LCA of Manufacturing Lead Free Copper Alloys

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LCA of Manufacturing Lead-Free Copper Alloys

Atsushi Nakano

1;*

, Nurul Taufiqu Rochman

2

and Hidekazu Sueyoshi

1 1Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan 2Research Center for Physics, Indonesian Institute of Science, Tangerang 1530, Indonesia

To promote the recycling of copper alloy scrap, we developed a new technique for removing Pb from copper alloy scrap containing 2– 6 mass% Pb. However, we must evaluate quantitatively the level of environmental impact reduction that can be obtained using this new technology. In this study, a manufacturing system that produces Pb-free copper alloy products using copper alloy scrap was assessed by means of life cycle assessment (LCA). The superiority of the new manufacturing system that uses Pb-free copper alloy scrap over the conventional one that uses virgin materials was investigated from the viewpoint of environmental impact. LCA software (JEMAI-LCA) was used to assess environmental impacts such as global warming, acidification, energy consumption and resource consumption. We assessed the raw material acquisition and casting process of Pb-free copper alloy products. The subsequent processes such as machining, assembling, transportation, use and recycling/waste processing are not taken into account in the environmental impact assessment. The results show that the conversion of the conventional system that uses virgin materials into the new one that uses Pb-free copper alloy scrap decreases the environmental impact, significantly. This is attributed to the nonutilization of virgin materials and the decrease in energy consumption during the casting process.

(Received June 2, 2005; Accepted August 24, 2005; Published December 15, 2005)

Keywords: life cycle assessment, recycle, lead-free copper alloys

1. Introduction

In copper alloys, which are widely used in water faucets and pipes in freshwater service, some amount of Pb has usually been added to enhance its machinability.1)However, due to environmental concerns, the leaching standard value for Pb was revised to a stringent value of 0.01 mg/L in Japan in April, 2003.2)In response to this, Pb-free copper alloys have been developed. Most of the developed Pb-free copper alloys are manufactured from virgin materials, and Bi is added as a substitute element for Pb. If we continue the manufacturing method that uses virgin materials, the re-source consumption of not only Bi, which is a rare metal, but also of Cu, Zn and Sn increases. Moreover, an enormous amount of copper alloy scrap containing Pb will be accumulated without being recycled. These are undesirable situations from the viewpoints of efficient use of resources and recycling.

The authors developed a new technology for removing Pb from copper alloys containing Pb.3–6) If a manufacturing system for producing Pb-free copper alloy products using copper alloy scrap containing Pb is realizable by using this technology, the recycling the copper alloy scrap is possible. However, we must evaluate quantitatively how much environmental impact can be reduced by using this new technology.

In this study, a manufacturing system that produces Pb-free copper alloy products using copper alloys scrap was assessed by means of life cycle assessment7–9)(LCA). The

superiority of this new manufacturing system that uses copper alloy scrap over the conventional one that uses virgin materials was investigated from the viewpoint of environ-mental impact.

2. Analysis Method

The LCA software JEMAI-LCA (developed by the Japan Environmental Management Association for Industry) was used to assess environmental impacts such as global warm-ing, acidification, energy consumption and resource con-sumption. Table 1 shows the evaluated products. The evaluated products were former Pb-free brass which is manufactured from virgin materials, new Pb-free brass which is manufactured by removing Pb from brass scrap, conven-tional Pb-bronze, former Pb-free bronze which is manufac-tured from virgin materials, and new Pb-free bronze which is manufactured by removing Pb from bronze scrap. In Pb-free bronze, Bi was added as a substitute for Pb. Figure 1 shows a schematic diagram of the system boundary. The former Pb-free brass and former Pb-Pb-free bronze have been manufactured from virgin materials. These products are mixed with copper alloy scrap containing Pb after their use. Therefore, it is not possible to recycle them because the technology for classifying such scrap has not yet been established. Thus, the manufacturing system for former products may be regarded as an open system. On the other hand, it is possible to recycle new Pb-free brass and new Pb-free bronze because the copper alloy scrap containing Pb can be used as main raw materials. Thus, the new manufacturing system may be regarded as a closed system. It was assumed that copper alloy scrap can be reused repeatedly in this method. The system boundary in the inventory analysis was restricted from raw

Table 1 Evaluated products in this study.

