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Biomass and Bioenergy 31 (2007) 656–664

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Potential for rural electrification based on biomass gasificationin Cambodia

Hitofumi Abea,b,�, Akio Katayamab,c, Bhuwneshwar P. Sahb,d, Tsuyoshi Toriub,e, Sat Samyf,Phon Pheachf, Mark A. Adamsg, Pauline F. Griersona

aEcosystems Research Group, School of Plant Biology, The University of Western Australia, Crawley, WA 6009, AustraliabJICA study team for ‘The Master Plan Study on Rural Electrification by Renewable Energy in The Kingdom of Cambodia’, Phnom Penh, Cambodia

cNippon Koei Co. Ltd., Tokyo 102-0083, JapandPasco Corporation, Tokyo 153-0043, Japan

eSojitz Research Institute, Ltd., Tokyo 107-0052, JapanfMinistry of Industry, Mines and Energy, Phnom Penh, Cambodia

gSchool of Biological Earth and Environmental Science, University of New South Wales, Sydney, NSW 2052, Australia

Received 11 August 2006; accepted 17 June 2007

Available online 17 August 2007

Abstract

Around 76% of the 10,452 villages of Cambodia will still be without electricity in the year 2010. We examined the potential of biomass

gasification fuelled by alternative resources of agricultural residues and woody biomass to increase rural power supply, using geographic

and social economic databases provided by the Royal Government of Cambodia. About 77% of villages currently without electricity

have sufficient land available for tree planting for electricity generation based on a requirement of 0.02 ha per household. Among 8008

villages with sufficient land, we assumed that those villages that had greater than 10% of households owning a television (powered by a

battery or a generator) would have both a high electricity demand and a capacity to pay for electricity generation. Those 6418 villages

were considered appropriate candidates for mini-grid installation by biomass gasification. This study demonstrated that while

agricultural residues such as rice husks or cashew nut shells may have high energy potential, only tree farming or plantations would

provide sufficient sustainable resources to supply a biomass gasification system. Cost per unit electricity generation by biomass

gasification is less than diesel generation when the plant capacity factor exceeds 13%. In order to ensure long-term ecological

sustainability as well as appropriate tree-farming technology for farmers, there is an urgent need for studies aimed at quantifying biomass

production across multiple rotations and with different species across Cambodia.

r 2007 Elsevier Ltd. All rights reserved.

Keywords: Agricultural residues; Energy tree farming; Leucaena leucocephala; Plant capacity factor

1. Introduction

Cambodia has a population of 13.6 million and isclassified as a low income country (LIC) with a grossnational income (GNI) per capita in 2004 of US$320. ThisGNI is the lowest among countries of Southeast Asia andthe Pacific, and the 16th lowest in the world [1]. Currently,

e front matter r 2007 Elsevier Ltd. All rights reserved.

ombioe.2007.06.023

ing author. Ecosystems Research Group, School of Plant

University of Western Australia, Crawley, WA 6009,

+618 6488 4257; fax: +61 8 6488 7925.

ess: abejin@plants.uwa.edu.au (H. Abe).

the total installed capacity of the registered electricitysupplier of Cambodia is 185MW [2]. While the nationalpopulation census in 1998 [3] reported that about 15% ofhouseholds have access to electricity, accessibility is skewedtowards cities, with only 9% of households in rural areashaving access to electricity compared with 54% in urbanareas. Electricity supply to the national capital of PhnomPenh and some other major cities is via the 100% state-owned company, Electricite du Cambodge (EdC). Bycontrast, electricity to rural areas is supplied by indepen-dent power producers, collectively referred to as ruralelectricity enterprises (REE).

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Prices for electricity supply vary considerably amongcommunities. The lowest residential electricity price is$90–160MWh�1 in Phnom Penh. Prices in other citiessupplied by EdC are slightly higher than that in PhnomPenh ($130–230MWh�1). The price of electricity suppliedby most REE is between $500 and 900MWh�1, ten timeshigher than in Phnom Penh. There are also manynon-registered REE across Cambodia. Small-scale(o30 customers) non-registered REE often charge usersmore than $1000MWh�1. Electricity is supplied duringlimited hours (often only in the evenings) in rural areas andthere are frequent power failures owing to the poorfacilities. People living in villages without electricity supplyoften use shallow cycle lead acid batteries (e.g. carbatteries) for lighting and other electrical devices such asTV and radio. The average unit electricity price for batteryuse including re-charging batteries and battery replacementis estimated as about $1050MWh�1 [2]. Overall, people inrural areas of Cambodia are subject to both expensive andpoor-quality electricity.

