Model Sistem Tertutup untuk Pengembangan Industri Penggilingan Padi Mandiri Energi.

A CLOSED MODEL OF PRODUCTION SYSTEM FOR
ENERGY SELF-SUFFICIENCY IN RICE MILL

MUHAMMAD NURDIANSYAH

DEPARTMENT OF AGROINDUSTRIAL TECHNOLOGY
FACULTY OF AGRICULTURAL TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015

STATEMENT OF ORIGINALITY, INFORMATION SOURCE
AND COPYRIGHT TRANSFER
I declare that Skripsi entitled: “A Closed Model of Production System for
Energy Self-sufficiency in Rice Mill” is my own work assisted by supervisor and
I have never submitted it in any form to any collage. Source of information from
published or unpublished works are cited in the text and listed in the references
section. Hereby, I state that the copyright of this paper is transferred to Bogor
Agricultural University.

Bogor, August 2015

Muhammad Nurdiansyah
NIM F34110022

ABSTRACT
MUHAMMAD NURDIANSYAH. A Closed Model of Production System for
Energy Self-sufficiency in Rice Mill. Supervised by: TAJUDDIN BANTACUT.
Rice mills consumed a lot of energy. The fossil fuel has been the main
source of energy which availability is declining, and in addition the use of it
caused negative impact on the environment. A more sustainable energy resource,
such as biomass should be considered to replace fossil energy. This research was
aimed to develop a model of a self-sufficiency rice mill by converting by-products
into energy. The model is based on principle of mass balance by assuming linear
equation in each compartment. The simplest model assumed the rice mill as a
single compartment, the level II model assumed main process as compartment,
and the complex model used a more detailed step of processes as compartment.
The complex model was chosen to be the most suitable model to represent actual
process of rice mill. According to this model, head rice yield, rice husk ratio, and
bran ratio obtained is 0.572; 0.231, and 0.074 of dried paddy respectively. Energy
potential of by-product conversion is 18,827 MJ/day from processing 20 tons

paddy. This energy potential exceeded the need with surplus of 28.25%. This
research revealed that rice mills can be energy self-sufficient. Therefore, it is
possible to limit fossil fuel energy used in rice mill.
Keywords: rice mill, closed production system, self-sufficient energy industry
ABSTRAK
MUHAMMAD NURDIANSYAH. Model Sistem Tertutup untuk Pengembangan
Industri Penggilingan Padi Mandiri Energi. Dibimbing oleh: TAJUDDIN
BANTACUT.
Penggilingan padi menggunakan energi yang besar. Pemenuhan kebutuhan
energi ini masih dipenuhi oleh sumber energi fosil yang terbatas ketersediaannya
dan berdampak negatif terhadap lingkungan. Sumber energi alternatif yang
berkelanjutan dibutuhkan untuk menggantikan sumber energi fosil, salah satunya
adalah biomassa. Penelitian ini bertujuan untuk mengembangkan model
penggilingan padi mandiri energi memanfaatkan hasil samping produksinya
dalam sebuah sistem yang tertutup. Model dibuat berdasarkan prinsip
kesetimbangan massa dengan asumsi persamaan linier pada setiap
kompartemennya. Model paling sederhana diasumsikan terdiri dari satu
kompartemen, model level II menggunakan proses utama penggilingan padi
sebagai kompartemen dan model paling kompleks menggunakan proses
penggilingan padi yang lebih detail sebagai kompartemen. Model paling

kompleks dipilih sebagai model yang paling sesuai untuk menggambarkan proses
penggilingan padi. Berdasarkan model ini, didapatkan rendemen beras kepala,
sekam dan dedak yang didapatkan adalah 0.572, 0.231 dan 0.074 terhadap gabah
kering giling secara berurutan. Potensi konversi energi dari model yang
dikembangkan adalah 18 827 MJ/hari untuk kapasitas pabrik 20 ton gabah kering
panen per hari. Potensi energi tersebut memberikan surplus energi sebesar 28.25%
terhadap kebutuhan energi produksi. Penelitian ini mengungkapkan bahwa

industri penggilingan padi dapat mandiri energi dengan memanfaatkan hasil
sampingnya sehingga dimungkinkan pembatasan penggunaan energi fosil pada
penggilingan padi.
Kata kunci: penggilingan padi, sistem produksi tertutup, industri mandiri energi

A CLOSED MODEL OF PRODUCTION SYSTEM FOR
ENERGY SELF-SUFFICIENCY IN RICE MILL

MUHAMMAD NURDIANSYAH

Skripsi
As partial fulfillment of the requirements for the degree of

Bachelor (Honour) of Agricultural Technology
at
Department of Agroindustrial Technology

DEPARTMENT OF AGROINDUSTRIAL TECHNOLOGY
FACULTY OF AGRICULTURAL TECHNOLOGY
BOGOR AGRICULTURAL UNIVERSITY
BOGOR
2015

Skripsi title : A Closed Model of Production System for Energy Self-sufficiency
in Rice Mill
Name
: Muhammad Nurdiansyah
NIM
: F34110022

Approved by

Dr Ir Tajuddin Bantacut MSc

Supervisor

Acknowledged by

Prof Dr Ir Nastiti Siswi Indrasti
Head of Department of Agroindustrial Technology

Date of graduation:

PREFACE
Praise and thanks to Allah SWT the Almighty for mercies and blessings so
the author could finish this skripsi on time. There is no power of the author to
complete this skripsi without His help and mercies. Sholawat and salam may still
delivered to Prophet Muhammad SAW because of his guidance so that we can
know the true way of life that is Islam Religion.
Author thank to:
1.
Dr Tajuddin Bantacut as the author’s supervisor for his guidance, support
and motivation until this Skripsi finished.
2.

