<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Ansink et al. (2022)</td><td>Ecological Economics</td><td>Bioplastics labels</td><td>On pack</td><td>Recycling behaviour</td><td>Field experiment and survey</td><td>Non-students</td><td>199 individuals</td><td>Netherlands</td><td>(1) The bioplastics logo displayed on a cup did not significantly affect the likelihood of recycling. (2) The bioplastics logo was noticed by only 35% of participants, and those who noticed it did not sort better than those who did not. (3) Over 90% of subjects incorrectly disposed of their cup as plastic waste. (4) Recycling behaviour for bioplastics was not affected by information, moral norms or environmental concern.</td><td>(1) Labels need to succeed in grabbing attention and inducing the intended behaviour; however, gaining attention is not enough to induce the correct behaviour. (2) Some basic knowledge - for WSLs, particularly knowledge on the relevant SWC schemes - appears necessary for them to have the desired effects. (3) In the case of new waste materials that require new WSLs, it should be taken into account that they may need some time to be perceived, be understood and become effective.</td></tr><tr><td>APCO and Planet Ark (2021)</td><td>Grey literature</td><td>Recycling labels</td><td>On pack</td><td>Awareness, valuation and perceptions of different recycling and disposal logos. Recycling intentions</td><td>Unclear</td><td>Unclear</td><td>Unclear</td><td>Australia, New Zealand</td><td>(1) Awareness of the ARL was relatively low compared with awareness of other logos, such as the Tidyman, the Mobius loop and the plastic identification code, but increased between 2018 and 2020. (2) Awareness of the ARL was somewhat higher among 16- to 44-year-olds than among 45- to > 65-year-olds. (3) Forty per cent of respondents said that they would recycle a little or a lot more if the ARL was on all packaging. (4) The ARL improved various recycling intentions for aluminium foil lids, soft plastic wraps and other materials (although it is not clear if these differences were statistically significant).</td><td>(1) It appears important to provide further information to help people understand a new WSL. (2) It requires time for WSLs to become known among the population and among different population segments. (3) Some population segments become aware of new labels earlier than others and might consequently benefit more from accompanying awareness campaigns.</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Buelow et al. (2010)</td><td>Management of Environmental Quality: An International Journal</td><td>Recycling and WSLs</td><td>On pack and on receptacle</td><td>Perceptions of helpfulness and understanding of labels</td><td>Mixed research (surveys and interviews)</td><td>Non-students</td><td>88 individuals</td><td>Australia</td><td>(1) Most respondents reported recycling packaging waste and sorting their waste carefully, but their understanding of recycling information on packaging labels was often poor. (2) Labels were considered neither overly helpful nor unhelpful in assisting with waste sorting. (3) Stickers on bins were found to be helpful but sometimes contained incorrect or confusing information. (4) The best-understood labels were action oriented and specific, while vague and contradicting labels were the least understood. (5) Respondents demonstrated confusion around various recycling symbols and their meanings. (6) Incorrect, misleading and vague labelling provided by manufacturers was a significant barrier to proper waste sorting.</td><td>(1) Effective WSLs must provide clear, straightforward and actionable information. (2) Usually, on-receptacle labels offer more space for communication than on-pack labels and can thus be important complements to on-pack labels. (3) The beneficial effects of WSLs might be limited and fall short of expectations (especially if they are not properly designed). (4) WSLs must be consistent with existing recycling (or other types of) labels.</td></tr><tr><td>Catlin et al. (2021)</td><td>Journal of Consumer Psychology</td><td>Recycling labels</td><td>On receptacle</td><td>Sorting accuracy</td><td>Study 1: field experiment<br>Study 2: field experiment<br>Study 3: online experiment</td><td>Study 1: students<br>Study 2: students<br>Study 3: Amazon Mechanical Turk</td><td>Study 1: 259 recycling decisions<br>Study 2: 122 recycling decisions<br>Study 3: 399 individuals</td><td>United States</td><td>(1) Pro-environmental receptacle labelling can lead to overinclusive recycling (defined as the proportion of decisions to recycle non-recyclable items). (2) Both approaches (including the message 'Recycle more, save the Earth' on the label) and avoidance (including the message 'Landfill' on the label) increased overinclusive recycling. (3) There was no evidence that pro-environmental labelling increased the likelihood of recycling recyclable items.</td><td>Pro-environmental/persuasive labels can have detrimental effects or at least may not have positive effects on recycling behaviour. WSLs should thus use these types of messages only after careful testing.</td></tr><tr><td>Gutierrez et al. (2021)</td><td>Convergence of Ergonomics and Design (book)</td><td>WSLs and receptacle design (body)</td><td>On receptacle</td><td>Preferences and ability to identify the correct waste bin</td><td>Quality function deployment approach, focus group discussions and</td><td>Students and university staff</td><td>Study 1: n/a<br>Study 2: 8</td><td>Philippines</td><td>(1) Difficulties in using the bin, a lack of knowledge regarding SWC, inconvenience (a large number of items depicted on labels) and confusion (as a result of images on labels not accurately representing</td><td>(1) WSLs should not show too many different items. (2) The items referred to on WSLs should be unambiguously inferable from the icons and pictograms used. (3) WSLs should strive to provide</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td></td><td></td><td>shape, opening shape and position, lid type, labels/signage design and position, category organisation and colour)</td><td></td><td></td><td>user needs survey</td><td></td><td>individuals<br/>Study 3: 81 individuals</td><td></td><td>what items look like) were the main reasons for waste-sorting difficulties. (2) Removing lids, using informative labels, reducing the number of labels on the top of the bins and using images on labels that correspond to actual items lowered the amount of inaccurately separated waste, from 62.29% to 14.29%.</td><td>sufficient information on the SWC scheme they refer to, to make them self-contained, or be accompanied by complementary information campaigns.