DIRECT TRANSESTERIFICATION FOR BIODIESEL EXTRACTION FROM
MICRO-ALGAL BIOMASS: A REVIEW
Rahul Chamola
Assistant Professor,Department of Mechanical Engineering
Dev Bhoomi Institute of Technology Dehradun-248007
Uttarakhand, India
Ayush Gupta
Assistant Professor,Department of Mechanical Engineering
Dev Bhoomi Institute of Technology Dehradun-248007
Uttarakhand, India
Vijay Singh Chauhan
Assistant Professor,Department of Mechanical Engineering
Dev Bhoomi Institute of Technology Dehradun-248007
Uttarakhand, India
Tirath Singh
Assistant Professor,Department of Mechanical Engineering
Dev Bhoomi Institute of Technology Dehradun-248007
Uttarakhand, India
Abstract
The biodiesel production has gone through fast growth over the
past decade. Microalgae have large scale cultivation resources.
The non edible biodiesel resources have potential to meet the
future energy demand without any environmental loss. Despite
the umpteen advantages microalgal biodiesel is still facing
technical and economical challenges. The complexity and the
production cost related issues have been studied by many
researches and scholars all over the globe for the optimum
biodiesel extraction. This article reviews about the recent
development and process parameters affecting the biodiesel
production by insitu-transesterification. This article also
reviews about the recent techniques which are being used for
large scale production.
It has been studied that insitu transesterification is being used
for economic production of bio fuels and the process
parameters viz. reaction temperature, reaction time, types of
catalyst and methanol to algae ratio play a significant role in
commercial biodiesel production.
There is a focus on insitu transesterification which is most
efficient and economic oil production process for wet as well
as dry micro-algal biomass. Furthermore, all other issues
related to the biodiesel production such as viscosity purification
and processing time are taken into consideration.
Keywords: microalgae, innovation in biodiesel extraction,
insitu transesterification, Biofuel Non-edible feedstock,
1. Introduction
Biodiesel is derived from vegetables oil has a great potential as
a substitute of diesel fuels. Biofuels are generated from mainly
two sources namely edible and non edible biofuels. Edible
biodiesel resources are usually employed for maximum
biodiesel extraction. Almost 95% of world's total biodiesel is
produced from edible biodiesel resources. However, edible
biodiesel resources such as soybean, rapeseeds, sunflower and
palm oil are associated with sever environmental problems like
deforestation, vital land availability and climate change[1]. The
limitations of edible resources can be minimized by the
introduction of non-edible biodiesel resources viz. Jatropha
Curcas, neem seeds, mahua and algae. Algae are kept in the
category of third generation biofuel resources. These resources
are most efficient and eco-friendly and excessively being
adopted as sustainable future fuels.
Algae are plant like organism without true roots, leaves and
vascular bundle. They can be collected from different aquatic
bodies such as pond, river and sea. Algae are of two types
namely microalgae and macroalgae. Microalgae available in
the size of micro to nano metre and known as single cell
organisms[2]. Macroalgae on the other hand are known as
seaweeds available in the size of 60 to 150 m in length.
2. Material and Method
Various biodiesel extraction techniques have been introduced
by the research scholars some of them are pyrolysis,
gasification, micro-emulsification, two-step transesterification,
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 9, 2019 (Special Issue) © Research India Publications. http://www.ripublication.com
Page 180 of 184
super critical transesterification and insitu transesterification.
Out of these techniques insitu transesterification is the most
useful economic and efficient process for biofuel generation
from biomass. It is a chemical reaction in which triglyceride
reacts with an alcohol in presence of homogenous or
heterogeneous to produce free fatty alkyl ester (FFEAs). The
transesterification reaction is shown below.
Alcoholic Group + Triglycerides = Glycerol + Fatty Methyl
Esters
Where R', R'' are alkyl groups [3].
3. Types of Transesterification
Commonly known Transesterification techniques are base
catalyst, acid catalyst, enzyme catalyst and supercritical
transesterification. Base catalyst method is broadly used for oil
generation. It can't be reuse or recycled. It has been found that
acid catalysts are slower than that of base catalyst and most
suitable for high lipid containing oil. Enzyme catalyst
technique is technique laborious in process and not useful for
commercial production of biodiesel. Talking about
supercritical transesterification high temperature around 250°C
and pressure is required for the oil extraction. In this process
use of catalyst is optional.