Parents and author’s big family for their pray and support.
3.
All of lecturers and staffs of Agroindustrial Technology Department which
provide excellent facilities and services.
4.
Author’s partner: Mohammad Ryan Pratama, Andreas Zuriel and Aryosan
Tetuko Haryono who have stood together to carry out this research.
5.
Author also thanks to Yunita Siti Mardhiyyah, Anisa Nurul Rosnadia,
Yudhistira Chandra Bayu and Indra Kurniawati as correctors of this skripsi.
6.
Author’s classmates of Agroindustrial Technology 48 generation especially
for P1 class who have stayed together in happiness and sorrow.
7.
Family of Al Khidmah Kampus IPB: Bagus Sukma Agung, Muhammad
Iqbal, Dewi Anggraeni, Afif Bahruddin and close friends: Mirra Chan, Fajar
Syahreza, Aldilah Fazy, M. Nizam Mustaqim, Diki Dwi Aji, Ahmad
Muhaimin and comrade AKSEL 25 who always motivate.
8.
Big Family of Himasurya Plus IPB, KMNU IPB, IMAJATIM IPB which

always stay with the author when he was bored.
9.
All of author’s friend include alma mater or not and all parties that support
completion of this skripsi.
The Author hopes this skripsi can contribute significantly to the
development of science and technology. Author expects critics and suggestion for
further development of better agriculture.

Bogor, June 2015

Muhammad Nurdiansyah

TABLE OF CONTENTS
LIST OF FIGURES

xii

LIST OF TABLES

xii

LIST OF APPENDICES

xii

INTRODUCTION

1

Background

1

Research Objective

2

Scopes of the Research

2

METHOD

2

Data Collection

2

System Boundary

3

Model Description

3

Mass Balance

3

Energy Content of Rice Production By-product

4

Process Flow of Self-sufficiency on Rice Mill

4

MASS BALANCE MODEL OF RICE MILL

5

Mass Balance Model Level 1

5

Mass Balance Model Level 2

5

Mass Balance Model Level 3

8

RESULT AND DISCUSSION

13

Mass Balance Model

13

Energy Self-sufficiency in Rice Mills

16

Closed System Production of Rice Mill

18

CONCLUSION AND RECOMMENDATION

19

Conclusion

19

Recommendation

19

REFERENCES

20

BIOGRAPHY

30

LIST OF FIGURES
1
2
3
4
5
6

Mass Balance Model Level 1 (I = P + W)
Mass Balance Model Level 2
Mass Balance Model Level 3
Result of Mass Balance Model Level 3 operation
Schematic diagram of fluidized bed drying
Self-sufficient energy closed production system model

5
6
9
15
16
18

LIST OF TABLES
1 Supporting data for energy potency calculation
2 Notes of Mass Balance Model Level 2
3 Efficiency values of Mass Balance Model Level 2
4 Description of symbols of Mass Balance Model Level 3
5 Efficiency values of Mass Balance Model Level 3
6 Comparison of models and IRRI standards by dried paddy
7 Comparison of Model level 3 with actual data by dried paddy
8 Rice husk potency for energy generation

4
6
8
9
13
14
14
17

LIST OF APPENDICES
1 Input value and inverse matrix operation of Model Level 2
2 Multiplier value and result of matrix operation of Model Level 2
3 Input value and inverse matrix operation of Model Level 3
4 Multiplier value and result of matrix operation of Model Level 3
5 Completed information of energy generation potency of rice mill
6 Completed closed system production model

24
25
26
27
28
29

1
INTRODUCTION
Background
Rice is a staple food for most people in the world especially for Asian
people, whereas 90% of the world’s rice is grown and consumed (Adjao and
Staatz 2014; Singha 2013; Suh 2014). Indonesia is one of the big five riceproducing countries in the world. Badan Pusat Statistik (2015) states that
Indonesia produced about 70 million tons of paddies in 2014. About 90% was
consumed by domestic people (Lim et al. 2014). This makes rice milling industry
is vital for national food security.
Rice milling industry is one of the energy consuming industries. The
amount of consumption varies from 734–1194.2 MJ/ton paddy input (Basappaji
and Nagesha 2013; Goyal et al.2012; Kapur et al. 1995).The variation depends on
its capacity and complexity of technology process.
The energy needs will continue to increase as much as the rice demands.
The fulfillment of the energy needs is dominated by fossil energy resources. For
the country, the consumed energy is fulfilled by fossil fuel (48%), coal (19%),
natural gas (14%), LPG (5%), electricity (13%) and other resources (1%). The
industrial sector has the largest share of energy consumption, as much as 33% of
total national energy consumption with an average growth of 4.5% per year
(KESDM 2014). Meanwhile, stocks of oil, coal and natural gas are declining and
will be limited for near future. Rice mills will face serious substitute fossil fuel
resources. Sustainable alternative energy resources are needed to replace fossil
energy sources. Biomass is one of the potential alternative energy which can be
the right solution for that energy problem.
The application of biomass-based energy sources is safer to the environment
than the fossil energy since the content of sulfur and nitrogen is lower
(Chungsangunsit et al. 2004; Sarasuk and Boonrod 2011). According to the study
by Gadde et al. (2009), the application of biomass as an energy resource for rice
production can prevent greenhouse gas emission (GHG) in three countries; India,
Thailand and Philippines for 0.75%, 1.81% and 4.31% respectively based on the
national specific GHG. The developed countries also fulfill their energy needs (up
to 35%) using biomass energy resource (Basappaji and Nagesha 2013). Biomass
utilization as an alternative energy resource is a promising choice for the
sustainable rice mill.
Rice husk is a potential biomass energy resource produced from rice milling
industries since it has high calorific value of 13–15.4 MJ/kg of rice husk in 14%
moisture content (Ahiduzzaman and Islam 2009; Hiloidhari 2014). It is also
conveniently converted into energy (UNEP 2007). Rice milling process produces
rice husk as much as 20–22% of dried paddy weight (Buggenhout 2013; Lamberts
et al. 2007; Nugraha et al. 2007). The amount of rice husk will be a major
problem in rice-producing countries if it is not handled properly (Lim et al. 2012).
Several researches were conducted to analyze the potency of rice husk for
energy generation. Chungsangunsit et al. (2004) who assessed the electricity
production from rice husk in Thailand, state that rice mill had a potency to fulfill
its energy needs. Majhi et al. (2014) who studied utilization of rice husk for power
generation in India reveal that the utilization of rice husk could reduce energy cost.

