Life cycle assessment of rice straw-based power generation in Malaysia

Energy xxx (2014) 1e10

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Life cycle assessment of rice straw-based power generation in Malaysia S.M. Shafie a, b, *, H.H. Masjuki a, T.M.I. Mahlia c, d a

Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia School of Technology Management and Logistics, College of Business, Universiti Utara Malaysia, 06010 Sintok, Malaysia c Department of Mechanical Engineering, Universiti Tenaga Nasional, 43000 Kajang, Selangor, Malaysia d Department of Mechanical Engineering, Syiah Kuala University, Banda Aceh 23111, Indonesia b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 2 June 2012 Received in revised form 3 April 2014 Accepted 5 April 2014 Available online xxx

This paper presents an application of LCA (Life Cycle Assessment) with a view to analyzing the environment aspects of rice straw-based power generation in Malaysia. It also compares rice straw-based power generation with that of coal and natural gas. GHG (Greenhouse gas) emission savings were calculated. It finds that rice straw power generation can save GHG (greenhouse gas) emissions of about 1.79 kg CO2-eq/kWh compared to coal-based and 1.05 kg CO2-eq/kWh with natural gas based power generation. While the development of rice straw-based power generation in Malaysia is still in its early stage, these paddy residues offer a large potential to generate electricity because of their availability. Rice straw power plants not only could solve the problem of removing rice straw from fields without open burning, but also could reduce GHG emissions that contribute to climate change, acidification, and eutrophication, among other environmental problems. Ó 2014 Elsevier Ltd. All rights reserved.

Keywords: LCA (life cycle assessment) Rice straw Power generation Malaysia

1. Introduction Malaysia energy industries largely depend on fossil fuel resources in the electricity generation sector. From 1990 until 2004, total CO2 emission increased by 221% in Malaysia, and it expected to increase up to 328 million ton CO2-eq in 2020 [1] whereas fossilfuel consumption contributed more than half of the total increments in CO2 emission [2]. As a tropical country, Malaysia has an abundance of biomass resources that could be utilized for reducing fossil fuel consumption. The commitment of government to the development of RE (Renewable energy) is by introducing the Five Fuel Diversification Policy in 1999 by addition of RE as the fifth source of fuel in Malaysia [3]. Currently, the government of Malaysia encourages the utilization of biomass resources to attain the energy independence through its National Green Technology Policy [4]. In 2010, Malaysia introduced the National Renewable Energy Policy. Even though, the development of RE in Malaysia is still in the early stage, it estimated that by

* Corresponding author. School of Technology Management and Logistics, College of Business, Universiti Utara Malaysia, 06010 Sintok, Malaysia. Tel.: þ60 49287038/ þ60 174994562; fax: þ60 49287070. E-mail address: shafi[email protected] (S.M. Shafie).

utilizing only 5% of renewable energy in the energy mix could save the country RM5Billion over a period of 5 years [5]. One potential green application uses paddy residue to generate electricity. The potential of electricity generation from paddy residue is 5652.4 GWh that is 5.4% from total electricity demand in Malaysia. Unfortunately, development of paddy residue for electricity generation remains low in Malaysia. Rice husk-based power generation only amounted to 1.38 MW in 2009 [6]. While, rice straw consumption as fuel in biomass energy plants is still unavailable not only in Malaysia but in Southeast Asia [7]. Utilization of rice straw for generating electricity remains in the discussion phase in Malaysia with plans on the drawing board for 12 MW capacity of electricity using rice straw as a fuel [8]. The use of rice straw as a fuel requires a knowledge of its heating value [9]. There are a lot of studies regarding the model of predicting the ultimate and proximate analysis. Table 1 listed the studies related to rice straw heating value model. Even though the moisture content of straw is usually more than 60% on wet basis, Malaysian dry weather can quickly dry down the straw to its equilibrium moisture content of about 10e12% [6]. Worldwide development of straw utilization for energy conversion has been studied for more than 10 years; research has examined adapting straw technology from a small scale (<200 kW) to a large scale (>100 MW) and looked at ways to improve the combustion efficiency and reduce the pollutant emissions [18].

http://dx.doi.org/10.1016/j.energy.2014.04.014 0360-5442/Ó 2014 Elsevier Ltd. All rights reserved.

