Quality- and Dilution Losses in the Recycling of ... - ACS Publications

Aug 9, 2012 - The composition of a passenger car (henceforth, a car) in terms of the four types of ferrous materials was also obtained by use of WIO-M...
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Quality- and Dilution Losses in the Recycling of Ferrous Materials from End-of-Life Passenger Cars: Input-Output Analysis under Explicit Consideration of Scrap Quality Shinichiro Nakamura,*,†,‡ Yasushi Kondo,† Kazuyo Matsubae,§ Kenichi Nakajima,∥ Tomohiro Tasaki,∥ and Tetsuya Nagasaka§ †

Graduate School of Economics, Waseda University, Tokyo, Japan Ecotopia Science Institute, Nagoya University, Nagoya, Japan § Graduate School of Engineering, Tohoku University, Sendai, Japan ∥ Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, Tsukuba, Japan ‡

S Supporting Information *

ABSTRACT: Metals can in theory be infinitely recycled in a closed-loop without any degradation in quality. In reality, however, open-loop recycling is more typical for metal scrap recovered from end-of-life (EoL) products because mixing of different metal species results in scrap quality that no longer matches the originals. Further losses occur when meeting the quality requirement of the target product requires dilution of the secondary material by adding high purity materials. Standard LCA usually does not address these losses. This paper presents a novel approach to quantifying quality- and dilution losses, by means of hybrid input-output analysis. We focus on the losses associated with the recycling of ferrous materials from end-of-life vehicle (ELV) due to the mixing of copper, a typical contaminant in steel recycling. Given the quality of scrap in terms of copper density, the model determines the ratio by which scrap needs to be diluted in an electric arc furnace (EAF), and the amount of demand for EAF steel including those quantities needed for dilution. Application to a highresolution Japanese IO table supplemented with data on ferrous materials including different grades of scrap indicates that a nationwide avoidance of these losses could result in a significant reduction of CO2 emissions.

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INTRODUCTION

recycling of EoL materials is thus associated with a loss in the quality of the relevant materials.6 The example of ferrous materials can be used to illustrate the above point. For ferrous materials, the occurrence of copper and tin is undesirable, and is subject to strict control (refs 7,8; see also Table S1 in Supporting Information (SI)). The recycling of secondary metals usually involves remelting processes. Thermodynamics dictates that some metal species can be recovered, but others are not, at least under the current economic and technical conditions of remelting processes. In particular, copper and tin cannot be removed in remelting processes such as BOF (basic oxygen furnace) and EAF (electric arc furnace)9 (for details of BOF and EAF, see refs 8 and 10). Accordingly, copper and tin are contaminants for iron and steel scrap (IS scrap). For instance, SI Table S1 indicates

Metals are indestructible atoms, and hence can in theory be recycled infinite times to produce new materials without any deterioration in their inherent properties as basic materials. In other words, they can be recycled in a closed-loop infinitely. This feature distinguishes metal from molecular based materials, like plastics, and fiber materials.1 In reality, however, metals do not usually occur separately, but in combinations in alloys and/or in combined forms based on bondings of a physical and chemical nature. When products composed of metals such as cars or electronics are discarded, and submitted to end-of-life (EoL) processes, a mixing of different metal species is likely to occur due to incomplete separation and/or liberation. The mixing in the EoL process of metals of different inherent properties produces secondary metals the properties of which are no longer equal to their original ones.2 Consequently, in reality, not closed-loop cycles but open-loop cycles are typical for many metals recovered from EoL products such as cars and electronics.3−5 Open-loop © 2012 American Chemical Society

Received: Revised: Accepted: Published: 9266

April 11, 2012 August 8, 2012 August 9, 2012 August 9, 2012 dx.doi.org/10.1021/es3013529 | Environ. Sci. Technol. 2012, 46, 9266−9273

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Policy Analysis

Figure 1. Quality- and dilution losses due to mixing of material species.