</td></tr><tr><td>Langley et al. (2021)</td><td>Sustainability</td><td>Labels aimed at reducing food waste (date and storage information) and packaging design (visual and functional arrangements of elements)</td><td>On pack</td><td>Consumer perceptions of food packaging and food waste, and how these perceptions might be influenced by packaging design and information</td><td>Study 1: journey mapping<br/>Study 2: interviews</td><td>Non-students</td><td>Study 1: 37 individuals<br/>Study 2: 50 individuals</td><td>Australia</td><td>(1) Consumers did not feel empowered to reduce food waste or food packaging waste. (2) Food packaging or reducing food waste was rarely a primary motivation in food purchasing decisions. (3) Reducing packaging, including plastic packaging, was seen by participants as more important than reducing food waste. (4) Consumers can be encouraged to save food with appropriate prompts and with packaging designed to limit the cognitive, conative and affective burden placed on them. (5) Packaging design needs to be developed collaboratively with industry to balance commercial and consumer considerations. (6) On-pack information should not add to the information clutter on packaging.</td><td>(1) Situating WSLs close to information that people seek when looking at product packaging can increase their salience and impact. (2) The design of WSLs needs to consider if their objective conflicts with other objectives, especially those indicated by other labels on packaging and those that consumers have. (3) WSLs should make people feel empowered to sort their waste correctly. (4) Involving central stakeholders in the design of WSLs might be beneficial. (5) On-pack information should be easy to find in relevant places on packaging but should not add to information clutter on packaging. (6) WSLs should be perceived as increasing the convenience of sorting waste. (7) WSLs should consider the cognitive, conative and affective</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td></td><td></td><td>ts, materials, graphics and information)</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td>burdens that consumers face during waste sorting.</td></tr><tr><td>Latkin et al. (2022)</td><td>Sustainability</td><td>Recycling labels</td><td>On pack</td><td>Understanding of 'chasing arrows' symbol</td><td>Survey</td><td>Non-students</td><td>808 individuals</td><td>United States</td><td>(1) The majority (81.3%) of respondents misunderstood the 'chasing arrows' symbol as an indication that the item could definitely be recycled, while 16.3% reported that it indicated that the item could probably be recycled. This suggests that a large proportion of individuals do not correctly understand the 'chasing arrows' symbol on plastics. (2) Most respondents did not know the meaning of the numbers included in the middle of the symbol, and almost one third gave an incorrect response.</td><td>(1) WSLs should not contradict other, potentially conflicting and potentially misunderstood, recycling labels or, at the very least, there should be an acknowledgement that the misunderstanding of related labels might affect the extent to which WSLs are understood and acted upon. (2) Additional information to help in understanding WSLs could be communicated via QR codes or other digital means.</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Luo et al. (2022)</td><td>Environment and Behavior</td><td>WSLs</td><td>On receptacle</td><td>Sorting accuracy</td><td>Study 1: field experiment<br>Study 2: field experiment</td><td>Non-students</td><td>Study 1: unclear but potentially like study 2<br>Study 2: between 915 and 4925 items disposed of, depending on the week during which the study was conducted</td><td>Canada</td><td>(1) Signage showing a marine animal trapped in plastic debris resulted in the largest reduction in plastic waste (17%), compared with improved recycling signage alone, signage with a pledge to reduce plastic waste and the control condition. (2) Seeing the animal image in the kitchen area several times may have resulted in consumers retaining a mental image that triggered a reconsideration when they attempted to use a plastic item. (3) The fact that plastic waste was reduced across all bins suggests that the signage with the animal minimised the plastic items entering the waste streams, rather than diverting plastic items from one bin to another. (4) The signage with the animal was more effective in reducing plastic waste than commitment making or improving information about the appropriate disposal behaviour alone. (5) The reduction was solely due to the image of the marine animal, rather than a combined effect of the text and the image on the signage. (6) Very few employees reported that they had noticed the posters, signed the pledge or changed their waste disposal behaviour over the course of the studies. (7) The visual image of a marine animal trapped in plastic debris may not require conscious awareness to elicit behavioural change.</td><td>(1) Emotionally engaging visuals can motivate correct plastic waste sorting (as plastic waste is responsible for animal suffering) and could thus be beneficial as part of WSLs. (2) Such visuals can be effective without having to include text on WSLs. (3) Such visuals on WSLs most likely work subconsciously.</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Nemat et al. (2020)</td><td>Sustainability</td><td>Food packaging design (form, shape, material, colour and size) and on-pack labels in general, with specific focus on recycling logos as part of packaging design</td><td>On pack</td><td>Perceptions of graphical elements on packaging (logos, symbols, images and text) and their usefulness in enhancing recycling knowledge and motivating sorting; the process of separating food packaging waste; and packaging types and attributes that gave the largest impression of quality/value</td><td>Interviews</td><td>Non-students</td><td>15 families including 37 individuals</td><td>Sweden</td><td>(1) Recycling behaviour was influenced by packaging attributes such as perceived quality, value and recyclability. (2) Some graphical elements were not clear, were confusing or were inconvenient, making the participants uncertain on how to separate and sort the packaging. (3) There were packaging types and attributes that contributed to perceptions of quality/value and that benefited consumer sorting (e.g. dotted or perforated lines to indicate where the packaging should be folded or providing declarative and oriented information about waste sorting aligned with consumer needs). (4) Most participants saw no benefit in using different colours for the main body of packaging. Vivid colours were seen as good reminders to sort. (5) Inconsistent placement of information and small size were considered the main barriers to usefulness.