A
Environment Report
On
EFFLUENT TREATMENT PLANT
Dairy
Submitted By
MR. PUSHKRAJ JADHAV
DEPARTMENT OF MECHANICAL ENGINEERING
TATYASAHEB KORE INSTITUTE OF ENGINEERING & TECHNOLOGY,
WARANANAGAR-416113
2006-2007
TATYASAHEB KORE INSTITUTE OF ENGINEERING
& TECHNOLOGY, WARANANAGAR-416113
DEPARTMENT OF CHEMICAL ENGINEERING
CERTIFICATE
This is certify that project report entitled
“BIO-DIESEL”
It is bonafied work of Mr. SHASHIKANT H. NIKAM In the
practical fulfillment of the requirements for the award of degree
of bachelor of Engineering in Chemical Engineering of the
Shivaji university, Kolhapur.
He has carried out the work under my supervision and guidance,
during academic year 2006-07
Prof. B. R. Bagane,
Examiner
(Supervisior)
Prof. S. V. ANEKAR
(H.O.D.)
Department of Chem
Dr. C. R. Rao
(Principal)
ACKNOWLEDGEMENT
It gives me an immense pleasure to present a report on the successful
completion of my Environmental Science Report On
“BIO-DIESEL”
We express my deep sense of gratitude to my guide Prof. B. R.
Bagane for his valuable guidance rendered in all phase of project. We are
thankful for his wholehearted assistance, advice and expert guidance
towards making our project a success.
Our special thanks to honorable Principal Dr. C. R. Rao & Head of
Department Prof. S. V. ANEKAR for their keen interest, encourage and
excellent support.
We are also like to express my thanks to all of other staff members of
college & friends who helped me directly & indirectly during the completion
of this Report.
MR. SHASHIKANT H. NIKAM
DECLARATION
The Principal,
Tatyasaheb Kore Institute of Engineering and Technology,
Warananagar-416113.
Sir,
We undersigned hereby declare that the project report entitled “BIODIESEL”. Written & Submitted by us under the guidance of Prof. B.R.Bagane in
my original work.
The empirical findings in this report are based on the data collected by
ourself. The matter collected in this report is not a reproduction from any source.
We understand that, any such copying is liable to be punished in a way
the institute authorities claim fit.
Place: -Warananagar
Date:-
MR. SHASHIKANT H. NIKAM
INDEX
Sr. No.
Contents
Page No.
1.
Introduction
1
2.
Bio-Diesel As An Option For Energy Security
3
3.
Chemistry of Bio-Diesel
5
4.
Bio-Diesel Processing
19
5.
Storage of Bio-Diesel
37
6.
Specification of Bio-Diesel
39
7.
Emission Norms
40
8.
Advantages of Bio-Diesel
44
INTRODUCTION
The use of vegetable oils as diesel fuel is nearly as old as the diesel engine itself.
The
Fuel and energy crisis and the concern of society for depleting world’s non-
renewable resources initiates various sectors to look for alternative fuels. One of the
most promising fuel alternative is the vegetable oils and their derivatives. Hundreds of
scientific articles and research activities from around the world were printed and
recorded. Oils from coconut, soy bean, sunflower, safflower, peanut, linseed and palm
were used depending on what country they grow abundantly. In the Philippines alone,
research activities on the use of vegetable oils as fuel substitute have already been done
as early as the 1970s using coconut oil. In the United States, the primary interest as
biodiesel source is soy bean oil while many European countries are concerned with rape
seed oil and countries with tropical climate prefer to utilize coconut oil or palm oil.
Several problems encountered cause delay in the widespread use of biodiesel. First is
economics and second is the properties of biodiesel. Use of neat vegetable oils cause
injector coking, engine deposits, ring sticking and thickening of the engine lubricant.
To overcome this problem, various modifications of vegetable oils were suggested such
as by transesterification, micro-emulsion formation and the use of viscosity reducers.
Among
these, transesterification was considered as the most suitable modification
because technical properties of esters are nearly similar to diesel.
What is Biodiesel?
The term Biodiesel, in general, refers to neat vegetable oils used as diesel fuel as well as
neat methyl esters prepared from vegetable oils or animal fats and even blends of
conventional diesel fuel with vegetable oils or methyl esters. Due to problems
encountered in the use of neat vegetable oil, Biodiesel is now referred to as the mono
alkyl esters of long chain fatty acids derived from vegetable oils for use in compression
ignition (diesel) engines. Methyl ester is usually made from 80-90% vegetable oil, 1020% alcohol and 0.35-1.5% catalyst.
Why Use Biodiesel?
Biodiesel fuel is reliable, renewable, biodegradable and non-toxic. It is less harmful to
the environment for it contains practically no sulfur and substantially reduce emissions of
unburned hydrocarbon, carbon monoxide, sulfates, polycyclic aromatic and particulate
matter.
It has fuel properties comparable to mineral diesel and because of great
similarity, it can be mixed with mineral oil and used in standard diesel engines with
minor or no modifications at all. Biodiesel works well with new technologies such as
catalysts , particulate traps and exhaust gas re-circulation. It can be produced from any
kind of oil both vegetable and animal source . Used frying oil can also be used and ,
therefore, be a very promising alternative for waste treatment.
Being an agricultural product, all countries have the ability to produce and control this
energy source which is a situation very different to the crude oil business.
It can
strengthen economy by creating more jobs and create independence from the imported
depleting commodity petroleum.
supporting agriculture.
It can also be used as a way of stimulating and
BIO-DIESEL AS AN OPTION FOR ENERGY SECURITY
With petroleum product prices rising steadily; diesel alone has become 25 per cent
costlier over the last year. Apart from the search for alternatives, it is the need to achieve
energy independence that is directing so much focus on biofuels and the crops that will
help yield these oils. If sugar mills are being encouraged to produce ethanol from
sugarcane for blending with petrol, efforts are on to cultivate such crops as jatropha and
pongamia, which yield oil that can either be blended with diesel or used independently.
BIOFUELS, ethanol, jatropha, pongamia... Words till recently rarely mentioned outside a
select circle are coming into common usage now. The reasons are not difficult to fathom:
Petroleum product prices have been rising steadily; diesel alone has become 25 per cent
costlier over the last year. Apart from the search for alternatives, it is the need to achieve
energy independence that is directing so much focus on biofuels and the crops that will
help yield these oils.
Sugar mills are being encouraged to produce ethanol from sugarcane for blending with
petrol, while efforts are on to cultivate such crops as jatropha and pongamia, which yield
oil that can either be blended with diesel or used by themselves instead.
Much potential
While jatropha has clearly emerged as the preferred option for cultivation, pongamia, a
traditional species that has been around for ages, too has great potential. The advantage
with jatropha, a bush, is that it is easy to maintain and starts yielding from the fourth year,
while pongamia, a tree, requires more area and yields can be expected from the seventh
or eighth year on. Scientists, however, say that the Botanical Survey of India has
identified more than 400 species of plants and trees that can yield such oils.
The enthusiasm for biofuels must also be viewed against the backdrop of the country's
thirst for oil — about 114 million tonnes every year — 75 per cent of which is imported
at a cost of Rs 1,20,000 crore. About 112 million tonnes of oil is consumed just by the
transportation sector. Experts feel that the problem of the huge oil import bill and the
price uncertainty can be mitigated by cultivating biofuel crops on the over 60 million
hectares of wasteland available in the country.
Each hectare would yield up to three tonnes of seed, from which can be extracted one
tonne of oil. This would translate to 30 million tonnes of oil.
The problem is that these estimates represent a theoretical potential, say the National
Bank for Agriculture and Rural Development and commercial banks. Studies are still at
the academic level and banks need large-scale field data before they will commit funds.
Even the economics of cultivating jatropha and the unit cost analysis available with
banks are based on preliminary estimates by research institutes. Banks are for now only
willing to wait and watch and have not extended any loans for jatropha cultivation.
CHEMISTRY OF BIODIESEL
The topic of biodiesel can be introduced in a variety of classes – chemistry,
biology .Engineers in today’s world need to also focus on issues such as making their
processes and products economical, and looking into related political issues, biodiesel
presents an excellent example for students learning how science topics relate to nonscientific fields.
I. Biology
Being produced from biological matter, there are several options for topics that
could be introduced or elaborated on through a discussion of biodiesel. The following are
a few possibilities.
I. a. Carbon Cycle
The carbon cycle is a topic that many students – even a majority of adults – have
difficulty understanding. Our UNH Biodiesel Group has given many presentations to
legislators, members of the general public, students, and scientists. We have found that a
discussion of how the carbon cycle works for biodiesel is very successful in engendering
a better understanding of the carbon cycle in general.
With regard to alternative fuels, the main importance of the carbon cycle is
whether it is a closed or open cycle. Any fuel produced entirely from biomass would have
a closed carbon cycle – since all of the carbon within the fuel came from the plants from
which it was produced, and the carbon in the plants came from the atmosphere. As
Figure 1 shows, plants get their carbon from CO2 in the atmosphere – converting the CO2
to O2 during photosynthesis, with the carbon being stored in the plant (as carbohydrates,
oils, starch, etc.). Photosynthesis is the process by which plants convert carbon dioxide
and water into glucose and oxygen, in the presence of chlorophyll and sunlight (which
supplies the energy). In energy terms, the plants are converting the electromagnetic
energy (sunlight) into chemical energy (glucose).
CO2
2
The glucose can then be converted into other forms by the plant – other sugars, or
fats, starches, proteins (which also requires nitrogen and sometimes sulfur), and so on.
Plants can get everything they need to make sugars, oil, and starches from the air (CO2),
sunlight, and water (H2O). That’s because those molecules are made only of carbon,
hydrogen, and water. As far as the carbon cycle, the important point is that all of the
carbon within a plant comes from carbon dioxide in the air.
