Distribution of E3

Blended E3 arrives at petrol station in Taipei. This delivered E3 is distributed customers in Taipei.

In this subsystem electricity used in petrol stations and amount of E3 provided to customers in Taipei are parameters of input. Output is material outflow of fugitive loss in E3 and energy loss from electricity used in petrol stations and E3 distributed to customers.

3.2.6 Vehicle Use of E3

Distributed E3 at subsystem of Distribution was assumed to be an input in this subsystem. Output was the energy loss of consuming E3 and material loss of pollutants to the air.

3.3 Life Cycle Impact Assessment Method

As one of life cycle impact assessment methodology, IMPACT 2002+ is and attractive implementation combined midpoint/damage approach. Jolliet et al, 2003 proposed a feasible implementation of a combined midpoint/damage approach that link all types of life cycle inventory results through 14 midpoint categories to four damage categories as shown in Figure 3.5. IMPACT 2002+ has developed new concepts and methods especially for the comparative assessment of human toxicity and ecotoxicity.

For human damage factors were calculated for carcinogens and non-carcinogens that employ intake fractions, best estimates of dose-response slope factors as well as severities. Both human toxicity and ecotoxicity effect factors are reflected from mean responses rather than the assumptions.

Figure 3.5 Overall scheme of the IMPACT 2002+ framework, linking LCI results via the midpoint categories to damage categories, adapted from Joliet (2003)

Mineral extraction

As a scope of this assessment, E3 gasoline literatures ethanol from sugarcane in purpose of a transportation fuel will be assessed. Past literatures published in recent years and local data will be assessed then applied on the case in Taiwan. The final goal of this LCA is to model all potential impacts to the environment and energy issues of bioethanol. Air emissions will be analyzed followed by the methodology proposed by Bernesson et al (2004). Considered emissions are CO2, CO, HC, methane, CH4, NOx (nitrous oxides), SOx (sulphur oxides), NH3, N2O and HCl. These emissions will be classified in to different environmental impact categories: global warming potential, acidification potential, eutrophication potential, carcinogens, respiratory organics and inorganic, ionizing radiation, ozone layer depletion, ecotoxicity and land occupation.

These impact categories are able to be analyzed by LCA software like SIMAPRO.

3.4 Life Cycle Exergy Analysis of Biofuel

Dewulf et al (2005) has stated that the cumulative exergy values were calculated by tracking back input materials to the raw materials extracted out of the ecosystem to deliver them. The whole production of sugarcane and transport of raw materials and ethanol are therefore accounted. Values of exergy, cumulative exergy consumption (CExC) and cumulative degree of perfection (CDP) are already given by Szargut, (1987), Szargut et al, (1988), Tsatsaronis & Moran, (1997), Mulder, (2002) and Dewulf et al., (2005). These values are adapted into this study.

Assessment of a boundary requires calculating total exergy and cumulative exergy consumptions. These parameters were required to calculate exergy breeding factor (BFex) and non-renewable exergy ratio.

Total Exergy = Quantity × Exergy (3.4.1) CExC_total = Quantity × CExC (3.4.2)

The CExC-index expresses the sum of exergy values of natural resources fraction to the system delivered in all the link of the chain of production processes, per unit of the product under consideration. Dewulf et al., 2005 analyzed the CExC-index adapting the method of Szargut, 1987 by correcting the exergy consumption in three production chain. The reference state of Szargut, (1987) was chosen with its reference temperature (298 K), pressure (1 atm), and composition.

In this study, it adapted from Szargut (1987) when the reference state was not available by calculating from lower heating value-to-exergy rations. Solar irradiations were calculated by taking into account the geographical position of the different production sites. This study however assumes the solar irradiation is the same in any geographical position. Functional unit of the land is already decided therefore the solar

radiation was considered to be the same in Taiwan and Brazil. Exergy of solar radiation can be calculated from the exergy-to-energy ratio being 0.933 (Szargut, 1987).

With respect to system boundaries, the whole production chain, including extraction, transport and storage of raw materials and the pesticides were taken into account.

Firstly, exergy of the bagasse and sugarcane was calculated. For the determination of bagasse exergy, an exergy value has given by Patzek and Pimentel (2005) in Table 3.18. The data has been directly adopted. Patzek and Pimentel (2005) stated the bagasse at the reference environment conditions, its total exergy is equal to its chemical exergy.