possible by detailed study of economy-wide interindustry flows of ferrous materials including eight types of IS scrap in a form compatible with the Japanese IO table of around 420 production sectors.13 The copper content of IS scrap recovered from an ELV was obtained from a detailed study by Tasaki14 on the material composition of dismantled ELV parts and components and their treatment. The issues related to openloop recycling and dilution by primary material are addressed in line with ref 15. The losses of dilution are assessed by comparing the environmental burdens associated with scenarios that differ from each other in terms of the need for dilution, and the feedstock to be used for dilution. Similarly, we assess quality losses by setting-up scenarios which differ from each other in terms of whether recovered scrap is of default quality that is to be fed into an EAF only, or of primary quality that can be fed into a BOF. The losses are evaluated in terms of the emission of greenhouse gases (GHG), and the requirements for energy and resources.

that IS scrap with 0.2% copper is not a suitable material to produce steel sheets for deep drawing, but is still suitable to produce section steel. When the contaminants occurring in secondary materials exceed the maximum content allowed for the target product to be produced out of the secondary material, additional high purity materials must be added to dilute the contaminant to an acceptable level. This refers to another type of loss associated with recycling that is termed the dilution loss in ref 6. Dilution loss occurs when the quality of the secondary material does not satisfy the quality requirement of the target product. It leads to a depletion of resource reserves and decreases the resource efficiency of the system.6 For instance, if a given mass of IS scrap with 0.60% copper is to be used to produce section steel, it has to be diluted with primary iron of equal mass to achieve the requirement of 0.3% copper. Notwithstanding the observations made in the abovementioned studies and elsewhere, standard LCA usually assumes recycling to take place in a closed-loop,10,11 and does not consider the generation of quality and dilution losses. Reuter and his associates6,12 coped with this fundamental weakness of the LCA of open-loop recycling by proposing an innovative method, the exergetic LCA, to quantify material losses, quality losses, and dilution losses by means of chemical exergy analysis. They estimated the quality loss that results from mixing alloys by the associated reduction in chemical exergy relative to the original states before mixing. The dilution loss was obtained by the exergy of the mass of primary material that is needed for dilution. Their pioneering study represents a process based exergy analysis of the losses involved in openloop recycling. The hybrid-IOA-(input-output analysis)-based approach to LCA has increasingly become a widely used holistic methodology in industrial ecology. The aim of this paper is to provide a hybrid-IOA-based alternative to the process-based exergy analysis pioneered by Reuter and his associates. This paper is concerned with the quantification of quality- and dilution losses associated with metal recycling under explicit consideration of the economy-wide interindustry flow of inputs and outputs by means of a new hybrid-IOA approach. More specifically, this paper focuses on the quality- and dilution losses associated with the recycling of ferrous materials from ELV due to the mixing of copper. Material losses in EoL and refining processes are not considered. Our approach to scrap quality is based on explicit consideration of different grades of IS scrap and their use patterns, which were made

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MODEL Quality- and Dilution Losses. Figure 1 gives a schematic representation of the quality- and dilution losses for the simplified case of a product consisting of two metal species, a red one with mass c and a white one with mass x−c, a combination of which is required to realize the functionality of the product. In the EoL process, mixing of these species occurs, and results in mixed scrap that can be used neither as white nor as red metal species. Associated with this EoL process is the quality loss in the amount of x because none of its components is able to realize the original functionality. Furthermore, if the degree of mixing, say, θ = c/x, exceeds the permissible level, say, θ*, it has to be diluted by primary material (white species in this example) by amount x(θ/θ* − 1). This amount refers to the dilution loss. Henceforth, we consider the case where η ≡ θ/θ* ≥ 1. The case of η < 1 is excluded because it corresponds to underutilization of potential scrap value, and the loss of possible profit. Types of Secondary Ferrous Materials. Based on their origins, IS scrap can be distinguished into two types: new scrap originating from production processes and old scrap originating from EoL products. Major components of the former are pig iron scrap, in-house scrap, and industrial scrap, while those of the latter are heavy scrap, shredded scrap, and pressed scrap.13 Stainless steel scrap, while small in quantity compared to other IS scrap items, occurs in both new and old scrap.13 9267

