life cycle inventory analysis of rice produced by local
TRANSCRIPT
Research PaperJournal of JSAM 67(1) : 6167, 2005
Life Cycle Inventory Analysis of Rice Produced by Local Processes
Poritosh ROY*1, Naoto SHIMIZU*2, Toshinori KIMURA*2
Abstract
Rice processing is one of the most important agro-industry. It consumes a considerable amount of
energy and is responsible for environmental pollution. Life cycle inventory analysis has been
performed on rice (parboiled and fresh) produced by different production processes (vessel, small-boiler, medium-boiler and untreated) to find an environmentally-friendly rice production process.
The inventory results (energy consumption, atmospheric emission and solid waste) gradually
decreased from the small-boiler to the untreated process (small-boiler>vessel>medium-boiler>
untreated) and there is no waterborne emission in the case of the untreated process. The untreated
process was found to be more environmentally-friendly compared to the others, however due to the lowest head rice yield (whole kernels after milling), it consumes greater resources (paddy). Among
the parboiling processes the medium-boiler was found to be better, which has a lower energy
inventory, atmospheric emission and solid waste compared to the others. This study also reveals that
fuel switching only for cooking (biomass to electricity ; electricity was assumed to be generated from
biomass by IGCC technology) conserved primary energy (biomass) and reduced atmospheric emission
(CO2, CO, CH4, TSP, NOR, and SOX) significantly.
[Keywords] rice, processing, life cycle, inventory analysis
I. Introduction
The food industry is one of the world's largest in-
dustrial sectors. While food processing is not consid-ered to be amongst the most environmentally hazard-
ous industries, nevertheless, they can cause severe organic pollution if designed or operated with insuffi-
cient attention to the environment (Ramjeawon, 2000). Use of energy resources is a major source of envi-
ronmental pollution. Biomass is the major source of energy in most developing countries and biomass
burning has been identified as a major source of at-mospheric pollution (Crutzen and Andreae, 1990). In
Bangladesh, 63% of the total energy consumption is met by biomass fuel and 37% is commercial fuels
(BBS, 1993). Households sectors consume 80% of total biomass energy and rural households use it almost
exclusively for cooking (Bani et al., 1998). The emis-sion from its use depends on the quantities of fuels
consumed and on the design of combustion system
(Bhattacharya et al., 2000). It is reported that biomass combustion contributes as much as 20 to 50% of
global greenhouse gas emission of which one-third May come from households, which has an adverse effect on human health and the environment (Smith,
1999). Therefore, efficient utilization of energy re-
sources is very important to conserve it and to reduce environmental pollution.
Rice is the staple food in some developing countries including Bangladesh. Different types of rice have
been consumed all over the world, such as parboiled and untreated rice (fresh rice). In Bangladesh, about
90% of rice is processed as parboiled (Tariq, 2002). Parboiled rice has been produced by both traditional
and modern methods. Modern methods are energy and capital intensive, and are not suitable for small-
scale operation at the village level (Au and Ojha, 1976; Bhattacharya, 1990). It has also been reported that
more than 80% of the rice is processed in villages and less than 20% is processed in commercial rice mills. In
the rural areas, various methods are being used to
produce rice and consume different amounts of energy. With the growing concern about environ-mental pollution and health risks, it is very important
to find the most environmentally-friendly rice pro-cessing method. Therefore, this study attempts to
evaluate the environmental effects of different rice
processing methods (traditional) and find the most suitable one, using LCA (life cycle assessment) meth-odology.
*1 JSAM Student Member , Doctoral Program in Agricultural Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki
305-8572, Japan *2 JSAM Member , Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki
305-8572, Japan
62 Journal of the Japanese Society of Agricultural Machinery Vol 67, No. 1 (2005)
‡U
. Materials and methods
The life cycle assessment (LCA) is a tool that can be
used to evaluate the environmental effect of a prod-
uct, process, or activity throughout its life cycle or
lifetime, which is known as `from cradle to grave'
analysis. The purpose of an LCA can be: comparison
of alternative produces, processes or services; com-
parison of alternative life cycles for a certain product
or service ; identification of parts of the life cycle
where the greatest improvement can be made. This
concept can be categorized in four steps. These are :
(1) Goal definition and scoping, (2) Inventory analysis,
(3) Impact assessment and (4) Improvement assess-
ment (SETAC). This study deals only with the first
two steps.
