Recycling plastics from e‐waste: Implications for effective eco‐design

This paper presents five case studies on waste electrical and electronic equipment (WEEE) recycling to provide a coherent overview on the likely impact of eco‐design measures on recycling of plastics used in energy‐related products within the EU. Whilst some eco‐design measures, such as improving disassembly of plastic parts, may generally benefit recycling operations, other measures were found to be ineffective or requiring further investigation. For example, product polymer marking, and provision of product‐specific information was rarely utilized by participant organizations, if at all. Additionally, this study highlights a disconnect between the aims of substance bans as an eco‐design measure and the impact upon plastics recycling in practice. Future research could help with quantitative and/or statistical analysis of WEEE processing to investigate across a wider selection of recyclers and recycling processes. Despite 20 years of research on eco‐design, it appears that EU eco‐design policies and voluntary initiatives are still being devised without adequate understanding of their impact on different types of recycling practices. Empirical research on recycling processes can provide important insight to ensure eco‐design measures are effective and avoid unintended consequences for the environment.

Whilst Europe is the highest collector of e-waste globally, only 42.5% of 12 Mt annually is officially collected and properly recycled (Forti et al., 2020).
The EU is also targeting plastics use within EEE (European Commission, 2015, 2018), as it contributes around 2.6 Mt to WEEE annually, with only around 560 kt recycled (Haarman et al., 2020).WEEE plastics can be technically difficult to recycle (Wäger et al., 2012) and may contain hazardous substances, such as flame retardants, which are problematic for recycling (Wagner & Schlummer, 2020).If such chemicals enter the natural environment, for example, through uncontrolled burning or slow degradation in landfill, they may pose risks to both environmental and human health (Forti et al., 2020).Therefore, the EU's plastics strategy (European Commission, 2018) aims to improve the recyclability of plastics from WEEE through the Eco-Design Directive (2009/125 1 ).There are various EU eco-design requirements for the recyclability of EEE plastics, which vary by product group.Following an analysis of the various EU proposals and regulations by the authors, Table 1 provides a unique outline of relevant examples following a review of eco-design policy documents, alongside other non-regulatory measures such as those within voluntary agreements, ecolabels, and product standards.ICT and other similar consumer electronics are the focus of this review as they generally have the widest range of eco-design measures (legislation and voluntary approaches) and are usually collected together for EoL treatment and recycling.
Eco-design is widely advocated as a method to improve environmental characteristics of products, for example, design for recycling (DfR; Hauschild et al., 2005;Kriwet et al., 1995;Li et al., 2015;Luttrop & Lagerstedt, 2006).However, there are several issues to consider when applying eco-design in practice.Eco-design options for electronics should not be too generic and should be customized to specific contexts and applications (Boks & Stevels, 2007).
Although a number of studies have evaluated plastics recycling, the majority of these focus on packaging (Eriksen et al., 2019;Faraca & Astrup, 2019) or plastics from end-of-life (EoL) vehicles (Corabieru et al., 2014;Miller et al., 2014).Information regarding the specific management and recycling of plastics within WEEE is limited in comparison (Hopewell et al., 2009;Ragaert et al., 2017).General information on WEEE recycling processes is available on a national level (DEFRA, 2007;Makenji & Savage, 2012, Ragaert et al., 2017), but information on the specific processes used appears scant as there is no universal approach recyclers use (JRC, 2014) and technologies tend to be proprietary (Baxter et al., 2014).Previous studies relating to eco-design of plastics within EEE are relatively outdated (APC, 1999;D'Anjou et al., 1995), lack sufficient evaluation from a WEEE plastics perspective versus general WEEE (Hultgen, 2012), or are specific to certain product groups and specialized recycling processes (Masanet et al., 2002;Wagner et al., 2019).Overall, empirical data is required to provide a more coherent overview on if the eco-design measures put forward for EEE product groups are likely to help improve EoL recycling of plastics from WEEE in practice.Therefore, this research aims to investigate the challenges and opportunities to improve the effectiveness of eco-design approaches and requirements for EEE (Table 1) in helping improve EU plastics recycling at EoL using specific case studies on plastics recycling from WEEE within the EU.
There are several key trends impacting plastics recovery from WEEE.First, increasing plastics recovery and recycling from WEEE is becoming increasingly important: the share of plastics used in EEE has increased from around 14% in 1980 to between 20% and 30% (Buekens & Yang, 2014;Yang et al, 2013).Second, there has been a shift from manual to automated processing of WEEE and plastics within WEEE (Masanet et al., 2002), and also several new recycling technologies are improving recovery rates (Buekens & Yang, 2014;Sahajwalla & Gaikwad, 2018;Wagner et al., 2019).
Third, an increasing variety of polymer types and composite plastics are appearing in the waste stream (Corabieru et al., 2014), so the general composition of WEEE is changing over time (Martinho et al., 2012;Schlummer et al., 2007).It is challenging to determine the number of operations in Europe recycling plastics from WEEE, as opposed to other sources of plastics.An EU-wide certification scheme for the recycling of plastic waste, EUCertPlast, has certified 20 recyclers of Acrylonitrile Butadiene Styrene (ABS) plastic (commonly associated with WEEE) out of around 300 plastic recyclers.Although some attempts have been made to review the overall fate of WEEE plastics (Haarman et al., 2020), without clear consideration of how plastics are recycled, it is not possible to determine the likely effectiveness of any measures aiming to increase the recyclability of products at the design stage.