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Nomenclature A ARS AF BFC CT CARS DC EBRS

activity level rice straw availability (tonne) availability factor burning fraction of carbon carbon content of diesel for transportation rice straw catchment area (km2) diesel oil consumption (L/ha) avoided GHG emission from burning rice straw in the fields ECOAL avoided GHG emission from displaced coal power production EP emission pollutant (CH4 or N2O) ERS GHG emission from rice straw-based power generation EPOWER; CO2 power plant emission of CO2 ECRSC energy consumption for rice straw collection (MJ/ha) EORS electricity output power from rice straw (MW) EUD energy unit of diesel oil (MJ/L) ET; CO2 transportation emission of CO2

In recent years, approximately 130 straw power plants have been established in Denmark, whereas the construction of these power plants is even high when we take into account the other European countries. The UN has enlisted the power generation based on straw as a fundamental element when it especially comes to combating environmental setbacks [19]. In 2011 the production of rice straw in Malaysian fields was 1,933,889.3 tonnes [20]. Unfortunately, the burning of rice straw remains the current cultural practice of disposal in Malaysia [21]. One major problem of open-field straw burning is atmospheric pollution because about 1521.53 kg CO2-eq is produced from the open burning of one tonne of crop residue. This burning causes reduced air quality and human respiratory ailments [22]. Besides the potential to reduce problems associated with air quality, there is another advantage that is a move from fossil feedstock to rice straw for power production would result in a reduction of GHG (greenhouse gas) emissions [23]. One significant way to assess these concerns is through LCA (Life Cycle Assessment) which is a process that evaluates the environment impact for entire period of its life cycle [24].Some papers use the life cycle to analyze the different indicators regarding rice straw based power generation and therefore the literature of rice straw based energy production has been listed in Table 2.

EFP, S FVT FF FOT HCT HHVRS LHVRS MWC MWCO2 Ŋ sC PC PRR RGHG RSavai, yr QRS SGR T YRS

emission factor (CH4 or N2O) volume of diesel combusted for transportation farmland factor fraction oxidized of diesel for transportation heat content of diesel for transportation rice straw high heating value, MJ/kg rice straw low heating value, MJ/kg molecular weight of carbon molecular weight of CO2 overall efficiency of the plant collection efficiency carbon content in rice straw rough rice production (k tonne/ha) GHG emission reduction annual availability of rice straw, tonne/year quantity of rice straw (k tonne/ha) Straw-to-Grain Ratio plant operating hours straw yield (tonne/km2)

A few studies carried out to evaluate the life cycle of rice straw based power generation for ethanol and electricity production. The majority of biomass electricity life cycle assessments has been prepared in a European context, where Asian countries only contribute 5% from the total studies [31]. However, there are significant differences of environmental performances among the existing bio-fuel production system due to local condition management practice [32]. For this study, it uses life cycle analysis of energy consumption and environment impact to the global warming potential of rice straw based power production in Malaysia. The environmental aspect of rice straw-based power generation is important to analyze because that aspect is a key consideration for technology investment. Information on environmental aspect should be disseminated to fully understand the direction of Malaysia future energy [33]. Rice straw-based power generation potential can be assessed with respect to both environmental and economic concerns based on the Malaysian situation before a pilot study is conducted. According to [34], application of the LCA method is helpful in analyzing (and helpful in decreasing) environment effects. This paper presents an application of LCA in calculating the environment impact and energy consumption of rice straw-based power generation in Malaysia. The emissions saving from rice straw

Table 1 Listed the studies related to rice straw heating value model. Calorific value (MJ/kg)

LHV (MJ/kg)

HHV (MJ/kg)

10.24

References [10] [11] [12]

15.03 14 14.71 Experimental on California rice 15e17 HHV212.2H (%W)0.8 (O (%W) þ N (%W)) 34.8c þ 93.9h þ 10.5s þ 6.3n10.8o2.5w (in %) 14 14.97 Crushed rice straw in China 16.1 smash rice straw in China

[13] [14] [12]

[15] [16] 17.8 in Denmark

[17]

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S.M. Shafie et al. / Energy xxx (2014) 1e10 Table 2 The literature of rice straw based power production. Country

Year

Aim

Paper

Thailand Sweden

2013 2013

[25] [26]

Thailand

2012

Japan

2012

China China

2011 2010

GHG analysis of bio-DME production The performance of energy and economic of rice straw based bio-refinery Impact of socio-economic variable for electricity and ethanol production Techno-economic and environmental evaluation of bio-ethanol production The energy study of bio-fuel industries Analysis of direct and indirect environmental impact