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In the classification of the data employed by ref 16 “pig iron” was the closest that corresponds to the concept of primary material within the current framework of analysis. Accordingly, pig iron henceforth refers to the primary (ferrous) material. Direct and Indirect Use of Secondary Materials. Remarkable differences exist among the three ferrous materials, pig iron, new scrap, and old scrap, in terms of their use (SI Table S2, panel (a)). Old scrap is mostly used to produce EAF steel but not BOF steel, whereas pig iron is mostly used to produce BOF steel (see ref 10 for further details of iron production processes). In contrast to old scrap, a sizable portion of new scrap is used to produce BOF steel. New scrap is more homogeneous than old scrap, and is subject to lesser extents of mixing: its quality is somewhere between old scrap and pig iron. In which final products are ferrous materials embedded? Answering this question requires knowledge of the material composition of final products. We have elsewhere developed an IO based methodology, WIO-MFA,17,18 to estimate the material composition of products by tracing the flow of materials along the supply chain upward from basic materials toward final products across different stages of fabrication. Application of this methodology to the Japanese IO table for the year 2005,16 supplemented by detailed data on the generation and use of scrap,13 shows that old scrap mostly ends up in construction, whereas pig iron mostly ends up in machinery, including passenger cars, with new scrap somewhere in between (SI Table S2, panel (b)). This can be attributed to the fact that machinery, due to its high requirements for functionality, is mostly made out of high-quality steel products that are made of BOF steel that, in turn, is mostly made of pig iron. On the other hand, quality requirements for construction are not as high as those for machinery, and can be met by steel products made of EAF steel that is mostly made of secondary materials. Ferrous Materials (Pig Iron, New Scrap, Old Scrap) Constituting a Car. The composition of a passenger car (henceforth, a car) in terms of the four types of ferrous materials was also obtained by use of WIO-MFA (SI Table S3). Of the ferrous materials constituting a car, around 30% comes from secondary sources, of which only one-third originates from EoL sources. This implies that a closed-loop recycling of ferrous materials does not apply to cars. Only around 10% of ferrous materials constituting an ELV can find its way back into a new car, with the remaining 90% being put to other uses. Of the 90%, some portion will be reused as second hand parts and components, while the rest will end up in products other than cars, say, in buildings. The presence of a sizable quality loss is thus indicated. This finding is consistent with ref 5 which finds that open cycles are typical for many metals. Quality of IS Scrap Recovered from ELV. Consider the case where ELV is submitted to the following three EoL processes that represent a typical pattern of ELV treatment in Japan: 1. Disassembling of parts and components for reuse in used cars for repair and/or replacement. 2. Disassembling for recycling, resulting in disassembled scrap for recycling. 3. Shredding, resulting in shredded scrap.

processes hazardous items such as oil, fuel, batteries, freon, and air bags are removed prior to the above EoL processes. Contamination with copper mostly occurs due to incomplete liberation/separation of parts and components containing copper.12,19,20 Henceforth it is assumed that disassembled scrap for recycling is not submitted to further separation between ferrous and copper components, but is used as IS scrap as a whole: copper in scrap remains mixed and is not submitted to any separation process. This provides a reasonable approximation to the actual practice. Our estimation of the metal composition of IS scraps recovered by the three EoL processes is based on a detailed study by ref 14 on the metal composition for 25 items of parts and components based on a sample of six types of ELV and a representative pattern of the application of the EoL processes to each of these items that was obtained by an extensive survey of around 170 ELV dismantlers in Japan (see SI Table S4 for details). After the parts and components have been disassembled for reuse and recycling purposes, the remaining portion of ELV is submitted to shredding, and is transformed into shredded scrap. Table 1 Table 1. Scrap for Recycling Recovered from an ELV Cu in IS scrapa

metal composition: kg

a

scrap types

Fe

Cu

Zn

Al

%

disassembled scrap shredded scrap total

273.7 407.8 681.5

2.5 1.1 3.6

0.0 3.6 3.6

27.1 2.3 29.4

0.91 0.27 0.53

Cu in scrap = Cu/(Cu + Fe).

