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Chapter 3
Upgrading of Oil Palm Empty Fruit Bunch
to Value-Added Products

Mustakimah Mohamed, Suzana Yusup, Wahyudiono, Siti Machmudah,

Motonobu Goto, and Yoshimitsu Uemura

Contents
3.1 Oil Palm Industry in Malaysia........................................................................................... 64
3.2 Waste to Value-Added Product.......................................................................................... 66
3.3 Conversion of Oil Palm Empty Fruit Bunch to Bio-Oil via Supercritical
Fluid Extraction.................................................................................................................. 70
3.3.1 Preparation of Raw Material.................................................................................. 71
3.3.2 Extraction Process.................................................................................................. 71
3.3.3 Gas Chromatography Mass Spectrometer Analysis............................................... 73
3.3.4 Determination of Yield........................................................................................... 73
3.3.5 Analysis of Chemical Composition........................................................................ 73
3.4 Effect of Extraction Temperature....................................................................................... 73
3.5 Effect of CO2 Flow Rate.................................................................................................... 75
3.6 Conclusion......................................................................................................................... 76
References................................................................................................................................... 77

M. Mohamed (*)
MOR-Green Technology, Universiti Teknologi PETRONAS,
31750 Bandar Seri Iskandar, Perak, Malaysia
e-mail: mustakimah.mohamed@petronas.com.my
S. Yusup • Y. Uemura
Biomass Processing Laboratory, Center of Biofuel & Biochemical Research, MOR-Green
Technology, Universiti Teknologi PETRONAS, 31750 Bandar Seri Iskandar, Perak, Malaysia
e-mail: drsuzana_yusuf@petronas.com.my
Wahyudiono • M. Goto
Chemical Engineering Department, Nagoya University, Furu-cho, Chikusa-ku,
464-8603 Nagoya, Japan
S. Machmudah
Chemical Engineering Department, Sepuluh Nopember Institute of Technology,
Kampus ITS Keputih Sukolilo, Surabaya 60111, Indonesia

K.R. Hakeem et al. (eds.), Biomass and Bioenergy: Applications, 63

DOI 10.1007/978-3-319-07578-5_3, © Springer International Publishing Switzerland 2014
64 M. Mohamed et al.

Abstract As the second largest producer of palm oil in the world, Malaysia
­generates a substantial amount of oil palm biomass as agricultural wastes in the
forms of empty fruit bunches, shell and fiber, fronds, leaves, and trunks. This biomass
feedstock has long been identified as a sustainable source of renewable energy which
could reduce the dependency on fossil fuels as the main source of the energy supply
and thus lead to reduction of greenhouse gases emission. This chapter highlights the
application of oil palm biomass as value-added product and specifically demon-
strates the capability of empty fruit bunch as renewable source in generating bio-oil
which later could be upgraded as biofuel. Green extraction technique known as
supercritical fluid extraction using supercritical CO2 (SC-CO2) was implemented in
this study. Effects of two extraction conditions were investigated which includes
temperature (60–80 °C) and CO2 flow rate (3–6 mL/min). The extraction was con-
ducted for 2 h using 10 g of OPEFB within particle size 0.15 mm. The crude bio-oil
obtained in this study was diluted in 10 mL dichloromethane (DCM) for analysis using
gas chromatography-mass spectrometry (GC-MS). Hexadecanoic acid (palmitic
acid, C16), dodecanoic acid 1, 2, 3-propanetriyl ester (glycerol trilaurate, C39), and
6 octadecanoic acid (stearic acid, C18:0) were identified as the major compounds.

Keywords Bio-oil • Oil palm empty fruit bunch • Supercritical CO2 • Palmitic acid
(C16) • Glycerol trilaurate (C39) • Stearic acid (C18:0)

3.1 Oil Palm Industry in Malaysia

Malaysia is a country located in south east of Asia experiencing tropical climate which
is suitable for growing of oil palm. The seed which is originated from West Africa was
introduced by British in early 1871 and its first commercial plantation is in 1917 at
Tennamaran Estate of Selangor (Basiron and Weng 2004). Today, the plantation cov-
ers 5 million ha of land in Malaysia which make the country as one of the largest
exporters of palm oil in the world. Figure 3.1 indicates the production of crude palm
oil (CPO) from peninsular Malaysia from 2004 until 2011. The production is rela-
tively kept increasing which indicates the stability and sustainability of the sector.
The oil palm trees that have been planted in Malaysia are mainly from the type
of tenera, which is the hybrid seed of dura and pisifera. The ripe oil palm fruit is
reddish in colour which grows in large bunches. The fruit is made up of mesocarp
fiber layers that enclosed the palm kernel and most of the oil is extracted from both
parts, known as CPO and crude palm kernel oil (CPKO) (Sumathi et al. 2008). It is
able to bear fruits after 30 months and produce 4–5 tons of CPO each hectare every
year. The tree could be productive for 20–30 years and only require 0.26 ha of land
to produce 1 ton of oil compared to soybean, sunflower and rapeseed which required
2.22, 2, and 1.52 ha of land, respectively (MPOC 2012). Sumathi et al. (2008) state
that oil palm is energy-efficient crop since it requires less energy to produce 1 ton
of oil. Figure 3.2 illustrates the ratio of energy output to input for several commer-
cially grown oil crops which indicates that oil palm output is three times greater
than the others (Sumathi et al. 2008).
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 65

Fig. 3.1 Production of crude palm oil from peninsular Malaysia (Malaysian Palm Oil Council 2012)

Fig. 3.2 Input and output energy consumption of several biomass (Sumathi et al. 2008)

Figure 3.2 demonstrates the staggering amount of waste generated which cur-
rently is still underutilized. For instance, it is estimated that 37 million tons of oil
palm biomass had been generated in 2008 which consisted of 22 % OPEFB, 13.5 %
fruit press fiber (FPF), and 5.5 % palm kernel shell (PKS) (Mazaheri 2010; MPOC
2012). Figure 3.3 illustrates the general mass balance involved in palm oil mill
which indicates that pure oil only contributes 21 % of a fresh fruit bunch and left
almost 50 % waste including OPEFB as the biomass (Mazaheri 2010; Umikalsom
et al. 1997; MPOC 2012). Yusoff (2006) states that OPEFB is one of the main by-­
products and wastes produced from the mill. As described in Table 3.1, EFB is the
highest amount of biomass generated in the mills compared to fiber and shell in
1997 for an estimated plantation hectare of 148 palms/ha (Yusoff 2006).
66 M. Mohamed et al.

Fig. 3.3 Composition chart of palm oil mill (Mazaheri 2010; Umikalsom et al. 1997; MPOC 2012)

Table 3.1 Amount of Biomass Quantity (million tons)

biomass generated by
Empty fruit bunch 10.6
palm oil mills in 1997
(Yusoff 2006) Fiber 6.6
Shell 2.7
Pome 32

3.2 Waste to Value-Added Product

Renewable energy is environmental friendly since it does not emit CO, CO2, SOx,
NOx, and particulates during combustion compared to fossil fuels including oil, gas,
and coal (Tan et al. 2009; Sulaiman et al. 2011). It has been one of the main agenda
for Malaysian Government although the country is rich with primary energy
resources. Utilization of renewable energy resources, particularly oil palm wastes,
has been increased since it is a strategically sustainable energy resources and able to
reduce agriculture disposal problem in an environmental friendly manner (Sulaiman
et al. 2011). In 2006, biodiesel which is a blend of palm oil (5 %) and petroleum oil
(95 %) was promoted through National Biofuel Policy. The policy ensures the qual-
ity of the biodiesel to meet the industrial standard and to support biodiesel pumps at
selected stations. It also encourages the establishment of biodiesel plants in
Malaysia. In addition, Malaysia has implemented National Renewable Energy
Policy and Action Plan in 2010 which is aimed to branch the utilization of local
renewable energy resources towards electricity supply and socio-economic devel-
opment (APEC 2013). Figure 3.4 represents several major crops that have been used
as the natural renewable sources for respective biofuels.
Oil palm biomass is a promising renewable energy source due to rising price of
crude petroleum. Therefore, converting oil palm biomass into biofuel is not
only able to reduce the petrol crisis, but also helps to protect the environment by
reducing CO2 emission (Shuit et al. 2009). According to Sulaiman et al. (2011)
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 67

Fig. 3.4 Crops for biofuels production (Demirbas 2007)

oil palms waste has been used to produce steam for mills and electricity generation.
It was reported that more than 300 palm oil mills are operating using self-generated
electricity using oil palm waste which is also sufficient for surrounding remote areas
(Sulaiman et al. 2011). Generally, biomass is a lignocellulosic material which is
made up of hemicellulose, cellulose, lignin, and minor amount of extractives.
Biomass material is eligible to be converted to energy by applying thermochemical
or biological processes (Demirbas 2007). Tan et al. (2009) mentioned that liquid
fuel such as bio-diesel is one of the global extensively researched renewable energy
resources. Biodiesel is mono-alkyl esters of long-chain fatty acids which is derived
from trans-esterification reaction of triglycerides from the feedstock presence of
alcohol, forming esters and glycerol (Tan et al. 2009).
By implementing several conversion technologies as shown in Fig. 3.5, biomass
is able to be converted into biofuel. One of the most interesting thermochemical
conversion technologies is biomass gasification due to its high combustion effi-
ciency compared to pyrolysis. Gasification is believed to cause the carbon to become
less reactive and forming stable chemical structure which consequently increased
the activation energy as the conversion increased (Demirbas 2007). Biomass
­gasification occurs at higher temperature than pyrolysis and is able to produce
68 M. Mohamed et al.

Fig. 3.5 Conversion technologies applicable to biomass (Demirbas 2007)

­mixture gases including H2 at 6–6.5 % concentration (Demirbas 2007). These gaseous

products are able to be converted into clean fuel gases or known as biofuel (Demirbas
2007). Oil palm biomass is able to produce many types of biofuel including
­bio-­ethanol, bio-methanol, bio-briquettes, hydrogen gas, and pyrolysis oil (Shuit
et al. 2009).
It is well known that biofuel is able to reduce the emission of CO2. For instance,
biofuels such as bioethanol, biomethanol, and biodiesel can help reduce the emission
of this greenhouse gas by almost 80 % compared to petroleum diesel (Shuit et al.
2009). Shuit et al. (2009) also claimed that CO2 emission was reduced by 1,040 thou-
sand tons when diesel was replaced with biogas to generate electricity. Empty fruit
bunch, mesocarp fibers, and palm kernel are the main oil palm wastes that have been
used to provide steam for electricity generation. Currently, Malaysia has 300 palm oil
mills which self-generated electricity by using these wastes and this figure is increas-
ing. Small Renewable Energy Program (SREP) has been launched in 2004 and 62
projects have been approved which include 25 projects that are implementing oil
palm biomass as the fuel source (Shuit et al. 2009). PKS also has been applied as fuel
in the boiler of some cements company which is believed to reduce CO2 emission by
366.26 thousand tons in 2006 (Shuit et al. 2009; Sulaiman et al. 2011). Therefore,
biomass is an option for renewable energy which can reduce the greenhouse effect
compared to current fossil fuel (Sulaiman et al. 2011; Shuit et al. 2009).
Oil palm waste is also able to generate hydrogen, which currently has been
regarded as synthetic fuel obtained from fossil fuels (Sulaiman et al. 2011). Via
gasification, various parts of oil palm such as EFB fiber, shell, trunk, and frond can
be converted into biohydrogen which is diversely applicable in transportation or
power generation. Hydrogen as transportation fuel is efficient for the engine and
environment due to its zero emission (Sulaiman et al. 2011). Besides, oil palm
­biomass is also rich in sugar and lignocellulose which makes it a perfect candidate
for production of bio-methanol and bio-ethanol. Bio-methanol has high octane rat-
ing which makes it suitable for spark ignition in the engine (Shuit et al. 2009). It is
prominently converted through gasification which involves vaporization of biomass
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 69

Fig. 3.6 Cost of producing various fuels in Malaysia (Shuit et al. 2009)

at high temperature and removing impurities from the hot gas before being c­ onverted
to bio-methanol using catalyst (Shuit et al. 2009). Inversely, bio-ethanol is produced
via fermentation process and is mostly applied as fuel additive to reduce emission
of CO and smog. According to Shuit et al. (2009), xylose from EFB is produced via
acid hydrolysis and can further be utilized as second generation bio-­ethanol. Brazil,
US, and European market have provided the flexible-fuel vehicle which can run on
mixtures of gasoline and up to 85 % bio-ethanol (Shuit et al. 2009). Figure 3.6 com-
pares the production price of various fuels in Malaysia. About 46 % of the cost for
bio-ethanol production is due to the feedstock which could be further reduced
throughout the year since the feedstock is abundantly available and cheap (Shuit
et al. 2009). Therefore, biofuel is achievable to replace the fossil fuel.
Bio-oil is also one of the products from biomass conversion. The term bio-oil
refers to liquid fuels made from biomass material including agricultural crops,
municipal waste, and agricultural and forestry by-product via bio-chemical or
­thermochemical processes (Demirbas 2007). Bio-oil normally has pungent odour, is
brown in colour, and contains fragments of cellulose, hemicelluloses, lignin, and
extractive (Sulaiman et al. 2011). Bio-oil is also known to be high-density oxygen-
ated liquid and can be used to run diesel engines partially in blend, turbines, or
boilers (Sulaiman et al. 2011; Demirbas 2007). The yield of bio-oil is about 70 and
15 % charat temperatures around 500 °C together with short vapor residence times
(Sulaiman et al. 2011). Bio-oil is considered as relevant technologies in both
­developing and industrialized countries due to energy security reasons, environ-
mental concerns, foreign exchange savings, and rural sector of socio-economic
issues (Demirbas 2007).
70 M. Mohamed et al.