2
Okehet al. (2014) who analyzed the potency of rice husk for alternative energy
resource in Nigeria, show that rice milling industry has a potency to fulfill its
energy needs by rice husk utilization. However, those research are not adequate to
estimate the independence of rice mill. Detailed modeling and estimation of how
far rice mill can be self-sufficient in energy fulfilling will be the scope of this
research.
Energy generation from rice husk may be utilized in a closed system,
without any energy input from outside of the system. Based on the environmental
engineering rules, closed system means a system which each input and output
flows are known (Davis and Cornwell 2013). This research refers to that rule.
Some useful methods used are mass balance modeling and rice husk potency
analysis. Developed closed system is expected to integrate rice production and
rice husk utilization as an energy resource to achieve self-sufficient energy rice
mill.
Research Objective
This research aims at developing a model of self-sufficient energy rice
production system. It can be achieved by the followings:
1. Developing rice production mass balance model.
2. Calculating energy needs of rice mill.
3. Calculating rice husk potency for energy generation.
4. Developing closed rice production system.
Scopes of the Research
Scopes of this research are rice production mass balance modeling and rice
husk potency analysis as the energy resource. The input of the mass balance
model is paddy and the outputs are head rice and broken rice. The value of input
flow is 20 tons paddy/day. This value is following the observed rice mill capacity.
The compared parameters of the models are head rice yield, rice husk ratio, and
rice bran ratio.
The energy produced from rice husk utilization is compared to the rice mill energy
consumption of rice mill based on the literature. This comparison determines the
rice mill energy independence. If the energy generated is greater than energy need,
the rice mill can potentially be independent for its energy. However, if the energy
generated is smaller, the system is not independent for its energy.

METHOD
Data Collection
This research used primary data and secondary data. Primary data (factual
mass balance of Rice Mill) is collected from direct observation on a rice mill in
Cianjur, while the secondary data (mass flow of production, energy requirement

3
and by-product generation) from research reports, journals, books, thesis and other
scientific articles. The field research was conducted in Cianjur Rice Mill (West
Java) and the desk work in Department of Agroindustrial Technology, Faculty of
Agricultural Technology, Bogor Agricultural University (February–April 2015).
System Boundary
Rice production is a complex system which involves many factors which are
connected to each other. Those are material, energy requirement and by-product.
A comprehensive approach is used to minimize energy usage, optimize production
and utilize by-product. Therefore, a system approach is used to analyze the flow
of mass, energy needs and energy potency from the by-product.
In general, rice production is divided into five compartments (process):
drying, dehusking, whitening, polishing and grading. The material input is 20 tons
paddy per day (based on the field observation). The main output is head rice and
the secondary outputs (by-products) are broken rice, rice husk and rice bran.
Broken rice is output of compartment 5 (grading), rice husk from compartment 2
(dehusking) and rice bran from compartment 3 and 4 (whitening and polishing).
Model Description
The model was developed based on mass balance of process flow and
compartments to describe the real situation of rice production. The development
of model notes to obtain the appropriate model which is able to represent real rice
production. It was also to confirm the models consistency. The input is the
independent variable while output and by-product are dependent variables.
Modeling also used the ratio value (efficiency) of the variables based on the linear
equation principal as the supporting data to develop the model. The calculation of
the variables passed through matrix operation using Microsoft Excel.
The basis of mass balance modeling was white rice production at 20 tons of
paddy per day capacity. The results of the model calculation were then compared
with the international standard of rice production from International Rice
Research Institute (IRRI) and the factual data of white rice production. It was used
to confirm and validate the accuracy of the model.
The model was used to identify and calculate the amount of by-products that
potential for energy source to meet the energy needs of rice mill. The model
which had a high degree of consistency and appropriate with real rice production
was used to the next analysis (energy potency analysis) to develop a self-sufficient
energy rice mill.
Mass Balance
Mass balance is mathematical representation of input and output mass flows
in a system. It can be applied for the modeling of production, transportation and
fate of pollutants in the environment. It shows every flow in the system and also
every accounted component in the closed system (Davis and Cornwell 2013).