METHODS
An expert case study approach was used to understand the views of different European WEEE recyclers on how the eco-design measures listed in Table 1 were likely to affect their plastics recycling processes.Site visits and interviews were undertaken at five separate organizations between October 2018 and October 2019.An exploratory case study approach was used as it is particularly appropriate where issues are multiple and too complex for exploration by empirical or quantitative methods (Yin, 1994), and where current knowledge and understanding is limited (Eisenhardt, 2002).Similar approaches have also been used to good effect to understand stakeholder views on future WEEE policy, including WEEE recyclers (Kunz et al., 2018).
Three plastics re-processors were investigated as indicative examples of EU recycling practices.Subsequently, two sites of initial WEEE treatment were added to better understand the differences between manual and automatic WEEE disassembly and the impacts on subsequent recycling of plastics from WEEE.Altogether, these cases were selected to broadly represent the different types of contemporary WEEE and plastic recycling processes in Europe, operators following applicable recycling laws and standards, and operators processing relatively substantial volumes TA B L E 1 Review of mandatory regulations and voluntary measures related to the recycling of plastics used in electronic and electrical equipment.

Ecolabels
Eco-design measure  Limits to coatings on plastics, e.g., paints Coating ban exemptions for recycled plastics

Ecolabels
Eco-design measure Set a target for % of product that shall be recyclable  The opportunity to participate was advertised through various means (including direct email, contact to trade associations, networking events, etc.) to recruit companies willing to participate.The participants were recruited under conditions of anonymity and understanding that some aspects of process technology would remain confidential.Each study was then categorized according to the type of WEEE/plastics processing undertaken (see Tables 3 and 5), based on information provided by the interviewees (which varied depending on the use of proprietary processes, e.g., organizations C and D); articles, presentations, and reports published by the companies themselves; and wider literature on plastics and WEEE recycling available describing the types processes and technologies used by the recyclers.References are not included here to preserve the anonymity of the cases.Semi-structured interviews were then used to explore the views of each recycler on the effectiveness of eco-design approaches with regard to their recycling processes.
A three-stage protocol was used for consistent interactions with the participant organizations and is provided in S.1.The study results, including interview transcripts, were codified using a list of pre-determined codes based on the topics in the protocol document to organize and complete individual reports.To further identify key themes and issues, the reports were re-codified using a more inductive approach (Hsieh & Shannon, 2005).This two-step coding process was an efficient way to summarize the findings from each case study and to enable comparison and overall interpretation of a large variety of data.This allowed analysis concerning the original research aim and the uncovering of additional information.

RESULTS
The case studies are presented in two parts: the first provides a summary of the organizations' recycling processes as the context for each case study.The second provides the results and insights from the respondents regarding the potential for increased recycling for different eco-design measures listed in Table 1.This study focuses mainly on implications for eco-design approaches, but further information on the processes for each recycler is available in S.2.The following table is used throughout this section to refer to specific illustrative quotes from the interviewees.

WEEE
WEEE Plastics recycling involves two main steps, shown in Figure 1: first, "plastics-rich" fractions are separated from WEEE in a pre-processing stage and then sorted by polymer type.
All the participating organizations perform WEEE pre-processing.Cases B, C, and D have in-house plastics recycling operations, whereas A and E rely on third-party service providers for subsequent plastics recycling (see Table 5).
Recyclers use either manual disassembly (E) or mechanical shredding and separation techniques (D) during pre-processing, or a combination of both (A, B, and C).Organization E uses solely manual disassembly and sorting (except for hard disk drives due to data protection requirements) and, therefore, can sort larger pieces of material into separate output streams, decreasing the risk of losing valuable materials which automatic processing may disperse into unrecoverable fractions (Chancerel et al., 2009), but they process significantly less WEEE.A, B, and C include some manual disassembly to access hazardous material and valuable components before granulation.In these cases, there are up to two "manual picking" stages, usually before and following initial coarse mechanical fragmentation of WEEE.Abbreviation: X, operations undertaken by the participant organization.Organization D is limited by their input material and unable to manually process large items within the mix of waste processed on site (including vehicles, light iron scrap), so is primarily shredded.The shredder residue is separated into different material outputs using a variety of technologies (Table 3), and the plastic-rich fraction is processed again using similar equipment to maximize plastic purity.Organizations using automated processing technology (A, B, C, and D) generally had similar types of equipment and an adaptable set-up that can be configured as required.