Mark of product Product

A Former Pb-free brass

B New Pb-free brass

C Conventional Pb-bronze

D Former Pb-free bronze

E New Pb-free bronze

*Graduate Student, Kagoshima University. Present address: Graduate

School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan

Special Issue on Growth of Ecomaterials as a Key to Eco-Society II

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materials acquisition to casting, and the other processes were not included in the evaluation.

Figure 2 shows the flow of materials in the system boundary. In the former Pb-free brass (A), both return scrap turnings produced during the manufacturing and virgin materials are used as main raw materials. The new Pb-free brass (B) uses both return scrap turnings produced during the manufacturing and Pb-copper alloy scrap as main raw materials. The Pb removal is carried out after melting. The conventional Pb-bronze (C) uses both return scrap turnings produced during the manufacturing and Pb-copper alloy scrap as main raw materials, and also uses virgin materials for component adjustment. In the former Pb-free bronze (D), both return scrap turnings produced during the manufacturing

and virgin materials are used as main raw materials. The new Pb-free bronze (E) uses both return scrap turnings produced during the manufacturing and Pb-copper alloy scrap as main raw materials. The Pb removal is carried out after melting. The treatment of Pb-containing waste was excluded from the evaluation, because this technology has not yet been established. Virgin materials of 20 mass% are also added for component adjustment.

3. Result and Discussion

Inventory analysis was carried out on 1 kg of each product. The inventory data was obtained from the database of the LCA software in the raw materials acquisition process and the production management table of a water supply equip-ment company in the casting process, respectively.

Inventories for the manufacturing of the former Pb-free brass (A) and new Pb-free brass (B) are shown in Tables 2 and 3, respectively. It was assumed that the electric power consumption of the new Pb-free brass (B) using brass scrap decreases by 46.3% compared with that of the former one (A) using virgin materials,10)because the melting point of brass is

lower than that of electric copper. However, the new Pb-free brass (B) requires electric power for Pb removal. Conse-quently, it was estimated that the electric power consumption of the new Pb-free brass (B) increases by 33.0% compared with that of the former one (A) (on the basis of the experimental data). In the new Pb-free brass (B), Pb compound that was removed from molten brass was included in the slag (waste). Inventories for the manufacturing of the

Recycling Assembling

Using

Waste Machining

Transportation Casting Raw materials aquisition

Virgin materials

System boundary A : Former Pb-free brass B : New Pb-free brass

C : Conventional Pb-bronze D : Former Pb-free bronze E : New Pb-free bronze

Fig. 1 Schematic diagram of system boundary.

Casting

Virgin materials Copper alloy scrap

Melting Transportation

Pb removal

A : Former Pb-free brass B : New Pb-free brass C : Conventional Pb-bronze

D : Former Pb-free bronze E : New Pb-free bronze Return scrap turnings

Fig. 2 Material flow in system boundary.

Table 2 Inventory for the manufacturing of former Pb-free brass.

Input Product Output

Elect.Cu 0.60 kg 1.0 kg Product (Pb-free brass)

1.133 kg Return scrap turnings

Virgin Zn 0.404 kg (Pb-free brass)

0.038 kg Slag (Waste)

Return scrap turnings

1.287 kg A a kg CO2

(Pb-free brass) b kg CH4

c kg N2O

Electricity 2.60 kwh d kg SO2

e kg NOx

Table 3 Inventory for the manufacturing of new Pb-free brass.

