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Ecological Engineering 36 (2010) 1348–1354

Contents lists available at ScienceDirect

Ecological Engineering

journa l homepage: www.e lsev ier .com/ locate /eco leng

mergy analysis of cassava chips-suitable feedstock for fuel ethanol in China

ui Yang, Li Chen, Zongcheng Yan ∗, Honglin Wangchool of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, Guangdong 510640, China

r t i c l e i n f o

rticle history:eceived 25 September 2009eceived in revised form 14 April 2010

a b s t r a c t

The theory and indices of Odum’s concept of emergy are explained. The environmental and economicinputs and sustainability of cassava chips production system are evaluated by emergy methodology. The

ccepted 5 June 2010

eywords:assava chipsuel ethanol

emergy indices of cassava chips production system were calculated as follows: Tr (transformity) was6.85E + 11 sej/kg, EYR (emergy yield ratio) was 1.11, ELR (environmental loading ratio) was 1.75, EIR(emergy investment ratio) was 9.33, and ESI (emergy sustainability indice) was 0.63. The emergy indicesof four kinds of feedstock for fuel ethanol—corn, wheat, sugarcane, and cassava chips—were compared.Least solar energy was consumed when taking cassava chips as feedstock for fuel ethanol. According to theemergy indices, using cassava chips as the feedstock of fuel ethanol is helpful for sustainable development

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mergy analysis in China.

. Introduction

At present, the energy crisis and environmental pollution arewo major problems the world is facing. Therefore, developingenewable and clean energy has become the great concern of everyountry. Biofuels can positively impact socio-economic develop-ent, e.g., by alleviating poverty, creating jobs, reducing reliance

n imported oil and on increasing access to modern energy servicesUnited Nations and Foundation, 2006).

Fuel ethanol as the substitute for gasoline is helpful to ensurenergy security and improve environment quality. Fuel ethanolas a long history as an alternative transportation fuel. It wassed in Germany and France as early as 1894 by the then incip-

ent industry of internal combustion (IC) engines (Demirbas andarslioglu, 2007). Fuel ethanol has a higher octane number, 108,roader flammability limits, higher flame speeds and higher heatsf vaporization. These properties allow for a higher compressionatio and shorter burn time, which leads to theoretical efficiencydvantages over gasoline in an IC engine (Balat, 2007).

Therefore, how to evaluate sustainability of the production sys-em of fuel ethanol becomes the great concern of every country.here are many methods to evaluate fuel ethanol, such as energynalysis (Suiran and Jing, 2009a; Thu Lan et al., 2007, 2008; Cardona

lzate and Sánchez Toro, 2006; Rubo et al., 2008), economic analy-is (Suiran and Jing, 2008; Cheng et al., 2003; Krishnan et al., 2000),nvironmental evaluation (Thu Lan et al., 2007; Tom and Tim, 2007)nd exergetic evaluation (Yang et al., 2009).

∗ Corresponding author. Tel.: +86 20 87111109; fax: +86 20 87111109.E-mail address: zcyan@scut.edu.cn (Z. Yan).

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925-8574/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.ecoleng.2010.06.011

© 2010 Elsevier B.V. All rights reserved.

However, feedstocks are the major inputs in the fuel ethanolroduction process. The productivity, environmental impact, andustainability of the agriculture system of feedstock have a greatnfluence on the development of fuel ethanol. It is necessary tovaluate the planting system of feedstock for fuel ethanol.

Because most types of agriculture depend on a combination ofatural and economic inputs, it is necessary to account for both inquivalent terms when comparing the resource use of agriculturalethods (Campbell, 1998). While the value of economic contribu-

ions is routinely quantified by economic analyses, such approachesften underestimate environmental contributions to productionystems. If environmental inputs are not properly accounted forelative to economic inputs, optimum use of resources may not bechieved, and management decisions will be based on incompletenalyses (Ulgiati et al., 1994).

In energy analysis, different kinds of energy are calculated onhe common unit of joule. There are no differences between 1 J oflectricity and coal in energy analysis. In fact, 4 J of coal can producenly 1 J of electricity. Therefore, energy analysis cannot reflect theuality of energy. And free environmental inputs are usually notccounted for.