WEEE CollecƟon
A separate recycling process may be warranted for specific types of WEEE where sufficient volumes are available or there are concerns about the waste product received.For example, organization A receives a high number of LCD TVs, which are manually dismantled due to the risk from mercury-containing back-lights.However, specialized processing of WEEE, especially small mixed WEEE, is challenging due to the diversity of products.

Plastics
The next stage is the re-processing and recycling of the plastic-rich output streams from the initial WEEE pre-processing.(Vanegas et al., 2017).B and D noted some exceptions, for example, to process non-black plastics, separate circuit board fragments from plastics, or to increase purity of a single polymer stream.Sink-float is the dominant method for sorting polymers due to its low cost and commercial scalability (Ragaert et al., 2017).However, sole use of density-based technologies is unlikely to satisfy purity requirements due to the overlapping density profiles of plastics (see Table 4, Q1).
The waste fractions arising from these separation steps can include unwanted polymers, hazardous materials such as brominated flame retardants (BFRs) and phthalates (see Table 4, Q2).Separation of these wastes is ensured by setting the flotation tanks to specific densities based on the properties of the incoming material (see Table 4, Q3).In all cases, the waste fractions are sent to high-intensity incinerators due to the presence of plastics containing hazardous substances.The waste fraction is around 40% at B, between 50% and 70% for C, and at D roughly 50% recovered into extruded pellets, and 50% a mixture of other products (e.g., mixed aggregate chip) and waste.
Additional technologies are also used to further separate polymers after the wet, density-based process to try and maximize the product yield.
However, the cost is always a consideration for recyclers, which is influenced by market demand (see Table 4, Q4).
After the separation into single polymer mixtures, plastics are compounded into polymer pellets, ready to use as raw material.For C and D, this takes place at the same facility as the polymer separation, but for B, compounding for one polymer takes place at a separate facility, with others sold to other compounders.Compounding requires the extraction of impurities, such as non-plastic material, often achieved by using a melt filter (a mesh to filter the melted plastic).To ensure consistency of polymer properties, organizations may blend batches of processed plastic flakes before melting and conduct laboratory testing of material before and after pelletization.The main outputs are single polymer (or polymer blend) pellets, but the processing of plastic-rich fractions also can yield lower grade mixed plastic chip, lower quality plastics waste material for solid recovered fuel (SFR), and a metal-rich fraction.

Effectiveness of EU eco-design measures
The effectiveness of different eco-design measures for improving plastics recycling is presented in this section, analyzing the interview responses from each organization and considering the different recycling processes.Table 7 provides an overview of the results.Each type of eco-design measure is classified as either "Low," "Medium," or "High" in terms of its likely potential for increasing plastic recycling at each processing stage.
"Low" meaning the majority of respondents believed the measure would make no or very little difference to their plastics recycling rates, "Medium" that they believed it would have some or moderate influence on their recycling rates, but with limitations, and "High" where respondents believed their recycling rates could be notably or substantially increased.Where further investigation is needed to determine the effectiveness due to conflicting or a lack of information, then the measure is classified as a range, for example, Low-High.These results are then discussed in more detail below.

Waste
F I G U R E 2 Generalized recycling process for plastics from waste electrical and electronic equipment.

Disassembly
Eco-design approaches relating to the ability to disassemble a product and joining techniques are generally aimed at initial WEEE treatment.The importance of designing for disassembly to separate EEE into different material fractions for recycling is well noted (Li et al., 2015).Recently, approaches have focused on the removability of plastic parts based on size and/or type (e.g., voluntary agreements for games consoles vi and imaging equipment iv ).However, case study respondents argued that such a requirement would have minimal effect on products disassembled using solely mechanical processes, for example, shredding.
Another proposed eco-design approach is to reduce non-separable connections between different materials.The respondents did highlight certain materials that can cause more issues for plastics recyclers than others, if not easily separable, for example, wood.As an absorbent and buoyant material, wood tends not to sink during wet density-based sorting processes, rather staying present in the lighter, valuable plastics mix, thus requiring further processing using different technology.Therefore, maximizing the separation of wood from WEEE plastics before it reaches the plastic re-processor is preferable.Organization A tries to achieve this by removing wood-containing objects at the manual picking stage before the waste enters the impact chamber (see Table 4, Q5).Therefore, according to the respondents, limiting connections between plastic and certain materials, such as wood, would likely increase recycling efficiency.

TA B L E 4
In-text explanatory and illustrative quotations from interviewees.C Some measures require permanent adhesives to be avoided, for example, to join different materials, although some previous research has indicated that they may not negatively impact recyclability (Masanet et al., 2002).All organizations used some type of size reduction step to ensure materials were completely separated (see Table 4, Q6).Organization D did note that not all materials are effectively removed from plastics during size reduction processes.Metal screws are a particular problem as they can then block and erode melt filters during extrusion (see Table 4, Q7).

