Design for and from Recycling: A Circular Ecodesign Approach to Improve the Circular Economy

Abstract

In the context of a circular economy, one can observe that (i) recycling chains are not adapted enough to the end-of-life products they have to process and that (ii) products are not sufficiently well designed either to integrate at best their target recycling chain. Therefore, a synergy between product designers and recycling-chains stakeholders is lacking, mainly due to their weak communication and the time-lag between the product design phase and its end-of-life treatment. Many Design for Recycling approaches coexist in the literature. However, to fully develop a circular economy, Design from Recycling also has to be taken into account. Thus Re-Cycling, a complete circular design approach, is proposed. First, a design for recycling methodology linking recyclability assessment to product design guidelines is proposed. Then, a design from recycling methodology is developed to assess the convenience of using secondary raw materials in the design phase. The recyclability of a smartphone and the convenience of using recycled materials in a new cycle are both analyzed to demonstrate our proposal. The Fairphone 2® and its treatment by the WEEE French takeback scheme are used as a case study.

Full text

sustainability
Article
Design for and from Recycling: A Circular Ecodesign
Approach to Improve the Circular Economy
Jorge Martínez Leal 1, *, Stéphane Pompidou 1, Carole Charbuillet 2and Nicolas Perry 3
1Université de Bordeaux, CNRS, I2M Bordeaux, F-33400 Talence Cedex, France;
stephane.pompidou@u-bordeaux.fr
2Arts et Métiers, Institut de Chambéry, F-73375 Le Bourget-du-Lac, France; carole.charbuillet@ensam.eu
3Arts et Metiers, CNRS, I2M Bordeaux, F-33405 Talence Cedex, France; nicolas.perry@u-bordeaux.fr
*Correspondence: jorge.martinez-leal@u-bordeaux.fr
Received: 31 October 2020; Accepted: 21 November 2020; Published: 25 November 2020


Abstract:
In the context of a circular economy, one can observe that (i) recycling chains are not adapted
enough to the end-of-life products they have to process and that (ii) products are not sufficiently well
designed either to integrate at best their target recycling chain. Therefore, a synergy between product
designers and recycling-chains stakeholders is lacking, mainly due to their weak communication
and the time-lag between the product design phase and its end-of-life treatment. Many Design for
Recycling approaches coexist in the literature. However, to fully develop a circular economy, Design
from Recycling also has to be taken into account. Thus Re-Cycling, a complete circular design approach,
is proposed. First, a design for recycling methodology linking recyclability assessment to product
design guidelines is proposed. Then, a design from recycling methodology is developed to assess the
convenience of using secondary raw materials in the design phase. The recyclability of a smartphone
and the convenience of using recycled materials in a new cycle are both analyzed to demonstrate our
proposal. The Fairphone 2
®
and its treatment by the WEEE French takeback scheme are used as a
case study.
Keywords: design for recycling; design from recycling; ecodesign; circular economy
1. Introduction
Proper management of waste is a key point for avoiding pollution of environmental matrices,
such as soil and groundwater, and to avoid contaminant emission in the atmosphere [
1
,
2
]. The actions
implemented by legislation to encourage the recovery of end-of-life (EoL) products (i.e., waste) can
be divided into two main categories. The first one consists of setting up waste treatment chains [
3
],
and the second one aims to prevent the generation of waste through better product design [4,5].
A performance review of extended producer responsibility (EPR) treatment chains has shown
that some are insufficiently adapted to the waste they process; on the other hand, products are not
systematically designed to best match their chain [
6
]. This lack of synergy between the product and its
treatment chain is due to the weak communication between designers and recovery-chain stakeholders [
7
].
Moreover, the time-lag between the product design and its end-of-life treatment may weaken this link
as well as the geographic performance disparity between the stakeholders involved in the chain [
8
,
9
].
This link between design and end-of-life stakeholders is therefore essential to ensure that the product is
better recovered when it becomes waste.
This article presents Re-Cycling, an innovative indicator-based design approach that includes
both design for recycling and design from recycling in a combined approach that seeks to improve
circular economy by creating a direct and bijective link between product designers and EoL chain
stakeholders. The article focuses on the designer’s point of view.
Sustainability 2020,12, 9861; doi:10.3390/su12239861 www.mdpi.com/journal/sustainability

Sustainability 2020,12, 9861 2 of 30
2. Materials and Methods
2.1. Re-Cycling: Circularity Management by Both Design and End-of-Life Stakeholders
As previously mentioned, both design and end-of-life phases of the product lifecycle must be
connected to ensure the circularity of components and materials. Therefore, designers must take
this into account by designing for and from the end-of-life. The corollary is that stakeholders of the
product’s end-of-life must also change their practices to work from and for the design. The possible
approaches and exchanges between design and EoL stakeholders are illustrated in Figure 1.
Sustainability 2020, 12, x FOR PEER REVIEW 2 of 29
2. Materials and Methods
2.1. RE-CYCLING: Circularity Management by Both Design and End-of-Life Stakeholders
As previously mentioned, both design and end-of-life phases of the product lifecycle must be
connected to ensure the circularity of components and materials. Therefore, designers must take this
into account by designing for and from the end-of-life. The corollary is that stakeholders of the
product’s end-of-life must also change their practices to work from and for the design. The possible
approaches and exchanges between design and EoL stakeholders are illustrated in Figure 1.
Figure 1. Possible approaches and exchanges between designers and EoL stakeholders.
2.1.1. Product Designers Approaches
From the product designer’s point of view (see Figure 1), two approaches can be followed:
• Design for EoL is the most known and the most used. It aims (i) to improve the product so that it
can be recovered in the best possible way when it becomes waste and (ii) to promote the
elimination of residues that could not be recovered;
• Design from EoL is concerned with the integration of artefacts from the end-of-life treatment chain
into a new product (e.g., use of recycled materials instead of virgin ones, reuse of modules or
parts extracted during disassembly, etc.).
2.1.2. End-of-Life Stakeholders Approaches
From the EoL stakeholders’ point of view (see Figure 1), two approaches can be followed:
• EoL from design aims to integrate the information accrued from the product design into the
operating mode of the chain or its treatment processes to increase the functional, material, and
energy recovery;
• EoL for design is concerned with the end-of-life treatment pathway that becomes a supplier of
artefacts (i.e., product, module, part, or material from a recovery pathway), which must meet
the designer’s specifications.
Design End-of-Life
Design
from
End-of-Life
End-of-Life
from
Design
Al
Design
for
End-of-Life
End-of-Life
for
Design
Product
(from Design)
Product
(from End-of-Life)
Information
Exchanges
Figure 1. Possible approaches and exchanges between designers and EoL stakeholders.
2.1.1. Product Designers Approaches
From the product designer’s point of view (see Figure 1), two approaches can be followed:
•
Design for EoL is the most known and the most used. It aims (i) to improve the product so that it can
be recovered in the best possible way when it becomes waste and (ii) to promote the elimination
of residues that could not be recovered;
•
Design from EoL is concerned with the integration of artefacts from the end-of-life treatment chain
into a new product (e.g., use of recycled materials instead of virgin ones, reuse of modules or parts
extracted during disassembly, etc.).
2.1.2. End-of-Life Stakeholders Approaches
From the EoL stakeholders’ point of view (see Figure 1), two approaches can be followed:
•
EoL from design aims to integrate the information accrued from the product design into the operating
mode of the chain or its treatment processes to increase the functional, material, and energy recovery;
•
EoL for design is concerned with the end-of-life treatment pathway that becomes a supplier of
artefacts (i.e., product, module, part, or material from a recovery pathway), which must meet the
designer’s specifications.

Sustainability 2020,12, 9861 3 of 30
2.1.3. Focus of the Article
From the designer’s point of view, assessing the product’s recoverability seems to be the first way
to develop or consolidate the link with the EoL chain stakeholders. However, there is a weak correlation
between recoverability (theoretical EoL treatment performance) and recovery (real performance) of
a product. Indeed, studies have shown a discrepancy between the potential recovery of a product
(evaluated from the design step) and what the chain actually recovers. This difference is mainly due to
the lack of information available by the designers for their analysis.
A way to improve this link is to create design tools that integrate the EoL notion. In this regard,
several tools have been identified in the literature [
10
]. However, they are proved to be insufficiently
used in practice. Despite the aforementioned problems, the assessment of product’s recoverability
remains today the assessment tool mainly used in product design [11].
In addition, designers involved in a design-for-EoL approach have to design their product to
best integrate the EoL treatment chain. To help them achieve this, a great number of design-for-EoL
guidelines are available in the literature [
12
]. However, they mainly consist of “design advices” among
which it is difficult to choose the most convenient. For this reason, we are interested in developing
a design approach to determine easily and objectively which guideline is the most appropriate for
achieving the desired objective or the most urgent according to the reality of the EoL treatment chain.
Another way to strengthen the link with the EoL chain stakeholders is to create design-from-EoL
approaches. Indeed, the recovery chain provides several products from different treatment pathways.
For example, the functional recovery pathway can provide either the whole product (full functional
recovery) or modules and parts (partial functional recovery). In addition, the material recovery pathway
provides recycled materials. Finally, the energy recovery pathway provides electricity, thermal energy,
or gas. All these coproducts coming out of the end-of-life recovery processes must meet the needs of
the potential clients (among which are designers) who will buy and use them.
Thereby, we also focus on the designer as a customer of the recycling chain to stimulate his interest in
integrating recycled materials into a new product. These materials must therefore meet the requirements
of the design specifications. However, note that any other artefact could also be considered (e.g., any
refurbished part or module that may incorporate a new product). Nevertheless, the classic example
of secondary raw materials (i.e., recycled materials) will provide a more accurate way of defining
our approach.
Promoting the use of recycled materials in product design is thus a fundamental strategy for
achieving a circular economy. For this reason, we are also interested in developing a design approach to
determine the convenience of using recycled material (i.e., feasibility and suitability) and thus simplify
the process of material selection. This proposal falls within the scope of a design-from-EoL approach.
The design-for-recycling approach is first presented (Section 2.2). Then, the design-from-recycling
one is detailed (Section 2.3). Both proposals are then tested with a case study on the results section
(Section 3) and lastly commented on the discussion section (Section 4).
2.2. Design-for-Recycling: Proposition of an Indicator-Based Approach
Today, product designers mainly use the assessment of product’s recoverability and the evaluation of
environmental impacts to know where design efforts should be directed. However, although recoverability
indicators match the elements of validation of regulatory constraints, there are very few (if any) with the
action levers associated with the design guidelines [6].
To simplify decision making, it is necessary to know whether the product characteristics to be
modified with these levers are consistent with a target or a reference. For this reason, we are interested in
linking product assessment to design-for-recycling guidelines by proposing an indicator-based approach.

