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Journal of Cleaner Production 17 (2009) 26–35

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Journal of Cleaner Production

journal homepage: www.elsevier .com/locate/ jc lepro

Material hygiene: improving recycling of WEEE demonstrated on dishwashers

Jan Johansson, Conrad Luttropp *

Machine Design KTH, SE-10044 Stockholm, Sweden

a r t i c l e i n f o

Article history:Received 26 June 2007Received in revised form 21 February 2008Accepted 21 February 2008Available online 28 April 2008

Keywords:RecyclingDesignMaterial hygieneEcoDesign

* Corresponding author. Tel.: þ46 8 7907497; fax:E-mail address: conrad@md.kth.se (C. Luttropp).

0959-6526/$ – see front matter � 2008 Elsevier Ltd.doi:10.1016/j.jclepro.2008.02.010

a b s t r a c t

There must be a change in attitude towards end-of-life products. The view that these products posea liability must be changed. Secondary material is valuable as raw material. Thus, activities encouragingchanges in opinion are important.Two major EU directives guide the recycling process; the Directive of End-of-Life Vehicles (ELV) and theDirective of Waste Electrical and Electronic Equipment (WEEE). Both focus on the input of the recyclingsystem, not on what is coming out of the system.The WEEE Directive is the legislation on the European level that governs the handling and processing ofthese types of products. The WEEE Directive is not only aimed at stricter handling and reduction ofhazardous materials but also encourages EU member states to support technical development in order tofacilitate increased recycling.In order to properly address these issues a mind-set, material hygiene, has been introduced. The basicidea is to act, in every life cycle phase of the product, towards highest possible efficiency in recycling. Theoutcome of useful material is in focus.A study on dishwashers is made with copper outcome as target. The results are based on Swedishconditions but general conclusions can be made. Limited design efforts can raise the outcome of valuablematerials, if the recycling process is organized in an optimal manner.A theoretical concept of disassembly structures is used to draw general conclusions on the case study.Increasing product recycling suitability is one side of the problem; another is increasing effectiveness ofhandling and processing of end-of-life products.The purpose of this paper is to introduce the concept of ‘‘material hygiene’’ and based on that demon-strate a method for grading structural properties in a recycling perspective. The findings presented in thispaper are based on a field study in which a number of dishwashers were disassembled and analyzed.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Increasing demands for materials and energy raise resourceprices. Together with new environmental demands and stricterlegislation, recycling is coming more and more in focus.

Two major EU directives guide the recycling process; theDirective of Waste Electrical and Electronic Equipment (WEEE) [1]and Directive of End-of-Life Vehicles (ELV) [2]. Both directives focuson the input side of recycling. ELV states that by 2015 end-of-lifeautomotives should be recycled to 95%. WEEE states collectiongoals, how much to collect on a per capita basis. The output side ofrecycling is sparsely addressed. No one seems to know how muchmaterial that comes out of the process. No one seems to know howmuch of this material that is pure enough to be put back ina product on the same level as before. No one seems to know thetrue efficiency of recycling processes. Especially the WEEE Directive

þ46 8 202287.

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is implemented in various ways, from country to country. Even inthe same country one can spot different approaches on WEEErecycling. In Sweden some recycling sites disassemble beforeshredding. Different machines are used such as hammer mills,hurricane machines, ring mills or roller knifes. Sometimes WEEE isprocessed exclusively in so-called campaigns with hand pickingafter shredding.

Recycling companies often have their own homemade processand there is no common surveillance on the outcome of recycling.Especially recycling efficiency in terms of amounts of pure materialout compared to input is not quite clear.

With a metaphor:

When it comes to recycling yield, we measure what the cow eatsbut we don’t really measure what the cow produces.

This problem can be solved by preparing products for recyclingin the design phase and to industrialize the end-of-life process ofproducts. Design can facilitate disassembly pre-steps beforeshredding and different fractioning processes can raise the out-come and purity of valuable fractions.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–35 27

The WEEE Directive stipulates special requirements for electricand electronic equipment and the ELV Directive puts similardemands on car recycling. However, there are discrepancies whencomparing these two directives. An electronic subassembly withinan ELV may very well be comparable with an electronic productcovered by the WEEE Directive but demands are different. Forinstance, a printed circuit board (PCB) in a dishwasher must, if thearea exceeds 10 cm2, be removed according to the WEEE Directive,but not according to ELV.

In the future one can expect a harmonization between these twodirectives in order to maintain credibility towards producers.

The current practice in recycling needs support to increase theamount of recycled valuable and precious materials. Decreasing therisk of diluting these materials to levels so low that no recovery isfeasible is beneficial in both a recycling and economic perspective.

2. Recycling research and process

The process of material recovery starts at the collection facility.Proper handling throughout storage and transportation facilitateincreased yield in the process. The next step is dismantling andsorting of toxic waste and valuable parts or subassemblies inrelevant fractions; ‘‘Fractioning I’’ in Fig. 1. This fractioning can bedone manually or automated on different levels.

A predominant part, for recycling of WEEE, is a shredder pro-cess. The shredding is sometimes preceded by a special preprocesssuch as recovery of CFC from waste refrigerators and freezers(‘‘Toxic waste’’ in Fig. 1). After shredding, fractioning is carried outwith magnetic, eddy current and/or other techniques. Large electricmotors such as the circulation pump in a dishwasher have a mag-netic stator with copper windings. These items must be handpicked at present (a part of ‘‘Fractioning II’’ in Fig. 1).