4
The first step is identifying the compartments of the rice production process.
Then set mass balance to link the variables as input (paddy) and output (head rice
and by-products) for all compartments. By-product is assumed to be recyclable. In
identifying, the efficiency equation (the ratio of variables) used secondary data
from literature study. Then, the mass balance can be determined.
Mass balance model is a series of mass balances illustrating rice production
process. Matrix operation is used to calculate the value of variables. The input
values for matrix operation are variables of mass balance and efficiency value of
each compartment. It will be developed into three levels of mass balance model
based on complexity of production process. This development aims at checking
the consistency of the models. Then, the most suitable model to describe the real
rice milling process will be chosen for the next analysis (energy analysis).
Energy Content of Rice Production By-product
The potential energy will be calculated by the equation: Potential energy
(MJ) = Mass (ton) x calorific value (MJ/ton). Mass of by product will be obtained
from model calculation whereas the calorific value will be obtained from the
literature (13–15.4 MJ/kg of rice husk). This research used lowest calorific value,
which was 13 MJ/kg of rice husk as a self-sufficient energy potency analysis.
Process Flow of Self-sufficiency on Rice Mill
The analysis of self-sufficient energy potency needs actual energy
consumption of rice mill for the comparison. Actual energy consumption of rice
mill is obtained from literature. The value is varied depends on applied technology
and capacity. Several studies stated that it was about 734 MJ/ton paddies.
(Basappaji and Nagesha 2013). Besides, it also needs some supporting data to
calculate the generated energy from rice husk. Table 1 summarizes the properties
of the calculation
Table 1 Supporting data for energy potency calculation
Supporting data
Value
Reference
Energy need of rice mill
504 (thermal) & Basappaji and Nagesha (2013)
(MJ/ton paddy)
230 (electrical)
Efficiency of hot air
30%
Basappaji and Nagesha (2013)
Efficiency of boiler
68%
Yadav and Singh (2011)
Steam/rice husk ratio
4.3
Yadav and Singh (2011)
Efficiency of generator
77%
Narvaez et al. (2013)
Finally, the comparison of energy potency and energy needs will show the
independence of rice mill. If the energy potency of by-product is greater than or
equal to the energy needs, then rice mill can potentially be self-sufficient in its
energy. However, if the energy potency is smaller than the energy needs, the rice

5
mill needs energy from the outside then the system is not independent in its
energy.

MASS BALANCE MODEL OF RICE MILL
Mass balance model of rice mill is developed into three levels based on
complexity of production process. The simplest model assumed the rice mill as a
single compartment, the level II model assumed the main process as a
compartment, and the complex model used a more detailed step of process as a
compartment.
Mass Balance Model Level 1
Mass Balance Model Level 1 is the simplest model by assuming all steps of
the process as single compartments. It explains total amount of input and output of
the system generally. Thus it only contains single efficiency value, which is head
rice yield (HRY). In general, rice milling in Indonesia produce HRY as much as
45% based on rough paddy, stated in Indonesia as “Gabah Kering Panen” or
“GKP” (Rachmat 2012).

Figure 1 Mass Balance Model Level 1 (I = P + W)
Notes: I = input, P = product, W = waste

Mass Balance Model Level 2
Mass Balance Model Level 2 is the development of the previous model. It
shows a more detailed explanation of rice production process than the previous
model. This model contains several compartments as an extension of the previous
model corresponding with general rice milling processes. Those are drying,
dehusking, whitening, polishing and grading. Drying is to decrease moisture
content of harvested paddy (De Datta 1981). Dehusking is rice husk removal with
a minimum damage (Araullo et al. 1976). Whitening is rice bran removal (Araullo
et al. 1976). Polishing is to remove existing fine rice bran (De Datta 1981).
Grading is to classify produced rice based on physical properties (Houston 1972).
Generally, the aim of rice milling is to remove husk, bran to produce polished rice
and then grade it to the classified rice.

6
There are 5 mass balance equations based on number of compartment. Thus,
the number of efficiency value is as much as the number of mass balance
equations (5 values). It consists of 1 independent variable (I1) and 10 dependent
variables (X1, X2, X3, X4, W1, W2, W3, W4, P1 and P2). The independent variable
is a consistent variable which has a given value (20 tons of paddy) while the
dependent variables have various value depended on efficiency values. Mass
Balance Model Level 1 is shown below.

Figure 2 Mass Balance Model level 2 (The symbols are described in Table 2)

I1

W1
W2
W3
W4

Table 2 Notes of Mass Balance Model Level 2
Input
Output
= paddy
P1 = head rice
P2 = broken rice
Waste
Internal flows
= vapor
X1 = dried paddy (milling)
= rice husk
X2 = brown rice
= rice bran
X3 = white rice
= rice bran
X4 = polished rice

Mass Balance Equations:
Compartment 1
Compartment 2
Compartment 3
Compartment 4
Compartment 5

: I1 – W1 – X1
: X1 – X2 – W2
: X2 – X3 – W3
: X3 – X4 – W4
: X4 – P1 – P2

= 0..................................................... (2.1)
= 0..................................................... (2.2)
= 0..................................................... (2.3)
= 0..................................................... (2.4)
= 0..................................................... (2.5)

