and paperboard

demand as at 2011 stood at 402 million tonnes per annum whereas about 7,745 mills

existing globally can produce only 192 million tonnes of pulp. The paper demand has

almost doubled in 20 years from 242.79 million tonnes in 1990 to 402 million tons by

2011. Paper consumption and production growth in Asia is expected to double by 2030

from 2010 levels (Alexandratos & Haen, 1995; Golley & Tyers, 2006; Oh et al., 2010).

In tropical countries like Malaysia, oil palm plantation has constituted one of

the major source of gross national income (GNI). In Malaysia the oil palm export

constituted $22.31 billion USD to the country’s gross national income in 2014 and it

is expected to rise to $55.8 billion USD by the year 2020 (Awalludin et al. 2015). Food

and Agricultural Policy Research Institute FAPRI (2010) predicts that Malaysian palm

oil production will increase by 26.5 percent, to 23.4 million tonnes by 2020, slightly

less than the predicted Indonesian production of 28.5 million tonnes (Ivancic and Koh,

2016). Oil palm industry in Malaysia with its 6 million hectares of plantation, produced

biomass as much as 100 million tons (Abdul Khalil et al., 2010). In order to maintain

steady growth of oil palm plantation, large areas of primary and secondary forest have

been cut or burned down to make way for oil palm plantations in Indonesia and

9

Malaysia, the two countries , which produce 80.5% of the world’s palm oil (Ivancic

and Koh, 2016 ).

The conducive climatic condition of Malaysian climate has contributed

absolutely to the growth of oil palm plantation, making it the most important

agricultural crop in Malaysia and has contributed immensely to the national economic

growth (Leibo, 2015). This has made Malaysia the second world largest producer of

oil palm.

The rapid growth of the palm oil industry in South-East Asian countries like

Malaysia is as a result of the palm oil being the world’s largest source of edible oil and

hence constitutes its major economic crop. This has contributed to the expansion of the

area of plantation and making Malaysia the second largest producer of oil palm after

Indonesia (Ivancic and Koh, 2016). The types of waste biomass generated in oil palm

industries in Malaysia as shown Fig 2.1 are generated from both the mill and the

plantation site (Dungani et al., 2013). Fig. 2.1 shows that oil palm fronds, (OPF), and

the oil palm trunks, (OPT), are generated from the plantation sites while the empty fruit

bunches (EFB), palm oil mill effluent (POME), mesocap fibre (MF), and Kernel Shell

(KS) are generated from the oil palm mill.

Increase in oil palm plantation translates to the huge generation of the oil palm

biomass, globally over 190 million tonnes of solid and liquid residues are being

generated from the palm oil industries. In Malaysia, about 100 million tonnes dry

weight of these biomass wastes is projected by 2020, of , which the OPF constitutes

70% and is considered the highest (Wanrosli et al., 2007). These biomass are usually

10

left on the site resulting to environmental issues while undergoing decomposition,

which is aimed at fertilising the soil (Lim et al., 2000). Oil palm fronds are agricultural

residues by-product biomass generated from oil palm activities and made up of the

petiole, rachis and leaflets.

Figure 2.1 Oil palm biomass residues Source: (Dungani et al., 2013).

Owing to its abundance, biodegradability and problem of disposal, has

contributed to the present currently increases farming costs. In addition it has lead to

environmental deterioration through pollution, fires, and pests. According to Abdul

Khalil and co-workers (2008), oil palm frond contains various sizes of vascular bundle

fibres imbedded in thin-walled parenchymatous ground tissue. While the parenchyma

cells act as a storage medium, the vascular bundle fibres act as mechanical support for

the oil palm frond. This growth of the palm oil industry has caused a corresponding

11

increasing in the biomass wastes derived from the pruning management practices and

replanting operations (Daud and Law, 2010; Paltseva et al., 2016).

Malaysian and Indonesian based researchers have been saddled with research

and development into economic viability of oil palm wastes in order to minimise if not

totally eradicates the environmental issues associated with the poor management of the

biomass. Biomasses such as agricultural crops and residues, forest resources and

residues, and municipal wastes are the largest source of cellulose in the world

(Awalludin et al. 2015). Among the merits of non-wood plants include short growth

cycles, moderate irrigation and fertilization requirements and low lignin content

resulting to reduced energy and chemicals use while pulping (Wang & Chen, 2013).