Input Product Output

Copper alloy scrap 1.004 kg 1.0 kg Product (Pb-free brass)

1.133 kg Return scrap turnings

Return scrap turnings 1.287 kg

(Pb-free brass)

(Pb-free brass) 0.063 kg Slag (Waste)

Ca–Si compound 0.040 kg B a kg CO2

b kg CH4

c kg N2O

Electricity 1.86 kwh d kg SO2

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conventional Pb-bronze (C) and former Pb-free bronze (D) are shown in Tables 4 and 5, respectively. In the former Pb-free bronze (D), the electric power consumption for melting is larger than that in the case of the conventional Pb-bronze

(C). This is because the former Pb-free bronze (D) used virgin materials as main raw materials. Table 6 shows the inventory for the manufacturing of the new Pb-free bronze (E). It was assumed that the electric power consumption of

Table 4 Inventory for the manufacturing of conventional Pb-bronze.

Input Product Output

Copper alloy scrap 0.450 kg 1.0 kg Product (Pb-bronze)

Return scrap turnings

(Pb-bronze) 1.287 kg 1.133 kg

Return scrap turnings (Pb-bronze)

Virgin

Cu–Zn–Sn–Pb alloy 0.511 kg 0.009 kg

Return scrap turnings (Waste)

Virgin 6/4 brass 0.010 kg 0.038 kg Slag (Waste)

Virgin Zn 0.006 kg C 0.00017 kg Dust (Waste)

Silica sand 0.122 kg 0.330 kg Sand (Waste)

Core 0.261 kg a kg CO2

Heavy oil 0.284 kg b kg CH4

LNG 0.013 kg c kg N2O

Electricity 0.921 kwh d kg SO2

Industrial water 2.026 kg e kg NOx

Table 5 Inventory for the manufacturing of former Pb-free bronze.

Input Product Output

Virgin Cu–Zn–Sn–Bi alloy 0.911 kg 1.0 kg Product (Pb-free bronze)

Return scrap turnings

(Pb-free bronze) 1.287 kg 1.133 kg

Return scrap turnings (Pb-free bronze)

Virgin 6/4 brass 0.010 kg

0.009 kg Return scrap turnings

Virgin Zn 0.006 kg (Waste)

Silica sand 0.122 kg 0.038 kg Slag (Waste)

Core 0.261 kg D 0.00017 kg Dust (Waste)

Heavy oil 0.284 kg 0.330 kg Sand (Waste)

LNG 0.013 kg a kg CO2

Electricity 1.188 kwh b kg CH4

c kg N2O

Industrial water 2.026 kg d kg SO2

e kg NOx

Table 6 Inventory for the manufacturing of new Pb-free bronze.

Input Product Output

Copper alloy scrap 0.730 kg 1.0 kg Product (Pb-free bronze)

Return scrap turnings

(Pb-free bronze) 1.336 kg 1.133 kg

Return scrap turnings (Pb-free bronze)

Virgin Cu–Zn–Sn–Bi alloy 0.182 kg

0.009 kg Return scrap turnings

Virgin 6/4 brass 0.010 kg (Waste)

Virgin Zn 0.006 kg 0.083 kg Slag (Waste)

Ca–Si compound 0.073 kg E 0.00017 kg Dust (Waste)

Silica sand 0.122 kg 0.330 kg Sand (Waste)

Core 0.261 kg a kg CO2

Heavy oil 0.284 kg b kg CH4

LNG 0.013 kg c kg N2O

Electricity 1.004 kwh d kg SO2

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the new Pb-free bronze (E) increases by 33.0% compared with that of the former one (D) (on the basis of the experimental data). In the new Pb-free bronze (E), the Pb compound that was removed from molten bronze was included in the slag (waste).

Table 7 shows the results of inventory analysis of energy consumption and exhaust gas. The energy consumption in the raw materials acquisition process of the new Pb-free brass (B) is 0, resulting in the decrease in the total energy consumption. This is because the new Pb-free brass (B) used Pb-copper alloy scrap as raw materials. The energy con-sumption of conventional Pb-bronze (C) is less than that of the former Pb-free bronze (D). This may be due to the use of Pb-copper alloy scrap as raw materials. In the new Pb-free bronze (E), the each energy consumption in raw materials acquisition process decreases, resulting in the decrease in the total energy consumption. This is because of the reduction in the use of virgin materials as raw materials. In exhaust gases, the amount of CO2 is the largest in each manufacturing system. In the new Pb-free brass (B), the each exhaust gas in raw materials acquisition process is 0, resulting in the decrease in the total amount of exhaust gases. This is attributed to the utilization of Pb-copper alloy scrap as raw

materials. The amount of each exhaust gas of the former Pb-bronze (D) is larger than that in the case of the conventional Pb-bronze (C). This results from the use of virgin materials as raw materials. The amount of each exhaust gas of the new free bronze (E) is less than that in the case of the former Pb-free bronze (D). Particularly, the reduction in the raw materials acquisition process is considerable. This is because the use of virgin materials as raw materials decreased.