3.3 C
 onversion of Oil Palm Empty Fruit Bunch to Bio-Oil
via Supercritical Fluid Extraction

The liquid fuel or commonly known as bio-oil could be further upgraded to other
value-added compounds such as gasoline and diesel. Recently, it was reported that
a promising route to convert biomass to liquid fuel is via supercritical fluid extrac-
tion (SFE). It is one of the thermochemical reaction techniques that can be applied
to extract bio-oil from biomass other than combustion, pyrolysis, and gasification
(Qian et al. 2007; Demirbass 2000; Xu et al 2011; Naik et al. 2010; Minowa et al.
1998). The technique is able to obtain liquid fuels with low molecular weight from
the biomass by converting the solid compounds under supercritical fluid conditions.
Compared to conventional fast pyrolysis method, supercritical fluid liquefaction is
advantageous since drying the feedstock is not necessary and therefore it is simpler
and attractive from the perspective of energy consumption (Qian et al. 2007). This
method is also a promising technique since it implements nontoxic, non-flammable,
cheap, and readily available fluid as the solvent for extraction (Molero et al. 1996).
For instance, CO2 require low temperature (31.1 °C) and low pressure (73.8 atm) to
reach the supercritical condition. Supercritical fluid is defined as fluid formed at
conditions above the critical properties for that particular solvent. During supercriti-
cal conditions, a fluid is neither liquid nor gas and it has unique properties in
between liquid and gas. For instance, supercritical fluid possesses liquid-like densi-
ties, but has high diffusivity and compressibility similar to gas. Therefore, super-
critical fluid has enhanced solid solubility compared to liquid or gas solvent. Slight
changes in temperature or pressure can cause big alteration towards the fluids prop-
erties such as density, solubility, or diffusivity (Herrero et al. 2006). At supercritical
conditions, the fluid has low viscosity and relatively high diffusivity in which it is
able to diffuse easily within the extraction matters (Herrero et al. 2006). Thus, by
modifying the extraction condition such as pressure, temperature, and CO2 flow
rate, the solubility strength of the fluid can be amended and higher extraction yield
could be obtained.
Molero et al. (1996) extracted grape seed oil (GSO) using SC-CO2 and found that
the yield of GSO is higher compared to the extraction using liquid CO2. Using the
same operating condition, Molero et al. (1996) obtained same yield of GSO to
those conventional extraction using hexane. Yet, the extraction using SC-CO2 is
more preferable and economical since it is solvent-free (Molero et al. 1996).
In addition, Patel et al. (2006) claimed that the quality of the obtained oil using
SC-CO2 is better compared to the oil that has been obtained using normal thermal
route. Till date, there are limited studies of SFE using SC-CO2 that have been con-
ducted on biomass to extract bio-oil. Mostly, the SFE is implemented in food and
pharmaceutical industries. Therefore, this chapter provides an insight in extracting
bio-oil from oil palm biomass by implementing SFE using SC-CO2 under various
extraction conditions.
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 71

Fig. 3.7 Physical appearance of OPEFB (a) before extraction, and (b) The residue looked dry,
lighter and turned into more fine particles after the extraction was conducted

3.3.1 Preparation of Raw Material

Figure 3.7 illustrates the changes in physical appearance of OPEFB before and after the
extraction. The biomass was collected from nearby local oil palm plantation. It was
cleaned by removing the sand and air dried for one day. The biomass was collected
from nearby local oil palm plantation. It was cleaned by removing the sand and air
dried for one day. The biomass was ground and sieved into the intended particle sizes,
which in this case was 0.15 mm. To keep the sample fresh, it was kept in the refrigera-
tor (6 °C) prior to extraction.

3.3.2 Extraction Process

Figure 3.8 illustrates the SFE SC-CO2 extraction system that has been applied in
this study. A 10 g of the sample was filled into the extractor (TharDesigns, 25 mL)
and placed in the oven (EYELA WFO-400). Liquid CO2 is supplied from the gas
cylinder with purity of 99 % and the flow rate was adjusted using CO2 delivery
pump (Jasco). The gas passed through the chiller to liquefy the stream before enter-
ing the oven which was preheated at the desired temperature. A back pressure regu-
lator was used to manually regulate the extraction pressure. The extraction took
place for 120 min and the extracted bio-oil was collected in the sample bottle. The
wet CO2 gas that has been released from extractor was measured using wet gas
meter before vented. Table 3.2 indicates the extraction conditions and the manipu-
lated extraction parameters in this study.
The extracted bio-oil obtained during the extraction was in waxy state. It was
weighted and diluted in 10 mL of DCM prior to analysis using GC-MS. Figure 3.9
demonstrates the changes in physical appearance of the extracted bio-oil obtained
during the extraction and after being diluted in the solvent.
72 M. Mohamed et al.

Fig. 3.8 Set-up of SFE system in GOTO Laboratory, Nagoya University, Japan

Table 3.2 Extraction conditions of the manipulated parameters

Varied parameters Pressure (MPa) Temperature (°C) Flowrate (mL/min)
Temperature 40 60 5
70
80
CO2 flow rate 40 70 3
4
6

Fig. 3.9 Physical appearance of (a) waxy bio-oil (b) diluted bio-oil in DCM
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 73

Table 3.3 Composition Component Composition (%)

of three main components
Hemicellulose 26.9
in biomass
Alpha-cellulose 26.6
Lignin 18.6

3.3.3 Gas Chromatography Mass Spectrometer Analysis

Gas chromatography mass spectrometer (GCMS) (Agilent) is used to analyze the

presence of compounds and their composition in the extracted bio-oil. Helium with
flow rate of 3 mL/min was the carrier gas and split less column HP-5MS is used to
analyze the components in the sample using NIST Library. The column temperature
was kept constant at 150 °C for 3 min, then ramp to 320 °C for 10 min with heating
rate of 5 °C/min.

3.3.4 Determination of Yield

Yield of bio-oil is expressed as the yield of crude extracts with respect to the
­biomass. Therefore, weight of feed bio mass and extracted bio-oil was recorded.
The expression applied was quoted in Eq. 3.1.

m extract
Yield ( wt% ) = ´ 100. (3.1)
m biomass

mextract is mass of the extract (g); and mbiomass is mass of the biomass (g)

3.3.5 Analysis of Chemical Composition

Table 3.3 describes the amount of main components in the biomass OPEFB. Cellulose,
hemicellulose, and lignin are the major components that made up the biomass.
Cellulose and hemicellulose are the compounds which are mainly involved and
­converted into bio-oil during the extraction compared to lignin. Therefore, high com-
position of these components reflects that OPEFB is a good source to obtain bio-oil.

3.4 Effect of Extraction Temperature

Near to critical state, fluid density is highly sensitive to temperature because a slight
increment in temperature can lead to a large decrease in fluid density and solubility
(Bimakr et al. 2009). It will accelerate mass transfer and improve extraction yield.
74 M. Mohamed et al.

Fig. 3.10 Yield of bio-oil obtained under different extraction temperature

As indicated in Fig. 3.10, a yield at 17 wt% was maximized at temperature of 80 °C

compared to 14.8 wt% at the lowest temperature of 60 °C. According to Machmudah
et al. (2007), higher temperature contributed to the decomposition of cell walls, and
as a result oil extracted increased. Leo et al. (2005) also claimed that high tempera-
ture enhanced the oil solubility in the CO2 fluid due to lower solvent strength since
the fluid density tends to decrease.
Effect of extraction temperature on composition of major compounds was
­demonstrated in Fig. 3.11. Extraction temperature was varied from 60 to 80 °C.
Composition of glycerol trilaurate (C39) was identified to be maximized at lowest
extraction temperature of 60 °C. But, the concentration kept decreased with an
increase in temperature. Inversely, composition of palmitic acid (C16) increased with
respect to temperature from 16.63 to 24.41 %. Concentration of stearic acid (C18)
decreased from 12.05 to 11.47 % when the temperature was increased but later
increased at temperature 80 °C.
According to Zaidul et al. (2007), the extraction of triglyceride in the fatty acid
constituents is highly dependent on solubility of the fatty acids in the SC-CO2.
It depends on the length of hydrocarbon chain, functional group, extraction pres-
sure, and temperature (Zaidul et al. 2007). In this case glycerol trilaurate (C39)
­composition decreased once the temperature increased from 60 to 80 °C. The same
behavior was observed by Medina-Gonzalez et al. (2012) who studied the phase
equilibrium of SC-CO2 with respect to glycerol. The finding indicates that in CO2-
rich phase, glycerol has low solubility in CO2 as the temperature increased (Medina-
Gonzalez et al. 2012). Thus, the mole fraction of glycerol trilaurate (C39) is decreased
as illustrated in Fig. 3.11.
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 75

Fig. 3.11 Concentration of three major compounds in the extract at different reaction temperature

3.5 Effect of CO2 Flow Rate

Fluid flow rate is also a factor that influences extraction efficiency since it deter-
mines solvent to solid ratio (Patel et al. 2006). It was observed that total liquid yield
increased once flow rate of fluid was increased (Patel et al. 2006). When higher flow
rate of CO2 was supplied into the extraction cell, higher yield of bio oil was recov-
ered due to better mass transfer. Figure 3.12 described that yield increased once
flow rate was increased from 3 to 4 mL/min before it decreased at 6 mL/min.
Rahman et al. (2012) mentioned that mass transfer can be enhanced once the flow
rate is increased since the extracted oil will saturate to exit the solvent (SC-CO2),
hence maximize the extraction. However, Rahman et al. (2012) claimed that “any
additional flow rate” cause imbalance of equilibrium condition causing the solvent
to be unsaturated and reduce the extraction efficiency. This argument applies for the
observed behavior in Fig. 3.12.
Effect of solvent amount on the concentration of major compound is illustrated
in Fig. 3.13. Flow rate of CO2 was varied which signify the amount of CO2 fluid
presence for the extraction. At all flow rates, glycerol trilaurate (C39) concentration
was the highest while stearic acid (C18) was the lowest. Composition of glycerol
trilaurate (C39) and stearic acid (C18) increased with respect to the fluid flow rate.
However, concentration of palmitic acid (C16) decreased from 16.5 to 13.35 % when
the flow rate was increased to 4 ml/min and later increased to 14.56 % once flow rate
was increased to 6 mL/min.
76 M. Mohamed et al.

Fig. 3.12 Yield of bio-oil obtained under different CO2 flow rate

Fig. 3.13 Concentration of three major compounds in the extract at different CO2 flow rate

3.6 Conclusion

Mass production of oil palm biomass illustrates the capability of this agricultural
waste as the reliable and sustainable energy resource. The properties of oil palm
biomass which is made up of lignocellulosic material enable the waste to be con-
verted into various types of biofuel using many conversion techniques. In this case,
empty fruit bunch demonstrated its capability to be converted into bio-oil via one of
3 Upgrading of Oil Palm Empty Fruit Bunch to Value-Added Products 77

the thermochemical promising route, SFE SC-CO2. While studying the effect of
temperature, the highest yield obtained was 17 % at the highest extraction tempera-
ture which is 80 °C. Palmitic acid (C16) and stearic acid (C18:0) composition increased
with respect to temperature increase. Further, the highest yield was obtained at flow
rate of 4 mL/min, which is 23.2 %, and the composition of glycerol trilaurate (C39)
is at the maximum at these conditions compared to palmitic acid (C16) and stearic
acid (C18:0).

Acknowledgment Thanks to Yayasan Universiti Teknologi PETRONAS—Fundamental Research

Grants and Universiti Teknologi PETRONAS for the financial assistance and support provided to
undertake the work.

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Chapter 4
Bioenergy Derived from Electrochemically
Active Biofilms

Mohammad Mansoob Khan

Contents
4.1 Introduction........................................................................................................................ 80
4.2 Applications of EABs as a Bioenergy Source.................................................................... 82
4.2.1 Bioelectricity Production....................................................................................... 82
4.2.2 Synthesis of Metal Nanoparticles.......................................................................... 83
4.2.3 Synthesis of Metal-Metal Oxide Nanocomposites................................................ 84
4.2.4 Modifications of Metal Oxides.............................................................................. 85
4.2.5 Bio-hydrogen Production....................................................................................... 85
4.2.6 Environmental Remediation.................................................................................. 86
References................................................................................................................................... 86

Abstract Microorganisms (bacteria) naturally form biofilms on solid surfaces.

Biofilms can be found in a variety of natural sites, such as sea water sediments,
soils, and a range of wastewaters, such as municipal, dye, agricultural, and indus-
trial wastewaters. The biofilms are normally dangerous to human health due to their
inherited robustness. Electrochemically active biofilms (EABs) generated by elec-
trochemically active microorganisms (EAMs) have potential applications in bioen-
ergy production, green chemical synthesis, bioremediation, bio-corrosion mitigation,
and biosensor development. EABs have attracted considerable attention in bioelec-
trochemical systems, such as microbial fuel cells (MFCs) and microbial electrolysis
cells, where they act as living bio-anode or bio-cathode catalysts. EABs are an
anode material in MFCs that generate an excess of electrons and protons by biologi-
cally oxidizing substrates, such as sodium acetate or organic waste, and the flow of
these electrons produces significant amounts of electricity. Recently, it was found
that EABs can be used as a biogenic-reducing tool to synthesize metal nanoparticles

M.M. Khan (*)

School of Chemical Engineering, Yeungnam University, Geongsan-si, South Korea
e-mail: mmansoobkhan@yahoo.com

K.R. Hakeem et al. (eds.), Biomass and Bioenergy: Applications, 79

DOI 10.1007/978-3-319-07578-5_4, © Springer International Publishing Switzerland 2014
80 M.M. Khan

and metal–metal oxide nanocomposites. The EAB-mediated synthesis of metal

nanoparticles and metal–metal oxide nanocomposites is expected to provide a new
avenue for the greener synthesis of nanomaterials with high efficiency than other
synthetic procedures. It was also found that EABs could be effectively used as a tool
to provide electrons and protons by biologically decomposing acetate which is later
used in the presence of a suitable catalyst for the bio-hydrogen production. These
nanoparticles as well as nanocomposites syntheses and bio-hydrogen production
takes place in water at 30 °C and does not involve any energy input which make
these approaches highly efficient. These findings show that EAB is a fascinating
biogenic tool for MFCs, nanomaterials synthesis, bioremediation, and bio-hydrogen
production.

Keywords Electrochemically active microorganisms • Electrochemically active

biofilms • Biogenic tool • Microbial fuel cells • Nanomaterials synthesis • Bio-
hydrogen production

4.1 Introduction

In general, microorganisms naturally form biofilms on solid surfaces for their mutual
benefits such as protection from environmental strains caused by contaminants,
nutritional depletion, or imbalances. Biofilms can be found in a variety of natural
sites, such as sea or river water sediments, soils, and a range of wastewaters, such as
domestic, municipal, dye, agricultural, and industrial wastewaters (Borole et al.
2011; Babauta et al. 2012). The biofilms are normally hazardous to human and ani-
mal health due to their inherited sturdiness and infectious nature. On the other hand,
recent studies suggested that electrochemically active biofilms (EABs) (Fig. 4.1)
generated by electrically active microorganisms (EAMs) have properties and poten-
tial that can be utilized to catalyze or control the electrochemical reactions in a range
of applications, such as bioenergy production, biogenic chemical synthesis, bio-
remediation, bio-corrosion mitigation, and bio-sensor development (Borole et al.
2011; Babauta et al. 2012; Erable et al. 2010; Rittmann et al. 2008; Halan et al. 2012;
Kalathil et al. 2013a). EABs have attracted considerable attention in bioelectro-
chemical systems (BESs), such as microbial electrolysis cells (MECs) and microbial
fuel cells (MFCs), where they act as living bio-anode or bio-cathode catalysts
(Kalathil et al. 2013a). EABs are an anode material in MFCs that generate an excess
of electrons and protons by biologically oxidizing substrates, such as sodium acetate
or other organic wastes. The flow of these biologically generated electrons produces
significant amounts of electricity, whereas the produced protons (H+) moves to the
cathodic chamber of MFC where it may be reduced by electrons to H2 gas in the
presence of a suitable catalyst such as gold or oxidized to H2O (Dulon et al. 2007;
Logan et al. 2005; Khan et al. 2014). The discoveries of EAMs forming biofilms
which are able to transfer directly electrons on electrode surfaces have boosted the
development of MFCs. The mechanisms of electron transfer have been demonstrated
to be either direct, involving membrane-bound cytochromes for instance, or through
4 Bioenergy Derived from Electrochemically Active Biofilms 81

Fig. 4.1 Scanning electron microscopy images of mixed culture EABs showing different types
of bacteria on biofilm

Fig. 4.2 Applications of mixed culture EABs for various possible applications

natural electron mediators that are produced by the microorganisms and remain
entrapped in the biofilm (Bond et al. 2002). The involvement of conductive pili in
electron transfer has also been demonstrated (Babauta et al. 2012; Erable et al. 2010;
Rittmann et al. 2008; Halan et al. 2012). MFCs utilize microbial EABs as catalysts
to convert the chemical energy contained in a large variety of organic compounds
directly into electricity and various other products such as H2O, H2, etc. MFCs pro-
duce a lower power density than fuel cells but the increasing interest in sustainable
energy sources is promoting intense research leading to fast improvements.
Recently, it was found that EABs can be directly used as a biogenic tool (Fig. 4.2)
to synthesize metal nanoparticles and metal–metal oxide nanocomposites (Kalathil
et al. 2011, 2012; Khan et al. 2012, 2013a, b; Ansari et al. 2013a). The EAB-­
mediated synthesis of metal nanoparticles and metal–metal oxide nanocomposites
is expected to provide a new way for the greener synthesis of nanomaterials with
comparatively high efficiency than the other synthetic procedures. It was also estab-
lished that EABs could be effectively used as a tool to provide electrons and protons
by biologically decomposing acetate which is later used in the presence of a suit-
able catalyst for the bio-hydrogen production (Khan et al. 2013c, 2014; Kalathil
et al. 2013b). Further, it was also found that EABs could be exploited to narrow the
band gap of metal oxides such as TiO2, ZnO, SnO2, and CeO2 (Kalathil et al. 2013a,
82 M.M. Khan

b, c; Ansari et al. 2013b, 2014). These EAB-mediated nanoparticles as well as

nanocomposites syntheses, bio-hydrogen production, and metal oxide modification
processes do not involve any external energy input (energy supply) which makes
these methodologies highly efficient and useful. These findings show that EAB is a
fascinating biogenic tool for MFCs, nanomaterials syntheses, bioremediation, and
bio-­hydrogen production.