If the plant decays, much of that carbon finds its way back into the atmosphere as
CO2 or methane (CH4). If the oil is extracted from the plant, and turned into biodiesel (the
alcohol used to make the biodiesel could come from alcohol also made from the plant),
all of the carbon in the biodiesel had to come from CO2 in the air. So, when we burn
biodiesel, even though it gives off CO2, there is no net addition to atmospheric carbon
(CO2) levels, since that same carbon we are releasing was taken from the atmosphere by
the plants when they were growing.
Contrast this to the carbon released when we burn any fossil fuels. The carbon in
gasoline, for example, is from the petroleum we extract out of the ground. That carbon
itself was likely in the atmosphere at one point – but billions of years ago, when the earth
was much younger, and had much higher levels of atmospheric carbon dioxide. The
bacteria that grew on the young earth took carbon out of the atmosphere, and over
billions of years of dying, not fully decaying, “sequestered” that carbon within the earth
(which resulted in atmospheric carbon dioxide levels dropping to the stable level they
have been at now for millions of years – a level that results in the right amount of infrared
insulation for maintaining a temperature here on earth that is suitable for humans, etc.).
By burning a fossil fuel, we are adding carbon to the atmosphere (as CO2, with the
oxygen portion coming from O2 already present in the atmosphere) that had not been in
our atmosphere for billions of years. Through so doing, we gradually increase the
atmospheric carbon level beyond the fairly stable level it has been at for millions of
years, resulting in more heat held in through the greenhouse effect (another issue to be
discussed). Figure 5 shows the increase in atmospheric carbon levels over the past 200
years since the Industrial revolution, when we began burning fossil fuels. Figure 4 plots
the anthropogenic (man-made) emissions of carbon to the atmosphere (largely from
burning fossil fuels). Some of this CO2 emitted was taken up by plants and the oceans
(the green region), while the rest remains in the atmosphere, increasing the atmospheric
level of CO2, the prime greenhouse gas. The current level is now up to 379 ppm.5
There have been minor fluctuations in the atmospheric carbon levels over the past
few million years, but nothing close to the increase we have caused in the past 200 years
alone. From the environmental standpoint, this is the most important reason for moving
from fossil fuels to renewable biofuels, which result in no net addition to atmospheric
carbon levels.
I.b. Greenhouse Effect
Note – This topic comes under environmental science and current events)
This is a topic that could be covered in a variety of courses, yet is a topic covered
very little in most current curriculum. The issue could be covered either briefly, or in
excruciating detail. Being such an important topic, particularly as far as an issue with
science and political crossover, it would be very desirable for students to garner a better
understanding of the greenhouse effect. There are many valuable resources on the web
providing a thorough discussion of it from a variety of perspectives (biology, chemistry,
physics, public policy, etc.).
One valuable reason for lessons on the greenhouse effect, and global climate
change, is for students to learn that there are ongoing discussions and debates about many
topics in science. Students often get the impression that science is a “finished book”.
Learning that there are many questions scientists are still trying to answer, with many
lively debates among scientists helps develop student interest in the subject.
I.d. Plant Suitability
Perhaps the most critical area of biodiesel research currently is finding or
developing alternative crops that can be grown for producing biodiesel (or another
alternative fuel). The crop used for producing a fuel is referred to as the feedstock.
Currently, soybeans are the primary feedstock in the US for biodiesel production. The
only reason for this is the fact that the US produces a large amount of surplus soybean oil
as a by-product of the soy industry. Soybeans are growing in the US primarily for their
protein content – with the bulk of that being for animal consumption (animals in the US
grown for human consumption consume ten times as much protein every year as all of
the humans in the US). But, other crops would make far better options for biodiesel
production – from the perspective of biology, chemistry, and physics. One example the
UNH Biodiesel Group is working on is hybrids of yellow mustard, bred to have higher
concentrations of glucosinolates. These glucosinolates are broken down in soil by
bacteria, creating isothiocyanates. The isiothiocyanates have strong pesticidal qualities,
but themselves break down within a few days. The result is that the mustard meal (what
is left after extracting the oil) could make an excellent organic pesticide, to replace much
more harmful pesticides. The isiothiocyanates are as effective as pesticides currently
used, but due to the fact that they themselves biodegrade quickly, there would be no
concern about pesticidal residue on crops intended for consumption. The high economic
value of the mustard meal then would allow the oil to be sold much more cheaply,
resulting in lower cost biodiesel.
This illustrates the multi-disciplinary nature of biofuels – this mustard example
can incorporate the chemistry involved in the glucosinolate breakdown, understanding
the biology of breeding mustard for higher glucosinolate levels, the effects of those
glucosinolates on plants and animals, and the economics resulting from the same crop
producing a very high value co-product.
Another feedstock the UNH group is focusing on is high oil algaes, which are
particularly appealing due to their extremely high growth rates (due to high
photosynthetic efficiency and low amount of energy expended on things other than
growing), and the potential for high oil content. The energy of photosynthetically active
radiation (PAR, the portion of sunlight used for photosynthesis) reaching the landmass
portion of earth is 2,250 times our current energy use. Algaes can achieve photosynthetic
efficiencies of up to 25% - meaning that 25% of the PAR can be converted into chemical
energy in the algae. This illustrates that we could meet all of our energy needs with a
relatively small portion of our landmass – provided we do it as efficiently as possible.
Biofuels essentially revolve around using photosynthesis as a means of “producing” our
energy – rather than deriving it from fossil fuels (which are essentially chemical energy
from plants that grew billions of years ago – so still a form of solar energy, but over a
very long-term, with the carbon in the fuel having been out of our atmosphere for billions
of years).
II. Chemistry
There are several lessons that can be initiated with a discussion of biodiesel.
Many of the lesson ideas that are also mentioned under biology and physics could be
included in the chemistry classroom. This section will focus on a few ideas that would be
specific to chemistry, while the ones that overlap into other areas are listed in the area of
overlap. Some possibilities specific to chemistry include:
II.b. Organic Chemistry Terminology
Discussing vegetable oils and transesterification presents a nice opportunity for
students to learn about, or further their knowledge of various chemistry terminology and
classification – in particular, alcohols, alkenes, alkanes, alkyls, acids, esters, and so on. In
addition to examining the reactions involved in making biodiesel, it can also be valuable
to examine the properties of the various types of molecules involved (from different types
of oils). In particular, looking at the properties of the methyl esters of 18 carbon chain
fatty acids can demonstrate the effect of double bonds, and why it is so important to have
the many different names in chemistry to distinguish between seemingly minor
differences. Most students would not expect initially that what appears to be a minor
difference – one molecule having a double bond, and two less hydrogen, as compared to
an otherwise identical molecule – would have such a large impact on the properties of the
molecule.
II.c. Freezing and Gelling
Most liquid fuels consist of a number of different molecules, with different
properties. As a result, the entire fuel does not have one single freezing point. Looking at
Table 3 of the document “Biodiesel Chemistry”, included in the packet, shows typical
profiles of a few different vegetable oils as well as an animal fat (beef tallow). From this,
it can be seen that most potential biodiesel feedstock oils consist of a variety of fatty
acids, anywhere from a few, up to nine or more. As a result, the properties of the
biodiesel will depend on the makeup of the fatty acid profile, as well as the particular
alcohol used in processing (for example, ethyl esters have lower melting points than
methyl esters of the same oil, meaning ethanol would be a preferred alcohol to use for
cold weather operation of the biodiesel. Ethanol has only minor impacts on the cetane
number, lubricity, and viscosity of the fuel. However, producing biodiesel with ethanol is
somewhat more finicky than with methanol. With methanol, the concentration of the
reactants can be off slightly, and the reaction will still proceed successfully.
Transesterification with ethanol is less forgiving. The main reason methanol is the prime
alcohol used in the biodiesel industry, however, is the cheaper cost of methanol).
There are a few different important properties for cold weather performance of
any fuel. These include the “Cloud Point” (CP), “Cold Filter Plugging Point” (CFPP),
and “Pour Point” (PP), also referred to as “Gel Point” (GP). The CP is the temperature at
which some of the molecules in the fuel first begin to freeze, resulting in the appearance
of crystals in the fuel, which give it a “cloudy” appearance initially. Since the Cloud
Point is the temperature at which the highest freezing point molecules in the fuel begin to
freeze, a casual analysis would leave students to believe that the CP is simply the freezing
point of that biodiesel molecule (methyl ester, ethyl ester, etc.) in the fuel that has the
highest freezing point. But, that is not the case. The molecules in the fuel with lower
freezing points have an anti-freezing effect on the molecules with higher freezing points.
This can be observed by looking closely at Tables 2 and 3 in the Biodiesel Chemistry
handout. In soybean oil, ignoring the behenic acid and erucic acid, which are present in
only very small percentages, the fatty acid whose methyl ester has the highest freezing
point is stearic acid, which constitutes 3.6% of soybean oil. The next highest is palmitic
acid, constituting 9.9%. The freezing points of methyl stearate and methyl palmitate,
respectively (from Table 2), are 39.1º C and 30.5º C (102.4º F and 86.9º F). So, at first
glance, we may expect that the “Cloud Point” for soy biodiesel (aka methyl soyate)
would be 39.1º C, the freezing point for methyl stearate. But, looking at Table 3, we see
that the CP is actually 3º C, considerably lower. The reason for this is the freezing point
depressing effect of the other molecules in the fuel, which have considerably lower
freezing points. Biodiesel therefore presents an interesting opportunity for discussion of
how freezing point depression works.