The following composition of the bagasse in mass and dry base was assumed:

C(47.0%), H(6.5%), O(44.0%) and Ash(2.5%) (Patzek and Pimentel, 2007). The exergy of the sugarcane was assumed from 1 metric ton of harvest sugarcane stem (Patzek and Pimentel, 2005). It is assumed on the dry basis of 140 kg bagasse, 160 kg of fermentable sugars and starch and 92 kg of attached tops and leaves, 188 kg detached leaves and 608 kg of water (Figure 3.6).

Figure 3.6. The mass fraction of sugarcane structure

Exergy value of bagasse and trash were referred to Patzek and Pimentel (2005) (Table 3.4)

Table 3.4 Exergy of bagasse and attached trash.

Item Exergy value Unit

Dry bagasse exergy 179.9 GJ/ha-yr

Dry attached trash exergy 47.5 GJ/ha-yr

Exergy analysis was conducted and the method used in here is adapted from Szargut, (1987) and Dewulf et al., (2005). The same system boundary from LCA was applied in this section. The functional unit used is kg of sugarcane or ethanol to the hectare of land use. Resource use is quantified and also the data was adapted from Szargut (1987) and Dewulf et al., (2005) then the quantity of each parameter was adapted from the LCA inventory data.

3.4.1 Exergy analysis of E3 use

Dincer (2000) defined exergy as the maximum theoretical work that can be obtained from a system as it comes to equilibrium with a reference environment. To improve energy source utilization by determining the order of exergy destructions and losses in the processes and components of the system and then by reducing them, the exergy analysis of thermal system is performed. In the exergy calculation it is assumed by Canakcki and Hosoz (2006) and Sayin et al., (2007) that the reference environment has a temperature (T₀) of 298.15 K and a pressure (P₀) of 1 atm. The reference environment is considered a mixture of perfect gases with the following composition of a molar basis: N₂, 75.67%: O₂, 20.35%; CO₂, 0.03%: H₂O, 3.12%: other, 0.83%.

The specific flow exergy of a fluid stream can be found as

ch

where h and s denote the specific enthalpy and entropy of the fluid, respectively while h₀ and s₀ stand for the corresponding values of these properties when the fluid comes to equilibrium with the reference environment.

The following expression on a unit mass basis can evaluate the specific chemical exergies of liquid fuels (Kotas, 1995)

e^ch_F = [1.0401 + 0.1728

where h, c, o, and s are the mass fractions of H, C, O, and S, respectively. The chemical

exergies of the fuels were calculated using the equation (3.4.1.3) and the table adapted from Sayin et al. (2007).

After calculating all the formulas, Sayin et al., (2007) showed the result as Table 3.5.

Table 3.5 Properties of the fuel

Research octane number 95

Typical formula C6.97H14.02

Average molecular weight (kg kmol_1) 97.842 Lower heating value (kJ kg_1) 43 961 Specific exergy (kJ kg_1) 47 011 (calculated from Equation (3.4.1.3) by

Sayin et al., 2007)

After calculating all the total exergy and cumulative exergy consumption, the production manners can be assessed in terms of exergy breeding (BFex). BFex assesses how much renewable resources are bred from nonrenewable resources. In order to calculate it, renewable inputs have to be subtracted from the total input. In this study solar radiation is considered as renewable exergy. However the solar radiation value is quite high and assumed to be overwhelming the system when compare to the other inputs fertilizers. Concept of this exergy study is defining renewable and non-renewable exergy. Furthermore, there is no reason that the solar radiation value to be neglected as renewable exergy and cumulative exergy consumption even the value will be extremely high. Biofuel production assessment of exergy study must be consuming higher amount of non-renewable energy. Therefore at the final stage, it was assumed that the solar radiation exergy value will be depleted at the end of the system. Below formulas are the BFex and overall BFex stated by Dewulf et al., 2005. BFex was calculated by dividing the amount of biofuel delivered by allocated non-renewable resources consumed in the agricultural and industrial biofuel production:

Breeding Factor (BF) =

Overall BFex was calculated by dividing biofuel exergy amount by all non-renewable resources consumed in the overall industrial metabolism as follows:

Overall Breeding factor (overall BF) =

metabolism

Chapter 4 Results and Discussion 4.1 Environmental Performance

Environmental performance of E3 gasoline in Scenario 1 and 2 was discussed in this section. Results calculated by SimaPro 7.1 were also discussed in this section.

Environmental impact of sugarcane to produce ethanol, industrial production of ethanol, and use of E3 gasoline of use were analyzed. The environmental performance of E3 gasoline in Scenario 1 and 2 is only distinct in these stages, namely agricultural activities, industrial ethanol production and transportation.