[27] [28] [29] [30]

consumption compared to coal and natural gas electricity production are important parameters to see the potential of rice straw combusted in the boiler. The environment impact of hauling distance and plant efficiency discussed under sensitivity topic. The result of optimum and maximum distance allowed getting lower environmental impact can help the decision of plant location in the future. The conclusion of the study would provide a direction for policy maker on biomass based power plant development in Malaysia and would be a feasible study for straw based, power plant development for other countries. It also would provide the benchmark to for continuing improvement of environmental performance from rice straw power production. 2. Overall approach An LCA study is generally carried out by four phases (goal and scope definition, inventory analysis, impact assessment, interpretation) and is used to quantify major potential environmental impacts related to the aim of study. Generally LCA boundaries about the rice straw electricity production is used comprehensive boundary starting from rice straw production to electricity generation. 2.1. Goal and scope This study performs a LCA of electricity generation from rice straw alone and conventional fuel (coal and natural gas) in Malaysia.

3

The aim of this study is to identify the environment impact of rice straw consumption for power generation in Malaysia and to compare it with conventional fuel electricity production. Accordingly, the more specific objectives of the study are to (a) calculate the environment impact and energy consumption of rice straw based electricity generation in Malaysia, (b) compare the environmental performance between rice straw and conventional fuel (natural gas and coal) for electricity generation and (c) analyze the sensitivity of the parameter that most effect the life cycle emissions. The functional unit used in this study is 1 kWh of electricity generated by rice straw and by conventional fuel in power plant. A reference as 1 kWh is used due to common applied among LCA users [35]. The result from rice straw alone is compared with conventional fuel reference system which produces the same amount of electricity generation. Even though, the goal and scope are identical with other studies, the outcome result may obtain in different ways due to different choices and approaches applied during the studied [36]. 2.2. System boundaries The system’s boundary contains the processes for paddy production, rice-straw collecting, rice straw transportation and electricity generation. The environment impact involves in each process is taken into account. If the boundary is set too narrowly some important impacts might be undetected; conversely, if the boundary is set too broadly, impacts other than those of interest might be included [37]. Most researchers have decided that the boundaries for bio energy LCA begin with the crop grown (input) and end with energy production [23,38e40]. In regard to the biomass life cycle, biomass production is included in most bioenergy LCAs [31]. The system boundaries applied in this study is starting from paddy production process and end up at biomass boiler process which is the same boundary setting or applied in that paper [32]. The steps involved in the process include: paddy production, rice straw collecting, rice straw transportation and power generation. Fig. 1 shows the schematic presentation of steps involved in this study. For each step, the energy consumption and GHG (greenhouse gas) emission were calculated. Figs. 2 and 3 are

Fig. 1. System boundaries for rice straw-based power generation.

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Fig. 2. System boundaries for coal based power generation.

Fig. 3. System boundaries for natural gas based power generation.

the system boundaries for coal and natural gas based power generation.

2.3. Inventory analysis and impact assessment In this phase, data are collected for each process involved to meet the goal of defined study.

2.3.1. Collected data The study focused on the Northern region of Malaysia that encompasses the states of Perlis, Penang, Kedah and Perak and covers an area of 17,816 km2. Current agriculture activities in the Northern region are cultivation of paddy with almost 42% out of 800,000 ha agriculture land. About 61.2% of paddy productions in Malaysia is from Northern region areas [41]. Table 3 shows the availability of rice straw for each state in 2011 [42]. The paddy production processes requires fertilizer, pesticides, mechanical field operation and irrigation. Data were drawn both from Refs. [34,43e45] and from questionnaires sent to selected farmers in the northern region of Malaysia. The rice straw collecting process uses the baler machine, tractor and stump cutting machine [46]. The baling method is used because it is less expensive compared to others methods [17,47]. The data to analyze was taken from Ref. [48] and an interview session with Manager MADA at the B11 area. Emissions for rice straw collection were calculated based on the machine’s diesel combustion. Rice straw transportation consists of two processes which are from rice straw field to collection centre and from collection centre to power generation (refer Fig. 1). For estimating for both distance to transport a unit of rice straw, it is assumed that the rice straw is distributed uniformly in the whole catchment area. Equation (1) [49] used to estimate the rice straw catchment area.