</td><td>(1) The placement of graphical elements on packaging can be crucial in affecting whether they are noticed or ignored. Placement should be consistent and the size of WSLs should be appropriate to make sure they are being noticed and incorporated in waste-sorting-related decisions. (2) There are several potential elements of bad label design: small size, poor positioning and inconsistent use across different products of the same company or across the same products by different companies. (3) Combining graphical and textual elements is important. (4) Vivid colours could function as sorting reminders (making WSLs salient).</td></tr><tr><td>Rousta et al. (2015)</td><td>Waste Management</td><td>WSLs</td><td>On receptacle</td><td>Sorting accuracy</td><td>Field experiment</td><td>Non-students</td><td>28 bins</td><td>Sweden</td><td>New on-bin stickers reduced the number of incorrectly sorted nappies considerably, but did not have as big an effect on food waste.</td><td>WSLs should provide visible and easily understood information at the time of disposal and should be consistent with the relevant SWC scheme.</td></tr></tbody></table>
<table><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Label location</td><td>Main outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Shearer et al. (2017)</td><td>Waste Management</td><td>'No food waste please' stickers</td><td>On receptacle</td><td>Amount of separately collected food waste</td><td>Field experiment</td><td>Non-students</td><td>64 284 households</td><td>United Kingdom</td><td>(1) The use of visual prompts in the form of stickers on food waste bins significantly increased the amount of food waste recycled by households. (2) The effect was sustained over time, with the treatment group continuing to recycle more food waste than the control group in the short medium and long terms. (3) The stickers were cost-effective, with a cost of GBP 0.35 per household. (4) There were multiple potential explanations of the observed effects, such as the semi-permanent nature of the stickers, increased visibility and the potential change in social norms for food waste recycling.</td><td>(1) WSLs can function as simple reminders of desired actions (recycling food waste) while highlighting what should not be commingled in a general waste bin ('No food waste please') and what instead should be done (i.e. '... use your food recycling caddy'). (2) WSLs as stickers can be particularly cost-effective (but naturally are not always feasible).</td></tr><tr><td>Verdonk et al. (2017)</td><td>Sustainability</td><td>WSLs</td><td>On receptacle</td><td>Sorting accuracy</td><td>Field experiment</td><td>Non-students</td><td>889 disposals</td><td>Australia</td><td>(1) Motivational pro-environmental signs attracted participants' attention, and more items were deposited in the bins featuring new signage. (2) The motivational pro-environmental signs did not improve sorting accuracy.</td><td>(1) As the motivational signs may have been ineffective because they were too cluttered, potentially leading to information overload, WSLs should be designed with this limitation in mind. (2) Motivational messages and WSLs should avoid being cluttered, and the pictures indicating the correct waste stream should be clear and legible. (3) The effectiveness of pro-environmental prompts on WSLs may be limited.</td></tr><tr><td>Wojciecho wska and Wiszumirska (2022)</td><td>Sustainability</td><td>Ecolabels</td><td>On pack</td><td>Attitudes towards recycling, experiences and attitudes regarding SWC, practical information about SWC and the level of awareness of</td><td>Survey</td><td>Non-students</td><td>1 029 individuals</td><td>Poland</td><td>(1) The study identified three clusters of consumers based on their attitudes towards recycling: pro-recycling, indifferent and anti-recycling. (2) Consumers' level of knowledge about SWC in Poland is generally low, and there is a need for more practical information about SWC. (3) Consumers considered the information-related function of packaging to be important for waste sorting. (4) There is a need for</td><td>(1) Interactive solutions, including QR codes, can provide additional and updated information that does not fit on the physical labels themselves. (2) Correct waste sorting can also be challenging for people with pro-environmental attitudes, making it important that WSLs speak to and are understood by different types of consumers</td></tr></tbody></table>
<table><thead><tr><th>Reference</th><th>Journal</th><th>Focus</th><th>Label location</th><th>Main outcome variable</th><th>Methodology</th><th>Sample type</th><th>Sample size</th><th>Geographical focus</th><th>Main findings</th><th>Main insights for WSLs</th></tr></thead><tbody><tr><td></td><td></td><td></td><td></td><td>respondents regarding SWC</td><td></td><td></td><td></td><td></td><td>innovative packaging solutions that are both sustainable and functional.</td><td>and for consumers with a limited understanding of SWC.</td></tr><tr><td>Wu et al. (2018)</td><td>Journal of Environmental Psychology</td><td>WSLs</td><td>On receptacle</td><td>Sorting efficiency (time to sort divided by sorting accuracy)</td><td>Motion tracking experiment</td><td>Students</td><td>Study 1: 43 individuals<br>Study 2: 20 individuals<br>Study 3: 26 individuals</td><td>Canada</td><td>(1) Signs conveying information using images or icons were better than signs conveying information using only words (at least when the images and icons were familiar to users). (2) Displaying prohibited items along with permitted items did not yield a net benefit compared with signs that displayed only permitted items. (3) Consistent positioning of the four waste categories enhanced sorting performance.</td><td>(1) WSLs should consider the use of images and icons and make sure that the images and icons used are familiar to users. (2) Presenting both permitted and prohibited items on WSLs can interfere with performance when the signs are icons and should thus be critically assessed before being featured on WSLs. (3) WSLs should be placed consistently across waste categories.</td></tr><tr><td>WWF Detuschla nd (2021)</td><td>Grey literature</td><td>Unclearr</td><td>On pack</td><td>n/a</td><td>n/a</td><td>n/a</td><td>n/a</td><td>Germany</td><td>n/a</td><td>(1) All labels should be easily removable, with minimal direct printing on the container. (2) Only transparent, uncoloured containers should be used. (3) The additives, barriers, coatings, adhesives and ink used should not be problematic for recycling. (4) Closure material choices should not create a problem for recycling (e.g. silicone seals and valves, polystyrene, polyvinyl chloride, aluminium and steel caps should be phased out).</td></tr></tbody></table>

NB: n/a, not applicable.

