development, utilization and adaptation of …

Journal of Science, Engineering and Technology, Vol. 7 (1), March 2020: pages 116-128

116

DEVELOPMENT, UTILIZATION AND ADAPTATION OF THRESHERS FOR

EFFECTIVE RICE PRODUCTION IN NIGERIA – A REVIEW

*Odey, S. O.1, Ovat, F. A.2 and Ofem, M. I.3

1Department of Wood Products Engineering, Cross River University of Technology, Calabar,

Nigeria. 2, 3Department of Mechanical Engineering, Cross River University of Technology, Calabar,

Nigeria.

*Correspondence Author email & Phone: [email protected], 07034575615

ABSTRACT

Review was done on the development, utilization and adaptation of threshers for effective

rice production in Nigeria to meet the needs of the ever-growing population. Locally

produced rice, are highly nutritious, but characterized by dirt, stones, and unpolished

surfaces, making it unattractive, poorly priced, unavailable due to technology and less

accepted by individuals. Critical factors responsible for low quantity and quality of rice

production were unveiled. Developed machines are not adapted and utilized by farmers due

to lack of linkage between stakeholders. Secondly, some threshers had constraints as

reported by their tests results. It is recommended that researchers, institutions and relevant

authorities should collaborate in the rice value chain for increased quantity and quality of

produce through appropriate funding of research, linkage between researchers and industries,

subsidies by governments, provision of funds, grants and soft loans, intensification of

extension services and need for enforcement of rice quality standard. Steps in the

development of rice threshers were also presented to enhance good research. Development,

adaptation and utilization of rice threshers would reduce drudgery, increase production,

elevate income and improved standard of living. Conscious domestication of rice production

using machineries by stakeholders would discourage import and make it available,

affordable and accessible to Nigerian consumers.

Key Words: Rice, Threshing, Machine, Development, Utilisation, Adaptation

1. INTRODUCTION

Globally, rice is a staple food to over 50% of

the people, providing over 19% of global

human per capita energy. Human

consumption accounts for about 78% of

global production while the balance serves

other uses such as feed. Over 3.5 billion

individuals depend on rice for more than 20%

of their daily calories, with Asia, South

America and Sub-Sahara Africa the largest

consuming regions (KPMG, 2019). Rice is a

commodity with the third-highest worldwide

production after sugarcane and maize

(FAOSTAT, 2012). Worldwide there are

different varieties of rice species names like

Oryza sativa, Doongara, Jarrah, Kyeema,

Reizip are a few species (IRRI, 2009). More

than 40% of the rice consumption in West

Africa is imported, which represents 2.75

million tonnes per year (Ani et al., 2020). It

is estimated that rice sustains the livelihood

of more than 100 million people and its

production has employed more than 20

million farmers in Africa.

Rice is the third-most consumed staple food

in Nigeria (after maize and cassava) and has

become a food security crop due to its

increased significance in the country. As one

of the most consumed staples in all geo-

political zones and socioeconomic classes in

Nigeria, rice has a consumption per capita of

32kg. In the past decade, consumption has

increased 4.7%, almost four times the global

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Journal of Science, Engineering and Technology, Vol. 7 (1), March 2020

117

consumption growth, and reached 6.9 million

tonnes in 2019, accounting for 20% of

Africa's consumption. Only about 57% of the

6.9 million metric tonnes of rice consumed in

Nigeria annually is locally produced, leading

to a supply deficit of more than 3 million

metric tonnes. With rapid population growth

expected to exceed 200 million by 2020, it is

expected that the demand for rice will be

sustained and increased in the foreseeable

future. Apart from being an important food

security crop, it is an essential cash crop for

small-scale farmers who commonly sell 80%

of total production and consume only 20%.

Rice generates more income for Nigerian

farmers than any other cash crop in the

country (KPMG, 2019 and Ani et al., 2020).

In Nigeria, rice consumption far exceeds

production with a yearly average production

deficit of about 2.4 million tonnes recorded

between 2007 and 2018. In order to meet the

present deficit due to insufficient local

production, Nigeria imports rice from several

exporting countries to increase its total

supply (Morse, 2020). In 2018, 3 million

tonnes of rice was imported into Nigeria, via

its shipping ports as well as informal cross-

border channels (importation through land

borders is prohibited). Nigeria imports most

of its rice from Thailand, India and the USA,

incurring a bill of about $5 million daily.