Smaller motors and wires can slip through hand pickingdepending on belt speed, concentration of WEEE and number ofhand pickers. The magnetic fraction from WEEE therefore oftencontains a large non-acceptable portion of copper.

Fig. 1. A graphic picture of how recycling is organized at present in Sweden and otherEuropean countries. Collection is followed by dismantling and other preprocesses.Secondly shredding takes place and this is followed by different post-processes inorder to create proper fractions.

Currently, necessary manual operations are carried out byskilled workers. Maintaining a qualified work force for these taskscan be difficult, mainly due to the current low status of recyclingwork. Most likely, manual labor must be phased out and newimproved automatic processes must be developed.

The Volkswagen-SiCon process is an example of a downstreamwaste treatment without any link to design [3] (‘‘Fractioning III’’ inFig. 1). The process is specialized in fractioning of After ShredderResidue, ASR or ‘‘fluff’’.

In order to raise the effectiveness in recycling, a higher degree ofindustrialization is necessary.

Dalrymple et al. [4] describe the situation in the UK where the 10waste categories in WEEE are not implemented as separate wastestreams, due to, for example space constraints at waste collectionfacilities. Current and emerging technologies to handle WEEE arepresented, such as sorting and disassembly and crushing and sep-aration. The different separation techniques used are presented. Theauthors claim that initial disassembly (see pre-step) is essential tofulfill demands for removal of toxic components as well as simpli-fication of later separation stages. Furthermore, any technologiesthat bring automation to the treatment process would improve theprocess and increase chances for financial success. A smaller par-ticle size after the shredder is highlighted as being important in theseparation of different materials. It stated in this paper that 20–25%by weight of WEEE is polymeric (which corresponds to 50% byvolume). It is a large fraction of WEEE that does not get treated wellat the recycling facility. Heat from the shredder can degrade thepolymers. Furthermore, 20% of the polymers contain brominatedflame retardants and require special attention.

In contrast there are advantages using thermal treatment whenrecycling metals. Printed circuit boards (PCB) are said to be 3% byweight of WEEE but contain 29% by weight of WEEE of valuablemetals. Burning followed by pyrometallurgical treatment canrecover metal from PCBs. This treatment requires highly specializedfacilities. Additionally, hydrometallurgical treatment is another wayof extracting metals from, for example PCBs; this technique is widelyused in treating ore. The major problem with hydrometallurgicaltreatment is the use of toxic fluids to produce waste streams.

The authors conclude with eight points:

More clear definitions in order for treatment facilities to optimizetheir operations.Development and support for the second hand materials market.Better match between collection streams and treatmenttechnologies.Education of designers on the choice of materials and the impactthose choices have on the recycling treatment.Recycling large household appliances is a good practice based highcontent of valuable materials.The RoHS Directive will influence the composition of WEEE.WEEE is constantly evolving, since new products are put on themarket and these can demand different treatment techniques thanthe current waste streams [4].The research project has so far identified existing, emerging andfuture technologies for WEEE treatment.

Based on the poor performance of weight estimates as measuresfor recyclability Huisman et al. [5] present the concept of Quotes forenvironmentally WEighted RecyclabiliTY (QWERTY) for calculatingproduct recyclability. Electronic products are the focus productgroup. These products represent complex structures from a de-composition view. Using the default weight of fractions todetermine material amount after treatment is misleading asdecomposition behavior differs. This means that the same type ofproduct containing the exact same fractions and fraction amountswould give different result after waste treatment.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–3528

The first purpose of QWERTY is to calculate for one and the sameproduct recyclability ‘‘the environmental way’’, for one or moreend-of-life treatment avenues.

The first step of this method is the quantification of the productsenvironmental impact. In order to calculate this impact thefollowing is needed:

Material composition;Percentages of the different materials in the different fractions;An impact assessment method (from the LCA methodology), forexample EcoIndicator 99;An environmental database, the authors uses Philips ConsumerElectronics database.

The second step is to determine reference values; best possibleand worst possible environmental impact case.

The third step is the difference between step 1 and 2; theQWERT score.

After the presentation of the conceptual basis case scenarios arepresented. These are shredding and separation of non-CRT browngoods, shredding and separation of CRT brown goods and shred-ding and separation of cell phones.

In the conclusion the authors states that the proposed method isuseful in giving insight the environmental impact of recycling, notonly by the product themselves but also by the treatment stepsrequired [5].

Platcheck et al. [6] target the sustainability issues of electricaland electronic products.

A brief field survey of local Brazilian e-waste concludes thatcurrent disposed products do not facilitate reuse or recycling.

A product development process methodology is presented:

Briefing phase;Development phase;Projection phase;Communication phase.

To summarize this methodology; ‘‘environmental variables’’ arehighlighted at the different stages of the product developmentprocess (as defined in the traditional German style). A Five-R con-cept is according to the authors:

‘‘to rethink on sustainability before the conception of theproducts; to return parts, components or the whole product forreuse or recycling; to reduce raw material and components; toreuse sub-systems improving disassembly and maintenance; torecycle parts of the product’’ [6].

Kriwet et al. [7] present an approach to include recyclingconsiderations into the product design process. A cooperationconcept, ‘‘recycling network’’, is introduced in order to facilitatecommunication between designers, consumers, recyclers, andsuppliers.

