Energy Procedia 68 ( 2015 ) 195 – 204

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1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of Scientific Committee of ICSEEA 2014doi: 10.1016/j.egypro.2015.03.248

2nd International Conference on Sustainable Energy Engineering and Application, ICSEEA 2014

Effect of combining chemical and irradiation pretreatment process to characteristic of oil palm’s empty fruit bunches as raw material

for second generation bioethanol

Anis Kristiania,*, Nurdin Effendib, Yosi Aristiawana, Fauzan Auliaa, Yanni Sudiyania aResearch Centre for Chemistry, Indonesian Institute of Sciences, Kawasan PUSPIPTEK 15314, Tangerang, Indonesia

bCenter of Nuclear Industry Material Technology – National Nuclear Energy Agency Kawasan PUSPIPTEK 15314, Tangerang, Indonesia

Abstract

Oil palm’s empty fruit bunches (OPEFB) as the waste from oil palm industry is one of lignocellulosic biomass feedstocks for a potential second-generation bioethanol production. Pretreatment process is a key process for producing bioethanol. OPEFB treated is expected to give better properties used for bioethanol production. This research aims to study the effect of pretreatment process by combining chemical and irradiation to OPEFB’s properties as raw materials in the hydrolysis reaction producing sugars which will be fermented into ethanol. The raw materials are characterized in term of crystallinity, chemical structure, chemical content, and surface morphology. Analysis results of chemical content showed that cellulose and hemicellulose content increased significantly while lignin content decreased significantly after pretreatment. The crystallinity measured by X-Ray Diffraction (XRD) showed that after pretreatment, their crystallinity index and the crystallite size increased significantly. While, the surface morphology and composition shown by Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) showed the changing in morphology surface and dominantly composed by carbon and oxygen. © 2015 The Authors. Published by Elsevier B.V. Peer-review under responsibility of Scientific Committee of ICSEEA 2014.

Keywords: bioethanol; chemical; EFB; irradiation; NaOH; pretreatment.

* Corresponding author. Tel.: +62-21-7590929; fax: +62-21-7560549.

E-mail address: aniskristiani87@gmail.com

© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer-review under responsibility of Scientific Committee of ICSEEA 2014

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196 Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204

Nomenclature

EFB empty fruit bunches OPEFB oil palm’s empty fruit bunches OPEFB-C oil palm’s empty fruit bunches treated by chemical method NaOH 10% OPEFB-CI 100 kGy oil palm’s empty fruit bunches treated by chemical and irradiation method 100 kGy OPEFB-CI 200 kGy oil palm’s empty fruit bunches treated by chemical and irradiation method 200 kGy OPEFB-CI 300 kGy oil palm’s empty fruit bunches treated by chemical and irradiation method 300 kGy OPEFB-CI 400 kGy oil palm’s empty fruit bunches treated by chemical and irradiation method 400 kGy OPEFB-CI 500 kGy oil palm’s empty fruit bunches treated by chemical and irradiation method 500 kGy

1. Introduction

Here Indonesia is the biggest palm oil producer in the world with oil palm plantation and crude palm oil production reaching 6.8 million ha and 19.3 million metric ton [1]. Palm oil industries generate approximately 20.2 x 106 ton/year of solid wastes which consist of OPEFB, fiber, and fruit shell [2]. Seeing those abundant residues, there are a lot of potencies from palm oil waste as a renewable energy. EFB is the residue generated at the thresher, where fruits are removed from fresh fruit bunches. Fresh fruit bunch contains only 21% palm oil, while the rest are 14-15% fiber, 6-7% palm kernel, 6-7% shell and 23% EFB which left as biomass. EFB and mesocarp fibre are the highest contributor of palm oil biomass, where by about 19.5mn and 12mn tones, respectively have been produced per year. Nowadays, utilization of biomass has attracted interest of researchers because of its potential applications.