The emergy methodology was proposed by Odum in 1983. Thisethod is able to evaluate environmental and economic contri-

utions and services on a common basis of “solar energy”. As aeasure of energy used in the past, emergy (with unit emjoule)

nalysis is totally different from conventional energy (with unit

oule) analysis, which merely accounts for the remaining availablenergy at present, considers both energy quality and energy usedn the past, and therefore proves a more feasible approach to evalu-te the status and position of different energy carriers in universalnergy hierarchy (Chen et al., 2006).

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Generally speaking, ethanol can be generated from a numberf feedstocks, which are usually categorized into starch, molassesnd cellulose-based feedstock (Suiran and Jing, 2009b). In China,ood grain was taken as the main feedstock of fuel ethanol in theeginning, such as corn and wheat. However, from a long-termonsideration, taking food grain as feedstock will increase the totalost of fuel ethanol, and at the same time China has such a big pop-lation to feed that the food supply may not be enough for botheople and fuel ethanol. Hence, a number of other kinds of feed-tock have been proposed, among which cassava is one of the mostromising choices (Zhiyuan et al., 2004). Cassava is not a staple foodor the Chinese people. Using cassava as the feedstock of ethanolould not a the foodstuff crisis. And cassava is easy to be commin-ted, cooking time is short, and gelatinization temperature is low.early 2.8 t cassava chips can produce 1 t of fuel ethanol.

This paper evaluates the production system of cassava chips inhina by emergy analysis. Emergy analysis has many indices, andhese indices indicate various performance characteristics of theystem in terms of efficiency and sustainability.

. Emergy analysis of cassava chips

.1. Emergy theory and emergy indices

Emergy is defined as the sum of all inputs of available energyirectly or indirectly required by a process to provide a given prod-ct or service, when the inputs are expressed in units of the sameorm (or type) of energy, usually solar emjoules (sej) (Odum, 1996;rown and Ulgiati, 1997). Solar energy is the primary source whichould feed all processes and cycles on Earth. In other words, emergys the “energy memory” that has been used throughout a sequencef different processes going into a product. Emergy is therefore notstate function, because it considers the specific path from the ini-

ial to the present state (Pulselli et al., 2008). To derive the solarmergy of a resource or commodity, it is necessary to trace back allhe resource and energy flows which are used to produce a resourcer commodity, and express these input flows in the amount ofolar energy that went into their production (Brown and Ulgiati,002).

The ratio of the total emergy inputs to the mass or energy ofhe product gives a unit, namely specific emergy or transformityTr), in unit of sej/g or sej/J, respectively. Moreover, specific emergyan be conceived as an indicator that represents the position that aiven transformation process (and its product) occupies in the hier-rchical network of the earth’s biosphere (Odum, 1996). Throughultiplying the inputs and outputs by certain transformities, the

mergy amount of each resource, service and corresponding prod-ct can be calculated.

With the same accounting unit, the environment cost and ben-fit can be clearly analyzed through a series of emergy-basedatios and indices. Emergy analysis has many indices, and thesendices indicate various performance characteristics of the sys-em in terms of efficiency and sustainability. In order to make themergy indices clear, an emergy consumption figure of a system isiven in Fig. 1. There are three categories of inputs emergy flows: Rs renewable environmental resources, N as non-renewable envi-onmental resources and F as the purchased resources. The R and

flows provided by the environment are economically free. Theconomic inputs, F, are provided by the market and related to

uxes that are accounted by the economy. F can also be divided

nto two categories, renewable purchased (FR) and non-renewableurchased (FN). The outputs, Y, may include products, services andlso emissions that are released to the environment (Giannetti etl., 2006). There are many emergy indices for better evaluation of

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Fig. 1. Inputs and outputs emergy flows of the system.

he concerned system and indication of various performances of theystem in terms of ecological efficiency and sustainability (Zhou etl., 2009).

EYR. The emergy yield ratio (EYR) is the ratio of the output (Y)mergy to the purchased (F) emergy. This ratio is a measure of thebility of the system to exploit and make local resources availabley investing in outside resources.