The authors also state that total recycling of product is notfeasible, however, maximizing the amount of recycled materialwhile minimizing the effort needed is desirable.

A multi-objective goal can only be accomplished by two means;sophisticated recycling and recycling-friendly design. Furthermore,is believed that 10–20% of the recycling cost and benefits are relatedto process optimizations. The other 80–90% is already decided bythe design of the product [7].

3. Design for recycling

The general rules for recycling oriented design are well-known,e.g. ‘‘Konstruieren recyclinggerechter technischer Produkte’’ (VDI2243) [8].

Masanet et al. [9] have developed a Design for Recyclingguideline concerning recycling of polymers. Manual and automatedrecycling technologies are examined in the US and Europe.

The authors’ makes references to ‘‘TCO ’99’’ and ‘‘Blue AngelRAZ-UL 78’’ as eco-labels. Six different guidelines are presented andtied to the eco-labeling schemes.

Suggestions and benefits/targets:

1. Plastic components (>25 g) should be labeled (ISO11469), forvisual identification;

2. All plastic components (>100 g) should be made of the sametype of material to increasing volumes of similar plastics;

3. Paint should not exceed 1% of the total plastic component(>25 g) weight thus minimizing the adverse effect (mechanicaland aesthetic) paint can have on recycled plastic;

4. No metallization of plastic components, no molded-in orglued-on metal parts. Avoiding metal in recycled plastic due topossible hinder in the recycling process;

5. Components of the same material should have the same color;6. At least half of the separable connections should be snap-fits in

order to decrease disassembly times [9].

A method is developed by Luttropp on Design for Disassem-bly with an analyzing and synthesizing tool where productcomponents are in focus. Section 4 is a brief subset of this work[10].

Many methods have been developed over the years on EcoDe-sign in general and on design for recycling or disassembly. How-ever, all these methods are often too complicated and there isa need for practical, simple guidelines that can be used by industryin daily work [11].

At the department of Machine Design at the Royal Institute ofTechnology (KTH) a simple tool called Ten Golden Rules is de-veloped involving the whole life cycle of a product including end-of-life in order to maximize the benefit of recycling [12].

A very important field for recycling is remanufacturing. Sundinhas covered this in his PhD thesis from 2004. In refurbishing thegoal is to prolong the life of used products. In the case studiesmainly guarantee repairs were studied and typically products weremalfunctioning in early or mid-life. Instead of repair on site, onproducts still under guarantee, the products were transported toa repair plant where they were repaired and afterwards solda second time. The author also advices how to improve design of,e.g. washing machines in order to facilitate upgrading and repair[13].

However, the scope of our paper is material recycling at end-of-life and if the goal is to gain as much material as possible and as pureas possible from a process, it is not necessary to use reversible ac-tions, which is a prerequisite for upgrading and repair.

The benefit of few fractions in recycling is obvious as well as thebenefit of a clear and obvious layout of a complex product. Thisstated already 1993 in VDI 2243 [8].

The Volvo S80 dismantling handbook advices how to disas-semble and sort a Volvo S80 and this of course interesting forcannibalizing of fairly new but broken automotives [14]. How-ever, in materials recycling reversibility is not so beneficialcompared to a clear layout with easy access to relevantfractions.

The IVF handbook on environmentally adapted design states thebenefit of few materials and a simple layout but also the benefit ofa clear layout and standardized parts [15].

Kuuva and Airila [16] make eight statements on design forrecycling:

� minimize the number of parts;� standardize and use modular constructions;

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–35 29

� place the components in logical groups according to theirintended recycling strategy and the handling sequence in thedisassembly process;� avoid integral constructions and unnecessary combinations of

different materials;� reduce the number of non-recyclable materials and

components;� ensure that the coatings, paints, etc. that are used do not

present any problems;� make the joints, gripping points, breaking points, etc. easily

accessible;� ensure that the disassembly can be made with conventional

tools and equipment without special arrangements;� provide a technique to safely dispose of hazardous waste

possibly found in the product [16].

Kirby states the importance of material selection, fewer mate-rials and coding as well as recommendations on labeling andrecycling-friendly joining [17].

The Volvo handbook for designers, being a forerunner in auto-motive EcoDesign, contains a chapter on design for recycling [18].

4. The material management concept of material hygiene

Material hygiene (MH) is a conceptual metaphor for treatmentof materials in the product life cycle. MH is associated with treat-ment of provisions like meat, vegetables, canned food, etc., andunbroken chain of a cold environment, origin of production, list ofcontents, etc.

The concept of material hygiene is focused on optimizing thereuse of materials in products.

Our definition:

MH is to, in every step of the product life cycle to act towards largeramounts and increased purity of useful material from recycling,possible to use on the same quality level as before or degraded aslittle as possible.

This concept does not exclude the possibility of remanu-facturing as expressed by Steinhilper [19] or Sundin [13]. For MH,especially the end-of-life phase is in focus. A high-level of ma-terial hygiene means a high-degree of effectiveness in materialsuse. The necessary changes towards higher MH should beimplemented early in the design process when design freedomstill exists. Additional changes in the production will only be ofa superficial nature.

The goal is to design products in such a way that as much aspossible of used material is kept in the eco-cycle and used in themost effective way.