Bioethanol production from lignocellulose biomass includes three main processes, which are pretreatment, hydrolysis and fermentation. Pretreatment process is an important process in series of processes to produce bioethanol. The major components of OPEFB are cellulose (44.2 %), hemicelluloses (33.5%), and lignin (20.4%) [3]. The properties of native lignocelluloses biomass make them resistant to enzymatic attack. The cellulose′s crystallinity, accessible surface area, protection by lignin and hemicelluloses, polymerization degree and acetylation degree of hemicelluloses are the main factors affecting the rate of enzymatic degradation [4]. The aim of pretreatment is to change these properties in order to prepare the materials for enzymatic degradation. Several pretreatment methods of lignocellulosic materials are physical pretreatment, physico-chemical pretreatment, chemical pretreatment, and biological pretreatment [5, 6]. Physical pretreatment can increase the accessible surface area and size of pores, and decrease the cellulose crystallinity and polymerization degrees. Different types of physical pretreatment such as milling (e.g. ball milling, two-roll milling, hammer milling, colloid milling, and vibro energy milling) and irradiation (e.g. by gamma rays, electron beam or microwaves) can be used to improve biodegradability of lignocellulosic waste materials [7]. Digestibility of cellulosic biomass has been enhanced by the use of high energy radiation methods, including -ray [8,9], ultrasound [10-12], electron beam [13,14], pulsed electrical field [15], UV [16], and microwave heating [17-19]. The action mode behind the high energy radiation could be one or more changes of features of cellulosic biomass, including increase of specific surface area, decrease of the degrees of polymerization and crystallinity of cellulose, hydrolysis of hemicellulose, and partial depolymerization of lignin. However, these high energy radiation methods are usually slow, energy-intensive, and prohibitively expensive [20,21].

In this research, we did pretreatment of OPEFB by combining chemical and irradiation method and studied their effect after pretreatment process, in term of their crystallinity, chemical structure, chemical composition, and surface morphology. Combining of two pretreatment methods aim to study the effect given to OPEFB as raw material for second generation bioethanol.

Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204 197

2. Materials and experimental

2.1. Materials

Raw material of oil palm’s frond used in this research is oil palm’s EFB from PT. Perkebunan Nusantara VII (PTPN VII) in Palembang, South Sumatra. While, chemical used pretreatment process is NaOH.

2.2. Instrumentation

Equipments used in this pretreatment process are milling-grinding machine, autoclave, glass equipments, XRD Phillip PW 1710, FT-IR spectroscopy (Shimadzu, Prestige-21) with ATR 4000 and SEM EDX ZEISS.

2.3. Procedure

2.3.1. Pretreatment

In this research, we use pretreatment technology of OPEFB by combining chemical and irradiation method. Chemical pretreatment used is NaOH 10 % followed by irradiation. EFBs fiber was dried and milled to a particle size ±3 mm, then treated by 10% NaOH solutions. The ratio of NaOH solutions and EFBs was 5:1. Pretreatment process was carried out at temperatures 150°C and 4-7 kg/cm2 of pressure for 30 minutes. EFBs-treated was washed with water until neutral pH and dried to a moisture content below 10%. The irradiation was conducted using an electron beam machine, with energy variation from 100 kGy with step of 100 kGy up to 500 kGy. The irradiations were carried out at the Isotope and Radiation Application Center, National Nuclear Energy Agency, Pasar Jum’at, South Jakarta.

2.3.2. Characterization

Solid samples are analyzed for their lignin, cellulose and hemicellulose content by using TAPPI T 13 m - 45 and ASTM 1104-56 method. Crystalinity samples were determined by using XRD methods. X-ray diffraction (XRD) analysis was carried out for crystallographic phase identification of the catalyst samples using a Phillip PW 1710 diffractometer, with Cu K irradiation at 40 kV and 30 mA, and a secondary graphite monochromator. The chemical structure of the three components was analyzed by using Fourier Transform Infra Red (FT-IR) spectroscopy in KBr phase using FT-IR spectrometer Shimadzu, Prestige-21 with ATR 4000 attached to an automatic data acquisition center. Surface morphology was observed by using Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM EDX) ZEISS at acceleration voltage of 15 kV and taken at 500x magnifications for analysis.

3. Result and discussion

Lignocellulose biomass is composed of cellulose, hemicellulose and lignin connected to each other because of amorphous structure and 1,4- bonding in cellulose and also the existence of lignin between cellulose chain [22]. Compositional analysis result of OPEFB is shown in Table 1.