The Royal Government of Cambodia is acutely aware ofhow rural communities are disadvantaged, and have set atarget of 70% of households to have electrification withgrid-quality electricity by 2030 [2]. The Government isworking to achieve this target via grid extension and mini-grid establishments, and it has been proposed that mini-grid establishment will be based mainly on renewableenergy. As all oil and petroleum products are imported intoCambodia, the development and utilization of domesticrenewable energy sources has both environmental andeconomic advantages. However, micro-hydro and windpower potential are very limited in Cambodia and solarpower generation is not appropriate for stand-alone gridsystems [2]. By contrast, biomass resources such as woodand agricultural residues are abundant in Cambodia andbiomass already accounts for some 80–85% of the nationalenergy consumption [4–6].

In this paper, we report the potential for ruralelectrification in Cambodia from biomass energy, basedon geographic and social economic databases compiled bythe Royal Government of Cambodia. We examined thepotential of biomass-powered mini-grids to supply elec-tricity to rural villages expected to be still withoutconnection to main power grids in 2010. The officialcurrency in Cambodia is the ‘Riel’, but as US dollars arecommonly used in stores and markets in Cambodia and forthe convenience of international readers, we present oureconomic analysis in US dollars. The exchange rate,US$1 ¼ 4000Riel, has been used throughout this study.We also include here details of chemical and energycharacteristics of a range of potential biomass energysources.

2. Off-grid area

There are currently 13,793 villages in Cambodia. Thenumber of villages that would be electrified by grid power

by 2010 was estimated based on the National PopulationCensus 1998 data provided by the National Institute ofStatistics [3], and the Commune Database 2003, which isfreely available on the website [7] organized by SEILA.SEILA is a rural area support program of the government.Progress of the ongoing Rural Electrification and Trans-mission Project funded by the World Bank and AsianDevelopment Bank was also taken into consideration. By2010, it is estimated that there will be 3341 villages (24%)and 832,043 households (34%) that have access to gridelectricity, while 10,452 villages (76%) and 1,625,908households (66%) will remain unelectrified (Table 1). Mostof the electrified villages are distributed in and aroundPhnom Penh, close to other major cities or along the mainroads (Fig. 1). More than 80% of the villages andhouseholds are situated within a 40 km radius of munici-palities and provincial capitals, which involves a technicallimit of 22 kV distribution line extension (Fig. 1). Whilegrid extension is critical to rural electrification, there arecurrently no further plans confirmed to undertake theextension owing to large capital costs. Consequently,alternative opportunities for electricity generation to ruralareas are critical.

3. Biomass resources

We have considered only plant biomass here aselectricity generation using bio-digestion gas (animalexcreta) and landfill gas is site specific. Direct combustionsteam turbine is the most commonly used method togenerate electricity from solid biomass in the world, butthis system is appropriate only at relatively larger scales(e.g. 41MW) [2]. Mini-grids in rural Cambodia would notrequire such large systems. Alternatively, gasificationsystems are commercially available for relatively small-scale generation, e.g. 4 kW. Consequently, we considergasification to be the most appropriate method for ruralmini-grid electrification in Cambodia.

3.1. Agricultural residues

3.1.1. Rice husks

Rice is by far the staple food of Cambodia and the majoragricultural resource in terms of area, volume and income.In 2003, Cambodia produced 4.7Mt of rice on 2300 km2

[8]. Rice husks accounted for 20% of paddy production ona weight basis [9], meaning that nearly 1Mt of rice huskswere produced in 2003. The higher heating value (HHV) ofrice husks was 15.38MJ kg�1 (Table 2), which is about one-third that of furnace oil, and one-half that of good-qualitycoal [9]. About 2 kg of rice husk is needed to generate1 kWh electricity [2]. Consequently, if all 1.6 millionhouseholds currently without electricity in Cambodiarequire 10 kWhmonth�1, a gasification plant would need380 kt of rice husks as fuel per annum. Current annual ricehusk production is nearly three-fold greater than therequired amount. Annual production of rice in Cambodia

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Fig. 1. Distribution of villages in Cambodia with electricity (black dots) and without electricity (grey dots). The circles show the area within a 40 km radius

from municipalities and provincial capitals, which involves a technical limit of 22 kV distribution line extension.

Table 1

Estimated number of villages with and without electricity in Cambodia

Electricity supplier Number of villages Number of households

With electricity EdC grid 1405 313,387

Mini-grid by registered REE 526 153,350

Mini-grid by non-registered REE 657 156,786

Expected to have electricity by 2010 Planned grid extension 753 208,520

Without electricity None 10,452 1,625,908

Total 13,793 2,457,951

H. Abe et al. / Biomass and Bioenergy 31 (2007) 656–664658

has more than doubled (112%) over the last 10 years [8],and it is expected that rice production will continue toincrease. However, rice husks are generally well utilized forhousehold cooking and cottage industries such as brickkilns. Consequently, expanded demand for rice huskresidues in some areas may negatively impact on villages,where supply is already limited and used for other purposes[5,6]. While there are currently insufficient data regardingrice husk availability to make estimates at the nationallevel, it could be considered as a high potential fuel sourceat more local scales.