According to Udemezue (2018), even during

the rice import ban period, Nigeria was still

importing several hundred thousand tonnes

of rice per year through illegal trade. The

researcher concluded that the Statistics of

rice production in Nigeria clearly shows that

the country needs 7 million metric tonnes of

its demand. Currently, Nigeria is capable of

supplying only 49% of domestic demand.

However, rice production in Nigeria keeps

growing, but it will not be enough to supply

the domestic demand of the whole country in

the next several years.

KPMG (2019) stated that almost all states in

Nigeria produce rice. However, the North-

Western region of the country produces the

highest volumes (about 72% of total rice

production), followed by the North Central

region and the southern region. Nigeria is the

largest producer of rice in West Africa (2nd

in Africa, after Egypt). The average yield in

the country is approximately 1.8 metric

tonnes per hectare. A total land area of 3.2

million hectares was harvested by 1.43

million farmers in the 2018/2019 season. The

two types of rice mainly cultivated in Nigeria

are the African Rice (Oryza glaberrima) and

the Asian rice (Oryza sativa). In recent times

however, new hybrid varieties have been

introduced such as NERICA (Manful and

Fofana, 2010).

Folami et al. (2016) asserted that local rice

production faces competition from imported

rice, which is favoured for its long white,

clean grains, stones free but taste less than the

local varieties. Eliminating stones from

Nigerian rice with locally available materials

at low cost when compared with expensive

imported ones, would allow Nigerian locally

produce rice to be appreciated better than

imported rice. Raising the quality of local

rice might discourage rice importation, whilst

boosting local production. Thus, rice

processing machines produced in developed

countries are mostly unaffordable by rural

farmers, hence there was need to develop cost

effective/efficient machines produced from

available local materials desirable in food

industry that meets the need of the rural

farmers.

Grain loss and damage are significantly

affected by threshing performances

(Alizadeh and Bagheri, 2009; Spokas et al.,

2008; Amare et al., 2015)). Hence, many

researchers put their efforts to investigate

grain-threshing devices, and different kinds

of grain threshers or threshing components

have been developed since 1820s (Li et al.,

2012; Li et al., 2017). Fu et al. (2018) stated

that a higher level of threshing theory and

technology are still the unswerving pursuit

due to the fact that they always seriously

affect grain loss and damage. Loss rate is a

major parameter to evaluate in the

performance of grain threshing. Reducing the

Odey, Ovat & Ofem: Development, Utilization and Adaptation of Threshers for Effective Rice Production in Nigeria – A Review

118

mechanical loss may be a more practicable

means to improve quality of grain threshing

(Xu et al., 2008). Likewise, damage rate is

another direct index of grain threshing which

negatively affects the market value and

storage. Many mechanical improvements

have been made empirically to reduce the

grain loss and damage.

1.1 Objective of the study

The objective of this study is to review the

development, utilization and adaptation of

threshers for effective rice production in

Nigeria to meet the needs of the ever-growing

population.

1.2 Rice Threshing

Rice as a food stuff passes through different

stages of processing of which threshing is one

of the major stages. Fu et al. (2018) revealed

that threshing is the most important function

of grain harvester. Grain loss and damage in

harvesting are significantly related to

threshing theory and technology. Grain loss

and damage in harvesting are significantly

affected by threshing performances (Spokas

et al., (2008); Elizadeh and Bagheri, 2009;

Zareiforoush et al., 2010; Khir et al., 2017).