Quote reference
However, the separation of metal from plastic was not raised as an issue by B, except in the instance where large pieces of, for example, stainless steel, may break granulation equipment (see Table 4, Q8).This conflicting information makes it difficult to determine the true benefits of eco-design measures for plastics recycling that limit certain types of connections or try to ensure separability of different materials.However, it does appear that in some cases, they may be useful and in others, although not useful, not detrimental either, and therefore these measures may increase recycling efficiency by reducing the risk of contaminating material in the output streams.

TA B L E 5
Processes relating to the disassembly and separation of waste electrical and electronic equipment materials.

Hydrophobicity/wettability
Froth flotation A more expensive and complex separation process which relies on different hydrophobic properties of polymers.Polymers are separated in a water container, as continuous air addition (creating froth) adheres to the hydrophobic particles and floats upward for recovery.Selective chemical additions can change the hydrophobicity of plastics.

Triboelectric Electrostatic sorting
Separation is based on the electrical conductivity properties of polymers.Clean and dry plastics are charged using friction, passed through an electrical field and separated by deflecting toward an electrode.The method is dry, so avoids generation of wastewater, and works well with polymers of similar densities.
Spectral or visual aspect X-ray detection (XRF or XRT) Near infra-red (NIR) spectroscopy Optical sorting based on properties such as color These sorting methods usually detect target plastics on a pre-set property such as color and usually separates using a pneumatic air jet.However, the efficiency of these techniques reduces as the variety of plastic types increases.

Processing of hazardous substances
Whilst legislation restricting hazardous substance use in new products has been enacted to protect human and environmental health (e.g., Regulations 1907/2006 3 , 2019/1021 4 ; Directive 2011/65 5 ), respondents reported that there have been unintended consequences for plastics recycling, including an increase in plastic waste sent for incineration and suspected increase in the export of waste plastics.As EEE remains in use for many years, plastics from WEEE are typically from older products containing a legacy of hazardous substances that are now restricted and cannot be recycled into new products.These include classes of chemicals containing bromine (e.g., PBBs, PBDEs, and HBCD), previously used as flame TA B L E 7 Potential for eco-design requirements to increase recycling of plastics from waste electrical and electronic equipment at each processing stage.

Mediumhigh
Respondents agreed it would stimulate demand for more plastics recycling.However, recyclers face significant issues in meeting quality and quantity needs for EEE currently.
Set a target for % of product that shall be recyclable

Lowmedium
Low Low More guidance from plastics recycling industry is needed as "recyclable" can differ.Current focus on "ability to disassemble" which currently benefits mainly manual WEEE processing, although may increase amounts of plastics available to recyclers.
a Not a measure included in Table 1, but highlighted by participant organizations as a potential eco-design solution.
retardants.EU Directive 2012/19 6 requires recyclers to separate plastics containing BFRs for selective treatment, which means these must be treated at a cost rather than recycled.
The EN 50625 7 standards set a maximum separation threshold of 2000 ppm bromine, those plastics under the threshold are determined as "BFR free" and recyclable.Generally, substance legislation sets the threshold of restricted chemicals in new products to <1000 ppm, but in some cases, this is undergoing review to stricter thresholds.All the respondents referred to a specific example of new EU proposals to lower the threshold of the BFR "DecaBDE" from 1000 to 10 ppm under EU POPS Regulations (EuRIC, 2018).The respondents were concerned they cannot provide firm guarantees that their recycled plastics would be able to comply with some of these new levels of substance bans (see Table 4, Q9).
Respondents explained that producing recycled plastics with such a low threshold is not technically or economically feasible until the substance is no longer present in the waste stream, as well as a concern that current screening methodologies and testing standards for bromine are not verified for <1000 ppm (see Table 4, Q10).

Plastic coatings
The potential impact of paints and coatings on plastic recycling was an issue for some but not all respondents.Some indicated that coatings can cause problems for separation by affecting the density of the plastic pieces or the performance of extruders (see Table 4, Q11, Q12).There was some consensus among respondents that small quantities of coatings tend to be chipped or washed away by mechanical processes such as shredding or grinding.Coatings may cause an issue for sorting and extruding processes if present in larger quantities, although none of the respondents raised this as a major concern.
Notably, one of the respondents suggested that coatings can be used to hide defects more common in recycled plastics and to match color specifications.Therefore, an unintended consequence of limits to coatings could be to reduce the demand for recycled plastics.