CARS ¼ ARS =ðYRS  sC  AF  FFÞ

(1)

It assumed that each district consist a rice straw collection

Table 3 Availability of rice straw in Northern Region of Malaysia, 2011.

centre and state has the rice straw power plant in the centre. Table 4 shows the parameter use for transportation process. Paddy straw-based electricity generation is a new system that has not yet reached its decommissioning age [30]; this means that the data sources are limited. Table 5 show the main process of life cycle of rice straw power generation and their data sources. For power generation, the energy consumptions and emissions data were taken from Ref. [51], and rice husk-based electricity generation was taken from Ban Heng Bee Rice Mill, Pendang Kedah. According to [23], rice straw-based power generation can be evaluated by referring to current conditions of feasible rice-husk power plants operating in Malaysia. Today, almost all rice straw is burned in Malaysia [52], but the implementation of rice strawbased power generation could avoid the GHG emissions from open burning as well as that from fossil fuel-based power generation that focuses on coal and natural gas. Equation (2) used to calculate the GHG emission reduction [23]. GHG emission from open burning is calculated based on the Equation (4) from Ref. [12].

RGHG ¼ ðEBRS þ ECOAL Þ  ðERS Þ

(2)

The emission data for coal and natural gas based power generation used the database from NREL [54] and Malaysia Department of Environment [55]. 2.3.2. Analysis of rice straw lifecycle Life cycle analysis of electricity production from rice husks involves two steps which are rice straw preparation and power generation. Energy consumptions and emissions of all processes for paddy straw-based power generation were identified using material and energy balances (See Fig. 1). 2.3.2.1. Rice straw preparation. Rice straw preparation involves the paddy farming process, collecting rice husks and transporting them to the power plant. Total energy consumption for the paddy farming process is 12225.97 MJ/ha [45]. The amount of rice straw production was derived using the Equation (3) [12]. The value of SGR is 0.75 [12].

Table 4 Parameter use for transportation process.

State

Area (Ha)

Paddy production (ton)

Rice straw production (ton)

State

T1PP

Perlis Kedah Penang Perak

52,075 215,930 25,564 82,150

232,674 878,430 144,613 323,445

174,505.5 658,822.5 108,459.8 242,583.8

Kedah Penang Perak Perlis

15.29 8.91 23.24 e

> CC

(km)

T2CC

> POWER

(km)

55.49 15.45 81.78 15.91

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Table 5 Main process of life cycle of rice straw power generation and their data sources. Process

Subsystems

Sources of data

1. Paddy production

Fertilizers

Measure data from Northern paddy farm area Literature data [56] Measure data from interview session (Senior Engineer, Irrigation and drainage service, MADA) Data from questionnaire to selected farmer in Northern region Literature [45] Data from Ref. [57] Literature data [44] Data from four case projects of rice straw in MADA area Data from four case projects of rice straw in MADA area Data from wood waste combustion

Irrigation Mechanical field operations Pesticides 2. Rice straw collection 3. Rice straw transportation 4. Power generation

Mechanical equipment Transportation system Rice straw bale combustion Electricity generation

QRS ¼ PRR  SGR

(3)

Energy consumption for rice straw collection considers diesel consumption in machinery [59]. Rice straw collection in Malaysia uses the baling technique because the method is simple and involves less cost. The average mass of a rice straw bale is 450 kg. Equation (4) used to calculate the energy consumption for rice straw collection.

ECRSC ¼ EUD  DC

(4)

Energy unit of diesel use was 47.8 MJ L1. Data was taken from MADA B11, Kedah who reported that 7L diesel was used per 1 ha of paddy fields, including all machinery needed in rice-straw collection using the baling technique. Transportation involve the process of rice straw from paddy production to collection centre (T1PP > CC) and collection centre to power plant (T2CC > POWER). The majority of vehicles used to transport material from Malaysian paddies have a capacity of between 1 and 3 tonnes per load [60]. In this analysis the T1PP > CC link used a light truck (lorry) below 1.5 tonne capacity with fitted 2 bales of rice straw per vehicle (lorry). Rice straw transportation energy is calculated from energy unit of diesel (43.1 MJ L1), fuel consumption (5.5 km L1), average distance (100 km) and the amount of rice straw (4853.1 kg ha1). The transportation of rice straw bale from collection centre to power plant, T2CC > POWER consumed the truck with 400 800 which had 4 km L1 [61]fuel consumption and able to carry 20 bales per truck. The CO2, CH4 and N2O emissions from transportation are calculated based on Equations (5) and (6) [62].

ET;CO2 ¼

X

   FVT  HCT  CT  FOT  MWCO2 MWC

EP ¼ AS  EFP;S

(5)

  EORS ¼ RSavai;yr  s  LHVRS 3:6  T

The natural gas based generation offered net thermal efficiency over 55% [64]. The emission of CO2 emission is 0.32 kg per kWh, calculated as Equation (8) [65].

