Biofuel Energy: spent coffee grounds biodiesel, bioethanol and solid fuel
©2014
Textbook
104 Pages
Summary
In this study, the use of waste coffee grounds for biodiesel producution, its solid by-product after oil extraction for bioethanol generation, and the second by-product after bioethanol generation for solid fuel generation is explored. For the study, waste coffee grounds samples were gathered from TOMOCA PLC, Addis Ababa, Ethiopia. The oil was then concentrated utilizing n-hexane and brought about an oil yield of 19.73 %w/w. The biodiesel was acquired by a two-stage process, i.e. acid catalyzed esterification followed by base catalyzed transesterification utilizing catalysts sulfuric acid and sodium hydroxide respectively. The change, after esterification of waste coffee grounds oil into biodiesel, was about 80.4%w/w. Different parameters that are fundamental for biodiesel quality were assessed utilizing the American Standard for Testing Material (ASTM D 6751- 09) and revealed that all quality parameters are inside the extent pointed out aside from acid value. Also, the strong waste staying after oil extraction was researched for conceivable use as a feedstock for the generation of bioethanol and brought about a bioethanol yield of 8.3 %v/v. Moreover, the solid waste staying after bioethanol generation was assessed for solid fuel (20.8 MJ/Kg) applications.
Excerpt
Table Of Contents
8
2.4.4. Reaction Time and Temperature ... 32
2.5. Parameters which define the fuel quality of biodiesel ... 33
2.5.1. Density (15
C) ... 33
2.5.2. Viscosity (40 C) ... 33
2.5.3. Gross calorific value ... 34
2.5.4. Cloud point (CP) ... 35
2.5.5. Cetane Number ... 35
2.5.6. Iodine Value (IV) ... 36
2.5.7. Flash point ... 36
2.5.8. Water and sediment ... 37
2.5.9. Carbon Residue ... 38
2.5.10. Sulfated ash ... 38
2.5.11. Acid value ... 39
2.6. Coffee production and Waste coffee residues ... 39
2.6.1. Coffee production in Ethiopia ... 39
2.6.2. Waste Coffee Residues (WCRs) ... 40
2.6.2.1. Chemical composition of WCR ... 41
2.7. Advantages and Disadvantages of Biodiesel ... 42
3. MATERIALS AND METHODS ... .................................43
3.1. Materials and chemicals ... 43
3.2. Experimental
... 43
3.2.1. Waste coffee residue (WCR) Moisture content Determination ... 43
3.2.2. Waste coffee residue (WCR) oil extraction ... 43
3.2.3. Physicochemical parameters of WCRs oil ... 47
3.2.3.1. Determination of Saponification Value ... 47
9
3.2.3.2. Determination of Peroxide value ... 47
3.2.4. Two-Step Biodiesel Production Process ... 48
3.2.4.1. Acid-catalyzed esterification ... 48
3.2.4.2. Base-catalyzed transesterification ... 49
3.2.4.3. Purification ... 49
3.2.5. Biodiesel yield ... 50
3.2.6. Characterization of WCR Biodiesel ... 50
3.2.6.1.