ELR. The environmental loading ratio (ELR) is the ratio ofon-renewable purchased (FN) emergy plus non-renewable envi-onmental (N) emergy to renewable purchased (FR) emergy plusenewable environmental (R) emergy. This index is used to eval-ate how much “pressure” is placed on the environment by theystem. ELR values less than 2 indicate a relatively low impact onhe environment (or processes that could use a large area of a localnvironment to ‘dilute the impact’); values between 2 and 10 meanhat the system caused a moderate impact; up to 10 are indicative ofelatively concentrated environmental impact (Brown and Ulgiati,004).

EIR. The emergy investment ratio (EIR) is the ratio of themergy fed back by the economy to “natural” (renewable and non-enewable) environmental emergy inputs.

ESI. Emergy sustainability index (ESI) is the ratio of the emergyield ratio EYR to the environmental loading ratio ELR. ESI’s of lesshan 1 appear to be indicative of products or processes that areot sustainable in the long run and those with ratios greater thanindicative of products and processes that are sustainable contri-utions to the economy. Medium level of sustainability seems toe characterized by ESI’s between 1.0 and 5.0, while processes androducts with higher ESI’s have accordingly greater sustainabilityBrown and Ulgiati, 2002).

The emergy/dollar ratio is the ratio of total emergy use of atate or country to gross national product (GNP) for the nationalconomy. It can be used to convert money payments into emergynits.

.2. Cassava-suitable feedstock for fuel ethanol

Cassava grew only in South American originally, but itas introduced to China 200 years ago. The planting areas

f cassava were 600,000 ha, and the yields of cassava were1 million t in China in 2005. It is estimated that the plant-

ng areas will increase to 1 million ha in 2015 (http://www.opo100.com/e/DoPrint/?classid=731&id=5174). Cassava grows

ainly in Guangxi, Guangdong, Hainan, Yunnan, Fujian provincesn China. The growth period of cassava is usually 8–12 months inhe south of China.

Cassava is usually used to produce amylum, feedingstuff, andthanol. As feedstock for fuel ethanol, cassava has two advantages

1350 H. Yang et al. / Ecological Engineering 36 (2010) 1348–1354

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The emergy proportion of each flow to the whole inputs of cas-sava chips production system is shown in Fig. 3. Nitrogen and labor

Fig. 2. Energy flow diagram o

ver other feedstocks. First, cassava is a shrubby tropical plant,idely grown for its large, tuberous, starchy roots, especially onarginal land where rice, wheat, corn, sugarcane and other agri-

ultural crops cannot grow well (Zhiyuan et al., 2004). Second, usingassava as the feedstock of ethanol would not cause the foodstuffrisis as would corn and wheat. Cassava is easy to be comminuted,ooking time is short, and gelatinization temperature is low. There-ore, cassava is suitable feedstock for fuel ethanol. Fresh cassava iserishable, and it is usually made into cassava chips to reserve andse. The production system of cassava chips includes field prepara-ion and plough, sowing, fertilization, weeding, harvesting, pillingnd slicing, baking and packing.

.3. Study site

Cassava grows in Danzhou City, Hainan Province. Danzhou is aypical tropic zone, tropical monsoon climate conditions. The aver-ge annual temperature is 23 ◦C, solar radiation is approximately10 kcal/cm2, and the yearly precipitation is about 1600 mm. Theield of cassava studied is 40 t/hm2. The data of every input flow ofassava system are obtained from the Chinese academy of tropicalgricultural sciences.

.4. Emergy evaluation procedure of cassava chips

The first step in the application of emergy methodology iso construct system diagrams to categorize all components intoenewable or non-renewable, environmental or purchased. A sys-em’s diagram is drawn using the symbols of the energy languagef systems ecology (Odum, 1996) to graphically represent sys-em components, emergy sources and flows and the circulation of

oney through the system. The components and subsystems areonnected with arrows that indicate energy, feedstock and infor-ation flows (Odum, 1996). The energy flow diagram of cassava

hips production system is shown in Fig. 2.

The second step for the emergy analysis is to make emergy eval-

ation tabulation, placing the numerical value and the units of eachow mentioned in the diagram. To obtain the emergy value of each

nput, the raw data of input such as joules, grams or dollars areultiplied by their transformities.