3.1.2. Other agricultural residues

Around 371.4 km2 of cashew trees (Anacardium occiden-

tale) have been planted in Cambodia [8], with the areaincreasing annually. Shells of cashew nuts are about 70%of the total fruit mass, while the remaining 30% is the nut

itself. The HHV of cashew nut shell was 23.62MJkg�1,which is much higher than that of all other biomassmaterials tested (Table 2). Cashew nut shells were tested forgasification by two local NGOs, but both encounteredtechnical problems associated with the high oil content ofthe shells. Nevertheless, cashew shells may potentially be agood fuel source for direct combustion for power genera-tion if there were sufficient supply. There are no dataavailable on total tonnes of cashew nuts producedeach year in Cambodia. However, most sun-dried rawnuts (with shells) are currently sent to Vietnam as informalborder trade [10] for processing, and so the current netamount of shell available within Cambodia is unlikely to besufficient for biomass energy production.Bagasse is the residue of sugar processing from sugar-

cane, constituting about 30% of total sugarcane weight,with a HHV of 15.68–19.50MJ kg�1 [11]. Cambodia

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Table 2

Chemical and energy (HHV) characteristics for selected biomass materials collected in Cambodia

Sample name C H N S O Cl Ash HHV (MJkg�1)

(wt%, dry basis)

Agricultural residues

Cashew nuts shell 54.03 6.80 0.59 0.04 37.88 0.03 0.67 23.62

Corn cob 43.96 5.92 0.65 0.00 47.96 0.67 0.83 17.72

Rice husk 37.89 5.04 0.29 0.00 39.52 0.14 17.13 15.38

Peanut shell 45.84 5.87 1.74 0.00 43.48 0.04 3.03 18.92

Coconut shell 46.67 5.43 0.55 0.00 44.03 0.73 2.58 18.56

Cassava stem 45.25 5.99 0.80 0.00 45.31 0.43 2.21 18.59

Woody biomass

Hevea brasiliensis (rubber) 46.04 6.15 0.32 0.00 46.56 0.03 0.89 18.89

Morus alba (mulberry) 45.14 6.02 0.57 0.00 47.40 0.04 0.83 18.33

Casuarina sp. 46.95 6.17 0.40 0.00 46.40 0.07 0.01 19.27

Gliricidia sepium 45.22 5.91 1.06 0.00 46.26 0.03 1.52 18.38

Cassia sp. 45.28 5.62 0.73 0.00 47.02 0.01 1.35 17.95

Memecylon acuminatum 47.39 5.89 0.57 0.00 46.10 0.04 0.01 19.14

Leucaena leucocephala 46.99 6.23 0.75 0.00 45.10 0.07 0.86 19.53

Eucalyptus camaldulensis 48.68 6.20 0.24 0.00 44.86 0.03 0.00 20.10

Acacia auriculiformis 48.45 6.12 0.26 0.00 44.27 0.04 0.87 20.00

Chemical analysis was conducted by The Joint Graduate School of Energy and Environment, King Mongkut’s University of Technology Thonburi,

Thailand. All samples were ground into a fine-articles pass through 250mmmesh and dried under vacuum at 70 1C till constant weight. C, H, N and S were

analysed using a CHNOS analyser (Thermofinnigan, Flash Ea 1112). Thermogravimetric analysis (900 1C in air) was used for Ash content. For Cl content

determination, samples were mixed with HNO3 (65%) and digested by heating in a microwave digester, and the solution was analysed by using an ICP-MS

(Agilent, 7500a). O was estimated as the difference between total dry mass and mass of other elements. Higher heating value (HHV) was obtained by the

following Boie equation [11,29]: (157.4 C+520.4 H+28.1 N+46.9 S–49.7 O)� 0.00232.

H. Abe et al. / Biomass and Bioenergy 31 (2007) 656–664 659

produced 173.1 kt of sugarcane in 2003 [8]. While powergeneration by direct combustion of sugar cane residues hasbeen widely adopted by processing factories in othercountries, it has not been introduced to Cambodia and isdifficult to assess further without detailed study ofproduction and availability.