With liquids consisting of molecules of various freezing points, gelling occurs as
a result of solid molecules entangling and crosslinking, to form a semi-rigid structure,
even though the majority of the molecules may still be liquid. A gel, also referred to as a
sol, would of course present a serious problem to a vehicle’s fuel system. Regular
petroleum diesel can gel at anywhere from –20º C (-4º F) to -10º C (14º F), depending on
the quality of the fuel. Since atmospheric temperatures can fall below that, the diesel fuel
industry has developed techniques for “winterizing” the fuel, to prevent this gelling from
happening. The temperature at which this gelling occurs is referred to as either the “Gel
Point” (GP), or more commonly, the “Pour Point” (PP). With diesel fuel, in some cases
the gelling issue is dealt with by blending in other liquids with lower freezing points,
such as kerosene. This also has a freezing point depressing effect on the molecules in the
diesel fuel, so it also lowers the cloud point. Another method of winterizing involves the
addition of an “antigel additive”. These additives are generally added in very small
quantities (0.1-0.2% by volume), but can significantly lower the PP. They do so,
primarily, by bonding to frozen molecules when the fuel falls below the cloud point, and
preventing those molecules from bonding/crosslinking with other frozen molecules. The
molecules of an antigel additive are generally considerably smaller than the fuel
molecules themselves, so 0.1% of the additive by volume can effectively block a much
larger percentage of fuel molecules from having the ability to gel the fuel. Some additives
can lower the PP of diesel fuel by 30ºC (48º F) or more.
These same methods of winterization can also be used with biodiesel. Many of the
same antigel additives that are effective with petroleum diesel are also effective with
biodiesel. An issue of critical importance, however, is that most biodiesel fuels have a
greater percentage of the highest freezing point molecules than most petroleum diesel, so
while 0.1% by volume of the additive may be enough to bond to all of those high-freeze
point molecules in petroleum diesel, they may not be enough for biodiesel. As a result,
using the same amount may have no effect on the gel point. But, using a greater
percentage, based on the percentage of high freeze point molecules in the biodiesel, a
significant antigelling effect can be achieved. Most methyl soyate biodiesel has a
gel/pour point slightly below 0ºC (-3ºC is the PP of the sample analyzed in the reference
used for compiling Table 3). But, in tests performed by a member of the UNH Biodiesel
Group (Michael Briggs), use of antigel additives in the appropriately higher percentage
required successfully lowered the PP of soy biodiesel to below -23ºC.
The cold flow properties of biodiesel present an excellent opportunity for lessons
on freezing point depression as well as sols (gels), and applications of those concepts
currently in use in the automotive fuel sector, as well as how they can be used with an
alternative fuel entering the market.
III.a. Thermodynamics, Energy Conservation
An important issue when looking at fuels, and energy “production”, is the energy
efficiency of the processes involved. For an automotive fuel, the more efficiently it can
be produced, the less energy we need to create for the production of the fuel. This is an
issue of critical importance in any discussion of alternative energy or fuel, and is
something which is unfortunately often completely overlooked. A key concept for
students to understand here is the conservation of energy. Energy can not be created or
destroyed, it can only be changed from one form to another. When we say we “produce
energy from coal”, for example, we are not actually creating energy, we are instead
converting the chemical energy that was in the coal into electrical energy which we can
more readily use.
There are many different methods of examining the energy efficiency for a
process. One of the most useful is referred to as the EROI – or Energy Return On
Investment (or EROEI, Energy Return on Energy Invested). Essentially, this means how
much energy we get back (in the form of a fuel, or usable energy) for each unit of energy
we put into the process. The higher the EROI, the better the process. If the EROI is below
one, then we actually lose energy through the process.
A similar method often used is referred to as an energy balance. Energy balances
can be performed in a number of ways, and at heart are the same as an EROI. But, energy
balances are often done to only include a certain type of energy input. For example, fossil
energy balances are often done to look at how efficiently something uses fossil fuels. A
fossil energy balance is done to see how much energy we get back for each unit of fossil
energy expended in the process – including the energy of any fossil fuel converted to a
more usable form. To clarify, for analyzing the use of petroleum to make gasoline, diesel,
etc., the EROI measure tells us how much energy we get in the form of those fuels for
each unit of energy we expend on extracting the petroleum, refining, and transporting it.
But, the EROI does not include the energy in the petroleum itself as an energy input. For
the various petroleum products (gasoline, diesel, etc.), the EROI is generally around 10 to
20, depending on the quality of the petroleum and amount of processing involved (i.e.
Middle Eastern oil is generally lighter, and requires less processing to get gasoline, than
petroleum from the US). An EROI of 10 means that for each unit of energy we put into
the process (including extracting the petroleum, refining it to fuel, transporting it, etc.),
we get back an amount of fuel containing 10 units of energy.
An EROI of 10 is not a violation of the conservation of energy. No energy is
“created” in the process. The reason the EROI can be greater than 1 is that the energy
contained in the petroleum itself is not counted as an energy input for this calculation.
This is done since we do not have to put energy in ourselves to “make” the petroleum.
It’s just sitting there, so if we can extract it, we can consider the petroleum energy “free”
– at least for the purpose of an EROI calculation. An EROI of 10 simply means that all of
the additional energy, which we have to put into the process, adds up to only one unit of
energy for each unit of fuel we are able to process from the “free” petroleum (free in
energy terms for this calculation). All of the energy input used for the process is included,
even if that energy came from petroleum itself.
By contrast, a fossil energy balance includes the energy in the petroleum as an
input. The reason for such a calculation is that it’s often useful to know how efficiently
we can convert fossil fuels to more usable fuels, since fossil fuels are after all not
unlimited, and not “free”. So, for a fossil energy balance, the energy within the extracted
petroleum is counted as an energy input. If we extract an amount of petroleum containing
11 units of energy, spend 1 unit of that energy in processing (i.e. burn some of the
petroleum to produce heat and electricity for operating a refinery, etc.), and end up with
10 units of energy in the form of various petroleum fuels, our fossil energy balance would
be 10 units of output energy to 11 units of input energy, 10:11, or a fossil energy balance
of 10/11:1, 0.91:1. Such a fossil energy balance would be abbreviated as just 0.91, meaning
we get 0.91 units of energy in the form of fuels for each unit of fossil energy input –
including the energy within the petroleum being processed. So, while petroleum fuels
may have an EROI of 10, they would have a fossil energy balance of 0.91.
These analyses are useful for comparing other forms of alternative fuels and
energy. If an alternative fuel has an EROI of only 1.4, to make enough fuel-energy to
replace all of the petroleum fuel we currently use, we would have to generate far more
energy to be used as input to the process than we currently do for processing petroleum
fuels. Likewise, if the EROI or fossil energy balance is below 1, we would end up using
up a greater amount of energy than we end up with as fuel (so it is not a truly renewable
fuel).
In energy terms, biofuels use the sun as their prime energy input. We may put
energy into planting, fertilizing, harvesting, and processing the crops, but a great deal of
energy input also comes from the sun. Since plants use photosynthesis to convert solar
energy into chemical forms of energy (carbohydrates, fats, etc.), we can think of plants as
“cheap” solar cells. They convert solar energy into a form more usable as a fuel. So,
whereas for the purpose of an EROI analysis we can consider the energy in a fossil fuel
we dig up out of the ground as “free” (except for the additional energy we expend getting
it), we can also consider the energy in the plants free – except for the energy that we put
into planting, fertilizing, and harvesting them. After all, “we” are not responsible for
producing the solar energy the plants use as their prime energy source for making the
chemical energy within the plant’s biomass.
The U.S. Department of Energy (US DOE) performed a thorough fossil energy
balance calculation for soybean biodiesel. In this analysis, they assumed that all energy
inputs other than the energy within the soybeans themselves came from fossil fuels. So,
for example, the tractors used for planting and harvesting were assumed to run on
petroleum diesel – even though they could be run on biodiesel, so it would not be a fossil
input. This assumption is useful to make, as for a biofuel it results in the fossil energy
balance essentially being an EROI calculation. The reason being that this method for
calculating a fossil energy balance assumes that all energy input (except the energy in the
plant) is from fossil fuels. Therefore, the energy input for the EROI of a biofuel is the
same as the energy input side of the equation for a fossil energy balance, when that
assumption is made (since neither analysis would include the energy in the plant as an
input). The fossil energy balance would be better if some inputs came from biofuels as
well, such as running tractors on biodiesel, but it is more useful to know how much total
energy input is required.
The US DOE’s analysis yielded a value of 3.2 for the fossil energy balance (and
henceforth EROI) of soybean biodiesel. This is considerably better than the fossil energy
balance for petroleum fuels, but lower than the EROI of petroleum fuels. Other options
for producing biodiesel can yield a considerably higher EROI, which makes it suitable as
a potential wide-scale replacement for petroleum. This analysis also assumed that the
methanol used was derived from natural gas – a reasonable assumption for now, since
that is where most of our methanol comes from. But, there are many options for
producing methanol from biomass, which could be used in the future. So, if those
methods were used, the EROI and fossil energy balance could be increased substantially.
An example of why energy analyses are so important in analyzing alternative
fuels can be seen by looking at the furor over the notion of a “hydrogen economy”. One
good example of this is included in the “Misconceptions” section later in this document.
In essence, the relevant issue is that most media articles, and even many attempts at
scientific analysis of hydrogen as a fuel completely ignore this issue. Deciding upon
public energy decisions without including an energy analysis is extremely short-sighted.
Table 4, “Analysis of Prototype and Production Vehicles on Various Fuels”,
includes an example of using a fossil energy balance to examine various fuel options.
This analysis includes vehicles running on gasoline, diesel, biodiesel, and hydrogen. The
biodiesel vehicle included is a Volkswagen Jetta TDI Wagon, a vehicle currently in fullscale production. The hydrogen vehicle included is Honda’s Fuel Cell Vehicle (FCV)
prototype, a vehicle which Honda previously estimated would sell for roughly $100,000
if in full-scale production in 2012 (they have since backed away from that estimate,
saying it will not be possible). For such a cost, we should hope for a very high fossil
energy balance – at least higher than for the Volkswagen available today for around
$20,000, and running on 100% biodiesel.