gives the metal composition of disassembled scrap and shredded scrap. The occurrence of zinc and aluminum causes no problem regarding the quality of scrap as ferrous materials because these metals can easily be separated in remelting processes.9 Comparison with the permissible levels of copper contamination (SI Table S1) indicates that disassembled scrap with around 1% of copper requires dilution even as feed to produce steel bars, whereas no dilution is necessary for shredded scrap when used for section steel or steel bars. In accordance with Figure 1, if disassembled scrap (θ = 0.0091) is to be used to produce section steel (θ* = 0.003), it needs to be diluted at the rate of θ/θ* = 0.0091/0.003 = 3.03. The IO Model. It was shown above that the use of EAF steel in car production is limited to around 30%, and hence closedloop recycling of IS scrap is not possible. For recycling of scrap recovered from ELV to occur, an expansion of the system is needed to accommodate the “extra” demand for EAF steel that absorbs the IS scrap that is not absorbed by car production. It follows that the functional unit must include the demand for EAF steel as well: a system expansion is needed. Geyer21 takes a similar approach, but is not explicit about where the scrap is to be used. If dilution is required, the demand for EAF steel must include the diluted portion as well. In accordance with ISO 14044, our modeling of recycling acknowledges that material not recycled needs to be replaced by primary material feedstock, and hence is based on the end-of-life recycling approach.22 Our analysis is based on a simplified WIO model23 augmented with an “extra” EAF sector, a single EoL sector (ELV treatment), and a single waste item (ELV):

Since reuse of disassembled parts and components in their original functionality does not affect scrap quality, they are not considered below. It is also noted that in real ELV treatment 9268

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Environmental Science & Technology −1 ⎛ x I ⎞ ⎛ I − AI −aEAF −aELV ⎞ ⎛ fI ⎞ ⎟ ⎟ ⎜ ⎜x ⎟ ⎜ 1 0 ⎟ ⎜ fEAF ⎟ ⎜⎜ EAF ⎟⎟ = ⎜⎜ 0 ⎟ ⎜ ⎟ ⎝ x ELV ⎠ ⎝ 0 0 1 ⎠ ⎝ wELV ⎠

e = ( RI rEAF

⎛ xI ⎞ ⎜ ⎟ rELV )⎜ x EAF ⎟ ⎜ ⎟ ⎝ x ELV ⎠

Policy Analysis

where ap,EAF refers to the input of pig iron per unit of output of the extra EAF sector. anew,EAF and aold,EAF are defined analogously. For the original EAF processes, this condition is not assumed. It is the input coefficients of ferrous materials of the extra EAF sector that are altered subject to the scenarios under consideration. Considering the high quality of new scrap (SI Table S2) and following ref 6, it is assumed that new IS scrap can substitute for pig iron as a dilutant. Following ref 15 under consideration of eq 5, the IO coefficients of the ferrous materials are then given by

(1)

(2)

where e refers to the vector of environmental interventions, AI to the matrix of input coefficients of goods- and services producing sectors, aELV to the vector of the input coefficients of the EoL (ELV treatment) sector, RI to the intervention matrix associated with the production of goods and services, and rELV to the intervention vector associated with the EoL sector. f I refers to the vector of final demand for goods and services, and wELV to the amount of ELV, ⎛ f = one car ⎞ ⎜ car ⎟ ⎜ ⎟ 0 fI = ⎜ ⎟ ⋮ ⎜⎜ ⎟⎟ ⎝ ⎠ 0

(3)

wELV = one ELV in kg

(4)

a p,EAF + anew,EAF =

aold,EAF =

1 (1 + ε)η

(6)