Sustainability 2020,12, 9861 4 of 30
2.2.1. Method Description
The proposed design-for-recycling approach seeks to allow product designers to identify the product
characteristics that are the least efficient in terms of recycling, and to provide the most appropriate
guidelines to improve them. It is composed of the four steps listed in Figure 2.
Sustainability 2020, 12, x FOR PEER REVIEW 4 of 29
2.2.1. Method Description
The proposed design-for-recycling approach seeks to allow product designers to identify the
product characteristics that are the least efficient in terms of recycling, and to provide the most
appropriate guidelines to improve them. It is composed of the four steps listed in Figure 2.
Figure 2. Schematic representation of the proposed design-for-recycling approach.
The construction of the design-for-recycling approach is carried out in four steps. First, the
design-for-recycling guidelines and the product designer’s action levers are identified (see Section
2.2.2), then a grouping of product designer’s action levers is made (Section 2.2.3), later the indicators
associated with product designer’s action levers are selected (Section 2.2.4), and finally, the indicator-
based design-for-recycling guidelines are presented (Section 2.2.5).
2.2.2. Identification of Design-for-Recycling Guidelines and Product Designer’s Action Levers
Material recovery aims to preserve the added value of various materials by ensuring their
compatibility and by minimizing sorting rejects [13]. It aims at recovering all the material of the
product as secondary raw material. Therefore, material flows form a closed-loop (as promoted by the
circular economy), thus ensuring the preservation of primary raw materials.
The proper functioning of recovery pathways is impacted by several issues: on the one hand,
those associated with the pre-treatment stages (decontamination, disassembly, shredding, and
sorting), and on the other hand, those associated with the treatment pathways (e.g., recycling). The
performance of each stage is thus affected by various factors, the main ones of which are listed below:
Product characterisation
Materials’
compatibility Materials’
diversity
Action levers ranking
Identification of “hotspots”
corresponding guidelines
Materials’
recyclability
Aggregation
Identification of “hotspots”
2. Evaluation of action levers
Product’s
recyclability
3. Identification of product’s “hotspots”
Product selection
1. Selection and characterisation of the product
4. Proposal of relevant guidelines
Figure 2. Schematic representation of the proposed design-for-recycling approach.
The construction of the design-for-recycling approach is carried out in four steps. First, the design-
for-recycling guidelines and the product designer’s action levers are identified (see Section 2.2.2), then
a grouping of product designer’s action levers is made (Section 2.2.3), later the indicators associated
with product designer’s action levers are selected (Section 2.2.4), and finally, the indicator-based
design-for-recycling guidelines are presented (Section 2.2.5).
2.2.2. Identification of Design-for-Recycling Guidelines and Product Designer’s Action Levers
Material recovery aims to preserve the added value of various materials by ensuring their compatibility
and by minimizing sorting rejects [
13
]. It aims at recovering all the material of the product as secondary
raw material. Therefore, material flows form a closed-loop (as promoted by the circular economy), thus
ensuring the preservation of primary raw materials.

Sustainability 2020,12, 9861 5 of 30
The proper functioning of recovery pathways is impacted by several issues: on the one hand,
those associated with the pre-treatment stages (decontamination, disassembly, shredding, and sorting),
and on the other hand, those associated with the treatment pathways (e.g., recycling). The performance
of each stage is thus affected by various factors, the main ones of which are listed below:
•
decontaminationdependsmainly on the identification time, the clarity anddurability of the instructions,
and the dismantling time;
•dismantling is also affected by the identification time and the dismantling time;
•
shredding is impacted by the fragmentation capability of the product as well as the energy required
for this fragmentation;
•
sorting depends on the difference in physical properties between each of the shredded materials
(e.g., magnetism of ferrous metals, density difference between materials, etc.) and is highly dependent
on shredding quality;
•
recycling is mainly affected by material’s ability to be regenerated, as well as its compatibility with
the other materials to recycle, but also with (i) different grades of the same material, (ii) impurities
that were not separated during the shredding/sorting phase, and (iii) its surface treatments [13].
Design for material recovery is thus concerned with modifying the product to increase recovering
potential and regenerating its materials based on the knowledge of EoL chain processes and its
performances [6]. A review of design-for-recycling guidelines will be presented in Section 2.2.5.
The design-for-material-recovery guidelines have been organized into seven categories according to
the intended scope. The first five (product, components, materials, fasteners, and cables and connectors)
relate to design choices; the last two (marking and labelling, information) concern the transmission of
information to the different stakeholders involved in the product’s end-of-life (i.e., from the last user of the
product to the stakeholders in the EoL chain) to make the treatment process more efficient. The identified
categories and action levers are the following:
•
Product. Action levers depend solelyon the characteristics ofthe product, such as its complexity
[12,14–16]
,
modularity [12,15,16], and disassemblability [12,16–18];
•
Components. Action levers are here centered on the identifiability [
12
,
13
,
15
,
16
,
19
], accessibility
[12,15,16,20]
,
and disassemblability [
12
,
13
,
15
–
17
,
20
,
21
] of components containing non-recyclable, non-compatible,
toxic, precious, rare, and critical materials;
•
Materials. This category is mainly concerned with the selection of materials. The levers identified are
the diversity [
12
,
15
,
16
,
19
], compatibility [
12
,
15
–
17
,
19
–
21
], recyclability [
12
,
15
–
18
], toxicity [
14
,
17
,
18
],
and circularity [16] of materials, and also the use of recycled ones [12,15,16];
•
Fasteners. In this category, action levers are not only associated with the fasteners themselves
(complexity of the fastening system [
12
,
14
–
16
] and their diversity [
12
,
16
], identifiability [
12
,
15
–
17
],
accessibility [
12
,
15
–
18
,
20
], disassemblability [
12
,
15
–
20
], and durability [
18
]), but also with the
dismantling tools (tools’ diversity [
12
,
15
] and types [
12
,
14
–
16
,
18
,
20
]). Therefore, this category
includes action levers that seek to simplify the disassembly of fasteners;
•Cables and connectors. The complexity of the wiring system [12,15] is the only action lever;
•
Marking and labelling. The action lever is the implementation of identification systems for recyclable
and/or problematic components and materials [12,15–17,19–21];
•
Information. This category deals with the communication of useful information about the end-of-life
of the product to both users and stakeholders of the EoL chain [17].
The technical and environmental considerations referred to in the previous paragraph are not the
only ones to be taken into account. Indeed, the regulatory requirements must also be considered to have
an overall view of all the elements that must be validated by designers during a design-for-EoL process.
Within this context, designers must ensure that the recovery potential of their products is in
line with the recovery targets imposed by regulations (e.g., [22,23]). Additionally, for certain product

Sustainability 2020,12, 9861 6 of 30
categories, the legislation prohibits or restricts the use of several substances [
16
]. The summary of
regulatory constraints to be taken into account in design will be presented in Section 2.2.5.
It should be noted that in this section, we no longer seek to identify the action levers, but rather
the verification elements, which are the indicator (or any other tool) enabling us to confirm that the
regulatory constraint has been complied with.
Regulatory constraints have been divided into two categories according to the intended scope.
The first one relates to the extent to which the product can be potentially integrated by the recycling chain,
and the second one to the (potential) recovery requirements imposed on manufacturers. The identified
action levers relate to the following elements:
•Product. Reusability, recyclability, and recoverability of the product;
•Materials. Maximum tolerated concentration of harmful substances.
The analysis of design-for-EoL approaches has led to the identification of 23 action levers and
three regulatory constraints. A graphical summary of these action levers and regulatory constraints is
shown in Figure 3. Most of the action levers (21) are centered on design choices. The others focus on
the transmission of information.
Sustainability 2020, 12, x FOR PEER REVIEW 6 of 29
Regulatory constraints have been divided into two categories according to the intended scope.
The first one relates to the extent to which the product can be potentially integrated by the recycling
chain, and the second one to the (potential) recovery requirements imposed on manufacturers. The
identified action levers relate to the following elements:
• Product. Reusability, recyclability, and recoverability of the product;
• Materials. Maximum tolerated concentration of harmful substances.
The analysis of design-for-EoL approaches has led to the identification of 23 action levers and
three regulatory constraints. A graphical summary of these action levers and regulatory constraints
is shown in Figure 3. Most of the action levers (21) are centered on design choices. The others focus
on the transmission of information.
Figure 3. Graphical summary of the identified action levers and regulatory constraints.
2.2.3. Grouping of Product Designer’s Action Levers
It was observed that some of the action levers were related between them and could be used to
improve another one. Because of this, we decided to group the following action levers:
• Disassemblability of the product: (i) accessibility of components, (ii) accessibility of fasteners, (iii)
complexity of the product, (iv) complexity of the wiring system, (v) complexity of the fastening
system, (vi) disassemblability of components, (vii) disassemblability of fasteners, (viii) diversity
of fasteners, (ix) diversity of disassembly tools, (x) durability of fasteners, (xi) modularity of the
product, (xii) identifiability of components, (xiii) identifiability of fasteners, and (xiv)
standardization of disassembly tools
• Recyclability of the product: (i) compatibility of materials, (ii) diversity of materials, and (iii)
recyclability of materials
It is to be noted that the action lever recyclability of the product was added to the 23 that were
originally identified. A graphical summary of the main action levers is shown in Figure 4.
Figure 4. Grouping of product designer’s action levers.
▪Accessibility of components
▪Accessibility of fasteners
▪Compatibility of materials
▪Circularity of materials
▪Complexity of the product
▪Complexity of the wiring system
▪Complexity of the fastening system
▪Disassemblability of the product
▪Disassemblability of components
▪Disassemblability of fasteners
▪Diversity of materials
▪Diversity of fasteners
▪Diversity of disassembly tools
▪Durability of fasteners
▪Identifiability of components
▪Identifiability of fasteners
▪Modularity of the product
▪Recyclability of materials
▪Standardization of disassembly tools
▪Toxicity of materials
▪Use of recycled materials
Action levers
Design choices Information transmission
Regulatory constraints
▪Communication
▪Identification
▪Maximum allowed concentration
▪Reusability and recyclability rate
▪Recoverability rate
▪Circularity of materials
▪Disassemblability of the product
▪Recyclability of the product
▪Toxicity of materials
▪Use of recycled materials
Action levers
(material recovery)
Design choices Information transmission
▪Communication
▪Identification
Figure 3. Graphical summary of the identified action levers and regulatory constraints.
2.2.3. Grouping of Product Designer’s Action Levers
It was observed that some of the action levers were related between them and could be used to
improve another one. Because of this, we decided to group the following action levers:
•
Disassemblability of the product: (i) accessibility of components, (ii) accessibility of fasteners,
(iii) complexity of the product, (iv) complexity of the wiring system, (v) complexity of the fastening
system, (vi) disassemblability of components, (vii) disassemblability of fasteners, (viii) diversity
of fasteners, (ix) diversity of disassembly tools, (x) durability of fasteners, (xi) modularity of the
product, (xii) identifiability of components, (xiii) identifiability of fasteners, and (xiv) standardization
of disassembly tools
•
Recyclability of the product: (i) compatibility of materials, (ii) diversity of materials, and (iii) recyclability
of materials
It is to be noted that the action lever recyclability of the product was added to the 23 that were
originally identified. A graphical summary of the main action levers is shown in Figure 4.