1. Goal definition and scoping
The goal definition and scoping stage of LCA
defines the purpose of the study, the expected product
of the study, the boundary conditions, and the as-
sumption (SETAC, 1993). Furthermore, a reference
unit (functional unit), to which all the environmental
impacts are related, has to be defined. The goal and
scope definition is very important since the study will
be carried out according to the statements made in
this phase. The goal of this study was to investigate
the life cycle of rice produced by different processes to
quantify and to evaluate the environmental impacts
of the respective processes and compare them to facil-
itate decision making.
The product of this study is rice. The production
process of parboiled rice includes : pre-steaming,
soaking, steaming, drying, de-husking and milling.
However, the production process of fresh rice consists
of de-husking and milling only. Figure 1 shows the
life cycle of rice under different processing methods.
The system boundary of this study is encircled by a
dashed line.
It has been reported that agricultural LCAs often
exclude production processes of medicine and insecti-
cides, machines, buildings, and roads because of a lack
of data (Cederberg and Mattsson, 2000; Iepema and
Pijnenburg, 2001 ; Van Dijik, 2001). In this study, en-
vironmental impacts related to the construction of the
parboiling facilities were not considered because of
the unavailability of data. Usually, the paddy and rice
are marketed at the nearby local market or at the
mill-gate in the local areas. The main transport used
for these purposes are manually operated three-
wheeled rickshaw-vans. However, in the case of large
capacity, other transports are also used, which is not a
common practice. Therefore, energy consumption in
transportation and the environmental impact from
transportation were also not considered.
The purpose of the functional unit (FU) is to provide
a reference unit to which the inventory data are
normalized. Definition of FU depends on the envi-
ronmental impact category and aims of the investiga-
tion. In this study, the FU has been defined as the
mass of the product, e.g., 1 ton of head rice. Head rice
yield is an estimate of the quantity of head rice which
can be produced from a unit of paddy and expressed
in a percentage, i.e., head rice yield={(weight of whole
rice kernels)/weight of paddy)}•~100.
2. Inventory analysis
The life cycle inventory (LCI) analysis quantifies
the resources use, energy use, and environmental re-
leases associated with the system being evaluated. In
this study, all the inputs entering and outputs leaving
the production processes of rice were listed and quan-
tified. Three parboiling processes (local parboiling
process) were investigated to evaluate the environ-
mental impacts from the parboiled rice. The produc-
tion process of fresh rice was also evaluated and com-
pared with the parboiled rice.
(1) Energy consumption
Energy is consumed in the different stages of the
rice life cycle. The use of energy for parboiling is one
of the most important sectors for energy consumption
in the rice processing industry in developing coun-
tries where parboiled rice is the staple food. Various
parboiling processes and devices are being used in a
local parboiling process. The commonly used parboil-
ing devices are vessel (0.5-1.2 t/batch), small-boiler
Fig. 1 Life cycle of rice and the system boundary of this study
ROY, SHIMIZU, KIMURA: Life Cycle Inventory Analysis of Rice Produced by Local Processes 63
(2-4t/batch) and medium-boiler (5-10t/batch). The
paddy is poured on the vessel and fires are lit under-neath of it. In boiler processes, steam is generated in
the boiler and applied to the paddy in the conical
hoppers through the connecting pipes. Figures 2 to 4
show the studied parboiling processes. The energy
consumption in these parboiling processes was meas-
ured at Gazole under Malda district in West Bengal,
India (Roy et al., 2003 b). In the local parboiling (tradi-
tional) processes, sun drying is the common practice,
i.e., no energy has been used in the drying process
of parboiled paddy. However, in this study, energy
consumption during drying of parboiled paddy was
derived from literature (Palipane et al., 1988). The
energy consumption during de-husking and milling
were measured in our laboratory. According to our
own studies, the head rice yield was considered to be
67% and 60% for parboiled rice and fresh rice, respec-
tively (Roy, 2003). The energy consumption in cook-
ing of milled rice was also taken from our own study
(Roy et al., 2004). Table 1 shows the energy forms and estimated energy consumption per ton of head rice at
different stages of rice life cycle. Then the material
and energy balances were established for each unit
process. De-husking, milling and cooking energy were considered to be the same for parboiled rice
produced by different processing methods. Based on these materials and energy balance, an inventory
analysis was done for energy.