Hence, many researchers put their efforts to

investigate grain-threshing devices, and

different kinds of grain threshers or threshing

components have been developed. The

process of removing grains from the panicles

of crops like rice, sorghums, wheat, beans,

guinea corn is known as threshing (Ajis and

Lanya, 2018). According to Okusanya and

Oladigbolu (2020) threshing is the first and

the most important post-harvest operation of

rice crop processing. It involves the

detachment of hulled grains from the

harvested straw. The threshing machine is a

devised for the separation of grain from stalks

and husks. This step requires threshing

machine with efficient operation. Threshing

is an integral part of post-harvest activities

for rice processing. There are four kinds of

threshing principles including impact,

rubbing, combing and grinding. Four types of

contact models between grain and threshing

components have been constructed

correspondently (Azouma, et al. (2009);

Ajavi et al., 2014); Xianfei et al. (2018); Ajis

and Lanya (2018); Fu et al., (2018); Bariya et

al. (2019)

1.3 Threshing Methods

Harvested paddy bunches may be stacked on

the plot. The in-field storage method results

in a pre-drying of the rice ears before

threshing, the purpose of which is to separate

seeds from panicles (Olugboji, 2004).

1.3.1 Traditional Method

The traditional threshing of rice is generally

done by hand. Thus, bunches of panicles are

beaten against a hard element (e.g. a wooden

bar log, bamboo table, or stone). In many

countries in Asia and Africa, and in

Madagascar, the crop is threshed by being

trodden underfoot (by humans or animals);

this method often results in some losses due

to the grain being broken or buried in the

earth (Food Agency Organization, 1995).

Another manual method still being practiced

by most rice farmers in Nigeria is the use of

clubs and sticks in beating the straw to

remove the grain from the panicle. In some

cases, the paddy stalk is held by hand, and the

panicle of paddy is struck against the hard

object, so that the grain removes from the

panicle. This traditional method results high

losses and is ineffective, because it will

bounce the grain everywhere. The manual

system of threshing rice in Nigeria leads to

low quality of paddy rice and grain loss.

1.3.2 Manually Operated Pedal

Thresher

Several researchers have worked on

manually operated thresher, called pedal

thresher. Amare et al. (2015) revealed major

parts of the pedal thresher. The pedal thresher

consists of an open rotating drum with wire

loops. The drum strips the grains from the

panicles when fed by hand. The Pedal Rice

thresher was simple to operate with leg

muscle, doesn’t consume fuel and it is used

for threshing paddy rice easily. It can also be

operated by women and can be used in hilly

or terraced areas because of its portability


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(Khan and Salin, 2005). Amare et al. (2015)

stated some of the major specification of a

manually operated pedal thresher developed

- Power: human labor (chain drive

mechanism). Labor requirement: 2 persons.

Weight: 35 Kg-40 Kg. Dimension (L*W*H):

62*65*63 cm. Capacity: 110-120 Kg/hr.

Threshing drum: peg type. Peg diameter:

46cm. Peg length: 44.5cm. Construction

material: steel metal.

1.3.3 Mechanized Thresher

This machine is known as “through-flow”

thresher, because stalks and ears pass through

the machine. The rice threshing machine

comprises three main units; the feeder

chamber, the threshing chamber and the

separation chamber. It consists of a threshing

device with pegs, teeth or loops, and (in more

complex models) a cleaning-winnowing

mechanism based upon shakers, sieves and

centrifugal fan. Major components of a

mechanized rice threshing machine include

prime mover (combustion engine), blower,

threshing basket, sieving and threshing units.

These components are normally assembled

on a structural frame made from a 50mm mild

steel angular bar. The prime mover

(combustion engine) drives the primary shaft

of the threshing unit which in turn drives the

feeder shaft unit that turns the blower shaft

(Ani et al., 2020). Different components of

threshers include:

a. The Feeder Olugboji (2004) stated that the feeder unit

comprises of the hopper, whose aperture lays

vertical at the base. The hopper has only one

of its sides in a slant. Opposite the start side

is a vertical side, which has the aperture of

the hopper at its bottom. Within the aperture

by two feed rollers, the free one is on top of

the driven one. The free one is constantly

under a vertical force, which tends to

compress it downwards upon the lower

driven one (Maynard, 2013; Xia et al., 2018

and Ani et al., 2020). At the two free ends of

the free roller’s axle are loads which provide

the downward force mentioned earlier. The

loads are varied as required. A pulley is

attached to the shaft of the driven roller. The

input for the shaft is taken from the shaft of

the thresh comb via a vee-belt. According to

the researchers the internal of some feeder

chambers comprises a conveyor like

attachment to give direction to the rice stalk

while being threshed on the rotation of the

shaft.