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ava chips production system

Finally, various emergy-based indicators are calculated. Theco-efficiency, environmental impact and the sustainability of thetudied system are assessed.

. Results

As the seeds of cassava, cassava stem cuttings are a part of thenput flows. The transformity of cassava stem cuttings is unknown,t is necessary to make emergy analysis of cassava cultivation sys-em to calculate its transformity first. Table 1 shows the emergynalysis of cassava cultivation system. The mass ratio of fresh cas-ava to stem is 1:1, and the input emergy to produce fresh cassavand stem are the same, so fresh cassava and stem have the sameransformity which is represented by X. Through calculation, it isnown that the transformity of fresh cassava and cassava stem areoth 2.10E + 11 sej/kg. Emergy analysis of cassava chips production

ig. 3. The emergy proportion of each flow to the whole inputs of cassava chipsroduction system.

H. Yang et al. / Ecological Engineering 36 (2010) 1348–1354 1351

Table 1Emergy analysis of cassava cultivation system.

Item (unit) Data (unit/(c hm2)) Transformity (sej/unit) Emergy (sej/(c hm2))

RSun radiation (J) 2.68E + 13 1 2.68E + 13Rain chemical potential (J) 2.63E + 10 3.05E + 04a 8.04E + 14Rain geopotential (J) 1.05E + 10 4.70E + 04a 4.91E + 14Wind (J) 2.07E + 10 2.45E + 03a 5.07E + 13Sum of R 8.04E + 14

NNet topsoil loss (J) 1.32E + 09 7.40E + 04b 9.76E + 13

FR

Stem cuttings (kg) 750 X 750XLabor (man h) 1000 1.1E + 12c 1.10E + 15Sum of FR 750X + 1.10E + 15

FN

Nitrogen (kg) 150 2.40E + 13d 3.6E + 15Phosphate (kg) 75 2.02E + 13d 1.515E + 15Potash (kg) 225 1.74E + 12d 3.915E + 14Herbicides (kg) 15 1.48E + 13d 2.22E + 14Ploughing ($) 171 3.00E + 12 5.14E + 14Sum of FN 6.24E + 15Sum of inputs 750X + 8.24E + 15

YCassava (kg) 40,000 X 750X + 8.24E + 15Stem 40,000 X 750X + 8.24E + 15

Cassava variety: ZM9057. c stands for growth cycle of cassava, here took 10 months. Rain and wind are considered to be co-products of sunlight; to avoid dou-ble counting among the inputs of renewable environmental resources, only the item with the highest value is added to the total amount of emergy (Odum, 1996).Emergy/dollar ratio of China was 3.46E + 12 sej/$ in 2004 (Wang and Zhang, 2004), considering the impact of economic development, here took 3.0E + 12 sej/$.40,000X = 750X + 8.24E + 15X = 2.10E + 11 sej/kg.

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Odum et al. (2000).b Brown and Bardi (2001).c Ortega (2000).d Brandt-Williams (2002).

able 2mergy analysis of cassava chips.

Item (unit) Data (unit/a)

RSun radiation (J) 2.68E + 13Rain chemical potential (J) 2.63E + 10Rain geopotential (J) 1.05E + 10Wind (J) 2.07E + 10Sum of R

NNet topsoil loss (J) 1.32E + 09

FR

Stem cuttings (kg) 750Labor (man h) 2200Hydroelectricity (electricity × 30%) (kJ) 3288Sum of FR

FN

Nitrogen (kg) 150Phosphate (kg) 75Potash (kg) 225Herbicides (kg) 15Diesel (kJ) 1,500,787Coal electricity (electricity × 70%) (kJ) 7673Sum of FN

Sum of inputs

YCassava chips (kg) 13,600

he electricity used is recalculated to primary energy for an average south China electricia Odum et al. (2000).b Brown and Bardi (2001).c Ortega (2000).d Brown and Ulgiati (2002).e Brandt-Williams (2002).f Odum (1996).