The most useful means of comparing vehicles on their energy efficiency is
the total fossil energy input per mile. As the table shows, this quantity is a combination of
the fossil energy balance for the fuel itself (FEB), the energy density of the fuel in
Btu/gallon (ED), and the fuel efficiency of the vehicle in miles per gallon (FE). The total
fossil energy input per mile then becomes:
Fossil Energy Input per Mile = _____Energy Density_______
Fuel Efficiency * Fossil Energy Balance
The fossil energy balance is used since it gives a better comparison of how
efficiently we use fossil fuels, and the net CO2 emissions (since those only come from
fossil fuels). For biofuels, as mentioned, the energy inputs could all come from non-fossil
sources, but for this analysis, it is more meaningful to assume they come from fossil
sources.
For the hydrogen analysis, the method of generating hydrogen was assumed to be
steam reformation of natural gas – the most common and cost effective method of
producing hydrogen, and likely the primary method that would be used in a “hydrogen
economy”. Large quantities of hydrogen are already produced via this method for various
industrial uses. The cost and efficiency of this process is therefore very well established.
A US DOE analysis calculated the fossil energy balance (FEB) for this process of
producing hydrogen to be 0.66, meaning for each unit of fossil energy input, we get back
0.66 units of energy in the form of hydrogen. Using the specifications for Honda’s Fuel
Cell Vehicle from Table 4 (FE = 5.7 mpg, ED = 9 Btu/gal, FEB = 0.66) , this yielded a
fossil energy input per mile of 2.4 Btu/mile. By comparison, with the Volkswagen
already on the market (FE = 44.75 mpg average between city/highway), running on
soybean biodiesel (and assuming all energy inputs (tractors, etc.) are from fossil fuels, for
a FEB of 3.2, and ED of 127 Btu/gal) yields an input of 0.89 Btu/mile. If biodiesel were
used in the Dodge Intrepid ESX3, a diesel-electric hybrid prototype developed by
Chrysler in 2000 (and with an expected full-scale production cost of $28,500), the input
would be 0.55 Btu/mile.
Table 4 - Analysis of Prototype and Production Vehicles on Various Fuels
Jetta TDI on
Jetta TDI on
Jetta
2.0L
Toyota
biodiesel
petroleum
gasoline
Prius
diesel
engine
gasoline
Honda
on
Cell
Fuel
vehicle
(hydrogen)
Dodge ESX3
(dieselhybrid)
biodiesel
Vehicle cost
$19,970
$19,970
$18,790
$21,520
$100,0003
$28,500
Fuel efficiency
41/48.5
42/50
24/31
52/45
5.74
72
Vehicle range
609/711
609/711
348/450
619/536
155
???
Power (hp)
90
90
115
70
110
???
Torque (ft-lbs)
155
155
122
82 (EM?)
188
???
Cost/mile2
$0.047
$0.040
$0.062
$0.035
$0.195
$0.03
141
123
123
9
127
0.83
0.74
0.74
0.667
3.2
3.7
6.0
3.4
2.4
0.55
Energy density of 127
fuel (Thousands of
BTUs/gal)
Fossil Fuel Energy 3.2
Balance6
Total fossil energy 0.89
input/mile8
(Thousand
BTU/mile)
2 .5
Ho nd a' s F uel C ell
V ehicle
2
1.5
V W , so yb ean
B io d iesel
D o d g e Int r ep id ,
d iesel- elect r ic
hyb r id
1
0 .5
0
F EI, B t u/ M ile
The Total Fossil Energy Inputs per mile are shown in Figure 6. This important
analysis shows that the most likely scenario for the hydrogen economy would yield
on
vehicles which would still require considerably more fossil energy input per mile than
vehicles available today, running on biodiesel. Unfortunately, such energy analyses are
rarely done by the media, or even the panels making recommendations on public energy
policy.
BIO-DIESEL PROCESSING
Biodiesel is a clean, renewable and domestically produced diesel fuel, which has many
characteristics of a promising alternative energy resource. The most common process for
making biodiesel is known as transesterification. This process involves combining any
natural oil (vegetable or animal) with virtually any alcohol, and a catalyst. There are other
thermochemical processes available for making biodiesel, but transesterification is the
most commonly used one due to the simplicity and high energy efficiency. The high
energy efficiency of transesterification is an important aspect of Biodiesel, which makes
it favorable in the competitive energy market. The following is a transesterification
reference guide that can be used to process Biodiesel on an experimental scale for
classroom demonstrations. It can be done with basic equipment and common chemicals.
Be sure to use extreme caution when carrying out this procedure, the methanol and
catalyst are toxic, and give off potentially harmful vapors. Proper personal protection is
imperative, including thorough ventilation. Links will also be given for more information
on building more sophisticated small-scale biodiesel processors.
This demonstration can be done with a food processor or a large, empty (and clean) soda
bottle (using shaking to mix the oil and methoxide).
Materials
Biodiesel consists of three principal feed stocks;
1. Oil: Glycerides are commonly known as oils or fats, chemically speaking these are
long chain fatty acids joined by a glycerin backbone. They appear most often with three
fatty acid chains connected to the glycerin, making them trigylcerides. In the US, the
primary triglycerides used currently for biodiesel production are soybean oil and waste
vegetable oil (which is often used soybean oil). During the process of being used in
fryolators, some of the triglycerides are broken apart into mono or diglycerides, leaving
free fatty acids (FFAs) in the oil. To counter this, additional catalyst must be added
according to the acidity of the specific oil, since the FFAs will bond with and neutralize
some of the alkali catalyst.
2. Alcohol: Although a variety of alcohols can be used to produce Biodiesel, such as,
ethanol or butanol, this experiment will focus on methanol as it is most readily available,
and most frequently used (the reaction is also more complicated with larger alcohols,
which will be explained later). Therefore the Biodiesel produced is referred to as methyl
esters. Methanol is one of the most common industrial alcohols; because of its abundant
supply it’s most often the least expensive alcohol as well.
3. Catalyst: the third reactant needed is a catalyst that initiates the reaction and allows the
esters to detach. The strong base solutions typically used are sodium hydroxide (NaOH)
and potassium hydroxide (KOH). This classroom experiment will be using NaOH as
catalyst.
Safety:
Extreme caution must be taken when working with methanol and especially with sodium
methoxide. Safety Goggles, Chemical gloves and ventilation apparatus must be used at
all times. Have plenty of water and vinegar (to neutralize the base) on hand.
Processing guidelines:
1. To get a more complete reaction, the oil should first be heated to around 120-130º F
to help the reaction proceed more quickly. Used Vegetable oil should also be filtered
first (after heating) to remove particulates. Used oil may also have water in it which
would need to be removed. With this small batch of oil, this can be accomplished by
heating to above 100º C to boil off the water. Water removal can also be done (with
less energy) by using a vacuum pump to decrease the boiling point of water, or by
using molecular sieves.
2. Approximately 3.5g of NaOH per L of oil is needed when using virgin oil. However
when using waste oils (which therefore have free fatty acid (FFA) content), the pH
must first be determined (by titration) to calculate the additional amount of NaOH
needed.
The titration (for used oils, or older oils that could have degraded some, producing
FFAs) is done as follows:
Dissolve one gram of NaOH into 1 liter of distilled water. Dissolve 1ml of the filtered
oil into 10ml of isopropyl alcohol and add two drops of phenolphthalein, an acid base
indicator. Now slowly add, by calibrated dropper or pipet, the NaOH(aq) solution to
the oil solution, mix intermittently. When the oil solution turns pink and stays pink
for ten seconds the titration is complete. The volume of NaOH(aq) solution in
milliliters necessary to neutralize the free fatty acids corresponds directly with the
number of additional grams per liter of NaOH needed for transesterification.
3. Methanol makes up approximately 10% of the Biodiesel, but to force the reaction, an
excess is generally added – usually totaling 20% of the volume of the oil (well
designed processors can use methanol recovery systems to recover this surplus
methanol after the reaction, after removal of the glycerin). So for a reaction with one
liter of oil; 200 ml of methanol is first mixed with 3.5 grams of NaOH, plus any
additional NaOH in regards to the free fatty acid titration (only necessary if using
used/waste vegetable oil). Ensure the NaOH is completely dissolved; this reaction
creates sodium methoxide. Again, Caution! Sodium methoxide is extremely toxic.
Provide thorough ventilation and wear protective equipment.
4. Add the sodium methoxide to the oil. Mix thoroughly - for this small demonstration, a
blender on a low setting for an hour or more is ideal; however, vigorous shaking for a
couple minutes will suffice (although if this method is used, you’ll need to re-shake
the solution after twenty minutes or so, and at least one more time). In actual
biodiesel processors, the oil is heated to 120-130º F to aid the reaction, so it can be
done in only an hour. If done at room temperature, longer reaction time is needed for
a complete reaction – but repeated shakings separated by 10-20 minutes can suffice.
If building a larger processor, an ideal solution is to use an old electric water heater as
your processing tank, with a recirculating pump to send the oil/methoxide mix up to
the top of the tank, allowing it to splash down into the tank for splash blending. See
the “Biodiesel Homebrew Guide” reference for more details on this design.
5. Allow the solution to sit. After about ten minutes, the beginning of separation can be
observed. However, after about eight hours the glycerin molecules will have mostly
settled to the bottom of the container and the methyl esters (biodiesel) will be on top.
Analyze results
Possible errors:
1. Soap formation. You can get this if using waste vegetable oil that is heavily used, or
using too much catalyst. Any Free Fatty Acids (FFAs) will combine with the alkaline
catalyst (NaOH or KOH) to make soap (which is why you need to use extra NaOH
when dealing with used oils with FFAs). These soaps need to be removed from the
biodiesel by “washing” it (discussed later). A large amount of FFAs can result in
enough soap forming to turn the entire reaction into a bunch of “glop” (non-scientific
term). If using WVO with high levels of FFAs (determined via titration), a slightly
different process can be used, known as an “acid-base” process (whereas this process
discussed is strictly a base catalyzed process). In the acid-base process, you first add
some acid (hydrochloric typically) and a small amount of methanol to esterify the
FFAs into biodiesel, and then do the normal base catalysed process to conver the
triglycerides into biodiesel. With high FFA oils, the normal base process doesn’t
yield as much biodiesel, since the FFAs are being turned into soap (and removed
through washing). The acid-base process allows you to turn those FFAs into
biodiesel.