Table 1 shows that cellulose content in OPEFB both treated by chemical and chemical-irradiation is higher than OPEFB untreated. Higher cellulose content in the sample can produce higher glucose, however hemicellulose content can also hydrolyze to xylosa, while lignin can produce derivative compound of phenol. The goal of pretreatment process is to remove structural and compositional inhibitor to hydrolysis process in order to improve the rate of enzyme hydrolysis and increase yields of fermentable sugars from cellulose or hemicellulose. The presence of lignin in lignocelluloses leads to a protective barrier that prevents enzyme attack in hydrolysis process. For hydrolysis process, the cellulose and hemicellulose must be broken down into their corresponding monomers (sugars), so that microorganisms can utilize them. So, during pretreatment process, lignin will decrease while cellulose and hemicellulose will increase.

198 Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204

Table 1. Chemicall compound contentt of OPEFB untreateed and treated

Sample

OPEFB unt

OPEFB-C

OPEFB-CI

OPEFB-CI

OPEFB-CI

OPEFB-CI

OPEFB-CI

Total l

treated 35.94

10.32

100 kGy 8.25

200 kGy 5.86

300 kGy 7.01

400 kGy 7.65

500 kGy 7.86

ignin (%) Cellulo

30.41

77.5

68.87

71.96

65.64

64.92

63.81

ose (%) Hemicel

20.70

6.83

14.27

15.20

13.94

13.39

13.45

llulose (%)

Ce

cellulportiowholecontit

Fiand 2arrang18.4°303) scattefrom Treatchem

Fig

ellulose moleculose in the planon is an amorphe fibers and restuents and chanig. 1 shows the

2 = 18.4°–25.6gement of cellu–25.6° which isin the region 32

ering dominatedOPEFB. The ced OPEFB by c

mical only. The h

g. 1. XRD pattern o

ules are randomnt is highly cryhous cellulose. Isulting in a disoges the crystalli XRD pattern o° indicating cry

ulose molecule. s the (012) peak2.06°–36.26° is d by intramoleccrystallinity of combining chemhighest crystallin

f untreated OPEFB

mly oriented anystalline and mIrradiation attacordered structureinity in the celluof OPEFB untreystalline region.The region at 2

k are cellulose ra cellulose reg

cular. Overall, XTreated OPEF

mical-irradiationnity index was g

(a) and (b). CI; (c)

d tend to formmay contain as mcks the structuree. The irradiatioulose.

m intra and intemuch as 80% ce of cellulose, pron of OPEFB c

ermolecular hydcrystalline regioroducing many

contributes to th

drogen bonds. Mons. The remaideffects throug

he degradation o

Most ining ghout of its

eated and treate. While, peak at2 = 13.3°–17.3region and origiion and it is als

XRD pattern at FB samples tendn gave higher cgiven by Treate

ed. Broad peak t 32.06°–36.26°3° which is the nated from intra

so a contribution2 = 18.4°–25

d to increase crystallinity inde

ed OPEFB by ch

was observed ° is peak resulte(-102) peak andamolecular scatn from the intra.6° belongs to

compared to OPex compared to hemical-irradiat

at 2 = 13.3°–1ed from crosslind the region at ttering while pea and intermoleccrystalline celluPEFB raw mateTreated OPEFB

tion 200 KGy.

17.3° nking 2 =

eak (-cular ulose erial. B by

CI 100 kGy; (d) CII 200 kGy; (e) CI 300 kGy; (f) CI 400 kGy; (g) CI 500 kGGy

Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204 199

The crystalliniity index and crrystallite size booth of untreated and treated OPEEFB was shownn in Table 2.

Table 2. Crystallinity inddex of OPEFB untreeated and treated

Sample

OPEFB u

OPEFB-C

OPEFB-C

OPEFB-C

OPEFB-C

OPEFB-C

OPEFB-C

Crysuntreated 38.33

C 59.48

CI 100 kGy 60.60

CI 200 kGy 62.45

CI 300 kGy 61.27

CI 400 kGy 61.68

CI 500 kGy 60.88

tallinity Index (%)3

8

0

5

7

8

8

Crystallite Size5.68

8.93

9.01

9.21

8.85

9.30

9.22

e (nm)

TabOPEFslight takingsizes o

Fig

Thrcontai

ble 2 shows thB. The increaseincrease in the

g place [22, 23] of treated OPEF

g. 2. FT-IR Spectra

ree componentsining functional

hat the crystallie of crystallinitydegree of crystand the remov

FBs also increas

of Untreated OPEF

s of biomass conl groups observe

inity index of y index in OPEFallinity after treal of the amorp

se compared to O

FB (a) and (b) CI 10

nsisting of alkeed, e.g., OH, C=

treated OPEFBFBs treated caneatment by chemphous fraction (hOPEFB raw ma

00 kGy; (c) CI 200 k

ene, esters, arom=O, C–O–C, an

Bs increase sign be explained frmical and chemihemicellulose a

aterial.