Sustainability 2020,12, 9861 7 of 30
Sustainability 2020, 12, x FOR PEER REVIEW 6 of 29
Regulatory constraints have been divided into two categories according to the intended scope.
The first one relates to the extent to which the product can be potentially integrated by the recycling
chain, and the second one to the (potential) recovery requirements imposed on manufacturers. The
identified action levers relate to the following elements:
• Product. Reusability, recyclability, and recoverability of the product;
• Materials. Maximum tolerated concentration of harmful substances.
The analysis of design-for-EoL approaches has led to the identification of 23 action levers and
three regulatory constraints. A graphical summary of these action levers and regulatory constraints
is shown in Figure 3. Most of the action levers (21) are centered on design choices. The others focus
on the transmission of information.
Figure 3. Graphical summary of the identified action levers and regulatory constraints.
2.2.3. Grouping of Product Designer’s Action Levers
It was observed that some of the action levers were related between them and could be used to
improve another one. Because of this, we decided to group the following action levers:
• Disassemblability of the product: (i) accessibility of components, (ii) accessibility of fasteners, (iii)
complexity of the product, (iv) complexity of the wiring system, (v) complexity of the fastening
system, (vi) disassemblability of components, (vii) disassemblability of fasteners, (viii) diversity
of fasteners, (ix) diversity of disassembly tools, (x) durability of fasteners, (xi) modularity of the
product, (xii) identifiability of components, (xiii) identifiability of fasteners, and (xiv)
standardization of disassembly tools
• Recyclability of the product: (i) compatibility of materials, (ii) diversity of materials, and (iii)
recyclability of materials
It is to be noted that the action lever recyclability of the product was added to the 23 that were
originally identified. A graphical summary of the main action levers is shown in Figure 4.
Figure 4. Grouping of product designer’s action levers.
▪Accessibility of components
▪Accessibility of fasteners
▪Compatibility of materials
▪Circularity of materials
▪Complexity of the product
▪Complexity of the wiring system
▪Complexity of the fastening system
▪Disassemblability of the product
▪Disassemblability of components
▪Disassemblability of fasteners
▪Diversity of materials
▪Diversity of fasteners
▪Diversity of disassembly tools
▪Durability of fasteners
▪Identifiability of components
▪Identifiability of fasteners
▪Modularity of the product
▪Recyclability of materials
▪Standardization of disassembly tools
▪Toxicity of materials
▪Use of recycled materials
Action levers
Design choices Information transmission
Regulatory constraints
▪Communication
▪Identification
▪Maximum allowed concentration
▪Reusability and recyclability rate
▪Recoverability rate
▪Circularity of materials
▪Disassemblability of the product
▪Recyclability of the product
▪Toxicity of materials
▪Use of recycled materials
Action levers
(material recovery)
Design choices Information transmission
▪Communication
▪Identification
Figure 4. Grouping of product designer’s action levers.
2.2.4. Selection and Definition of the Indicators Associated with Product Designer’s Action Levers
As mentioned above, it is important to know whether the characteristics of the product we want
or need to change are in line with an objective or a reference. Therefore, this section focuses on defining
the performance indicators and indexes associated with the action levers for design choices related to
recyclability. This will be followed by the description of the guidelines to be used if the action lever is
identified as non-performing.
To compare the performance of the action levers, the value of the performance indicators must be
expressed on the same range of values. Thus, we define that indicators and indexes used to assess the
performance of the action levers must have the following characteristics:
•the result value must be within the range of 0 to 1;
•the value of 1 must correspond to the best score and 0 to the worst.
Indicators that do not have this form will have to be normalized.
When the aggregation of indicators is necessary, Maurin’s index construction method [
24
] will
be used as a reference. In his analysis, the fundamental, symmetric, algebraic, and homogeneous
functions from first to nth degree were studied. He found that:
•
for the first-degree function, the variation in each indicator reflects in the same way on the index;
•
for the
n
th degree function, it was observed that for the minimum value of one of the indicators,
the partial derivative of the index with respect to this indicator is the highest and for the maximum
value, the derivative is the lowest. The function is then sensitive to the lowest values;
•
for the intermediate symmetrical functions (degree 2 to n
−
1), the same behavior as for the
n
th
degree function has been identified.
Unlike Maurin’s index, we want that the variation of each indicator has the same impact on the
index. Therefore, we do not seek to give sensitivity to the highest values as in the original study.
We prefer that the variation of each indicator occurs in the same way in the index. Therefore, the average
function has been chosen (first-degree function).
Recyclability of the product
As previously mentioned, three action levers associated with the recyclability of the product
have been identified: compatibility, diversity, and recyclability of its materials. An index allowing the
indicators associated with these three parameters to be aggregated is therefore necessary. The product’s
recyclability index is defined as an average as follows:
Rp=Cm+Dm+Rm
nal (1)
with
Rp
: recyclability of the product;
Cm
: compatibility of materials;
Dm
: diversity of materials;
Rm: recyclability of materials; nal: number of aggregated action levers.

Sustainability 2020,12, 9861 8 of 30
Compatibility of materials
The material compatibility action lever addresses the chemical compatibility of materials during
recycling. Two materials are thus incompatible if the properties (mechanical or other) of the material to
be recycled decrease if both are recycled together. Some indicators of material compatibility have been
identified in the literature:
•
Ishii et al. [
25
] propose to assess the compatibility of materials in a semi-qualitative way. The proposed
indicator defines six levels of compatibility: very compatible (1), compatible (0.8), some level of
compatibility (0.6), incompatible (0.2), hazardous (0), and no information (0.5). The allocated score
is within the range [0,1];
•
Qian et al. [
26
] propose to use matrices to easily visualize the compatibility information. Compatibility
is divided into four levels: most compatible, some compatible, limited compatible, and no compatible.
Here, the value of the indicator is not numerical, but a graph indicating compatibility degree by zones;
•
Pahl et al. [
20
] propose an indicator similar to that of Qian et al. Compatibility of materials (plastics)
is classified on four levels: compatible, limited compatibility, compatible in small quantities, and not
compatible. As for the indicator of Qian et al., the value provided by this indicator is graphical and
not numerical;
•
De Aguiar et al. [
27
] propose a compatibility indicator similar to the previous ones. They propose
to classify material compatibility into four levels: same material (1), compatible materials (2), low
compatibility materials (3), and non-compatible materials (4). The indicator’s range is therefore
between 1 and 4.
All the identified indicators give a semi-quantitative score of the compatibility between two
materials. They could all (with minor modifications) be used in our approach.
A new indicator based on the identified indicators is proposed. Pahl et al.’s compatibility indicator
was chosen as the starting point for the construction of ours, because it was considered the most
appropriate (due to its ranking). The following modifications were made:
•
the compatibility values are expressed in a similar way to those proposed by Ishii et al. so that the
provided value is a number (and not a graph). The value is thus contained in the interval [0;1] so
the interpretation remains the same as the one adopted for all indicators (i.e., 0 being the worst
value and 1 being the best);
•the situation where the designer has no information, proposed by Ishii et al., has been added.
The indicator of compatibility between two materials cmis defined in Table 1.
Table 1. Indicator of compatibility between two materials.
Level cm
Compatible 1.0
Limited compatibility 0.5
Compatible in small quantities 0.25
Not compatible 0.0
No information 0.25
In our approach, the compatibility assessment does not stop at the comparison of two materials. Indeed,
material’s compatibility must be assessed for a module or a multi-material part. Therefore, compatibility
must be assessed with all the other materials contained in the studied module or part. However, an index
capable of assessing the compatibility of one material with all the others (with which it will be recycled) is

Sustainability 2020,12, 9861 9 of 30
missing. An aggregation of compatibilities is therefore necessary. The compatibility index of a material is
thus defined as an average function as follows:
Ci
m=
u
P
j=1ci,j
m
u(2)
with
Ci
m
: compatibility of the
i
th material;
ci,j
m
: compatibility between the
i
th and the
j
th material;
u: number of materials.
It is to be noted that there are two reading modes for compatibility analysis:
•
the first mode corresponds to the line reading (Figure 5a). It shows the compatibility of our material
as one of the main materials (i.e., as a material to be recycled);
•
the second mode corresponds to the column reading (Figure 5b). It shows the compatibility of
our material as one of the secondary materials (i.e., as an impurity that could compromise the
recycling of the main material).
Sustainability 2020, 12, x FOR PEER REVIEW 9 of 29
(a)
(b)
Figure 5. Reading modes of the material’s compatibility matrix: (a) Compatibility as main material;
(b) Compatibility as secondary material. * Material selected for the study.
We can then define, for each material, a compatibility as main material (
) and another one as
secondary material (
). The material compatibility score (
) is assigned according to whether the
material is considered as a main or a secondary material in its specific recycling chain. When this
information is not available, the worst of both scores is selected. An overall compatibility score ()
can finally be calculated as the average of the compatibility of all materials. It is expressed as follows:
1
ui
m
i
m
C
Cu
=
=

(2)
with : compatibility of all materials; 
: compatibility of the  material; : number of materials.
Diversity of materials
We define material diversity as the variety of materials used in a product. Diversity contributes
inversely to the recyclability of the product: the greater the diversity (i.e., more different materials),
the more difficult it is to recycle them.
It is important to note that we do not know the precise effect of this diversity of materials on the
recyclability of the product. However, in a very general way we expect the following behavior:
• the greater the variety of materials, the more difficult it is to recycle the product;
• the higher the concentration of a material, the easier it is to recycle it.
Therefore, the material diversity indicator must be defined according to two parameters: the
number of materials and their concentration in the product.
A literature review on material diversity indicators was conducted. Most of the articles do not
specify how this diversity is measured. However, it is implied that it refers to the number of different
materials used in a product. Only two indicators were identified:
• Dostatni et al. [28] proposed the rate of materials diversity indicator, whose value is in the range
between 0.5 and 5. The rate of material diversity indicator is dependent on the number of
occurrences (i.e., the number of parts) of the material the most frequently used in the product,
and the number of occurrences of other materials;
• Rzeźnik et al. [29] measure the material heterogeneity (i.e., the material diversity) of a machine
using its information entropy.
The indicator proposed by Dostatni et al. does not correspond to our needs. The main problem
is that the mass of these materials is not taken into account. This is indeed an important parameter:
for example, if the product is made from a wide variety of materials, most of which are in very small
quantities, and one of its parts has a mass of more than 99% of the whole, the product could be
considered as being single-material. This indicator is not able to reflect this kind of situations.
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0.5 0 .5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0.25 0.5 1 1 Compatible
PC Mix 1 0.5 0 1 1 0 1 1 0.5 Limited compatibility
PA Mix 0 0.5 0 1 0 1 0.5 0.5 0.25 Compatible in sm all quantities
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1 0 Not compatible
Undefined plastic (ABS*) 1 0 1 1 0.25 0.25 1 1 0.25 No information
Secondary material
Main material
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0.5 0 .5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0.25 0.5 1 1 Compatible
PC Mix 1 0.5 0 1 1 0 1 1 0.5 Limited compatibility
PA Mix 0 0.5 0 1 0 1 0.5 0.5 0.25 Compatible in sm all quantities
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1 0 Not compatible
Undefined plastic (ABS*) 1 0 1 1 0.25 0.25 1 1 0.25 No information
Secondary material
Main material
Figure 5.
Reading modes of the material’s compatibility matrix: (
a
) Compatibility as main material;
(b) Compatibility as secondary material. * Material selected for the study.
We can then define, for each material, a compatibility as main material (
Ci
mb
) and another one
as secondary material (
Ci
mc
). The material compatibility score (
Ci
m
) is assigned according to whether
the material is considered as a main or a secondary material in its specific recycling chain. When this
information is not available, the worst of both scores is selected. An overall compatibility score (
Cm
)
can finally be calculated as the average of the compatibility of all materials. It is expressed as follows:
Cm=
u
P
i=1Ci
m
u(3)
with Cm: compatibility of all materials; Ci
m: compatibility of the ith material; u: number of materials.
Diversity of materials
We define material diversity as the variety of materials used in a product. Diversity contributes
inversely to the recyclability of the product: the greater the diversity (i.e., more different materials),
the more difficult it is to recycle them.
It is important to note that we do not know the precise effect of this diversity of materials on the
recyclability of the product. However, in a very general way we expect the following behavior:

Sustainability 2020,12, 9861 10 of 30
•the greater the variety of materials, the more difficult it is to recycle the product;
•the higher the concentration of a material, the easier it is to recycle it.
Therefore, the material diversity indicator must be defined according to two parameters: the
number of materials and their concentration in the product.
A literature review on material diversity indicators was conducted. Most of the articles do not
specify how this diversity is measured. However, it is implied that it refers to the number of different
materials used in a product. Only two indicators were identified:
•
Dostatni et al. [
28
] proposed the rate of materials diversity indicator, whose value is in the range
between 0.5 and 5. The rate of material diversity indicator is dependent on the number of occurrences
(i.e., the number of parts) of the material the most frequently used in the product, and the number of
occurrences of other materials;
•
Rze´znik et al. [
29
] measure the material heterogeneity (i.e., the material diversity) of a machine
using its information entropy.
The indicator proposed by Dostatni et al. does not correspond to our needs. The main problem
is that the mass of these materials is not taken into account. This is indeed an important parameter:
for example, if the product is made from a wide variety of materials, most of which are in very small
quantities, and one of its parts has a mass of more than 99% of the whole, the product could be considered
as being single-material. This indicator is not able to reflect this kind of situations.
On the other hand, the indicator proposed by Rze´znik et al. is consistent with the expected behaviour
of the indicator assessing the diversity of materials (in terms of number and concentration of materials):
•
the indicator is dependent on the diversity of materials: the more different materials the product
contains, the more the entropy value increases;
•
the indicator is dependent on the concentration of materials: the higher the concentration of a
material, the lower the value of diversity.
However, this indicator had to be adapted to homogenize its range of values with those of our
other indicators. Since the diversity of materials contributes inversely to the recyclability of the product,
the inverse function was used. Moreover, it is known that entropy values start at 0 (for a single-material
product for which there is no disorder) and increase with the number and concentration of materials.
For this reason, a coefficient is added to the denominator. The proposed indicator is then defined
as follows:
Dm=1
1−
u
P
i=1cilog2ci
(4)
with Dm: diversity of materials; ci: concentration of the ith material; u: number of materials; Pci=1.
Recyclability of materials (treatment efficiency)
The action lever recyclability of materials is a performance indicator for the recycling chain that
focuses on the efficiency of recycling. The proposed indicator is based on the two parameters used to
assess the product’s recoverability and more specifically, to calculate the efficiency potential of material
recovery [30]. It is defined by:
rm=τrτp(5)
with rm: recyclability of material; τr: material recycling rate; τp: material purity rate.
The recycling rate used above is constructed in the same way as the waste treatment recycling
rate proposed by Horta Arduin et al. [
31
], as it seeks to assess treatment chain performance. The only
difference is obviously that only one recycled fraction is taken into account in the calculation.
The material recycling rate is therefore defined as follows:
τr=mrc
mtc (6)

Sustainability 2020,12, 9861 11 of 30
with
τr
: material recycling rate;
mrc
: mass of material recycled by the chain;
mtc
: mass of material
treated by the chain.
The purity rate seeks to estimate the degree of quality preservation of recycled materials. Grimaud
has defined the output quality as the indicator expressing the capacity of a sorting technology to extract,
from a mixed waste stream, a material stream corresponding to a defined typology [
32
]. He defined this
indicator as to the ratio between the amount of material present in the output stream corresponding
to this typology and the total amount of waste constituting the output fraction. This material purity
indicator has been used as a starting point to build our indicator. However, the fraction that we take
into account is the fraction that comes out of recycling and not the fraction that comes out of sorting.
The indicator is defined as follows:
τp=mm
mm+mom (7)
with
τp
: material purity rate;
mm
: mass of material in the recycled fraction;
mom
: mass of other materials
in the recycled fraction.
An overall value characterizing the recyclability of all materials in the product is required. The material
recyclability index is therefore defined as an average as follows:
Rm=
u
P
i=1ri
m
u(8)
with Rm: recyclability of materials; ri
m: recyclability of the ith material; u: number of materials.
2.2.5. Indicator-Based Design for Recycling Guidelines
The indicators defined in the previous section create a link between product assessment and design
for Xguidelines. In this section, the design for recycling guidelines to be used when a component is
identified as non-performant is presented. A summary of the aforementioned guidelines is presented
in Table 2. For each guideline, the associated action leaver and its scope (i.e., product, component,
material, etc.) can be observed.
Table 2. Summary of design for recycling guidelines.
Scope Action Lever Guidelines
Product
Complexity Minimize the number of components
Modularity Make the product as modular as possible (with material separation)
Disassemblability
Reduce time and number of disassembly steps
Increase the linearity of the disassembly sequence
Minimize divergence in the dismantling sequence order
Homogenize the principles of assembly and disassembly
Design the product so that it can be easily transported after use (i.e.,
allowing for pre-disassembly)
Components
Identifiability Components containing non-recyclable, non-compatible, toxic,
valuable, rare, and critical materials must be easily identified
Accessibility Components containing non-recyclable, non-compatible, toxic,
valuable, rare, and critical materials must be easily accessible
Disassemblability
Components containing non-recyclable, non-compatible, toxic,
valuable, rare, and critical materials must be easily removed
Where the materials of inseparable parts or sub-assemblies are not
compatible, ensure that they are easily separable
Design parts for disassembly stability

Sustainability 2020,12, 9861 12 of 30
Table 2. Cont.
Scope Action Lever Guidelines
Materials
Diversity
Minimize the number of different types of materials
Avoid the mixing of materials in assemblies
Monomaterial strategy. Favor using a single material per product
or sub-assembly
Compatibility
Use compatible materials (that can be recycled together) in the product
or sub-assembly
Use fasteners made of a material compatible with the other parts
Recyclability
Use recyclable materials
Choose materials that can easily recover their original properties
after recycling
Use of recycled
materials Use recycled materials
Toxicity Avoid or reduce the use of substances, materials, or components
harmful to humans or the environment
Circularity Design considering the secondary use of recycled materials
Fasteners
Complexity Minimize the number of fasteners
Diversity Minimize the number of different types of fasteners
Identifiability Fasteners must be easily identified
Accessibility Fasteners must be easily accessible (including the space for the
disassembly tool)
Disassemblability Fasteners must be easily removed
Diversity Minimize the required number of fastener disassembly tools
Standardisation Promote the use of standard disassembly tools
Durability Protect fasteners from corrosion and wear
Cables and
connectors Complexity Minimize the number and length of interconnecting wires or cables
Marking and
labelling Identification
Standardized coding and marking of materials to facilitate their
identification (especially plastic parts)
Standardized labelling of products and components on recyclability,
incompatibility, and/or toxicity so that they can be easily identified
from recyclables and waste streams
Eliminate labels incompatible with end-of-life treatment
Place identification elements in visible locations
Information Communication
Provide useful processing-related information
Provide information to the user on how the product or its parts are to
be disposed of
A summary of the regulatory constraints to which a product designer is subjected is presented in
Table 3. Similarly to the previous table, for each regulatory constraint, the associated validation tool
and its scope can be observed.
2.3. Design from Recycling: Proposition of an Index Assessing the Convenience of Using Recycled Materials
The recovery chain provides several products derived from the different treatment pathways.
We focus on product designers as customers of the chain to encourage their interest in using recycled
materials in new products. These secondary raw materials must meet the design specifications.

Sustainability 2020,12, 9861 13 of 30
Table 3. Summary of regulatory constraints.
Scope Validation Tool Regulatory Constraints
Product Reusability and recyclability rate Potentially reusable and recyclable mass percentage of a
new product
Recoverability rate Potentially recoverable mass percentage of a new product
Materials Maximum allowed concentration Restrictions on the use of certain hazardous substances
in products
Encouraging the use of recycled material in product design is a fundamental approach to promote
the circular economy. For this reason, we are interested in developing a design tool to determine the
convenience of using recycled material (i.e., feasibility and suitability) and thus simplify the process
of material selection. The convenience of using recycled material is assessed based on an index that
aggregates three indicators, each of which concerns one of the selected dimensions (technical, economic,
and environmental).
2.3.1. Method Description
Assessing the convenience of using recycled material is a complementary approach to the one
proposed in the previous paragraph (Section 2.2). The objective is to provide the designer with validation
evidence to judge (and justify if necessary) the appropriateness of using recycled material. The proposed
design from recycling approach is composed of the three steps detailed in Figure 6.
Sustainability 2020, 12, x FOR PEER REVIEW 13 of 29
2.3.1. Method Description
Assessing the convenience of using recycled material is a complementary approach to the one
proposed in the previous paragraph (Section 2.2). The objective is to provide the designer with
validation evidence to judge (and justify if necessary) the appropriateness of using recycled material.
The proposed design from recycling approach is composed of the three steps detailed in Figure 6.
Figure 6. Schematic representation of the proposed design-from-recycling approach.
The index will produce a score whose value varies around 1 (see Figure 7). If the score is inferior
to 1, it means that using recycled material is more convenient than using virgin material. Inversely,
recycled material is less convenient if the score is greater than 1.
Figure 7. Graphical result example of the assessment of the convenience of using recycled material.
The construction of the design-from-recycling approach is carried out in three steps. First, the
assessment indicators are defined for each dimension (see Section 2.3.2), the weighting method is
then determined (Section 2.3.3), and finally, the aggregation method is chosen (Section 2.3.4).
Selection of the
Recycled Material
Recycled
Material
Purity Rate
Recycled
Material Supply
Reliability
Recycled Material
Economic Value
——————————
Virgin Material
Economic Value
Environmental Convenience
Transformation Function
Economic ConvenienceTechnical Convenience
Convenience of Using
Recycled Materials
Aggregation
Aggregation
Recycled Material
Environmental Value
——————————
Virgin Material
Environmental Value
1. Selection of the Recycled Material
2. Evaluation of Convenience Indicators
3. Evaluation of Convenience Index
Figure 6. Schematic representation of the proposed design-from-recycling approach.
The index will produce a score whose value varies around 1 (see Figure 7). If the score is inferior
to 1, it means that using recycled material is more convenient than using virgin material. Inversely,
recycled material is less convenient if the score is greater than 1.