An often-cited concept is the cradle to cradle concept. The originis ascribed to Walter Stahl. However, McDonough and Braungarthave written a book on the cradle to cradle concept based on theirpersonal experience from eco-projects and their idea of biologicaland industrial cycles, earlier presented in a paper ‘‘The nextindustrial revolution’’ [20]. The basic idea is to keep the biologicaleco-cycle and the industrial eco-cycle apart [21]. This conceptmight preserve nature but the main idea with MH is to separate theindustrial cycle into useful fractions of different materials that canbe used on the same value level as before.

The RoHS directive [22] and the new legislation on chemicalsREACH [23] will of course affect WEEE and ELV in the sense thatproducts will in the future not contain certain substances bannedby RoHS or restricted via REACH. The MH perspective here is tosecure that materials restricted by REACH are easy to recycle safelyand if suitable reuse in same position as before. RoHS substancesshould not be there at all and by this eliminate a MH problem oftoday.

With a high level of MH it will be easier in the future to extractsubstances that were allowed at time of manufacturing but whichlater have proven to be toxic.

The following five areas are especially important in an MHperspective in line with the definition above:

The material mix;The layout structure;Identification possibilities;Resource preservation;The weight of products and subassemblies.

The next five sections present the five material hygiene (MH)factors.

4.1. MH mix

The mix of materials is essential for recycling efficiency. Thisimplies a reduction in numbers of materials used, both in terms ofnumber of materials and number of parts out of each fraction. Thenumber of material used in a product influences the possibility ofachieving clean fractions at time of recycling.

But, one can state that a high-number of properly separatedmaterials are better than two different materials hopelesslyentwined. Emphasis should lie on keeping used fractions as sepa-rated as possible and avoiding unnecessary alloys.

4.2. MH map

A simple and visible structure for parts, joints and sub-assemblies, well-documented, possible to read ocularly or bytechnical means, promotes repair, upgrading and recycling.

As implied in prior factor definitions the need for clear and well-defined structure is important. Many recycling problems can beavoided by relatively small changes in design. The insight that reuseof components or recycling of material is required at end-of-life isa challenge for designers.

4.3. MH identification

This is important for recycling logistics with questions such as:What is inside the product? How should the product be handled?Who is the producer? Is the product under some legislation? Whatis the value of the product in material and or economic funding?, etc.

From a recycling process point of view, color labeling could beused in combination with a vision system and a robotic solution forseparating fractions. The product label could be, in order to handlelarge amount of products, a type of radio frequency identificationdevice (RFID). The information possible to receive from an RFIDcould, for instance, be product number and spatial placement ofcopper hotspots.

4.4. MH resource

Keeping documentation on scarce and toxic materials is goodpractice and is in most cases required. The RoHS directive defines atpresent six materials that are forbidden to use within the EuropeanUnion marketplace. Substances not included in RoHS but still toxicor scarce and may be under REACH restrictions, might be requiredto achieve certain functionality. In such cases, good documentationshould follow the product through its life cycle. Replacement ofmaterials should be carried out with a systems view; there isalways a risk that toxic material, well-documented and controlled,is replaced with a substance with perceived better characteristicsthat in the end is just slightly better.

Fig. 2. A product can be regarded as a set of modules where each module consists ofa homogenous piece of material, a useful subassembly, etc. Each of these objects hasone or several surfaces where the object is connected or joined to other objects. Theseparating surfaces are held together by ‘‘resting load cases’’ which are ‘‘sleeping’’ untilthe disassembly moment. All joints that can be released during disassembly are‘‘resting load cases’’ since these joints are released by applying a force of some kind ina new way that is not present during service life of the product.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–3530

4.5. MH weight

Weight issues are in this context connected to designingstructures that lend themselves to rational disassembly. That is,there are cases where additional weight may be required in order tobe able to successfully remove certain parts. Low vehicle weight ispositive in the sense that fuel consumption is lowered but if lifelength is shortened there can be a total loss when these two factorsare combined.

Contradictions between the MH elements are the rule ratherthan the exception, giving a trade-off situation in most cases. Aproduct with a high-degree of MH has a balanced and optimized setof factor values.

5. Recycling structure of products

This section is a subset of a theory developed by Luttropp [10].The recycling structure of a product consists of pieces of

homogenous materials, useful subassemblies, and parts for recon-ditioning, upgrading, energy recovery or deposit.

The product can then be regarded as a set of modules whereeach object or module consists of a homogenous piece of material,a useful subassembly, etc. Each of these objects has one or severalsurfaces where the object is connected or joined to other objects.These surfaces are called separating surfaces and indicate theborder between modules. If the module is possible to identify andpossible to use, it is surrounded by a sorting border. The separatingsurfaces are held together by resting load cases which are sleepinguntil the disassembly moment. Sometimes the resting load casesare the same as the assembly load case, like when unscrewinga screw. In other cases it can be destructive separation at a breakingpoint, as shown in Fig. 2.

Accepting these structural functions features and principlessome statements can be made. The recycling structure of a productcan be regarded as a set of sorting borders, separating surfaces andresting load cases.

5.1. Five structural families

The concepts of ‘‘sorting border’’, ‘‘separating surface’’ and‘‘resting load case’’ can be used to describe the inner workings ofa product. A set of these can be used to describe a whole product.These products could then be arranged into families.

