MODIFICATION AND EVALUATION OF A MOTORIZED NEEM
SEED (AZADIRACHTA INDICA) DECORTICATOR
M.A. Adedeji*, A. Ayodele and A. Olaniyi
Department of Agricultural and Bio-Environmental Engineering Technology, Federal
Polytechnic, Bauchi, Bauchi State, Nigeria
*-Corresponding author email: firstname.lastname@example.org +230-7068154452
Abstract—Tropical oilseeds both edible and nonedible nuts are important economical crops
and are used widely for human and livestock consumption while in some cases for industrial
usage; the by-products also have a variety of uses. Their decortication is necessary to remove
the outer layers which previously provided physical protection to the oil-rich kernel and to
achieve the economic recovery of primary and secondary products.
Neem seed (Azadirachta indica) decorticator was modified, fabricated and evaluated using
locally available materials. It consists the hopper, decorticating, cleaning and the collection
units. The decortication action is accomplished through a process in which the oilseed is
'cracked open' and the embedded kernel is recovered when the seed is trapped in the clearance
between the moving drum with fixed circular bars and the fixed concave. The kernel is collected
through the collection unit while chaff is blown out through the open space at the backside of
the machine. The performance test which was conducted at a moisture content of 10.5%
showed that the machine has a decorticating efficiency of 72.33 %, cleaning efficiency of 22.6
%, 4.0 % broken seeds and 1.42 % un-decorticated seeds. The machine capacity was 60.0 kg/h
at a constant drum speed of 180.0 rpm.
Keywords— neem seed, decorticator, threshing efficiency, moisture content and machine
A paper presented at the 2nd National Academic Conference scheduled for M.L. Audu Hall,
Federal Polytechnic, Bauchi, Bauchi State, from Thursday 5th to Friday 6th November, 2015.
Neem tree (Azadirachta indica) is a member of the mahogany family “meliaceae”. It is one
species in the genus “Azadiracha” and is native to Indian subcontinent, growing in tropical and
semi-tropical regions. Other vernacular names include Neem (Hindi, Nepali, Urdu), Nim
(Bengali), Nimm (Punjabi), Arya Veppu (Malayalam), Lindo (Gujarati language), Kadu-Limba
(Marathi), Dongo yaro (in some Nigerian Languages), Margosa, Neeb (Arabic), Nimtree,
Vepu, Vempu, Vepa (Telugu) (Adedeji and Owolarafe 2015).
In Nigeria over four millions of neem trees have been planted in the northern part especially in
Borno, Kano, Katsina and Sokoto states; and rich in protein. About 3,500 hectares of land is
under cultivation in Kebbi, Sokoto and Zamfara states, with an average density of about 1,200
trees per hectare. (Amwayo and Maiganda, 2013). In Nigeria, neem form about 90% of forestry
established in 12 states within the savannah zone under the afforestation programme. It may
grow up to 15m tall under ideal conditions and is reported to live up to 200 years. It takes about
five years to produce the first fruit crop but can produce a good yield in the third year. Neem
tree produces flowers between February and May with profuse clusters of small white flowers.
The fruits are drupes, turning golden yellow on maturity, which occurs during June to August
in India. A full grown tree can produce 30-100 kg fruit depending on rainfall, soil type and
ecotype. About 50 kg of fruits yield 30 kg of seed giving 6 kg of oil and 24 kg of seed cake.
The seeds are about 10.24 to 16.68 mm major diameter, 4.52 to 7.11 mm minor diameter and
4.77 to 7.25 mm intermediate diameter, while the kernel is 6.17 to 14. 16.00 mm major
diameter, 2.40 to 5.12 mm minor diameter and 2.47 to 5.46 mm intermediate diameter
containing about 30 to 40 percent oil. A 5 to 6 years old tree can yield 20 kg kernels (Adedeji
and Owolarafe, 2015). The yield of 20.5 kg fresh fruit for a fully grown neem tree was reported
in Nigeria and an average yield of 17.71 kg in Nigeria (Sokoto and its environment). The large
number of the neem trees and its yield in the northern part of Nigeria is an advantage for its
use. (Amwayo and Maiganda, 2013).
Economic Importance of Neem Oil
Neem oil is a non-edible vegetable oil pressed from the kernels of the neem seeds. The oil
contains qualities of steroids, including beta-sitosterol (used to treat men suffering from
enlarged prostate glands) as well as linoleic and olei acids (Omega 6 and 9), and is found to
contain the well-known omega 3 fatty acid (used to prevent arterial sclerosis) (Adedeji and
Owolarafe, 2015). Also there is a general concept that in those countries where neem has been
grown for ages, it has also been used for a long time. According to a report from GTZ, Germany
(2000), neem has been used for more than 50 years in various Asian and African countries,
whereas in industrialized countries neem has been utilized for the last 20 to 25 years only.