Numerous researches have been reported on transesterification
process. Chamola R et al.[4] have been conducted insitu
transesterification of dry algae with Methanol, acid catalyst
(H2SO4) and base catalyst (NaOH). they found that acid catalyst
has significant role in biodiesel extraction than that of base
catalyst, reported maximum yields of 89.58% and 87.42% for
acid and base catalyst respectively at 50°C in 60.4 min. Shirazi
et al.[5] have been conducted insitu transesterification of dry
algae with methanol, hexane and moisture content. 99.32%
yields have been reported by using Response Surface
Methodology (RSM) and Centre Deviation Method (CDM).
A Salam et al.[6] have worked with marine as well as fresh
water microalgae for biodiesel generation. They used methanol,
hexane and different catalyst to reduce the cost of the biodiesel
production. Velasquez Orta and Harvey[7] conducted a
research on chlorella Vulgaris oil in presence of methanol and
a suitable catalyst. They claimed 77.6% yield with methanol to
oil ratio 600. 94.9% fatty acid methyl ester (FAMEs) is
obtained by Dong et al.[8] during two step transesterification
and direct transesterification using amberlyst-15 and base
catalyst. Spirulina Chlorella and pond water algae have been
applied by Nautiyal et al.[9] for the oil extraction through
transesterification process. It has been suggested that hexane
could be better solvent for high yield.
Im et al.[10] reported biodiesel yield using supercritical
transesterification with chloroform ethanol and H2SO4. They
studied the involvement of moisture content decreases the
output values. Transesterification of dry algae using solvents
viz. n butanol, chloroform, ethyl ether, hexane, acetone and
petroleum to check which has vital role on the output yield for
oil production. Zhang et al.[11] found that n hexane and
petroleum ether are best solvent due to miscibility with
alcoholic products. Kaism and Harvey [12] performed
transesterification on jatropha curcus using alkali catalyst at
60°C. They reported maximum FAME yield of 95%. A
research has been conducted by Hass and Wangner [13] using
wet biomass and acid catalyst at 65°C. Maximum yield of 96%
was recorded with methanol/oil ratio 308:1.
3. Process Parameters in Insitu Transesterification Process
Direct transesterication crucially depends upon process
parameters like processing time, processing temperature,
methanol/algae ratio and catalyst concentration. some of the
study has take processing time in between 60 to 180 min and
operating temperature range is suggested in between 60 to
80°C[14].
Effective methanol/algae ratio has been suggested as (8% to
20%)(W/W). Batch reactor is used to extract biodiesel from
algal biomass which takes lots of steps are listed below in flow
chart[15].
Fig 3:- Flow-Chart for Biodiesel Extraction
Experimental procedures were done in a batch reactor as shown
in the figure. The reactor was heated with an electric heater at
COLLECTION
CLEANING
DRYING
CRUSHING
PARAMETERS SELECTION
INSTRUMENT PREPARATION
TRANSESTRIFICATION
SEPARATION
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 9, 2019 (Special Issue) © Research India Publications. http://www.ripublication.com
Page 181 of 184
a constant temperature was sensed by a thermocouple. in a
batch reactor mixture of methanol, algae, n-hexane and
chloroform is prepared by weighing in chemical balance. A
magnetic stirrer is used for the proper agitation and heat
transfer rate along with a condenser.
According to research analysis, Oil production experiments are
mostly decided by Response Surface Methodology (RSM) and
Central Composite Design(CCD) through design expert
software 11. The software has analysis of variance (ANOVA)
feature to establish the statistical significance of process
parameters on the output. the optimization is also conducted
through the software in order to choose process variables to
optimize the production yield.
Fig 4:- Diagram of Reactor [4]
statistical analysis is done by using regression equation,
generated by the software. furthermore, gas chromatography (G
C) is used to optimized the experimental samples. the process
is processed for 30 minutes at 230°C with nitrogen as a carrier
gas. study shows that G C analysis was performed by many
research scholar using European standard EN 14103:2003.
equation mentioned below is used to calculate the yield and
stock solution i.e., Methyl heptadecanoate and n-heptane is
used to determine the FFA content.