Determination of specific gravity/density (ASTM D1298) by hydrometer
method...50
3.2.6.2. Determination of Kinematic Viscosity (40 C) ... 51
3.2.6.3. Determination of Acid value ... 52
3.2.6.4. Determination of Gross calorific value ... 52
3.2.6.5. Determination of Cloud point (ASTM D 2500) ... 53
3.2.6.6. Determination of Water and sediment ... 54
3.2.6.7. Determination of Cetane number ... 55
3.2.6.8. Determination of Iodine Value ... 55
3.2.6.9. Determination of flash point by Pensky-Martens closed cup tester ... 56
3.2.6.10. Determination of conradson carbon residue ... 56
3.2.6.11. Determination of Ash content... 57
3.2.6.12. Determination of Copper strip corrosion ... 58
3.2.6.13. Determination of distillation characteristics ... 59
3.2.7. Fatty acid composition of WCR methyl ester ... 60
3.2.8. Production of Bioethanol from the solid waste remaining after oil extraction of WCR
(Spent of WCR) ... 60
3.2.9. Determination of the quality of the solid residue after Bioethanol production for compost
and solid fuel ... 61
10
3.2.9.1. Calorific value ... 61
3.2.9.2. Proximate analysis ... 61
4. RESULTS AND DISCUSSION ... 63
4.1. Oil content of waste coffee residue (WCR) ... 63
4.2. Physicochemical characteristics of the extracted WCR oil ... 64
4.3. Biodiesel yield of WCR oil ... 67
4.4. Waste Coffee Residue methyl ester Fuel properties ... 68
4.4.1. Density (15
C) ... 68
4.4.2. Kinematic viscosity (40 C) ... 69
4.4.3. Gross calorific value ... 69
4.4.4. Cloud point ... 70
4.4.5. Acid value (AV) ... 70
4.4.6. Cetane number ... 72
4.4.7. Iodine Value ... 72
4.4.8. Water and sediment ... 73
4.4.9. Distillation Temperature ... 73
4.4.10. Ash content ... 74
4.4.11. The Conradson Carbon residue of waste coffee residue ester ... 75
4.4.12. Flash point ... 75
4.4.13. Copper corrosion ... 76
4.5. Fatty acid composition of WCR Biodiesel ... 76
4.6. Bioethanol yield from solid waste remaining after oil extraction of WCR (Spent of WCR)77
4.7. Solid fuel and compost from the WCR after Bioethanol production ... 78
4.7.1. Solid waste remaining after Bioethanol production for solid fuel ... 79
4.7.2. Solid waste remaining after Bioethanol production for compost ... 80
11
5. CONCLUSION AND RECOMMENDATIONS ... 81
5.1. Conclusion
... 81
5.2. Recommendations
... 82
REFERENCES ... 83
APPENDICES ... 99
12
List of Tables
Table 2.1: Sector wise energy source utilization percentage distribution ... 24
Table 2.2: Composition of waste coffee residue ... 41
Table 3.1: Standard test methods for physicochemical properties of WCR oil ... 48
Table 3.2: test methods to characterize WCR oil methyl ester/biodiesel ... 54
Table 3.3-Analysis of solid fuel and compost ... 63
Table 4.1 - Moisture and oil contents of WCR ... 64
Table 4.2: Characterization of the oil extracted from waste coffee Residue ... 66
Table 4.3: Characterization of the WCR methyl ester ... 72
Table 4.6: characteristics of WCR after bioethanol production for solid fuel and compost ... 80
13
List of Figures
Figure 1: Scheme of general transesterification reaction ... 26
Figure 2: A typical base-catalyzed process for the production of bio-diesel ... 27
Figure 3: A typical acid-catalyzed process for the production of bio-diesel ... 28
Figure 4: Experimental set up for Soxhlet Extraction ... 44
Figure 5: Rotavapor used to separate hexane from the extracted WCR oil ... 44
Figure 6: WCRs before extraction (left) and after extraction (right) ... 45
Figure 7: General Flow chart of the study ... 46
Figure 8: Transesterification of WCR oil ... 49
Figure 9: During phase separation Purification stage Purified WCR biodiesel ... 50
Figure 10: Cannon- Fenske glass capillary viscometer tube with samples in the SETA KV-8
viscometer bath ... 51
Figure 11: The Peltier device apparatus... 53
Figure 12: Centrifuge for determination of water and sediment ... 55
Figure 13: Pensky- Martens closed cup tester ... 56
Figure 14: Carbon residue test apparatus assembly at pre ignition stage ... 57
Figure 15: The samples in crucible at ignition stage ... 58
Figure 16: Copper Corrosion Apparatus ... 59
Figure 17: Setastill distillation apparatus ... 59
Figure 18: a. Hydrolysis b. Fermentation c. fractional distillation d. FTIR reading ... .42
Figure 19: WCR oil ... 64
Figure 20: Density of WCR ester in relative to biodiesel EN 14214 standard specification ... 68
Figure 21: WCR ester viscosity in comparison with ASTM and EN biodiesel standards ... 69
Figure 22: Acid value of WCR oil and ester in relation with ASTM and EN standards ... 71
Figure 23: cetane number of WCR oil and ester in relation with ASTM and EN standards ... 72
Figure 24: Iodine value of WCR oil and ester in relation with EN standard specification ... 73
14