7
Efficiency values:
Drying efficiency (a1)
a

dried paddy
paddy

I

( 6

Drying process is basically the transfer of heat by converting the water in grain to
a vapor and transferring it to the atmosphere (De Datta 1981). In tropical countries,
the moisture content of harvested paddy is about 25% (Jittanit et al. 2010). It
needs to be decreased to 14% (Rahmat 2012; Steffe et al. 1980). Based on the
mass balance equation (2.1), 12.8% of water from the paddy needs to be
evaporated to obtain 14% moisture content. Thus the efficiency value of drying
process (a1) is 87.2%.
Husking efficiency (a2)
a

brown rice
dried paddy

( 7

Husking is process of removing rice husk from harvested paddy with a minimum
of damage to the bran layer (Araullo et al. 1976; Lambrets et al. 2007). Rice husk
accounts for 20% of the weight of dried paddy (Chungsangunsit et al. 2004;
Nugraha et al. 2007). Thus the efficiency value of rice husk removal (a2) is 80%.
Whitening efficiency (a3)
a

white rice
brown rice

( 8

Whitening is a process to remove bran from brown rice (Araullo et al. 1976; De
Datta 1981). Rice bran produced as much as 10% by weight of dried paddy (Naito
et al. 2015; Rachmat 2012). Based on the mass balance equation (2.3), it is as
much as 12.5% of the weight of brown rice. Thus the efficiency value of brown
rice milling (a3) is 87.5%.
Polishing efficiency (a4)
a

polished rice

( 9

Polishing is a process to remove existing fine rice bran on the kernel to smooth its
surface using abrasive polisher (De Datta 1981). Polished rice produced is about
98% of the weight of white (Chung and Lee 2003; Prakash et al. 2013). Thus the
efficiency value of polishing (a4) is 98%.

8
Head rice grading efficiency (a5)
a

head rice

P

(

0

Rice milling also generates broken rice as much as 18–25% of the weight of
polished rice. So it must be separated to get better quality of rice (Dalen 2004;
Damardjati 1990). Based on the mass balance equation (2.5), broken rice is as
much as 21.5% of the weight of polished rice. Thus the efficiency value of
grading (a5) is 78.5%. Table 3 summarizes the efficiency values used in Mass
Balance Model Level 2.
Table 3 Efficiency values of Mass Balance Model Level 2
Efficiency Value
Reference
a1
0.872 Jittanit et al. (2010); Rahmat (2012); Steffe et al. (1980)
a2
0.8
Chungsangunsit et al. (2004); Nugraha et al. (2007)
a3
0.887
Naito et al. (2015); Rachmat (2012)
a4
0.98
Chung and Lee (2003); Prakash et al. (2013)
a5
0.785
Dalen (2004); Damarjati (1990)
Mass Balance Model Level 3
Mass Balance Model Level 3 is the development of the second model which
shows more detailed explanation from the previous. This model contains several
compartments as extension of the compartments of the second model related to
the complex rice production process. Drying is extended into paddy cleaning (precleaning) and drying. Pre-cleaning is removing the impurities from rice (De Datta
1981). Husking is extended into general destoning (stone removal), dehusking,
screen sorting, brown rice separating and thickness grading (immature grain
separation). Screen sorting and brown rice separating are to recycle the
uncompleted brown rice (Chung and Lee 2003). Whitening is extended into
brown rice destoning (secondary stone removal), whitening and rotary shifting
(broken rice separation). Polishing is extended into polishing and color sorting.
Grading is a single step so it is not extended (Chung and Lee 2013).
Mass Balance Model Level 3 has efficiency values as much as the number
of compartments (13 compartments). It consists of 1 independent variable (I1) and
26 dependent variables (X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, W1, W2,
W3, W4, W5, W6, W7, W8, W9, W10, W11, W12, P1 and P2). The independent
variable is a consistent variable which has a given value (20 tons of paddy)
whereas the dependent variables have various value depended on the efficiency
values. Mass Balance Model Level 3 is shown below.

9

Figure 3 Mass Balance Model Level 3 (The symbols are described in Table 4)

I1

W1
W2
W3
W4
W5
W6
W7
W8
W9
W10
W11
W12

Table 4 Description of symbols of Mass Balance Model Level 3
Input
Output
= paddy
P1 = head rice
P2 = broken rice
Waste
Internal flows
= leaves and stems
X1 = clean paddy
= vapor
X2 = dried paddy
= stone
X3 = clean dried paddy
= rice husk
X4 = brown rice
= unhusked grain
X5 = complete brown rice
= raw brown rice
X6 = complete brown rice
= unripe grain
X7 = ripe brown rice
= stone
X8 = brown rice
= rice bran
X9 = white rice
= broken rice
X10 = complete rice
= rice bran
X11 = polished rice
= colored rice
X12 = clean polished rice

Mass balance equations:
Compartment 1
Compartment 2
Compartment 3
Compartment 4
Compartment 5
Compartment 6
Compartment 7
Compartment 8
Compartment 9
Compartment 10

: I1 – W1 – X1
: X1 – X2 – W2
: X2 – X3 – W3
: X3 – X4 – W4+ W5 +W6
: X4 – X5 – W5
: X5 – X6 – W6
: X6 – X7 – W7
: X7 – X8 – W8
: X8 – X9 – W9
: X9 – X10 – W10

= 0............................................(3.1)
= 0............................................(3.2)
= 0............................................(3.3)
= 0............................................(3.4)
= 0............................................(3.5)
= 0............................................(3.6)
= 0............................................(3.7)
= 0............................................(3.8)
= 0............................................(3.9)
= 0..........................................(3.10)

10
Compartment 11 : X10 – X11 – W11
Compartment 12 : X11 – X12 – W12
Compartment 13 : X12 – P1 – P2

= 0..........................................(3.11)
= 0..........................................(3.12)
= 0..........................................(3.13)