Sustainability 2020,12, 9861 14 of 30
Sustainability 2020, 12, x FOR PEER REVIEW 13 of 29
2.3.1. Method Description
Assessing the convenience of using recycled material is a complementary approach to the one
proposed in the previous paragraph (Section 2.2). The objective is to provide the designer with
validation evidence to judge (and justify if necessary) the appropriateness of using recycled material.
The proposed design from recycling approach is composed of the three steps detailed in Figure 6.
Figure 6. Schematic representation of the proposed design-from-recycling approach.
The index will produce a score whose value varies around 1 (see Figure 7). If the score is inferior
to 1, it means that using recycled material is more convenient than using virgin material. Inversely,
recycled material is less convenient if the score is greater than 1.
Figure 7. Graphical result example of the assessment of the convenience of using recycled material.
The construction of the design-from-recycling approach is carried out in three steps. First, the
assessment indicators are defined for each dimension (see Section 2.3.2), the weighting method is
then determined (Section 2.3.3), and finally, the aggregation method is chosen (Section 2.3.4).
Selection of the
Recycled Material
Recycled
Material
Purity Rate
Recycled
Material Supply
Reliability
Recycled Material
Economic Value
——————————
Virgin Material
Economic Value
Environmental Convenience
Transformation Function
Economic ConvenienceTechnical Convenience
Convenience of Using
Recycled Materials
Aggregation
Aggregation
Recycled Material
Environmental Value
——————————
Virgin Material
Environmental Value
1. Selection of the Recycled Material
2. Evaluation of Convenience Indicators
3. Evaluation of Convenience Index
Figure 7. Graphical result example of the assessment of the convenience of using recycled material.
The construction of the design-from-recycling approach is carried out in three steps. First, the assessment
indicators are defined for each dimension (see Section 2.3.2), the weighting method is then determined
(Section 2.3.3), and finally, the aggregation method is chosen (Section 2.3.4).
2.3.2. Selection and Definition of the Indicators
Design decision-making tools focusing on the choice of materials are available in the literature.
For example, Ecodesign Pilot proposes some guidelines associated with the selective choice of materials
for the reduction of environmental impacts [17]:
•use materials that benefit from a good environmental score;
•avoid or reduce the use of toxic materials or components;
•prefer the use of materials coming from renewable raw materials;
•prefer recyclable raw materials;
•avoid irreversible mixing of materials;
•avoid raw materials and parts whose origin is problematic.
Assessing the convenience of using a recycled material involves verifying how it has been recovered.
In the context of recoverability assessment, a study showed that product recoverability is evaluated
on three dimensions (technical, economic, and environmental) [
11
]. It was observed that the technical
dimension is focused on assessing the technical performance of the product’s processing, and the other
two dimensions are interested in assessing the economic and environmental convenience of the process.
By extrapolation, we define that the designer seeking to use the recycled material must validate that
the technical properties of the material are well recovered and that this recovery is economically and
environmentally convenient.
The proposed indicators for assessing the convenience of using recycled materials on each
dimension are presented in the following paragraphs.
Technical Convenience of Using Recycled Materials
As mentioned above, product designers (as potential customers of a material produced by recycling
chains) must ensure that the proposed material meets their specifications. Technical compliance must
therefore be verified. We propose to evaluate it using two parameters: the quality of the recycled
material and the reliability of supply.
On the one hand, the parameter of quality of the recycled material verifies that the technical
properties of the material have been properly recovered. In this regard, the use of a purity factor to
take into account the preservation of quality in recycled materials has been observed in the assessment
of material recyclability [6]. Purity rate is therefore used as an indicator.

Sustainability 2020,12, 9861 15 of 30
On the other hand, raw materials with supply problems should be avoided [
17
]. Indeed, waste
streams vary in quantity and composition, and suppliers of secondary raw materials may be sensitive
to this particularity of their input stream. The design team, in partnership with the purchasing
department, must therefore ensure that the supplier of recycled material can supply the material in
the required quality, quantity, and timeframe. Reliability of supply
sr
is thus proposed as a second
parameter to be taken into account. The indicator is presented in Table 4.
Table 4. Indicator of reliability of supply.
Scenario sr
The recycled material supplier complies with the purchasing department criteria 1
The recycled material supplier does not comply with the purchasing department criteria 0
The technical convenience index should aggregate both indicators mentioned above. Aggregation
in the form of a product was chosen so that the index would be sensitive to low values. In particular,
we are interested in the supply reliability indicator. Indeed, if the reliability of supply is not guaranteed,
the value of the index will be zero, because the use of this recycled material may be risky, and that makes
it not convenient (even if its good quality material). In contrast, if the supply reliability is guaranteed,
the relevance solely depends on the quality of the recycled material. The technical convenience index
is defined as follows:
pteu =2−τp×sr(9)
with
pteu
: technical convenience of the recycled material;
τp
: purity rate of the recycled material;
sr: supply reliability of the recycled material.
Note that the resulting values of the indicator are contained within the range [
1
,
2
]. This choice
was made to normalize it with the other two convenience indicators.
Economic Convenience of Using Recycled Materials
The economic dimension of the convenience of using recycled material aims to assess whether
the materials issued from the end-of-life treatment are economically more interesting than the ones
coming from the ores. The indicator to be used must therefore compare the price of secondary (i.e.,
recycled) raw materials to the price of primary (i.e., virgin) ones. In addition, such a comparison
must be expressed in the form of a ratio. Indeed, a ratio of two quantities of the same nature would
make it possible to better visualize their relationship, thus facilitating not only the interpretation of the
indicator, but also design decision making. The indicator to be used is thus defined as follows:
pecu =vec
vec,re f (10)
with
pecu
: economic convenience of the recycled material;
vec
: economic value (recycled material);
vec,re f : economic reference value (virgin material).
Environmental Convenience of Using Recycled Materials
The environmental convenience of using recycled material aims to assess whether the end-of-life
treatmenthas a higher or lowerimpactthan the productionofrawmaterials. To determine the environmental
dimension of the convenience of using recycled material, the indicator must therefore compare the
environmental impacts generated in the production of secondary raw materials (i.e., through recycling)
with the impacts generated in the production of primary raw materials. Thus, it is a special case of the
environmental performance of the treatment defined above. As with economic convenience, such a
comparison must be expressed in the form of a ratio. However, several environmental impact categories
exist and aggregation is then necessary. In our study, no single impact category was supposed more

Sustainability 2020,12, 9861 16 of 30
important than another. Therefore, an average of the relevance of all categories is proposed. Such a
calculation is possible, since the environmental relevance of each category is obtained as a ratio of
two values of the same nature. The resulting values are therefore dimensionless and have the same
reference level (1) regardless of the category. The indicator to be used is finally defined as follows:
penu =
s
P
k=1
vk
en
vk
en,re f
s(11)
with
penu
: environmental convenience of the recycled material;
vk
en
: environmental value (recycled
material) on the
k
th impact category;
vk
en,re f
: environmental reference value (virgin material) on the
k
th
impact category; k: impact category number (1 ≤k≤s); s: number of impact categories.
2.3.3. Selection of the Weighting Method
The weighting of the indicators consists of representing the importance given to each one of them.
However, it is difficult to reach a consensual objectification, as the coefficients used often result from
subjective or self-declared objective points of view [24].
Within the framework of weighting and aggregating sustainability indicators, Gan et al. [
33
]
studied the weighting methods of 90 indexes. They identified that the methods commonly used in the
literature are equal weighting (46.9%), principal components analysis (11.5%), public opinion (8.3%),
budget allocation (7.3%), analytic hierarchy process (6.3%), regression analysis (6.3%), benefit of the
doubt approach (3.1%), conjoint analysis (2.1%), unobserved component models (1%), and others (7.3%).
Our analysis method aims to ensure that the three dimensions for assessing the convenience of
using recycled material are given equal importance. The weighting method to be used is thus the equal
weighting method. In other words, the indicators will not be weighted.
2.3.4. Selection of the Aggregation Method
Indexes (i.e., aggregated indicators) reduce complex or multi-dimensional elements to a single variable
that can be used for decision-making [34]. However, aggregation methods are extremely numerous.
In the study presented in the previous paragraph [
33
], Gan et al. also identified the aggregation
methods most frequently used in the literature:
•
Additiveaggregation methods(86.5%): Theyusefunctionsthatsumthenormalizedvaluesoftheindicators
to form the index. The most common additive method is by far the weighted arithmetic mean;
•
Geometric aggregation methods (8.3%). These methods use multiplicative functions instead of additive
functions. Thegeometric aggregation functionthemostcommonlyusedistheweightedgeometricmean;
•
Non-compensatory aggregation methods (5.2%). The additive and geometric aggregations imply that
the compensation between the indicators is acceptable. Non-compensatory methods are used
when such compensation is deemed unacceptable. The result of such a method is rather a rank
than a concrete value. As no compensation between the indicators of the method is allowed,
all weights reflect the relative importance of each indicator rather than a trade-offratio.
To define the convenience index for using recycled material, Maurin’s index formal construction
method [
24
] was used again as a reference for the choice of the aggregation function. It is defined as an
average function as follows:
Crm =pteu +pecu +penu
nd(12)
with
Crm
: convenience of the recycled material;
pteu
: technical convenience of the recycled material;
pecu
: economic convenience of the recycled material;
penu
: environmental convenience of the recycled
material; nd: number of aggregated dimensions.

Sustainability 2020,12, 9861 17 of 30
3. Results
3.1. Implementation of the Design for Recycling Proposition
3.1.1. Step 1—Selection and Characterization of the Product
Product’s Selection
The product to be studied is chosen to validate our results on the already known intentions
and approaches implemented by the designers. We chose a product listed in an EPR. Indeed, their
end-of-life processing has been identified as problematic and is therefore the source of significant
management costs [
35
]. We recall that the six products associated with the European EPR sectors are
household packaging, batteries and accumulators, electrical and electronic equipment (EEE), automobiles,
fluorinated gases, and medicines.
We wanted to test the implementation of the approach by validating the material recovery of a
reasonably complex product. Both EEEs and vehicles meet these criteria. However, we have decided to
work on EEEs; these are products with higher stakes, as the end-of-life vehicles (ELV) chain is currently
more efficient than the waste electrical and electronic equipment (WEEE) chain.
The choice of an EEE is still very wide. We have chosen to focus our study on the smartphones
around which our daily lives are increasingly centered. To give an example, seven billion smartphones
have been sold worldwide since 2007 (including 1470 million in 2016) [36].
Like any other product, the smartphone impacts the environment throughout its life cycle.
Its manufacture (from the extraction of raw materials to final assembly) is responsible for about
three-quarters of its impacts, most of which are attributable to the display and complex electronic
components (microprocessors, etc.). Indeed nowadays, more than 70 different materials (including
about 50 metals) are needed to create a smartphone. Some of them are becoming more and more
difficult to obtain. Concerning the end of life, the so-called precious metals are often present in very
small quantities, and often in complex alloys, which makes many of them difficult to recycle. [36]
To reduce the impact, the first rule is to extend its lifespan. However, smartphones are subject to a
renewal cycle that is too fast: Ademe (French Environment and Energy Management Agency) points
out that in France, the smartphone is renewed on average every two years and that 88% of French
people renew it even though it is still working [36].
Within this typology of products, the Fairphone
®
holds a particular place. Fairphone
®
is a company
that aims to develop smartphones designed and produced with minimal environmental impact. Thus,
the second smartphone launched by this company (Fairphone 2
®
) has been designed to be easily repaired
and upgradable. Another special characteristic of this company is its transparency. It shares much of its
production practices to provide insight into what is involved in obtaining materials and components,
as well as the production, transportation, repair, and recycling of the phone. The aim is to provide
businesses and consumers with a better overview of [37]:
•
production practices, working conditions, working hours, and health and safety regulations on
the products that consumers use and buy;
•the origin of raw materials (i.e., transparency in the supply chain);
•the functioning of companies (including economic aspects).
As part of this transparency policy, Fairphone
®
has carried out several well-documented studies
on its products. Most technical, economic, and environmental information is available to the public.
The Fairphone 2®, for example, has been the subject of several studies including the evaluation of its
life cycle impact, its recyclability, cost breakdown, etc. This is why we have chosen to validate our
study using this product.