4.2 Applications of EABs as a Bioenergy Source

The chemical energy stored in the bonds of organic compounds (such as acetate) is
utilized using EAMs which oxidizes organic compounds into harmless by-products
such as protons, electrons, and CO2 (Kim et al. 2012; Logan and Rabaey 2012; Pant
et al. 2012; Han et al. 2013; Rozendal et al. 2009). Recently, it was established by
many researchers that these electrons and protons can be used for various purposes in
MFCs such as electricity generation, CO reduction, etc. (Kim et al. 2012; Logan and
Rabaey 2012; Pant et al. 2012). Very recently, it was also reported that nanomaterials
such as metal nanoparticles and metal-metal oxide nanocomposites can be in-situ
synthesized successfully using EABs (Kalathil et al. 2011, 2012; Khan et al. 2012,
2013a, b; Ansari et al. 2013a, 2014). Following are the few examples which show that
how the energy stored in the organic compounds is biologically exploited for various
green synthesis, environmental remediation, bioelectricity, and bio-­hydrogen produc-
tion. In general, when one mole of acetate is biologically decomposed by EABs, it
gives two moles of HCO3−, nine moles of H+, and eight moles of electrons as shown by
following reaction (Logan and Rabaey 2012; Rozendal et al. 2009; Khan et al. 2014).

CH 3 COO − + 4H 2 O + EABs → 9H + + 8e − + 2HCO3 − ……. (4.1)

4.2.1 Bioelectricity Production

EABs are used as living bioanode catalysts in MFCs to generate electricity (Kim et al.
2012; Logan and Rabaey 2012; Pant et al. 2012; Han et al. 2013). The EAB oxidizes
organic substrates, such as acetate to electrons, protons, and CO2 without combustion.
The electrons produced are transferred through an external circuit, whereas the pro-
tons migrate to the cathode via a cation exchange membrane to cathode and react with
oxygen to produce water (Fig. 4.3). The most striking feature of this technology is
that a simultaneous wastewater treatments, nanomaterials synthesis, bio-hydrogen
production, and bioelectricity generation can be achieved without the need of energy
input (Han et al. 2013). Though the produced electricity is not too high, but no energy
input, nanomaterials synthesis, bio-hydrogen production, and wastewater treatment,
makes this approach efficient (Kalathil et al. 2013b; Han et al. 2013).
4 Bioenergy Derived from Electrochemically Active Biofilms 83

Fig. 4.3 Bioelectricity production in MFC using mixed culture EABs

a b
EAB on Stainless steel mesh Microorganisms

Sodium acetate ns
ctro
Ele
Electrons Ag+
+ + Ag0
+ 0 + Ag Cysteine
Au3+ Au + Cysteine Complex
Electrons + + Sodium
(+)AuNPs acetate Cysteine
Cl- ion penetration into
Capped AgNPs
stainless steel mesh
Stainless steel mesh Electrochemically
Active Biofilm

Fig. 4.4 Synthesis of (a) (+)AuNPs, and (b) Cys-AgNPs using EABs

4.2.2 Synthesis of Metal Nanoparticles

Metal nanoparticles such as gold nanoparticles (AuNPs) (Khan et al. 2013c; Kalathil
et al. 2013b), silver nanoparticles (AgNPs) (Kalathil et al. 2011), and cysteine-­
capped silver nanoparticles (cys-AgNPs) (Khan et al. 2012) were reported to be
synthesized by EABs as a reducing tool in the presence of sodium acetate as an
electron donor (Kalathil et al. 2013b; Logan et al. 2005). Here, sodium acetate acts
as carbon source and biologically oxidizes to electrons, protons, and CO2. Respective
precursors were used to synthesize the different metal nanoparticles in the presence
of sodium acetate as a carbon source which provides plenty of electrons for the
reduction of metal ions into zero-valent metal nanoparticles. Figure 4.4a shows the
84 M.M. Khan

Fig. 4.5 Synthesis of Au@TiO2, Ag@TiO2, and Ag@ZnO nanocomposites using EABs

synthesis of AuNPs using EAB formed on stainless steel as a support. Similar

approach was used to synthesize AgNPs (Kalathil et al. 2011). Presence of stainless
steel as a support for EAB enhances the availability of electrons by Cl- penetration
into it (Khan et al. 2013c; Han et al. 2013). Figure 4.4b shows the synthesis of cys-­
AgNPs using EABs and sodium acetate as an electron source (Khan et al. 2012).
The synthesized nanoparticles were used for different applications, for example,
bio-hydrogen production (Khan et al. 2013d) and anti-microbial activity (Khan
et al. 2012).

4.2.3 Synthesis of Metal-Metal Oxide Nanocomposites

Another very interesting use of EABs was to synthesize different types of nanocom-
posites. New reports show the use of EABs as a biogenic tool to synthesize metal–
metal oxides nanocomposites such as Au@TiO2, Ag@TiO2, and Ag@ZnO
nanocomposites in the presence of sodium acetate as a carbon source (Kalathil et al.
2012; Khan et al. 2013a; Ansari et al. 2013a). Figure 4.5 shows a common proposed
mechanism for the synthesis of nanocomposites. Here too, the electrons produced
by the EABs were used for the reduction of the metal ions at the surface of metal
oxides. This leads to the formation and anchoring of metal nanoparticles at the sur-
face of metal oxides. The reported methods are green as the entire synthesis takes
place in water at 30 °C. The advantage of this protocol is that it does not involve any
energy input and the products obtained are quite free from any impurities or by-
products. The synthesized nanocomposites were used for various applications such
as sensing (Khan et al. 2013b), dye degradation (Kalathil et al. 2012; Khan et al.
2013a; Ansari et al. 2013a), etc.
4 Bioenergy Derived from Electrochemically Active Biofilms 85

Fig. 4.6 Modifications of

metal oxides (TiO2, ZnO,
SnO2, and CeO2) using EABs

4.2.4 Modifications of Metal Oxides

Recently another use of EABs was discovered which is highly motivated, i.e., band
gap engineering of metal oxides such as TiO2, ZnO, SnO2, and CeO2. The approach
is quite simple, efficient, and produces the defected metal oxides having reduced
band gap in comparison to pure metal oxides (Kalathil et al. 2013a; Ansari et al.
2013b, 2014). Figure 4.6 shows the proposed mechanism to narrow down the band
gap of the different metal oxides using EAB as a band gap engineer. The EAB pro-
duced electrons and protons interacted with the metal oxides and produced some
defects such as oxygen vacancies, low valent ion formation, etc. (Kalathil et al.
2013a; Ansari et al. 2013b, 2014). The defected metal oxides were used as visible
light active photocatalyst materials for environmental remediation. The band gap-­
narrowed metal oxides were used for several exciting studies and applications such
as visible light-induced photocurrent and dyes degradation of different classes
induced by visible light (Kalathil et al. 2013a; Ansari et al. 2013b, 2014).

4.2.5 Bio-hydrogen Production

The use of EABs seems to be fictions; however, it is a fact and also reported for bio-­
hydrogen production in presence of gold nanoparticles as catalyst and sodium ace-
tate as a carbon source which provides electrons as well as protons. Figure 4.7
shows the proposed mechanism for the bio-hydrogen production. The biologically
produced electrons and protons combine at the surface of AuNPs following the
Volmer-Heyrovsky mechanism (Kalathil et al. 2013c; Brust and Gordillo 2012).
The observed bio-hydrogen production rate was ~105 ± 2 mL/L/day (Khan et al.
2013d). The bio-­ hydrogen production in MFC was also reported and found
~1.5 mL/h (Kalathil et al. 2013c).
86 M.M. Khan

Fig. 4.7 Bio-hydrogen production using EABs in the presence of (+)AuNPs

4.2.6 Environmental Remediation

Recently, it was also reported that EABs could be directly used for the environmen-
tal remediation such as dye (methylene blue) degradation in the presence of suitable
catalyst such as Au@TiO2 (Kalathil et al. 2013d). Here too, the degradation process
does not need any energy which makes it efficient.
In summary, EABs are biogenic tool that is used for various applications such as
nanomaterials synthesis, band gap engineering, bio-hydrogen production, and envi-
ronment remediation. The beauty of EABs is that its use does not need any energy
input and the products obtained are free from impurities. The energy stored in the
organic molecules are released with the help of EABs and used up for various appli-
cations. These approaches show that EABs acts as a fascinating biogenic tool which
is easy to prepare and use.

References

Ansari SA, Khan MM, Ansari MO, Lee J, Cho MH (2013a) Biogenic synthesis, photocatalytic,
and photoelectrochemical performance of Ag-ZnO nanocomposite. J Phys Chem C 117:
27023–27030
Ansari SA, Khan MM, Kalathil S, Nisar A, Lee J, Cho MH (2013b) Oxygen vacancy induced band
gap narrowing of ZnO nanostructures by an electrochemically active biofilm. Nanoscale
5:9238–9246
Ansari SA, Khan MM, Ansari MO, Lee J, Cho MH (2014) Highly photoactive SnO2 nanostruc-
tures engineered by electrochemically active biofilm. New J Chem 38:2462–2469
Babauta J, Renslow R, Lewandowski Z, Beyenal H (2012) Electrochemically active biofilms: facts
and fiction. A review. Biofouling 28:789–812
Bond DR, Holmes DE, Tender LM, Lovely DR (2002) Electrode-reducing microorganisms that
harvest energy from marine sediments. Science 295:483–485
4 Bioenergy Derived from Electrochemically Active Biofilms 87

Borole AP, Reguera G, Ringeisen B, Wang Z, Feng Y, Kim BH (2011) Electroactive biofilms:
­current status and future research needs. Energy Environ Sci 4:4813–4834
Brust M, Gordillo GJ (2012) Electrocatalytic hydrogen redox chemistry on gold nanoparticles.
J Am Chem Soc 134:3318–3321
Dulon S, Parot S, Delia ML, Bergel A (2007) Electroactive biofilms: new means for electrochemistry.
J Appl Electrochem 37:173–179
Erable B, Duteanu NM, Ghangrekar MM, Dumas C, Scott K (2010) Application of electro-active
biofilms. Biofouling 26:57–71
Halan B, Buehler K, Schmid A (2012) Biofilms as living catalysts in continuous chemical synthe-
ses. Trends Biotechnol 30:453–465
Han TH, Khan MM, Kalathil S, Lee J, Cho MH (2013) Simultaneous enhancement of methylene
blue degradation and power generation in a microbial fuel cell by gold nanoparticles. ACS Ind
Eng Chem Res 52:8174–8181
Kalathil S, Lee J, Cho MH (2011) Electrochemically active biofilm-mediated synthesis of silver
nanoparticles in water. Green Chem 13:1482–1485
Kalathil S, Khan MM, Banerjee AN, Lee J, Cho MH (2012) A simple biogenic route to rapid syn-
thesis of Au@TiO2 nanocomposites by electrochemically active biofilms. J Nanopart Res
14:1051–1060
Kalathil S, Khan MM, Ansari SA, Lee J, Cho MH (2013a) Band gap narrowing of titanium dioxide
(TiO2) nanocrystals by electrochemically active biofilms and their visible light activity.
Nanoscale 5:6323–6326
Kalathil S, Khan MM, Lee J, Cho MH (2013b) Production of bioelectricity, bio-hydrogen, high
value chemicals and bioinspired nanomaterials by electrochemically active biofilms. Biotech
Adv 31:915–924
Kalathil S, Lee J, Cho MH (2013c) Gold nanoparticles produced in situ mediate bioelectricity and
hydrogen production in a microbial fuel cell by quantized capacitance charging. ChemSusChem
6:246–250
Kalathil S, Lee J, Cho MH (2013d) Catalytic role of Au@TiO2 nanocomposite on enhanced
­degradation of an azo-dye by electrochemically active biofilms: a quantized charging effect.
J Nanopart Res 15:1392–1398
Khan MM, Kalathil S, Lee J, Cho MH (2012) Synthesis of Cysteine Capped Silver Nanoparticles
by Electrochemically Active Biofilm and their Antibacterial Activities. Bull Kor Chem Soc
33:2592–2596
Khan MM, Ansari SA, Lee J, Cho MH (2013a) Highly visible light active Ag@TiO2 nanocompos-
ites synthesized by electrochemically active biofilm: a novel biogenic approach. Nanoscale
5:4427–4435
Khan MM, Ansari SA, Lee J, Cho MH (2013b) Novel Ag@TiO2 nanocomposite synthesized by
electrochemically active biofilm for nonenzymatic hydrogen peroxide sensor. Mater Sci Eng C
33:4692–4699
Khan MM, Kalathil S, Han TH, Lee J, Cho MH (2013c) Positively charged gold nanoparticles
synthesized by electrochemically active biofilm—a biogenic pproach. J Nanosci Nanotechnol
13:6079–6085
Khan MM, Lee J, Cho MH (2013d) Electrochemically active biofilm mediated bio-hydrogen pro-
duction catalyzed by positively charged gold nanoparticles. Int J Hydr Energy 38:5243–5250
Khan MM, Ansari SA, Lee JH, Lee J, Cho MH (2014) Mixed culture electrochemically active
biofilms and their microscopic and spectroelectrochemical studies. ACS Sustain Chem Eng
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ration and potential drop phenomenon at series connection of unit cells in shared anolyte.
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a microbial fuel cell. Water Res 39:942–952
88 M.M. Khan

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(BES) for sustainable energy production and product recovery from organic wastes and indus-
trial wastewaters. RSC Adv 2:1248–1263
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study of microbial communities involved in bioenergy. Nat Rev Microbiol 6:604–612
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organic matter in a bioelectrochemical system. Electrochem Commun 11:1752–1755
Chapter 5
In-Situ Transesterification Reaction
for Biodiesel Production

Ahmad Hafiidz Mohammad Fauzi, Ramli Mat, and Anwar Johari

Contents
5.1 The Importance of Crude Oil and Its Derivatives ............................................................. 90
5.2 Biofuel as an Alternative to Fossil Fuel ............................................................................ 91
5.2.1 Biodiesel Production ............................................................................................. 92
5.3 In-Situ Transesterification ................................................................................................. 94
5.3.1 Catalytic Process ................................................................................................... 95
5.3.2 Non-catalytic Process............................................................................................ 98
5.3.3 Advanced Process for In-Situ Transesterification ................................................. 99
5.4 In-Situ Microalgae Transesterification .............................................................................. 100
5.5 Conclusion and Future Perspective ................................................................................... 103
References .................................................................................................................................. 104

Abstract Biodiesel synthesis can be conducted using transesterification of triglyc-

erides in the presence of catalyst and alcohol. The oil extraction and transesterifica-
tion steps are carried out separately for the conventional biodiesel production, which
can result in longer time requirement and using different operating units. An alterna-
tive to the conventional method is the in-situ transesterification process, where it
combines both extraction and transesterification processes into a single-step pro-
cess. Biomass feedstock is used directly in the in-situ method, which can reduce the
time required to obtain biodiesel, as well as conduct both processes simultaneously.