4.1.1 Agriculture 4.1.1.1 Scenario 1 1. Material inflow (1) Rainfall

Amount of rainfall into subsystem of agriculture was assessed. According to the US Library of Congress: Climate, the amount of averaged rainfall in Brazil per year is 1500 mm/year (US Library of Congress: Climate, http://countrystudies.us/brazil/23/htm) Total amount of rainfall input = (density of rain water) × (rainfall/area/year) × area × time

= 10³ kg/m³ × 1500 yr

mm ×468.75 hectares ×

hectares m² 10000

× mm

m 103

1

= 7.03 × 10⁹kg/yr (4.1.1.1)

(2) Pesticide

The amount of insecticide and herbicides used for agriculture of sugarcane in Brazil is assessed in this section. Data is directly adapted from de Oliveira (2005).

According to de Oliveira (2005), insecticides used for sugarcane production were 0.5 kg

The amount of herbicides into agriculture subsystem was calculated.

Herbicides used for production of sugarcane were 3.0kg per hectare according to de Oliviera (2005). In this study, 468.75 ha were used as calculation basis therefore:

ha

According to de Oliveira (2005), fertilizer applied the farm land was 217 kg/ha. Within this amount fertilizer use, the amount of nitrogen used was 65 kg/ha, then 52 kg of P₂O₅ and 100 kg of K2O.

According to de Oliveira (2005) sugarcane seed used per hectare was 215 kg.

This is the amount of sugarcane seed required per hectare.

Calculating the total amount of sugarcane bud to produce 1.0 × 10⁸ L of E3 is:

ha

bud sugarcane kg

215 × 468.75 ha = 1.01 × 10⁵ kg sugarcane bud (4.1.1.5)

According to de Oliviera (2005), the energy consumption per hectare of sugarcane bud was 3.35 GJ/ha.

(6) Diesel

For agricultural activity, the used amount of diesel is 600 L per hectare (de Oliveira, 2005). Converting this amount :

468.75 ha × ha

L

600 = 2.81 × 10⁵ L diesel/year (4.1.1.6)

(7) Lime

According to de Oliveira (2005), amount of lime used per hectare was 616 kg.

468.75 ha × ha

kg

616 = 2.89 × 10⁵ kg (4.1.1.7)

2. Energy Loss

Energy outflow at agricultural stage estimated in fuels considered to be energy loss.

This is calculated by:

Amount of water contained in soil is calculated by assumption. Intensity of rainfall in Brazil is 1500 mm. Runoff coefficient was assumed 0.1 as sandy soil with 2% slope.

0.1 × 1500 mm × 468.75 ha ×

ha m² 10000

= 7.03 ×10⁸ m³ (4.1.1.9)

(2) CO2

Amount of CO2 emitted from diesel use was calculated. 0.284 kg CO2/kL of CO2

emission factors was adopted from Daishou (2006).

2.81 × 10⁵L diesel/year × 0.284 kg CO2/kL = 7.98 × 10⁴ kg CO2/year (4.1.1.10)

It should be noted that soil loss would not be count based on the consideration of little amount of soil was lost during sugarcane production.

(3) Sugarcane

According to the calculation basis in this study, amount of sugarcane required was given. The sugarcane production was 3.30 × 10⁴ ton

4.1.1.2. Scenario 2

Inputs of material and energy are referred to the data from Omette et al. (2004).

Subsystem 1, have four subsystems in this system. Amount of material: water, pesticide and sugarcane; fuels and labor are examined based on local data. Subsystem 1 has outputs of energy loss, material outflow and sugarcane.

1. Material inflow (1) Rainfall

According to the Central Weather Bureau, the amount of averaged rain water in Taiwan per year is 2400 mm/year (Central Weather Bureau, http://www.cwb.gov.tw/) Total amount of rainfall input = (density of rain water) ×(rainfall/area/year) × area × time

= 10³ kg/m³ × 2400 used because the soil condition and the land use.

Therefore, the total amount of pesticides used for the 465.75 ha of a sugarcane field is:

yr

②. Herbicides used for production of sugarcane were 3.0kg per hectare according to de Oliviera (2005). 0.80 GJ per hectare of energy is used. With the same

Amount of fertilizer used on 268.75 ha land in Taiwan was calculated. According to Taiwan Sugar Corporation (1999), fertilizer applied to per hectare of farm land was 684 kg/ha from 1989 to 1999. Within that amount Nitrogen was117 kg/ha, then 19.45 kg of P2O5 and 40 kg of K2O (Table. 4.1).