Peanut production in Cambodia in 2003 was 18.5 kt,with peanut shells already currently used for electricitygeneration via biomass gasification by one REE inCambodia. Peanut shells represent about 30% of the totalweight of peanuts, with an HHV of 18.92MJkg�1

(Table 2). The results of HHV analysis of other commonagricultural residues include 18.56MJ kg�1 for coconutshells, 18.59MJ kg�1 for cassava stems, and 18.33MJkg�1

for mulberry (Morus alba) stems (Table 2). The Centre forLivestock and Agriculture Development tested thesebiomass materials with a 9 kW capacity gasificationelectricity generator (Ankur Gas-9), imported from India.All residues were suitable for gasification, with fuelefficiencies between 1.3 and 1.5 kg kWh�1 [12]. Whileproduction of cassava in 2003 was 330.6 kt and the areaunder coconut plantation was 270.5 km2 [8], the annualproduction of coconut and cassava residues, as forsugarcane, is not known.

3.2. Woody biomass

3.2.1. Old rubber trees (Hevea brasiliensis)

There is about 400 km2 of area under rubber plantationin Cambodia [13] with 40 kt of rubber block, also known as

resin crepe rubber, produced annually [14]. The HHV ofrubber tree wood was 18.89MJkg�1 (Table 2). Therotation period for replanting rubber trees is 25–30 years,suggesting that about 3–4% of the planting area is clearedannually and about 180 t of woody biomass is obtained perhectare [15]. If 250 kt of old rubber trees is harvestedannually in Cambodia, this woody biomass could generate10 kWhmonth�1 electricity for about 1.4 million house-holds for a year, which is about 90% of the totalhouseholds currently without electricity. A large amountof harvested old rubber wood is transported to PhnomPenh as fuel for cottage industries such as brick kilns andbakeries [16], but quantitative details are not known.

3.2.2. Natural forest

While more than half of Cambodia remains forested,there has been serious deforestation over the last severaldecades. In 1960, forests covered 73% of the total land areaof the country, but this had decreased to 58% by 1998 [4].Forest cover is expected to further decrease to around 50%or less by 2010 [13]. Loss of forests has been attributedmainly to commercial logging, sometimes illegal, andextensive clearing for agriculture. Forests are also underincreasing pressure from wood harvesting for domesticneeds. Around 95% of the population is dependent onwood fuel for cooking [3]. Total fuel wood consumptionwas estimated to be about 6 million m3, while logproduction was about 1.5 million m3 in 1995 [17].Cambodia’s population is increasing rapidly with anannual growth rate of around 2.5%, such that fuel wood

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consumption in 2010 is likely to be 40% greater than in1995 [4]. While annual fuel wood consumption in someprovinces may be a minor proportion of the annual forestbiomass increment [18], there is concern that increaseddemand for wood fuel will further exacerbate deforesta-tion.

About 288 kt of woody biomass would be neededannually to generate the 192GWh required to supply the1.6 million households currently without electricity, assum-ing that each household consumes 10 kWhmonth�1. Theannual biomass increment of Cambodian forests is about50Mt, based on data from Kampong Thom province(4.77 t ha�1) [18]. The woody biomass required annually forelectrification of the whole country would only be 0.6% ofthe annual national forest biomass increment. However, asdescribed above, natural forests in Cambodia are alreadyunder heavy and often localized pressure, and extrademands to supply wood for fuel may exacerbate the riskof deforestation in some regions.

3.2.3. Forest plantations

Cambodia currently has around 111.3 km2 of treeplantations, mainly of Acacia spp. and Eucalyptus spp.[19]. The purpose of these plantations is generally produc-tion of wood chip materials for export. The selling price ofwood to woodchip companies is $15–23 t�1 [20]. Ifplantation wood is supplied for biomass power generationat $23 t�1, the fuel cost for electricity generation becomes$35MWh�1, which is about one-fifth of the $180MWh�1

fuel cost of small-scale diesel power generation in ruralareas of Cambodia. There is currently about 2500 km2 ofgrassland with scattered trees area in Cambodia [13], asubstantial proportion of which is abandoned lands andpreviously cleared forest [19]. Tree plantations for biomassproduction therefore have great potential for expansion,not only for rural electrification but also for main gridelectricity supply.

3.3. Currently installed biomass electricity generation

There is currently one bio-digestion gas and threegasification electricity generation systems installed inCambodia with a total capacity of slightly larger than100 kW. The hybrid electricity generation system consistsof solar photovoltaic (50 kW) and 2� 35 kW bio-digestiongas installed by Japan’s NEDO. This system and a 9 kWgasifier at the Centre for Livestock and AgricultureDevelopment are mainly operated for research purposes.In addition, there are two operations supplying electricitycommercially. Since February 2005, the Anlong Ta Meivillage energy cooperative supported by SME Cambodia(local NGO) in Battambang province has operated their9 kW gasifier imported from India. The Anlong Ta Meicooperative supplies electricity 6 h a day to 70 households.The cooperative purchases Leucaena wood planted bycooperative members at $20 per dry tonne for the fuel. Thecharge for electricity is $300MWh�1, which is much lower

than the $700–900MWh�1 of other REE nearby. Initialinstallation costs were covered by the Canadian Interna-tional Development Agency, but operational and deprecia-tion costs are covered by the user charge. The otherbiomass electricity operation is also in Battambangprovince. One REE owner invented a gasifier andconnected it to his existing 75 kW diesel engine. This dualfuel operation (30–40% diesel and 60–70% producer gasderived from peanuts shell, corncobs and wood) hassupplied electricity to 410 customers since February 2005.