2. Not enough ly, resulting in unreacted oil.
3. Not enough alcohol (reaction does not proceed to completion), can also get more soap
formation.
4. Water in oil (results in catalyst being broken apart, and more soap formation)
5. Not enough reaction time (a common problem with demonstration batches like this.
Ideally you want to mix for an hour or so, at a slightly elevated temperature (120-130º
F). The reaction does not proceed instantly from triglycerides (oils) to 3 biodiesel
molecules (per triglyceride). Instead, the methoxide first cleaves off one fatty acid
(making one biodiesel molecule from it, by combining with the methanol), leaving a
diglyceride (DG).
If there is further agitation, the DG is broken apart by the
methoxide to make another biodiesel molecule and leaving a monoglyceride (MG).
Further agitation breaks that MG apart, making the third biodiesel molecule and
leaving free glycerin. If the agitation does not continue long enough (or is not
repeated multiple times), you will likely not see full conversion of triglycerides to
biodiesel, instead being left with some MGs and DGs, which will often show up as
white “chunks” when the fuel cools down to room temperature.
Washing
“Washing” is done primarily to remove soap from the biodiesel (which forms from the
combination of the alkali catalyst and free fatty acids). The glycerin primarily settles out
(provided enough time is given), the methanol either evaporates or is recovered (and
mostly goes with the glycerin), the catalyst goes out with the glycerin, but the soaps can
remain in the biodiesel unless washed. More sophisticated processing techniques (such
as using organometallic catalysts instead of alkali catalysts) can eliminate the need for
washing by preventing soap formation.
Washing is done through one of two methods – mist washing or bubble washing (or
both). Mist washing consists of gently misting water down onto the biodiesel, so that as
it falls down through it (since the water is more dense) the soaps dissolve into the water,
being pulled out of the biodiesel. Bubble washing consists of using an aerator (such as
used in a small household aquarium) to bubble water and air up through the biodiesel,
with the soaps dissolving into the water as it travels up (with the air) and then falls back
down. Bubble washing is more effective, but causes more agitation – which can result in
an emulsification forming if there is too much soap. So, an ideal approach is to first do
one gentle mist wash, drain the water, and then do a couple of bubble washes. Washing
is generally done multiple times (with each wash taking as much as a couple of hours),
only stopping when a wash does not pull out any more soap (evidenced by the wash
water remaining clear).
Washing is generally done in a specific “wash tank”, often the same tank used for
settling. You need a tank that can be drained from the bottom – either a conical bottom
tank with a drain at the base, or a cylindrical tank with two drains on the bottom, one of
which has a stand pipe going up into the tank far enough that the biodiesel can be drained
separate from the water or glycerin on the bottom. A conical bottom tank is ideal,
although more expensive.
Biodiesel Chemistry
Biodiesel
Chemically, biodiesel (from transesterification) refers to mono alkyl esters of long chain
fatty acids derived from natural oils. We’ll look a little closer into what exactly that
means.
Ester
An ester is the product of combining an acid (abbreviated as R1-COOH) with an alcohol
(abbreviated as R2OH). Esters in general are often abbreviated as R1-COOR2, where
R1COO represents the residue of an oxygen acid (The residue is what’s left when the
hydrogen is lost), and R2 represents an alkyl – from an alcohol that lost its OH group. So,
through the combination, an H is lost, and an OH (although in reality the O could come
from either the alcohol or the acid), yielding a water molecule (H2O), and the ester, made
up of everything else remaining of the acid and alcohol except the H2O. Esters vary
depending on the type of acid (R1COOH, often abbreviated as R1 for simplicity) and the
type of alcohol (R2OH, often abbreviated R2).
Vegetable Oil
Vegetable oils are triglycerides, which are esters of glycerin (an tri-hydroxy alcohol, aka
glycerol) and three fatty acids (which can be different types). A glycerin molecule looks
like:
CH2OH
|
CHOH
|
CH2OH
Figure 1 – Glycerin (glycerol)
Each vegetable oil molecule is a triglyceride, meaning it is made of the combination of
three fatty acids (which can be of different types) and a glycerin backbone. So, while
some esters consist of just one acid (R1OH), vegetable oil molecules have three acids
combined with an alcohol. When speaking about vegetable oils in particular, the three
acids are often referred to as R1, R2, and R3, and the alcohol as R4. In reality, the acids
are R1OOH, R2OOH, etc., where “R” represents a chain of carbon atoms with hydrogen
atoms attached, but with the carbon on one end being a carboxyl group (carbon with
OOH attached). Rather than an entire glycerin backbone, it is actually the alkyl group of
glycerin, essentially glycerin with just oxygen atoms in place of the hydroxy (OH) groups
(so remove the three Hs on the right of Figure 1).
When fatty acids and glycerin are
added to make triglycerides, the glycerin loses the three Hs on the end, and the acids lose
the hydroxy group on the end, making water. A triglyceride (vegetable oil) can then be
drawn as:
O
H2COR1
CH2OOR1
|
|
HCOR2O
or simplified as
CHOOR2
|
|
H2COR3
CH2OOR3
O
Figure 2 – A triglyceride (vegetable oil molecule)
The extra oxygens on the triglyceride are attached to the carbon on the end of the fatty
acid’s alkyl group with a double bond (one oxygen atom has a double bond to the carbon
atom at the end of the fatty acid alkyl group, the other oxygen has one bond to that
carbon atom, and its second bond is to one of the carbons in the glycerol itself). The
chemical diagram on the left of Figure 2 illustrates more appropriately the structure of the
glycerol, while the diagram on the right is the convention more commonly used. The
fatty acids involved are R1OOH, R2OOH, and R3OOH (the hydrogen atoms and one
oxygen atom are lost when the acid is combined with the alcohol to make the triglyceride,
with the alcohol losing a hydrogen atom, creating water),
Alcohol
An alcohol is a molecule in which any carbon atoms have the maximum number of
hydrogen atoms attached possible, except for one carbon atom which has an OH group
connected. The simplest alcohol, and the one used most often in biodiesel production, is
methanol. Methanol consists of only one carbon atom, with three hydrogen atoms
attached, and one oxygen attached. The oxygen atom also has a hydrogen atom attached.
Thus, methanol is often written as CH3OH. The next simplest alcohol is ethanol, which
has one more carbon atoms, with two hydrogen atoms attached, in between the CH3
group and the OH group. Ethanol is written as either CH3CH2OH, or C2H5OH. The
former method is often used to give more of a description of the structure (since it
consists of a carbon with three hydrogen atoms attached, connected to another carbon
with two hydrogens attached, connected to an oxygen with one hydrogen attached).
These alcohols are abbreviated as ROH, where the R is the alkyl group (hydrocarbon
chain (consisting of CnH2n+1)), and determines what type of alcohol it is.
Typical Fatty Acids in vegetable oils
Below is a table of typical fatty acids found in alcohol, and some of their properties. The
“Acronym” is a chemical abbreviation for the molecule. The first number refers to the
number of carbon atoms in the chain, and the second number refers to the number of
double bonds in the molecule. Thus, Linoleic acid, for example, is a fatty acid consisting
of a chain of 18 carbon atoms, with two double bonds. Notice that the more double bonds
in the acid, the lower the melting point. This is an important issue regarding the cold
weather suitability of the oil or the biodiesel produced from the oil, and will be discussed
further. The double bonds also lower the boiling point, which does not make a significant
difference on the operability of the fuel since all biodiesel molecules have boiling points
so high as to make vaporization not an issue.
Table 1 – Properties of Fatty Acids commonly found in vegetable oils 1
Fatty Acid Acronym Molecular Melt
Boil
Cetane
Number (kg-cal/mole)
Weight
ºC/ºF
ºC/ºF
Heat Combust
Caprylic
8:0
144.2
16.5/61.7
239.3/462.7
Capric
10:0
172.27
31.5/88.7
270.0/518.0 47.6
Lauric
12:0
200.32
44.0/111.2 131.0/267.8
1763.25
Myristic
14:0
228.38
58.0/136.4 250.5/482.9
2073.91
Palmitic
16:0
256.43
63.0/145.4 350.0/662.0
2384.76
Stearic
18:0
284.43
71.0/159.8 360.0/680.0
2696.12
Oleic
18:1
282.47
16.0/60.8
286.0/546.8
2657.4
Linoleic
18:2
280.45
-5.0/23.0
230.0/446.0
Linolenic
18:3
278.44
-11.0/12.2
232.0/449.6
Erucic
22:1
338.58
33.0/91.4
265.0/509.0
1453.07
Saturated Fatty Acids
A saturated fatty acid is one containing no double bonds. Since fatty acids are acids with
a COOH group at the end, a saturated acid is one in which the rest of the carbon chain is
an alkane – i.e., the carbon atoms in the chain have the maximum number of hydrogen
atoms bonded possible (every bonding location is filled with a hydrogen atom, except for
single bonds to neighboring carbon atoms). Stearic acid (18:0) is an example of a
saturated fatty acid, as it has no double bonds. The chemical formula for stearic acid is
CH3(CH2)16COOH.