Finding structural layouts that support disassembly with a high-degree of recycling, either piece by piece or through shredding isthe challenge. Two products can contain the same type of parts andhave the same functions but have radically different structurallayout. Thus, some products will have beneficial properties ina recycling perspective.

Products can be divided into different categories based onstructural layout of included parts. Such a division, made byLuttropp [10], based on relatively small products, cell phones,toasters, etc., presented the following categories, see Fig. 3:

Hamburger design;Shell design;Rod design;Twin design;Dressed design.

5.1.1. Hamburger designThese kinds of products have a casing in two halves, often

plastic, which lock-in and hold the interior, like transmission,motor, cables, supporting parts, printed circuit board, etc.

Typical products: mobile telephone, drilling machine, toy car,and remote control for home electronics.

1st Step¼ one non-destructive load case to open the casing;2nd Step¼ sorting.

5.1.2. Shell designThe casing of these kinds of products has a closed shell structure

with a smaller entrance into the shell than the main overall productdimension.

Typical products: flashlight, ammunition, electrical toothbrush,fuel tank, gearbox, and hydraulic jack.

The disassembly sequence is:

1st Step¼ one destructive load case to open the casing;2nd Step¼ sorting.

5.1.3. Rod designThis product family has the characteristics of one or several

pieces of the same homogenous material and this ‘‘material body’’is of main interest when it comes to recycling.

Typical products: screw, screwdriver, pliers, pipes for water, andtelevision antenna.

The disassembly sequence is:

1st Step¼ sorting.

5.1.4. Twin designIn this case there is more than one important sorting object on

the first sorting level and the load case for this first level should bedesigned with great care.

Typical products: water tap, water closet, pieces of furniturewith tubular legs, works of a clock, jewelry, and car wheel.

Fig. 3. The five structural families with shell up left, hamburger up mid, twin up right, rod down left and dressed down right.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–35 31

The disassembly sequence is:

1st Step¼ separation of fractions;2nd Step¼ sorting.

Table 1Joint load case indices

Information Li : 0 – easy to understand, 1 – almost impossible to understandEquipment Lq : 0 – no tools needed, 1 – special tools neededForce Lf : 0 – just fingers needed, 1 – power tools neededTime Lt : 0 – less than 10 s, 1 – more than 30 s needed

5.1.5. Dressed designThese products are characterized by a carrier on which nearly

all components are mounted and around this there is a cover/housing just as a protection and mostly with no other function.The first level of disassembly is always to remove the casing andtherefore this operation should be given a good non-destructiveload case. The sorting border for the casing is most of the timequite natural.

Typical products: toaster, computer, audio equipment, and car.The disassembly sequence is:

1st Step¼ one load case to open the casing;2nd Step¼ disassembly;3rd Step¼ sorting.

The carrier with the mounted parts contains a variety of dif-ferent load cases, destructive and non-destructive. This kind ofdesign gives the opportunity to pick valuable components andleave components or subassemblies of minor interest. Parts tobe taken care of that are mounted on the carrier should havegood sorting border layout. They should be easy to identify andseparate.

This is a traditional layout for products with a lot of manualassembly work and this type of designs is common when there arelarge empty spaces inside the product. Complex products, planes,cars, etc. most likely contain all of the design types specified. Whendesigners try to make a certain product smaller Dressed designs can

be transformed into Hamburger designs. When expressingrelations between parts in a product, DfDS can be used.

5.2. Design for Disassembly Structure (DfDS)

Design for Disassembly Structure (DfDS) is the name of thesubdomain of DfD that deals with product structure description.One way of expressing these relations can be by using a graphicalrepresentation as introduced by Luttropp [10]. This methodintroduces the concept of describing joints as resting load cases.These load cases can be graded, in an ordinal scale, on in-formation needed to understand how to disassemble and howmuch equipment, force and time needed for the operation, seeTable 1.

Using a structural in–out approach, copper-containing parts couldbe seen as parts of the ‘‘copper-subassembly’’. This subassemblyshould have strong connections inside the assembly and weak con-nections to neighboring subassemblies. Lf should be higher within thecopper-subassembly than outside using the notation in Table 1. Thisimplies that when forcefully removing the ‘‘copper core/squid’’ theprobability that only this subassembly will be released is increased.

Fig. 4 below, exemplifies this method by the use of a de-pendency tree.

The dependency tree method is intended to be used in a settingwhere management and designers together define and gradeconnection strength during discussion sessions.

Tub

Li=0Lt=1Lf=0.5

Li=0Lt=1Lf=0.5

Li=0.25Lt=1Lf=0.5

Motor (Circulation Pump)

Rubberseal

Undercarriage

Rotary Switch(Microprocessor)

3x

Joint connections

Contact only

Cable

Li=0.25Lt=1Lf=0.5

3x

Fig. 4. Dependency tree visualizing connections between motor and surroundingcomponents.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–3532

A dotted line represents only connection by contact. Full linesexpress joint connection, for instance, a screw joint.

All grading is performed from an operator point of view. Threelevels of operator knowledge are defined: high expert, experiencedscrapper and home user. The indices are defined by using an ordinalscale, zero to one.

Given a disassembled dishwasher, the structure has beengraded. The focus is on copper-containing parts. The connection tothe most copper-intensive part, e.g. motor is displayed in Fig. 4.