Agricultural by-products are annually renewable, available in abundance and of limited

value at present. The use of non-wood fibres and agricultural wastes in papermaking

has been proposed by some environment advocates as a way to preserve natural forests

and prevention of global warming. EFB have proven to be useful raw material for the

pulp and paper industries (Rushdan, 2002).

In countries where the supply of wood resources is inadequate, the rate of paper

consumption continue to be on the increase despite the challenges of commercial

papermaking with respect to limited wood resources. Many ecological problems

occasioned by deforestation such as global warming, hurricanes, flooding, droughts are

among some of the detrimental global environmental problem facing humanity

(Middleton, 2013). While global campaign towards improvement in reforestation has

been on the increase, the utilisation of agricultural residues have attracted the interest

of environmentalist and scientist. The suitability of these agricultural biomass through

12

various analytical investigation has been the first step in their utilization. For paper

making, the morphology and chemical properties of fibres of the lignocelluloses for

pulp and paper are of great importance to the suitability of pulping and papermaking

processes, as well as for final paper products.

In India, the pulp and paper industry is divided into three sectors based on the

raw materials usage (Reddy & Ray, 2011). These include:-

a) The wood based mills , which comprise of 26 large integrated paper mills using

both wood and bamboo, contributes to 31% production of the mill production

and this translates to 3.19 million tonnes of pulp per annum.

b) The 150 agro-based mills constitute about 25% of the total output and

c) The 538 recycle fibre mills contribute to 4.72 million tonnes, or 47% total

paper product.

In Malaysia, the total capacity of the paper mills is about 50 T/day that

translates to about 1,300,000 T/year. Of all these, integrated pulp and paper mill in

Sipitang, Sabah (Sabah Forest) uses wood fibres (Grafton & Jago, 2013). Table 2.1

shows the total annual production capacity of the paper mills in Malaysia and the actual

production per annum.

It is apparent that the production capacity per annum is short 10.52% of the

total annual capacity of the of the mills. This shortfall is attributable to the lack of raw

material and the maintenance culture of the machinery, , which often breakdown.

There are significant regional differences in pulp and paper consumption and

production patterns. Asia is the biggest region in term of paper consumption and

13

production, about twice as big as the North America (Fontagné & Fouré, 2013; Taylor

et al., 2013). Perhaps the most striking fact is that Africa’s paper consumption and

production are so extremely low compared to the other region. The paper making

process thus far has mainly used wood materials from the cut, debarked, chipped, and

pulped tree stems. The continual growth in pulp and paper production entails massive

deforestation.

The pulp and paper industry is currently facing broad structural changes

because of global shifts in demand and supply (Hujala, (2013), as a result of the short

supply of wood materials. This challenge has led to the reductions in the number of

pulp and paper mills, lower rates of capacity growth, employment downturns, and a

loss of market share to foreign competitors (Brown and Wang 2015). These structural

shifts portray an industry that has encountered difficulty in adapting to a more

competitive environment and earning sufficient profits to generate a return on

investment that covers opportunity cost. These changes have significant impacts on

most national economies worldwide. Increasing competition for wood supplies for

construction purposes coupled with gradually rising costs of wood have generated

renewed interest in the use of nonwood plant fibres for papermaking in the highly

industrialized countries (Smith, 1997). It is interesting to note that some environment

advocates have proposed the use of non-wood fibres in papermaking as a way to

preserve natural forests and prevention of global warming.

Both wood and non-wood resources are currently being exploited for the

manufacturing of pulp, paper and paper boards. In countries where the supply of

wood resources is inadequate, the rate of paper consumption has been on the increase

14

despite the challenges of commercial papermaking with respect to limited wood

resources.

The use of agricultural residues in pulping and papermaking is gradually

gaining attention because of the problem of disposal, , which currently increases

farming costs and causes environmental deterioration through pollution, fires, and pests

(Bajpai, 2015). In 2003, Malaysia’s Eko Pulp & Paper Sdn Bhd (Company No. 590644-

K).

(EPP) was established in joint collaboration with Forest Research Institute of

Malaysia (FRIM) and Malaysian Palm Oil Board (MPOB) to undertake research and

development and commercialization of pulp production using the oil palm Empty Fruit

Bunches (EFB) (MPOB 2012).

Many ecological problems occasioned by deforestation such as global

warming, hurricanes, flooding, droughts are among some of the detrimental global

environmental problem facing humanity(Middleton, 2013). Many attempts have been

made to simplify the design of the mill to achieve the reduction in the effect of the

economies of scale (Karltorp & Sandén, 2012).

