http://www.ngrguardiannews.com/2015/07/science-towards-a-clean-and-developed-environment-6/
[Nigeria could hardly do worse than continuing to let Shell and other
multi-nationals develop their fossil oil resources.]
Science towards a clean and developed environment (6)
By Dr. Adeleke Atanda Abiodun on July 16, 2015
Production of biodiesel from castor oil
Madam Rector Ma, in continuation of our efforts towards solving the
increasing energy problems in Nigeria, we conducted a research on the
production of biodiesel from the castor oil. The high energy demand in
the industrialized world as well as in the domestic sector and pollution
problems caused due to the widespread use of fossil fuels make it
increasingly necessary to develop the renewable energy sources of
limitless duration and smaller environmental impact than the traditional
one.
This has stimulated recent interest in alternative sources for
petroleum-based fuels. The alternative fuel must be technically
feasible, economically competitive, environmentally acceptable, and
readily available. However, biodiesel is an alternative biodegradable
and non toxic fuel, which is essentially free of sulfur and aromatics.
It is essentially produced by transesterification reaction of vegetable
or waste oil with a low molecular weight alcohol, such as ethanol or
methanol. Industrially the most common method of biodiesel production is
a basic homogeneous reaction.
The demand for alternative energy sources is frequent, because there is
a progressive decrease of the world’s petroleum. Vegetable oil fuel or
biodiesel is a potential substitute for diesel fuel because it is made
from renewable resources. The American Society for Testing and Materials
defines biodiesel fuel as monoalkyl esters of long chain fatty acid
derived from a renewable lipid feedstock such as vegetable oil or animal
fat. Among the biodiesel advantages, it can cite: biodegradability, no
toxicity, renewable, reduction in greenhouse gas emission and so on 79.
Biodiesel is embrace globally because it is an eco-friendly alternative
diesel fuel prepared from domestic renewable resources i.e vegetable
oils (edible or non-edible oils) and animal fats, which runs in diesel
engines – cars, buses, trunks, construction equipment, boats,
generators, and oil home heating units.
Biodiesel is non toxic, biodegradable. It reduces the emission of
harmful pollutants (mainly particulates) from diesel engines (80% less
CO2 emission; 100% less sulfur dioxide) but emissions of nitrogen oxides
(precursor of ozone) may increase.
Biodiesel has a high cetane number (above 100, compared to only 40 for
diesel fuel). Cetane number is a measure of a fuel’s ignition quality.
The high cetane numbers of biodiesel contribute to easy cold starting
and low idle noise.
The use of biodiesel can extend the life of diesel engines because it is
more lubricating and, furthermore, power output are relatively
unaffected by biodiesel.
Biodiesel replaces the exhaust odour of petroleum diesel with a more
pleasant smell of popcorn of French fries.
Biodiesel can be used either in the pure form or as without any major
modifications. Its biodegradability makes it eco-friendly.
Madam Rector Ma, it is worthy to note that a variety of oils can also be
used to produce biodiesel. These include; virgin oil feedstock; rapeseed
and soybean oils are most commonly used, Waste Vegetable Oil (WVO) and
Animal fats including fallow, lard, yellow grease, chicken fat, and the
by-product of the production of omega-3 fatty acids from fish oil 80,
and Oil from halophytes such as salicornia bigelovii, which can be grown
using salt water in coastal areas where conventional crops cannot be
grown, with yields equal to the yields of soybean and other oil seeds
grown using fresh water irrigation81.
Many researchers had advocated that waste vegetable oil is the best
source of oil to produce biodiesel, but since the available supply is
drastically less than the amount of petroleum-based fuel that is burned
for transportation and home heating in the world; this local solution
does not scale well. Vegetable fats and oils may however be classified
as edible or not edible. Examples of inedible vegetable fats and oils
include processed linseed oil, lung oil, and castor oil used in
lubricants, paints, cosmetics, pharmaceuticals, and other industrial
purposes 82.
Castor oil is a vegetable oil obtained from the seeds of the plant,
Ricinus communis, sometimes known as Ricinus oil. Castor oil is a large
plant native to tropical Africa and Asia, the shrub is a flowering plant
up to 12m high. It is cultivated widely in the tropics for its seeds,
from which castor oil is extracted, and in temperate regions as an
ornamental shrub seldom taller than 2m. Castor oil is pale amber viscous
liquid with mild or no odour or taste, its boiling point is 3130C
(5950F) and its density is 931kg.m3. It is a triglyceride in which
approximately 90 per cent of the fatty chains are ricinoleic acid. This
oil has an ash content of about 0.02 per cent the percentage for sulfur
is less than 0.04 per cent. The higher the cetane number (CN), the
better the fuel will be when used as a diesel. The CN of the majority of
biodiesel fuels is actually higher than petrol or diesel, and the cetane
number of castor oil biodiesel is in a good range for diesel engines83.
Castor plant has many uses, particularly the thick, yellowish or almost
odourless oil and obtained from the seeds. The seeds with hulls removed
contain 40 to 60 per cent oil. Although castor oil is not edible, it is
more versatile than other vegetable oils and it is widely used as a
starting material for many industrial chemical products because of its
unique structure. It is one of those vegetable oils that have found
usage in many chemical industries.