Source: Authors' own creation.
<table><caption>Table A2. Relevant references focusing on packaging and receptacle design</caption><thead><tr><td>Reference</td><td>Journal</td><td>Focus</td><td>Specific focus</td><td>Outcome variable</td><td>Methodology</td><td>Sample type</td><td>Sample size</td><td>Geographical focus</td><td>Main findings</td><td>Main insights for WSLs</td></tr></thead><tbody><tr><td>Borgman et al. (2018)</td><td>Grey literature (student thesis)</td><td>Packaging design (including labels)</td><td>Graphical label design, certification on information and bottle form</td><td>Preferences, and purchasing and recycling intentions</td><td>Study 1: online ranking survey<br>Study 2: conjoint analysis<br>Study 3: field experiment</td><td>Study 1: unclear<br>Study 2: unclear<br>Study 3: non-students</td><td>Study 1: n/a<br>Study 2: 73 individuals<br>Study 3: 200 individuals (200 cups; 96 opinions)</td><td>Unclear</td><td>(1) Graphics played a larger role than information and form in consumer decisions. (2) Sustainability information was appreciated by consumers. (3) Graphical congruency with the product was important. (4) The willingness to pay for an extra sustainability label was low. (5) It was unclear if recycling labels and text could affect the recycling intentions of consumers.</td><td>(1) Graphical elements should be used by WSLs to provide information. (2) WSL design should consider that consumers might have only weak preferences for additional labels.</td></tr><tr><td>Jiang et al. (2021)</td><td>Waste Management</td><td>Receptacle design</td><td>Colour preferences, slot shape preferences and slot position preferences, as well as the impact of past perceptions on these preferences</td><td>Study 1: colour preferences<br>Study 2: slot shape preferences for PET bottle bins<br>Study 3: slot shape preferences for other bins<br>Study 4: slot position preferences<br>Study 5: sorting accuracy</td><td>Studies 1-4: surveys<br>Study 5: field experiment</td><td>Studies 1-4: non-students<br>Study 5: mostly students</td><td>Study 1: 730 individuals<br>Study 2: 730 individuals<br>Study 3: 210 individuals<br>Study 4: 3090 individuals<br>Study 5: 240 recycling bins used in public spaces</td><td>Japan</td><td>(1) Common perceptions of colours used in certain design items of recycling bins affected colour preference. (2) Common perceptions of certain insertion slot design items affected slot design preference. (3) The colours that were popular depended on the design items and waste types.</td><td>(1) Colours for WSLs should be carefully selected. (2) Previous encounters of consumers with colours and their associations with certain waste materials should be considered.</td></tr></tbody></table>
<table><tr><td>Keramitso glou and Tsagaraki s (2018)</td><td>Sustainability</td><td>Receptacle design</td><td>Shape, colour and type of lid and insertion slot</td><td>Preferences for bin designs</td><td>Study 1: exploratory survey<br/>Study 2: validation survey</td><td>Non-students</td><td>Study 1: 757 individuals<br/>Study 2: 430 individuals</td><td>Greece</td><td>(1) The following design elements were identified as preferred for recycling bins: easy handling, being free of risks to human health and safety, the protection of recyclables and attractivity. (2) Preferences did not always coincide with the top-down decision-making in relation to recycling bin design. (3) Respondents connected the colour of recycling items with the recycling bin colour. (4) Public participation in the designing of recycling facilities could increase willingness to recycle.</td><td>(1) Public participation in the design of WSLs could be beneficial. (2) Colours of WSLs should take into account people's colour preferences with respect to the associated materials.</td></tr><tr><td>Lane and Wagner (2013)</td><td>Resources, Conservation and Recycling</td><td>Receptacle design</td><td>Size, type and colour</td><td>Study 1: multiple<br/>Study 2: programme design of waste collection systems</td><td>Study 1: literature review<br/>Study 2: survey</td><td>Study 1: n/a<br/>Study 2: non-students (waste professionals)</td><td>Study 1: n/a<br/>Study 2: 785 individuals</td><td>Study 1: n/a<br/>Study 2: United States</td><td>(1) There was no single 'best' recycling container (i.e. no best size, colour or type) that was unambiguously statistically shown to perform best. (2) Confounding contextual variables (sociopolitical variables and those related to infrastructure) made identification of an optimal receptacle difficult. (3) Costs (purchase costs, assembly needs, durability, maintenance, adaptability to new technology, impacts on worker safety, collection limitations/needs and additional technology needs) are important factors to consider. (4) Recycling programmes should be targeted to dwelling type (single- versus multiple-family households). (5) 'Purposeful incrementalism informed by pilot studies' is a good approach. It should set distinct and ordered goals (e.g. increasing participation rates or diversion rates).</td><td>(1) Contextual factors influence the 'best' design of WSLs. (2) Costs of WSLs and their implementation need to be considered. (3) Optimal WSLs should be based on pilot studies, if possible.</td></tr></table>