Availability of information
The aim of making product-specific information available to recyclers is to inform on features such as disassembly and hazardous substances.
However, all respondents agreed that they did not have the resource or capacity to look at manufacturer-specific information (see Table 4, Q13).
Exceptions included particularly large or unusual items such as an MRI scanner.Greater collaboration between industry and recyclers to track a higher-level overview of wider substance and polymer use trends in electronic products may be a more suitable approach than providing productspecific information.
Even E, the manual WEEE disassemblers, do not utilize this information.This is due to both a lack of specific product volumes and because they often use destructive techniques that are quicker than reverse-assembly approaches.It may be used if they had a specific agreement and sufficient volume from one producer.Due to the time lag between products placed on the market and appearing in the waste stream, A suggested that it is more efficient to distribute relevant information between recyclers than find product information.Therefore, making product-specific information available to recyclers appears not to be a particularly useful aid to increase recycling.

Plastic marking
None of the respondents, including the manual WEEE disassembler (E), used plastics markings for identification or sorting (see Table 4, Q14).Markings were not of use to the plastics recyclers as all used mechanical separation techniques, and plastics mostly arrived at their facilities as shredded flakes.One respondent was even suspicious of the accuracy of the markings.

Standardization
Some voluntary eco-design measures set limits regarding the number and type of polymers and polymer blends used in EEE to help facilitate increased recyclability.A substantial portion of WEEE plastics processed by the organizations studied (and indeed for WEEE overall in Europe) are not ultimately recycled; the respondents recycling plastics in-house gave estimates that between 40%−70% of their plastic material is directed to high-intensity incinerators.This is mainly due to its extreme complexity; numerous types of polymers and blends, additives, fillers, reinforcements, and hazardous substances affect the separation processes, particularly those which use density-based technology.These are simply uneconomical to recover.Standardization of polymers and polymer properties may, therefore, be a significant aid to recyclers (see Table 4, Q15).However, the extent to which each case study considered a plastic or polymer recyclable differed.Some recovered more polymers than others, or even certain filled polymers (see Table 4, Q16).
Another suggestion from some respondents was to ensure "un-recyclable" polymers are easily separated, designing these to be high density, and, therefore part of the waste fraction.However, there was no unanimous viewpoint across the respondents, as each had different capacities and tolerances for density separation techniques.Density is a physical property of the materials required, so it is not clear if designing plastics use for specific densities is possible.There is also the consideration of the overall resource efficiency of the system, and whilst increasing the density of an 'unrecyclable plastic' may improve recycling operations, it may have a negative impact for the environment by using additional resources.
Further research on the relationship between plastic density, chemical and physical design requirements, and separation densities required by different plastic recyclers would be needed to identify appropriate opportunities to improve recyclability through the standardization of plastics.

Mandatory recycled content
The aim of a mandatory minimum content of recycled material in EEE is to stimulate demand for recycled plastics.According to the respondents, recycled plastic polymers are typically used in basic applications, for which demand is relatively high, for example, flowerpots, garden furniture, and internal automotive parts.These products have less strict requirements for color, technical, and chemical properties, unlike those for EEE.
However, several wider issues highlighted in this study would hinder the effectiveness of this type of measure.First, respondents from B and C had concerns regarding the recycling capacity in EU to fulfil increased demand (see Table 4, Q17).This included the need for investment in more facilities and infrastructure, both for recycling and the high-intensity incineration facilities needed to dispose of plastics containing hazardous substances.Respondents noted that increasing WEEE collection across the EU and targeting the illegal export of WEEE and WEEE plastics is needed to increase the quantities of recycled material available.It seems that the WEEE Directive 8 requirements could play a more important role than eco-design measures in supporting increased use of recycled plastics in new products.
Second, the respondents raised concerns over the general quality of recycled plastics that may not currently be suitable for use in EEE (see Table 4, Q18).Recycled plastics cannot always match the same specifications as virgin plastic, for example, in price, color, physical, and technical properties.Respondent B highlighted that blending different batches of sorted polymer flakes was an important step to ensure consistent properties in the end product.In some cases, it may be necessary to blend with virgin plastic to ensure quality.In addition, respondents B, C, and D all claimed that by controlling more parts of the recycling supply chain or having direct partnerships with up-and downstream recycling operators, they could be more confident in the quality and quantity of input material.Another approach to quality control includes laboratory testing for composition upon arrival of material, following polymer separation processing and of the final product.Respondents B and C highlighted that where manufacturers can "relax" their plastics quality specifications, it can help solve this issue (see Table 4, Q19).
There were examples from B and C of collaborations with producers to take back products and recycle plastics to use in new EEE, for example, WiFi routers, vacuum cleaners, and coffee machines, but the same results are likely more difficult to achieve with the mass collection of mixed WEEE.
Overall, several factors outside the scope of eco-design measures will determine the feasibility of a mandatory recycled content for plastics in EEE.Whilst the measure aims to increase demand and stimulate a marketplace, there are significant technical and economic barriers to overcome before supply and quality can meet demand.