It was assumed that the energy requirement in the
life cycle of rice was met by the biomass energy and
biomass (rice husk) as the source of primary energy
for all types of energy consumed in the rice life cycle,
except diesel energy. The biomass used in parboiling
and electricity generation is considered to be the in-
dustrial use of biomass and an improved domestic
cook-stove was used for cooking. Different processes
are being used to generate electricity from biomass.
These are : steam turbine, circulating fluidized bed
gasifier and integrated gasification combine cycles
(IGCC). Among these, the IGCC system is reported to
be more efficient than the others. Also the efficiency
of the systems depends on the capacity. The electrici-
Fig. 2 Vessel process
Fig. 3 Small boiler process
Fig. 4 Medium boiler process
Table 1 Energy forms and estimated energy consumption per ton of head rice in different stages of rice life cycle
* Derived from the literature (Palipane et al ., 1988)
64 Journal of the Japanese Society of Agricultural Machinery Vol. 67, No. 1 (2005)
ty efficiency of IGCC is reported to be 43% with the
plant capacity of 35MWth (Gustavsson,1997). It might
be an ambitious plan to produce electricity from bio-
mass by using the IGCC technology in Bangladesh
and is expected that it would be possible to generate
electricity from biomass and can be dispersed in the
local areas. The efficiency of an improved cook-stove
(ASTRA) is reported to be 30% (Bhattacharya et al.,
1999). Based on these factors the total biomass con-
sumption was determined.
(2) Atmospheric emission
To determine the atmospheric emission CO2, CO,
TSP, CH4, NOx, SOX, and VOC were considered. The
emission factors for these components were derived
from the literature (Bhattacharya et al., 2000).
(3) Water emission
The waterborne emission is caused from the
polluted water drained from the parboiling processes.
The excess water mainly comes from the soaking
process. The amount of excess water produced in the
process was taken from our own study (Roy et al., 2003
a). In the local parboiling processes (boilers), drainage
of a little amount of excess water has also been
reported during the steaming process, which is negli-
gible compared to the amount of excess soak water.
However, in the case of vessel method drainage of
excess water was not reported during or after the
steaming process. Therefore, it was not considered in
this study. Amino nitrogen, Phenol, BOD, and COD
were considered for the waterborne emission. The
following emission factors for waterborne emission
were also derived from the literature (Ramalingam
and Anthoni Raj, 1996).
(4) Solid waste
For complete combustion it produces 17.4% of ash
(Singh et al., 1980). It has also been reported that the
husk oxidization rate is 90.6 and 83.0% for industry
and improved cook-stove, respectively (Bhattacharya
et al., 2000). The amount of solid waste (ash) was
determined considering the rice husk oxidization rate
and ash content.
‡V. Results and discussion
The inventory results consist of an exhaustive list
of parameters, but in this study the only parameters
discussed from an environmental point of view are
energy consumption, air emission, water emission and
solid waste.
1. Energy consumption
In the life cycle of rice, different types of final
energy have been consumed. For parboiling, drying
and cooking processes, the thermal energy has been
used as the final energy. However, in the case of
dehusking and milling, mechanical energy has been
used. In this study, energy consumption in the par-
boiling and drying process was measured in terms of
biomass energy. On the other hand, energy consumed
in the dehusking, milling and cooking process was
measured in terms of electrical energy. Energy con-
sumption at different phases of rice processing was
varied for different processing methods. In the case of
the vessel, small-boiler and untreated processes, no
fossil fuel was used, however in the case of the
medium-boiler process, diesel energy was used to
supply water by a shallow tube-well. Water is sup-
plied through a manually operated hand-tube-well for both the vessel and small-boiler processes. Figure 5
shows the energy inventory results of this study.
Among the parboiled rice energy inventory, the
medium-boiler method was lower compared to the
others. The energy inventory was the lowest for the
fresh rice among all types of rice.