A.H.M. Fauzi • R. Mat (*)

Chemical Reaction Engineering Group (CREG), Faculty of Chemical Engineering,
Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia
e-mail: ramli@cheme.utm.my
A. Johari
Institute of Hydrogen Economy (IHE), Faculty of Chemical Engineering,
Universiti Teknologi Malaysia (UTM), 81310 Skudai, Johor, Malaysia

K.R. Hakeem et al. (eds.), Biomass and Bioenergy: Applications, 89

DOI 10.1007/978-3-319-07578-5_5, © Springer International Publishing Switzerland 2014
90 A.H.M. Fauzi et al.

The single-step process can be integrated with other technology such as microwave
irradiation to enhance biodiesel productivity. Furthermore, the in-situ transesterifi-
cation process involving microalgae feedstock has started to gain attention from
researchers, where microalgae biomass is utilized as a feedstock for the in-situ trans-
esterification process without the lipid extraction step prior to the transesterification
reaction. This chapter focused on the in-situ transesterification process for biodiesel
production, particularly for both catalytic and non-catalytic processes, and also the
application of the single-step process for biodiesel synthesis from microalgae.

Keywords Biodiesel • Transesterification • Catalyst • In-Situ • Microalgae

5.1 The Importance of Crude Oil and Its Derivatives

Crude oil is an important source of energy that has played an integral role in our
society for a very long time. It is extremely important throughout the world, as the
derivatives of crude oil are used in different applications in our daily life. For exam-
ple, gasoline and diesel fuel are used as fuel in internal combustion engine, base oil
as lubricant, petrochemical products (plastic, paint, adhesive), and many more. The
straightforward refining process enables the production of a variety of products
based on crude oil. The process occurs at different temperatures within the fraction-
ation column, depending on the final products. Three major categories from crude
oil-refining process are light, medium, and heavy distillates and residuum. Different
sectors depend on the use of crude oil, where four of the main sectors are transporta-
tion, industrial, residential and commercial, and electric power (EIA 2012).
According to the U.S. Energy Information Administration (U.S. EIA), transporta-
tion is the second largest energy consumer in the U.S. after industrial sector, and it
was estimated that, in 2010, about 97 % of energy consumption in the transportation
sector came from petroleum, which is obtained by processing crude oil (EIA 2012).
Although we are heavily dependent on crude oil, there are some concerns regard-
ing the continuous use of crude oil and its derivatives as it has finite supply and is
nonrenewable. With the continuous use of crude oil and its derivatives, Maggio and
Cacciola (2012) forecasted that the oil production is expected to decline after they
predicted the peak productions of oil will occur between year 2009 and 2021. Based
on the data obtained from BP Statistical Review of World Energy 2013 (BP 2013),
the production and consumption of oil steadily increased over the past 10 years, and
since year 2007, the consumption of oil exceeded its production, and this situation
is alarming due to the finite amount of crude oil available.
Other than that, combustion of fossil fuel releases substances that are harmful to
human and also the environment, such as carbon dioxide, carbon monoxide, sulfur
dioxide, and particulates. The biggest concern with the product from combustion of
fossil fuel in the engine is carbon dioxide (CO2), as it is the most significant green-
house gas that contributes to global warming potential compared to others. Statistical
data has shown that the CO2 emissions increased steadily each year since 1965, and
5 In-Situ Transesterification Reaction for Biodiesel Production 91

there was an increase of approximately 36 % of world’s total CO2 emissions from

year 2000 to 2012, where the emission recorded in 2012 was 34,466 million tons of
CO2 emitted (BP 2013). In addition, among the four main sectors that depend on the
use of crude oil and its products as the source of energy, transportation sector
recorded the highest CO2 emissions among those four sectors (1,802 million metric
tons of CO2) in the U.S. for year 2011, which accounts for 79 % of the total CO2
emission (EIA 2012). The products include aviation gasoline, distillate fuel oil, jet
fuel, motor gasoline, and diesel.

5.2 Biofuel as an Alternative to Fossil Fuel

In order to alleviate the problems regarding finite amount of crude oil reserve and
harmful consequences due to emissions from combustion of fossil fuel, countries
around the world have turned their attention to its alternative, biofuel. Biofuel is a
type of fuel that is produced from biomass source as a substitute for crude oil. There
are two common biofuels that have received considerable attention from users,
which are bioethanol and biodiesel. The emergence of biofuel as a substitute to
crude oil seems to be important in an effort to reduce the release of CO2 into the
atmosphere, as the impact of global warming can be reduced. Other than that,
biofuel has higher oxygen content than petroleum, which leads to higher percentage
of complete combustion, and at the same time, the amount of hydrocarbon, carbon
monoxide, and particulate emissions is reduced (Tye et al. 2011).
Biofuels production increased from year to year. As reported by BP (2013), the
world’s total biofuels production increased almost sevenfold since 1992, where
around 60,220 thousand tons of oil equivalent biofuels were produced in 2012, with
almost 50 % of the total biofuels produced in North American countries (U.S. and
Canada). This trend highlights the significant role of biofuels in reducing the depen-
dency on crude oil, and also in ensuring that sustainable biofuel production has
positive impacts on CO2 emission. With the availability of these biofuels, the depen-
dency on crude oil can be decreased, especially for the transportation sector. Using
bioethanol as a fuel additive can reduce the emission of carbon monoxide and other
substances that caused smog, while biodiesel can be utilized as an alternative for
fossil diesel in diesel engines (Tye et al. 2011).
The main process involved in the production of bioethanol is the conversion of
sugars into alcohol (i.e., ethanol) via fermentation process. During the production,
hydrolysis of carbohydrates in biomass source produces sugars, and further conver-
sion will produce bioethanol. It is suitable to be used as fuel additive that can increase
the octane level for improving engine performances, and the by-product from bio-
ethanol, dried distillers grain with soluble DDGS, can be used as livestock feed.
Another type of biofuel that can be used as an alternative to crude oil derivatives is
biodiesel. Different from bioethanol, biodiesel is mainly produced from feedstocks
that contain triglycerides. Biodiesel can be obtained via transesterification process,
where triglycerides are converted into fatty acid alkyl esters (FAAE) in the presence
92 A.H.M. Fauzi et al.

of catalyst and alcohol, such as methanol. Biodiesel can replace fossil diesel for any
diesel engine application. The high viscosity of vegetable oils and animal fats is
reduced via transesterification or esterification reactions, and the resultant product
can be used directly or blended with fossil diesel.

5.2.1 Biodiesel Production

Two methods that are commonly applied for biodiesel synthesis are transesterifica-
tion and esterification processes. In the transesterification process, biodiesel is pro-
duced from transesterification of triglycerides in the presence of alcohol and
catalyst, and the by-product from the process is glycerol. According to the stoichio-
metric ratio of the transesterification reaction, 3 mol of alcohol are required for
1 mol of triglyceride for the reaction to proceed, and this produces 3 mol of fatty
acid alkyl esters and 1 mol of glycerol. Usually, large amount of alcohol is required
to shift the reaction towards the product formation and increase the biodiesel yield,
as transesterification is an equilibrium reaction. Besides, the yield can also be
obtained faster by conducting the process at elevated temperature, and also by
employing suitable catalysts, depending on the types of the process.
In contrast to transesterification reaction, esterification involves production of
biodiesel from free fatty acid (FFA), where 1 mol of FFA is converted to 1 mol of
FAAE in the presence of alcohol and catalyst. Moreover, water is a by-product for
this reaction, instead of glycerol. Esterification reaction is important for feedstock
that contains high amount of FFA, as this can interfere with the process, especially
when alkaline catalysts are used for biodiesel synthesis. Both esterification and
transesterification processes can be performed subsequently, where esterification
process is employed in the first step to minimize the FFA content in the feedstock,
and then followed by transesterification process for the conversion of feedstock to
biodiesel. However, this two-step biodiesel synthesis involves the use of two differ-
ent catalysts; acid catalyst for esterification reaction, and alkaline catalyst for trans-
esterification, which can increase the production cost.
Catalysts are utilized for biodiesel synthesis to increase the reaction rate for the
formation of biodiesel. Besides, the use of catalyst also allows the reaction to be
conducted at lower reaction temperature and faster reaction compared to the reaction
conducted without catalyst. Figure 5.1 shows different types of catalysts that are
utilized in biodiesel synthesis. Generally, they can be divided into three main catego-
ries, which are homogeneous, heterogeneous, and enzyme catalysts. At the moment,
most biodiesel production at the industrial scale is conducted using homogeneous
catalyst, especially alkaline catalyst, such as sodium hydroxide (NaOH) and potas-
sium hydroxide (KOH). For feedstock with high FFA content, homogeneous acid
catalyst is preferred as acidic catalyst can withstand the presence of FFA, which is
converted to FAAE via esterification process. Soap formation can be observed if the
feedstock with high FFA content is employed in biodiesel synthesis using alkaline
5 In-Situ Transesterification Reaction for Biodiesel Production 93

Fig. 5.1 Types of catalysts used in biodiesel production

catalyst. This will reduce biodiesel yield and further complicates the downstream
processing of biodiesel synthesis.
Although homogeneous catalysts are preferred to catalyze biodiesel synthesis,
one of the main disadvantages is that the separation of the catalysts from the reac-
tants at the end of the reaction can be difficult. As the catalysts are in the same phase
with the reactants, they are usually removed from the reactants after separation of
biodiesel from glycerol, and further washing of biodiesel is required to remove any
traces of catalysts completely from biodiesel and improve its purity. In recent years,
the applications of ionic liquids as catalysts for biodiesel production have been
reported extensively (Elsheikh et al. 2011; Man et al. 2013). Ionic liquids (ILs) are
made from a combination of different types of cations and anions, and their negli-
gible vapor pressure, high thermal stability, and good solubility and miscibility with
reactants allow them to be recovered and recycled after the transesterification reac-
tion is finished, which is one of the benefits of using ILs (Mohammad Fauzi and
Amin 2012). They also have excellent catalytic activity in catalyzing the transesteri-
fication reaction, where most of them are Brønsted acidic ionic liquids (Ghiaci et al.
2011; Fang et al. 2011).
Heterogeneous catalyst is another type of catalyst that is used for biodiesel pro-
duction (Mat et al. 2012). Although many research have employed heterogeneous
catalysts to obtain biodiesel at the laboratory and pilot scale, there are limited appli-
cations of this type of catalyst at the industrial scale. The utilization of heteroge-
neous catalysts enables transesterification reaction to be conducted in continuous
process as the catalysts can be placed in fixed bed reactor, and they can be replaced
or regenerated once their catalytic activity has deteriorated. However, the operating
conditions for heterogeneous catalysts can be quite severe, where longer reaction
time and elevated temperature are required due to the different phase between cata-
lysts and reactants. Enzyme is another interesting option as catalyst in biodiesel
production, as high purity biodiesel can be obtained, and there is no formation of
soap when feedstock of high FFA is used, where enzyme can be used to simultane-
ously conduct esterification of FFA and transesterification of triglycerides in a sin-
gle step (Taher et al. 2011). However, high cost and enzyme’s deactivation hinder its
utilization for large-scale biodiesel production.
94 A.H.M. Fauzi et al.

5.3 In-Situ Transesterification

Conventional biodiesel production involves a two-step process, where oil is

extracted from biomass feedstocks prior to conducting transesterification reaction.
This method is not really efficient, as different equipments are used for both pro-
cesses, and longer time is required as the processes cannot be conducted at the same
time. In addition, after the oil extraction step, the leftover biomass needs to be sepa-
rated before proceeding with the transesterification process. There is also the pos-
sibility of using different solvents for these two processes, which can increase the
operating cost for biodiesel production. Hexane is usually chosen for the extraction
of oil from biomass due to its good solubility with the triglycerides. In contrast,
methanol, which is commonly used as the solvent in the transesterification process,
has poor miscibility with oil or lipid, and resulted in low extraction efficiency (Mat
et al. 2011; Lee and Lim 2012).
A process known as in-situ transesterification combines both extraction and
transesterification processes, where they proceed simultaneously in a single step.
It is also known as reactive extraction process. The difference between conventional
and in-situ transesterification is shown in Fig. 5.2. For the conventional process, the
oil extraction and transesterification processes are conducted in two separate steps.
After the oil is obtained, only then the transesterification step can be carried out.
This process can also be quite lengthy, as biomass left after the oil extraction phase
needs to be separated from the oil, and the solvent used must also be removed to

Fig. 5.2 Comparison

between (a) conventional and
(b) in-situ transesterification
5 In-Situ Transesterification Reaction for Biodiesel Production 95

prevent any interference with the transesterification process. In the in-situ trans-
esterification, the biomass feedstock is used straightaway as the raw material, where
the oil extraction and the conversion to biodiesel are combined in a single step, and
can even also be conducted in a single reactor. The in-situ process reduces the
amount of solvent required as methanol can be used simultaneously for extracting
the oil from biomass, and also as the solvent for transesterification reaction.