Table 8 shows the results of inventory analysis of resource consumption. The resource consumption is decreased sig-nificantly by a shift to the new Pb-free brass (B) and Pb-free bronze (E).

Figure 3 shows the results of characterization for global warming. In each manufacturing system, CO2 has a signifi-cant influence on global warming. This is because the amount of CO2 emission is much larger than that of other gas emissions, even though the characterization factor of CO2is considerably smaller than that of CH4and N2O. The overall influence on global warming is decreased by 78% in Pb-free brass and by 43% in Pb-free bronze by shifting from the former manufacturing system to the new one.

Figure 4 shows the results of characterization for acid-ification. SO2 has a considerable influence on acidification.

Table 7 Results of inventory analysis of energy consumption and exhaust gas.

Product Process Unit Input Output

Oil LNG Coal CH4 CO2 N2O NOx SO2

Raw material 1:9910 1 5:9810 2 4:4910 1 1:1910 5 2.07 1:8610 4 3:2010 3 1:0810 2

A Casting 1:5810 1 6:9810 2 1:4010 1 2:5210 5 1.08 2:5210 5 6:5610 4 8:2610 4

Total 3:5710 1 1:3010 1 5:8910 1 3:7110 5 3.15 2:1110 4 3:8610 3 1:1610 2

Raw material 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

B Casting 1:1310 1 4:9910 2 9:9810 2 1:8010 6 7:7010 1 8:4710 6 4:6910 4 5:9110 4

Total 1:1310 1 4:9910 2 9:9810 2 1:8010 6 7:7010 1 8:4710 6 4:6910 4 5:9110 4

Raw material 1.46 7:3610 2 1:1110 1 1:8010 5 9:9510 1 9:3910 5 7:7310 4 1:5610 3

C Casting kg 3:4010 1 5:2710 3 1:0410 1 9:2110 6 4:4410 1 1:9910 5 2:6810 4 2:8110 4

Total 1.80 7:8810 2 2:1510 1 2:7210 5 1.44 1:1410 4 1:0410 3 1:8410 3

Raw material 1.60 1:1010 1 1:8310 1 3:0910 5 1.57 1:0810 4 1:1310 3 2:1310 3

D Casting 3:510 1 5:4610 3 1:3410 1 1:1910 5 5:6510 1 2:0610 5 3:3310 4 3:6110 3

Total 1.95 1:1610 1 3:1710 1 4:2810 5 2.13 1:2810 4 1:4710 3 2:4910 3

Raw material 1.34 4:0710 2 4:6710 2 6:3610 6 4:8110 1 8:1610 5 4:5410 4 1:1010 3

E Casting 3:410 1 5:3310 3 1:1410 1 1:0010 5 4:8110 1 2:0110 5 2:8810 4 3:0610 4

Total 1.68 4:6010 2 1:6010 1 1:6410 5 9:6210 1 1:0210 4 7:4210 4 1:4110 3

Table 8 Results of inventory analysis of resource consumption.

Metal Unit Product

A B C D E

Cu 6:6910 1 0.00 4:4210 1 7:8610 1 1:3710 1

Zn 2:5010 1 0.00 3:5610 2 7:3810 2 2:0810 2

Sn 0.00 0.00 2:1510 2 4:0110 2 6:7010 3

Pb kg 0.00 0.00 2:8110 2 0.00 0.00

Bi 0.00 0.00 0.00 2:7310 2 4:6010 3

Ca 0.00 1:7310 2 0.00 0.00 2:3210 2

Si 0.00 3:7110 2 0.00 0.00 4:9510 2

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The overall influence on acidification is decreased by 91% in Pb-free brass and by 36% in Pb-free bronze by shifting from the former manufacturing system to the new one.