Transformity (sej/unit) Emergy (sej/a)

1 2.68E + 133.05E + 04a 8.04E + 144.70E + 04a 4.91E + 142.45E + 03a 5.07E + 13

8.04E + 14

7.40E + 04b 9.76E + 13

2.10E + 11 1.58E + 141.1E + 12c 2.42E + 156.23E + 07d 2.05E + 11

2.58E + 15

2.40E + 13e 3.60E + 152.02E + 13e 1.52E + 151.74E + 12e 3.92E + 141.48E + 13e 2.22E + 146.60E + 07f 9.91E + 131.71E + 08d 1.31E + 12

5.83E + 159.31E + 15

6.85E + 11 9.31E + 15

ty production system, which is based on 30% hydropower and 70% coal fuels.

1352 H. Yang et al. / Ecological Engineering 36 (2010) 1348–1354

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Table 4Comparison of emergy indices of four kinds of feedstock for fuel ethanol.

Emergy indices Corn Sugarcane Wheat Cassava chips

Tr (sej/kg) 1.4E + 12 1.96E + 11 1.82E + 12 6.85E + 11EYR 1.07 1.62 1.32 1.11ELR 18.83 3.27 3.47 1.75EIR 13.8 1.61 3.11 9.33ESI 0.06 0.50 0.38 0.63

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ig. 4. The emergy proportion of four categories of flows to the whole inputs ofassava chips production system.

re two major emergy flows. Nitrogen is responsible for 38.68%f all emergy flows in the cassava chips production system. Themergy of labor accounts for 26% of all inputs. In Fig. 4, non-enewable purchased emergy accounts for 62.62% of the wholenput emergy. The emergy from the environment only accountsor less than 10% of the whole inputs.

Various emergy-based indicators of cassava chips are shown inable 3. The transformity of cassava chips is 6.85E + 11 sej/kg, EYRs 1.11, ELR is 1.75, EIR is 9.33, ESI is 0.63.

. Discussions

As shown in Fig. 3, nitrogen is responsible for 38.68% of allmergy flows in the cassava chips production system. Because theransformity of nitrogen is the highest in all of the input flows, farm

anure substitutes for nitrogen partially, the total emergy inputnd the transformity of cassava chips will decrease. Moreover, farmanure is renewable resource, so using more farm manure is good

or sustainable development. The emergy of labor accounts for 26%f all inputs. The mechanization level of cassava cultivation is lown China. In Fig. 4, non-renewable purchased emergy accounts for2.62% of the whole input emergy. The emergy from the envi-onment only accounts for less than 10% of the whole inputs. Itndicates that the system depends less on the environment.

Various emergy-based indicators of cassava chips are shownn Table 3. The transformity of cassava chips is 6.85E + 11 sej/kg,

hich is related with input emergy and the yield of the cassava. Inrder to decrease the transformity, it is necessary to cultivate bet-er varieties, choose good stem cuttings, and improve the plantingechnology to increase the yield, use less amount of N, P, K fertilizernd more amount of farm manure to decrease the emergy input.mergy indexes of corn (Jay et al., 2006), sugarcane (Simone andadia, 1996), wheat (Xiaobin et al., 2008), and cassava chips areompared in Table 4. The transformity of cassava chips is lowerhan corn and wheat, and higher than sugarcane.

EYR of cassava chips is 1.11, which shows the emergy fromnvironment is little. Sugarcane has the highest EYR of 1.62. Sougarcane has the highest exploitation of environmental resources,

epends least on purchased resources.

The more non-renewable resources consumed in the system,he heavier the loading on the environment. Excessive loading onnvironment by humans might result in severe degradation in eco-

able 3mergy indices of cassava chips production system.

Emergy indices Tr EYR ELR EIR ESI

Data 6.85E + 11 sej/kg 1.11 1.75 9.33 0.63

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ig. 5. The solar emjoules of different feedstock to produce 1 t of fuel ethanol.

ogical function of a system (Brown and Ulgiati, 1997). Since theassava chips production system has a relatively low technologicalevel, the ELR of cassava chips is the lowest, as presented in Table 4.t means that there is plenty of room for further development fromhe mainstream point of view of modern industrialized agriculture.