5.3.1 Catalytic Process

The presence of catalyst in in-situ transesterification process for biodiesel produc-

tion is important, as it speeds up the reaction to obtain biodiesel. Homogeneous
catalysts are preferred to heterogeneous catalysts, as the latter are less efficient in
terms of mass transfer process between feedstock in the form of seed with the solid
catalyst. Table 5.1 summarizes previous in-situ transesterification processes that
utilized homogeneous catalyst for biodiesel synthesis. All catalysts utilized in
respective processes are alkaline homogeneous catalyst, either using potassium
hydroxide or sodium hydroxide. Different types of feedstocks have also been used
(i.e., rapeseed, jatropha, palm oil).
Zakaria and Harvey (2012) conducted direct production of biodiesel from rape-
seed using in-situ transesterification process and catalyzed by NaOH. Aside from
focusing on the effect of operating parameters, they also studied the effect of water
towards the reaction by comparing the ester yield of wet (6.7 wt% moisture) and dry
(0 wt% moisture) seeds. Ester yield increased for higher methanol to oil ratio up to
nearly 900:1, but decreased afterwards and resulted in harder separation between
ester and glycerol phase. At constant molar ratio of methanol to oil, the final equi-
librium ester yield was achieved for seeds with smaller size (300–500 μm) faster
than those with larger size (1,000–1,400 μm), where they mentioned that the extrac-
tion rate was enhanced by reducing the size of seeds used. On the other hand, higher
reaction temperature (60 °C) allowed the final yield to reach equilibrium faster than
those processes conducted at lower temperature (30 and 40 °C). Finally, for the
effect of water content in the feedstock, there was not much difference for the ester
yield for both wet and dry feedstocks, which lead to the conclusion that the process
economics can be improved by excluding the moisture content removal step for
seed with less than 6.7 wt% moisture content.
Biodiesel production from rapeseed by in-situ transesterification process was
conducted by Abo El-Enin et al. (2013), which also include the techno-economic
cost analysis related to the process. KOH was selected to catalyze the reaction.
From the study, higher biodiesel yield was achieved with increasing KOH concen-
tration and reaction time, but decreased for value of higher than 0.02 N and 100 min,
respectively. Meanwhile, there was minimal change in methyl ester yield when
molar ratio of alcohol to oil increased from 1,000:1 to 1,500:1. For the cost evalua-
tion study, the analysis was performed for the production of biodiesel for 1.0 ton.
By assuming the plant capacity of biodiesel production (50,000 tones/year) and the
 96

Table 5.1 In-situ transesterification for biodiesel production from various feedstocks
Alcohol: Mixing Optimum
Feedstock Catalyst Alcohol seed ratio Time (h) Temp (°C) speed (rpm) Yield (%) References
Rapeseed KOH Methanol 720:1 1.0 65 Not mentioned 90 Abo El-Enin et al. (2013)
Jatropha KOH Methanol 6:1 5.0 50 800 87 Amalia Kartika et al. (2013)
Oil palm fiber KOH Methanol 225:1 9.6 60 300 97 Jairurob et al. (2013)
Jatropha NaOH Methanol 400:1 1.0 60 400 95 Kasim and Harvey (2011)
Rapeseed NaOH Methanol 475:1 1.0 60 200 89 Zakaria and Harvey (2012)
A.H.M. Fauzi et al.
5 In-Situ Transesterification Reaction for Biodiesel Production 97

cost of rapeseed ($250/ton), the gross profit was found to be almost twice as much
compared to the conventional method, with the percentage simple rate of return
(%SRR) for the in-situ transesterification process (79.5 %) was way higher than the
conventional method (29.4 %). They proved that in-situ transesterification process
was more promising and gave higher gross profit than the conventional method,
provided that the methanol recovery step was carried out properly as it is an integral
part for in-situ biodiesel production.
The productions of biodiesel from in-situ transesterification using jatropha as the
feedstock have also been studied (Kasim and Harvey 2011; Amalia Kartika et al.
2013). The influence of parameters involved for in-situ transesterification from jat-
ropha has been studied by Kasim and Harvey (2011). A trend of decreasing yield
and methyl ester content was observed when higher size of jatropha was used,
where the highest yield (86.1 %) was obtained for feed with particle size of less than
0.5 mm. Increased mixing speed of the reaction mixture leads to higher responses,
while no significant responses were observed when the mixing speed was increased
from 300 to 400 rpm. On the other hand, no significant change in the yield and
methyl ester content was observed when reaction temperature was increased from
30 to 60 °C, as well as extending the reaction time from 10 to 60 min. The responses
were highest when NaOH concentration of 0.15 N was applied. Higher or lower
catalyst concentration produced lower yield and methyl ester content. They observed
the formation of soap for NaOH concentration of 0.2 N, which then lowered the
amount of yield obtained. Lastly, the highest yield was detected when methanol to
oil molar ratio was 600:1, but the authors mentioned that higher molar ratio can lead
to problems in the downstream separation processes.
Another study that involved biodiesel synthesis from jatropha seeds was con-
ducted by Amalia Kartika et al. (2013). In-situ transesterification was carried out
using jatropha seeds with moisture content of less than 1 %, and then ground for a
mesh size of 35. They included the use of co-solvent to improve the miscibility of the
mixture, as well as accelerate the reaction by using n-hexane. It was observed that
biodiesel yield increased with higher amount of KOH catalyst and ratio of methanol
to seed used. In addition, using methanol to seed of ratio less than 6:1 resulted in
lower biodiesel quality produced, which correspond to high acid value and viscosity
and low FAME purity. Based on the experiments conducted, the highest crude bio-
diesel yield (87 + 1 wt%) was obtained after 5 h reaction time by using methanol to
seed ratio of 6:1, 0.075 mol/L KOH in methanol, stirring speed of 800 rpm, and tem-
perature of 50 °C. The authors highlighted that the effect of temperature on biodiesel
yield was more significant than stirring speed and reaction time, based on the ANOVA
analysis of the experimental data at p = 0.05. In addition, the biodiesel produced using
the in-situ transesterification process met the specifications of Indonesian Biodiesel
Standard, particularly for its density at 40 °C, viscosity at 40 °C, and flash point, but
the cetane number did not meet the required specification.
In addition to rapeseed and jatropha, a group of researchers performed in-situ
transesterification for biodiesel synthesis using palm fiber (Jairurob et al. 2013).
Based on the analysis of fatty acid profiles, the main components in the oil
extracted from the fiber were palmitic acid and oleic acid. The fiber, also known as
98 A.H.M. Fauzi et al.

after-stripping sterilized palm fruit (A-sSPF), was then subjected to in-situ

transesterification process in the presence of KOH as the catalyst. Biodiesel yield
was higher than 90 % for methanol to oil molar ratio of 200:1 and KOH loading of
3 % w/v were employed. Then, the optimization of reaction parameters was per-
formed using Taguchi method. The optimal yield (97.25 % w/w) can be obtained
for methanol to oil ratio of 225:1, catalyst loading of 3.85 % w/v of KOH, reaction
temperature of 60 °C, and conducted for 9 h and 36 min. The authors also compared
biodiesel production using two-step process (i.e., oil extraction and transesterifica-
tion/esterification process) with in-situ transesterification process. Biodiesel yield
using the former method produced 174.6 biodiesel/kg of fresh fruit bunch (FFB),
while the latter produced 271.9 g biodiesel/kg FFB. The difference in the amount
of biodiesel yield was due to the amount of oil lost in the single-step process, as it
simplified biodiesel synthesis from palm fiber.

5.3.2 Non-catalytic Process

In order to improve the feasibility of biodiesel production, the in-situ transesterifica-

tion process can be conducted in the absence of catalyst. This means that the pro-
duction cost can be reduced as no catalyst is involved in the process. Plus, no
additional chemical is required to stop the transesterification reaction. For example,
the addition of acetic acid glacial was needed to suppress the reaction and neutralize
the alkaline catalyst for in-situ transesterification process (Zakaria and Harvey
2012). This step can be eliminated when the reaction is conducted without using any
catalyst. Furthermore, the absence of catalyst simplifies the purification of bio-
diesel, where usually biodiesel is washed several times to remove any traces of cata-
lyst from biodiesel, especially when homogeneous catalyst is employed.
Aside from the non-catalytic system, only a single solvent is used in the process,
where methanol is often used as the solvent. The process is carried out at elevated
temperature and pressure, where methanol is heated and pressurized until it reaches
the supercritical state. In this form, the miscibility of supercritical methanol with
oils and fats is enhanced, which enables the in-situ transesterification process to be
conducted without any catalyst. Tan et al. (2011) performed the in-situ transesterifi-
cation of waste palm cooking oil (WPCO) using the supercritical method. After the
predetermined reaction time, biodiesel was separated with glycerol in a decanter,
with no additional step of catalyst removal required. This makes the separation step
easier, as the presence of catalyst adds extra steps to the process, including stopping
the transesterification reaction, as well as removing catalyst from biodiesel.
Furthermore, about 80 % biodiesel yield can be obtained by conducting the reaction
for only 20 min. The resultant biodiesel was also found to have flash point and kine-
matic viscosity that agreed to the standards specified by ASTM test methods.
Lim and Lee (2013b) studied the process parameters in a supercritical in-situ
transesterification process from Jatropha curcas L. seeds for biodiesel production.
After the seeds were ground and dried accordingly, the supercritical reaction
was conducted by varying different parameters for the optimization study. There
5 In-Situ Transesterification Reaction for Biodiesel Production 99

was no significant difference in the extraction efficiency for different space load-
ings, which was related to the interphase mass transfer resistance. The use of metha-
nol alone as the solvent in the reaction was sufficient, as the addition of co-solvent
(i.e. n-hexane) decreased the FAME yield, and the authors suggested that the dilution
of oil/methanol interphase may have occur when n-hexane was used. Higher reaction
temperature resulted in higher FAME yield, same is true for reaction time, but the
latter was more effective at lower temperature. Elevated temperature allowed the
conversion of oil to methyl ester at faster reaction rate. Lastly, the effect of mixing
intensity was significant to the supercritical process when the reaction was not con-
ducted at the optimum condition. FAME yield of 99.67 % was obtained when the
supercritical in-situ transesterification was performed at optimum condition.
The same authors extended their study to observe the effect of different
co-solvents in the supercritical in-situ transesterification for biodiesel synthesis
(Lim and Lee 2013a). Supercritical process is usually energy-intensive, as the pro-
cess is conducted at high operating temperature and pressure. One of the methods
that can be used to alleviate this condition is by the addition of co-solvent.
Co-solvents with easier separation from products and their inertness in the super-
critical process are suitable to be applied in the process. Several co-solvents have
been considered, including pentane, heptane, toluene, tetrahydrofuran (THF), car-
bon dioxide (CO2), and nitrogen (N2). They found that the higher amount of pentane
applied resulted in the decrease of both extraction efficiency and FAME yield, as it
may have dilute the concentration of methanol, hence reducing its ability to extract
polar compounds. Heptane, on the other hand, enhanced the extraction efficiency as
it has higher solubility towards the nonpolar molecules. Aromatic hydrocarbons
(i.e., toluene, THF) improved the extraction efficiency, but the co-solvents content
higher than 3.0 mL/g diluted the concentration of methanol. The inertness of N2 did
not really improve the extraction efficiency and FAME yield of the process. Finally,
the application of CO2 as co-solvent allows the optimum FAME yield to be obtained
at lower temperature and also lower the methanol to solid ratio.

5.3.3 Advanced Process for In-Situ Transesterification

At the moment, the only feasible method to produce biodiesel is using transesterifi-
cation reaction, where triglycerides are converted to fatty acid alkyl esters in the
presence of alcohol and catalyst. While homogeneous catalysts allow the reaction to
proceed at moderate operating conditions, the homogeneity of the catalyst with
the reactants can become an issue, especially if acidic catalysts are used as acidic
wastewater is generated during purification of biodiesel. On the other hand, hetero-
geneous catalysts offer the recyclability of catalysts, but the reaction requires higher
temperature and longer reaction time. In order to overcome these difficulties, novel
processes and process intensification technologies are applied to enhance biodiesel
productivity. Among the technologies available for the process intensification
are membrane reactor, ultrasonic and microwave-assisted processes, and reactive
distillation (Fauzi and Amin 2013).
100 A.H.M. Fauzi et al.

The use of microwave irradiation is one of the processes of intensification studied

to increase the productivity of biodiesel production. It is considered to be more
effective than the conventional heating in transesterification or esterification reac-
tions, where electromagnetic radiation at microwave length is transmitted and influ-
enced the molecular motions, but does not alter the molecular structure of substance
(Kumar et al. 2011). This resulted in shorter reaction times and energy-efficient
operation. Da Rós et al. (2012) demonstrated the application of microwave-assisted
biodiesel production from beef tallow using enzyme as the catalyst. Usually, the
time required to achieve high biodiesel yield in transesterification process catalyzed
by enzyme would be long as the reaction is slow. However, with the utilization of
microwave technology, the authors showed that in the presence of microwave irra-
diation, the highest transesterification yield can be achieved within 8 h of reaction
time, compared to 48 h required for the reaction that used conventional heating.
They highlighted that the enhanced emulsification speed that influenced the mass
transfer between reactants was achieved for the microwave-assisted process.
Microwave technology is also suitable to be integrated with in-situ transesterifi-
cation process. In the study conducted by Patil et al. (2011), dry algal biomass was
used directly as the feedstock for biodiesel production in the microwave-assisted
in-situ transesterification process. The irradiation was supplied by using an 800 W
microwave, while methanol was used as the alcohol as they mentioned that metha-
nol is a strong microwave absorption material, which can improve the rate of trans-
esterification reaction. The highest FAME yield recorded was 80.1 %, which can be
obtained in just 6 min of reaction. This shows that the presence of microwave irra-
diation reduced the reaction time for biodiesel production significantly.
The same group extended their study in the microwave-assisted in-situ trans-
esterification with slight modifications to the previous study, where wet algal bio-
mass was used, and the process was combined with supercritical ethanol technology
(Patil et al. 2013). They focused on using wet sample instead of dry sample as
drying of microalgae is energy-intensive and can be costly. From the results, it can
be observed that the highest biodiesel yield obtained barely exceeded 30 %. The
yield increased with higher wet algae to ethanol ratio, but decreased for value higher
than 1:9 wt/vol, while longer reaction time resulted in higher biodiesel yield, with
reaction time longer than 25 min did not show any obvious change in the yield.
They determined that the optimum yield can be achieved by using wet algae to etha-
nol ratio of 1:9 wt/vol, reaction time of 25 min, and reaction temperature of 260 °C.