Table 4.1 Fertilizers used for sugarcane field kg/ha (data provided by Taiwan Sugar Corporation, Taiwan sugar Statistics 1999)

Year Fertilizer Contents per ha

N P2O3 K2O

According to Taiwan Sugar Corporation (1999) averaged planted area for sugarcane was 53,305 hectare (Table. 4.2). The estimation used in here is assumed that the sugarcane is planted for sugar production cane rather than for eating fresh. Then sugarcane production to the harvested area was 10,252 ha/year, yield of 63,502/ha and production of 651,041 ton has shown by Agricultural Statistics Yearbook 2006.

Table 4.2 Cane planted area (Ha). (Taiwan Sugar Corporation, 1999) Year Cane planted area (Ha)

1998-1999 40,709

According to National Agricultural Research Center for Kyusyu and Okinawa Region (2007), 1 kg of sugarcane grows about 4 to 5 m. When the sugarcane is planted about 30 cm of stem is planted. Then the assumption of sugarcane bud is carried by calculating 1 kg of 450 cm grown sugarcane from 30 cm sugarcane bud is:

1kg ×

Therefore it can be assumed the weight of sugarcane bud would be 0.07 kg. From this value the total amount of sugarcane bud can be calculated. According to Agricultural Statistics Yearbook (2006), the amount of produced grown sugarcane was 651,041 ton.

The amount of sugarcane will be:

area

Then the sugarcane bud per hectare is calculated:

ha

This is the amount of sugarcane bud required per hectare.

Calculating the total amount of sugarcane bud to produce 3.3 × 10⁴ ton of sugarcane from 268.75 ha of land is:

2. Material Outflow (1) Energy Loss

Energy outflow at agricultural stage estimated in fuels considered to be energy loss.

This is calculated by: assumed to be 0.1 of soil type of sandy soil with 2% slope.

= 0.1 ×10³ kg/m³ × 2400

CO2 emitted from diesel use in subsystem 1 is calculated. It was 1.31 × 10⁵ kg diesel consumed. To calculate CO2 emission, emission factor of 0.284 kg per kg of diesel is adapted from Simapro 7.1.

1.31 × 10⁵ kg diesel/year × 0.284 kg CO2/kg = 3.72 × 10⁴ kg CO2/year (4.1.1.21)

It should be noted that soil loss would not be count in consideration of less amount of soil been lost at sugarcane production.

(4) Sugarcane

3.30 × 10⁴ ton sugarcane is required to produce 10⁸ L of E3.

Harvested area was in average of 50,267 ha from 1989 to 1999 (Taiwan Sugar Corporation, 1997) (Table. 4.3). Cane harvested amount was in average of 4,272,417.3 tons from 1989 to 1999 (Taiwan Sugar Corporation, 1997) (Table. 4.4). Therefore 4.28

× 10⁹ kg of sugarcane was produced per year in Taiwan. After the harvest of sugarcane, there is also 80.6 ton/hectare of sugarcane yield recorded (Taiwan Sugar Corporation, 1997).

Table 4.3 Harvested area of sugarcane (ha). (Taiwan Sugar Corporation, 1999)

Year Harvested area of sugarcane (Ha)

1998-1999 36,339

Table 4.4 Sugarcane harvested amount from 1989 to 1990. (Taiwan Sugar Corporation, 1999)

Year Cane harvested amount (ton)

1998-1999 3,071,259

4.1.2 Transportation 4.1.2.1 Scenario 1 and 2

3.30 × 10⁴ ton of sugarcane was carried from sugarcane farm to ethanol factory. The travel distance of sugarcane from farm to the factory was assumed to be 30 km in both Scenario 1 and 2.

1. Material inflow (1) Sugarcane

3.30 × 10⁴ ton of sugarcane will be transported to the sugar refinery factory.

(2) Fuels

The distance between every farm and the factory are different. It was assumed that the traveling distance from the farm to the sugar refinery factory is 30 km. Assume that the truck with the capacity of 5 ton was occupied with 80%, thus 4 ton of sugarcane was carried by a truck. According to the data reported by Japan Institute of Logistics Systems (2006), the amount of diesel required is 0.0686 L/ton·km.

Therefore the amount of diesel used to carry 4 ton of sugarcane is:

3.30 × 10⁴ ton sugarcane ×

km ton

L

 0686 .

0 diesel × 30 km = 6.79 × 10⁴ L diesel

(4.1.2.1)

2. Material outflow (1) Energy Loss

The diesel consumption in this subsystem was 6.79 × 10⁴ L. The energy content of diesel is 38.2 MJ/L (Ministry of the Environment, 2003). These energy was either used

to power the truck or exhausted as waste heat. The amount of energy loss from transportation of sugarcane is calculated as following:

L Diesel

MJ 2 .