Unsaturated Fatty Acids
An unsaturated fatty acid is one containing one or more alkene functional groups – those
being hydrocarbons with double bonds between two carbon atoms. An alkene does not
have the maximum number of hydrogen atoms possible on all of the carbon atoms, as two
adjacent carbons have a double bond between them, and therefore one less hydrogen
attached each. Oleic acid is an unsaturated acid of the same length as stearic acid, but
with a double bond between two of the carbon atoms, and therefore two less hydrogen
atoms. Molecules with double bonds are often written using an equals sign (“=”) to show
where the double bond is. For example, oleic acid has its one double bond as the ninth
carbon-carbon bond, counting from the chain most distant from the carboxyl group
(COOH). Thus, oleic acid would be written as CH3(CH2)7CH=CH(CH2)7COOH. Thus,
the molecule has a methyl group (CH3), then 7 carbons with single bonds between them,
each having two hydrogens attached ((CH2)7), then the carbon that has one end of the
double bond (leaving only room left for one hydrogen atom, so it’s a CH), the double
bond connecting to another CH, followed by 7 more CH2 groups, and finally the
carboxyly group (COOH). This molecule is exactly the same as the stearic acid molecule
(CH3(CH2)16COOH, no double bonds), except for the double bond between the 9th and
10th carbon atoms (so the 9th carbon-carbon bond). Thus, in the middle of the molecule, a
set of two CH2 groups is replaced by CH=CH (double bond between the carbons, only
one hydrogen each).
This seemingly minor difference results in a significant change in some of the properties
of the molecule, most notably the melting point. The cold flow properties of the oils, and
the resulting molecules can thus be a nice method for introducing this topic of how minor
differences in a molecule can have large effects, and in particular, double bonds lower the
melting point of molecules (generally).
The oleic acid molecule could have another double bond added, which would turn it into
linoleic acid (18:2). A third double bond would make linolenic acid. Many vegetable oils
normally consist of a significant percentage of these particular 18 carbon acids with
double bonds. When the oil is hydrogenated (usually through high temperatures, such as
when oil is used in a fryolator), that is when some of these double bonds are lost,
replacing a CH=CH group with CH2CH2. The acid (or the oil that the acid is a part of)
acquires two more hydrogens, and loses a double bond. The result is an increasing of the
melting temperature of the acid, or oil of which it is part. This is an important
consideration as far as using waste vegetable oils as feedstocks for producing biodiesel.
The more heavily used the oil is, the more hydrogenated it becomes, resulting in higher
melting points for the molecules. Therefore, caution should be taken when using heavily
used (hydrogenated) oils for making biodiesel, as the higher freezing/melting points of
the molecules would result in a greater tendency of the fuel to clog fuel filters, or
possibly gel entirely.
Transesterification
Chemically, transesterification is the process of exchanging the alkyl group (from an
alcohol) of an ester with another alkyl, from a different alcohol. In the case of biodiesel, a
vegetable oil ester is combined with a simple alcohol and a catalyst, resulting in the
breakup of the triglyceride ester (three fatty acids connected to a single glycerol
(alcohol)), and the joining of the fatty acids with the added simple alcohols. The glycerin
alkyls are replaced with the alkyl of the added alcohol (i.e. methyl for methanol, ethyl for
ethanol, etc.). The separated glycerol is the waste product. This reaction is shown below:
CH2OOR1
catalyst
CH2OH
|
CHOOR2
+ 3CH3
3OORx
+ CHOH
|
|
CH2OOR3
CH2OH
Vegetable oil
3 Methanols
Biodiesel
Glycerin
Figure 3 – Transesterification
Rx is used since the biodiesel produced will consist of different types of mono-alkyl
esters, because of the various fatty acids (R1, R2, R3) in the vegetable oil. The reaction
can proceed both ways, so it is necessary to add an excess of methanol to force the
reaction to the right. Since it is not desirable to have free methanol in the biodiesel fuel, it
is then necessary to recover the methanol either by water washing, or a pressurecondensing method. But, the glycerin must be removed first (and actually, most of the
excess alcohol stays with the glycerin). If you remove the surplus methanol while the
glycerin is still present with the biodiesel, the process will start gradually reversing –
biodiesel and glycerin combining to re-make vegetable oil and methanol. The glycerin is
more dense than the biodiesel, so it will gradually settle to the bottom in the reactor,
simplifying separation.
Now, since we first react the catalyst with the methanol to form a methoxide (potassium
or sodium methoxide), the reaction doesn’t actually proceed exactly as shown in Figure
3. If we use NaOH as our catalyst, it combines with methanol (CH3OH) to form sodium
methoxide (NaO-CH3) and a water: NaOH + CH3OH
3
+ H2O. Sodium
Methoxide is a quite hazardous material, so it is extremely important to handle it with
care – it is explosive and toxic. Well designed biodiesel processors (whether small
home-scale or large commercial scale) keep the methoxide completely contained in
reaction vessels, and free from any sparks (you don’t want to use a mechanical mixer that
could cause sparks – this is why a pump/splash blending process is desirable). You need
to make sure that your alcohol and catalyst are very dry (no water), otherwise its presence
will prevent a full conversion to methoxide.
When the methoxide is added to the triglyceride, the conversion shown in Figure 3
actually happens in a series of reactions – the triglyceride first uses one fatty acid group
and becomes a diglyceride, then loses a second, becoming a monoglyceride, and the third
fatty acid is finally stripped off, leaving free glycerin. Each of the fatty acids are
converted into biodiesel (methyl ester) as they are stripped off. Each step of this reaction
occurs by the methoxide “attacking” the end carbon atom of each fatty acid alkyl group
where they attach to the glycerol backbone. The metal ion of the methoxide (Na or K)
breaks off, so you are left essentially with the methanol without a hydrogen atom (CH3O) with a negative charge. The carbon on the end of each fatty acid alkyl group in the
triglyceride has a slight positive charge, with the oxygens on that carbon having a slight
negative charge, particularly in the double bond between one of the oxygens and the
carbon. This is where the methoxide “attacks”, free of the metal ion.
This carbon being attacked (since it has a slight positive charge and the CH 3O- is
negative) loses its double bond to the oxygen, and the CH3O bonds to the carbon. This
carbon separates from the oxygen of the glycerol that it had been attached to, with the
carbon-oxygen double-bond reforming. The result is one biodiesel molecule has been
made, and the triglyceride has been turned into a diglyceride. The first step essentially
looks like this (the water comes from the creation of the methoxide):
Vegetable oil + NaMethoxide + H2O
Diglyceride + Biodiesel + NaOH
– First step of transesterification – triglyceride turns to diglyceride, one methoxide joins
freed fatty acid to make biodiesel
This process is repeated during the transesterification, with the additional methoxides
further breaking down the diglyceride into a monoglyceride (and making one more
biodiesel molecule), and then the monoglyceride being broken down into a glycerol (and
the final biodiesel molecule). The sodium separates from the sodium methoxide at each
step, combining with an OH- from the water (the other H goes onto the diglyceride),
reforming the catalyst NaOH. If the mixing time is too short, the reaction could stop
before finished, leaving you with a mix of biodiesel, monoglycerides, diglycerides, and
triglycerides.
As can be seen, the NaOH is not used up in the reaction – although procedurally it
effectively is (since it comes out in the glycerin, and is typically not easily recoverable).
Water is formed during the creation of the methoxide, but is also used up in the recreation
of the NaOH during each esterification reaction. Research on more novel catalysts, such
as organometallics, has lead to the development of catalysts that can be fixed to a
substrate, so that the alcohol and oil can be mixed together directly (no methoxide step),
and the transesterification occurs as the mix flows across the catalytic substrate. This is
an excellent option for new industrial scale biodiesel plants, as it eliminates the need to
continually buy new catalyst (such as NaOH), and simplifies the glycerin purification
(since there is no NaOH in it).
Biodiesel – Mono Alkyl Esters
As mentioned previously, biodiesel molecules are referred to as mono-alkyl esters, since
they are esters with one alkyl (from the alcohol) per fatty acid, in contrast to the
triglycerides in the vegetable oil, which had three fatty acids for each glycerol. If the
alcohol used in making the biodiesel was methanol, then the biodiesel is referred to as a
methyl ester. If the alcohol was ethanol, the biodiesel would consist of ethyl esters. Table
2 below shows a list of the methyl esters made from the fatty acids listed in Table 1, and
their properties. Note that the methyl esters of fatty acids with more double bonds have
lower melting points than those without double bonds, just as the fatty acids themselves
do. Also notice that the melting points of the methyl esters are lower than the melting
points of the fatty acids themselves. An interesting point of discussion is that the boiling
points are not all affected similarly, from fatty acids being turned into mono alkyl esters.
Note that methyl stearate has a much higher boiling point than stearic acid, while methyl
linolenate has a much lower boiling point than linolenic acid. Fortunately, the boiling
points don’t have any significant affect on the use of the chemicals as fuels.
Table 2 – Properties of Methyl Esters from Vegetable Oils 1
Methyl Ester
Acid
Molecular Melt
Acronym Weight
ºC/ºF
Boil
Cetane
Heat Combust
ºC/ºF
Number (kg-cal/mole)
Methyl Caprylate
8:0
158.24
193.0/379.4 33.6
1313
Methyl Caprate
10:0
186.30
224.0/435.2 47.7
1625
Methyl Laurate
12:0
214.35
5.0/41.0
266.0/510.8 61.4
1940
Methyl Myristate
14:0
242.41
18.5/65.3
295.0/563.0 66.2
2254
Methyl Palmitate
16:0
270.46
30.5/86.9
418.0/784.4 74.5
2550
Methyl Stearate
18:0
298.51
39.1/102.4
443.0/829.4 86.9
2859
Methyl Oleate
18:1
296.49
-20.0/-4.0
218.5/425.3 47.2
2828
Methyl Linoleate
18:2
294.48
-35.0/-31.0 215.0/419.0 28.5
2794
Methyl Linoleneate 18:3
292.46
-57.0/-70.6 109.0/228.2 20.6
2750
Methyl Erucate
352.60
222.0/431.6 76.0
6454
22:1
Why not use the straight oil?
Biodiesel is intended to replace petroleum diesel as a fuel in Diesel engines. A common
question (which students may have, since much of the public does) is why not just use the
straight vegetable oil (SVO), rather than going to the trouble to convert it into biodiesel.
After all, Rudolf Diesel did initially invent his diesel engine to run on pure vegetable oil.