Figure 25: Distillation temperature of WCR biodiesel in relative to ASTM specification ... 74
Figure 26: WCR ester ash content in comparative to ASTM and EN specifications ... 75
Figure 27: WCR ester flash point in relation to ASTM and EN standard specifications ... 76
Figure 28: WCR methyl ester fatty acid composition ... 77
Figure 29: Bioethanol yield (%) of the solid waste after oil extraction (spent of WCR) ... 77
15
List of equations
Equation 1: Mosture determination ... 43
Equation 2: Waste coffee residue oil content determination ... 44
Equation 3: Determination of saponification value... ................... 47
Equation 4: Determination of peroxide value ... .... 48
Equation 5: Acid pretreatment loss ... ..................................................... 49
Equation 6: Determination of biodiesel yield (%)... ........................... 50
Equation 7: Kinematic Viscosity Determination ... 51
Equation 8: Acid Value Determination ... 52
Equation 9: Determination of calorific value ... 53
Equation 10: Cetane index determination ... 55
Equation 11: Cetane number determination ... 56
Equation 12: Determination of iodine Value ... ......................................................... 56
Equation 13: Corrected flash point ... ................................................................. 56
Equation 14: Carbon residue determination ... ........................................................................... 57
Equation 15: Ash determination ... 58
Equation 16: Determination of Boiling tempratuer... ... 60
Equation 17: Gram of bioethanol ... 61
Equation 18: Yield of bioethanol ... 61
Equation 19: Fixed carbon determination ... ..62
16
List of Appendices
Appendix 1: ASTM D6751-09 Standard Specification for Biodiesel Fuel (B100)... ... 99
Appendix 2: EN 14214 biodiesel fuel standard ... .100
Appendix 3: Fatty acid composition of waste coffee residue oil methyl ester ... ..101
Appendix 4: Gas chromatogram profile of fatty acid methyl ester of WCR ... ....102
Appendix 5: Distillation Characteristics of WCR Methyl Ester ... ..............102
Appendix 6: Bioethanol yield from spent of WCR ... 103
Appendix 7: absorbance reading of spent of WCR bioethanol with distilled water and 1 molar
H2SO4...86
Appendix 8: Proximate analysis of the waste solid after bioethanol production ... 87
Appendix 9: calculations for esterification and transesterification ... 87
Appendix 9.1: calculation for Esterification ... 87
Appendix 9.2: calculation for Transesterification ... 87
17
Acronyms
ASTM American Society for Testing and Materials
AV Acid Value
BD Biodiesel
CN Cetane Number
CP Cloud Point
CV Calorific Value
EN 14214 European Standards for Biodiesel
EPA Environmental Protection Agency
FAME Fatty Acid Methyl Ester
FBP Final Boiling Point
FA
Fatty Acid
FFA Free Fatty Acids
FTIR Flourier Transform Infrared Spectroscopy
GC Gas Chromatography
GHG Green House Gases
IBP Initial Boiling Point
IV Iodine Value
KV Kinematic Viscosity
LPG Liquid Petroleum Gas
MoME Ministry of Mines and Energy
PP Pour Point
Rpm Revolution per minute
S. cerevisiea Saccharomyces cerevisiae
SG Specific Gravity,
ULSD Ultra Low Sulphur Diesel
WCR Waste Coffee Residue
19
1. INTRODUCTION
1.1.
Background and justification
In recent times, the world has confronted with crises of increased demand for energy, price hike of
crude oil, global warming due to emission of green house gases, environmental pollution, and fast
diminishing supply of fossil fuels (Atadashi, et al., 2011; Miguel and Calixto, 2009). The
indiscriminate exploration and consumption of fossil fuels has led to a reduction in petroleum
reserves (Miguel and Calixto, 2009).
Our reliance on these energy sources threatens energy security and influence economic growth
especially in fuel importing countries like Ethiopia. About all of Ethiopia's liquid fuel requirements
are imported in the form of refined petroleum products (Alemayhu, 2007). This external energy
supply is unsteady and has become a burden to the rapidly growing national economy. In addition,
diesel powered motor vehicles in the road transport sector are an important contributor to the total
gas emissions in the urban cities (Christoffel, 2010). From the point of view of global environment
protection and the concern for long-term supplies of conventional diesel fuels, it becomes necessary
to develop alternative fuels comparable with conventional fuels. Alternative fuels should be, not
only sustainable but also environmentally friendly (Miguel and Calixto, 2009). Some of the most
notable alternative sources of energy capable of replacing fuels (Miguel and Calixto, 2009) include
amongst others: water, solar and wind energy, and biofuels (Atadashi et al., 2011). A potential
diesel oil substitute is biodiesel (Miguel and Calixto, 2009).