<table><tr><td>Langley et al. (2011)</td><td>Packagin g Technolo gy and Science</td><td>Packag ing design</td><td>Materials , geometry , content and informati on</td><td>Consumer treatment specific examples of packaging end of life of at</td><td>Study 1: bin raids<br/>Study 2: digital diaries<br/>Study 3: visual questionnaire<br/>Study 4: video ethnography</td><td>Unclear</td><td>Study 1: 10 househol ds<br/>Study 2: 5 househol ds<br/>Study 3: > 200 response s<br/>Study 4: 2 househol ds</td><td>United Kingdom</td><td>(1) Some of the findings suggest that households generally do not incorporate on-pack information in their waste disposal decisions, that confusion regarding recycling symbols exists and that prior knowledge regarding waste sorting is more influential than on-pack information. (2) Recycling may be hindered if the materials are perceived as dirty and disgusting (especially related to the packaging of meat products).</td><td>WSLs will have to compete with prior and potentially conflicting consumer knowledge on how to sort waste correctly and with perceptions of waste as being disgusting and dirty. This suggests that complementary information campaigns might be important to create an adequate knowledge foundation into which WSLs are embedded.</td></tr><tr><td>Leeabai et al. (2021)</td><td>Waste Manage ment</td><td>Recept acle design</td><td>Colour, shape, lids and aperture slots of general waste bins</td><td>Study 1: colour preferences for general waste bins<br/>Study 2: noticeability of general waste bins<br/>Study 3: correct sorting</td><td>Study 1: survey<br/>Study 2: survey<br/>Study 3: field experiment</td><td>Universit y students and staff</td><td>Study 1: 442 individual s<br/>Study 2: 296 individual s<br/>Study 3: capture rates of three general waste bins</td><td>Thailand</td><td>(1) Participants were more likely to sort waste correctly when using general waste bins with preferred colours. (2) Bins with less noticeable colour combinations tended to require more effort to be found. Therefore, they were more likely to be found by people with high motivation to sort, leading to high effective capture rates. (3) The least preferred colour combination had the highest waste separation efficiencies. (4) Location, colour and noticeability of general waste bins affected waste collection and sorting performance.</td><td>(1) Increased efforts to grab attention through appropriate bin design and configuration (including WSLs) could lead to more efficient SWC. (2) WSLs with less-preferred colours might not necessarily perform worse.</td></tr><tr><td>Lin et al. (2016)</td><td>Sustaina bility</td><td>Recept acle design</td><td>Colours and symbols</td><td>Capture rates of sorted (recycled) materials</td><td>Field experiment</td><td>Non-students</td><td>13 buildings</td><td>China</td><td>Yellow bins with sunflowers resulted in lower contamination rates and good capture rates of the food waste targeted.</td><td>Induction of positive emotional states using visual prompts might explain the results and could also extend to WSLs.</td></tr></table>
<table><tr><td>Montazeri, et al. (2012)</td><td>DESIGN 2012 – 12th International Design Conference</td><td>Receptacle design</td><td>Colour</td><td>Study 1: recall of recycling bin<br>Study 2: waste disposal</td><td>Study 1: survey<br>Study 2: lab experiment</td><td>Students</td><td>Study 1: 99 individual s<br>Study 2: 48 individual s</td><td>United States</td><td>(1) Colour can affect the salience of an object and trigger the associated desired behaviour. (2) Out of grey, red, blue and green, green was the most remembered colour, while grey was the least remembered. (3) Participants recycled more in green than in grey bins.</td><td>(1) Colours are important components of WSLs, and certain colours may be better remembered and associated with certain concepts than others. (2) The colour green in particular may be associated with concepts such as recycling and pro-environmental behaviour more generally. Thus, it should be used consciously on WSLs.</td></tr></table>
<table><tr><td>Mozo-Reyes et al. (2016)</td><td>Resource s, Conservation and Recycling</td><td>Recept acle design</td><td>Special recycling bin features, including the ability to count recyclables, the salience of recycling and the embedding of recycling in social contexts to provide feedback</td><td>Study 1: number/weight of recycled items, number of unique recyclers, number of visits and user behaviour<br>Study 2: mass/number of recycled items<br>Study 3: number of users, interaction with bin, distance to bin, body position (including facial expressions), involvement of others, time of interaction, number of visits, number of recycled items per user, and total number and mass of recycled items</td><td>Study 1: 2-day field experiment<br>Study 2: 1-week field experiment<br>Study 3: 1-month field experiment</td><td>Students and university staff</td><td>n/a</td><td>United States</td><td>Study 1: the numbers of visits and recycled items were higher in the WeREcycle bin than in the baseline bin.<br>Study 2: recycling was diverted from other bins to the new bin, and recycling rates in the new bin were higher overall.<br>Study 3: the new bin had medium attendance (compared with the baseline and a 'non-technological' intervention), had the highest number of recycled items and had the lowest amount of contamination. Average recycled items per attendance per day was highest for the new bin. Overall, the new bin garnered a lot of interest.</td><td>(1) Feedback can facilitate appropriate interaction with new technologies, including potentially also WSLs. (2) Technology has the potential to make recycling more attractive and entertaining.</td></tr></table>
<table><tr><td>Nemat et al. (2019)</td><td>Sustainability</td><td>Packaging design</td><td>Visual attributes that include structural features such as material, shape, size, weight, texture and graphical /iconic features such as colour combination, image and text layout, logo, and label, as well as verbal attributes that consist of lengthier textual explanations</td><td>Consumer sorting and preferences</td><td>Literature review</td><td>n/a</td><td>42 publications</td><td>n/a</td><td>(1) The review highlights the importance of packaging design and attributes in motivating or hindering consumers to sort packaging waste correctly. (2) The ability of packaging to communicate a message, primarily through its visual attributes, was considered an important factor to stimulate sorting behaviour. (3) The recyclability of packaging should be considered an inherent value of packaging, similar to attributes such as beauty and durability.</td><td>(1) Packaging can function as a natural vehicle for WSLs to communicate sorting instructions to consumers. (2) WSLs should strive to contribute to the perceived value of packaging.