Efficiency values:
Precleaning efficiency (a1)
a

clean paddy
rough paddy

I

(

4

Pre-cleaning process separates impurities such as weed, seed, leaves and stalks
(De Datta 1981). It applies oscillating sieve mechanism. Impurities generated as
much as 0.25% by weight of rough paddy (Chung and Lee 2003; Rachmat 2012).
Thus efficiency value of precleaning (a1) is 99.75%.
Drying efficiency (a2)
a

dried paddy
clean paddy

(

5

Drying process is basically the transfer of heat by converting the water in grain to
a vapor and transferring it to the atmosphere (De Datta 1981). In tropical countries,
the moisture content of harvested paddy is about 25% (Jittanit et al. 2010). It
needs to be decreased to 14% (Rahmat 2012; Steffe et al. 1980). Based on the
mass balance equation (2.1), 12.8% of water from the paddy needs to be
evaporated to obtain 14% moisture content. Thus the efficiency value of drying
process (a1) is 87.2%.
Destoning efficiency (a3)
a

clean dried paddy
dried paddy

(

6

Destoning process removes stone from paddy (Chung and Lee 2003). This process
takes advantage of gravitation force to separates stone from paddy. It generates
various value depends on harvesting process (IRRI 2015). In estimation, stone
generated about 0.25% by weight of clean dried paddy (Chung and Lee 2003).
Thus efficiency value of destoning (a3) is 99.75%.
Dehusking efficiency (a4)
a

brown rice
clean dried paddy

(

7

Dehusking process applies frictional force between two rollers with different
speed and direction to crack rice husk (Araullo et al. 1976). This process
generates husk as much as 20% by weight of clean dried paddy (Lambrets et al.

11
2007; Dhankhar et al. 2014). Thus the efficiency value of rice husk removal (a4) is
80%.
Screen sorting efficiency (a5)
a

complete brown rice
brown rice

(

8

Screen sorting is a recycling process to bring back the uncompleted brown rice to
dehusking process using compartment separator (Chung and Lee 2003; Lambrets
et al. 2007). It is assumed the value of screen sorting (a5) is 98%.
Brown rice separating efficiency (a6)
a

complete brown rice
complete brown rice

(

9

Brown rice separating is a secondary recycle of uncompleted brown rice based on
paddy size by using a tray separator. It also applies oscillating mechanism so that
the complete brown rice can be separated (Chung and Lee 2003; Lambrets et al.
2007). It is assumed that the value of brown rice separating (a6) is 98%.
Thickness grading efficiency (a7)
a

mature brown rice
complete brown rice

(

0

Thickness grading is to separate unripe grain based on the thickness (De Datta
1981; Chung and Lee 2003). It has various value based on the harvesting time
(IRRI 2015). This process separates unripe grain as much as 0.455% of the weight
of dried paddy (Chung and Lee 2003). It is equivalent to 0.782% of the weight of
complete brown rice 2. Thus, the efficiency value of thickness grading (a7) is
99.218%.
Brown rice destoning efficiency (a8)
a

clean brown rice
mature brown rice

(

Stone separation takes an advantage of gravitation force to separate stone from
paddy as well as previous destoning process (Chung and Lee 2003). It will be a
secondary stone removal. The generated stone is as much as 0.13% of the weight
of paddy (Chung and Lee 2003). It is equivalent to 0.023% of the weight of
mature brown rice. Thus, the efficiency value of brown rice destoning (a8) is
99.977%.

12
Whitening efficiency (a9)
a

white rice
clean

(

Whitening is to remove rice bran from grain surface to obtain white rice (Araullo
et al. 1976; De Datta 1981). Rice bran generated is as much as 4.58% by weight
of paddy (Gurjar and Sengupta 2015; Hansen et al. 2012). It is equivalent to
7.95% by weight of clean brown rice. Thus the efficiency value of whitening (a9)
is 92.05%.
Rotary shifting efficiency (a10)
a

complete white rice
white rice

(

Rotary shifting process is to separate complete white rice with broken rice (De
Datta 1981). Broken rice is uncompleted grain which has less than 50% whole
kernel length. (Rachmat 2012). The produced broken rice is as much as 2.68% of
the weight of paddy (Arora et al. 2007; Chung and Lee 2003). It is equivalent to
5.054% of the weight of white rice. Thus, the efficiency value of rotary shifting
(a10) is 94.946%.
Polishing efficiency (a11)
a

polished rice
complete white rice

(

4

Polishing is removal of existing fine rice bran on the kernel to smooth its surface
(De Datta 1981). This process apply abrasive polisher. Polished rice produced is
about 98% by weight of white (Chung and Lee 2003; Prakash et al. 2013). Thus
the efficiency value of polishing (a11) is 98%.
Color sorting (a12)
a

clean polished rice
polished rice

(

5

Color sorting separates the colored rice from the polished rice by using color
identifier (Chung and Lee 2003). The produced colored rice is about 1.2% of the
weight of paddy (Chung and Lee 2003). It is equivalent to 2.438% of the weight
of the polished rice. Thus, the efficiency value of color sorting (a12) is 97.562%.
Length grading (a13)
a