In the case of parboiled rice, energy inventory
varied only in the parboiling process (pre-steaming
and steaming). The energy consumption during pre-
steaming treatment was found to be 1501.6, 1823.1 and
901.0MJ/t for vessel, small-boiler and medium-boiler,
respectively. During the steaming process it was
2376.1, 2290.4 and 1568.5MJ/t for vessel, small-boiler
and medium-boiler process, respectively. The energy
consumption during pre-steaming process indicates
that there may be room to improve the small-boiler
process. Parboiled rice consumes a lower amount of energy compared to fresh rice in the dehusking pro-
cess, but it consumes greater energy in the milling
and cooking process. The energy consumption in
dehusking, milling and cooking process was 90.3, 94.6
and 3999.6 and 120.0, 48.0 and 3600MJ/t for parboiled
and fresh rice, respectively.
The rice processing industry consumes some ener-
gy and at the same time, it produces some energy in the forms of byproducts or waste. Rice husk is a
byproduct of the rice processing industry, which is a
Fig. 5 Inventory results: energy consumption
ROY, SHIMIZU, KIMURA : Life Cycle Inventory Analysis of Rice Produced. by Local Processes 65
source of biomass energy and considered to be con-
sumed by the system itself. In this study, biomass is considered to be the source of primary energy for
different stages of the rice life cycle and the life cycle inventory was analyzed for two options. These are:
option-1 (biomass is used for cooking) and option-2
(electricity generated from biomass is used for cook-ing). Table 2 shows the energy balance in the life cycle of rice produced under different processes and
options. It shows that all the processes have a short-age of energy. The energy shortage was found to be
the highest for the small-boiler and was the lowest
was for the untreated process. The untreated process
produced the highest amount of energy compared to the other processes because of the difference in head
rice yield (60% and 67% for untreated and parboiled rice, respectively). It indicates that the untreated
process consumed a greater amount of resource
(paddy) compared to the treated (parboiled) rice. Among the parboiled rice, the energy shortage was lowest for the parboiled rice produced under the
medium-boiler process compared to the other pro-
cesses. If fresh rice is considered to be a sustainable energy consumption option (energy shortage may be
met by agri-residues, animal wastes, tree-leaves and twigs) then the other processes might be responsible for deforestation. However, about 22 to 29% of prima-
ry energy can be conserved in the rice life cycle by
fuel switching only for the cooking process (biomass to electricity) because of the improved end use energy
efficiency. The conservation of biomass energy would reduce the intensity of deforestation. Considering the
head rice yield and energy consumption, it would be wise to recommend the medium-boiler process to pro-
duce parboiled rice even though it consumes a greater amount energy compared to the untreated process.
2. Atmospheric emission The atmospheric emission is directly related to the
energy consumption patterns. Among the rice pro-duction processes CO2, CO, CH4, TSP, NON, and SOX
were the highest in the case of the small-boiler process and the lowest for the untreated process (Figs. 6 and 7)
because of the difference in energy consumption
patterns. The air emission varied from option-1 to option-2 mainly because of the types of end use
energy (option-1: biomass; option-2: electricity) for cooking. Electricity generating technology (steam
turbine, circulating fluidized bed gasifier and IGCC) might also be responsible for the difference in air
emissions. In this study, it was assumed that IGCC technology has been used for electricity generation
from biomass (option-2). The VOC emission was ob-served only in the case of the medium-boiler process,
because of the fossil fuel (diesel) consumption and it was estimated to be 0.77g/t. The atmospheric emis-
Fig. 6 Inventory results : atmospheric emission
(CO2 and CO)
Fig. 7 Inventory results: atmospheric emission
(CH4, TSP, NOx, SOX, VOC)
Table 2 Energy balance in the life cycle of rice
Option-1: biomass was used for cooking; Option-2: electricity was used for cooking
66 Journal of the Japanese Society of Agricultural Machinery Vol. 67, No. 1 (2005)
sion inventory indicated the necessity of method
switching to reduce air emission. Among the rice
production processes, the untreated process was
found to be the best option. However, among the
parboiling processes, the medium-boiler process was
the best to reduce atmospheric emission. The fuel
switching only for the cooking process, about 24 to
30% atmospheric emission (CO2, CO, CH4, NOx, and
SOx) can be reduced, except TSP and the VOC emis-
sion. The TSP emission can be reduced about 15 to
17% and 28% for parboiled and fresh rice, respec-
tively. The fuel switching for cooking has no effect on
the VOC emission because it is emitted in the parboil-
ing process (medium-boiler only).