  EPOWER;CO2 ¼ PC *BFC *MWCO2 MWC HHVRS

2.3.3. Impact assessment Actually, there is hardly standard procedure set of environment impact categories applied [67]. According to [31], the majority of bio-energy LCAs studies applied the midpoint impact categories which use the CML (Centrum voor Milieukunde Leiden) method. In this paper, for the life cycle impact assessment, the CML 2001 method was used and the environmental impacts considered include acidification, climate change, eutrophication, toxicity and summer smog. In general, the different methodologies give similar characterization results for impact categories such as climate change and acidification [35].Table 7 lists the environmental impact categories of CML baseline [35].

Table 7 Environmental impact categories of CML baseline [35]. Environmental impact category

Relevant emissions

Unit

Acidification

Sulfur dioxide SO2 Nitrogen oxides NOx Hydrochloric acid HCL Hydrofluoric acid HF Ammonia NH3 Carbon dioxide CO2 Nitrous oxide N2O Methane CH4 Chlorofluorocarbon CFCs Hydrochlorofluorocarbon HCFCs Phosphate PO3 4 Nitrogen oxides NOx Nitrogen Nitrates NO3 Ammonia NH3 Arsenic Chromium equivalents VI Benzene Hexachlorobenzene

kg SO2 equivalents

Climate change

Eutrophication Table 6 Emission factor for rice straw fired boiler. Emission N2O Species (kg/kWh) Emission factor

CH4

SOx

NOx

CO

2.01  105 3.25  105 3.87  105 7.58  104 9.28  104

(8)

Since Malaysia still not available the rice straw based power generation the emission factor for rice straw fired was assumed as dry wood combustion in the boiler, which taken from USEPA External Combustion Report [66]. Table 6 show the resultant emission factor for rice straw fired boiler.

(6)

2.3.2.2. Power generation. Electricity output power from rice straw, EORS calculated based on Equation (7) [49]. HHVRS and LHVRS are 16.28 MJ/kg and 15.34 MJ/kg based on collected after harvest [63].

(7)

Toxicity

kg CO2 equivalents

kg PO3 4 equivalents

kg 1,4-dichlorobenzene (DB)

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Table 8 GHG emissions and energy consumption from rice straw preparation. Rice straw preparation stages

Energy consumption (MJ/kg rice straw)

CO2 emission (g)

Nitrous oxide emission (g)

Methane emission (g)

CO2-eq emission (g)

Paddy Production Rice straw collection Transport

2.52 0.11 0.87

1690 3.89 128.09

295.02 0.0291 0.8969

1486.5 0.0048 0.0488

91.52 3.92 129.04

Table 9 Emission from life cycle rice straw-fired alone for 1kWh electricity generated. Emission Unit/kg

CO2 0.36

CO 2.88  10

CH4 3

1.63  10

likely due to difference between studies in farming location, type, allocation method, energy and emission coefficients [72].

N2O 2

2.86  104

3. Results and discussion 3.1. Environment and energy assessment for rice straw preparation GHG emissions and energy consumption is calculated for three stages of rice straw preparation; these stages are paddy farming, rice straw collecting and transportation to the power plant. Table 8 shows the GHG emissions and energy consumption from rice-straw preparation. The highest energy consumption for rice straw preparation is from paddy production, which amounts to 72% of the total. This is identical with wheat crop study in Canada [68], that consumed the highest energy in farming stages due to nitrogen fertilizer. Consumption of fertilizer, pesticide and agriculture machinery use were major contributors to the total energy consumption [69]. Energy consumption of paddy production included both direct and indirect energy. These included fuel consumption and human load. The utilization of seed, pesticide, fertilizer and machinery was also categorized under indirect energy. Nevertheless, the paddy production process has a great advantage in relation to the global warming impact, due to absorption of carbon dioxide through photosynthesis [32]. Considering all the preparation stages of rice straw preparation, the highest contribution to GHG emissions was from transportation with 57.48% of the CO2-eq emission. The overall contribution of rice straw preparation to GHG emissions is 224.48 g CO2-eq/kg rice straw or 261.3 g CO2-eq/kWh. This emission is lower compared to cucumber production in Iran which is contributed 526.7 g CO2 per kg cucumber [70]. The life cycle emission of corn stalk based biofuel production is obtained 16.15 g CO2 per kg corn with transportation distance 5.8 km [71]. Other difference in emissions is