Biodiesel is a new energy source that has grown in importance over recent years. Nowadays, used
vegetable oils are potential renewable sources for the production of biodiesel as an alternative to
petroleum based diesel fuel, which is derived from diminishing petroleum reserves and which has
environmental consequences caused by the exhaust gases from diesel engines (Maceiras et al.,
2009). Biodiesel has several benefits such as a diminution in greenhouse gas emissions: it reduces
emissions of carbon monoxide by about 50% and emissions of carbon dioxide by about 78%
(Sheehan et al., 2008). In addition, biodiesel is produced from a variety of vegetable oils (such as
soybean, rapeseed and sunflower) and animal fats, and can be used in diesel engines blended with
petroleum diesel or on its own (Sánchez et al., 2012). Researchers are developing certain crops
20
with high oil content just for the production of biodiesel (Azam et al., 2005; Cardone et al., 2003;
Encinar et al., 2002; Gressel, 2008) or looking for new sources to produce biodiesel (Kondamudi et
al., 2008). Therefore, it will be very useful to look for new raw sustainable materials for biodiesel
production that do not involve the use of cereals and plants that compete with land.
Coffee is one of the largest agricultural products that are mainly used for beverages (Kondamudi et
al., 2008) throughout the world and providing approximately 30.6% of Ethiopia's foreign
exchange earnings in 2010-2011 (Bureau of African Affairs, 2012). Ethiopia is currently producing
an estimated 9.804 million 60-kg bags that would rank as the third largest coffee producer in the
world after Brazil and Vietnam (African Commodity Report,
2012) and half of the coffee is
consumed by Ethiopians (Abu, 2012).
Waste coffee residue (WCR), the solid dregs found from the treatment of coffee powder with hot
water to prepare instant coffee, is the main coffee industry residues with a generation of 6 million
tons worldwide (Tokimoto et al., 2005) and 235,296 tons in Ethiopia. According to Kondamudi et
al. (2008), on a worldwide scale, based on the amount of coffee that is used, 340 million gallons of
biodiesel can be produced from Waste coffee residues. Simões (2009) demonstrated that WCR can
be used for the production of biodiesel and fuel pellets and as a source of polysaccharide with
immune stimulatory activity. The amount of oil in the Waste coffee residue source varies from 11
to 20 wt % depending on its types (Arabica and Robusta) (Daglia et al., 2008), which is roughly
equivalent to that of palm, rapeseed, and soybean sources (Kondamudi et al., 2008). Compared to
other waste sources; such as cooking oils, animal fats, and other biomass residues, coffee has the
additional benefits of being less expensive, more stable due to the presence of antioxidants, and
comprising of a nice smell (Al-Hamamre et al., 2012). On average, the Waste coffee residues
comprise 15% oil, by weight, which can be converted to a similar amount of biodiesel using
transesterification methods (Kondamudi et al., 2008).
The biodiesel from waste coffee residues possesses better stability than biodiesel from other
sources due to its high antioxidant content (which hinders the rancimat process) (Campo et al.,
2007; Yanagimoto et al., 2004). WCR is also considered an inexpensive and easily available
adsorbent for the removal of cationic dyes in wastewater treatments (Franca et al., 2009). However,
21
none of these strategies have yet been routinely implemented, and most of these residues remain
unutilized, being discharged to the environment where they cause severe contamination and
environmental pollution problems due to the toxic nature (presence of caffeine, tannins, and
polyphenols) (Leifa et al., 2000). Nowadays, there is great political and social pressure to reduce
the pollution arising from industrial activities. In this sense, conversion of WCR to value-added
compounds is of environmental and economical interest (Mussatto et al., 2011). In this work,
investigation of WCR as a potential raw material for biodiesel production and its by-products for
bioethanol and solid fuel as well as compost was carried out.
1.2.