In the search for more environmentally friendly fuels, the use of castor
oil as ‘ Biodiesel ‘ has proven to have technical and ecological
benefits, and stands as an opportunity for agricultural development in
arid and impoverished areas through the tropics and subtropics globally.
Madam Rector Ma, it is important to mention the action process in this
study; the process of converting castor oil into a product that can be
used as diesel is called transesterification.
We purchased the castor seeds (or beans) from a market in Umuoji local
government area of Anambra state, Nigeria. The castor beans were made to
undergo various processing in the course of its preparation for extraction.
We cleared, dried, winnowed i.e. the separation of the shell from the
nibs (cotyledon) by using tray to blow away the cover in order to
achieve very high yield, and we grinded the beans thus reduced the size;
300ml of normal Hexane was poured into round bottom flask. 10g of the
sample was placed in the thimble and inserted in the center of
extractor; the soxhlet was heated at 60oC. When the solvent was boiling,
the vapour rises through the vertical tube into the condenser at the
top. The liquid condensate drips into the filter paper thimble in the
centre, which contains the solid sample to be extracted.
We determined moisture content of castor seeds, percentage of extracted
castor oil, acid value, saponification value, iodine value, specific
gravity, refractive index, pH value we carried out solvent extraction of
the oil from castor seed in relation with time of extraction as the only
optimizing parameters while keeping other parameters (e.g. particle
sizes, temperature e.t.c.) constant.
In line with our objectives of the study, we extracted and characterized
oil from castor seed and its utilization in the production of biodiesel.
The extracted oil was thereafter refined, and the same analysis carried
out on the crude castor oil were then repeated for the refined castor
oil and the value obtained were compared with the ASTM specification for
quality castor oil.
However, in order to produce biodiesel from the castor oil, the action
process earlier mentioned i.e transesterification was demonstrated, in
this process, the castor oil is chemically reacted with alcohol like
methanol or ethanol in the presence of catalyst like sodium hydroxide or
potassium hydroxide. The triglycerides are converted into alkyl esters,
which is the chemical name of biodiesel.
We found out that products of the reaction include not only biodiesel,
but also by-products, such as soap, glycerin, excess alcohol and trace
amounts of water. Then, the residual methanol was removed by
distillation and washed out with water as a waste.
The biodiesel (after separation from glycerin) was purified by washing
gently with warm water to remove residual catalyst or soaps, dried and
then sent to storage.
Properties of biodiesel were tested according to ASTM D6751 standard.
The result obtained for the percentage moisture content, 6.1 per cent
fall within the range of the moisture content found to be between 5 to 7
per cent 83. The result obtained from the percentage oil content 33.2
per cent also fall within the range of the percentage oil content (30 –
55 per cent) of castor beans84.
The chemical properties analysis shown in Table 3 indicates that the
acid value is higher in crude oil due to free fatty acid present, while
it is less for the refined oil as a result of the strength of 0.1M Na0H
used in the treatment of the crude oil, which must have neutralized some
of the free fatty acid present in it.
The results for the saponification value of the crude and refined oil
were found to be 183.mg KOH/g of oil and 177.99mg KOH/g of oil
respectively. This shows that, for the crude oil, more alkaline would be
required to enable it neutralize the available free fatty acid liberated
by the oil, when compared with the refined oil.
However, the low cloud and pour points makes biodiesel a good
alternative in winter conditions and it implies a higher level of
stability at low temperature, making biodiesel an ideal combustible for
those regions with extreme seasonal weather as it does not require any
kind of additives to converse its fluidity 85, The viscosity obtained at
400C is 4.97; falls within the specification which ranges between 1.9 –
6.0. This kinematics viscosity which is higher in biodiesel than the
normal diesel, improves injector efficiency.
We concluded that the percentage oil yield from castor seed using
solvent extraction was found to be 33.2 per cent of the total weight of
155g. The castor oil produced in this work was evaluated and some of its
physical and chemical properties were determined. All these resulted in
improving the quality of the castor in terms of the viscosity,
saponification value, acid value, pH and made it a suitable feedstock in
the production of biodiesel. The biodiesel produced by the
transesterification process has much lesser viscosity which makes it
capable to replace petroleum diesel in the diesel engines. Therefore,
the use of castor oil in the production of biodiesel will help in
producing a more environmental friendly fuel, since biodiesel is
non-toxic and biodegradable, whereas petroleum based oils are potential
health hazards, and take a very long time to biodegrades, thus can
damage the environment when concentrated.
It is recommended that more awareness should be created concerning the
use of a fuel (biodiesel) whose combustion does not generate sulphur
compound and generally does not increase the amount of CO2 in the
atmosphere.
Government should encourage industrial production of castor seed oil
which is suitable renewable feedstock and the best substance for
producing biodiesel, because it is the only one that is soluble in
alcohol, and does not require heat and the subsequent energy requirement
of other vegetable oils in transforming them into fuels.
Further research should be carried out on the use of hydraulic pressing
as an alternative method in the extraction of castor oil because of its
high yield of percentage oil compared to the solvent extraction process.
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