</td></tr><tr><td>Nemat et al. (2022)</td><td>Resources, Conservation and Recycling</td><td>Plastic food packaging, including visual communication attributes</td><td>Packaging form, size, durability, haptic aspects, visual communication properties and</td><td>n/a</td><td>Photo-based observation study and semi-structured interviews</td><td>Consumers, students and researchers</td><td>18 individuals</td><td>Sweden</td><td>(1) Participants reported difficulties in sorting small pieces of (torn/ripped) packaging waste, which can lead to missorting. (2) Participants were not aware of on-pack recycling information, logos or symbols on packaging and did not search for such information on the internet. (3) Consumers missorted plastic packaging waste due to perceived inconvenience, such as perceived separation difficulty or lack of space,</td><td>(1) There are challenges related to labels on mixed materials that WSLs need to consider. (2) Packaging design aspects, such as the perceived value of labels, are important for WSLs to be effective. (3) If possible, WSLs should provide users with a sense of convenience of waste sorting. (4) WSLs should be designed considering the reality of ripped and torn packaging, which may disrupt label functionality and</td></tr></table>
<table><tr><td></td><td></td><td>es (labels)</td><td>perceived value</td><td></td><td></td><td></td><td></td><td>including laziness. (4) Low perceived packaging value can deter consumers from undertaking proper disposal. (5) Packaging design can play a role in promoting proper waste separation by providing clear and visible recycling information and symbols.</td><td>affect the perceived value of packaging. (5) WSLs should contribute to the perceived value of packaging.</td></tr><tr><td rowspan="2">Schloss et al. (2018)</td><td rowspan="2">Cognitive Research: Principles and Implications</td><td rowspan="2">Receptacle design</td><td rowspan="2">Colour-object associations in the context of recycling</td><td rowspan="2">Response times and colour-object associations</td><td>Study 1: lab experiment</td><td rowspan="2">Unclear</td><td rowspan="2">Study 1: 24 participants</td><td rowspan="2">United States</td><td rowspan="2">(1) People perform an assignment colour inference process when they interpret colour-coding systems. (2) Evidence supported the global assignment hypothesis (which predicts that people not only consider association strength between object and colour, but also account for association strengths between all other objects and colours within the scope of the system). This can result in weak associations between colours and objects that result in overall stronger pairings. (3) Participants were more likely to discard waste in the correct bin when the bin's colour was strongly associated with the waste type. (4) Participants had difficulty discarding waste in bins that had weakly associated colours, even if the colour was the best available choice. (5) Overall, the results suggest that a colour-coding system that maximises the association strength between assigned colour-object pairings and minimises the association strength between non-assigned colour-object pairings could improve the ease of interpreting and understanding of waste-sorting systems, leading to better sorting.</td><td rowspan="2">Colours used on WSLs should consider the colour-object associations that people might already have.</td></tr><tr><td>Study 2: lab experiment</td><td>Study 2: 96 individuals</td></tr></table>
<table><tr><td>Trudel and Argo (2013)</td><td>Journal of Consumer Research</td><td>Packaging design</td><td>Size and distortion of waste</td><td>Studies 1–5: recycling behaviour<br>Study 6: perceptions of waste</td><td>Study 1: field observation (exploratory)<br>Studies 2–6: lab experiment</td><td>Study 1: non-students and university staff<br>Studies 2–6: students</td><td>Study 1: 22 faculty assistant offices<br>Study 2: 150 individuals<br>Study 3: 183 individuals<br>Study 4: 75 individuals<br>Study 5: 130 individuals<br>Study 6: 68 individuals</td><td>United States</td><td>Study 1: paper was more likely to be recycled when the pieces were large than when they were small.<br>Study 2: distorted paper was less often recycled than non-distorted paper.<br>Study 3: larger pieces of paper were more likely to be recycled than smaller pieces of paper, while distorted paper was less likely to be recycled than maintained paper.<br>Study 4: participants were more likely to recycle after listing uses for the paper, suggesting that usefulness underlies the impact of distortion on recycling.<br>Study 5: large cans were recycled more than small cans, and cans with a maintained form were recycled more than distorted cans.<br>Study 6: distorted cans were perceived as less clean and useful. Distorted cans were more likely to be intended for rubbish than maintained cans.</td><td>Distortion of packaging waste affects its disposal and most likely also the effectiveness of a complementary WSL.</td></tr></table>
<table><tr><td>Wever et al. (2010)</td><td>Packagin g Technolo gy and Science</td><td>Packag ing design</td><td>Branding, reclosabil ity and ability to play with packagin g</td><td>Littering</td><td>Study 1: field experiment<br/>Study 2: field experiment<br/>Study 3: field experiment<br/>Study 4: field experiment<br/>Study 5: field experiment</td><td>Study 1: mostly students<br/>Study 2: non- students<br/>Study 3: mostly students<br/>Study 4: mostly students<br/>Study 5: students</td><td>Study 1: around 4 000 individual s (5 000 cups)<br/>Study 2: 898 cups<br/>Study 3: 430 PET bottles + 394 CartoCan s<br/>Study 4: 1 857 sampled candies<br/>Study 5: n/a</td><td>Netherlands</td><td>(1) Conspicuous anti-littering labels may reduce littering, but more research is necessary to determine the optimal level of conspicuousness. (2) Peel-off closures were sensitive to littering, while screw-on caps induced users to reclose after use, but did not reduce littering. (3) Designing packaging to capture attention may affect littering, but depends on the availability of disposal options in surroundings. (4) Premium-brand packaging may be treated differently from unbranded product packaging.</td><td>(1) WSLs should be noticeable, salient and conspicuous. (2) The effects of WSLs are limited by the available waste disposal infrastructure.</td></tr></table>

NB: n/a, not applicable.