b. The Threshing Unit Olugboji (2004); (Amare et al., 2015); Ajis

and Lanya (2018) and Ani et al. (2020)

asserted that the threshing unit comprises of

the thresh comb. This is made up of a shaft

upon which small rods (tongs) are welded to

it in a line at intervals. There are two of such

lines-each welded to opposite sides of the

shaft. Each of the tongs is carved to forming

an arc of small curvature. The shaft rests on

ball bearings at each end. Attached to one of

the ends of the shaft is a pulley for drive. The

pulley/shaft rotates in the direction of carve

of the tongs. Just a distance beneath the

thresh comb is a sloppy tray which slopes

downwards into a trench. The trench is also

sloppy in the direction perpendicular it the

direction of slop of the tray.

In another design by Ani et al. (2020), the

motorized rice equipment is powered by

combustion (diesel) engine as prime mover

of power 4.41kw and at a speed of 2600r/min.

The dimension of the rice thresher reads 1020

× 650 × 800 mm. the threshing unit consists

of a rotating cylinder called the threshing

drum with a diameter of 320mm and 960mm

by length. It has flange on which a flat bar of

960mm x 50mm x 5mm is welded on it. On

top of it is a threshing pin of diameter 12mm

at 75mm length. The configuration of the

threshing pin is in spiral form to also act like

a conveyor, directing the straw through the

outlet. Below the threshing drum is the

threshing basket of 5mm spacing through

which threshed paddy is collected.

Ani et al. (2020) further revealed that the

threshing chamber comprises of the threshing

pin which is made up of a shaft running

through a flywheel with a flat bar welded


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across each flywheel from one end to another,

which small rods are bolted on in a line at

intervals in spiral direction. Each of the small

rods is bent at the tip. The shaft is held by a

bearing at each end with a pulley attached to

the ends of the shaft for drive. The

pulley/shaft rotates in the direction of carve

of the threshing pin. Under the tip of the

threshing pin is a threshing basket with an

external slant called a sloppy tray that slopes

downwards into a sieve. The sieve is attached

with a cam to the main frame of the thresher

so as to enable it to swing with vibrations for

final collection of threshed rice grain.

c. Separation Unit Olugboji (2004) stated that the separation

unit is located just under the hopper and

opposite the slope of the tray. It is responsible

for separating the grain from the chaff. It

consists of the blower chamber located under

the threshing barrel at a point opposite the

sloppy tray. It is a suction blower which takes

the stalks or empty pods off from the system

by sucking as separation is by gravity since

the massy rice grains weighs more than the

stalk (Ajis and Lanya, 2018).

Bariya et al., (2019) and Ani et al. (2020) in

their work explained that the blower consists

of am impeller shaft, volute casing and hose.

The impeller is an open type fabricated from

a 2mm thick mild steel plate with six vanes

(each made from 1.5mm slitted plate) which

created suction in the blower. The impeller

shaft is a 400mm long mild steel rod with a

diameter of 30mm. The casing which houses

the impeller was formed using a 1.5mm thick,

20mm width squared formed mild steel plate

with an ‘eye’ diameter of 18mm for

atmospheric air intake and air vent width of

800mm through which a 2mm thick, 35mm

long curved and 20mm diameter metal hose

that connects the blower to the metal valve

below the slating trays was fixed.

2. CONCLUSION FROM SOME OF

THE RESEARCHERS ON RICE

THRESHERS

Olugboji (2004) concluded that the design

and fabrication of a rice threshing machine

has been successfully carried out by his work.

The machine is capable of threshing,

separation of stalk from grains and reduction

in number of broken grains, thereby, giving a

better method of threshing than the

traditional methods. All the materials used

were locally sourced.

On the other hand, Azouma et al. (2009) in

their study on the Design of throw-in type

rice thresher for small scale farmers,

concluded an impressive result but

recommended that in future design the side

edge cover of the sieve/grain pan should be

raised to avoid falling of grain and chaff into

the grain outlet. They further stated that more

tests should be conducted to ascertain why

there was a decrease in threshing capacity as

speed went up; and finally, the screen spring

should be doubled to avoid future breakages.