The global pulp production is expected to increase simultaneously with the

consumption of paper, and this is especially through for fines paper with 6.5% increase

in global non-woods consumption (Laftah and Wan Abdul Rahman, 2016). In China

and India over 70% of raw material used by the pulp industries come from non-woody

plants and agricultural residues such as reeds, bamboo, bagasse and cereal straw (Al-

Mefarrej et al., 2013 ). Biomasses such as agricultural crops and residues, forest

15

resources and residues, and municipal wastes are the largest source of cellulose in the

world. Non-wood plants offer several advantages including short growth cycles,

moderate irrigation and fertilization requirements and low lignin content resulting in a

reduced energy and chemicals consumption during pulping (Wang & Chen, 2013).

Table 2.1 Annual Paper Production from Malaysian paper mills

No. Company Total Capacity per Annum

(mt)

Production per

Annum (mt)

1 Cita Peuchoon 30,000 24,000

2 Johmewah 35,000 8,000

3 Genting Sanyen 300,000 250,000

4 MudaPaper

(Kajang)

170,000 140,000

5 Muda Paper (S.

Prai)

130,000 140,000

6 Malaysia

Newsprint

250,000 250,000

7 Nibong Paper 60,000 60,000

8 Pascorp Paper 140,000 135,000

9 Pembuatan Kertas

(Perak)

3,000 3,000

10 Sabah Forest 165,000 165,000

11 Kimberly-Clark 45,000 35,000

12 See Hua Paper 12,000 10,000

13 Talping Paper 2,400 2,400

14 Then Seng Paper 15,000 11,500

15 Trio Paper 30,000 23,000

16 Union Paper 12,400 6,000

17 United Paper

Board

80,000 60,000

18 Yeong Chaur S 3,600 3,600

TOTAL 1,483,400 1,327,300

(Source:- MPPMA- 2003)

16

Agricultural by-products are annually renewable, available in abundance and

of limited value at present.

2.2 Pulp and Paper Production

Modern pulp and paper manufacturing evolved from the ancient art first

developed in China, ca. 105 A.D (Singh et al., 2014). Papers are manufactured from

cellulosic fibres, generally wood (composed cellulose, lignin, hemicellulose, and

extractives (e.g., resins, fats, pectins, etc.)), recycled paper, nonwood raw materials

such as bagasse, cereal straw, bamboo, reeds, esparto grass, jute, flax, and sisal and

agricultural residues (Main et al., 2015). In principle, papers are made by raw material

preparation (wood chipping and size reduction) and handling, Pulp manufacturing (to

separate and clean the fibres), Pulp Washing and Screening, Chemical recovery,

Bleaching, Stock Preparation, and Papermaking (Samariha and Khakifirooz 2011). The

main goal of pulping process is to remove as much lignin as possible without sacrificing

fibre strength, thereby separating the fibres and removing impurities that can cause

discoloration and paper instability. Hemicellulose, which is similar to cellulose in

structural composition and function plays an important role in fibre-to-fibre bonding in

papermaking. Other components of wood that are removed during pulping process are

extractives (e.g., oleoresins and waxes).

2.3 Pulping Technique

Two basic processing steps are involved in pulp and paper production this

include the conversion of fibrous raw material into pulp followed by the conversion of

the pulp into paper. This processes could be achieved mechanically or chemically. The

17

pulp is then bleached and further dispersed in water and reformed into a web,

depending on the type and grade of paper that is needed to be produced (Bajpai 2015).

Table 2.2 gives the common pulping method for lignocelluloses materials. The first

step in pulping is the cost efficient and environmental sound pulping technique even at

small scale. This is what forms the interest of researchers exploring the avenue of using

non-wood and agricultural residue as alternative raw material to wood. Globally,

several factors have contributed to increasing the level of industry interest in the use of

nonwood and agricultural residue as fibre sources. Some of these factors include :-

(a) environmental pressure to stop using trees due to deforestation

(b) projections of world fibre shortage by 2010 (Jepma, 2014), and the need to

find alternative fibre sources

(c) abundance of agricultural residues (such as corn stover, sugar cane bagasse,

banana pseudostem and wheat straw) that are otherwise burned off fields

and

(d) opportunities of integrated mill to produce multiple products (oils, textile

fibres, papermaking fibres, board fibres, plastics, food) from a simple fibre

source, , which provides unique opportunities for sustainable agriculture.