There are a couple of reasons why SVO isn’t as appealing as biodiesel.
First and foremost, is the fact that modern diesel engines use high tech injection pumps,
which don’t tolerate very viscous fluids. The viscosity of vegetable oil is considerably
higher than the biodiesel made from that oil. Most vegetable oils have viscosities around
30-50 “centistokes”, while most biodiesel has a viscosity around 5-6 centistokes.2 If a
person were to just pour vegetable oil into their fuel tank, with most diesel vehicles, the
fuel pump would fail fairly quickly due to the strain of pumping the very viscous oil.
That problem can be skirted somewhat by using a system to heat the vegetable oil before
it gets to the pump, reducing its viscosity to an acceptable level. In fact, this approach has
been taken by many people as it provides a method for them to run their diesel vehicle on
free waste vegetable oil from restaurants, without having to go to the trouble of turning it
into biodiesel. The most common approach is to put in a second fuel tank for the oil, and
use the coolant system of the vehicle to heat the second tank. The car would be started on
either diesel or biodiesel, and once the engine (and therefore the coolant) has heated up to
operating temperature - usually around 200F on most vehicles – the car can switch to
pulling fuel from the auxiliary tank holding heated vegetable oil. This approach can
work, but is not ideal for a few reasons. But, it can present an interesting project for
mechanically inclined students, and at several high schools and colleges around the
country, students have modified older diesel vehicles to run on straight vegetable oil in
this manner.
The main drawbacks of this approach are that most modern fuel injection pumps suffer
from increased wear from the high temperature of the fuel. The pumps simply aren’t
designed to tolerate having 200F liquid flowing through them. Additionally, the straight
vegetable oil does not burn as cleanly as biodiesel (due in large part due to the presence
of the glycerin in the SVO), resulting in worse emissions, and carbon buildup on fuel
injectors and inside the engine. Together, the effects to the injectors, injection pump, and
inside the engine make a vehicle running on SVO less reliable, and more polluting than a
vehicle running on biodiesel. A final reason for converting the vegetable oil into biodiesel
can be seen by comparing the melting points for the fatty acids shown in Table 1 to those
of their methyl esters shown in Table 2. The methyl esters all have lower melting points
than their corresponding fatty acids (and henceforth, the triglycerides made of those fatty
acids). The result is that straight vegetable oil would be more difficult to use in cold or
even moderate temperatures than biodiesel.
An important point to notice is that for the most part, the methyl esters with the lower
(and therefore preferable) melting points, unfortunately have lower (and therefore less
preferable) cetane numbers. Modern diesel engines generally require a cetane number of
at least 40, preferably 45 or higher. So, while from looking at Table 2, we might think
that the ideal biodiesel would be composed entirely of methyl linoleneate, due to the
extremely low melting/freezing point (-70º F), we should also notice that the cetane
number is far too low (20.6) for a fuel composed entirely of methyl linoleneate to be
acceptable.
Another point of interest is that other alcohols produce biodiesel molecules with lower
melting points. For example, isopropyl stearate has a melting point of 28º C, compared to
39.1º C for methyl palmitate.
3
But, the reaction can be more difficult with longer
alcohols, due to steric hindrance – longer alcohols do not fit as readily in the space
around the carbon with the double bond to oxygen during the esterification, slowing
reaction rates. The shorter the alcohol (methanol being the shortest), the easier it fits, and
the faster the reaction.
Differences between various vegetable oils
Looking at the properties of the various methyl esters demonstrates that the properties of
biodiesel – in particular the cold weather properties, could vary considerably depending
on what oil it is made from. Table 3 below lists a few different vegetable oils, and the
levels of various fatty acids they contain (bare in mind, in the oil the fatty acids are bound
to glycerin as triglycerides. The table lists the fatty acids themselves, but is not meant to
imply that they exist as free fatty acids in the oil). The fatty acid profiles are generalities,
as various plants (and animal fats, such as the tallow included) do have variability among
them, depending on growing conditions and other factors. A field in biodiesel research
focuses on breeding varities of various plants for ideal fatty acid profiles. The table also
includes the gel point, cloud point (these qualities are explained in section II.c of the
Lesson Ideas portion of this document), and cetane number for methyl ester made from
each oil.
Table 3 – Fatty Acid profile, and properties of methyl esters for various oils2
Rapeseed
Canola
Tallow
Soybean
Myristic (14:0
0
0.0
3.0
0.0
Palmitic (16:0
2.2
4.0
23.3
9.9
Stearic (18:0
0.9
2.4
17.9
3.6
Oleic (18:1)
12.6
65.0
38.0
19.1
Linoleic (18:2)
12.1
17.3
0.0
55.6
Linolenic (18:3)
8.0
7.8
0.0
10.2
Elcosenoic (20:1)
7.4
1.3
0.0
0.2
Behenic (22:0)
0.7
0.4
0.0
0.3
Erucic (22:1)
49.9
0.1
0.0
0.0
Properties of Methyl Esters of the oils
Cetane number
61.8
57.9
72.7
54.8
Cloud Point ºC
0
1
16
3
Gel/Pour Point ºC
-15
-9
16
-3
Data taken from http://www.biofuels.fsnet.co.uk/comparison.htm
Soap Formation
Soap can be made by combining sodium hydroxide (NaOH), water, and vegetable
oil. The water separates the sodium hydroxide, resulting in free Na+ ions. The vegetable
oil triglycerides are broken apart, separating the fatty acids and glycerin. The Na+ ions
attach to the fatty acids in the same place that the alkyl groups attach during
transesterification to produce biodiesel. The fatty acids with a sodium ion attached make
a soap (i.e. sodium palmitate).
Since a base is used both for making soap from vegetable oil and also as the catalyst for
breaking apart the vegetable oil molecule during transesterification, care needs to be
taken that one doesn’t inadvertantly make soap. The NaOH is combined with the alcohol
to make sodium methoxide, which is then added to the vegetable oil. Using too much
NaOH can result in soap formation, due to the excess sodium joining the fatty acids after
the vegetable oil molecules are separated.
With waste vegetable oils, free fatty acids are generally already present. These free fatty
acids will essentially always combine with a sodium ion during the processing, resulting
in saponification (soap formation). Unfortunately, that is an unavoidable result when
using this base-catalysed transesterification process (and is a reason why methods have
been developed for performing the reaction without a catalyst, with a non-alkali catalyst,
or an acid-base processes that first esterifies the FFAs into biodiesel). Since these free
fatty acids consume the catalyst, when waste vegetable oils are used, extra catalyst needs
to be added to account for that. Otherwise, not enough catalyst would be left for breaking
apart the triglycerides in the oil, as some would be consumed by the free fatty acids
(FFAs). This is the reason for doing the titration when using a waste vegetable oil
feedstock, so that extra catalyst can be added to account for the fact that some catalyst
will be consumed by the FFAs.
When oils with free fatty acids are used, the free fatty acids will be turned into soaps by
the alkali catalyst. As a result, the yield of biodiesel is lower for these oils, and the soap
needs to be removed. The process used for cleaning the biodiesel is known as “washing”,
in particular used for removing soaps. This process involves either bubbling water up
through the biodiesel (after glycerin separation), or misting water down on the top and
letting it flow down through the biodiesel (or a combination of both). The water pulls the
soaps out of the biodiesel as it passes through. The water eventually settles to the bottom,
and can be separated readily from the biodiesel.
STORAGE OF BIO-DIESEL

The flash point of biodiesel is higher than 100 degrees celsius (in fact, it is around
120 degrees). Thus, biodiesel is not subject to the regulations for flammable
liquids and has not been classified a dangerous substance.

Due to its quick biological degradability biodiesel is graded water hazard class 1,
i.e. it is only of minor harmfulness.
When storing biodiesel you ought to take the following points into consideration:
Storage location
o As biodiesel is an 'organic' substance it reacts to influences encouraging
oxidation, such as temperature, light and oxygen. Therefore, direct
sunlight should be avoided when storing biodiesel.
o It is of particular importance that the exchange of air as well as water
intake are avoided as biodiesel is hydrophilic.
Storage vessels: tanks
o Metal tanks are the most suitable vessels for the storage of biodiesel. The
varnish inside the tank must be resistant to biodiesel.
o Tanks with an inner coating of PVC are not suitable for the storage of
biodiesel.
Cleaning the tank
Biodiesel has the properties of a solvent. Thus, the deposits formed in the system by
diesel fuels are dissolved by biodiesel. That is why long-serving storage vessels ought to
be cleaned before filling them with biodiesel.
With the set-up of public petrol stations building regulations and safety measures
concerning water protectorates have to be taken that depend on the size of the tanks and
the respective local conditions.
The common safety precautions for the storage of flammable liquids in closed areas do
not apply as biodiesel is not subject to the regulations for flammable liquids for its high
flash point.
Expensive building measures such as keeping attached rooms resistant to fire and
providing
fire-fighting
equipment
are
not
necessary.
The maxime of environmental concern, however, does apply to biodiesel: plants for the
production, the treatment and utilization of substances that put water protectorates at risk
must be constructed, set up and run in a way that prevents the contamination of waters or
other long-term changes of their properties (§ 19g.Abs.1.WHG).
Due to the quick biodegradability of biodiesel and the very low degree of water toxicity
the following safety precautions ought to be taken depending on the size and shape of the
storage vessel:
1. It is sufficient to provide a leakproof, impermeable mounting similar to the type
of material used in roadworks (e.g. asphalt, concrete, cobbled floorspaces). The
area to be secured has got to comprise the area of action of the petrol pump
(length of the hose plus one metre).
2. Retention basins are to hold back potential small and large leakages from faulty
seals as well as the volume of the biggest receptacle (canisters, vats, containers)
and pallets for reloading.
3. Provide retention receptacles for the leakage volume that may occur until
automatic safety measures come into action (level indicator). If you use automatic
safety devices, you have got to consider the whole system of filling and
evacuation when you approximate the potential leakage volume.