4. Appropriate methods and potential of biomass mini-grid

4.1. Tree farming for energy production

Agricultural residues are well-utilized as domestic energysources and are not likely to be sufficient to meet electricitygeneration requirements for most regions. Harvest ofnatural forest for electricity generation is undesirable,owing to possible associated risks of deforestation andincreased pressure on this resource. By contrast, treeplantations would be highly suitable for supplying biomassfuel for rural mini-grid electrification. In the case of fast-growing legumes such as Leucaena spp. and Gliricidia spp.,farmers are able to harvest stems and branches one yearafter planting. Coppices of these species grow vigorouslyand farmers can harvest two or three times a year for manyyears [21–23]. Leucaena and Gliricidia are nitrogen-fixingtrees that grow well on degraded land and generallyimprove soil conditions. Rural villagers are encouraged toplant these species in and around gardens to improve theproduction and ecological sustainability of farmland bymany NGOs in Cambodia. Biomass electrification wouldprovide extra incentives to farmers for such activities, andselling wood to the power station would be an additionalsource of income.

4.2. Biomass production and land requirements

The annual accumulation of aboveground biomass formost tropical plantations is between 6 and 15 t ha�1 y�1

[24]. However, much higher accumulation rates have beenreported for tropical plantations in Peninsula Malaysia [25](21.0 t ha�1 y�1 at 4-y-old Acacia mangium) and forGmelina arborea in Nigeria [26]) (24.9 t ha�1 y�1 at 5.5-y-old). Up to 50 t ha�1 y�1 biomass has been harvested fromcoppiced branches of Leucaena leucocephala in India [21],but productivity varied depending on management and siteconditions [22]. There is little information on rates ofbiomass production and nutrient sustainability withrepeated harvest of either large-scale forest plantations orsmall-scale tree farms in Cambodia. However, the Depart-ment of Agriculture in Battambang province has measuredproduction of as much as 80 t ha�1 y�1 by L. leucocephala

after four years of repeated harvest in small-scale treefarms without irrigation (Ponh, unpublished data).We also conducted a survey of biomass production of

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10–12-month-old L. leucocephala at the Anlong Ta Meienergy cooperative. The mean annual woody biomassproduction was only 8.2 t ha�1 y�1 [27], but biomassproduction of the first year is usually very small. Whenwe observed the same site three months after the survey,the coppiced branches were as large as that pre-harvest,and annual production in the second year is expected to besignificantly greater. Here, we use a conservative estimateof 10 t ha�1 y�1 as a base rate of annual woody biomassproduction.

We analysed the fuel efficiency of L. leucocephala woodat the Centre for Livestock and Agriculture Development.The test was conducted over 4 h using a 9 kW gasifier, andrepeated four times. Fuel efficiency was 1.26 kg kWh�1

(1.43 kg kWh�1 for air-dried, 12% moisture content). Themonthly electricity consumption per household was pre-sumed to be around 10 kWh according to the cases of ruralareas in Cambodia and other developing countries [2].Based on a general figure of fuel efficiency of 1.5 kg kWh�1,annual consumption of woody biomass per household forelectricity generation is 180 kg. Consequently, 0.018 ha ofland per household would be required for tree planting tosatisfy biomass consumption requirements. We assumedthat grasslands and shrublands identified from the land usemap and data supplied by the Ministry of Public Worksand Transport (MPWT) (2003) were land areas availablefor tree planting. The land use map was produced based onLandsat (TM) data and aerial photos. Field verification ofland use was undertaken especially where interpretation ofsatellite images was difficult [28]. We analysed the availablegrassland and shrubland per household at the communelevel using GIS software (ArcView 9.0, ESRI). Thecommune is the smallest administrative boundary datasetavailable, with 1621 communes in Cambodia. There weresix categories of grassland (grassland, abandoned fieldcovered by grass, flooded grassland, grass savannah, grasswith termite mounds, and marsh and swamp), and fourcategories of shrubland (shrubland, abandoned fieldcovered by shrub, flooded shrub, and woodland andscattered trees (cover o10%)) in the land use map data.We excluded ‘flooded grassland’ and ‘marsh and swamp’ aspotential tree farming sites because conditions were notlikely to be suitable for plantations and such wetlands areoften areas of high conservation significance [4]. We alsodid not include ‘woodland & scattered trees (canopy covero10%)’ because such land has potential for restoration ofnatural vegetation and also may have higher conservationsignificance. Most of the communes contain more than0.2 ha of grassland and shrubland per household (Fig. 2),which is more than ten times the required area. Among10,452 unelectrified villages, 8008 villages (77%) have40.02 ha grassland and shrubland per household and 5941villages (57%) have 40.2 ha per household. In the case ofthe Anlong Ta Mei energy cooperative, the only biomasselectricity generation fuelled by energy tree farming inCambodia, all trees are planted with other agriculturalcrops or in fallow gardens. While the majority of new tree

planting is likely to be in and around gardens like AnlongTa Mei, the availability of grassland and shrublandprovides further assurance of land for tree farming.