(7)

where η−1 refers to the ratio by which old scrap needs to be diluted by pig iron (and/or new scrap) in the EAF process (see Figure 1). If η = 1, EAF becomes a 100% old scrap-based steel making process, which is its predominant pattern.10 On the other hand, if η ≫ 1, EAF becomes a predominantly primaryor new scrap-based steel making process. The supply demand balance, or the excess supply, of newand old IS scrap for a given final demand is given by ⎛ xnew ⎞ ⎜ ⎟ = G Ix I + gEAFfEAF + gELV wELV ⎝ xold ⎠

where it is assumed that sector 1 refers to the car manufacturing sector. f EAF refers to the final demand for EAF steel produced by the extra EAF sector to absorb IS scrap that is not absorbed by car production. It is important to note that there are two EAF processes in eq 1, one occurring in AI, the original EAF sector, and one occurring outside AI, the extra EAF sector, whose vector of input coefficients is denoted by aEAF. The row of AI referring to the intermediate demand for the original EAF sector contains nonzero elements because a limited amount of EAF steel is used in car production. In contrast, there is no intermediate demand for the product of extra EAF sector, because the sector is introduced to refer to the EAF production that is not related to car production. The demand for its product comes from f EAF only. rEAF refers to the intervention vector associated with the extra EAF sector. The same vector is used for the original EAF sector as well (it occurs in RI). xI refers to the vector of output of goods- and service producing sectors induced by the final demand (f I, f EAF, wELV). Because of the absence of intermediate demand for the extra EAF sector, its output is equal to f EAF in eq 2, that is, xEAF = f EAF. The same applies to the ELV sector as well, that is, xELV = wELV. We now turn to the mass balances of the extra EAF process. Assuming for simplicity the absence of input losses, its inputoutput balance is given by

(8)

where xI is given by eq 1, and GI, gEAF and gELV refer to the matrices of net scrap generation coefficients of the goods- and services production sectors, the extra EAF sector, and the ELV process, respectively. Note that ⎛ gnew,EAF ⎞ ⎛−anew,EAF ⎞ ⎟⎟ = ⎜ gEAF = ⎜⎜ ⎟ ⎝ gold,EAF ⎠ ⎝ −aold,EAF ⎠

(9)

because the extra EAF sector is assumed to generate no IS scrap. Accordingly, gEAF f EAF refers to the amount of IS scraps used by the extra EAF sector. The second element of gELVwELV, gold,ELVwELV, gives the mass of IS scrap that is recovered from an ELV. This is the only source of old IS scrap, while the first element of GIxI is the only source of new IS scrap. Following ref 15, the amount of final demand for the extra EAF sector that is required for the sector to use up a given amount of xold, say, xo̅ ld, is given by fEAF = xold (10) ̅ (1 + ε)η As mentioned above, the occurrence of aluminum and zinc in scrap poses no problem to the quality of IS scrap as ferrous materials, whereas copper is a contaminant of IS scrap. Accordingly, we henceforth focus on IS scrap that includes copper, but excludes zinc and aluminum. From Table 1, gold,ELVwELV = 685.1 kg and θ = (2.5 + 1.1)/685.1 = 0.0052. If the scrap is to be used to produce section steel (SI Table S1), η = 0.0052/0.003 = 1.73. It is important to note that gold,ELVwELV, the old IS scrap generated, is not equal to xo̅ ld in eq 10, the old IS scrap that remains unused in car production, because of the fact that some portion of old IS scrap is used in car production. xo̅ ld is obtained by imposing f EAF = 0 in eqs 1 and 8. This calculation also gives the amount of new scrap that is available in the absence of the open-loop recycling, xn̅ ew.

EAF steel = pig iron + new scrap + old scrap + ferroalloys = (pig iron + new scrap + old scrap)(1 + ε),

where ε ≥ 0 denotes the ratio of ferroalloys to the input of ferrous materials. Dividing both sides of this equation by the output results in 1 = (a p,EAF + anew,EAF + aold,EAF)(1 + ε)