5.4 In-Situ Microalgae Transesterification

Different types of feedstocks have been considered with the aim for sustainable
biodiesel production. Vegetable oils are preferred as the feedstock for biodiesel syn-
thesis, as they contain less free fatty acids. Current feedstocks for commercial bio-
diesel production used vegetable oils such as soybean and oil palm, which can result
in shortages of food production. In order to avoid problems related to food
5 In-Situ Transesterification Reaction for Biodiesel Production 101

Fig. 5.3 Steps involved

in microalgae biodiesel
production

shortages, microalgae have started to emerge as a favorite alternative to conventional

feedstocks among researchers for biodiesel synthesis. Known as the third-generation
biodiesel feedstock, microalgae have the benefits of higher biomass productivity and
oil yield compared to other oil-bearing feedstocks, with the yield as high as 25 times
than traditional biodiesel crops, such as oil palm (Ahmad et al. 2011).
There are several steps involved before microalgae oil can be converted to bio-
diesel. These steps are summarized in Fig. 5.3. Cultivation phase is where the
microalgae increased their body mass for several days, and water and CO2 are the
key elements for the cultivation of microalgae. Next, the dewatering step follows
after they have been harvested, where water is separated from microalgae biomass.
This is to prevent problems during the extraction and transesterification processes
due to the presence of water. After that, lipids are extracted from microalgae bio-
mass, where the obtained lipids will then be converted to biodiesel, while the
remaining microalgae biomass will be utilized for other uses. In-situ transesterifica-
tion is suitable to be used for producing biodiesel from microalgae, where the lipid
extraction and transesterification steps can be combined into a single step. Several
researchers have conducted the single-step biodiesel synthesis using in-situ trans-
esterification process, which are summarized in Table 5.2. Most of them used meth-
anol as the alcohol in the process, with homogeneous catalysts (i.e., KOH, H2SO4)
preferred to catalyze the reaction.
In-situ transesterification of Chlorella pyrenoidosa microalgae was performed
by D’Oca and coworkers (2011). They compared the efficiency of conventional
extraction-transesterification method with the in-situ process. Initially, they studied
 102

Table 5.2 Biodiesel production from in-situ transesterification process from different microalgae species
Algae Alcohol:
Species Catalyst Alcohol amount (g) biomass ratio Time (h) Temp (°C) Yield (%) References
Chlorella pyrenoidosa H2SO4 Methanol 100.9 2:1 4 60 7.8 D’Oca et al. (2011)
Commercial microalgae H2SO4 Methanol 2.5 4:1 2 65 98.0 Haas and Wagner (2011)
Nannochloropsis sp. Mg-Zr Methanol 1 36:1 4 65 28.0 Li et al. (2011)
Nannochloropsis sp. KOH Methanol 2 9:1 0.1 64 80.1 Patil et al. (2011)
Spirulina KOH Methanol 0.5 2:1 1 Room 76.0 Xu and Mi (2011)
A.H.M. Fauzi et al.
5 In-Situ Transesterification Reaction for Biodiesel Production 103

the lipid extraction process using magnetic stirring and ultrasonication methods,
where they found that longer time allowed more lipids to be extracted, with higher
lipid recorded for magnetic stirring method at 120 min. Also, the highest lipid
extracted occurred when a mixture of chloroform and methanol was used. For bio-
diesel production, the conventional extraction-transesterification method produced
higher FAME yield (10.6 %) compared to the in-situ process (8.4 %), although the
latter used higher amount of catalyst loading (20 % H2SO4). The low FAME yield
recorded may be due to the low amount of lipid in microalgae, with insufficient
reaction time as the transesterification process using acid catalyst requires extended
reaction time to achieve high yield, whereas the reaction was only conducted for 4 h.
Xu and Mi (2011) used Spirulina as the microalgae feedstock for biodiesel pro-
duction involving in-situ transesterification technology. KOH was utilized as the
catalyst, with the effects of different co-solvents in the conversion examined. Some
of the important criteria of co-solvents highlighted by the authors are immiscible in
water, miscible with triglyceride and methanol, maintained inertness in the in-situ
reaction, and low toxicity. Out of five solvents that met these criteria, the optimum
biodiesel yield was observed when the reaction was conducted in the toluene-
methanol mixture with 2:1 ratio of volume per volume. They mentioned that the
best solvent system may vary for different microalgae species as the constituents in
microalgae depend on the microalgal species. Plus, the ratio of the binary mixture
must be correct, as methanol is a polar compound, while toluene is a nonpolar com-
pound. Incorrect ratio will lead to more extraction for one type of compound, either
polar or nonpolar.
The utilization of heterogeneous catalyst in one-step biodiesel production from
Nannochloropsis sp. was studied by Li et al. (2011). Magnesium-zirconia (Mg-Zr)
solid base catalyst was synthesized prior to the in-situ reaction. Higher methyl ester
yield was obtained for higher amount of Mr-Zr used, where the catalyst amount of
10 % gave the highest yield at methanol-dichloromethane volume of 45 mL, and
decreased for catalyst loading for 15 % catalyst. Meanwhile, it was observed that
the one-step transesterification managed to produce higher methyl ester yield com-
pared to the two-step conventional method, where the authors highlighted that the
one-step method simplified the conversion process, as well as reduced the numbers
of operating units and the overall process costs. Plus, the heterogeneous catalyst
enabled easier separation of catalyst from microalgae residue, although the reported
methyl ester yield was low compared when using homogeneous catalyst.

5.5 Conclusion and Future Perspective

In the wake of continuous use of crude oil, biofuel emerges as a suitable alternative
that can ease our dependency on crude oil and its derivatives, especially in the trans-
portation sector. Biodiesel, which can be produced from either transesterification of
triglycerides or esterification of free fatty acids, requires the lipid extraction and
conversion to biodiesel steps to be conducted separately in the conventional
104 A.H.M. Fauzi et al.

biodiesel production. To improve the feasibility of biodiesel synthesis, in-situ trans-

esterification method offers the simplification of the conventional process, where
the lipid extraction and conversion to biodiesel is conducted simultaneously in a
single operating unit. The one-step method reduces the time required to obtain bio-
diesel, as well as reduces the amount of solvents used by utilizing the same solvent
for both extraction and transesterification processes.
Homogeneous catalysts are more suitable to be employed in the in-situ trans-
esterification process as heterogeneous catalysts interfered the mass transfer pro-
cess between reactants involved in the process. The inclusion of co-solvent can help
to enhance the one-step process to obtain biodiesel. In addition, in-situ transesteri-
fication can be enhanced to improve biodiesel productivity either by conducting the
process in the absence of catalysts (i.e. supercritical methanol), or by integrating the
process with other novel process (i.e. microwave irradiation). The single-step pro-
cess also starts to gain attention for biodiesel synthesis from microalgae. In the
process, microalgae biomass is used directly as the feedstock, where simultaneous
lipid extraction and transesterification of lipid to biodiesel occur at the same time.
Although the in-situ transesterification method seems as beneficial in terms of
conducting two different processes simultaneously, there are some areas that require
improvements to ensure that the process is feasible to be conducted, especially at the
industrial scale. The first area is related to the use of novel processes to enhance the
in-situ transesterification reaction. Different types of novel processes are available,
and studies that focused on integrating the in-situ method with novel processes should
be carried out to improve biodiesel productivity. Another area is regarding the use of
co-solvents in the in-situ transesterification. There are many co-solvents that can
enhance the reaction; therefore, determining types of solvents suitable for the in-situ
process is important as well for the feasibility of biodiesel synthesis in larger scale.

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Chapter 6
Abaca Fiber: A Renewable Bio-resource
for Industrial Uses and Other Applications

Romel B. Armecin, Feliciano G. Sinon, and Luz O. Moreno

Contents
6.1 Physico-chemical Characteristics of Abaca Fiber............................................................. 108
6.1.1 Physical Dimensions of Abaca Fiber .................................................................... 108
6.1.2 Moisture Content .................................................................................................. 109
6.1.3 Tensile Strength, Elongation at Break and Elastic Modulus of Abaca Fiber ........ 110
6.1.4 Chemical Composition.......................................................................................... 111
6.2 Integrated Industrial Uses of Abaca .................................................................................. 112
6.2.1 Abaca for Pulp and Paper ...................................................................................... 112
6.2.2 Natural Fibers for Composites .............................................................................. 113
6.2.3 Abaca Fiber for Geotextiles .................................................................................. 114
6.3 New Application of Abaca Fiber....................................................................................... 114
6.4 Conclusions and Future Challenges .................................................................................. 115
References .................................................................................................................................. 116

Abstract Abaca fiber is considered as one of the strongest among natural fibers
which is three times stronger than sisal. This is one of the finest among natural
fibers and believed to be resistant to salt water decomposition than any other vege-
table fibers. It originated in the Philippines and is one of the dollar earners of the
country for centuries. The fiber cells of mature abaca is longer and has thicker cell
wall than younger abaca pseudostems which would suggest that the cell growth is
more on the increased in length and thickened cell walls rather than the expansion
of the cell diameter by itself. Aside from the novel compounds, the dominance of
some essential elements in the abaca fiber would possibly lead to soil fertility
decline due to crop uptake. Moisture content of the dried fiber should be lower than
14 % to avoid deterioration and microbial damage caused by molds and fungi.

R.B. Armecin (*) • F.G. Sinon • L.O. Moreno

National Abaca Research Center, Visayas State University, Visca, Baybay, Leyte, Philippines
e-mail: rbarmecin@vsu.edu.ph; rbarmecin@gmail.com

K.R. Hakeem et al. (eds.), Biomass and Bioenergy: Applications, 107

DOI 10.1007/978-3-319-07578-5_6, © Springer International Publishing Switzerland 2014
108 R.B. Armecin et al.

Tensile strength and E-modulus are important parameter of abaca fiber specifically
for aerospace and automotive applications. Pulp and paper are the principal interest
best suited for bank notes, currency papers, cigarette filters, toiletries, lens cleansing,
tea bags, and other related products. Composites were also an interesting uses of
abaca fiber for aerospace and automotive industries. Geotextiles are other uses of
natural fibers (e.g., abaca) for environmental protection specifically for soil conser-
vation and control of soil erosion. New application of natural fiber is on the rise
such as the preparation of cellulose nanocrystals as components of the composites.
However, threats and emerging issues are one of the concerns in the sustainability
of the major abaca growing areas around the globe. Nutrient depletion, which often
leads to soil degradation, is one of the major threats of the industry. As a conse-
quence, under these conditions, abaca plants are vulnerable to various environmen-
tal stresses such as the occurrence of the threatening disease such as the abaca
bunchy top virus disease.

Keywords Abaca (Musa textilis Nee) • Natural fiber • Specialty paper • Composites
• Geotextiles

In the global market, abaca fiber is commonly known as Manila hemp which is also
considered as one of the strongest among vegetable fibers. It is much stronger than
sisal and more resistant to salt water decomposition than any other natural fibers.
It is a biodegradable material that possesses higher tensile strength and lower elon-
gation in both wet and dry states compared to the synthetics ones. This is a unique
property of abaca fiber which has superior quality compared to that of the rest of
natural fibers derived from various economically important fiber crops.
This particular crop is widely grown in the Philippines primarily for its fibers
which are utilized for various industrial uses. The major key players and processors
of the abaca fiber include the pulp, cordage, and fibercraft industries. It is considered
as one of the pillars among export commodities of the country that continues to be
one of the important sources for employment and foreign exchange earnings. This is
an economically important crop of the country because of its wide range of uses par-
ticularly in the manufacture of tea bags, meat casing, currency notes, cigarette filter
paper, cable insulation, and a host of other industrial products. These are some of the
wide array of applications for this particular highly valued agro-based natural fiber.

6.1 Physico-chemical Characteristics of Abaca Fiber

6.1.1 Physical Dimensions of Abaca Fiber

The ultimate fiber cells of abaca are 3–15 mm long and 3–30 μm in diameter, with
lumen width of about 3 μm (Kohler 2006). In cross section, they are oval or rounded
polygon with five or six sides. Longitudinally, they are tapering gradually to a
6 Abaca Fiber: A Renewable Bio-resource for Industrial Uses and Other Applications 109

Table 6.1 Average cell length, diameter, width, and wall thickness of five abaca varieties
(Moreno et al. 2006)
Variety Cell length (mm) Cell diameter (mm) Lumen width (mm) Wall thickness (mm)
Inosa 3.29 0.0231 0.0201 0.0015
Laylay 3.35 0.0232 0.0196 0.0018
Linawaan 2.81 0.0340 0.0310 0.0016
Lagwis 2.75 0.0335 0.0300 0.0017
Minenoga 2.82 0.0320 0.0295 0.0016

pointed or rounded end (Bawagan et al. 1972; Batra 1985; Sun 1998). Fiber cells
have large lumen and sometimes, relatively thin walls. The hollow structure of the
fiber cells may have contributed to the lower density of the fiber bundle.
Almost all natural fibers have similar cell length with abaca fiber. Both hemp and
abaca have similar cell widths of 0.02–0.05 mm (Rowell 1995). The length of abaca
fiber bundle resembles that of jute fiber; however its diameter is bigger. Among the
common abaca varieties grown massively in the Central Philippines, var. Laylay has
the longest cell length of 3.35 mm followed by Inosa at 3.29 mm while Lagwis the
shortest with only 2.75 mm (Table 6.1). Linawaan has the largest diameter of
0.034 mm followed by Lagwis. In terms of cell wall thickness, Laylay showed the
thickest wall at 1.8 μm while Inosa is the thinnest of only 1.5 μm (Moreno et al. 2006).
Fiber cells of mature stalks are more uniform and longer than from younger
stalks. It has also thicker walls of about 2.3 μm. The cells from younger stalks have
bigger lumen to wall ratio than the cells from mature stalks. Generally, the fiber cell
of mature stalk is longer and has thicker cell wall than cells of younger stalk. This
observation may mean that the cell growth is more on the increasing length and the
thickening of the cell walls but not on the expansion of the diameter of the cell itself.

6.1.2 Moisture Content

The presence of hydroxyl groups or weak hydrogen bonds in natural fibers like
abaca becomes a drawback in its application for resin matrices since it absorbs and
releases moisture rapidly (Biswas et al. 2001). This leads to poor wettability with
resin and weak interfacial bonding. Consequently, composites have poor environ-
mental performance due to delamination under humid conditions. Through appro-
priate pretreatment of the fiber, its moisture absorption is reduced and the wettability
with the resin is improved (Rowell et al. 2000).
Different plant-based natural fibers vary in their equilibrium moisture content
with respect to the levels of relative humidity. The moisture content of fiber from
the newly harvested abaca is about 45 % and reduced to about 8 % after 2–3 h of
sun drying under summer weather condition (Sinon 1997). In the Philippines where
the temperature range between 23 and 30 °C and RH between 60 and 75 %, abaca
fiber can be stored safely at storage conditions of 8–12 % moisture content.
110 R.B. Armecin et al.

However, above 14 % of moisture content, abaca fiber starts to deteriorate due to

microbial infestation (e.g., molds and fungi).
Likewise, abaca fiber showed an interesting characteristic in both the moisture
uptake of dry fiber and the corresponding water release by the moist fiber. In the first
20 min, the rate of moisture uptake of dried abaca fiber was fast and slowed down
after 30–60 min. The highest moisture content (i.e., 4.5 %) is reached when the RH
is between 32 and 37 % with a temperature range of 24–26 °C. Likewise, fiber sub-
jected to 92 % RH initially gained 23 % MC. Furthermore, natural fibers released at
a minimum of 11.7 % MC in 60 min having a RH and temperature range between
45 and 47 % and 20–22 °C, respectively.