Sustainability 2020,12, 9861 18 of 30
Product’s Characterization
The Fairphone 2
®
is the first modular smartphone available to consumers. Its structure simplifies
its repairability and consequently increases its lifespan. It is composed of seven modules.
The Fairphone 2
®
BOM is shown in Figure 8. It was largely defined from information published
by Fairphone
®
[
38
–
42
]. However, several hypotheses had to be proposed to complete the missing
information. The results and analyses presented in this article are therefore only valid for our Fairphone
2
®
definition. A more detailed bill of materials (BOM) (of both components and materials) is presented
in another study [6].
Sustainability 2020, 12, x FOR PEER REVIEW 18 of 29
Figure 8. Bill of materials (BOM) of the Fairphone 2® in mass percent.
Compatibility of materials
Compatibility between two materials has been defined concerning recycling (see Section 2.2.4).
In this context, the following findings were made:
• For metals, compatibility is addressed in the literature by the ability to separate impurities from
the material to be recycled. Some authors analyze the impurity distribution rates between the
metal, slag, and gas phases using an element radar map [43,44]. Others use the metal recycling
wheel, which describes the various possibilities for loss and recovery of impurities as well as the
economically viable routes [45,46].
• For plastics, compatibility is approached in the chemical sense, i.e., by the relationship between
the material to be recycled and the impurities that could disrupt its recycling. It is represented
in a matrix form in the literature [20,26,47]. Maier’s matrix was preferred, because it is more
recent and more comprehensive. Information from the Eco3e site on what is tolerated, poorly
tolerated, and not tolerated for recycling regarding glass fiber concentration has been used to
analyze the compatibility of PC Mix and PA Mix plastics [48].
Inspired by the representation mode used for plastics, all compatibilities have been organized
in a matrix. Figure 9 shows the material compatibility matrix for the Fairphone 2®. Two areas can be
identified: in purple, the area containing the compatibility between metals and in orange, the area
containing the compatibility between plastics. Note that there is no information on any of the other
material families, nor on the compatibility between materials of different families (e.g., between
metals and plastics).
Figure 8. Bill of materials (BOM) of the Fairphone 2®in mass percent.
3.1.2. Step 2—Evaluation of Action Levers
The Fairphone 2
®
has been designed in a modular way to make it easier to repair and to be upgraded,
thus prolonging its lifespan. However, it has not been designed to facilitate its recycling, and we thus
expect a low score for recyclability even though the recycling industry could benefit from the modularity
and disassemblability of the smartphone.
The recyclability of the product was defined in the previous section by grouping together three
action levers (see Section 2.2.4): compatibility, diversity, and recyclability of the materials.
The product’s recyclability score is thus defined as the average of the indicators associated with
these three action levers. The indicators are calculated in the following paragraphs and a summary
will be proposed at the end.

Sustainability 2020,12, 9861 19 of 30
Compatibility of materials
Compatibility between two materials has been defined concerning recycling (see Section 2.2.4).
In this context, the following findings were made:
•
For metals, compatibility is addressed in the literature by the ability to separate impurities from
the material to be recycled. Some authors analyze the impurity distribution rates between the
metal, slag, and gas phases using an element radar map [
43
,
44
]. Others use the metal recycling
wheel, which describes the various possibilities for loss and recovery of impurities as well as the
economically viable routes [45,46].
•
For plastics, compatibility is approached in the chemical sense, i.e., by the relationship between
the material to be recycled and the impurities that could disrupt its recycling. It is represented in
a matrix form in the literature [
20
,
26
,
47
]. Maier’s matrix was preferred, because it is more recent
and more comprehensive. Information from the Eco3e site on what is tolerated, poorly tolerated,
and not tolerated for recycling regarding glass fiber concentration has been used to analyze the
compatibility of PC Mix and PA Mix plastics [48].
Inspired by the representation mode used for plastics, all compatibilities have been organized in a
matrix. Figure 9shows the material compatibility matrix for the Fairphone 2
®
. Two areas can be identified:
in purple, the area containing the compatibility between metals and in orange, the area containing the
compatibility between plastics. Note that there is no information on any of the other material families, nor
on the compatibility between materials of different families (e.g., between metals and plastics).
Material compatibility will not be included in our study, as the information available in the literature
is very limited and consequently our matrix remains fairly incomplete. However, we will use the zone of
compatibility between plastics to illustrate the approach. Figure 10 focuses on the plastic compatibility
matrix for the Fairphone 2®.
In the context of the WEEE stream in France, it has been identified that only PP, ABS, and PS are
recovered in the small household appliances stream [
49
]. Therefore, any other material will be considered
as complementary. Table 5details all plastic compatibilities.
Table 5. Plastic compatibilities of the Fairphone 2®.
Compatibility Ci
mb Ci
mc Ci
mCm
PC (polycarbonate) 0.59 0.63 0.63
0.54
PE (polyethylene) 0.50 0.44 0.44
PVC (polyvinyl chloride) 0.44 0.44 0.44
TPU (thermoplastic polyurethane) 0.63 0.88 0.88
PC Mix (PC +glass fibre) 0.69 0.28 0.28
PA Mix (PA +glass fibre) 0.44 0.25 0.25
Other plastics (COC, PSU et PBT *) 0.50 0.69 0.69
Undefined plastic (ABS *) 0.69 0.88 0.69
* Material selected for the study.
It can be seen in this table that while for some materials the
Ci
mb
and
Ci
mc
compatibilities are similar
(e.g., PC and PE) or even equal (e.g., PVC), significant differences may exist for other materials. If we
consider the example of PC Mix (glass-fiber reinforced PC), we can notice that its compatibility as a
base material is good, but it is very poor as complementary material. This statement highlights the
interest of the two reading modes of compatibility. As an example, knowing that the industry does not
recover the PC Mix, the material should be avoided by the designer, because it may compromise the
recycling of other plastics.

Sustainability 2020,12, 9861 20 of 30
Sustainability 2020, 12, x FOR PEER REVIEW 19 of 29
Figure 9. Compatibility matrix of Fairphone 2® materials. * Material selected for the study.
Material compatibility will not be included in our study, as the information available in the
literature is very limited and consequently our matrix remains fairly incomplete. However, we will
use the zone of compatibility between plastics to illustrate the approach. Figure 10 focuses on the
plastic compatibility matrix for the Fairphone 2®.
Figure 10. Compatibility matrix of Fairphone 2® plastics. * Material selected for the study.
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0.5 0.5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0.25 0.5 1 1 Compatible
PC Mix 1 0.5 0 1 1 0 1 1 0.5 Limited compatibilit y
PA Mix 0 0.5 0 1 0 1 0.5 0.5 0.25 Compatible in small quantit ies
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1 0 Not compatible
Undefined plastic (ABS*) 1 0 1 1 0.25 0.25 1 1 0.25 No information
Secondary material
Main material
Stainless steel
Fe
Ag
Al
Au
Co
Cu
Cr
In
Mg
Mn
Ni
Pb
Pd
Pt
Si
Sn
W
Zn
Gd
Nd
Pr
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
Rubber
Epoxy
Polyimide (PI)
Liquid crystal polymer (LCP)
Glass
Graphite
ITO Layer
Liquid crystal
LCO
LiPF6
Stainless steel 1 1 1 1 0.5 0.5
Fe 0.25 1 0 0 0 0.5 0 0.5 0 0.5 0.5 0.5 0 0 0.5 0 0.5 0.5
Ag 1
Al 0.5 0.5 0 1 0 0 0.5 0 0 0.5 0.5 0.5 0 .5 0 0 0.5 0.5 0 0.5
Au 1
Co 1
Cu 1 1 1 1 1 1 1 1 1 1
Cr 1
In 1
Mg 0.5 0.5 0.5 0.5 0.5 1 0.5 0.5 0.5 0 0 .5
Mn 1
Ni 1 1 1 1 1 1 1 1 1 1
Pb 1 1 1 1 1 1 1 1 1
Pd 1
Pt 1
Si 1
Sn 1 1 1 1 1 1
W1
Zn 1 1 1 1 1 1 1 1
Gd 1
Nd 1
Pr 1
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0 .5 0.5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0.25 0 .5 1
PC Mix 1 0.5 0 1 1 0 1 1
PA Mix 0 0.5 0 1 0 1 0.5 0.5
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1
Undefined plastic (ABS*) 1 0 1 1 0.25 0.25 1 1
Rubber 1
Epoxy 1
Polyimide (PI) 1
Liquid crystal polymer (LCP) 1
Glass 1
Graphite 1
ITO Layer 1
Liquid crystal 1
LCO 1
LiPF6 1
Secondary material
Main material
1 Compatible
0.5 Limited compatibility
0.25 Compatible in small quantities
0 Not compatible
0.25 No information
Figure 9. Compatibility matrix of Fairphone 2®materials. * Material selected for the study.
Sustainability 2020, 12, x FOR PEER REVIEW 19 of 29
Figure 9. Compatibility matrix of Fairphone 2® materials. * Material selected for the study.
Material compatibility will not be included in our study, as the information available in the
literature is very limited and consequently our matrix remains fairly incomplete. However, we will
use the zone of compatibility between plastics to illustrate the approach. Figure 10 focuses on the
plastic compatibility matrix for the Fairphone 2®.
Figure 10. Compatibility matrix of Fairphone 2® plastics. * Material selected for the study.
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0.5 0.5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0 .25 0.5 1 1 Compatible
PC Mix 1 0.5 0 1 1 0 1 1 0.5 Limited compatib ility
PA Mix 0 0 .5 0 1 0 1 0 .5 0.5 0.25 Compatible in small quantities
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1 0 Not compatible
Undefined plastic (ABS*) 1 0 1 1 0.2 5 0.25 1 1 0.25 No information
Secondary material
Main material
Stainless steel
Fe
Ag
Al
Au
Co
Cu
Cr
In
Mg
Mn
Ni
Pb
Pd
Pt
Si
Sn
W
Zn
Gd
Nd
Pr
PC
PE
PVC
TPU
PC Mix
PA Mix
Other plastics (PBT*)
Undefined plastic (ABS*)
Rubber
Epoxy
Polyimide (PI)
Liquid crystal polymer (LCP)
Glass
Graphite
ITO Layer
Liquid crystal
LCO
LiPF6
Stainless steel 1 1 1 1 0.5 0.5
Fe 0.25 1 0 0 0 0.5 0 0.5 0 0.5 0.5 0.5 0 0 0 .5 0 0.5 0.5
Ag 1
Al 0.5 0.5 0 1 0 0 0.5 0 0 0.5 0.5 0.5 0.5 0 0 0.5 0 .5 0 0.5
Au 1
Co 1
Cu 1 1 1 1 1 1 1 1 1 1
Cr 1
In 1
Mg 0.5 0.5 0.5 0.5 0.5 1 0.5 0.5 0.5 0 0.5
Mn 1
Ni 1 1 1 1 1 1 1 1 1 1
Pb 1 1 1 1 1 1 1 1 1
Pd 1
Pt 1
Si 1
Sn 1 1 1 1 1 1
W1
Zn 1 1 1 1 1 1 1 1
Gd 1
Nd 1
Pr 1
PC 1 0.5 0 1 0.25 0 1 1
PE 0.5 1 0.5 0.5 0.25 0.25 0.5 0.5
PVC 0 0.5 1 1 0 0 0 1
TPU 0.5 0.5 1 1 0.25 0.25 0.5 1
PC Mix 1 0.5 0 1 1 0 1 1
PA Mix 0 0.5 0 1 0 1 0.5 0.5
Other plastics (PBT*) 1 0 0 0.5 0.25 0.25 1 1
Undefined plastic (ABS*) 1 0 1 1 0.25 0.25 1 1
Rubber 1
Epoxy 1
Polyimide (PI) 1
Liquid crystal polymer (LCP) 1
Glass 1
Graphite 1
ITO Layer 1
Liquid crystal 1
LCO 1
LiPF6 1
Secondary material
Main material
1 Compatible
0.5 Limited compatibility
0.25 Compatible in small quantities
0 Not compatible
0.25 No information
Figure 10. Compatibility matrix of Fairphone 2®plastics. * Material selected for the study.
Overall, the material compatibility indicator provided a score slightly higher than the average
value in our range (0.5). The plastics of the Fairphone 2®are thus fairly compatible with each other.