η−1 (1 + ε)η

(5) 9269

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The functional unit is given by eqs 3 and 4 where the final demand for EAF is given by eq 10 with η fixed at the value for DILp applied to all the scenarios because comparison of alternative scenarios under the same functional unit calls for the same amount of demand for EAF steel for cases both with and without dilution. With regard to the input coefficients, scenario specific values of η apply as in Table 2. It was found above that recycling of ferrous materials from ELV in Japan is likely to be accompanied by sizable quality- and dilution losses. The default scenario, DILp can then be seen to correspond to the real situation. NODIL refers to the case where the use of scraps in an EAF needs no dilution. QLTYs refers to the case where the shredded scrap recovered from an ELV is of primary iron quality: the ELV process then generates, in place of old IS scrap, an equal amount of pig iron as a byproduct, which is represented as a negative input of pig iron in accordance with the standard practice of IOA.24 The recovery of scrap contributes directly to the saving of primary product it substitutes for. QLTYs is nested within NODIL because scrap of primary quality requires no dilution. QLTYa refers to the case where both types of scrap are of primary quality, and corresponds to the standard LCA where recycling of scrap takes the form of closed-loop material recycling (ISO14049, refs 1,11,25). In standard LCA, issues of dilution and quality are not taken into account.6 In the absence of a need for dilution, NODIL gives the default scenario with open-loop recycling, while QLTYa gives the scenario with closed-loop recycling. Consideration of scenarios DIL, and QLTYs is a distinguishing feature of this paper. Improvement in the quality of recovered scrap will require additional inputs to the ELV process for its enhanced function. This effect is neglected for simplicity and lack of information. A sensitivity analysis will be conducted instead.

The effects of reuse of recovered parts and components in used cars and or repair are not considered. Items of waste/ byproduct other than IS scrap are not considered. Scenarios. Based on the IO model, six scenarios are formulated here to evaluate the losses (Table 2). The first four Table 2. Scenario Descriptions scenario

η

DILp DILpn DILn NODIL QLTYs QLTYa

1.73 1.73 1.73 1 1 1

EoL sectora

Extra EAF sectorb

gold,ELV

ap,ELV

ap,EAF

anew,EAF

aold,EAF

s+d s+d s+d s+d d 0

0 0 0 0 −s −(s+d)

>0 >0 0c 0 0 0

0c >0 >0 0 0 0

>0 >0 >0 >0 >0 >0

a

s: shredded scrap. d: disassembled scrap. s+d refers to the fact that it applies to both s and d. When recovered IS scrap is to be fed into an EAF, it occurs in column gold,ELV, whereas when it is of primary quality to be fed into a BOF, it occurs in column ap,ELV with a negative sign. b See eqs 6 and 7. cSet to zero by assumption.

scenarios are concerned with the effects of dilution, whereas the remaining two scenarios are concerned with the effects of reuse. Scenarios with DIL refer to the case where dilution is required and are distinguished in terms of dilutant(s) being used. DILp refers to the case where only pig iron is used for dilution, DILpn to the case where both pig iron and new scrap are used, and DILn to the case where only new scrap is used. DILp is the most conservative case, and serves as default scenario. In DILpn, the proportion between pig iron and new scrap in eq 6 is determined by the amount of new scrap that is available to (and used up by) the extra EAF sector, xn̅ ew. On the other hand, DILn refers to the case where there is no limitation to the availability of IS scrap: the required amount will be supplied from somewhere. The effects of DILn and NODIL are the same except for the balance of scrap.

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DATA The basic IO data are given by Japanese IO Table 2005,16 the data on IS scrap by ref 13 and the data on the EoL treatment

Figure 2. Effects of avoiding dilution- and quality losses for a car. Possible reduction in % against the default case where EAF requires dilution, and scrap recovered from ELV is used in EAF. “A−B” refers to the difference in the effects between scenarios A and B. For instance, the sum of the two left-hand areas that are painted in blue and red represents the result for NODIL relative to DILp. 9270

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Figure 3. Effects of avoiding dilution and quality losses implemented for 4 million ELVs. Possible reduction (%) of alternative scenarios against the national total. See Figure 2 for the notations.