4.3. Ability to pay

Once biomass energy mini-grids are established, thepublic will be required to utilize the generated electricityand pay for it in order for the system to be sustainable.People who use batteries for their lighting and otherelectrical devices are already electricity consumers. It wasassumed that where battery use is high, the demand andability to pay for grid electricity is high as well.Unfortunately, battery use was not surveyed in either thenational census database [3] or the SEILA communedatabase [7]. We therefore decided to use television (TV)ownership, which is included for each village data ofSEILA commune database 2003. We assumed that villageswith greater than 10% of the households having TVswould also have a high electricity demand and also acapacity to pay. Of 8008 villages without electricity andwith 40.02 ha of grassland and shrubland per household,6418 had more than 10% of households with TVs.Consequently, 6418 is the current number of potentialvillages for biomass mini-grid installation, which is 61% ofthe total number of villages that currently have no access togrid electricity. The distribution of potential villages acrossCambodia is shown in Fig. 3.

5. Economic viability

Almost 100% of electricity in rural areas in Cambodia isgenerated by diesel engines. We compared the economicefficiency of electricity production between biomass gasi-fication and diesel generation. The price of gasifiers andengines varies considerably. Consequently, we standar-dized the initial cost for gasification system as $1500 kW�1

($1000 for gasifier and $500 for engine generator) based ontests using Ankur (Indian manufacturer) gasifiers, one ofthe world’s most widely installed small gasification systems,including in Cambodia. The cost of diesel engine powergeneration was set at $500 kW�1 to standardize the qualityof biomass and diesel systems. We assumed a capitalrecovery factor of 7% and repayment period of 10 yearsfor both systems, a fuel cost for biomass of $30MWh�1

(price of biomass, $20 t�1; specific biomass consumption,1.5 kg kWh�1) and for diesel of $180MWh�1 (diesel price,$0.60 l�1; specific fuel consumption, 0.3 l kWh�1), and anannual operation and maintenance cost for biomass of 3%of the initial cost and for diesel of 5% of the initial cost.The unit electricity generation cost based on the plantcapacity factor is shown in Fig. 4. Although the capital costof the biomass system was three-fold greater than that of adiesel system, the cost of generating electricity by biomassgasification was less than that by diesel when the plantcapacity factor exceeded 13% (Fig. 4). This is due to themuch lower cost of biomass fuel. A 13% plant capacity

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Fig. 2. Area of grassland and shrubland per household (hh) analysed at commune level in Cambodia.

Fig. 3. Distribution of 6418 villages appropriate for installation of biomass gasification mini-grids fuelled by energy tree farming in Cambodia.

H. Abe et al. / Biomass and Bioenergy 31 (2007) 656–664662

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5%

5.1

10%

10.2

15%

15.3

20%

20.4

25%

25.6

30%

30.7

35%

35.8

40%

40.9

0

100

200

300

400

500

600Ficalculation

Fuel cost

Annual O & M costBiomass: 3% Diesel: 5%

Biomass Gasification

Diesel

Figures used for

Cos

t for

Uni

t Ele

ctri

city

(U

S$ M

Wh-1

)

(kWh hh-1 month-1)Monthly Consumption per Household

Plant Capacity Factor

(of capital cost)

Diesel: $180 MWh-1Biomass: $30 MWh-1

Diesel: $500 kW-1Biomass: $1,500 kW-1

Capital costrepayment) = 0.143(7%, 10-year

Capital recovery factor

Fig. 4. Cost comparison of unit electricity generation between biomass

gasifier and diesel generation (not including distribution lines).

Biomass gasification

73%

11%

16%

Diesel

24%

67%

9%

Depreciation Fuel O & M

Fig. 5. Comparison of cost breakdown of biomass gasification and diesel

electricity generation. The cost breakdown was compared at a plant

capacity factor of 13%, where the unit generation costs of two systems

were the same ($270MWh�1).

H. Abe et al. / Biomass and Bioenergy 31 (2007) 656–664 663

factor is achieved by average monthly electricity usage of13.3 kWh per household, which is slightly higher than theexpected 10 kWh per household per month in rural areas.As plant capacity factor increases, the cost per unitelectricity generation decreases and the economic advan-tage of biomass gasification against diesel generationincreases.