38 ×6.79 × 10⁴ L diesel = 2.59 × 10⁶ MJ (4.1.2.2)

4.1.3 Industrial production of ethanol 4.1.3.1 Scenario 1

Process of producing ethanol was examined with inputs of materials: water, lime, diesel and electricity. Ethanol production plants have outputs of energy loss and material outflow of bagasse and molasses which are the byproduct of sugar production and necessary to produce ethanol. At the stage of bioethanol production, basically there are two steps of fermentation and hydrolization as shown in Figure 4.1. In the case of sugarcane, ferment molasses which is a byproduct of sugar production then dilute this fermented molasses to be a finally produce hybrid ethanol (Kadam, 2002).

Figure 4.1 The process of ethanol production (Su, 2006) 1. Material inflow

(1) Water

Water was required to wash excess soils and leaves of sugarcane for production ethanol. According to Ometto et al (2004), the amount of water required to produce 1 ton of ethanol was 1.29 ×10⁵ kg/ton ethanol.

1.29 ×10⁵ kg/ton ethanol × 3.0 × 10⁶ L × 0.789 L kg ×

kg ton

1000 = 3.05 ×10⁸ kg water Cane Juice Fermentation Distillation Dehydration Ethanol

(2) Lime

An amount of lime used as clarifying materials at sugar production is calculated by Ometto et al (2004). It was 11.68 kg/t alcohol of lime used.

3 × 10⁹ mL ethanol × 0.789 g/mL = 2.37 ×10⁹ g = 2367 ton (4.1.3.2) 11.68 kg/t × 2367 ton = 2.76 ×10⁴ kg lime used (4.1.3.3)

(3) Sugarcane

The amount of sugarcane as input in this section was 3.30 × 10⁷ kg.

(4) Diesel

The amount of diesel used from Ethanol production plant to the Port and Santos Port in Brazil then from Brazil to Kaohsiung Port in Taiwan is calculated.

It is assumed that the distance from ethanol plant to the Santos Port is about 30 km.

Assume that the farm uses a truck that amount of sugarcane can carry 5 ton. According to the Japan Institute of Logistics Systems (2006), the amount of diesel required is 0.0686 L/ton·km.

Therefore the amount of fuel used to carry 4 ton of sugarcane is:

3.30 × 10⁴ ton sugarcane ×

km ton

L

 0686 .

0 × 30 km = 6.79 × 10⁴ L (4.1.3.4)

Daishou (2004) has calculated the distance from Santos Port to the Yokohama Port in Japan. The distance from Santos Port in Brazil to Yokohama Port in Japan is 12,000 miles (21911.6 km) transporting by 100,000t transoceanic tanker. It was assumed that the distance from Yokohama Port to he Kaohsiung Port is 2600 km. In total, the ethanol will be shipped for 24511.6 km.

The amount of ethanol carried from Brazil to Taiwan was 2.36 × 10³ ton Traveling distance is 24511.6 km therefore:

24511.6 km ×9.7149 ton/km = 2.38 × 10⁵ ton (4.1.3.5)

Therefore 2.38 × 10⁵ ton of diesel was required to transport ethanol from Brazil to Taiwan.

2. Material Outflow (1) Wastewater

In this section, the amount of biological oxygen demand (BOD) will be analyzed.

Vinasse will be produced as a residual substance left after sugarcane alcohol distillation stage and treatment of this vinasse is a most nuisance material to dispose (Polack et al., 1981; Cortez and Brossard Perez 1997). Vinasse has a light brownish color and contents high BOD₅ and acid material. It produces up to 15 times larger of quantities than the alcohol.

Patzek and Pimentel (2005) calculated the amount of BOD as:

BOD =

According to Patzek and Pimentel (2005), a minimum BOD concentration of 20,000 mg will be contained per liter of water and 14 liter of water is required per ethanol.

Therefore approximately 0.28 kg of BOD will be emitted to produce one liter of ethanol.

In this study 3000 kL of ethanol is assumed to be produced. Therefore:

Ethanol

(2) Mass ethanol

The amount of ethanol produced is assumed 3 × 10⁶ L.

(3) Diesel

The amount of diesel consumed by transporting bioethanol from ethanol factory to Santos Port in Brazil was 3.91 × 10³ L. Therefore the energy loss from 3.91 × 10³ L of

The amount of diesel consumed by transporting bioethanol from ethanol factory to Santos Port in Brazil was 3.91 × 10³ L. Therefore the energy loss from 3.91 × 10³ L of

在文檔中 考量可用能之生命週期評估─以臺灣生質酒精為例 (頁 56-0)