3. Water emission
The excess soak-water drains after the soaking
treatment is the main source of water emission in the
life cycle of parboiled rice. The soak-water discharged
from the parboiling process contained various compo-
nents and among them COD, BOD, phenols and the
amino nitrogen were calculated and reported in Fig. 8.
There is no soaking treatment in the case of untreated
rice, hence there is no water emission.
4. Solid waste
The solid waste production from different rice pro-
cessing methods is also directly related to the energy
inventory results. Untreated rice produces the lowest
amount of solid waste compared to the others (Fig. 9).
However, in the case of parboiled rice, it was lowest
for the medium-boiler process. Therefore, it would be
better to adopt the medium-boiler process to minimize
the production of solid waste from the production
process of parboiled rice. The fuel switching only for
cooking reduces about 22 to 29% of solid waste pro-
duction in the rice life cycle.
(1) General discussion
The life cycle inventory analysis of rice reveals that
all the processes have a negative effect on the environ-
ment and the intensity of environmental effects
depends on the production process of rice. This study
indicates that the substitution of rice production proc-
ess is required to reduce environmental pollution.
The untreated rice is found to be environmentally-
friendly compared to the others, however this process
has the lowest head rice yield, hence consumes a
greater amount of paddy. Considering the head rice
yield and the consumption pattern of rice, it would
be wise to recommend an environmentally-friendly
parboiling process to produce parboiled rice. Among
the parboiling processes evaluated in this study the
medium-boiler process is found to environmentally
friendly compared to the others.
‡W. Conclusions
The life cycle inventory analysis has been per-
formed on rice to provide information on the en-
vironmental effect of rice production processes to the
consumers and to the decision makers. This study
makes it possible to compare the environmental effect
of different types of rice and it reveals that all the
processes are responsible for environmental pollution,
but the intensity of pollution varies from process to
process. Thus, the substitution of rice production
process and consumption pattern would reduce the
energy consumption, atmospheric emission, water-
borne emission and solid waste in the rice life cycle.
The untreated process was found to be the most en-
vironmentally-friendly compared to the others. A
nominal incentive, motivation and awareness of envi-
ronment and health are required for method and fuel
switching. The method and fuel switching would
reduce environmental pollution, deforestation and
global warming.
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「研 究 論 文 」
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ポ リ トシ ロイ*1・ 清 水 直人*2・ 木 村 俊 範*2
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さな い 方 につ い て ラ イ フ ・サ イ クル ・イ ンベ ン ト リ分 析
を行 った。イ ンベ ン トリ(エ ネ ル ギ消 費 大 気 へ の排 出物
質 お よ び固 体 廃 棄 物)の 結 果 で は,小 規 模 ボ イ ラ方 式 〉
ベ ッセ ル 方 式>中 規 模 ボ イ ラ方 式 〉パ ー ボ イ リン グ を施
さ な い方 式 の順 位 で減 少 した。また,パ ー ボ イ リ ング を施
さ な い方 式 の場 合 に は,水 系 へ の排 出物 質 は な く,パ ー ボ
イ リン グ方 式 と比 較 して 環 境 へ の負 荷 が 小 さ い が,ヘ ッ
ドライ ス歩 留(掲 精 後 の精 米 の整 粒 割合)が 最 も低 か っ
た。中 規 模 ボ イ ラ方 式 は,他 の2つ のパ ー ボイ リ ング方 式
と比 較 して 最 も低 い イ ンベ ン ト リ(エ ネ ル ギ消 費,大 気 へ
の排 出 物 質 お よ び固 体 廃 棄物)結 果 を示 し,環 境 にや さ し
いプ ロセ スで あ る こ とが 分 か った。 米 の炊 飯 プ ロ セ ス で
消 費 さ れ る一 次 エ ネ ル ギ を バ イ オ マ ス利 用 に よ る もの か
ら電 気(IGCC技 術 に よ って バ イオ マ ス か ら発 電 され た も
の と仮 定)に 切 り替 え る ことで,大 気 へ の排 出物 質(CO2,
CO,CH4, TSP, NOx, andSOx)が 減少 す る こ とが 明 らか に
な った 。
[キーワー ド]米,加 工,ラ イフ ・サイクル,イ ンベ ントリ分析
*1学 生会員,筑 波大学大学院農学研究科(〒305-8572つく ば市天
王台1-H Tel 029-853-4650)*2会 員,筑 波大学大学院生命環境科学研究科(同 上)