Problem of the statement
In today's world, alternative fuels are needed more than ever. The primary sources of energy are
mainly non-renewable: natural gas, oil, coal, peat, and conventional nuclear power. These
Conventional fuels are constantly being depleted; however, our dependency on these fuels is still
growing. Additionally, the price on foreign fuels is ever increasing. For these reasons, Ethiopia is
pursuing alternative fuel sources to lessen the dependency on conventional fuel that is petro. One
alternative fuel is biodiesel; biodiesel can be produced from vegetable oil or animal fat and thus can
be used to alleviate the foreign fuel dependency. In order for biodiesel to be a viable alternative fuel
source, a cheap feedstock for biodiesel production process needs to be improved. Compared to
current designs and fossil fuel, the process must be cost competitive.
Ethiopia imports its almost all petroleum fuel requirement and the demand for petroleum fuel is
rising rapidly due to a growing economy and expanding infrastructure (Alemayhu, 2007). Statistics
from the Ethiopian Ministry of Mines and Energy (MoME) indicate that the country spends about
Ethiopian Birr 10 billion (US$800 million) annually to import petroleum products for domestic
consumption. This astounding figure represents nearly 90 percent of the earnings that the country
makes each year in foreign trade. By cutting its dependency on foreign oil, Ethiopia could perhaps
keep some of the money inside the country (Gathanju, 2010).
22
1.3.
Objectives
1.3.1.
General objective
To Investigate the Waste Coffee Residue (WCR) remaining after brewing coffee as a
potential alternative raw material for biodiesel production.
1.3.2.
Specific objectives
¾ To extract oil from WCR remaining after brewing coffee
¾ To analyze Physicochemical parameters of WCR oil that affect the production and
characteristics of the biodiesel produced from the oil
¾ To produce biodiesel from WCR and to analyze its fuel properties such as acid value,
density, kinematic viscosity, iodine value, flash point, cetane number, carbon residue,
water and sediment content, heating value and cloud point, along with the standard test
methods
¾ To determine fatty acid composition of the biodiesel
¾ To evaluate the spent remaining after the oil extraction for possible uses as fuel and
compost
1.4.
Significance of the study
The results of this study will give insight to produce biodiesel from waste materials. Clean energy
for today's economic development is crucial to assure a sustainable development. Hence, the
investigation of waste coffee residue remaining after brewing coffee as a potential alternative raw
material for biodiesel production is very timely because of arising problems such as the rising cost
of fuel in the market, global warming phenomenon, and health problems such as respiratory
diseases caused by the harmful byproducts of burning petroleum-based fuels. Producing a biodiesel
from it will be a good way to minimize GHG and waste in the environment.
23
2.
LITERATURE REVIEW
2.1.Overview of Ethiopia's Energy Sector
Ethiopia is well endowed with a variety of energy and other natural resources. However, much of
the energy resource available has yet to be exploited. The renewable energy resources with
potential include biomass, hydropower, and alternative forms of energy-solar, wind and geothermal
energy. There are also considerable reserves of coal and natural gas (W/Giorgis, 2004).
Most people living in Ethiopia have, until now, been unable to satisfy their household energy
requirements with modern energy sources (kerosene, electricity, gas). In rural areas they use only
biomass (wood, dung or agricultural waste) for cooking, baking and heating. The biomass energy
consumption is estimated about 94% of the total. The low agricultural production is a consequence
of deforestation, erosion and desertification. On the other hand petroleum products which are used
mainly at urban household center are entirely an imported commodity. Demand for these products
is rising rapidly increasing due to in scarcity of fuel wood and the change of life style of the people.
The rise in demand is accompanied by a much faster growth in the import bill because of rising
petroleum prices and products (Alemayhu, 2007).
In Ethiopia the gross available potential land for production of feedstock for biodiesel is estimated
about 23,305,890 hectares and the total irrigable land for sugarcane production for ethanol
production is about 700,000 hectares. Thus Ethiopia has a potential to produce 1billion liters of
ethanol within available suitable land (Alemayhu, 2007). The major use of energy, about 89% of
the overall energy consumption in the country, is the households. The second most important sector
in terms of energy consumption is industry (4.5%) followed by services and others (3.6%) while
agriculture and transport were attributed to the remaining 2.3%. The consumption of energy is
directly related to the availability of energy source, the size of the population and the price
(Ministry of mines and energy, 2011).Table 2.1 shows the sector-wise percentage usage distribution
of energy source type in Ethiopia.