3.2. Rice straw-based electricity generation Emission of rice straw-based electricity generation begins with paddy production and continues to power generation (Fig. 1). Table 9 indicates the emissions of life cycle rice straw fired alone gases for 1 kWh electricity generated. The obtained CO2-eq emission is 0.845 kg CO2/kWh which is lower than wheat straw fired alone, 1.076 kg CO2-eq/kWh and Brassica carinata fired alone with 1.086 kg CO2-eq/kWh [73]. CO2 emission results were obtained followed a study done in 1999 [74]. About 42.6% GHGs emissions were contributed from CO2 gas. Rice-straw electricity generation had zero carbon emissions when CO2, BIOGENIC consumed 1.67 kg/ kWh. Fig. 4 shows the CO2-eq emissions between base case (58 km) and 250 km for each processes of 1 kWh rice straw-based power generation involved in the system boundaries. Transportation contributes 6% to the total CO2-eq for the base case. Increase in the distance of T1PP > CC and T2CC > POWER the contribution of transportation goes to 42%. The distance of rice straw bale transportation contributed to the global warming (0.1875% per km) is much higher than rice husk with 0.024% per km [75] due to vast condition of bale rice straw. The rice straw bales are transported in 1.5 tonne lorries, consuming a large amount of space, with only 2 bales per lorry. By using a larger truck for transporting bales, GHG emissions could reduce as the result of fewer trips taken. According to [76], payload effect the total emission of biomass based power generation. Table 10 indicates the characterized results for 1 kWh of rice straw-based electricity generated. The CO2 gases cause climate change that contributes the highest impact to the environment as identical to LCA wood based electricity generation analysis in Japan [77]. Most of the process emitted the highest of CO2 gases. Only as an exception, the paddy production emitted the CH4 and N2O gases. SO2, NOx and NH4 all contribute to acidification [24]. The highest contribution to both impacts comes from rice straw transportation

Fig. 4. CO2-eq emission between base case (58 KM) and 250 KM for each processes.

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Table 10 Characterized results for LCA of 1 kWh of electricity (CML 2001). Acidification Climate change Eutrophication Toxicity Summer smog

6.78 4.30 1.46 1.41 5.22

103 101 103 103 103

    

kg kg kg kg kg

SO2-Eq CO2-eq PO4-Eq 1,4-DCB-Eq formed ozone

Table 11 GHG emission potentials comparison for 1 kWh for entire life cycle assessment. GHG emissions, kg

Paddy Straw Coal Natural Gas

CO2

NOx

CO

NH4

N2O

0.36 1.21 0.45

1.15  102 3.98  103 3.65  104

2.88  103 2.13  104 3.06  104

1.60  102 1.64  103 2.91  1011

2.86  104 2.02  108 8.17  106

with 42.42% for acidification and 77.66% for climate change. These values are considered lower than value from coal-based power generation (0.3134 kg SO2-eq/kWh). All the impact results from rice waste-based power generation are much lower compared to coalbased power generation [38,78e80]. 3.3. Comparison with coal and natural gas based electricity generation Rice straw-based power generation contributes 0.845 kg CO2-eq emission per 1 kWh of electricity generated. Open-burning rice straw contributes 1.38 kg CO2-eq with an emission factor of 1460 g/ kg [81] and coal-based electricity generating contributes 1.25 kg CO2-eq emission. Therefore, the GHG emission saving is 1.79 kg CO2 e eq per kWh. GHG emissions from rice straw-based power generation are less compared to contributions both from open burning and from coal-based electricity generation. The data also [30] indicated that straw based electricity generation has far fewer GHG emissions than coal. The pulverized coal power plant obtained the GHG emissions about 1.3kgCO2-eq/kWh from the mining process to power production setting boundaries [82]. The GHG emission saving from natural gas power generation is 1.05 kg CO2-eq per kWh. Table 11 shows the GHG emission potential comparison for 1 kWh for entire life cycle assessment. Table 12 indicates result comparison with others study in the straw based power generation. The result seems not identical due to system boundaries setting and input data source. It identical to conclusion from Ref. [83], indicated that the result or finding of LCA studies are difficult to compare due to research questions, method and data set selection give a significant impact to the outcome. The assumption and consideration of certain parameter depends on National level activities would generate different output. The size of straw bale transport also effected the total GHG

Table 12 Result comparison with others study in the straw based power generation.