Ahmad et al. (2013) modified the designs of

beater and beater drum of conventional wheat

thresher. As a result, grain damage was

reduced four times and grain-cleaning

efficiency was improved from 97.44% to

98.18%. In order to change the contact

condition, Mesquita et al. (2000) installed

nylon cords on the rotating shafts. The result

indicates that threshing efficiency increased

from 94.8% to 99%, which was substantially

higher than conventional threshing

components. At the same time, seeds broken

rate ranges from 0.6% to 0.3%, which was

also considerably lower than the

conventional level (8.4%).

In another development, Amare et al. (2015)

in their study on pedal rice thresher reiterated

that the promotion and utilization of the

modified thresher reduces the threshing

labour demand of an average farmer by

77.08%. Besides, farmers appreciated for

home consumption and the avoidance of hay

breakage used for thatching. However, they


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considered it as a low priority where weeding

and planting are recently considered as major

bottlenecks. Hence, inappropriate

postharvest handling including threshing

results in physical loss of produce and the

produce becomes low quality resulting in low

market competitiveness and low income for

farmers.

Ajis and Lanya (2018) reiterated that the

operation of hammer thresher is easier

compared to conventional thresher operation.

Equipment capacity of 132.1 to 168.8 kg of

rice per hour is quite feasible for small-scale

paddy farmers. The motor drive was 1 Hp

(746 Watt). The effective rotation of this

equipment uses 465 rpm, with the straw

expenditure opening being 180 cm2.

Xia et al. (2018) opined that in order to

improve efficiency of the threshing process,

the threshing roller with large diameter and

low rotating speed, the nail-tooth threshing

mechanism and the concave plate screen with

large spacing are suitable for the thresher.

Furthermore, the optimal combination is

roller speed, 400 /min, feed quantity, 1.2 kg/s

and concave tolerance, 54 mm. whereas the

testing results showed that impurity content

and breaking rate of the developed nail-tooth

type thresher were respectively 1.09 % and

3.45%, achieved relatively ideal operation

effect.

Bariya et al. (2019) concluded that the design

and development of automatic rice threshing

machine, which is operated by conveyor belt

was successful. The machine gave

automation in rice threshing and it is operated

on gear motor at required speed, thus

reducing human effort, labour cost, time and

increased output. While Ani et al. (2020) in

his conclusion stated that the developed

mobile rice threshing machine eliminates

drudgery and tedium in the processing and

production of local rice as well as the

excessive loss of rice grains during

production. The machine equally reduced the

breakage of rice grains and enhanced the

production of adequate quality and quantity

of processed rice. Adoption of this machine

is recommended to facilitate mass production

of rice as well as its possible exportation.

Okusanya and Oladigbolu (2020) asserted

that there is a need to increase effort on local

rice production so as to bring down the price

of rice sold at escalated cost. To help make

equipment available to rice processors,

research was undertaken by designing and

fabricating a motorized rice thresher for

small and medium scale holder of rice farm

to improve on the activities of rice processing

in the industry. Materials were fed into the

threshing chamber made of peg teeth

cylindrical drum through an axial-flow feed

in mechanism to separate hulled rice from its

stalk through impact force. The machine uses

cyclone vacuum principle for cleaning

operation. To this effect, the machine

designed and constructed has design capacity

of 350kg/hr. and efficiencies of threshed rice

at single and double passes to be 85% and

97% respectively.

Bello et al. (2020) identified critical factors

influencing rice quality which include rice

physical appearance before and after

processing, its cooking qualities, and eating

qualities. Appearance has a direct influence

on the marketability and success of

commercial varieties. Cooking and eating

quality are determined by its easiness in

cooking, texture, springiness, stickiness, and

chewiness of cooked rice. It was stressed that

challenges faced in the processing sector

include; processing equipment constraints

such as the use of outdated milling

technology, poor product branding, coupled

with evident political interests on agriculture.