6.1.3 Tensile Strength, Elongation at Break and Elastic

Modulus of Abaca Fiber

The quality of natural fiber for reinforcement is usually evaluated in terms of its
tensile strength. This is the maximum stress of the stress–strain curve, where stress
is defined as force per sectional area and strain (or elongation) is defined as percent
of extension (mm) divided by the length (mm). Since the cross section of natural
fibers is irregular and difficult to measure, strength is expressed in relation to its
specific weight, as specific strength denoted in cN/tex, where cN (centi-Newton) is
the unit of force at breaking point and tex is the linear density equal to the mass of
the fiber in grams per 1,000 m length.
Another important parameter in assessing fiber quality is the modulus. This is the
stress needed to affect a certain strain of the material, i.e., the slope of the material’s
stress–strain curve, which is a measure of the material’s stiffness classified as abso-
lute or specific modulus. The absolute modulus of the fiber is the slope of its stress
versus strain curve, taken at low elongation in the proportional zone, while specific
modulus is its elastic modulus divided by its mass density. This measurement is a
very important feature for natural fibers in cases where maximum strength for mini-
mum weight is required such as in aerospace and automotive applications.
Kohler and Kessler (2000) reported that abaca, hemp, kenaf, and sisal have spe-
cific tensile strength in comparison to glass fiber. They found out that hemp and
scutched flax were the only natural fibers that have comparable specific modulus
with glass. They also reported that scutched flax has significantly greater elastic
modulus than unretted and STEX flax. It can also be noted that materials having
higher tenacity and elastic modulus are suitable reinforcement for plastics with high
rigidity and impact strength, while materials having high tenacity and lower elastic
modulus are potential reinforcements for plastics exposed to high bending stresses.
Likewise, Munot (2002) reported that substitution of abaca fiber to glass fiber for
W168/W169 in direct long fiber thermoplastic compounding for under panel in
A-class passenger car has an estimated savings of about 8 %. He found out that the
density of natural fibers is almost half of that of glass fiber. However, the tensile
strength of glass fiber is more than thrice that of natural fibers. In terms of E-modulus
and specific E-modulus, flax and abaca surpass glass fiber.
6 Abaca Fiber: A Renewable Bio-resource for Industrial Uses and Other Applications 111

6.1.4 Chemical Composition

Natural fibers are composed of cellulose (60–67 %), hemicellulose (12–20 %),
lignin (3–12 %), wax (0.3–1.5 %), and water-soluble materials (1–10 %) (Escolano
et al. 1976; Escolano 1977). Cellulose is a natural polymer consisting of D-glucose
monomer units. These are largely crystalline, organized into microfibrils and is very
stable in normal environments.
Cellulose is a linear chain of different glucose units and is considered a structural
component of the cell walls of many plants. The walls where the cellulosic sub-
stances can be found may also contain polyphenols such as lignins and to some
extent structural proteins. The prevalence of polysaccharides in this particular cel-
lular organelle is advantageous for plants as they are generated directly from the
products of photosynthesis.
The positioning of the three hydroxyl groups in each glucose monomer, strong
hydrogen bonds are formed between this group and the adjacent chains. The
H-bonding of many cellulose molecules results in the formation of crystalline
microfibrils as well as in an amorphous form (Carpita 2012) that can interact to
form fibers. Cellulose fibers contain about 500,000 cellulose molecules. The high
tensile strength of cellulose is attributed to the strong H-bonding that is formed in
cellulose molecules (Biagiotti et al. 2004). Hemicellulose is made up of highly
branched sugars such as five-carbon, six-carbon, and uronic acid. When it is hydro-
lyzed by diluted acid or base it releases products high in xylose which is a five-
carbon sugar. The swelling of fiber bundle when exposed to high moisture is due to
the absorption of hemicellulose with water.
On the other hand, lignin is a highly branched phenolic polymer with a complex
structure made up of phenylpropanoid alcohols that may be associated with cellu-
loses and proteins. These compounds are found in the middle lamella of the fiber
bundle. Likewise, they are also present in the walls of the fiber cells. Together with
hemicellulose, they are the cementing materials of the fiber cells that make up the
fiber bundle with high tensile strength.
Bismark et al. (2004) reported the approximate chemical composition of abaca
and other natural fibers. They found out that abaca has cellulose contents of only
63.2 % while hemp has the highest of 67 %. However, abaca has the highest hemi-
cellulose of about 20 % while sisal has the lowest of only 12 %. Flax has the lowest
lignin of only 4 % while abaca and jute are the highest with 12 %. Del Rio and
Gutierrez (2006) determined the chemical characteristics of abaca fiber for the man-
ufacturing of pulp for the specialty paper production.
Among the parameters evaluated, it was noted that Klason extractable lignin
(11.8 %) was found to be the dominant component and the least was that of the
water-soluble extracts (0.3 %). Accordingly, the neutral monosaccharides identified,
glucose (87 %) to be the highest simple sugar and the least was noted in the rham-
nose and galactose sugars (0.2 %, respectively). The rest of the neutral simple sug-
ars were found to be intermediary such as arabinose (1.6 %), xylose (7.5 %), and
mannose (3.5 %). Likewise, novel compounds were identified and isolated in abaca
fiber such as free sterols, fatty acids, steroid ketones, triglycerides, and series of
112 R.B. Armecin et al.

Table 6.2 Macro- and Nutrient element Mineral composition

micro-nutrient contents
N (%) 0.038 ± 0.0014
of abaca fiber at harvest
(Armecin 2008) P (%) 0.010 ± 0.0021
K (%) 0.416 ± 0.1645
Ca (%) 0.114 ± 0.0121
Mg (%) 0.051 ± 0.0052
Fe (ppm) 180.00 ± 24.8902
Mn (ppm) 97.40 ± 12.0208
Zn (ppm) 9.76 ± 4.5113
Values are mean ± SE (n = 6)

p-hydrocinnamyl compounds (Del Rio and Gutierrez (2006); and phenylphenale-

non (Del Rio et al. 2006). The presence of these compounds suggests for a specific
functioning in the plant system and which can also be used as a parameter to assess
the quality of the fiber.
Aside from these novel compounds identified, essential elements specifically the
macro- and micro-nutrients are important components in the functioning and fiber
production in the pseudostem tissue of abaca plant. The high concentration of K in
this particular tissue is associated with its high concentration in the harvested fiber
(Table 6.2). It is possible that the influx of K ions in abaca tissue concentrated in the
pseudostem contributed to the high K concentration in the fiber (Armecin 2008; Del
Rio and Gutierrez 2006). Likewise, the fiber was also found to be high in Fe. It is
believed that these nutrients would cause potential risk to nutrient depletion due to
crop removal.

6.2 Integrated Industrial Uses of Abaca

6.2.1 Abaca for Pulp and Paper

The principal interest for abaca fiber (i.e., non-wood fiber) is that it provides fibers
for excellent quality for making specialty paper or it constitutes the sole affordable
source of fibrous raw materials. In addition, a non-wood plant such as abaca is an
alternative to the increasingly scant forest wood as a source of pulp (Jimenez et al.
2007). For pulp and paper, and composite, cellulose is the most important part of the
fiber. This is obtained by removing other chemical components in the fiber bundle.
Fats in the fiber surface are removed with benzene. Water-soluble compounds from
dewaxed fibers can be removed by boiling it with water. Likewise, water-soluble
pectic acid from pulp containing calcium, magnesium, and iron salts can be removed
by boiling in 0.1 N alkali. Similarly, dissolved pectin in boiling ammonium oxalate
or citrate and can be precipitated with calcium ions (Batra 1985).
The pulp of natural fibers is best suited for making specialty papers. Thinness
combined with high strength and durability is every essential for the production of
6 Abaca Fiber: A Renewable Bio-resource for Industrial Uses and Other Applications 113

cigarette, bank notes, technical filters, and other related products. This high-end
products constitute a large portion of total utilization for many natural fibers.
Piotrowski and Carus (2010) reported that a very large portion of cigarette paper is
made from flax and hemp. Tea bags are almost exclusively made of abaca owing to
the fibers exceptional water resistance.

6.2.2 Natural Fibers for Composites

Composites are hybrid materials made of a polymer resin reinforced by fibers. The
physical and chemical identities can be retained for both fibers and matrices.
However, they produce a combination of properties that cannot be achieved with
either of the constituents acting alone. In general, fibers are the principal load-
carrying members, while the surrounding matrix keeps them in the desired location
and orientation. Likewise, these materials would act as a load transfer medium
between them and protects them from environmental damages due to elevated tem-
peratures and humidity (Mallick 2007).
Concerns about the natural environment, protection of natural resources, and the
opportunity to reuse old packaging materials are on the rise. These materials then,
all contribute to the growing interest in environmentally friendly substitutes obtained
from renewable sources. Natural fibers are fibrous materials derived from plants and
animals, produced as a result of photosynthesis (Simon 1998; Zahedifar 1996).
Composites made from natural fiber and polymer such as abaca (Symington 2001;
Teramoto 2004; Tobias 1990) are potential replacement (Bruce 2000; Byrd 2001) of
glass fiber materials. This is renewable (Bartl et al. 2004; Dweib 2004; Gowda et al.
1999) in nature and biodegradable (Simon 1998; Nishino 2003; Ochi 2006; Oksman
et al 2003; Winter 2003) after its use.
Abaca fiber composite was developed as substitute to fiber glass in the car indus-
try (Cho et al. 1997; Fries 2000). Rieter Automotive System (Switzerland) in part-
nership with Daimler Chrysler AG (Germany) and Manila Cordage Co. (Philippines)
has produced a composite based on abaca (Musa textilis Nee) fiber reinforcement of
a PP matrix. This is used in under floor components and as covering of spare tire
wheel (Lelivelt 2003; Daimler Chrysler 2005). Lately, they have also increased the
use of renewable materials in some vehicles by up to 98 % over previous models by
using natural materials such as flax and abaca fibers. The newest Mercedes S-class
vehicle has 27 components made from natural-fiber composites which weigh 43 kg
(73 % more than previously). Daimler Chrysler’s innovative application of abaca
fiber in exterior under floor paneling on the Mercedes A-class, manufactured from
abaca plant fibers, which are extremely elastic and have impressive tensile strength,
has recently been recognized (Daimler Chrysler 2005). The versatility of natural
fibers composite in combination with different production techniques would open
up new possibility for wide applications especially in the developing countries
where natural fibers are indigenous and abundant (Alves et al. 2000; Rijswijk et al.
2001). In the USA the demand for natural fiber in the automobile industry is expected
to rise annually by 30 % and that in the construction sector by as much as 60 %.
114 R.B. Armecin et al.

Likewise, substitution of glass fibers in automotive composites, the specific

tensile strength, elongation at break and specific elastic modulus are very important
properties of natural fibers. Their lower density compared to glass fibers allows it to
achieve similar strength of the end product but with lighter weight. This leads to the
utilization of a lower power engine and reduction of CO2 emission. However, devel-
opers believed that the production and processing of natural fiber is CO2 neutral
(Riedel et al. 2000). Although the tensile strength of abaca is lower than glass fiber,
its specific modulus is greater than glass and when compared on modulus per cost
basis, abaca is better. Apart from much lower cost and the renewable nature of
abaca, much lower energy requirement for its production makes it an attractive rein-
forcing fiber in composites.

6.2.3 Abaca Fiber for Geotextiles

Geotextiles are woven materials either from synthetics or natural fibers which are used
to cover sloping soil surface primarily to prevent erosion (Lee et al. 1994). The use of
woven abaca fiber minimizes water loss in steep slopes and along hill sides as a conse-
quence for too much precipitation. This is also an effective covering to control sedi-
mentation by capturing soil particles removed from other locations. Sometimes it can
be used for drainage control that helps reduce the velocity of water moving downstream
that caused flooding and damage to soil and vegetation. Important considerations to
soil engineering play an important role in designing various geotextile materials.
In some instances, geotextiles from natural fibers are not suitable as reinforcement
in road construction and permanent support to vegetation in channels with high flow
velocities. It is because of their generally lower strength and limited life in moist and
biologically active environments (Kaniraj and Rao 1994). However, this is a good
material in moderate slopes and always disturbed sites where water flow is of low to
medium velocities. This condition will give the soil long-term protection for estab-
lishing healthy vegetation. Thus, soil protection or erosion control products from
natural fibers can vastly accelerate and protect the growth of surface vegetation.
The generally expensive costs of abaca fiber compared to coir, makes the latter
more preferable raw material for the production of natural-fiber geotextiles. However,
in terms of strength and stability of the end product, abaca is far better than coir.

6.3 New Application of Abaca Fiber

Natural fiber was the main reinforcement material available for fiber-reinforced
composites before man-made fiber was developed. However, in recent years the
main driving force in the use of abaca and other fiber plant sources for composites
was mainly technical (Oksman et al. 2003). The use of natural fibers as potential
6 Abaca Fiber: A Renewable Bio-resource for Industrial Uses and Other Applications 115

reinforcement for both organic and inorganic matrices is on the rise. The growing
interest in the use of natural-fiber-reinforced composites was brought about by envi-
ronmental concerns and increasing production cost. There is an extensive research
in some areas concerning natural fiber composite materials. This focuses on the
preparation of cellulose nanocrystals for applications including composites (Winter
2003). It is currently the subject of intensive study of various research groups around
the world. High expectations from the industry will lead to a new era of high-
performance bio-based composite materials. Intensive research activity is another
area of interest that would pave the way for the production of polymers from renew-
able resources. With these developments, commercial production of polymers from
renewable resources like polylactic acid (PLA) is considered as a leading enterprise
(Oksman et al. 2003).

6.4 Conclusions and Future Challenges

The abaca industry is presently facing several concerns especially in crop produc-
tion, and in the processing and marketing of the fiber. These concerns are mainly
affected by different factors such as low fertility of the soil (Armecin et al. 2005),
soil degradation, improper management, and disease caused by bunchy top virus
(Bajet and Magnaye 2002).
As reported by FIDA (2008), the national average in abaca fiber production of
the country is about 800 kg per hectare. This is way behind its potential production
of about 2–3 tons per year. Most of the abaca farms in low producing areas produce
only about 500 kg/year. This low production is caused by factors such as low fertil-
ity of the soil which is the result of several other factors. One of these is erosion of
the top soil. Since abaca is usually planted in hilly or mountainous areas, most of the
top soils are carried along with moving rain water from the top of the mountain
downhill. Other factor in soil fertility is on the transfer of dry matter during harvest-
ing. Instead of returning the waste material back to soil as fertilizer, these are carried
out from the farms to the stripping centers. In some cases, abaca farms have low
maintenance since cleaning activities are only done during harvesting time which
happens thrice or four times a year. Thus, downward trend in abaca production is
mostly observed especially in very old plantation areas of more than 30 years.
Nutrient management studies and soil health assessment are still on progress seek-
ing for an appropriate management strategy in rehabilitating and improving
degraded abaca growing areas.
The low abaca production of the country is greatly affected by bunchy top virus
disease (Raymundo 2001; FIDA 2008). This virus has significantly reduced abaca
plantation in Davao during the 50s, in Bicol areas during the 70s, and presently
damaging about 50 % of the plantations in Central Philippine islands, the highest
abaca producing province in the country. This virus has no cure at the moment.
However, government effort is focused only on proper farm management and
116 R.B. Armecin et al.

eradication of infected plants to prevent the spread of the disease. Research efforts
are also focused on the development of new varieties resistant to the virus either
through traditional breeding activities or through biotechnology. So far, no resistant
variety has been developed yet.

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Chapter 7
Microalgal Biomass as a Source of Renewable
Energy

Syed Hammad Raza, Syed Harris Husssain, Asad Abdullah Shahid,

Uzair Hashmi, and Alvina Gul Kazi

Contents
7.1 Introduction ....................................................................................................................... 120
7.2 Overview of Microalgal Biomass Production Techniques................................................ 121
7.2.1 Cultivation of Microalgae ..................................................................................... 121
7.2.2 Biomass Harvesting .............................................................................................. 122
7.2.3 Cell Disruption ...................................................................................................... 123
7.2.4 Compound Extraction ........................................................................................... 124
7.2.5 Fractionation and Purification ............................................................................... 124
7.3 Microalgal Strains for Bioenergy...................................................................................... 125
7.4 Conversion of Fatty Acids into Bioenergy ........................................................................ 125
7.4.1 Acid-Catalyzed Transesterification ....................................................................... 126
7.4.2 Alkali-Catalyzed Transesterification ..................................................................... 126
7.4.3 Lipid-Catalyzed Transesterification ...................................................................... 126
7.4.4 Microwave Heating ............................................................................................... 126
7.5 Converting Carbohydrates into Bioenergy........................................................................ 126
7.5.1 Anaerobic Digestion.............................................................................................. 127
7.5.2 Fermentation ......................................................................................................... 127
7.6 Processing Techniques Involved in Bioenergy Production/Biomass Conversion
Technologies ..................................................................................................................... 127
7.6.1 Gasification ........................................................................................................... 128
7.6.2 Pyrolysis................................................................................................................ 128
7.6.3 Direct Combustion ................................................................................................ 129
7.6.4 Transesterification ................................................................................................. 129
7.6.5 Hydro Cracking ..................................................................................................... 130
7.6.6 Biochemical Conversion Technologies ................................................................. 130
7.7 Torrefaction ....................................................................................................................... 131

S.H. Raza • S.H. Husssain • A.A. Shahid • U. Hashmi • A.G. Kazi (*)
Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences
and Technology (NUST), Islamabad, Pakistan
e-mail: alvina_gul@asab.nust.edu.pk

K.R. Hakeem et al. (eds.), Biomass and Bioenergy: Applications, 119

DOI 10.1007/978-3-319-07578-5_7, © Springer International Publishing Switzerland 2014
120 S.H. Raza et al.