Figure 5 shows the results of characterization for energy consumption. In the new Pb-free brass (B), the category indicator of coal is the smallest. This depends on both the coal consumption and the smallest characterization factor of coal. Oil has a large influence on energy consumption. This is because the characterization factor of oil is the second largest among those three energy resources and oil consumption is very large. The overall influence on energy consumption is decreased by 73% in Pb-free brass and by 19% in Pb-free bronze by shifting from the former manufacturing system to the new one.

Figure 6 shows the results of characterization for resource consumption. Both Ca and Si are used for Pb removal. In the new manufacturing system, the influence of Ca and Si is small. The category indicator of the new Pb-free brass (B) is 0, because virgin materials are not used. In each manufactur-ing system, Sn consumption has a significant influence on resource consumption in Pb-free bronze. This is because the

category indicator of Sn is large (Sn is a depleting metal), even though the amount of Sn consumption is small. The overall influence on energy consumption is decreased by 83% by shifting from the former Pb-free bronze (D) to the new one (E).

4. Conclusion

The inventory analysis of both the former Pb-free copper alloy manufacturing system that uses virgin materials and the new one that uses copper alloy scrap containing Pb, which is removed in the production process, was carried out. The results shows that the shift from the former manufacturing system to the new one reduces environmental impacts such as global warming, acidification, energy consumption and resource consumption significantly. Thus, in the LCA perspective, the new manufacturing system that uses a recycled copper alloy scrap is superior to the former one that uses virgin materials.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

A

B

C

D

E

GW

/ CO

2

eq.kg

N2O

CH4 CO2

Fig. 3 Characterization for global warming,GW.

0.0

5.0

10.0

15.0

A

B

C

D

E

A /

10

-3

SO

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eq.kg

SO

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NOx

Fig. 4 Characterization for acidification,A.

0.0

0.5

1.0

1.5

A

B

C

D

E

Coal

LNG

Oil

EC

/ 10

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MJ

Fig. 5 Characterization for energy consumption,EC.

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B

C

D

E

Cu

Zn

Sn

Bi

Pb

Ca

Si

RC

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Acknowledgments

This work was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, No. 16510063.

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Figure

Table 1Evaluated products in this study.

Table 1Evaluated

products in this study. p.1
Fig. 1Schematic diagram of system boundary.
Fig. 1Schematic diagram of system boundary. p.2
Table 2Inventory for the manufacturing of former Pb-free brass.

Table 2Inventory

for the manufacturing of former Pb-free brass. p.2
Figure 2 shows the flow of materials in the system

Figure 2

shows the flow of materials in the system p.2
Fig. 2Material flow in system boundary.
Fig. 2Material flow in system boundary. p.2
Table 4Inventory for the manufacturing of conventional Pb-bronze.

Table 4Inventory

for the manufacturing of conventional Pb-bronze. p.3
Table 5Inventory for the manufacturing of former Pb-free bronze.

Table 5Inventory

for the manufacturing of former Pb-free bronze. p.3
Table 6Inventory for the manufacturing of new Pb-free bronze.

Table 6Inventory

for the manufacturing of new Pb-free bronze. p.3
Table 7Results of inventory analysis of energy consumption and exhaust gas.

Table 7Results

of inventory analysis of energy consumption and exhaust gas. p.4
Table 8Results of inventory analysis of resource consumption.

Table 8Results

of inventory analysis of resource consumption. p.4
Fig. 4Characterization for acidification, A.
Fig. 4Characterization for acidification, A. p.5
Fig. 5Characterization for energy consumption, EC.
Fig. 5Characterization for energy consumption, EC. p.5
Fig. 3Characterization for global warming, GW.
Fig. 3Characterization for global warming, GW. p.5
Fig. 6Characterization for resource consumption, RC.
Fig. 6Characterization for resource consumption, RC. p.5

References