national average pattern for Japan indicate a smaller input of pig iron and a larger input of IS scrap than those that correspond to the default scenario in the above calculation. It is thus indicated that the national average of copper (and presumably tin) contamination of IS scrap is less serious than the case of IS scrap from ELV, thanks to the supply of “clean” scrap from other sources (ref 29 discusses the copper content of scraps from ELV, construction and machinery). In other words, ELV scrap is one of the major sources of copper contaminants of IS scrap in Japan. However, there is no reason to be optimistic that enough supply of clean scrap will remain available in the foreseeable future. On the contrary, it is likely that owing to the use of more sophisticated ferrous alloys in cars and appliances, the degree of contamination will increase in the future.29 It will then be of significant interest to identify the real losses associated with the recycling of the 4 million or so ELVs that are discarded every year in Japan.14 Evaluation of the nationwide effects in the above sense calls for some changes in the functional unit. First, the number of cars purchased, fcar, needs to be altered to the actual value for the year 2005, which was around 9 million.16 Second, the number of ELV was set to 4 million. Third, the amounts of new and old IS scrap were obtained by eqs 1 and 8, with all the remaining elements of the final demand vector, including that for the extra EAF steel, being set equal to zero. Finally, the elements of aEAF, aELV, gEAF and gELV, and the final demand for the extra EAF steel were obtained in the same way as the one car case. The results are given in Figure 3 in the form of rates of change relative to the national total of respective environmental items (detailed results are given in SI Table S6). For instance, “DILpn-DILp” for CO2 emission was obtained by first calculating the percentage of emission under each of the two scenarios, DILpn and DILp, against the total Japanese emission and then subtracting the percentages. Avoidance of dilution could result in a saving at the national level in pig iron production of around 1.4% and in the demand for energy of around 0.2%. Additional avoidance of the quality loss of shredded scrap could result in the additional saving of pig iron

process by ref 26. The effects of alternative scenarios are evaluated in terms of GHG, energy requirements, and the production of pig iron. 3EID27 provided inventory data on GHG (CO2) and energy that are compatible with the IO data. Our focus on CO2 is based on its dominant share (around 95%) in the total emission of GHG in Japan.28

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RESULTS

Effects Associated with the Production and Recycling of a Car. Figure 2 shows the results in terms of the difference in percent between two adjacent scenarios. For each part of the bars, the length of the color shows the difference in results obtained under the two scenarios indicated (detailed results are given in SI Table S5). Across the scenarios, avoidance of the losses had the largest effects for the production of pig iron. It could be saved by 33% if dilution losses are avoided, by an additional 32% if the quality loss of shredded scrap is avoided, and by an additional 22%, if in addition to that the quality loss of disassembled scrap is also avoided. It is important to note that this result is based on the assumption that the reservoir of IS scrap is large enough to accommodate the existing demand for EAF material. Conditional on this, an increased use of scrap in a BOF would reduce the production of pig iron, exactly in accordance with the endof-life recycling approach.22 In the event of the absence of all the losses, the production of pig iron associated with the production and recycling of a car could be saved by around 87%, and the energy requirement as well as the emission of CO2 by around 35−38%. In other words, neglect of these losses in LCA calculation leads to overestimation of the emission reducing effects of IS scrap recycling from an ELV by more than 30%. The removal of all losses does not reduce the need for pig iron by 100% owing to the reuse of parts/components, the effects of which are not considered in this paper, and the losses in production and EoL processes. Effects Associated with the Production of 9 Million New Cars and the Treatment of 4 Million ELVs. The above results indicate that the recycling of IS scrap recovered from an ELV is characterized by the presence of dilution- and quality losses. The actual IO coefficients of EAF that correspond to the 9271