DISCUSSION AND CONCLUSION
Knowledge of recycling processes in practice is crucial for understanding how producers can best improve the recyclability of plastics used in EEE.
Importantly, this also allows for assessment of the effectiveness of regulatory eco-design measures.Empirical research of EoL processes, such as the case study method used here, can provide important insight and validation for developing eco-design approaches aiming to improve product material efficiency.
Overall, analysis of the case study interview responses indicates several important mismatches between the expectations and requirements set within eco-design measures and practices used within the recycling sector.
Overall, the most effective eco-design measures appear to be those that ensure the removability of plastics, particularly where manual disassembly is used.Materials such as wood and screws can be particularly problematic for plastics recycling, although responses on how large an impact these measures may have differed between recyclers.Additionally, our findings show that disassembly eco-design measures may have minimal effect for recyclers using automated processes.However, this should be considered in the light of existing research: ease of disassembly requirements may be beneficial where substantial volumes of specific types of product are manually recycled, such as TVs (as in the case of organization A).Such a requirement may then increase opportunities for "closed-loop" recycling: Wagner et al. (2019) found that recycled plastics from TVs could be directly reapplied in certain TV parts with suitable flammability and mechanical properties if separately disassembled and processed.
However, as processes differ between recyclers, the concerns expressed by respondents do appear to confirm that the assumed benefit of such measures may not be universal.
Conversely, the findings revealed a high level of uncertainty as to the benefit of several other eco-design measures intended to improve the recyclability of plastics from WEEE, including substance restrictions, limiting coatings on plastics, markings, and standardizing polymer use.
On substance restrictions, our results show recyclers' concerns on recycling WEEE plastics due to the presence of substances such as BFRs.
Several eco-design measures restrict all types of BFRs or, even more widely, all types of halogenated flame retardants (HFRs), to <1000 ppm, so this material may be unlikely be able to meet the specifications for using recycled plastics in new EEE products.There appears to be an apparent contradiction between the objectives of eco-design policy and recycling practices.This finding supports claims by Haarman et al. (2020) that the majority of BFRs currently present in the waste stream are in fact not regulated BFRs and so could be recycled.However, as density separation processes cannot discriminate between these BFR types, more plastics than necessary are incinerated.The study suggests that doubling the current separation threshold would increase recycling yield without increasing the concentration of regulated BFRs in the recycled material.
Recycled material must comply with regulations that implement important substance restrictions on environmental and health toxicity grounds.
However, the stated aim of eco-design measures limiting hazardous substances is to facilitate increased recycling.For example, HFRs are banned from use in TVs with the intention of "permitting higher yields of recycled plastics" (EU, 2019, p. 243).As not all BFRs/HFRs are regulated under substance legislation, recycled material may struggle to comply with a blanket ban eco-design requirement, thus limiting the use of recycled material in EEE products.Overall, it appears sensible for regulators to align restrictions with EU substance regulations; however, the role of further substance restrictions aiming to improve plastic recyclability should focus on substances that directly impede recycling processes.
Another consideration is the impact of using alternatives to restricted substances on recycling.Haarman et al. (2020) highlight that flame retardants based on phosphates (PFRs) can cause brittleness of recyclates if not effectively separated out.This can be more difficult with PFR-containing plastics, which are lighter in density than BFR plastics and thus closer in density to the target polymers for recycling.However, Peeters et al. (2013) found that it is possible to recycle plastics containing PFRs under certain conditions and for the recycled material to retain its flame-retardant properties.There is limited research in this area and developing recycling technology (Wagner & Schlummer 2020), so more investigation is required to better determine the impact of flame retardants on the recyclability of WEEE plastics before restricting substances on recyclability grounds.
Next, the extent to which plastic coatings were identified as an issue by the recyclers varied, as generally, large quantities are not seen within WEEE.Some eco-design approaches and measures specify the size or mass of plastic coating allowable for new products, however, the extent to which they may impact future WEEE composition and disrupt recycling processes or not is unclear.Further investigation of the benefit of restricting the size of the coated area and/or specifying density of coatings on recycling ability is needed before the impact of the use of plastic coatings on recycling can be fully understood.
Our findings on plastics markings reveal not much progress in eco-design thinking over the last 20 years.Respondent's concerns that marking plastics with polymer type and other information, such as FR inclusion, to assist with sorting, may only benefit recyclers who manually sort plastics from WEEE reflect concerns raised in previous research (Masanet et al, 2002;Dalhammar et al., 2014).Nevertheless, even though automated recycling processes represent the majority of WEEE plastics recycling in Europe, plastics marking is already widely implemented for electronic products.If other labeling or marking eco-design measures aiming to assist recycling are to be introduced, it is recommended to first assess how widely beneficial such a requirement would be.
As found in this study, the ability to recycle different types of plastics differs according to the different types of recycling processes.Therefore, measures to standardize plastic use in EEE are unlikely to have a significant benefit across all recyclers.In addition, different plastic polymers are useful precisely due to their differing properties and applications, so standardizing plastics for current recycling technology will severely limit product design options.It is likely to inhibit product differentiation, and product innovation, for example, where look, finish, and feel are specific to certain types of polymers.