7.8 Emerging Pathways for Microalgal Biofuel Production ................................................. 132

7.8.1 Hydrothermal Liquefaction ................................................................................. 132
7.8.2 Oil Secretion ....................................................................................................... 133
7.8.3 Alkane Secretion ................................................................................................. 133
7.9 Biorefinery Concept for Biofuels and High Value Products ........................................... 133
7.10 Problems Associated With Bioenergy Generation from Microalgal Strains................... 134
7.11 Economic Feasibility of Microalgae to Biofuel .............................................................. 135
7.12 Biodiesel, Biogas, Bioethanol Production from Microalgae .......................................... 136
7.12.1 Biodiesel ........................................................................................................... 136
7.12.2 Biogas ............................................................................................................... 137
7.12.3 Bioethanol ......................................................................................................... 138
7.13 Future Prospects .............................................................................................................. 139
7.14 Conclusion ...................................................................................................................... 140
References .................................................................................................................................. 140

Abstract With the economy destruction and rapid declination of fossil fuels provi-
sion, there is an urgent need of low carbon economy generation. Traditional sources
of energy have concerns regarding their security and longevity. Searching for fossil
fuel energy alternatives is now given more and more attention. Energy produced
using micro-algal biomass provides the solution to current dilemma, which not only
is renewable source of energy but is environment friendly. Microalgae on account of
their high oil composition and rapid biomass generation have great potential for
biofuel production and hence have emerged as the most promising raw material for
generation of bioenergy. Progress in research methodology for catalytic reactions
has gone quite far that has made the efficient conversion of biomass into biofuels
possible. Procedures including hydrolysis, followed by trans-esterification, hydro-
genation, and isomerization have undergone a great deal of improvement in the last
decade from which microalgal lipids have to go through to obtain high-grade hydro-
carbons. There are a variety of methods to address microalgal processing suggesting
that microalgae are very potent candidates for bioenergy production.

Keywords Biodiesel • Biogas • Bioethanol • Microalgae • Torrefaction

7.1 Introduction

We are living in a world where energy requirements increase everyday. Initially

these requirements were met by using fossil hydrocarbons. But fossil fuels are a
major source of pollution so there has been a decline in their usage as motor oils due
to the progressive introduction of fuel alternatives. Other than that, fossil fuels are
also a non-renewable energy source. There is a limited amount of fossil fuels; as we
set up more oil fields the older ones get depleted. This also destabilizes the prices of
fossil fuels as its demand increases.
Vegetal biomass is now considered as the most important alternative to fossil hydro-
carbons. This is because vegetal biomass is produced by consuming solar, geothermal,
and wind energy source. Vegetal biomass can be converted into feedstock that can be
7 Microalgal Biomass as a Source of Renewable Energy 121

used as an alternative for oil in industries. Moreover, setting up of large-scale biomass

production units can allow us to balance the CO2 emission with CO2 absorption.
Vegetal biomass causes less environmental pollution than other fuel sources, e.g., coal.
Combustion of vegetal biomass yields about 0.2 % SO2 and 3–5 % ash as compared to
coal yielding 2–3 % SO2 and 10–15 % ash (Sorokina et al. 2012). The reason behind
this is fossil fuels contain sulfur, nitrogen, and mineral matter in much higher quanti-
ties as compared to the biomass. The most appropriate method of using biomass is by
converting it into biofuel. There are various techniques to convert biomass into biofuel;
however, the most appropriate biomass-producing crop has not yet been determined.
Therefore, it is essential to find an optimum biomass-producing source, which is read-
ily available and highly productive.
There are three generations of biofuels. The first generation uses conventional
crops such as soybean, sunflower, and sugarcane as raw material. First-generation
biofuels are abundantly produced in the world. The second-generation biofuel pro-
duction utilizes inedible raw materials such as wood processing and agricultural
waste. The second generation is clearly more viable than the first generation as it is
abundantly provided and does not utilize edible material. The third-generation bio-
fuel production is associated with the microalgal biomass processing. Microalgal
biomass is superior to other bioresources as an energetic raw material. Unlike the
terrestrial plants, its growth is more productive and less costly. Some microalgae
can yield about 98 m3 ha−1 of high-grade biofuel. Economic calculations show that
the cost of microalgal biomass production per year, for an annual output of 100 t, is
$3,000. Microalgae are the most quick-growing and highest energy plants. They can
provide a basis for industrial scale biofuel production, and therefore, also the sus-
tainable development of future energy economy (Sorokina et al. 2012).

7.2 Overview of Microalgal Biomass Production Techniques

Microalgae nowadays are of significant interest for large-scale production of biofuel

because they synthesize useful quantities of triacylglycerides and polysaccharides.
These serve as raw material for the production of bioethanol and biodiesel, which
can be used as transport fuels.

7.2.1 Cultivation of Microalgae

7.2.1.1 Raceway Pond System

A raceway pond comprises of an oval channel in a closed loop. It is about 0.25–

0.4 m in depth and is open to the air. The water containing the necessary nutrients
and CO2 is pumped in a cycle. Due to reduced average light supply in the depth of
the pond, raceway pond systems never reach suitable productivity rates. Moreover,
the energy cost of pumping water is high.
122 S.H. Raza et al.

7.2.1.2 Photobioreactors

Photobioreactors (PBRs) consist of a system of transparent tubes in which the

culture medium is enclosed and pumped for circulation from a central reservoir.
PBRs are better for controlling algae culture environment, but they are more expen-
sive than raceway ponds.

7.2.2 Biomass Harvesting

For large-scale production of biofuel from microalgae, a highly efficient system

for harvesting of biomass is required. The techniques that are currently applied in
harvesting biomass from microalgae include centrifugation, flocculation, gravity
sedimentation, electrophoresis techniques, screening and filtration, and flotation
(Uduman et al. 2010).

7.2.2.1 Centrifugation

By the process of centrifugation, a large proportion of microalgae can be removed

from culture medium. Chen et al. (2011) mentioned that centrifugation of pond
effluent at about 500–1,000 × g shows almost 80–90 % of microalgae removal
from culture medium in 2–5 min. Centrifugation is a more preferred method of
harvesting the microalgae from culture medium (Grima et al. 2003); however, it
can damage the cell structure of microalgal cells (Knuckey et al. 2006).

7.2.2.2 Flocculation

In this process, dispersed particles aggregate to form large particles. These large
particles, because of their greater weight, settle down from where they can be easily
recovered.

7.2.2.3 Gravity Sedimentation

This technique uses gravitational force for sedimentation of algal cells. Algal cells
settle according to their density, radius, and sedimentation velocity. Low-density
microalgae are separated unsuccessfully by settling (Edzwald 1993) hence decreas-
ing the efficiency of harvesting.
7 Microalgal Biomass as a Source of Renewable Energy 123

7.2.2.4 Electrophoresis Technique

Another approach to separate microalgae without any chemicals is the electrolytic

method. It involves setting up of an electric field which causes charged microalgae
to gradually move out of the solution. Hydrogen generated during the electrolysis of
water sticks to the microalgae, which are then carried to the surface (Mollah et al.
2004). The benefits of using this method include:
• Environmental compatibility
• Versatility
• Energy efficiency
• Safety
• Selectivity
• Cost-effectiveness

7.2.2.5 Screening and Filtration

The process involves the introduction of the suspension through a screen of a par-
ticular pore size.

7.2.2.6 Flotation

It is a process of separating microalgae using gravitational forces. Air bubbles attach

themselves to solid microalgae particles which are then carried to the surface of the
liquids.

7.2.3 Cell Disruption

There are two methods for the microalgal cell disruption; chemical disruption and
mechanical disruption. Though the mechanical method of disruption requires large
amount of energy, still it is preferred over the chemical method because it avoids
chemical contamination of cells and does not affect the overall functionality of the
cellular content (Chisti and Moo Young 1986; Mata et al. 2010). The microalgal
cells can be mechanically disrupted through the processes:
• Homogenization
• Ultrasound
• Milling
• Autoclaving
124 S.H. Raza et al.

GEA Process Engineering (2011) states that homogenization can be highly

efficient, with a percentage efficiency of about 77–96 %. This means 77–96 % of
microalgal cells will be ruptured. But Greenwell et al. (2010) mentioned that for
homogenization of 10 L of microalgal suspension having microalgal cell concentra-
tions ranging between 100 and 200 g L−1, we would require a high amount of energy
of about 1.5–2.0 kWh.
Another mechanical disruption method is sonication. It involves applying ultra-
sound ranging between 20 and 50 kHz to the sample. The frequency is generated
electronically and the energy is transferred to sample mechanically via a metal
probe. The high frequency generates an area of low pressure. The microalgal cells
move towards the area of low pressure. This area of low pressure has the highest
impact of ultrasound frequency which ultimately breaks open the cell.

7.2.4 Compound Extraction

The extraction of lipids from the microalgal can be done on cryodessicated material
efficiently (Fajardo et al. 2007). Ninety-six percent ethanol is used for the extraction
of lipids from lyophilized biomass. A system having two phases is formed by the
addition of hexane and water to the extracted crude oil. The purified lipids are then
transferred to the hexane phase. Majority of the impurities get left behind in the
aqueous phase.
Carbohydrates present in microalgal cells are of much complex nature and con-
sist of neutral sugars and amino sugars. Carbohydrates found in the microalgal bio-
mass can be quantified by using phenol–sulfuric acid. The sugars are first hydrolyzed
to furans, which are then quantified by spectrophotometry. The carbohydrates can
be extracted by chromatography and acid hydrolysis. Other than that, cell walls of
microalgae can also be hydrolyzed for the production of reducing sugars by using
cellulase (Fu et al. 2010).

7.2.5 Fractionation and Purification

Microalgal biomass includes lignocellulosic components. Lignocellulosic compo-

nents are a resource of relatively low value but they can be used for the production
of fuels and help us meet the present fuel and energy requirements. Research and
development of biorefining technology is ongoing. One of the approaches is the pre-
treatment of raw microalgal biomass, resulting in its fractionation into separate bio-
polymers, which are mainly lignin, hemicellulose, and cellulose. The cellulose
content obtained through this approach can be hydrolyzed easily for obtaining
simple sugars.
7 Microalgal Biomass as a Source of Renewable Energy 125

7.3 Microalgal Strains for Bioenergy

The world’s energy consumption rate increases day by day due to an ever-increasing
population and the overall desire for a better living standard. This consumption rate
of energy usage combined with the knowledge of the threat that carbon dioxide
poses on the climate has led many researchers, scientists, and environmental engi-
neers to study the potential of biofuels as an alternative to overcome the problems
caused by pollution. Among the potential biofuel sources, microalgae are consid-
ered as the most efficient. Microalgae are the most adaptable and sustainable energy
source.
Bioenergy production from microalgae is believed to be one of the most efficient
alternatives for the development of CO2-neutral fuels for several reasons:
1. Microalgae have the most suitable growth rates for biomass production.
2. They have a higher efficiency of photon conversion which results in a higher
biomass yield per unit of surface.
3. They can synthesize and accumulate large quantity of neutral lipids.
4. They can (under specific growth conditions) release hydrogen.
5. They can provide additional benefits of wastewater bioremediation.
One friendly way of producing energy is the production of photobiological H2
using Chlamydomonas reinhardtii (a microalgal strain). Other microalgal strains
that can be used include Chlorella vulgaris, Phaeodactylum tricornutum, and
Nannochloropsis species.

7.4 Conversion of Fatty Acids into Bioenergy

The conversion of fatty acids obtained from microalgal biomass into biodiesel for
the production of energy is done by transesterification process. Transesterification is
a chemical reaction through which fatty acids are bonded to alcohol, resulting in the
production of methyl esters of fatty acids commonly known as fatty acid methyl
esters (FAME) and glycerol. FAME basically is biodiesel. This process reduces the
viscosity of fatty acids and makes them combustible (Chisti 2007).
For the transesterification process, one mole of alcohol is used to transesterify
one mole of esters. Likewise, for the transesterification of one mole of triglyceride,
3 mol of alcohol is used (Fukuda et al. 2001). This process is a reversible reaction,
therefore, for a high yield, 6 mol of methanol are used for each mole of triglyceride.
This large excess ensures the reaction is driven in the direction of FAME
(Fukuda et al. 2001).
The transesterefication process can be catalyzed by acids, alkalis, lipase enzymes,
and microwave heating.
126 S.H. Raza et al.

7.4.1 Acid-Catalyzed Transesterification

The process is driven to completion by the large excess of methanol. In the presence
of a large excess of methanol, the free fatty acids are rapidly transesterified into
methyl esters at a temperature of about 80 °C. The molar ratios and temperature are
the most significant factors affecting the yield of FAME (Zheng et al. 2006).

7.4.2 Alkali-Catalyzed Transesterification

It is about 4,000 times faster than the acid-catalyzed transesterification (Fukuda

et al. 2001). It involves the use of sodium and potassium hydroxides as commercial
catalysts. An even better catalyst such as sodium methoxide is also used, but sodium
hydroxide and potassium hydroxide are often chosen for their cost. Water presence
can cause base hydrolysis so the reaction is kept dry. The optimum conditions for
the alkali-catalyzed transesterification include atmospheric pressure and a tempera-
ture of around 60 °C. In these conditions, the reaction is completed in approximately
90 min (Chisti 2007).

7.4.3 Lipid-Catalyzed Transesterification

Nowadays, the lipase-catalyzed transesterification for FAME production is of great

interest. The use of lipase enzymes does offer many important advantages, but is not
yet feasible because of the high cost of the catalyst (Fukuda et al. 2001).

7.4.4 Microwave Heating

Microwave heating can also be used for speeding up the transesterification process.
This process uses additional catalysts such as scandium triflate and bismuth triflate.
Upon providing a temperature of 150 °C by microwaves, the reaction is completed
in about 20 min (Sochaa and Sello 2010; Levine et al. 2012).

7.5 Converting Carbohydrates into Bioenergy

Algae mostly do not contain simple carbohydrates or easily hydrolysable polysac-

charides. Most commonly found carbohydrates in algae are mannanes, cellulose,
ulvan, fucans, xylanes, alginic acid, agarose, porphyran, furcelleran and funoran,
mannitol, and laminarin. Starch and cellulose are only present in minor quantities.
The yield of ethanol production from biomass is dependent upon the presence of