24
Table 2.1: Sector wise energy source utilization percentage distribution
Sectors
Energy source
Biomass (%)
Petroleum (%)
Electricity (%)
Households
98.6
1.1
0.3
Industry
75.7
17.3
7
Services
94.3
1.3
4.4
Transport
-
100
-
Agriculture -
100
-
Source: (Meskir, 2007; Ministry of mines and energy, 2011)
2.2.
Introduction to biodiesel
Biodiesel is defined as "a substitute for, or an additive to diesel fuel that is derived from the oils and
fats of plants and animals" (Ma and Hanna, 1999) or a fuel composed of monoalkyl esters of long-
chain fatty acids (Abreu et al., 2004; Hass et al., 2001) produced by transesterification reaction of
vegetable oils and animal fats with short chain alcohols meeting the requirements of ASTM D6751
(ASTM, 2008; Burtis,2006; Encinar et al., 2002; Noureddini et al.,1998). The alcohol and the base
compound (lye) are used to split vegetable oil into components. The ester component is what is
known as biodiesel, while the separated by-product is glycerin (Alberta, 2006). Glycerin has value
as a co-product and can be used in soaps, lotions, and as a lubricant (Sawyer, 2007). Biodiesel is a
form of biofuel that is a nontoxic, biodegradable substance and does not contain any sulfur
(Alberta, 2006). It is an alternative to diesel fuel produced from domestic renewable resources.
Typically biodiesel derived from the oils and fats of that of sunflowers, soybean, canola, and
rapeseeds, can be used in diesel engines with no to little modifications (Liu et al., 2010).
Similar to diesel, biodiesel can function as an alternative to electricity and petroleum diesel.
Because its components are derived from renewable resource and has a lower emission compared to
the traditional petroleum fuel, biodiesel is environment-friendly. With every one unit of needed
energy to generate biodiesel, in turn, 4.5 units of energy is return. This is due to biodiesel having a
high-energy balance and is locally produced (National Biodiesel Board, 2010).
25
2.3.Biodiesel production
Bio-diesel production is a very modern and technological area for researchers due to the relevance
that it is winning everyday because of the increase in the petroleum price and the environmental
advantages (Marchetti et al., 2005). The most common method of producing bio-diesel is the
reaction of vegetable oils and animal fats with alcohol mainly methanol in the presence of catalyst.
This process is called transesterification and is not a new process. It was conducted as early as 1853
by two scientists E. Duffy and J. Patrick. Since that time several studies have been carried out using
different oils such as soybean (Watanabe et al., 2002), rapeseed (Kusdiana and Saka, 2001), cotton
seed (Royon et al.2007), waste cooking (Zhang et al., 2003), spent coffee ground (Daglia el al.,
2008; Kondamudi et al., 2008),sunÀower seed (Harrington and D'Arcy-Evans,1985) , winter rape
(Peterson et al., 1991), different alcohols such as methanol (Demirbas, 2006), ethanol (Encinar et
al., 2002).
2.3.1.
The Transesterification (alcoholysis) Process of Biodiesel
The vegetable oils and animal fats usually contain free fatty acids, phospholipids, sterols, high
viscosity, water, odourants and other impurities. Because of these, direct use of these vegetables
and animal fats oil as fuel for diesel engine can cause particle agglomeration, injector fouling due to
its low volatility and high viscosity, which is about 10 to 20 times greater than petroleum diesel
(Fan, 2008). To reduce these problems the oil requires chemical modification principally through
transesterification, pyrolysis and emulsification (Ma and Hanna, 1999). Among these, the
transesterification is the main and fore most important step to produce the cleaner and
environmentally safe fuel from vegetable oils (Knothe and van Gerpen, 2005; Meher et al., 2004).
Additionally, the physical properties of biodiesel produced by this simple process are very close to
the petroleum diesel fuel (Fan, 2008).