Respondents also pointed out an issue further complicating matters: the use of coatings, additive chemicals content, and different polymer properties can be as important for the sale and use of recycled plastics as they are for plastics from virgin materials.This seems rarely considered in current eco-design literature (Berwald et al., 2021;Hultgren, 2012) and yet is important to understand how best to increase the use of recycled plastics in new products.
Further investigation is needed to reach a wider understanding of plastics recycling and address these uncertainties, including: • The level to which use of coatings may impede plastics recycling and whether there are any "threshold" levels of coating over which plastics recycling is disrupted.• Whether any level of standardization of specific plastics polymers and chemical additives substitution would lead to net increases in plastics recycling (and to create specific guidance on the extent to which plastic additives, fillers, and chemicals can be recycled).
Participants also discussed eco-design approaches they believed could help increase plastic recycling in future.First, they suggested that if any "un-recyclable polymers"' used in products could meet a specific density range, it may allow them to be more easily separated at EoL.Second, they suggested that using standardized markers/tracers in plastics could allow automatic separation at EoL.Although interesting, these approaches are largely speculative and would require substantial further investigation.The cost and feasibility of these approaches for production, the capability of recycling infrastructure to adapt to such changes, and their environmental impact are not well understood at present.Finally, respondents were more-or-less unanimous in their conviction that eco-design information, such as disassembly instructions or marking requirements, were of little practical use for their recycling operations.This seems to be a substantial mismatch between the intentions of government policy, undermining its effectiveness in practice.Overall, our results show that diverging practices between recyclers lead to conflicting expectations regarding what type of eco-design practices are best.Although recycling processes could be standardized to a degree to help resolve this issue, it does not follow that standardizing recycling is the best approach for an evolving and important environmental services sector.
Several limitations of the study presented here have been identified and could be addressed through future research.For example, although results are qualitative and limited to the specific cases studied, these cases were selected to represent the different types of recycling processes used within the EU.Future research could help with quantitative and/or statistical analysis of WEEE processing to investigate each of the issues and opportunities identified across a wider selection of recyclers and recycling processes.In addition, further research could expand the approach taken here and increase the number of interviews by including other relevant stakeholders, for instance, electronic design engineers and policy experts.
In particular, more research on how to improve the policy process for eco-design measures is needed, which could also investigate the opportunities and benefits of policymakers and industry to collaborate on particular products or at a sector level.
Without proper assessment and consideration of a product's environmental impact over its entire life cycle, unintended environmental consequences can be expected.In terms of implications for policymakers: consistent review of EoL treatment and recycling processes is needed to ensure eco-design measures and approaches are developed with consideration of current and expected future recycling scenarios.The methodology for the eco-design of energy-related products (MEErP) is the basis for setting product group specific eco-design regulations focused on energy efficiency and is under review to include better provision for material efficiency (Bundgaard et al., 2017).MEErP guidelines will need to include evaluation of how to resolve conflicting material efficiency goals (Holt & Barnes, 2010), for example, if proposals to increase recyclability contradict other material efficiency measures, such as ensuring product durability (Svensson & Dalhammer, 2018).In addition, these findings are likely to have implications for extended producer responsibility regulations, especially where fees are modulated according to a producer's adherence to eco-design criteria.As fee modulation to encourage product design for recyclability increases across the EU, so does the importance of further research on the effectiveness of eco-design measures for WEEE plastics.
Overall, this study has investigated many challenges and opportunities to improve the effectiveness of eco-design measures for EEE using a case study approach.Although eco-design is frequently advocated as a "one-size fits all" solution to improving material efficiency, our study demonstrates how eco-design measures aiming to improve EU plastics recycling, (i.e., information provision, marking, and substance restrictions) are likely to have a limited impact on improving plastics recyclability and may even inhibit or disrupt plastics recycling at EoL.Additionally, the results also highlight eco-design approaches that appear to be effective (i.e., disassemblability) and potential approaches that are, thus far, unexplored (i.e., the application of plastic coatings and standardization of plastic design).Despite more than 20 years of eco-design research, it appears that current EU policies and voluntary initiatives have been devised and implemented without adequate understanding of their impact on different types of recycling practices, thus likely impacting their long-term effectiveness.Empirical research, such as case studies used here, can provide valuable confirmation to ensure eco-design approaches are effective.
Abbreviation: X, required to comply with the regulation or voluntary measure.a Requirement for dismantling instructions as a form of compliance verification, rather than for provision to recyclers.
General overview of recycling plastics from waste electrical and electronic equipment (this study, supplemented with DEFRA, 2007; Makenji & Savage, 2012).