Sustainability 2020,12, 9861 21 of 30
Diversity of materials
Material diversity has been defined as a function inversely proportional to the entropy (see Section 2.2.4).
The entropy of the smartphone is first determined from the material concentrations of the Fairphone
2®(see Figure 8):
H=3.38
The material compatibility score is then calculated:
Dm=0.23
The indicator value is in the lowest range of values indicating that the product has a wide diversity
of materials.
Recyclability of materials
Material recyclability has been defined as a function of material recycling rates and material purity
rates (see Section 2.2.4).
To obtain these rates, an end-of-life scenario must be defined. Among the possible EoL scenarios [
50
],
the treatment composed of shredding, physical pre-processing, and metallurgy was chosen, because it
best represents the current treatment of EoL smartphones. The purity level was set to 1 for all materials,
becausethere wasnoavailable informationforthisscenario. Pleasenotethatthis is themostoptimisticsituation.
Table 6contains the recyclability score obtained by each material as well as the score for all Fairphone
2
®
materials. The value of the index is relatively low, meaning that the materials in the product are
generally poorly recycled.
Table 6. Recyclability of Fairphone 2®materials.
Materials rmMaterials rmRm
Stainless steel 0.99 Pr (praseodymium) 0.00
0.29
Fe (iron) 0.70 PC (polycarbonate) 0.95
Ag (silver) 0.80 PE (polyethylene) 0.00
Al (aluminium) 0.10 PVC (polyvinyl chloride) 0.00
Au (gold) 0.90 TPU (thermoplastic polyurethane) 0.00
Co (cobalt) 0.80 PC Mix (PC +glass fibre) 0.00
Cu (copper) 0.90 PA Mix (PA +glass fibre) 0.00
Cr (chrome) 0.00 Other plastics (COC, PSU et PBT *) 0.00
Mg (magnesium) 0.90 Undefined plastic (ABS *) 0.95
Mn (manganese) 0.00 Rubber 0.00
Ni (nickel) 0.80 Epoxy 0.00
Pb (lead) 0.00 Polyimide (PI) 0.00
Pd (palladium) 0.00 Liquid crystal polymer (LCP) 0.00
Pt (platinum) 0.90 Glass 0.00
Si (silicon) 0.00 Graphite 0.00
Sn (tin) 0.60 ITO Layer 0.64
W (tungsten) 0.00 Liquid crystal 0.00
Zn (zinc) 0.00 LCO 0.81
Gd (gadolinium) 0.00 LiPF6 0.00
Nd (neodymium) 0.00 Others 0.00
* Material selected for the study.

Sustainability 2020,12, 9861 22 of 30
Recyclability of the product
The recyclability score of the product is defined as the average of the performance indicators
associated with the action levers calculated above. The recyclability score of the Fairphone 2
®
is 0.26,
which is poor.
It should be noted that material compatibility could not be included in our study, because the
information available in the literature is limited, and consequently our matrix is very incomplete.
3.1.3. Step 3—Identification of Product’s “Hotspots”
From the results obtained in the previous step, a score chart can be constructed (see Figure 11)
and then be used to identify the hotspot of the product (i.e., the action lever with the lowest score).
Sustainability 2020, 12, x FOR PEER REVIEW 21 of 29
Table 6. Recyclability of Fairphone 2® materials.
Materials
𝒓𝒎
Materials
𝒓𝒎
𝑹𝒎
Stainless steel
0.99
Pr (praseodymium)
0.00
0.29
Fe (iron)
0.70
PC (polycarbonate)
0.95
Ag (silver)
0.80
PE (polyethylene)
0.00
Al (aluminium)
0.10
PVC (polyvinyl chloride)
0.00
Au (gold)
0.90
TPU (thermoplastic polyurethane)
0.00
Co (cobalt)
0.80
PC Mix (PC + glass fibre)
0.00
Cu (copper)
0.90
PA Mix (PA + glass fibre)
0.00
Cr (chrome)
0.00
Other plastics (COC, PSU et PBT *)
0.00
Mg (magnesium)
0.90
Undefined plastic (ABS *)
0.95
Mn (manganese)
0.00
Rubber
0.00
Ni (nickel)
0.80
Epoxy
0.00
Pb (lead)
0.00
Polyimide (PI)
0.00
Pd (palladium)
0.00
Liquid crystal polymer (LCP)
0.00
Pt (platinum)
0.90
Glass
0.00
Si (silicon)
0.00
Graphite
0.00
Sn (tin)
0.60
ITO Layer
0.64
W (tungsten)
0.00
Liquid crystal
0.00
Zn (zinc)
0.00
LCO
0.81
Gd (gadolinium)
0.00
LiPF6
0.00
Nd (neodymium)
0.00
Others
0.00
* Material selected for the study.
Recyclability of the product
The recyclability score of the product is defined as the average of the performance indicators
associated with the action levers calculated above. The recyclability score of the Fairphone 2® is 0.26,
which is poor.
It should be noted that material compatibility could not be included in our study, because the
information available in the literature is limited, and consequently our matrix is very incomplete.
3.1.3. Step 3—Identification of Product’s “Hotspots”
From the results obtained in the previous step, a score chart can be constructed (see Figure 11)
and then be used to identify the hotspot of the product (i.e., the action lever with the lowest score).
Figure 11. Recyclability of the Fairphone 2®.
A designer confronted with these results can easily identify that the action lever the most
appropriate to be used to improve the recyclability of the product is the diversity of materials.
Figure 11. Recyclability of the Fairphone 2®.
A designer confronted with these results can easily identify that the action lever the most appropriate
to be used to improve the recyclability of the product is the diversity of materials.
3.1.4. Step 4—Proposal of Relevant Guidelines
The guidelines proposed to the designer are those that allow improving the performance of the
product’s hotspot. In our case, those who are focused on the diversity of materials (see Table 2):
•minimize the number of different types of materials;
•avoid the mixing of materials in assemblies;
•use a monomaterial strategy: favor using a single material per product or sub-assembly.
3.2. Implementation of the Design from Recycling Proposition
3.2.1. Step 1—Selection of the Recycled Material
Fairphone
®
states on its website that it uses recycled polycarbonate, copper, and tungsten in its
products. To validate our proposed method, we decided to assess the convenience of using one of these
materials in a circular economy scenario. In other words, we seek to assess the convenience of using
recycled material produced by the WEEE chain for the production of an EEE. Recycled polycarbonate
from the French WEEE chain was chosen as a case study.
3.2.2. Step 2—Evaluation of Convenience Indicators
Assessing the Technical Convenience of Using Recycled Materials
The technical convenience of using a recycled material was defined as a function of the purity rate
and the supply reliability (see Section 2.3.2). The following considerations were taken into account:

Sustainability 2020,12, 9861 23 of 30
•
The Urban Mines Chair specifies that the impurity of recycled plastics from the WEEE sector is
between 12% and 15%. Due to a lack of information on the PC, we used the highest value in this
range for our study;
•
The following hypothesis is retained: the company responsible for supplying the recycled material
has been checked and validated by the purchasing department. Hence, a value of 1 has been
assigned to the indicator of supply reliability.
The technical convenience of the using recycled PC is thus presented in Table 7.
Table 7. Technical convenience of the using recycled PC.
τpsrpteu
PC 0.85 1.00 1.15
The indicator provides a score of 1.15, which is above the reference value (equal to 1). The use of
recycled PCs is technically less convenient than the use of virgin materials because of its impurities.
Assessing the Economic Convenience of Using Recycled Materials
The economic convenience of using a recycled material has been defined as the price ratio of
recycled material (v
ec
) to virgin material (v
ec,ref
) (see Section 2.3.2). The economic convenience of the
using recycled PC is thus presented in Table 8:
Table 8. Economic convenience of the using recycled PC.
vec (€·g−1)vec,ref (€·g−1)pecu
PC 2.86 ×10−33.49 ×10−30.82
The indicator provides a score of 0.82, which is below the reference value (equal to 1). This implies
that the use of recycled PCs is economically more attractive than the use of virgin materials.
Assessing the Environmental Convenience of Using Recycled Materials
The environmental convenience of using a recycled material was defined as the ratio between
the environmental impacts of end-of-life processing (v
en
) and those of raw material production (v
en,ref
)
(see Section 2.3.2).
To conduct this calculation, the impacts were calculated using the CML method with the functional
unit being producing one kilogram of PC (virgin or recycled). One should note that:
•
the environmental impact of the production of primary (i.e., virgin) raw materials was calculated
using the Ecoinvent 3 database;
•
the environmental impact of the production of secondary (i.e., recycled) raw materials was
calculated using the database created by Eco-systèmes and Récylum [
49
]. It enables manufacturers
to assess the environmental impacts or benefits of recycling more than 60 materials obtained
from WEEE;
•the selected impact categories are the same as those used in Fraunhofer’s report [38].
The environmental convenience of using recycled PC as well as those associated with each impact
category are detailed in Table 9.
We can observe that from an environmental point of view, the recycling of PC is very advantageous
for the categories of climate change, ecotoxicity, and depletion of fossil fuels. On the other hand,
in terms of human toxicity and especially on resource depletion, it is the production of virgin materials
that has the least impact and is therefore the most interesting.