Country Biomass fuel Bale weight (kg) Collection centre distance (km) Life cycle GHG reduction (g CO2-eq/kWh)

This study [27]

[30]

Malaysia Thailand Rice straw Rice straw 450 58 (base) 25e32

China Spain Wheat straw Wheat straw 15e18 20e42 100

560

664

193

[73]

1076

Fig. 5. Global warming potential saving from rice straw based power generations and total CO2 emission from Malaysia electricity production.

emissions. The most significant, are the biomass fired power station efficiency and also the resource transport distance [73]. If all rice straw generated in the fields was utilized fully for power generation, 1.93 Mt could be generated 1809.41 GWh in 2011. GHG emissions saving from coal-based electricity generation would be 1.03 Mton CO2-eq. Fig. 5 shows the graph of global warming potential saving from rice straw open burning and coal based power generations and total Malaysia CO2 emission from electricity generation. Malaysia CO2 emission from electricity generation sector shown an exponentially increase pattern for each year. The study by Ref. [84], indicate that the average annual growth rate of emission was 14.81% for CO2, 10.32% for SO2, 14.38% for NOx and 21.52% for CO. According to [85], Malaysia is one of the world’s fastest growing countries in terms of carbon emissions. Before 2008, total CO2 emission less than avoided of global warming potential. In 2010, the CO2 emissions reach 101.64 million tonne. In 2011, the electricity generation sector contributed the highest sources of global warming and acidification with N2O emissions and SO2 emission with 470292 tonnes (61%) and 86497 tonnes (46%) respectively [86]. However, the rice straw based power generation if applied can reduce the CO2 emission up to 1% of total CO2 emission in Malaysia. This small percentage of reduction will become more attractive in the future, as Malaysia strives to reduce its carbon emission. Table 13 listed the GWP (Global warming potential) saving in Northern region of Malaysia based on rice straw availability. The total potential installed capacity in Northern region was 132.4 MW which is 0.61% from total installed generation capacity in peninsular Malaysia for 2011. Among of the state in the northern region, Kedah provided the highest GWP saving which is 55.7% with 73.7 MW installed capacity. 3.4. Sensitivity analysis The impact of different assumptions on the results can be measured by different parameters and the observation of subsequent changes. In addition, with a view to identifying the impacts of change in power plant size, distance and plant efficiency, sensitivity analysis was aptly conducted.

Table 13 Potential in Northern region of Malaysia based on rice straw availability. State

Potential capacity (MW)

GWP saving (MtCO2-eq per year)

Kedah Penang Perak Perlis

73.7 12.1 27.1 19.5

0.405 0.0673 0.147 0.108

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Fig. 6. Relationship between the plant efficiency and CO2-eq emission.

Plant efficiency gives significant result to the overall GHG emissions as same as conclusion made by study from wheat straw [73]. Fig. 6 show the relationship between the plant efficiency and CO2-eq. Their linear relationship was CO2-eq per kWh ¼ 0.023s þ 1.061. Increase 0.5% plant efficiency, resulted the reduction about 2.3% of total GHG emissions. The plant efficiency could be vary with 2e3% points depending on fuel moisture, boiler pressure drop and steam data [87]. Rice straw transportation may have significant implications for optimizing the plant performance. Fig. 7 shows the graph of LCA GHG Emission for three different plant capacities (50 MW, 100 MW, 150 MW) with varies the distance of T1 and T2. The capacities of rice straw bale per lorry give significant impact to the total GHG emission for rice straw based power generation. Small capacity below 50 MW has a same pattern of GHG emission with distance. The system boundary consists of two types of transportation links which are T1 (transportation of bale rice straw from paddy production to collection centre) and T2 (transportation of bale rice straw of bale rice straw from collection centre to power plant). T2 has slightly higher impact to GHG emissions compare to T1when varies the distance and plant size parameter. Fig. 8 shows the specific GHG emissions with vary the distance. At shorter distance, T1 contributes more than T2 to the total GHG emission. After 110 km, T2 emission became more dominant than T1. In this case, the minimum GHG emissions can be obtained by designing the distance of collection centre to power plant (T2) not more than 110 km. It shows the same pattern correction from the biomass haulage study in Ireland [76]. Still, the suggestion from Refs. [88], nearly 78% of survey respondents believed that the plant site

Fig. 7. LCA GHG Emission for three different plant capacities (50 MW, 100 MW, 150 MW) with varies the distance of T1 and T2.