head rice
clean polished rice

P

(

6

13
Length grading is a removal of broken rice from clean polished rice to produce
head rice based on kernel length (Houston 1972). Head rice has 75%–80% of
whole kernel length. Head rice produced about 90% by weight of clean polished
rice (Cnossen et al. 2003; Damarjati 1990; USDA 2005). Thus the efficiency
value of length grading (a13) is 90%. Table 5 summarizes the efficiency values
used in Mass Balance Model Level 3.
Table 5 Efficiency values of Mass Balance Model Level 3
Efficiency. Value
Reference
a1
0.997
Chung and Lee (2003); Rachmat (2012)
a2
0.871
Jittanit et al. (2010); Nugraha et al. (2007)
a3
0.997
Chung and Lee (2003)
a4
0.8
Lambrets et al. (2007); Dhankhar et al. (2014)
a5
0.98
Chung and Lee (2003); Lambrets et al.(2007)
a6
0.98
Chung and Lee (2003); Lambrets et al. (2007)
a7
0.992
Chung and Lee (2003)
a8
0.999
Chung and Lee (2003)
a9
0.921
Gurjar and Sengupta (2015); Hansen et al. (2012)
a10
0.949
Arora et al.(2007); Chung and Lee (2003)
a11
0.98
Chung and Lee (2003); Prakash et al. (2013)
a12
0.976
Chung and Lee (2003)
a13
0.90
Cnossen et al. (2003); Damarjati (1990); USDA (2005)

RESULT AND DISCUSSION
Mass Balance Model
Head rice yield of Model Level 1 is lower than other models (Table 6). This
model is also not appropriate to illustrate the actual condition of rice mill. The
produced waste is expressed in aggregate (not clearly identified). It will cause
difficulties in energy potency analysis although the HRY is identified. Meanwhile,
the consistency analysis needs a value from this model as a comparison.
Mass Balance Model Level 2 is larger than the level 1 because it is an
extension of compartments of the previous model (Table 6). Meanwhile, this
model is not capable to identify impurities of rice production. The development of
this model is needed to identify all impurities and also to increase the HRY if
possible. But the first and second models are still needed to determine the
consistency of the models.
Mass Balance Model Level 3 produced greater HRY than the second model
because the flow of recycles (W5 andW6) brings back unhusked grain to the
husking process. Thus, it causes the increase of head rice yield (Chung and Lee
2003; IRRI 2013) while the previous models did not apply them. This model also
revealed impurities such as weed seed, leaves, stalks and stones. Stone and straw
were identified as much as 0.002 and 0.003 of the weight of paddy. So this model

14
is clear enough to illustrate actual situation of the rice mill. Mass Balance Model 3
is shown in Figure 4.
Table 6 Comparison of models and IRRI standards by dried paddy
Parameter
Model level 1 Model level 2 Model level 3 IRRI (2013)
Head rice yield 0.516
0.539
0.572
0.5–0.6
Rice husk ratio 0.2
0.231
0.2–0.23
Rice bran ratio
0.114
0.074
0.08–0.1
Recycle process also lead to increase of rice husk ratio (0.231 of the weight
of dried paddy). This is not corresponding with IRRI standards (0.2–0.23).
Recycle process brings back the unprocessed brown rice to the husking process
then the input of husking process increased. This improvement causes higher
number of the rice husk production. Thus, the recycle process is not only able to
improve HRY but also cause increasing of rice husk produced.
Next, this model is compared to the actual data from factory to verify its
accuracy (Table 7). The difference of HRY from this calculation is 10.287%
according to the actual data. It is acceptable because it is not too different.
Table 7 Comparison of Model level 3 with actual data by dried paddy
Variables
Model Level 3
Actual data
Difference
Head rice yield
0.572
0.517
0.053
Rice husk ratio
0.231
0.229
0.002
Rice bran ratio
0.074
0.125
0.051
Broken rice ratio
0.063
0.063
0
The difference of rice bran ratio from Table 7 is caused by the difference of
applied technology between the model and the factory. The Model developed
recycle process (screen sorting and brown rice separating) while the factory did
not. These processes bring back the uncompleted brown rice to the dehusking
process, thus, the number of rice husk produced increased. The higher rice bran
ratio of the actual data is caused by addition of fine rice husk to mixture of rice
bran. It was the same case with model level 2.
Mass Balance Model Level 3 has not significant difference with other
models and actual data and also meets the IRRI standards. Although it meets the
IRRI standards in HRY parameter only, it has not significant difference with IRRI
standards. So this model is accepted to be the best model of all. Thus, the next
analysis (energy potency analysis) examines the result of Mass Balance Model
Level 3.
From this discussion, it is possible to increase head rice yield of the factory
by improving technology to run an optimal process. The increase can be achieved
up to 10% based on HRY of the actual data. Recycling process is necessary to be
applied to produce better quality of rice.

Figure 4 Result of Mass Balance Model Level 3 operation
(Notes of symbols in Table 4)

15

16
Energy Self-sufficiency in Rice Mills
Rice husk utilization for energy generation is to fulfill thermal and electrical
energy needs of rice mill. The thermal energy is used for the drying process while
the electrical energy for the milling process. Variation of the amount of energy
consumption is depending on the capacity and technology applied.
There are several methods to utilize rice husk for energy generation.
Generally, they are divided into two paths, thermochemistry and biochemistry.
Thermochemistry path consists of combustion, gasification and pyrolysis while
biochemistry path consists of fermentation and esterification (Soltani 2015).
Thermochemistry path tends to be chosen because it is easier to be applied. While
biochemistry paths are more difficult to be installed.
Direct combustion for electricity generation using steam power has been
applied using wood biomass. It is also applicable for straw and husk biomass
(Matsumura 2005). Fluidized bed combustion is proper technology for low
density biomass conversion into energy since it has good mass transfer and heat
transfer characteristics (Loha et al. 2013). But the high content of silica also
causes high ash residue (Bazargan et al. 2015). Rice husk is not properly applied
for the fermentation process because of the high content of lignin and silica (Pode
et al. 2015). Thus, the direct combustion is chosen to be analyzed.
Rice husk combustion is used to produce hot air to supply the drying energy
needs. Hot air production uses fluidized bed dryer (FBD) which has an efficiency
of 30% (Basappaji and Nagesha 2013). FBD is an effective method for drying the
high moisture grain. The main advantages are fast drying rate, moisture content
similarity and high drying capacity due to a complete mixing between drying air
and paddy (Aghbaslo et al. 2013; Atthajariyakul and Leephakpreeda 2006;
Golmohammadi et al. 2015).The schematic diagram of drying process through
FBD is shown below.