keyboards TA B L E 2
Industry Voluntary Agreement to improve the environmental performance of imagining equipment placed on the European market.Draft FY19 v.2.https://www.eurovaprint.eu/pages/voluntary-agreement/ Voluntary Industry Agreement to improve the energy consumption of Complex Set Top Boxes within the EU.Version 6.0.April 2, 2018.http://cstb.eu/index.php/documents/Commission Decision of March 12, 2009 establishing the revised ecological criteria for the award of the Community Eco-label to televisions (notified under document Nordic Ecolabelling of TV and Projector Version 5.8: June 20, 2013-June 30, 2022.https://www.svanen.se/en/how-to-apply/criteria-application/tv-and-projectors-071/xiii Nordic Swan Ecolabel (2013) Nordic Ecolabelling for Imaging Equipment Version 6.6: June 20, 2013-June 30, 2021.https://www.svanen.se/en/how-to-apply/criteria-application/imaging-equipment-015/The German Ecolabel Computers and Keyboards DE-UZ 78 Basic Award Criteria Edition January 2017 Version 3, https://www.blauer-engel.de/en/products/electric-devices/computers-and-Selectioncriteria for case studies of waste electrical and electronic equipment (WEEE) and plastics from WEEE recyclers.

Table 2 .
All organizations are located in Western and Central Europe.

Organization pseudonym Operates WEEE recycling processes Operates plastics from WEEE recycling processes Job title of main contact Region located Original input materials Main output materials Company description
TA B L E 3 Introduction to participant organizations.A single site IT asset recovery business that prepares EEE for re-use and manually dismantles WEEE for recycling.Input material arrives on site after pre-agreement with commercial clients.
Table 6 presents the general techniques used in the recycling industry to separate plastics into different polymer types.Using information available from the interviews, site visits, and secondary data, Figure 2 classifies and summarizes the different types of processes used to recycle plastics from WEEE across the three relevant organizations.
Usually, plastics from WEEE are received as mixed polymer flakes after WEEE re-processing and are mechanically sorted.The input material undergoes visual or laboratory inspection, washing to remove contaminants and further size reduction.To separate the mixture into single polymer (or polymer blend) output streams, organizations B, C, and D all used wet density-based separation technology in combination with other equipment such as, rubber separators, electrostatic-based and air-based separators.Spectral separation is generally not used due to the presence of black plastics in WEEE, which are incompatible with NIR So we stand there and take that apart quite manually, to remove the wood content before we chipped it in to small little bits and it becomes even worse to try and remove it from the plastic."If you've got a screw going through a bit of plastic, often that'll shear off, so you've still got the metal inside the bit of plastic.So, most of the metallic separation is not sensitive enough to get that out." Quote Organization Q1 "...unlike metals, plastics don't have one specific density.They have a peak at a certain density but the range of densities in PS and ABS is quite large, there's a big overlap."B Q2 "It's a very complex mixture; all kinds of technical plastics, nylons, polyamides, PMMA, polycarbonate, all kinds of blends of the polycarbonate."B Q3 "Is there ability to increase our density range to maybe get more yield at the same quality?That's something we periodically look at.If the feedstock changes in the next 10 years and there's less banned flame retardants, then again we might be able to increase our density range and recover more materials."D Q8 "A small piece of circuit board, a small piece of cable or aluminum it's all no problem, but massive metal pieces that's a problem."B Q9 "If that threshold comes in, it's very likely that they won't be able to achieve that from recycled polymer [...] At that point, the circularity of plastics in the waste stream right now would stop.It would have to be used for a fuel."A Q10 "The problem is analysis methodology we have has never been validated for this low concentration."B Q11 "Coatings give the sorting a 50% chance that the part is not recycled, so coatings reduce productivity and therefore supply chain security from recycling."C Q12 "[Paint] can cause a problem because when you're extruding it, it can gas off.Usually by the time it's gone through a shredder and tons of screens and things like that, the paint is more or less chipped away.But it can be an issue."D Q13 "No recycler has time and resources to read manufacturer information.All processes are standardized according the 10 WEEE clusters and the main goal is throughput."C Q14 "As we do not get much of any type, we simply send our plastics as mixed.On that basis the marking is not critical for us at the moment."E Q15 "Define certain standard plastics and produce them towards to that standard.Standardize the density, standardize the chemical properties, say which additives can be used, which additives are not allowed to use and then you've got something that can be recycled better because [...] that can be recycled with current processes."B Q16 "Different recyclers have different processes.What's fine for one is not fine for another.There's no standardization.It's so hard to say, 'yes it's recyclable' or 'no it's not'."D Q17 "Quantity and constant availability is a huge problem for post-industrial recycled polymers [...] We need more raw material supply to build bigger plants to satisfy the needs of our customers."