Life Cycle Inventory Analysis of Rice Produced by Local ...

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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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

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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

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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)