gnificantly comfrom the XRD pical-irradiation and lignin). Bes

mpared to untrepattern. There w

due to crosslinksides, the crysta

ated was a king allite

kGy; (d) CI 300 kGGy; (e) CI 400 kGy aand (f) CI 500 kGy..

matics, ketone annd C–O–(H). Fi

nd alcohol, withig. 2 shows that

h different oxygt the most obser

gen-rved

200 Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204

peaks in the spectrum originate from -OH stretching vibration (3100-3800 cm-1) and CH2 and CH3 asymmetric and symmetric stretching vibrations (2800-3000 cm-1). These vibrations were expected from hemicellulose, cellulose, and lignin. Intense peaks in the region 1600-1700 cm-1 originate from the stretching mode of carbonyls mainly ketones and esters [22].

Fig. 3-5 shows the SEM micrograph of both untreated and treated OPEFB. The aim of the pretreatment is to change the morphology and crystalinity of raw materials. As can be seen from the SEM micrograph at 20 micrometer scale, it is clear that there are changes in their morphology before and after pretreatment process. SEM micrograph of treated OPEFB both by NaOH 10% and NaOH 10%-irradiation is different with SEM micrograph of OPEFB untreated. Before treatment, OPEFB has a solid, intact, rough and rigid structure but after treatment, OPEFB’s structure becomes brittle, and flaky. The effect of irradiation is to decrease intra and intermolecular ordering in cellulose, due to the breakdown of the system of intermolecular hydrogen bonds and to chemical transformations of the polymer. Under exposure to radiation, cellulose macromolecules undergo scission and the content of fragments with a low degree of polymerization gradually increases.

SEM micrograph of OPEFB untreated in Fig. 3 shows that there are cuticle and fiber parts. However, after NaOH pretreatment method, OPEFB decayed. This suggested that cuticles part have been degraded and removed then dominated only by fiber parts as shown in Fig. 4. Combining chemical and irradiation pretreatment method made OPEFB to be pulp.

Fig. 3. SEM micrograph of OPEFB untreated.

Fig. 4. SEM micrograph of OPEFB-C treated by chemical NaOH10 %.

Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204 201

Fig. 5. SEM micrograph of OPEFB-CI(chemical-irradiation) 500 kGy.

The compositional analysis of OPEFB untreated and treated measured by EDX was shown in Fig. 6-8.

Fig. 6. EDX of OPEFB untreated.

202 Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204

Fig. 7. EDX of OPEFB-C treated by chemical NaOH10 %.

Fig. 8. EDX of OPEFB-CI (chemical-irradiation) 500 kGy.

EDX profiles of both untreated and treated OPEFB show that they had carbon and oxygen in a large weight percentage, while the percentage of the potassium, chlorine, calcium, and silicon is small as shown in detail in Table 3.

Table 3 shows that both of untreated and treated OPEFB were predominantly composed of carbon and oxygen. In OPEFB untreated, the carbon content is higher while the oxygen content is lower than OPEFB treated. Pretreatment

Anis Kristiani et al. / Energy Procedia 68 ( 2015 ) 195 – 204 203

method aims to reduce the lignin content and increase the cellulose content. Lignin has more carbon and less oxygen than cellulose. It is clear that the percentage of carbon decrease while oxygen increase after treated both of NaOH and NaOH-irradiation.

Table 3. EDX analysis result of untreated and treated OPEFB

Sample Carbon (% wt) Oxygen (%wt)

OPEFB untreated 50.57 43.62

OPEFB-C 49.64 49.70

OPEFB-CI 500 kGy 46.03 50.75

4. Conclusion

Pretreatment process of OPEFB by combining chemical and irradiation method give effect for decreasing the lignin content and increasing the cellulose content. While, the OPEFB’s structure also change in term of their crystallinity index, crystallite size and morphology. OPEFB treated by combining chemical and irradiation pretreatment method gave better properties for hydrolysis process to produce bioethanol.

Acknowledgements

This work was fully supported by the State of Ministry Research and Technology, Government of Indonesia.

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