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dynamic flow of materials embedded in cars addressing these factors explicitly by means of lifetime-, weight- and material composition distribution functions.30 Consideration of these important distributional aspects within the hybrid modeling would be another important subject for future research. This paper is closed by a remark about its relevance to the overall trend of recycling policy in Japan. Meeting quantitative recycling targets of materials from EoL products has been the major focus of recycling policies in Japan.31 For instance, while the Home Appliance Recycling Law sets recycling targets for large waste electrical and electronic equipment (WEEE), little attention is paid to the quality of “recovered materials”, except for their conformity with environmental regulations. The Japanese ELV Recycling Law is focused on the proper treatments of airbags, air-conditioner coolants, and shredding residues. Recycling of metals is outside the scope of the Law because the recycling system is already well established and is functioning, at least, quantitatively. What is likely to become a turning point in these quantity oriented recycling policies is a planned new law to promote the recycling of small WEEE32 that focuses on the recovery of scarce metals. It can be regarded as the first legislation in Japan that is directly concerned with the quality of secondary materials, and hence a shift in recycling policy toward quality. The viewpoint and the methodology presented in this paper are thus very much in accordance with this shift in Japanese recycling policy.

of around 2%, and 0.3−0.4% for energy and emission. In the ultimate event of a complete avoidance of dilution- and quality losses, the saving could be around 4.7% for pig iron production, and 0.8% to 0.9% for energy and CO2. In view of the fact that under the Kyoto Protocol Japan was committed to reduce her emission of GHG by 6% relative to the level of her emission in the year 1990, the magnitude of this possible reduction is substantial.

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DISCUSSION Reduction in dilution- and quality losses could be achieved by, among others, an improvement in sorting technology, implementation of design for recycling/disassembly, and the introduction of an easier way to identify the chemical properties of secondary materials. Improvement in sorting technology would require an increase in the use of some inputs, say, electricity and fuel, for the realization of its improved performance. A sensitivity analysis was conducted to assess the extents to which the above results can be affected by a hypothetical increase in the input of electricity and fuels that are required under improved sorting technology. A rather extreme case was considered where these inputs are increased by 100% for NODIL, 200% for QLTYs, and 300% for QLTYa. It turned out that the results were not sensible to these changes: the change to the above result was less than 1.6% even for QLTa. Improvement in the quality of recovered secondary materials results in a shift in their use from an open cycle loop to a closed one. Associated with this shift, however, is the fact that a lesser amount of secondary materials will be available for the original users that were participating in the open loop. It is then of interest to consider if a closed-loop recycling of IS scrap recovered from 4 million ELVs is feasible from the point of view of the overall balance of IS scrap in Japan (the balance for the case of one car is discussed in SI). It turned out that under NODIL there would be an excess demand for IS scrap by the amount of 0.18 × 109 kg (SI Table S6). The excess demand attains its largest value of around 2.9 × 109 kg under QLTYa. In and around the year 2005, Japan was exporting IS scrap of around 7.6 × 109 kg.13 Accordingly, there was no indication of a shortage in the domestic supply of IS scrap. The supply of IS scrap from sources other than ELV is large enough to accommodate the possible shift in the use pattern of IS scrap of ELV origin due to improvements in quality. In an international context, however, the reduced export potential of Japanese scrap could have non-negligible effects in the flow of ferrous materials, among others, in China and South Korea,29 which could be an interesting subject for future research. Our analysis of the flow of recyclates was based on the material composition and weight of a representative ELV obtained from a sample of six ELVs. The possibility of their variation over time and across models was not considered. Also neglected was the dynamic process in which newly produced cars are added to the stock of cars in use and ELVs are discarded over time. These simplifications were made in order to focus on our main aim, the development of a new hybrid model to deal with the issue of losses in recycling. In reality, changing regulation on safety, consumer demands on comfort, and the reduction of fuel consumption, among others, continuously changes the material composition and weight of cars, with significant variation across car models.30 Van Schaik and Reuter developed a rigorous mathematical model of the

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ASSOCIATED CONTENT

S Supporting Information *

Data and results on permissible levels of copper and tin in steel products, use patterns of ferrous materials, ferrous materials composition of a car, metal composition of disassembled automobile parts/components and their treatment, effects associated with the production and recycling of a car, the results of implementation to 4 million ELVs. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by Waseda University through University Research Initiatives (10b-07), by JSPS KAKENHI (22360386), and by The Iron and Steel Institute Japan (Research Group for Automobile Recycling from the Material Industries’ Perspective).

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REFERENCES

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