Electricity consumption in rural areas is usually con-centrated in the evening. However, it is crucial to createdaytime demand for electricity by activities such as waterpumping for household use and irrigation, ice making,agricultural products processing, and other businessactivities when installing a biomass mini-grid in order toincrease the plant capacity factor. The Rural ElectrificationFund (REF) sponsored by the World Bank will commencein 2006. In REF, the World Bank is considering a subsidyof $400 kW�1 for mini-grid installation fuelled by renew-able energy including biomass. Once this plan is executed,and with rising costs of diesel, the cost of unit electricitygeneration by biomass gasification becomes the same withdiesel systems at a plant capacity factor of 8%($320MWh�1) and less as plant capacity factor increases.Cost of unit biomass gasifier electricity without subsidy at aplant capacity factor of 10% is currently about$330MWh�1, while that at 20% is $180MWh�1. Withan REF subsidy of $400 kW�1, these costs are significantlyreduced to $260MWh�1 (at 10%) and $150MWh�1

(at 20% plant capacity factor).The cost breakdown of biomass gasifier and diesel

electricity generation is shown in Fig. 5. The cost break-down was compared at a plant capacity factor of 13%,where the unit generation costs of two systems were thesame ($270MWh�1). In the case of diesel generation, twothirds of cost was fuel. By comparison, fuel was only asmall fraction (11%) of the generation cost of biomassgasification and depreciation accounted for 73%. The priceof the biomass gasifier (major part of depreciation cost) isexpected to decrease with technology improvement and

demand increase. If licensed domestic manufacture offoreign products or locally invented gasifier productionoccurs in Cambodia, it would significantly lower gasifierprices. The cost of diesel electricity generation is dependentheavily on the price of oil products, and is subject to risk ofsharp fluctuations. The percentage of fuel cost in thegeneration cost of both biomass and diesel systems increasewith the increase in plant capacity factor. Fuel cost of adiesel system flows out of the country; on the other hand,fuel cost of a biomass system remains in the communityand vitalizes the local economy.

6. Conclusion

Tree farming for biomass production by local farmers islikely to be the most sustainable method of fuel supply forbiomass gasification electricity generation for a rural mini-grid. More than 60% of the villages in Cambodia expectedto be still without electricity in 2010 are potentialcandidates for biomass gasification mini-grid in terms ofland availability for tree planting and ability to pay forelectricity by villagers. Biomass gasification is economicallycompetitive compared with diesel generation. The cost forunit electricity generation of biomass gasification becomeslower than diesel generation when the plant capacity factorexceeds by 13%. The largest cost associated with powergeneration via biomass gasifier is the depreciation, whichcould be reduced if gasifiers were manufactured locally.However, there are few accurate estimates of the produc-tivity of plantations and tree farms in Cambodia. In orderto ensure long-term ecological sustainability as well asappropriate tree farming technology for farmers, there isan urgent need for further studies that quantify biomassproduction across multiple rotations and with differentspecies across Cambodia.

Acknowledgements

This study was conducted as part of a project funded bythe Japan International Cooperation Agency (JICA): ‘Themaster plan study on rural electrification by renewable

ARTICLE IN PRESSH. Abe et al. / Biomass and Bioenergy 31 (2007) 656–664664

energy in the Kingdom of Cambodia’. The authors thankSME Cambodia for providing data about the Anlong TaMei biomass electrification project. Khieu Borin andMiech Phalla of the Center for Livestock and AgricultureDevelopment provided biomass fuel efficiency test forgasification. Nakorn Worasuwannarak of The JointGraduate School of Energy and Environment and KingMongkut’s University of Technology Thonburi, Thailandprovided the ultimate analyses of biomass samples. UngChanpisey and Takeshi Okamura of the JICA study teamprovided logistical support. We also thank three anon-ymous reviewers for their valuable comments and criticism.

References

[1] World Bank. World development report 2006: equity and develop-

ment. Washington, DC, USA: Oxford University Press; 2005. p. 320.

[2] Nippon Koei Co. Ltd. Interim report: the master plan study on rural

electrification by renewable energy in The Kingdom of Cambodia.

Phnom Penh, Cambodia: Japan International Cooperation Agency

(JICA); 2005. p. 476.

[3] Anonymous. General population census of Cambodia. Phnom Penh,

Cambodia: , National Institute of Statistics (NIS) of Cambodia; 1999.

p. 367.

[4] Anonymous. Cambodia’s initial national communication. Phnom Penh,

Cambodia: Ministry of Environment (MOE) of Cambodia. p. 57.

[5] De Lopez T. Assessing Cambodia’s potential for bio-energy. Phnom

Penh, Cambodia: Cambodian Research Centre for Development;

2003. p. 43.