Sustainability 2020,12, 9861 24 of 30
Table 9. Environmental convenience of using recycled PC.
Impact Category Indicator Units ven ven,ref pk
enu penu
Climate change GWP kg CO2eq 1.61 ×1008.20 ×1000.20
1.29
Resource depletion ADP (elements) kg Sb eq 7.56 ×10−61.59 ×10−64.75
ADP (fossils) MJ 1.34 ×1019.25 ×1010.14
Human toxicity Humantox kg DCB eq 5.46 ×10−14.16 ×10−11.31
Ecotoxicity Ecotox kg DCB eq 6.70 ×10−32.18 ×10−10.03
The environmental convenience index, constructed from the aggregation of the indicators for each
impact category, provides a score of 1.29, which is above the reference value (1). This implies that the
use of recycled PCs is environmentally less advisable than the use of virgin materials.
3.2.3. Step 3—Evaluation of Convenience Index
The index convenience of using recycled materials is calculated by aggregating the convenience
of use in the technical, economic, and environmental dimensions (see Section 2.3.4). The convenience
of using recycled PC is illustrated in Figure 12 and detailed in Table 10.
Sustainability 2020, 12, x FOR PEER REVIEW 23 of 29
Assessing the Environmental Convenience of Using Recycled Materials
The environmental convenience of using a recycled material was defined as the ratio between
the environmental impacts of end-of-life processing (ven) and those of raw material production (ven,ref)
(see Section 2.3.2).
To conduct this calculation, the impacts were calculated using the CML method with the
functional unit being producing one kilogram of PC (virgin or recycled). One should note that:
• the environmental impact of the production of primary (i.e., virgin) raw materials was calculated
using the Ecoinvent 3 database;
• the environmental impact of the production of secondary (i.e., recycled) raw materials was
calculated using the database created by Eco-systèmes and Récylum [49]. It enables
manufacturers to assess the environmental impacts or benefits of recycling more than 60
materials obtained from WEEE;
• the selected impact categories are the same as those used in Fraunhofer’s report [38].
The environmental convenience of using recycled PC as well as those associated with each
impact category are detailed in Table 9.
Table 9. Environmental convenience of using recycled PC.
Impact Category
Indicator
Units





Climate change
GWP
kg CO2 eq
 
 
0.20
1.29
Resource depletion
ADP (elements)
kg Sb eq
 
 
4.75
ADP (fossils)
MJ
 
 
0.14
Human toxicity
Humantox
kg DCB eq
 
 
1.31
Ecotoxicity
Ecotox
kg DCB eq
 
 
0.03
We can observe that from an environmental point of view, the recycling of PC is very
advantageous for the categories of climate change, ecotoxicity, and depletion of fossil fuels. On the
other hand, in terms of human toxicity and especially on resource depletion, it is the production of
virgin materials that has the least impact and is therefore the most interesting.
The environmental convenience index, constructed from the aggregation of the indicators for
each impact category, provides a score of 1.29, which is above the reference value (1). This implies
that the use of recycled PCs is environmentally less advisable than the use of virgin materials.
3.2.3. Step 3—Evaluation of Convenience Index
The index convenience of using recycled materials is calculated by aggregating the convenience
of use in the technical, economic, and environmental dimensions (see Section 2.3.4). The convenience
of using recycled PC is illustrated in Figure 12 and detailed in Table 10.
Figure 12. Convenience of using recycled PC.
Figure 12. Convenience of using recycled PC.
Table 10. Convenience of using recycled PC.
Technical Convenience Economic Convenience Environmental Convenience Use Convenience
PC 1.15 0.82 1.29 1.09
When analyzing these values, the following observations can be made:
•the technical convenience is not confirmed, as it is 15% above the reference value (100% purity);
•
the economic convenience is confirmed, as it is 18% below the reference value (i.e., the price of
virgin PC);
•
theenvironmentalconvenienceisnotconfirmed, as it is 29%abovethereference value(the environmental
impacts of the production of virgin PC). However, it should be noticed that this recycled material
might be environmentally convenient in another product. Another possibility is that recycled PC
from another industry might be environmentally more convenient;
•
the overall convenience is not confirmed, because the score provided by the aggregation index is
9% above the reference value. Recycled PC is, overall, less interesting than virgin PC.
The convenience index for the use of recycled material provides a score of 1.09, which is above the red
line indicating the reference value (1). This implies that the use of recycled PCs coming from the WEEE
chain is less recommended than the use of virgin materials, as it is only economically advantageous.

Sustainability 2020,12, 9861 25 of 30
4. Discussion
4.1. Design for Recycling Proposition
An inventory of design for end-of-life approaches has shown that the results of the recoverability
assessment need to be presented in the form of design guidelines (such as those used in any design for X
approach). To address the issue, an indicator-based design approach has been developed. The proposed
indicators create a link between product assessment and the ecodesign guidelines.
Indicators assessing product performance have been defined for each of the identified action
levers. It should be noted that the indicators have been chosen or constructed with the objective of the
simplicity of use and interpretation; the designer must be able to use them quickly and easily.
To test the proposal, the Fairphone 2
®
was studied. A low recyclability score was expected, as the
phone was not designed to improve its recycling, even if the recycling industry could benefit from
its modularity and disassemblability. It can be noted that the low score on the recyclability of the
product is consistent with the analysed product, as it was not designed to be recycled but repaired.
The low value is explained by the fact that (i) the product has a wide variety of materials, and (ii) these
materials have low recyclability. When a designer is confronted with such results, he can identify that
the most urgent action lever to be addressed is the diversity of materials.
The design-for-recycling approach has been proposed to allow designers to focus on the areas that
need to be improved first. It can be observed in the case study that we can identify the characteristics
of the product that are the least efficient in terms of recycling and to propose appropriate guidelines to
improve them. This is a big improvement in comparison to traditional design-for-recycling approaches,
which consist solely of a set of design guidelines [12,16,20].
The case study thus made it possible to validate this proposal. However, some limitations have
been identified for the proposed approach:
•
It was not possible to carry out an exhaustive literature search to define each of the performance
indicators for the 24 action levers and the three regulatory constraints. This implies that there may
be other very relevant indicators that have not been identified. However, careful attention will be
needed before selecting any new indicator, especially to its ease of use so that it can be effectively
used in the design phase;
•Difficulty in obtaining the detailed EoL information needed to use the indicators.
•
The data used to assess the compatibility and recyclability of materials needs to be updated as
constantly as possible (for the analysis to best reflect the reality of the recycling chains).
•
The recyclability analysis on the Fairphone 2
®
only considered the phone itself. Accessories (such as
USB cable, charger, and headphones) were not part of the scope of the study.
Lastly, several perspectives have been identified for the proposed design approach:
•
The first perspective is related to the fact that the indicators linking the design for EoL guidelines
have only been confronted with the Fairphone 2
®
. Therefore, the next step is to test the set of indicators
on other “non-modular” smartphones and verify that similar results are obtained.
•
Another test to be carried out is to compare the approach with other product typologies. Flat
screens, which have been widely discussed in the literature, could be a good option [31,51,52].
•
Finally, we believe that the development of a digital platform connected to design software would
allow capitalizing on all the expertise developed in this work. The objective is to allow designers
to better understand the proposed tools throughout the design process. Such a platform would
also ensure the availability and updating of the technical, economic, and environmental databases
gathered to feed the data of the current and future studies.

Sustainability 2020,12, 9861 26 of 30
4.2. Design from Recycling Proposition
Promoting the use of recycled material in product design is a fundamental strategy for achieving
a circular economy. To this end, a second tool allowing to assess the convenience of using recycled
material has been proposed. It is part of a design-from-EoL approach.
To test the proposal we looked again at the Fairphone
®
, as it states that it uses recycled polycarbonate,
copper, and tungsten in its products. To validate our tool, we decided to assess the convenience of using
one of these materials. Recycled polycarbonate was chosen as a case study.
Prior to this study, a value below the reference was expected for the technical convenience indicator
due to treatment impurities. For the economic and environmental dimensions, we expected that the
use of recycled material would be more convenient than the use of virgin material. This was found not
to be true for the environmental dimension and the overall score. The case study made it possible to
validate this proposal and to highlight the importance of the joint analysis of the three dimensions.
Furthermore, the analysis of a graph such as the one shown in Figure 12 allows the designer to verify
quickly the convenience, because anything above the red line (reference value) is not considered to
be convenient.
The proposed method for assessing the convenience of using recycled material has been created
so that the designer can easily and objectively assess the technical, economic, and environmental
convenience of using recycled material. Within this framework, we are proving that the proposal meets
its objective. However, some limitations have been identified:
•Difficult access to information (especially environmental data).
•
The technical, economic, and environmental data used to assess the convenience indicators needs
to be constantly updated.
•
No consideration of the impact of the decrease in the purity of the materials. On the one hand, this
loss conditions the resale market of the material (which might be purely and simply unsaleable),
and on the other hand, it might impact the technical performance of the product.
•
The convenience of using a recycled material may change over time, so it cannot be reduced to a
one-time analysis. A dynamic assessment is thus needed. The economic convenience is a good
example, as it may fluctuate over time due to the availability of the metals. Indeed, knowing that
smart device production is rising every year and that our planet has a limited reserve of rare-earth
and precious metals, it is foreseeable that the price of some metals will increase over time.
•
The convenience assessment does not take into account either the economic or environmental
impact of the whole production. Indeed, a slight cost reduction can induce sometimes a big
save when the whole production is considered. The same happens for environmental impacts,
and therefore this can be a decisive factor for the designer.
Several perspectives are foreseen for the proposed design approach:
•
The approach has only been tested on one material to show above all the interest of this type
of approach. The first perspective would be to first conduct further tests on the same material,
and then on others in a second step. However, it should be noted that the approach can only be
fully validated when facing a real situation within a company.
•
The possible deterioration of the technical performance of the product caused by the decrease in
the purity of the materials should be included in the technical convenience assessment.
•
The environmental and economic impact of the whole production and the associated savings
should also be included in their respective convenience assessment.
•
As with the design-for-EoL approach, the development of a digital platform integrated into the
design process is necessary to capitalize on the approach on the one hand and to consolidate and
update databases on the other hand.

Sustainability 2020,12, 9861 27 of 30
5. Conclusions
Re-Cycling is a design approach looking to improve circular economy by improving and simplifying
decision-making in product design. It is constructed by grouping two tools:
•
On the one hand, the design-for-recycling proposition allows identifying the product characteristics
that are the least performant (concerning recycling) and proposes the most accurate design
guidelines to improve them.
•
On the other hand, the design-from-recycling proposition allows the convenience of using recycled
materials within a technical, economic and environmental point of view to be easily and objectively
assessed. A global score is also proposed to simplify decision making.
The proposed approach favors the development of a link between designers and stakeholders in
the EoL treatment chain. This link can also be strengthened by proposing the complementary approach
(i.e., an approach that integrates recycling tools for and from the design process).
It is important to state that the Re-Cycling design approach is not restricted to electrical and
electronic equipment. Indeed, in this article, we want to show the implementation of our approach on
a reasonably complex product with high recycling stakes. However, it can also be used on other types
of products (e.g., vehicles, furniture, etc.). The only thing to be taken into account is that while the
approach remains the same, the databases to be used must be specific (i) to the recovery chain that
processes the selected product (for the design-for-recycling proposal) and (ii) to the recovery chain that
produces the selected recycled material (for the design-from-recycling proposal).
Author Contributions:
Writing—original draft preparation, J.M.L.; Writing—review and editing, S.P., C.C. and
N.P. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by Ademe (French Environment and Energy Management Agency).
Acknowledgments:
The authors would like to thank EcoSD Network (French association encouraging collaboration
between academic and industrial researchers in ecodesign fields) for their aid and support.
Conflicts of Interest:
The bill of materials used in this article to represent the Fairphone 2
®
was developed largely
from information provided by Fairphone
®
. However, several hypotheses had to be proposed to complete the
missing information. The results and analyses presented in this article are therefore only be valid for our Fairphone
2®definition.
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