3. POOR ADAPTATION AND

UTILIZATION OF RICE THRESHERS

While the rice demand increases, the manual

threshing consequently becomes arduous

even with the already existing mechanized

system, the rough nature of Nigerian farm

terrain still poses a challenge to the harvested

rice. Bariya et al. (2019) asserted that several

problems have been found associated with


122

rice threshing machines. The need to do

different performance evaluation of rice

threshing machines with consideration of the

terrains of the farmland in these areas

becomes essential so as to address the

challenges hampering the production of

adequate quality and quantity of processed

rice. Thresher reduces the drudgery

associated with the manual harvesting of

paddies with the winnower removing the

premature grain and leaves by the help of a

suction blower. These premature grains and

leaves are often lighter thus leaving aside the

massy grains that will thereafter be collected.

Appiah et al. (2011) reported that reducing

postharvest losses, among others, could help

in reducing rice imports with its accompanied

economic losses. In recent years, Nigeria

spent Billions of Naira annually on rice

importation to argument local demand. The

country’s self-sufficiency in rice production

stands at about 40 per cent, leaving a shortfall

of 60 percent. However, local farmers

involved in rice production in Nigeria still

use outmoded means of threshing. Thus,

using wood logs as implement to aid in the

threshing. Aside from being labour intensive,

the post-harvest losses are huge. Studies have

shown that threshing losses were higher

(6.14%) when threshing was done using the

“Bambam” box (a big locally made wooden

box) than when bag beating method (2.45%)

was used (KPMG, 2019 and Ani et al., 2020).

The issue of rice post-harvest management is

nationally recognized (Teshome and Dawit,

2011). Qualitative postharvest loss of rice

could reach as much as 50% of the production

(Fofana, 2010). The quantitative postharvest

loss is between 10% and 22% in sub-Saharan

Africa. Threshing losses account for 30% of

rice postharvest loss in Ghana (Appiah et al.,

2011). Reducing postharvest losses, among

others, could help in reducing rice imports

with its accompanied economic losses.

Ani et al. (2020) asserted that development of

the mobile rice threshing machine will

definitely make the processing of rice more

economical in terms of labour, time and cost

since drudgery will be reduced. Moreover,

the profit margin of rice investor will be

enhanced because excessive waste of un-

threshed rice which characterized this sector

will be totally phased out. This will also

provide employment for the populace and

increase the external trade potential of

Nigeria, as the prospect of mass production

of Nigerian local rice and their exportation

will be enhanced. Several researchers have

worked on the development and utilization of

rice threshing machines, but many farmers

are yet to adapt to the use of such equipment

in production. Thus, in spite of the beautiful

and favourable conclusion from most of the

researchers on rice processing machineries,

availability, adaptation and utilization of

these indigenous machineries have been very

poor. In general, there still exist poor research

into development, adaptation and utilization

of locally developed machines. Hence, wider

scale promotion of the technology of rice

processing is of paramount importance to

increase adoption and subsequently enlarge

households’ income, marketable yield and

hence increase national food availability and

accessibility (Amare et al., 2015).

Several reasons have been put forward for

inability of the country to carryout rice

production to meet the demand. Apart from

the general problems of agriculture and

agricultural mechanization in Nigeria

including, poor research, poor credit

facilities, land tenure problems, high cost and

unavailability of machinery, poor extension

services, poor attitude of individuals to

agriculture, misappropriation of funds meant

for agricultural sector, poor infrastructure

and many more. Paramount among the

factors responsible for poor adaptation, poor

utilization and low quality and quantity of

rice production in sub-Saharan Africa,

especially Nigeria are:

i. In as much as the locally produced rice in

the country is highly nutritious, it is

characterized by dirt, stones, short grains

and unpolished. This make the rice


123

unattractive, poorly priced and poorly

accepted by individuals.

ii. Critical factors responsible for low

quantity and quality of rice production

are, completed machines were not put out

for use by farmers due to lack of linkage

between stake holders.

iii. Another factor is over dependence on

imported costly rice processing

machineries over locally produced ones.