4. If there are no automatic safety devices, you have to provide detention receptacles
for the leakage volume that may escape until suitable measures come into action.
5. Provide a connection to the local sewage system or a similar system (direct
passing-in, e.g. a waterproof shaft with overflow). Also, there should be a device
that monitors the level of condensed water which accumulates during filling and
handling.
6. In case the storage area is roofed, the measures described under point three are
unnecessary.
7. Single containers as well as systems of combined containers for cost reasons have
to be equipped with devices indicating the boundary limit. If containers are set up
outdoors, they must have crash protection.
EMMISION NORMS
Biodiesel properties are competitive with conventional diesel fuel in some emission
categories but problems were also identified for other kinds of emissions. It was shown
that poly-aromatic hydrocarbon (PAH) emissions were lower for neat vegetable oils
especially the alkylated PAHs which are common in the emission of conventional diesel
fuel (DF). Besides higher NOx levels, aldehydes are reported to present problems with
neat vegetable oils. Total aldehyde increased dramatically with vegetable oils and
formaldehyde formation was consistently higher than with DF. It was also reported that
component triglycerides (TGs) in vegetable oil can lead to formation of aromatics via
acrolein (CH2=CH-CHO) from the glycerin moiety.
Most studies conducted report that for short-term trials, neat oils gave satisfactory
engine performance and power output are often equal to or even slightly better than
conventional DF. However, vegetable oils cause engine problems. Studies on sunflower
oil, coconut and other oils as fuel noted coking of injector nozzles, sticking piston rings,
crankcase oil dilution, lubricating oil contamination and other problems. The causes of
these problems were attributed to the polymerization of TGs via their double bonds
which leads to formation of engine deposits as well as the low volatility and high
viscosity with resulting poor atomization patterns.
Alkyl esters. Biodiesel emissions are substantially lower than petroleum diesel emissions.
Compared to gasoline, biodiesel produces no sulfur dioxide, no net carbon dioxide, up to
20 times less carbon monoxide, and more free oxygen. Biodiesel has the following
emission characteristics when compared to petroleum diesel fuel:

Reduction of net carbon dioxide (CO2) and sulfur dioxide (SO2)emissions by
100%.

Reduction of soot emissions by 40-60%.

Reduction of carbon monoxide (CO) and hydrocarbon emissions by 10 - 50%.

Reduction of all polycyclic aromatic hydrocarbons (PAHs) and specifically the
reduction of the following
Carcinogenic PAHs:
Reduction of phenanthren by 97%.
Reduction of benzofloroanthen by 56%.
Reduction of benzapyren by 71%.
Reduction of aldehydes and aromatic compounds by 13%.

Reduction or increase of nitrous oxide (Nox) emissions by 5-10% depending on
Opacity or "K" Reading (m-1)
the age of the vehicle and the tuning of the engine.
2.5
2.32
2
1.5
1.24
1.03
1
0.81
0.43
0.5
0.35
0.24
0
0
200
1,400
3,900
5,033
15,663
16,928
Road Run Kilom eter (Km )
Figure 1. Reduction of Smoke Emission after Blending Petroleum Diesel with 1% CME
Illustration No. 1. Effect of CME on the Engine
POWER TORQUE CURVE
TORQUE (kg-m)
LSD
10.80
1% CM E-13
10.60
10.40
10.20
1% CM E-15
10.00
5% CM E-15
2% CM E-13
2% CM E-15
5% CM E-13
9.80
9.60
9.40
9.20
9.00
8.80
1500
2000
2500
3000
RPM
3500
4000
4500
3
Opacity or "K" Reading (m-1)
2.65
2.5
with 1% CME
w/o CME
1.9
1.89
2
1.6
1.53
1.5
1.05
1
0.79
0.54
0.5
0.39
0.28
0.19
0.26
0
0
900
1800
2700
3600
4500
Distance Travelled (Km)
Fig. 3. Dynamometer Test Result On C-190 Isuzu Diesel Engine.
Illustration No. 2. California Buses Opacity Test Result
Biodiesel Standard
Pursuant to the intent of the Clean Air Act to develop and utilize cleaner alternative
fuels, the Technical Committee on Petroleum products and Additives of the Department
of Energy (DOE/TCPPA) prepared a Philippine Coconut Oil Biodiesel Product Standard
and is adopted as the Philippine National Standard (PNS) for Biodiesel by the Bureau of
Product Standard (BPS) which the manufacturers should comply to ensure its
effectiveness when used either in its pure state or as a blend. The ASTM standard
being used in the United States was used as basis for this specification. Table 1 shows
the prepared PNS specifications.
Critical key points on CME fuel quality include; Flash point whose limit is set at
100oC to ensure the removal of excess methanol used during the manufacturing process.
Presence of residual methanol even at small amount reduces flash point. It can also affect
fuel pumps, seals and can result to poor combustion, Sulfated Ash ensures the removal of
catalyst. High level of catalyst in the fuel can result in injector deposits or filter plugging,
Acid number limits to 0.5 maximum. Higher than the set limit may cause fuel system
deposits and reduce the life of fuel pumps and filters, and Free and Total Glycerin
Number which measure the degree of conversion of oil into ester. If the value is too high,
fuel gumming and engine fouling will occur.
DOE/TCPPA also come up with conclusive inter-laboratory fuel test results (wherein
the petroleum laboratories participated) that 1%, 2% and 5% CME-PDF Blend (by
volume basis) still conform to the PNS for Diesel Fuel.
Table 1. PNS Specification for Biodiesel and the Test Method Used
Property
CME Limit
Test Method
Flash point Pensky Martens oC, min.
100.0
PNS 613 / ASTM D 93
Water & Sediments % vol. Max.
0.050
PNS 707 / ASTM D 2709
Kinematic viscosity @ 40oC, mm2/s
2.0 – 4.5
PNS 407 / ASTM D 445
Sulfated ash % mass max.
0.020
PNS 2025 / ASTM D 874
Sulfur @ mass max.
0.050
PNS 504 / ASTM D 2622
Copper strip corrosion 3 hrs @ 50oC max.
No. 3
PNS 379 / ASTM D 130
Cetane number, min.
42a
PNS 653 / ASTM D 613
Cloud point, oC max.
Report
PNS 706 / ASTM D 2500
Carbon residue,100% sample,% mass, max.
0.050
PNS 708 / ASTM D 4530
Acid number, mg KOH/g,max.
0.50
PNS 2024 / ASTM D 664
PNS 2026 / ASTM D 974
Free glycerin, % mass, max.
0.02a
PNS
2022 / AOCS Ea6-51
(1989)a
Total glycerin, % mass, max.
0.24a
PNS 2023 / AOCS Ca 14 -- 56
(1997)a
Phosphorus,% mass,max.
0.001
PNS 2028 / ASTM D 4951
Distillation AET 90% recovered oC, max.
360
PNS 2027 / ASTM D 1160
a
Transition standard
ADVANTAGES OF BIO-DIESEL
Biodiesel fuel has numerous advantages over conventional diesel that make it
desirable to consumers. First, the molecular construction of Biodiesel relative to
conventional diesel will, when burned, increase engine lubricity (a measure of an
engine’s efficiency at performing the essential task of lubrication). Given the importance
of lubrication in both the efficiency and lifespan of an engine, this is a significant benefit
of the fuel. Second, Biodiesel has a high ignition temperature compared to regular
petroleum diesel fuel (150°C vs. 52°C), which means that it can be transported quite
safely with normal vehicles. Third, as a result of its organic origins, Biodiesel is both
biodegradable and non-toxic; in fact, 100% Biodiesel is as biodegradable as sugar and
less toxic than table salt. Therefore, in the event of a fuel spill, there would be far less
damage to the affected environment than would occur with conventional diesel. Finally,
although not an advantage of the fuel itself, it should also be noted that Biodiesel can be
used in any diesel engine without major engine or fuel tank modifications. This is
significant because it means that consumers will have negligible switching costs in
adopting Biodiesel for their vehicles.
As mentioned above, switching costs to Biodiesel are low. However, they do
exist: while the use of Biodiesel does not require major infrastructure changes to the
engine, deterioration of rubber fuel hoses may occur with the use of Biodiesel due to the
methanol content in the fuel. As a result, rubber fuel hoses and seals may need to be
replaced with synthetic fluroelastomer equivalents such as Viton®. These products can,
however, be found in most auto supply stores or replaced easily by any auto mechanic for
a nominal charge.
SPECIFICATION OF BIO-DIESEL
The comparison of properties of Jatropha curcas oil and standard specifications of
diesel oil
Specification
Standard specification of Jatropha curcas oil
Specific gravity
0.9186
Flash point
240/110°C
Carbon residue
0.64
Cetane value
51
Distillation point
295°C
Kinematics Viscosity
50.73 cs
Sulpher %
0.13%
Calorific value
9,470 kcal/kg
Pour point
8°C
Colour
4
Physical and chemical properties of diesel fuel and Jatropha curcas oil.
Property
Jatropha curcas Oil
Viscosity (cp) (30°C)
Speciflc gravity (15°C/4°C)
0.917/ 0.923(0.881)
Solidfying Point (°C)
Cetane Value
Flash Point (°C)
110 / 340
Carbon Residue (%)
Distillation (°C)
284 to 295
Sulfur (%)
0.13 to 0.16
Acid Value
1.0 to 38.2
Saponification Value
188 to 198
Iodine Value
90.8 to 112.5
Refractive Index (30°C)
Standard specification of Diesel
0.82/0.84
50°C
0.15 or less
> 50.0
350°C
> 2.7 cs
1.2 % or less
10,170 kcal/kg
10°C
4 or less
Diesel Oil
5.51
3.6
0.841 / 0.85
2
51 47.8 to 59
0.14
80
0.64 < 0.05 to < 0.15
< 350 to < 370
< 1.0 to 1.2
1.47
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