Fig. 8. Specific GHG emissions with varies the distance.

should be turned up within a 20 km radius from the resource points. T1 has 0.97% increase for each 10 km increase, while T2 only 0.13% increases with 10 km increase. It means, for long distance it is better to use the big size of lorry capacity that can save the GHG emissions. The plant capacity gives an impact to the total GHG emissions with 4832.65 ton CO2-eq per MW. The GHG Emissions change in distance with varies the plant size is presented in Fig. 9. Varies the distance of T1 is more affected on CO2-eq emissions compared to T2 with 10% more. Fig. 10 shows the total GHG emissions varies with distance for rice straw based power generation and coal based power generation. The maximum total distance should be below 235 km per trip for GHG emission below coal based power generation. 4. Conclusion The highest energy consumption for rice straw preparation is from paddy production which is 72% of the total. Considering all the preparation stages for rice straw preparation, the biggest contribution to GHG emissions is from transportation with 57.48% of CO2eq emission. Rice straw-based power generation contributes 96.65% of CO2 gas to GHG emissions. Transportation process has significant implication to the total CO2-eq emission. T2CC > POWER link slightly have higher impact of GHG emissions compare to T1PP > CC with varies the distance and plant size. The distance of collection centre to power plant less than 110 km to obtains minimum GHG emissions. The maximum total distance should be below 235 km per trip for GHG emission below coal based power

Fig. 9. GHG Emissions change in distance with varies the plant size.

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Fig. 10. Total GHG emissions vary with distance for rice straw based power generation and coal based power generation.

generation. All impact assessments from rice straw are much lower compared to coal and natural gas-based power generation. The current management practice in Malaysia for disposing of paddy straw residue is open burning. Rice straw power generation can save GHG emissions of about 1.79 kg CO2-eq/kWh compared to coal and 1.05 kg CO2-eq/kWh with natural gas based power generation. Thus, a rice-straw power plant not only removes the rice straw from field without open burning, but also saves GHG emissions that can contribute to climate change, acidification, and eutrophication, among other environmental problems. Issues regarding the government perspective on policy for encouraging the utilization of biomass-based residue and power plant development should be analyzed in depth in the near future. Local criteria (plant size, location, and supply) also need further assessment for practical implementation. References [1] Shamsuddin AH. Development of renewable energy in Malaysia strategic initiatives for carbon reduction in the power generation sector. Procedia Eng 2012;49:384e91. [2] Muis ZA, et al. Optimal planning of renewable energy-integrated electricity generation schemes with CO2 reduction target. Renew Energy 2010;35(11): 2562e70. [3] Mohamed AR, Lee KT. Energy for sustainable development in Malaysia: energy policy and alternative energy. Energy Policy 2006;34(15):2388e97. [4] National green technology policy [cited 2011 13 November]; Available from: http://www.greentechmalaysia.my/index.php/green-technology/greentechnology-policy/national-green-techology-policy.html; 2011. [5] Hashim H, Ho WS. Renewable energy policies and initiatives for a sustainable energy future in Malaysia. Renew Sustain Energy Rev 2011;15:4780e7. [6] Abdel-Mohdy FA, et al. Rice straw as a new resources for some beneficial uses. Carbohydr Polym 2009;75(1):44e51. [7] Carlos RM, Khang DB. Characterization of biomass energy projects in Southeast Asia. Biomass Bioenergy 2008;32(6):525e32. [8] Paddy Straw programme [cited 2011 7 November]; Available from: http:// www.mada.gov.my/web/guest/236; 2011. [9] Vargas-Morenoa JM, et al. A review of the mathematical models for predicting the heating value of biomass materials. Renew Sustain Energy Rev 2012;16: 3065e83. [10] Prasertsan S, Sajjakulnukit B. Biomass and biogas energy in Thailand: potential, opportunity and barriers. Renew Energy 2006;31(5):599e610. [11] Singh J, Panesar BS, Sharma SK. Energy potential through agricultural biomass using geographical information systemda case study of Punjab. Biomass Bioenergy 2008;32(4):301e7. [12] Gadde B, Menke C, Wassmann R. Rice straw as a renewable energy source in India, Thailand, and the Philippines: overall potential and limitations for energy contribution and greenhouse gas mitigation. Biomass Bioenergy 2009;33(11):1532e46. [13] Kargbo FR, Xing J, Zhang Y. Property analysis and pretreatment of rice straw for energy use in grain drying: a review. Agric Biol J N Am 2010;1(3):195e 200. [14] Valerio V, V A., Nanna F, Barisano D. Chemical characterisation of biomass feedstocks for the gasifier test. In: Task 5.3. Biomass selection and characterisation, Braccio G, Editor, Sezione Energia da Biomasse.

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