Imported rice processing machineries are

usually beyond the reach of farmers.

iv. Some developed threshers had

constraints as reported by their tests

results. Poor engineering research into

the design, production, testing, utilization

and maintenance of rice processing

machineries, mainly caused by poor

research and linkages between

engineering departments and faculties of

tertiary institutions and the institutions

themselves and industries and

government research institutions.

v. There is the issue of poor funding of the

educational sector. This has led to poor

funding of various researches in the

institutions.

vi. The sixth important factor is the problem

of poor extension services to teach the

farmers utilization and adaptation of

latest technology.

vii. Another important factor as reported by

Bello et al. (2020) is that although the

Nigerian government and institutional

agencies’ intervention in rice production

has significantly increased rice

production activities more than its efforts

towards ensuring quality assurance of the

products during processing. Enforcement

of rice quality standards has been left

dormant without strong controls for

implementation unlike the production

and ban on importation policies.

viii. Other identified challenges faced in the

processing sector include; processing

equipment constraints such as the use of

outdated milling technology, poor

product branding, coupled with evident

political interests on agriculture.

4. THE WAY FORWARD FOR

ADEQUATE DEVELOPMENT OF

RICE THRESHERS FOR USE BY

FARMERS

Development, adaptation and utilisation of

rice threshers for optimum production to

meet the demand of the people can be

achieved based on the solution to the issues

raised by different researchers as highlighted

in this article.

4.1 Appropriate Funding of Research

Funding of researches in our institutions is

one of the best solutions to the various

problems of agriculture in the country.

Governments and relevant organisations

should take funding of education very

seriously. Government provision of funds in

the yearly budget over the years have not

been encouraging, this has never met the

minimum provision according to the United

Nations. More funds should be budgeted on

education in other to enhance effective

research into different fields and most

especially in agriculture.

4.2 Sufficient Linkage Between the

Designers and the Industries

There should be sufficient linkage between

institutions engage in the designing of

agricultural machineries and relevant

industries to enable prompt production of

machines for the market for use by farmers

after production of prototype. In a situation

whereby most machineries are abandoned

after successful design and testing in the

institutions does not suffice as this fails to

address the production of agricultural

machineries especially, those in the rice value

chain.

4.3 Subsidising the Production of Rice

Threshers by Government Provision of subsidies on agricultural inputs

especially those in the rice value chain in

other to cushion the high cost of production.

This will generally encourage farmers to put

more effort in the production of agricultural

produce (rice).


124

4.4 Provision of funds in form of grants

and soft loans for those in Rice Value

Chain

Funds in form of grants and soft loans should

be provided by the relevant authorities to

researchers and those in the rice value chain

to encourage them into extensive work in the

production of rice.

4.5 Intensification of Extension

Services on Rice Value Chain

Extension services should be intensified on

all areas of the rice value chain to enlighten

the farmers on the nitty-gritty in rice

production. This will enlighten farmers on

the patronage of local rice threshers.

4.6 Need for Enforcement of Rice

Quality Standard

Standard should be maintained in rice

production. There dire need for enforcement

of rice quality standard to ensure that there is

quality control in the process. This will

enhance the quality of rice production in the

country to meet up with world standard. Once

the quality of local rice is equal to or more

than the foreign type, the issue of

overdependence on imported rice will be a

thing of the past.

5. GENERAL DEVELOPMENT AND

UTILIZATION OF RICE

THRESHING MACHINE

5.1 Machine Design Concept

Effective engineering design for application

in Rice threshing like any other engineering

design must follow the rules of design

concept. The Engineer must recognize the

need for such equipment before moving to

problem definition and design synthesis.

There is a great need for analysis of forces,

material selection and design of component

for the machine. The final stages are the

modification, detailed drawing, production

and testing of the equipment. Many

Researchers have worked tremendously on

the development of rice threshing machines.

Notable among others are Olugboji (2004);

Azouma, et al. (2009); Appiah et al. (2011);

(Ajavi et al. (2014); Amare et al. (2015); Ajis

and Lanya (2018); Xia et al. (2018); Bariya

et al. (2019) and Ani et al. (2020). The above

authors followed the general design steps to

achieve their design concepts.