Transesterification is the general term used to describe the important class of organic reactions
where an ester is transformed into another through interchange of the alkoxy moiety (Freedman et
al., 1986). It is the reaction of vegetable oil or animal fat with an alcohol, in most cases methanol,
to form esters and glycerol. According to Srivastava Prasad (2000) transesterification is the
displacement of alcohol from an ester by another alcohol in a process similar to hydrolysis, except
26
that alcohol is employed instead of water. The transesterification reaction is affected by alcohol
type, molar ratio of glycerides to alcohol, type and amount of catalyst, reaction temperature,
reaction time and free fatty acids and water content of vegetable oils or animal fats. The
transesterification process consists of a sequence of three consecutive reversible reactions, which
include conversion of triglycerides to diglycerides, followed by the conversion of diglycerides to
monoglycerides. The glycerides are converted into glycerol and yield one ester molecule in each
step.
Fig. 1: Scheme of general transesterification reaction (source: Ma and Hanna, 1999).
2.3.1.1.Catalytic transesterification
Catalytic transesterification is the process by which different catalysts are used to initiate the
esterification for making biodiesel. Also known as methanolysis, this process is well studied and
established (Helwani et al. 2009). The three basic Catalysts of biodiesel production from oils/fats
are the base-catalyzed transesterification, the acid catalyzed esterification, and enzymatic catalysis
(Kaieda et al., 1999; Haas et al., 2006; Ma and Hanna, 1999; Meher et al., 2006). Among these
base-catalyzed transesterification is involved in biodiesel production today (Srivastava and Prasad,
2000; Zhang et al., 2003), where feedstocks with a high water or free fatty acid (FFA) content
needs pretreatment with an acidic catalyst in order to esterify FFA (Freedman et al., 1984; Kaieda
et al., 1999).This is the most common method done because it is the most economical (Singh et al,
2006).
2.3.1.1.1.
Base-Catalyzed transesterification
Base-catalyzed transesterification involves stripping the glycerin from the fatty acids with a catalyst
such as sodium or potassium hydroxide and replacing it with an anhydrous alcohol, usually
methanol. The resulting raw product is then centrifuged and washed with water to cleanse it of
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form alkyl e
ercially as i
es; produces
ate compoun
et al., 1984;
d KOH (Kor
of sodium m
able, are t
).
g which are
roduct (Dem
nd water (C
l should ha
an 0.3% (W
at the proce
ved from the
se-catalyzed
mmed, 2011).
2
of glycerol,
ucts (Refaa
ester is faste
t is the mo
s over 98 %
nds; also, n
Singh et al
rytkowska e
methoxide o
he preferre
e removal o
mirbas, 2003
anakci et al
ave free aci
Wright et al
ess is energ
e product an
d process fo
7
a
at,
er
st
%
no
l.,
et
or
ed
of
3;
l.,
id
l.,
gy
nd
or
28
2.3
Acid-ca
tempera
conduct
procedu
refluxed
process
hydroch
1990). A
acid ca
tempera
proporti
ester for
ratio of
value at
feedstoc
relativel
Fig. 3: A
2.3
Enzyme
do bette
biodiese
2005; D
variety
3.1.1.2.
Ac
atalyzed tran
ature is usua
ted under h
ure of acid-c
d at or near
is catalyz
hloric (Lee
A simplified
atalyzed rea
atures and p
ionally incre
rmation sha
f 6:1. Highe
t a 30:1 ratio
ck, acid-cat
ly slower re
typical acid-
3.1.1.3.
E
e-Catalyzed
er than chem
el productio
De Oliveira e
of substrate
cid-Catalyz
nsesterificat
ally above 1
high temper
catalyzed tra
the boiling
zed by sulf
et al., 2000
d block flow
actions are
pressures, a
ease with m
arply improv
er molar rat
o (98.4%) (
talyzed tran
eaction rate
-catalyzed pro
nzyme-Cat
Transesteri
mical cataly
on, based on
et al., 2004
es such as r
zed Transes
tion is slow
100 °C and
rature and
ansesterifica
point of the
furic (Goff
0; Goff et a
w diagram o
performed
and high ac
molar ratio. F
ved from 77
tios showed
(Lotero et a
nsesterifica
(Zhang et
a
ocess for the p
talyzed Tra
ification is
ysts for biod
n the use o
; Noureddin
rice bran oil
sterification
wer than ba
reaction tim
pressure (A
ation is diff
e mixture of
f et al., 20
al., 2004), a
f the acid-c
d at high a
cid catalyst
For instance
7% using a
d only mode
l., 2006). D
tion has b
al., 2003).