EIR of cassava chips is 9.33, which is higher than sugarcane andheat, and lower than corn. Therefore corn needs the most pur-

hased emergy in the production system. ESI of cassava chips is.63, which is the highest in four kinds of feedstock. So the cassavahips system is more sustainable than the other three.

If 1 t fuel ethanol is produced, it will consume 3.2 t corn,6 t sugarcane, 3.28 t wheat or 2.8 t cassava chips. According tohe transformity of different feedstocks (shown in Table 4), corn.48E + 15 sej, sugarcane 3.14E + 15 sej, wheat 5.97E + 15 sej or cas-ava chips 1.88E + 15 sej are needed to produce 1 t fuel ethanolshown in Fig. 5). So it consumes the least solar energy when takingassava chips as feedstock to produce fuel ethanol.

. Conclusion

By quantifying natural and man-made, as well as renewablend non-renewable inputs to cassava chips production system oncommon basis, emergy analysis facilitates comparisons across

he system and can identify manipulations to achieve greater sus-ainability. Emergy is an appropriate methodology to evaluatehis system, because each type of flows, such as environmentalesources, monetary and labor flows could be taken into accountor the evaluation.

38.68% of all emergy was invested by nitrogen in cassavahips production system. The dependence on nitrogen reduces theraction of renewable energy and increases environmental degra-ation, making the system less sustainable relative to systems moreependent on renewable energies. Finding methods to reduce theon-renewable inputs has great potential to increase the sustain-bility and decrease the environmental loading of the system.

The transformity of cassava chips is 6.85E + 11 sej/kg, which isower than corn and wheat, and higher than sugarcane. In order

o decrease the transformity, cultivate better varieties of cassava,hoose good stem cuttings, and improve the planting technologyo increase the yield per hectare, use more farm manure and less, P, and K fertilizer to decrease the input emergy. The solar energy

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f different feedstock to produce 1 t of fuel ethanol is as follows:orn 4.48E + 15 sej, sugarcane 3.14E + 15 sej, wheat 5.97E + 15 sej,assava chips 1.88E + 15 sej. So it consumes the least solar energyhen taking cassava chips as the feedstock for fuel ethanol. ELR of

assava chips is 1.75, which is the lowest in four kinds of feedstockor fuel ethanol. So it has a low impact on the environment. ESI ofassava chips is 0.63, which is the highest in four kinds of feedstock.o cassava chips system is more sustainable than the other threeystems.

If taking corn or wheat as feedstock to produce fuel ethanol con-inually it may cause food crisis. Sugarcane is mainly used to makeugar. Taking sugarcane to produce fuel ethanol will influence theroduction of sugar.

All in all, in China, use of cassava chips as the feedstock of fuelthanol is helpful for sustainable development, and adapts to theiving needs of humans.

cknowledgements

This study has been supported by Guangdong Provincialaboratory of Green Chemical Technology, China and Thailandnternational Cooperation Program (Grant No. 18509J), and Guang-ong Provincial Science and Technology Development ProgramGrant No. 2006A50102002).

ppendix A.

1. Sun radiation = A × Ic × absorbed percentageA (surface area) = 10,000 m2

I (average yearly solar radiation) = 110 kcal/(cm2 a) = 4.6E + 09 J/m2 a)

Ic (solar radiation per the growth cycle of cas-ava) = I × 10/12 (a/c) = 3.83E + 09 J/(m2 c)

Absorbed percentage = 70%Sun radiation = 10,000 m2 × 3.83E + 09 J/(m2 c) × 0.7 = 2.68E +

3 J/c.2. Rain chemical potential energy = A × Pc × D × �G�G (Gibbs free energy) = 4.94 J/gP = yearly precipitation × (1 − evapotranspiration rate

0%) = 1600 mm/year × (1 − 0.6) = 0.64 m/yearPc (precipitation per the growth cycle of cas-

ava) = P × 10/12 year/c = 0.533 m/cD (water density) = 1E6 g/m3

Rain chemical potential energy = E + 0.4 m2 × 0.533 m/year ×E6 g/m3 × 4.94 J/g = 2.63E + 10 J/c.