5.2 Machine Components Design for

Rice Thresher

The following are the design concepts and

considerations for any typical rice thresher

5.2.1 Design Concepts and

Considerations

i. Threshing machine is normally

designed to separate the rice

grains from the stalks in a

manner to minimize absolutely

their breakage and enhance the

production of adequate quality

and quantity of processed rice.

ii. The effective moving system that

will suit Nigerian farm terrain

should be considered as well as

the air separating unit to separate

the rice grains from the stalks.

5.3 Steps in Rice Thresher Development

The following vital steps are essential in the

development of rice threshers are highlighted

for easy reference:

First, it is important to determine different

relationships using relevant formulae as done

by Olugboji (2004); Ajis and Lanya (2018);

Bariya et al. (2019) and Ani et al. (2020).

Such relationships are listed thus: (1) torque

required to comb off grains from the stalk, (2)

determination of power required to thresh off

grains from stalk, (3) determination of feed

roller speed, (4) shaft subjected to twisting

moment only, bending moment only,

combine twisting and bending moments

based on maximum shear stress theory (5)

determination of the shaft diameter (6) linear

speed and centrifugal force of hammer

including its weight and angle of position.

Others steps include (7) determination of V

belt length, tension and contact angle (8)

determination of drum (flange) diameter, (9)

Blower speed, (10) selection of drive


125

pulleys and its velocity ratio, (11) selection of

prime mover or motors of different power

ranges according to Ani et al. (2020); Bariya

et al. (2019); Ajis and Lanya (2018); Xia et

al. (2018); Olugboji (2004).

Next consideration is (12) hopper design and

capacity and maximum discharge rate and

concave screens as reported by Zhifeng et al.,

(2017) and Zhongkai et al. (2017) and finally

(13) designing the main frame of the machine

putting into consideration the stability,

rigidity, strength of vibration, and other

properties using mild steel – angular bar,

rectangular/square bar, solid or flat bar

depending on the structure of the machine.

5.4 Fabrication, Testing, presentation

and Utilization of Machine

Fabrication, testing, presentation and

appropriate utilization of the designed

machine are some of the most important

aspects of engineering development. An

excellent design that is not produced, tested,

presented and well utilized normally ends up

on the shelf. During fabrication, measures

must be taken in ensuring that this is done

according to specification and the right

materials are used. This will ensure

standardization, accurate testing and proper

utilization. Prototype building should be

made taking into cognisance of all

adjustments made during testing prior to

industrial production for appropriate

utilization (Odey and Manuwa (2016); Ajis

and Lanya (2018); Ovat and Odey (2019)].

5.4.1 Thresher efficiency and

Throughput

This is the ratio of mass collected at the outlet

to the mass inputted into the thresher as

presented by Sujanarko et.al. (2016) and Ani,

et al. (2020). It is found that peripheral

velocity of teeth, types of teeth and types of

drum all have prominent effects on threshing

efficiency and kernel surface quality (Xu et

al., 2013).

6. CONCLUSION

Review of the development, utilization and

adaptation of threshers for rice production in

Nigeria was carried out for the purpose of

increasing quantity and quality of rice to meet

the needs of the ever-growing hunger-

stricken population, for enhancement of

household income, marketable yield and

increase national food availability and

accessibility. Problems of rice threshing

machines and poor adaptation and utilization

were unravelled. Technical steps in the

design of rice threshing machines were

presented. In this research, it was revealed

that most of the researchers went through the

different steps in the design of their machines

and their tests results showed that their

machines had high efficiency. While a few of

the designs did not appropriately followed

the required steps.

It is recommended that the engineers,

relevant institutions and authorities should

collaborate in the development, evaluation,

utilization and adaptation of the rice

processing machineries for optimum quantity

and quality of produce through appropriate

funding of research, sufficient linkage

between the designers and the industries,

subsidising the production of rice threshers

by governments, provision of funds in form

of grants and soft loans for those in rice value

chain, intensification of extension services on

rice value chain and need for enforcement of

rice quality standard. Thus development,

adaptation and utilization of rice threshers

would reduce drudgery, increased income

and improved standard of living of the

people. It is also suggested that, relevant

authorities, private and public sectors should

intensify more efforts towards domestic rice

production to meet the demand of the

citizens.

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