6. Case study: dishwashers at end-of-life

The dishwasher was chosen as demonstrator product familybecause of its relatively small number of components and thecomponent similarity between brands. A dishwasher containslargely the same type of details; the defining difference is the layoutand assembly of these details.

A field study has been carried out to determine the properties ofdifferent dishwashers in a recycling perspective. Dishwashers rangein size from small bench type to full size floor standing. Two dish-washers of bench type were included and one of the narrow (40 cmwidth) type, and all other dishwashers were full-sized (60 cmwidth). Which are the typical dishwashers on the Swedish market.

Ages span from 10 to 15 years which is the approximate lifeexpectancy of a dishwasher. Three of the dishwashers were also ofthe free-standing type, which implies that they have a cover ofsheet metal. A dishwasher of any brand typically consists of 40–50parts, excluding screws and bolts.

6.1. Goal and scope of field study

One of the questions raised was: is there a type (brand) ofdishwasher in the current waste stream that has good recyclingproperties? Copper has been chosen as example material in thisstudy. Copper is a powerful demonstrator in the sense that it is botha valuable metal on its own and a contaminant in high-grade steelproduction [24]. Moreover, the price of copper in the world markethas been increasing steadily [25] the last 5–6 years. At the end of

2006 there was a drastic decrease in the price of copper ore. Thefactors responsible for this decrease are not entirely mapped.

In addition, electronic scrap represents the largest secondarycopper resource of old scrap [26]. Therefore, all detailed operationsrefer to copper removal if not otherwise stated. Assuming that theelectrical motors (in a dishwasher) are parts that are highly copper-intensive and in turn connect to other copper-containing parts, e.g.the wiring.

Based on this assumption the motor-circulation pump assemblyhas been designated a target part when planning possible disas-sembly operations.

6.2. Dishwasher study method

From the current scrap flow in Stockholm, Sweden, 14 dish-washers were selected with help from Mr. Alf Hedin, a representa-tive from El-kretsen AB [27]. This company, owned by 21 businessgroups, has the responsibility for collection and treatment of Wasteof Electric and Electronic Equipment (WEEE) in Sweden.

Selection criteria were firstly market share and secondlyinteresting design solutions.

Furthermore, a spread in brands and production places was alsoreflected in the choice.

The disassembly study was conducted at a disposal plant northof Stockholm, Sweden from 1/9/2005 to 1/12/2005.

The dishwashers were manually disassembled. Documentationtechniques used in the study included photography and manualnotes.

The manual disassembly was conducted using only hand tools,e.g. screwdrivers and pliers. No power tools of any kind were used.Parts were gathered, counted and if they carried markings con-cerning material content this was noted.

The stainless steel fraction and the sheet metal fraction werethen weighed. Important steps were photographed. Interestingdesign features were also documented this way.

The disassembly sequence started with a survey of the specificdishwasher. The sequence was roughly front-to-back and top-to-bottom. Identification of locations of nuts and screws and in the free-standing case the process started with removal of the cover sheetmetal. Front door removal includes removal of hinges and discon-nection of wiring. The wiring connects control panel and detergentcase to various electrical components under the dishwasher. Thewiring is guided through a plastic ‘‘tunnel’’ between door and chassis.

This is a solution used in almost all the selected dishwashers.

6.3. Dishwasher study result

Dishwasher design is of dressed type (c.f. Section 5.1.5), butcontains subassemblies from the other types as well. The design ofdishwashers in the study could roughly be divided into two cate-gories: those which feature a polymer sump type design and thosewhich do not. The last alternative, which is most common, is thatthe dishwashers features a sump integrated into the stainless steeltub bottom. Holes in the bottom then connected to the pumpsthrough rubber or polymer hoses.

The use of a polymer sump with integrated pumps and motors isconsidered beneficial when planning for a manual or automaticdisassembly operation. This kind of design keeps copper-intensecomponents close to one another, making it easy to extract copper-intense parts in one operation. Since most components are notcandidates for reuse destructive disassembly is a probable option.

A typical dishwasher contains approximately 1 kg of copperdistributed in four subassemblies:

Circulation pump motor – 700 gDrain pump motor – 100 gWiring – 100 g

100

90

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70

60

50

40

30

20

10

00 1 2 3 4 5

Copper yield [%]

Time [min]

A

B

C

A1

A2B1

B2

C1C2

Fig. 5. Copper outcome versus time of manual work on object. The marked positionsA, B and C, and the correlated outcome, 100%, 75% and 20% are defined to representthree distinct dishwashers.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–35 33

Electronic components – 100 g

The distribution presented above should be considered to be anaverage of a population of dishwashers, not a particular model orbrand. Based on this distribution, the copper recycling can beconsidered to have binary properties, i.e. either remove it or do not.

In the study, typically 5 min of work gained about 75% of thecopper and therefore this was used as datum. With some designefforts dishwashers could be disassembly prepared and could befully copper removed in approximately 2 min. For some dish-washers 5 min are not enough to remove the main copper source,the motor. This last type represents the most recycling unfriendlydishwashers.

Based on these results three different levels are defined basedon relative copper removal. These levels are contemplated tocorrespond to worst, best and a normal case.