Rain geopotential = A × E × pc × D × gE (average elevation) = 80 mpc (precipitation) = 1600 mm/year × 10/12 year/c = 1.333 m/cg (Gravity) = 9.8 N/kgRain geopotential = E + 0.4 m2 × 80 m/year × 1.333 m/c × 1E +

3 kg/m3 × 9.8 N/kg = 1.05E + 10 J/c3. Wind kinetic = r × c(vg)3G × Ar (air density) = 1.23 kg/m3

c (drag coefficient) = 1E − 3v (average annual wind velocity) = 2.4 m/svg (geostropic wind) = 10/6 vG (Wind gradient) = 3.154E + 7 s/yearWind kinetic = 1.23 kg/m3 × 1E − 3 × (2.4 m/s × 10/6)3 × 3.154E

7 s/year × 10/12 year/c × 10,000 m2 = 2.07E + 10 J/c4. Net topsoil loss = A × E × O × energy of organic soil

E (erosion rate) = 350 g/(m2 year)O (organic soil percentage) = 2%Energy of organic soil = 5.4E + 6 kcal/t × 4186 J/kcal = 2.26E + 10 J/tNet topsoil loss = E + 4 m2 × 350 g/(m2 year) × 10/12 year/c ×

% × 2.26E + 10 J/t = 1.32E + 9 J/c

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ring 36 (2010) 1348–1354 1353

eferences

alat, M., 2007. Global bio-fuel processing and production trends. Energy Explor.Exploit. 25, 195–218.

randt-Williams, S., 2002. Emergy of Florida Agriculture. Folio #4. Handbook ofEmergy Evaluation. Center for Environmental Policy, University of Florida,Gainesville, USA.

rown, M.T., Bardi, E., 2001. Folio #3: Emergy of Global Processes. Handbook ofEmergy Evaluation: A Compendium of Data for Emergy Computation Issuedin a Series of Folios. Center for Environmental Policy, University of Florida,Gainesville, USA.

rown, M.T., Ulgiati, S., 1997. Emergy-based indices and ratios to evaluate sustain-ability: monitoring economies and technology toward environmentally soundinnovation. Ecol. Eng. 9, 51–69.

rown, M.T., Ulgiati, S., 2002. Emergy evaluations and environmental loading ofelectricity production systems. J. Cleaner Prod. 10 (4), 321–334.

rown, M.T., Ulgiati, S., 2004. Emergy analysis and environmental accounting. Ency-clopedia Energy 2, 329–354.

ardona Alzate, C.A., Sánchez Toro, O.J., 2006. Energy consumption analysis of inte-grated flowsheets for production of fuel ethanol from lignocellulosic biomass.Energy 31 (13), 2447–2459.

ampbell, D., 1998. Emergy analysis of human carrying capacity and regional sus-tainability: an example using the state of Maine. Environ. Monit. Assess. 51,531–569.

hen, G.Q., Jiang, M.M., Chen, B., Yang, Z.F., Lin, C., 2006. Emergy analysis of Chineseagriculture. Agric. Ecosyst. Environ. 115, 161–173.

heng, Z., Weijian, H., Xuedong, J., Gengqiang, P., Chengtao, W., 2003. Life cycleeconomic analysis of fuel ethanol derived from cassava in southwest China.Renew. Sust. Energy Rev. 7 (4), 353–366.

emirbas, A., Karslioglu, S., 2007. Biodiesel production facilities from vegetable oilsand animal fats. Energy Sources Part A 29 (1), 33–41.

iannetti, B.F., Barrella, F.A., Almeida, C.M.V.B., 2006. A combined tool for envi-ronmental scientists and decision makers: ternary diagrams and emergyaccounting. J. Cleaner Prod. 14 (2), 201–210.

ay, F.M., Stewart, A.W.D., Erick, P., Michele, S., Samuel, L.-T., 2006. Emergy evalu-ation of the performance and sustainability of three agricultural systems withdifferent scales and management. Agric., Ecosyst. Environ. 115 (1–4), 128–140.

rishnan, M.S., Taylor, F., Davison, B.H., Nghiem, N.P., 2000. Economic analysis of fuelethanol production from corn starch using fluidized-bed bioreactors. Bioresour.Technol. 75 (2), 99–105.