Dental hygiene using the thin twigs of neem trees is a traditional use in India and established
to help prevent paradontosis and other gum related diseases (Daniel, 2014). Stomatitis is also
cured by an extract from bark of the neem tree. Nimodent, a product of Hamdard Co., Pakistan
and neem tooth paste and powder made by Calcutta Chemicals, India is effective dentifrice
products (Koul and Wahab, 2007).
Production of Biodiesel from Neem
An enormous increase in the number of automobile in recent years has resulted in greater
demand for petroleum products. With crude oil estimated to last only for few decades,
therefore, efforts are underway to research into alternatives to diesel. Of the various alternate
fuels under consideration, biodiesel, derived from esterified vegetable oils, appears to be the
most promising alternative fuel to diesel due to some reasons (Adedeji and Owolarafe, 2015).
Biodiesel is better than the conventional fossil fuel as it does not emit harmful fumes and is a
cheaper source for generating fuels. Using biofuel is the only way to lessen the environmental
pollution and lessen the usage of conventional fuels (www.genetix.com ). A lot of research
work has been carried out using vegetable oil both in its pure form and also in modified form.
Studies have shown that the usage of vegetable oils in pure form is possible but not preferable.
Table 1 illustrates the physicochemical properties of vegetable oils as compares with diesel
(ASTM D975). Esterified neem oil as a biodiesel satisfied the important fuel properties as per
ASTM D975 (Anbumani and Sing, 2010).
Neem in Reforestation and Agroforestry
Neem is a very valuable forestry species in India and Africa and is also becoming popular in
tropical America, the middle-east countries and Australia. Being a hardy, multipurpose tree, it
is ideal for reforestation programs and for rehabilitating degraded, semiarid and arid lands.
Neem is useful as windbreaks and in areas of low rainfall and high wind speed. In the Majjia
Valley in Niger, over 500 km of windbreaks comprised of double rows of neem trees have been
planted to protect millet crops which resulted in a 20 per cent increase in grain yield
(Erakhrumen and Ogunsanwo, 2010).
Table 1: Physicochemical properties of vegetable oils as compared with diesel (ASTM D975)
Properties before Blend
Cetane number (CN)
Calorific value (MJ/kg)
After blending (20% by volume with diesel)
Cetane number (CN)
Calorific value (MJ/kg)
Source: Anbumani and Singh (2010)
This is done with hand by applying a little pressure on the shell of a previously dried neem
seed, after manually depulping the fresh fruits. It is the oldest method known to mankind before
the advent of technology. There is a very minimal or no breakage of the kernel and the
separation of the kernel from the hull are done simultaneously during the hulling operation.
This method is slow and involves a lot of human labour and drudgery. Another traditional
method is by gentle pounding of the neem seed in a mortar by a pestle. In these later methods
the kernel suffer a great deal of breakage and the separation of the kernel from the chaff can be
achieved through winnowing, although, the shelling is achieved at a faster rate and less labour
is required (Akande, 2014).
Mechanical decortication of neem seed
Decortication is invariably done by powering the decorticating machine and pouring the neem
seeds through the hopper. Decorticator sometimes gives dried fruits 70% shell, 25% kernel and
for depulped seed 45% shell 50% kernel, wind-age loss 4 to 5 %. Maximum oil yields after 2
to 5 months of collection. (Vijayalakshmi et al., 1997).
Effect of moisture content on the physical properties of neem seed
Adedeji and Owolarafe (2015) reported that moisture has significant effects on physical
properties such as axial dimensions, geometric mean sphericity, volume, surface area, aspect
ratio, 1000-unit mass, true density, bulk density, and density ratio and percentage porosity.
Effect of moisture content on some mechanical properties
Adedeji and Owolarafe (2015) stated that moisture has significant effects on some mechanical
properties studies which are compressive load, stress and strain at yield, and energy at yield.
These properties are useful in determining the amount of energy that will required to
decorticate the seeds.
Materials and Methods
Collection of neem fruits
Ripened fruits were collected by shaking the tree branches so that the neem fruits should drop
on the polythene spread under the tree. (Adedeji and Owolarafe, 2015).
Depulping of the neem fruit to obtain the neem seed
Collected fruits were kept immediately in warm water to avoid fungal growth. These fruits was
kept in water between 12 hours to further soften the pulp. Mechanized scrubbers, macerators
and washers can be used for larger quantities. Depulping was done manually by rubbing and
washing the fruits in order to remove the pulp. (Adedeji and Owolarafe, 2015).
Method of drying of the neem seed
Depulped seeds were spread in thin layers for sun drying, however, in cloudy, rainy weather
use of fans, and hot air blowers are suggested. A safe storage seed moisture level of 9 – 15%
(w.b) was recommended as against 40-50% (w.b) moisture at the time of collection of fruits.
(Adedeji and Owolarafe, 2015).