[6] Williamson A. Sustainable energy in Cambodia: status and assess-

ment of the potential for clean development mechanism projects.

Phnom Penh, Cambodia: Cambodian Research Centre for Develop-

ment; 2004. p. 66.

[7] Anonymous. Seila commune database 2003. /http://203.189.

130.76:8080/database/index_en.asp?language=en&pgid=13&title=0S(accessed 4.01.2007).

[8] Anonymous. Agricultural statistics 2003–2004. Phnom Penh, Cam-

bodia: Ministry of Agriculture, Forestry and Fisheries (MAFF) of

Cambodia; 2003. p. 81.

[9] Natarajan E, Nordin A, Rao AN. Overview of combustion and

gasification of rice husk in fluidized bed reactors. Biomass &

Bioenergy 1998;14:533–46.

[10] Mathew AG. Cashew nuts, essential oils, and spices feasibility study

in Cambodia on processing for export development. International

Trade Centre (Project No. CMB/02/G01); 2003. p. 14.

[11] Reed TB. A survey of biomass gasification. Volume 2—principles of

gasification. SERI/TR-33-239. Golden, CO: Solar Energy Research

Institute; 1979. p. 241.

[12] Miech P. Adding value of edible fibrous biomass residues in

ecosystem farm for socio-economical and environmental benefits.

MSc dissertation. Swedish University of Agricultural Sciences; 2005.

p. 46.

[13] Hong N. Country paper on some aspects of forestry in Cambodia.

Rome, Italy: FAO; 1997. p. 16.

[14] Marubeni Corporation. Summary for rubber tree afforestation in

Mondul Kiri Province, Cambodia. 2004. p. 15.

[15] Prasertsan S, Krukanont P. Implications of fuel moisture content and

distribution on the fuel purchasing strategy of biomass cogeneration

power plants. Biomass & Bioenergy 2003;24:13–25.

[16] Anonymous. Woodfuel flow study of Phnom Penh, Cambodia.

Bangkok, Thailand: FAO; 1998. p. 58.

[17] Anonymous. Cambodia forest policy assessment. Washington, DC,

USA: World Bank; 1996. p. 60.

[18] Top N, Mizoue N, Kai S. Estimating forest biomass based on

permanent sample plots in relation to woodfuel consumption: a case

study in Kampong Thom Province, Cambodia. Journal of Forest

Research 2004;9:117–23.

[19] Anonymous. Cambodia: forestry statistics to 2002. Phnom Penh,

Cambodia: Department of Forestry and Wildlife (DFW) of

Cambodia; 2003. p. 97.

[20] Lic V, Shima T. Plantation and natural re-growth forests: the growth

and use by local villagers. Phnom Penh, Cambodia: Forestry

Administration of Cambodia and Japan International Cooperation

Agency; 2005. p. 78.

[21] Tewari SK, Katiyar RS, Ram B, Misra PN. Effect of age and season

of harvesting on the growth, coppicing characteristics and biomass

productivity of Leucaena leucocephala and Vitex negundo. Biomass &

Bioenergy 2004;26:229–34.

[22] Kumar BM, Kumar SS, Fisher RF. Intercropping teak with

Leucaena increases tree growth and modifies soil characteristics.

Agroforestry Systems 1998;42:81–9.

[23] Erdmann TK, Nair PKR, Kang BT. Effects of cutting frequency and

cutting height on reserve carbohydrates in Gliricidia sepium (Jacq.)

Walp. Forest Ecology & Management 1993;57:45–60.

[24] Lugo AE, Brown S, Chapman J. An analytical review of production

rates and stemwood biomass of tropical forest plantations. Forest

Ecology & Management 1988;23:179–200.

[25] Tsai LM. Studies on Acacia mangium in Kemasul Forest, Malaysia. I.

Biomass and productivity. Journal of Tropical Ecology 1988;4:

293–302.

[26] Chijoke EO. Impact on soils of fast-growing species in lowland humid

tropics. FAO Forestry Paper, vol. 21. Rome, Italy: FAO; 1980.

p. 111.

[27] Abe H, Phon P, Uon SO, Miech P. Productivity and sustainability of

biomass fuel production—case study of Meanok Forest Plantation in

Kampong Chhnang Province and Anlong Ta Mei Community

Energy Cooperative in Battambang Province. Phnom Penh, Cambo-

dia: Japan International Cooperation Agency; 2006. p. 19.

[28] PASCO Corporation. The study on the establishment of GIS base

data for The Kingdom of Cambodia (summary report). Phnom Penh,

Cambodia: Japan International Cooperation Agency; 2003. p. 59.

[29] Van Krevelen DM. Coal. New York, USA: Elsevier Scientific

Publishing; 1961. p. 416.