DWf20 – Drain pump motor and part of wiring are removed.Twenty percent copper is removed;DWf75 – Circulation pump motor and part of wiring are removed.Seventy-five percent copper is removed;DWf95 – Circulation pump motor, drain pump motor and all wiringare removed. Ninety-five percent copper removal. This is defined astotal removal of copper with a 5% loss ratio. The performance inrecycling as defined in these three categories of dishwashers is toa large extent dependent on design activities.

Based on the previously defined levels the following sectionsinclude a more comprehensive definition, where these levels arerelated to design features and pre-step operations.

To achieve DWf95 level the dishwasher must be prepared fora pre-step operation. That is, wiring must be designed to allow easyaccess and have joints that break or release at the correct position.The correct positions, in this context, would be where electronicequipment is fastened to the stainless steel tub and surroundingsheet metal. Therefore, pulling the wiring would release not onlythe wiring itself but also the part it connects to.

At DWf75 level the dishwasher would not be required to bedesigned for a pre-step per se. Given the layout of the over-whelming majority of dishwashers in the study, reaching theposition of the main motor is relatively easy and would enableremoval of the majority of the copper. This level aims to remove themost copper-intensive part, the circulation pump motor, and alongthe way some of the wiring will also be released. This operation willalmost certainly be performed destructively.

At DWf20 level the circulation pump is difficult to remove andinside 5 min of work just the drain pump and some wiring ispossible to remove inside 5 min of work.

The difference between DWf75 and DWf20 is that it is con-templated that the DWf20 is a more complex product in terms ofinternal structure.

A grading scheme based on the disassembly study has beencreated by defining probable disassembly time.

Point A: in Fig. 5 prepared dishwasher where a single operationwill remove almost all copper in the dishwasher after 1 min ofwork. Point B: not prepared but fairly well-suited for copperremoval; time 3 min. Point C: neither prepared nor suited and fairlylow amounts of copper removed in 5 min of work.

The maximum time allowed for disassembly of copper has beenset to 5 min due to economic considerations.

Curves A1–C1 represent a more generic and theoretical outcomeof copper removal in recycling. The scenarios A2–C2 are moreadapted to the real case in the dishwasher study. Curve B2 repre-sents a dishwasher where it takes 2 min to remove the circulationpump and after one extra minute some wiring will be removed aswell.

The marked positions A, B and C, in Fig. 6, and the correlatedoutcome, 100%, 75% and 20%, respectively, are defined to representthree distinct dishwashers.

Points A–C represent different dishwashers from a copper yieldpoint of view. The possibility to remove copper is presented relativeto the time required.

Point A; is the ideal case. A dishwasher that demands a 1-minoperation resulting in total copper removal would be A.

Curves A1–C1 must be seen as the outcome from a large numberof dishwashers, since observing one dishwasher would producea step–curve shape. It is also possible, in selected dishwashers, toachieve a convex or concave curve depending on product structure.

When applying the grading scheme presented above on thedisassembled dishwashers from the field study they would bepositioned in the area D between B and C depending on designfeatures, see Fig. 6.

One could state that dishwasher disassembly at the present timeis limited due to the fact that when they were built the end-of-lifephase was not taken into consideration, to reach the A levelnecessary design features must be implemented at an early phase.

To reach definite conclusions regarding this, a separate studywill have to be launched with this specific objective.

Copper has been identified as a target material in this study butthe general concept can be focused on some other interesting ormaybe dangerous material. The copper-subassembly removalwould be facilitated by implementing continuously falling restingload case strength. This means that the separating force on eachjoining between copper parts should be higher that the neededforce to separate copper from other parts. This way the copperfraction could be seen as a body of copper with a strong internalcohesion, see Fig. 7.

This means that an effort to design connections and jointsshould be made with regard to spatial conditions.

7. Discussion and conclusions

The introduction of one operation before shredding is consid-ered to be beneficial [28]. This suggestion is the essence of thisstudy towards the goal of finding ways to increase material recy-cling. The use of a manual operation is believed by the authors to beviable in a number of aspects including economic. Given the price

100

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30

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00 1 2 3 4 5

Copper yield [%]

Time [min]

A

B

C

A1

A2B1

B2

C1C2

Fig. 6. Copper outcome versus time of manual work on object. The gray area betweenpoint B and C represents dishwashers included in the case study.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–3534

of copper scrap one can based on economic reasons justify a pre-step operation.

In the specific dishwasher case the pre-step operation couldinclude removal of the sump, which would create a separate wastestream consisting of pump and motors connected to a plastic house.If this approach is not feasible, separate removal of motor (pump)and the wiring would accomplish the same result.

In the dishwasher field study presented in this paper, all MH-factors play a role. The generality of these factors extends beyondWEEE type scrap which is the focus product group in this study. Inorder to get reliable results, grading is essential.

It is important to identify drivers for increasing the MH-level.For instance, if there were design features that simplified both as-sembly and disassembly the likelihood would be greatly improved.

Using the proposed methods will increase the amount of recy-cled material.

Fig. 7. A schematic illustration of the ‘‘copper core/squid’’ for a dishwasher. The cir-culation pump motor, drain pump motor, wiring, and electronic components forma copper module where the joining strength inside is higher than the connectionstrength between copper parts and the environment inside the dishwasher.

The proposed methods are a first step towards a system tofacilitate grading and suggestions for better design in a recyclingperspective.

It is in the authors’ view inevitable that some methods will berequired in the near future to address issues concerning effectiverecycling. Increasing the marking of products is essential in orderto achieve an industrialized system at the end-of-life fora product.