% of ME = ∑𝑨−𝑨𝑬𝑰
𝑨𝑬𝑰∗
𝑪𝑬𝑰− 𝑽𝑬𝑰
𝒎∗ 100
Where,
∑A - Total peak area from the methyl ester in C14 to that in
C24:1;
AEI- Peak area corresponding to methyl heptadecanoate;
CEI - Concentration of the methyl heptadecanoate solution (mg/
ml);
VEI - Volume of the methyl heptadecanoate solution (ml);
m - Mass of the sample (mg).
4. Factors Affecting Insitu Transesterication Process
FAME yields are influenced by the wet and dry algal biomass,
reaction temperature, biomass grain size, agitation speed,
reaction time and catalyst selection during insitu
transesterification process.
4.1 Effect of Moisture Content
Some of the studies show that the output results are good with
dry algae biomass. Actually the availability of water leads
hydrolysis and as a result of which biodiesel disintegrates from
solvent. Hass et al.[16] conducted a study on transesterification
of soybean with 0% and 2.6% water content. They concluded
that methanol consumption increased from 40% to 60% for dry
and wet biomass respectively.
4.2 Effect of Biomass Particle Size
Biomass grain size has an important role in the consumption of
solvent. Scholars have notes that as the particle size increases
less solvent is required for the oil extraction. Methanol-to-dry
algae ratio has crucial impact on the transesterification. Patil et
al.[17] reported 85.75% of yield at 250°C in 30 minutes for wet
biomass of Nannochloris. 5.82% methyl ester yield is collected
in the processing of wet chlorella biomass (75% moisture) with
methanol to dry algae ratio of 8:1.
4.3 Effect of Co-Solvent for the Process
Hexane and chloroform is most widely used co-solvent for the
transesterification method. Hexane and chloroform improves
the solubility of oil and enhance the output[18]. Hexane is
preferred over chloroform because of its cost and availability.
4.4 Selection of Catalyst for the Oil Extraction
As it is already has been discussed that homogenous as well as
heterogeneous catalyst can be used for the biofuel production.
Selection of catalyst should be proper because it helps in
fragmentation of hard micro-algae cell wall. NaOH, KOH,
Ca(OH)2, Mg(OH)2, H2SO4, NaOCH3 and HCl are some
homogenous catalysts are being used by many researchers[19].
Furthermore, homogenous catalyst can be divided into two
categories acidic and basic. Studies showed that H2SO4 and
HCl are most effective for utmost output.
Commonly known heterogeneous catalyst are CaO, MgO,
BaO, SrO, SrCO3 and MgCO3[20]. According to some study
both catalysts are outstanding to boost the oil production with
the increase in consumption.
4.5 Effect of Agitation
Sivaramkrishnan and muthu kumar [21] reported as mixing
speed increases from 150 to 180 rpm FAME also increase.
They also suggested that output value doesn't changes with
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 9, 2019 (Special Issue) © Research India Publications. http://www.ripublication.com
Page 182 of 184
exceeding the mixing speed more than 450rpm.
4.6 Effect of Reaction Time and Temperature
It has been observed that reaction time for oil production is kept
in a particular range from 60 to 180 min. Qian et al.[22] have
conducted transesterification of rapeseed oil for 5 hour and they
achieved output yield of 98% . They concluded that high
reaction time doesn't affect product yield. The best yield results
are obtained for the range of 1 to 3 hours. Temperature on the
other hand increases the solubility and high temperature
reduces the viscosity of vegetable oil. According to a study
when temperature changes from 35 to 55°C almost double
value of output is obtained.
5. Conclusion
Recent developments in the insitu transesterification have been
reviewed. The present study was emphasized on the use of
direct transesterification for the sustainable development of fast
and economic biodiesel extraction process. The numerous
studies showed that the exploitation of edible biodiesel
resources can be compensated by the application of micro-
algae because of high grade oil and widely abundant.
The research data indicated that direct transesterification
resulted in maximum yields for FAEEs. In this case of insitu
transesterification with methanol and ethanol almost equal
yields are received but use of ethanol is a more economic, eco-
friendly and efficient pathway. It was further observed that
process variable had significant role on output. A comparison
study of conventional process and insitu transesterification is
discussed in this research.
5.1 Future Scope
Microalgal biomass can be directly processed using a suitable
catalyst and an alcohol in a batch reactor. Direct
transesterification as the name implies, used to convert
vegetable oil into fuel in one step. Mass production for
commercial applications, oil purification and upgrading of fuel
requires future attention and research.
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