The materials used in constructing this decorticator were locally sourced which are mainly mild
steel metal sheet, cast iron and angle irons. They were selected based on durability, suitability
The machine was fabricated with a mild steel sheet metal and the frame was made from angle
iron. After the production of the machine, the performance test was carried out using one level
of moisture content. The machine is portable, cheap and simple in operation that will allow any
local neem producing farmer within the same vicinity to use the machine together, one after
the other. The main machine components are listed in Table 2 below.
Table 2: The main components of the machine and the material to be used
350 x 350
320 x Ɵ 20
360 x Ɵ 20
Pulleys (main & fan)
Ɵ 80 and Ɵ 60
2 x 2 (angle bar)
350 x Ɵ 380
350 x 800 x 400
Drum diameter determination
The drum diameter was determined using the equation 1;
where; D= diameter of the drum (mm)
U = peripheral velocity of the drum (m/s)
Nb = number of beaters (38 beaters)
ATs = time interval for successive strikes (sec).
Determination of the pulleys velocity ratios
The velocity ratio of the pulley is defined as the revolution per minute of the driven divided by
the revolution per minute of the driver equation 2. This ratio was determined using equation 2
= = …………………………………….. 2
Source: Adedeji and Danladi (2015).
Fan design calculations
The free vortex theory was considered for the fan design calculation. The minimum air flow
velocity and its volumetric flow rate were determined in such a way that the draught from the
fan will only blow away the threshed chaff or empty pods while the rice grains were not blown
off. The head developed during operation by the fan is given by the Bernoulli’s equation 3;
− = /
( ) ………………………….………… 3
where; = ℎ ℎ ℎ ,
= ℎ ℎ ℎ ,
= , .
= ℎ ,
= ℎ ℎ ,
Determination of power requirement
The power required to power the thresher was calculated using equation 4 given below;
where; = ,
= , = ,
Source: Adedeji et al., (2015)
Results and Discussion
The test operation was carried out in two stages: the first operation was at no load and for
inspection of the machine for safe operation. The machine was ran for about 15 min. The
second operation was on-load using 5.0 kg of neem seed at moisture 10.5% (w.b). The material
was fed into the machine through the hopper, a digital stop watch was used to take the time of
the operation. The machine was allowed to run for 5.0 min. extra 3mins was given for the
materials in machine to come out, the results obtained were recorded in Table 3. Plate 1
illustrates the modified neem seed decorticator.
The performance test of the machine was determined at only one moisture content level of
10.5% (w.b). Table 3 shows the summary of the test results obtained;
Table 3: Test result summary
Duration of operation (min.)
Feed rate Wr (kg/h)
Fully decorticated Qd(kg)
Decorticated but broken seeds Qb(kg)
Un-decorticated seeds Qu(kg)
Weight of clean seeds collected Qc(kg)
Weight of winnowed chaff at the chute Qs(kg)
Weight of chaff with seeds Qss (kg)
Total weight of shells Qt(kg)
1. Decorticating efficiency = × 100%........................................5
= 0.7233 × 100%
2. Percentage un-decorticated = × 100%.........................................6
60 × 100%
= 0.014167 × 100%
3. Percentage damage = × 100%............................................7
= 0.04 × 100%
4. Winnowing (Cleaning efficiency) = × 100%...............................8
= 0.226 × 100%
Table 4: Shows the summary of result of performance test of neem seed decorticator
10.5 % (wb)
Input capacity kg/h
Plate 1: Modified neem seed decorticator
From tables 3 and 4, the results obtained show that the machine has 72.33 % decortication
efficiency and 22.6 % cleaning efficiency, with 10.5 % (wb) moisture content 1.42 % and 4.0
% for un-decorticated seeds and broken seeds, respectively.
Conclusions and Recommendations
The objective of the research work was achieved, the decorticating machine that can handle
bulk neem seed was modified and fabricated with 72.33 % decorticating efficiency and
cleaning efficiency of 22.6 %. Although this result is lower when compared with result
obtained by Adedeji and Danladi (2015). They reported machine decorticating efficiency of
83.20 %, the sieve loss of 23.67 % with machine cleaning efficiency of 78.9 %.
The following conclusion could be deduced from this study;
1. The modification and fabrication was carried out successfully.
2. The operation noise was a little bit on the high side.
3. The aim of the project has been achieved.
We hereby recommend that the following should be improved on for further modification of
1. The cleaning efficiency of the machine should be improved upon.
2. A bigger diameter pulley is highly recommended in order to further reduce the drum
3. The vibration and noise of the machine should be looked into.
4. The machine operator should use ear-plug to protect him from operational noise from
5. More moisture levels should be used in order to check the effect of moisture on the
6. Lighter material should be used for the fan blades for effective winnowing effect.
7. The concave and the clearance should be made adjustable.
8. The beater could be made of a plastic or rubber material instead of metallic material.
9. Wheels should be incorporated to make the machine mobile for easy transportation
during field operation and attachable to a tractor.
10. The outlet for the chaff should be wider.
11. A gate should be provided at the chute end for easy collection of the kernels and
12. Effect of drum speed and moisture content on the decorticating efficiency.
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