Source: Authors' own creation.
<figure><img src="image_45.png" /><figcaption>Figure A1. Categorisation of packaging according to components, materials and their separability</figcaption></figure>

NB: Single-component packaging with multiple separable materials is theoretically possible. However, it might be the case that, in such cases, a separable material might be interpreted as a separate component, simply because it is of a different material. This reflects the sometimes fuzzy definition of components.

Source: Authors' own creation.
<table><caption>Table A3. List of lessons and insights from the main sections of the report</caption><thead><tr><td>Section</td><td>Lessons and insights</td></tr></thead><tbody><tr><td>5.1.1</td><td>Although people recycle and sort waste without WSLs or recycling labels, such labels can aid in related efforts.</td></tr><tr><td>5.1.1</td><td>How labels are perceived and valued influences their acceptability and effectiveness and thus, we argue, their political feasibility.</td></tr><tr><td>5.1.1</td><td>Perceptions of labels depend on factors such as their design, as well as aspects of the packaging and materials they refer to.</td></tr><tr><td>5.1.1</td><td>The relation between labels and the materials they refer to is important. Consistent application of labels on different packaging waste materials is key to a clear relation between labels and materials.</td></tr><tr><td>5.1.1</td><td>WSLs should be easy to find and of sufficient size, but should not add to the information clutter on packaging.</td></tr><tr><td>5.1.1</td><td>The evidence reviewed is far from sufficient to generalise to the various existing WSLs or recycling labels in the EU. Nevertheless, design aspects of existing labels, specifically their clarity, size, positioning, readability and noticeability, appear to be important aspects of harmonised WSLs. Advanced digital solutions (e.g. QR codes) might also be relevant.</td></tr><tr><td>5.1.1</td><td>As different types of consumers can perceive and respond to labels differently, a nuanced understanding of consumer segments can be insightful.</td></tr><tr><td>5.1.1</td><td>Even environmentally motivated people can profit from WSLs.</td></tr><tr><td>5.1.1</td><td>Testing WSLs extensively is crucial.</td></tr><tr><td>5.1.2</td><td>Labels must be understood to work as intended.</td></tr><tr><td>5.1.2</td><td>Labels need to be understandable when positioned next to labels sending different or conflicting messages.</td></tr><tr><td>5.1.2</td><td>Elements of bad label design include small size, unclear and vague messages, inconsistent use and poor positioning.</td></tr><tr><td>5.1.2</td><td>Information on the necessity of and instructions for cleaning and segregating packaging materials and components can be relevant, although the space available on labels might be too limited.</td></tr><tr><td>5.1.2</td><td>Proper understanding of labels requires time. New labels, even if well designed, might not be judged as clear and understandable at the beginning.</td></tr><tr><td>5.1.2</td><td>Visual elements should be carefully chosen to reflect the intended message or function and possibly combine graphical and textual elements to provide meaningful and unambiguous information.</td></tr><tr><td>5.1.2</td><td>Action-oriented labels with clear instructions for consumers can improve their efficacy and clarity.</td></tr><tr><td>5.1.2</td><td>Ambiguous prompts such as 'Do the right thing' or 'Please dispose of this package thoughtfully' do not provide precise enough information to guide individuals in correctly sorting waste and should be avoided.</td></tr><tr><td>5.1.2</td><td>WSLs might benefit from being easily removable and applicable, with minimal direct printing on the container, and furthermore from being free of additives, barriers, coatings, adhesives or ink that might create problems for recycling.</td></tr><tr><td>5.1.3</td><td>WSLs that are perceived positively and understood well are not automatically effective. Effectiveness should always be verified empirically or experimentally.</td></tr><tr><td>5.1.3</td><td>WSLs must be clear, salient and actionable.</td></tr><tr><td>5.1.3</td><td>Being aware of label components that are self-explanatory and those that rely on external information is crucial. Digital solutions may serve to provide additional information without requiring additional space.</td></tr><tr><td>5.1.3</td><td>An important case for WSLs is multi-material and multicomponent packaging. These types of packaging can be more difficult to handle and sort for consumers than single-material and - component packaging, most likely because they require more cognitive and practical effort to be properly prepared and sorted. While this makes a case for simple packaging, it also suggests</td></tr></tbody></table>