The producer responsibility expressed in the WEEE directiveis important from a number of aspects. In order to drive thedesigns of products towards recycling-friendly products at end-of-life, there must be some feed-back from the recyclingindustry. This information flow is another challenge for thefuture.

Acknowledgements

The financial support from The Foundation for Strategic Envi-ronmental Research, MISTRA, is gratefully acknowledged. Further,the help in dishwasher selection from Mr. Alf Hedin Electrolux andEl-kretsen is also acknowledged.

References

[1] EU Directive 2002/96/EC on waste electrical and electronic equipment(WEEE); 2002.

[2] EU Directive 2000/53/EC on end-of-life vehicles; 2000.[3] Krikne S, Bossdorf-Zimmer B, Goldman D. The Volkswagen-SiCon solution for

future end-of-life vehicle treatment. In: Proceedings of 13th CIRPinternational conference on life cycle engineering; 2006. p. 359–63. Leuven,Belgium.

[4] Dalrymple I, Wright N, Kellner R, Bains N, Geraghty K, Goosey M, et al. Anintegrated approach to electronic waste (WEEE) recycling. Circuit World 2007;33(2):52–8.

[5] Huisman J, Ansems T, Feenstra L, Stevels A. The QWERTY concept, a powerfulconcept for evaluating the environmental consequences of end-of-life pro-cessing of consumer electronic products. In: 2nd International symposium onenvironmentally conscious design and inverse manufacturing; 2001. p. 929.EcoDesign’01.

[6] Platcheck ER, Schaeffer L, Kindlein Jr W, Candido LHA. Methodology ofecodesign for the development of more sustainable electro-electronicequipments. Journal of Cleaner Production 2008;16:75–86 [accessed 20.02.07].

[7] Kriwet A, Zussman E, Seliger G. Systematic integration of design-for-recyclinginto product design. International Journal of Production Economics 1995;38:15–22.

[8] VDI 2243. Konstruieren recyclinggerechter technischer Produkte. Dusseldorf,Germany: VDI-Verlag; 1993 [in German].

[9] Masanet E, Auer R, Tsuda D, Barrillot T, Baynes A. An assessment and priori-tization of ‘‘design for recycling’’ guidelines for plastic components. In:International symposium on electronics and the environment. IEEE; 2002. p.5–10.

[10] Luttropp C. Design for disassembly–environmentally adapted productdevelopment based on prepared disassembly and sorting. Doctoral Thesis KTHMachine Design, Stockholm, Sweden; 1997.

[11] Boks C. The soft side of ecodesign. Journal of Cleaner Production 2006;14:1346–56.

[12] Luttropp C, Lagerstedt J. EcoDesign and the ten golden rules: generic advicefor merging environmental aspects into product development. Journal ofCleaner Production 2006;14(15–16):1396–408. EcoDesign: What’shappening?

[13] Sundin E. Product and process design for successful remanufacturing. Link-opings Universitet; 2004. Linkoping Studies in Science and TechnologyDissertation No. 906.

[14] Volvo. Dismantling handbook S80. Gothenburg: Volvo Car Corporation;1998.

[15] Magnusson T. Handbok for Miljoanpassad mekanikkonstruktion. Molndal: IVFInstitutet for Verkstadsteknisk Forskning; 1997 [in Swedish].

[16] Kuuva M, Airila M. Design for recycling. In: International conference onengineering design, ICED 93 The Hague; 1993.

[17] Kirby JR, Wadehra I. Designing business machines for disassembly andrecycling. In: IEEE international symposium on electronics and the environ-ment; 1993. New York.

[18] Westerlund G, editor. Miljohandledning for konstruktorer. Goteborg: VolvoPersonvagnar AB; 1997 [in Swedish].

[19] Steinhilper R. Remanufacturing: the ultimate form of recycling. Stuttgart,Germany: Fraunhofer IRB Verlag; 1998.

[20] McDonaugh W, Braungart M. The next industrial revolution. The AtlanticMonthly; 1998.

J. Johansson, C. Luttropp / Journal of Cleaner Production 17 (2009) 26–35 35

[21] McDonaugh W, Braungart M. Cradle to cradle: remaking the way we makethings. North Point Press; 2002. p. 103–114.

[22] RoHS. EU Directive 2002/95/ on the restriction of the use of certain hazardoussubstances in electrical and electronic equipment. RoHS; 2003.

[23] REACH. Regulation (EC) No 1907/2006 of the European parliament and of thecouncil of 18 December 2006 concerning the registration, evaluation,authorisation and restriction of chemicals (REACH).

[24] Ekerot S, editor. Stålets kretslopp. Rapport i Jernkontorets Forskning nr D729;2003 [in Swedish].

[25] London Metal Exchange, http://www.lme.com/copper.asp [accessed 06.12.06].

[26] Bertram M, Graedel TE, Rechberger H, Spatari S. The contemporary Europeancopper cycle: waste management subsystem. In: Ecological Economics, 42.Elsevier Science B.V; 2002. 43–57.

[27] El-kretsen AB, http://www.el-kretsen.se [accessed 28.06.06].[28] Manouchehri HR. Looking at shredding plant configuration and its perfor-

mance for developing shredding product stream (an overview). NorthlandOretech Consulting Co; 2005. Manuscript.