dum, H.T., 1996. Environmental Accounting: Emergy and environmental DecisionMaking. John Wiley & Sons, New York.

dum, H.T., Brown, M.T., Williams, S.B., 2000. Folio #1: Introduction and GlobalBudget. Handbook of Emergy Evaluation: A Compendium of Data for EmergyComputation Issued in a Series of Folios. Center for Environmental Policy, Uni-versity of Florida, Gainesville, USA.

rtega, E., 2000. Handbook of Emergy Calculations. Laboratório de EngenhariaEcológica e Informática Aplicada, Sao Paulo, Brazil.

ulselli, R.M., Simoncini, E., Ridolfi, R., Bastianoni, S., 2008. Specific emergy of cementand concrete: an energy-based appraisal of building materials and their trans-port. Ecol. Indicators 8 (5), 647–656.

ang, Q., Chen, B., Xi, J., He, Y.F., Chen, G.Q., 2009. Exergetic evaluation of corn-ethanol production in China. Commun. Nonlinear Sci. Numer. Simul. 14 (5),2450–2461.

ubo, L., Chengtao, W., Cheng, Z., Du, D., Gengqiang, P., 2008. Life cycle inventoryand energy analysis of cassava-based Fuel ethanol in China. J. Cleaner Prod. 16(3), 374–384.

imone, B, Nadia, M., 1996. Ethanol production from biomass: analysis of processefficiency and sustainability. Biomass Bioenergy 11 (5), 411–418.

uiran, Y., Jing, T., 2008. Life cycle simulation-based economic and risk assessment ofbiomass-based fuel ethanol (BFE) projects in different feedstock planting areas.Energy 33 (3), 375–384.

uiran, Y, Jing, T., 2009a. Energy efficiency assessment by life cycle simulation ofcassava-based fuel ethanol for automotive use in Chinese Guangxi context.Energy 34 (1), 22–31.

uiran, Y., Jing, T., 2009b. Simulation based life cycle assessment of airborne emis-sions of biomass-based ethanol products from different feedstock planting areasin China. J. Cleaner Prod. 17 (5), 501–506.

hu Lan, T.N., Shabbir, H.G., Savitri, G., 2007. Energy balance and GHG-abatementcost of cassava utilization for fuel ethanol in Thailand. Energy Policy 35 (9),4585–4596.

hu Lan, T.N., Shabbir, H.G., Savitri, G., 2008. Full chain energy analysis of fuel ethanolfrom cane molasses in Thailand. Appl. Energy 85 (8), 722–734.

om, B., Tim, G., 2007. Life-cycle analysis of emissions from fuel ethanol and blendsin Australian heavy and light vehicles. J. Cleaner Prod. 15 (8–9), 833–837.

lgiati, S., Odum, H.T., Bastianoni, S., 1994. Emergy use, environmental loading andsustainability. An emergy analysis of Italy. Ecol. Model. 73, 215–268.

nited Nations and Foundation, 2006. The United Nations biofuels initiative. United

Nations, New York, Available at: www.unfoundation.orgS.

ang, L., Zhang, J., 2004. Emergy evaluation of power plant eco-industrial park.Chin. J. Appl. Ecol. 15 (6), 1047–1050.

iaobin, D., Sergio, U., Maochao, Y., Xinshi, Z., Wangsheng, G., 2008. Energy andemergy evaluation of bioethanol production from wheat in Henan Province.Chin. Energy Policy 36 (10), 3882–3892.

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Z

354 H. Yang et al. / Ecological Enginee

hiyuan, H., Fang, F., DaoFeng, B., Gengqiang, P., Chengtao, W., 2004. Net energyCO2 emission, and life-cycle cost assessment of cassava-based ethanol as analternative automotive fuel in China. Appl. Energy 78 (3), 247–256.

Z

ring 36 (2010) 1348–1354

hou, J.B., Jiang, M.M., Chen, B., Chen, G.Q., 2009. Emergy evaluations for con-structed wetland and conventional wastewater treatments. Commun. NonlinearSci. Numer. Simul. 14 (4), 1781–1789.