<table><tr><td></td><td>that WSLs should be as clear as possible when referring to multiple components and materials, to avoid confusion and ineffectiveness.</td></tr><tr><td>5.1.3</td><td>Some consumers might rely more on additional information and awareness campaigns than others.</td></tr><tr><td>5.2.1</td><td>On-receptacle labels can provide valuable information at the point of disposal. They can complement on-pack labels, offering more space for information.</td></tr><tr><td>5.2.1</td><td>Like for on-pack labels, clear and actionable instructions are important on receptacles, as is consistent and prominent placement.</td></tr><tr><td>5.2.1</td><td>Persuasive messages should be used with caution, as they can lead to confusion and overinclusive recycling and sorting.</td></tr><tr><td>5.2.2</td><td>On-receptacle labels can reduce waste contamination by highlighting which materials should and/or should not be disposed of in a receptacle.</td></tr><tr><td>5.2.2</td><td>Images and icons are valuable complements to text if they are meaningful and familiar to users.</td></tr><tr><td>5.2.2</td><td>The number of items shown on the labels should be limited and should resemble commonly discarded items, as this can compensate for a lack of knowledge among users.</td></tr><tr><td>5.2.2</td><td>In contrast with on-pack labels, on-receptacle labels have the advantage of being attachable to some receptacles as stickers, making them more flexible and cost-effective.</td></tr><tr><td>5.2.2</td><td>WSLs should be designed and applied in a way that minimises the risk of information overload – they should be salient and clear and should provide information that is consistent with the relevant SWC scheme.</td></tr><tr><td>5.2.2</td><td>Pro-environmental prompts should be used with care.</td></tr><tr><td>5.2.2</td><td>A combination of information on desired and undesired behaviours might improve correct sorting.</td></tr><tr><td>5.2.2</td><td>WSLs can benefit from separate informative and pro-environmental messaging.</td></tr><tr><td>6.1.1</td><td>Insights on how packaging design elements are perceived and understood are limited.</td></tr><tr><td>6.1.1</td><td>Packaging serves as a natural platform for WSLs to convey sorting instructions to consumers.</td></tr><tr><td>6.1.1</td><td>WSLs should complement the relevant messages conveyed by packaging and simultaneously enhance the perceived value of packaging.</td></tr><tr><td>6.1.1</td><td>WSLs compete with prior and potentially conflicting consumer knowledge on how to sort waste correctly and with perceptions of waste as being disgusting and dirty.</td></tr><tr><td>6.1.1</td><td>Complementary information campaigns can create the knowledge required.</td></tr><tr><td>6.1.1</td><td>The co-design of WSLs involving different types of stakeholders is essential.</td></tr><tr><td>6.1.1</td><td>The evidence related to packaging and bin design is often incomplete. However, we still opted to include the papers that provided relevant insights for WSL design.</td></tr><tr><td>6.1.2</td><td>WSLs should positively contribute to the perceived value of packaging and provide consumers with a sense of convenience when sorting their waste.</td></tr><tr><td>6.1.2</td><td>The practicality of packaging, such as the ease of emptying or cleaning and the resealability, could be highlighted and supported on and by labels.</td></tr><tr><td>6.1.2</td><td>Graphical elements might be preferable over text on WSLs.</td></tr><tr><td>6.1.2</td><td>WSL design should consider that consumers might have only weak preferences for additional labels.</td></tr><tr><td>6.1.2</td><td>Characteristics of practical packaging design (i.e. being easy to empty, clean, reseal and reuse) may be complemented and highlighted by labels.</td></tr><tr><td>6.1.2</td><td>WSLs should be noticeable, salient and conspicuous.</td></tr><tr><td>6.1.2</td><td>Effects of WSLs on littering and waste sorting are limited by the available waste disposal infrastructure.</td></tr><tr><td>6.2.1</td><td>Colours of WSLs should be carefully selected, and consumers' previous encounters with colours and their associations with certain waste materials should be considered.</td></tr></table>
<table><tr><td>6.2.1</td><td>The colour coding of labels could align with public perceptions of the type of waste. Relating various colours to a particular waste type, rather than just to one colour, could cater to a wider range of individual associations. This may be particularly relevant when developing harmonised EU WSLs. However, consumer confusion may outweigh potential benefits of a multicolour scheme.</td></tr><tr><td>6.2.1</td><td>WSLs with less-preferred colours do not necessarily perform worse.</td></tr><tr><td>6.2.1</td><td>Various contextual factors influence the 'best' design of WSLs.</td></tr><tr><td>6.2.1</td><td>The costs of WSLs and their implementation need to be considered during their design and planning.</td></tr><tr><td>6.2.1</td><td>WSLs should be based on pilot studies, if possible.</td></tr><tr><td>6.2.2</td><td>Consciously designed bin shapes, lid designs and colour choices, together with well-placed, easy-to-understand labels, can increase user engagement, waste sorting and recycling rates.</td></tr><tr><td>6.2.2</td><td>WSLs should be placed in prominent positions and designed in close correspondence with the waste material to be disposed of for easy recognition, and the number of labels should be minimised to facilitate quicker identification of the relevant label and information.</td></tr><tr><td>6.2.2</td><td>Because well-designed lids can promote recycling and decrease contamination, it is important to consider the compatibility of labels with different bin and lid designs. The labels should be designed and positioned (or attachable, if they are stickers) in a way that complements the bin design and does not interfere with the usage of lids or slots.</td></tr><tr><td>6.2.2</td><td>Using bright and appealing colours may induce a positive emotional state and encourage more participation in waste sorting; however, the colours that are perceived as appealing can vary greatly.</td></tr></table>

Source: Authors' own creation.
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