production of
ansesterific
gaining mo
diesel produ
of enzymes,
ni et al., 200
l, canola, su
n
ase-catalyze
me is 3 to 48
Allen et al
ferent from
f cosolvent
004; Liu et
and organic
atalyzed pro
alcohol-to-o
concentrati
e, for soybea
methanol-to
erate impro
Despite its in
been largely
f bio-diesel (s
ation
re attention
uction in the
, have beco
05). Most o
unflower oi
ed transeste
8 hours exc
l. 1945; Ta
base-cataly
and alcohol
t al., 2006
c sulfonic a
ocess is sho
oil molar r
ions. Howev
an methanol
o-oil ratio o
vement unt
nsensitivity
y ignored
source; Moham
n nowadays
e future. New
ome very in
f the article
l, soybean o
erification. T
cept when th
aylor et al.
zed one. Th
l. The transe
; Lopez et
cids (Stern
own in Fig. 3
ratios, low-
ver, ester y
lysis using s
of 3.3:1 to 8
til reaching
to free fatty
mainly bec
mmed, 2011).
and has the
w biochemi
nteresting (C
es published
oil, olive oi
The reactio
he reaction i
1927). Th
he reaction i
esterificatio
t al., 2005
and Hillion
3. In genera
-to moderat
yields do no
sulfuric acid
87.8% with
a maximum
y acids in th
cause of it
e potential t
ical routes t
Chang et al
d have used
il, and casto
on
is
he
is
on
),
n,
al,
te
ot
d,
a
m
he
ts
to
to
l.,
a
or
29
oil. Several lipases from microbial strains, including Candida Antarctica (Lai et al., 2005; Royon et
al., 2007), Candida rugasa (Chen and Wu, 2003; Linko et al., 1998), Pseudomonas cepacia (Deng
et al., 2005; Shah and Gupta; 2007), Thermomyces lanuginosus (Xu et al.,2004), Pseudomonas sp.
(Lai et al., 1999), and Rhizomucor miehei (Lai et al., 1999; Skagerlind et al.,1995) have been
reported to have transesterification activity. The enzymatic alcoholysis of soybean oil with
methanol and ethanol was investigated using a commercial, immobilized lipase (Bernardes et al.,
2007; De et al., 2006). In that study, the best conditions were obtained in a solvent-free system with
ethanol/oil molar ratio of 3.0, temperature of 50 °C, and enzyme concentration of 7.0% (w/ w).
They obtained yield 60% after 1 h of reaction.
The advantages of lipase-catalyzed transesterification, compared to the chemically-catalyzed
reaction, are emphasized and can be reused without separation (Nelson et al., 1996; Shimada et al.,
2002). Also, the operating temperature of the process is low (50 °C) compared to other techniques
(Nelson et al., 1996; Shimada et al., 2002). The main problem of the lipase-catalyzed process is the
high cost of the lipases used as catalyst (Royon et al., 2007) and inhibition effects which were
observed when methanol was used (Nelson et al., 1996; Shimada et al., 2002).
2.4.Variables Affecting the Transesterification Process
There are number of factors which could affect the transesterification process. These factors include
moisture content, free fatty acid contents, molar ratio of oil to alcohol, type and amount of catalyst,
reaction time, reaction temperature, mixing intensity, and co-solvent (Demirbas, 2007; Ma
Hanna, 1999; Meher et al., 2006; Sharma et al., 2008). These factors or variables usually have
different effect on the transesterification process depending on the method used for the
transesterification process. The effects of these factors are described below.
2.4.1.
Effect of free fatty acids (FFA) and moisture
The free fatty acids (FFA) and moisture contents are two key parameters for determining the
viability of the feedstock (vegetable oil) transesterification process (Meher et al., 2006). In the
transesterification, FFAs and water always produce negative effects, since the presence of FFAs
and water causes soap formation, consumes catalyst and reduces catalyst effectiveness, all of which
Details
- Pages
- Type of Edition
- Erstausgabe
- Publication Year
- 2014
- ISBN (eBook)
- 9783954898053
- ISBN (Softcover)
- 9783954893058
- File size
- 4.4 MB
- Language
- English
- Publication date
- 2014 (August)
- Keywords
- biofuel energy
- Product Safety
- Anchor Academic Publishing