Figure 5 Schematic diagram of fluidized bed drying
Simplified from Atthajariyakul and Leephakpreeda 2006; Chungcharoen et al. 2015

The efficiency value of electricity production using steam turbine generator
is approximately 77%. The input material is steam at 120 °C. Steam production
uses boiler heated by fluidized bed furnace. Efficiency of steam production of the

17
boiler is 68% (Yadav and Singh 2011). The calculation of energy independency
trough rice husk utilization is shown in Table 8.
Table 8 Rice husk potency for energy generation
Parameter
Amount
Energy needs
Dying energy needs (MJ)
4,600
Milling energy needs (MJ)
10,080
Total energy needs (MJ)
14,680
Energy generation potency
Rice husk produced (ton)
4.020
Rice husk for hot air production (ton)
2.585
Rice husk left (ton)
1.436
Steam produced (ton)
4.198
Electricity produced (MJ)
18,827
Energy surplus (MJ)
4,147
According to Table 8, rice husk is combusted to operate the heater for hot
air production. Leftover rice husk is burned to produce steam. Steam production
uses a boiler with equity of 4.3 kg of steam per kg of rice husk (Yadav and Singh
2011). Thus, the electricity can be produced with surplus of 4,147 MJ, equivalent
to 28.25% based on the total production energy needs. The complete information
is shown in Appendix 5.
Based on the calculation above, self-sufficient energy rice mill is achievable
by applying closed production system by utilizing the rice husk as the energy
resource. Energy fulfillment achieved is 128.25% of the total production energy
needs. This energy surplus can be used for the energy reserve.
The using of rice husk as energy resource can reduce the use of fossil fuel in
the rice mills. If the energy need of rice mill is assumed to be fulfilled by the grid,
it can reduce the coal consumption. Energy produced by PLN comes from coal
with ratio of 2,655 kWh per ton of coal (Sulistyono 2012). If the rice mill
consumes 204 kWh per ton of paddy, it will consume 76.8 kg coal per ton of
paddy. In comparison, rice mill needs 162 kg rice husk to process 1 ton of paddy.
Thus, the rice husk utilization will reduce the use of coal as much as 474 kg of
coal per ton of rice husk.
For the other approach, rice mill consumed about 6.44 liter of diesel (for
electricity) generation and 1.56 liter of kerosene (for drying) to process a ton of
harvested paddy (UCFCCC 2007). Based on this research, it is possible to reduce
the usage of fuel as much as 128.8 liter of diesel and 31.2 liter of kerosene per day.
It is equivalent to about 50 liter of fossil fuel per ton of rice husk (3.24 rice husk
used per day).
Furthermore, if the carbon emission factor of rice husk is compared to the
fuel, it will be found that rice husk is safer to environment. Rice husk has carbon
emission as much as 1.445 kg CO2/kg of rice husk (Capareda 2014). It is lower
than diesel and kerosene (2.673 kg CO2/liter of diesel and 2.538 kg CO2/liter of

18
kerosene). Thus, the use of rice husk will prevent the emission of CO2 as much as
105.339 kg CO2 per ton of rice husk.
Closed System Production of Rice Mill
By-product of rice production can be utilized as an energy resource and
value added product. Broken rice can be converted into rice flour. These
conversion passes through dry process using hammer mills followed by the drying
process. The range of rice flour yield production is 90% to 95%. While the rice
bran is proper to be sold for animal feed or converted into bran oil (Bagchi et al.
2015; Rachmat 2012). The closed production system model is shown in Figure 8
and the completed model is in Appendix 6.

Figure 6 Self-sufficient energy closed production system model

19
CONCLUSION AND RECOMMENDATION
Conclusion
Mass Balance Model Level 3 is chosen to be the most suitable to illustrate
real rice mill. This model is a consistent model and is able to illustrate actual
condition of rice mill because there is no significant difference with IRRI
standards and actual data. Head rice yield, rice husk ratio and rice bran ratio
generated as much as 0.572; 0.231 and 0.074 of the weight of dried paddy,
respectively.
Rice mill can be self-sufficient in energy fulfillment by applying closed
production system based on the rice husk utilization. Rice mill consumes energy
as much as 14,680 MJ for 20 tons of raw paddy. It was estimated that energy
fulfillment achieved was 128.25% of the total production energy needs. In
addition, rice bran can be utilized for animal feed or bran oil. Broken rice was
converted into rice flour.
Based on this research, every ton of rice husk utilization as an energy
resource will reduce 474 kg of coal or 50 liter of fuel (diesel and kerosene). The
use of rice husk also has potency to reduce CO2 as much as 105.339 kg CO2 per
ton of rice husk.
Recommendation
Further study is needed to calculate more detailed mass balance because the
mass balance model of this research is estimated relevant only for at least 20 tons
of paddy per day of rice mill capacity. The result of this research can be a
consideration to reduce the use fossil fuel on rice milling industries.

20
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