Among the qualities governing good pulp and paper material in paper

production is, increasing the amount of cellulose and decreasing the value of lignin, the

extractive content, and the percentage ash content. All these result in increased yield,

a decrease of chemical material consumption, and cooking time (Panshin & Zeeuw,

1980).

18

Table 2.2 Common Pulping Method for Lignocellulosic Materials

Pulping

method

Chemical used Properties of isolated pulp Application of pulp Refences

1 Kraft/

sulphate

Sodium hydroxide +

sodium sulphide

Strong, low brightness

(dark brown)

Making boxes, paper bags and

wrapping paper. Can also be used

for writing paper and paperboard

when bleached.

(Kim et al., 2016)

2 Sulphite Sulphurous acid / sodium

sulphite

High flexibility and

requires little bleaching

Used in making paper and special

purposes.

(Moradbak et al.,

2015)

3 Soda Sodium hydroxide +

anthraquinone

Have properties similar to

sulphite

Ideal for all paper uses. (Wutisatwongkul et

al., 2016)

4 organosolv Organic solvents and

organic acids

Properties still under

review

Preliminary results suggest

multi-purpose uses.

(Moral et al., 2016)

5 Biopulping Involve the use of white

fungus

Increase tear index, low

Kappa number and other

properties are still under

investigations.

Results suggest possible uses in

all aspects of the paper.

(Singhal et al., 2015)

6 APMP/PRC-

APMP

Hydrogen Peroxide+

Sodium hydroxide

High yielding pulp, high

iso-brightness, right paper

properties

Ideal for all paper uses (Cort and Bohn, 1991)

7 APP Hydrogen peroxide +

Sodium Hydroxide

Same as obtained for

APMP

Preliminary laboratory result

suggest multi-purpose use

(Ghazali et al., 2009)

19

The second step is the choice of pulping technique. Among the array of the

environmentally friendly pulping is alkaline pulping, organosolv pulping, and Chemi-

mechanical pulping (Sridach, 2010; Bajpai, 2013a).

There are three principal groups of pulping processes namely mechanical

pulping, chemical pulping and bio-pulping. Mechanical pulpingis a pulping method

that uses disc refinesr on raw wood (mainly softwood) against the abrasive surface with

the aim to de-fibre the raw material without the dissolution of lignin (Harinath et al.,

2013). Khakifirooz et al., (2012b) reported that this method is characterized by high

yield and usually more than 95% of the dryweight of the wood. High temperature and

pressure are used by some methods to increase the efficiency of the process. Although

mechanical pulping generates very low polluting effects but is an energy intensive

process, as the non-cellulosic wood components are not available conversely to what

obtain in chemical pulping (He et al., 2013). Chemical pulping involves the dissolution

of all the non-cellulosic components of the lignocelluloses biomass in cooking liquor

at high temperature and pressure thereby separating the fibres. Generally chemical

pulping gives better paper quality (Biermann, 1996; Bajpai, 2013a). However it is

characterized with greater environmental pollution (through its pulping and bleaching

process), capital intensive and operating costs are higher than those of mechanical

pulping. The yield of chemical pulping is about 50% of the dryweight of raw material.

An example of the method is: sulphate or kraft, sulphite, and soda pulping.

20

2.4 Hybrid Form of Pulping: Chemi-Mechanical Pulping

Hybrid pulping is another form of pulping, which involves a chemical pre-

treatment of the raw material, before a mechanical treatment to liberate the fibres. The

yields of these processes are situated between those for mechanical and chemical

pulping (Hosseinpour et al., 2014).

Chemi-Mechanical Pulping (CMP) has gained global attention as an

environmental benign pulping method (Khakifirooz et al., 2012b). It is a type of hybrid

pulping process involving impregnation of raw material with small amounts of

chemicals to soften the lignin, while it then employs mechanically treatment to liberate

the fibres. Masrol and co-workers (2015) reported that the pulp yields of these

processes are situated between those for mechanical and chemical pulping, due to the

synergistic operations of the two pulping protocol in CMP. Cort and Bohn (1991)

observed that heat is typically applied to improve pulping. The report further revealed

that this method is characterized by good fibre properties, low chemical application,

lower capital and operating costs compare to pure mechanical pulping. Chemi-

mechanical pulps can be used for low- to medium-quality papers, and with additional

processing they may be used for some high-end purposes. However,the most popular

and widely accepted process is the invention of a new CMP technology called

alkaline peroxide mechanical pulping (APMP) (Cort and Bohn, 1991). However, the

dissolved lignin and the other trace elements in the biomass are treated and discharged

into the environment.