Enabling desired disposal of compostable plastic packaging: an evaluation of disposal instruction labels

Introduction: This study evaluated a series of disposal instruction labels for their effectiveness in enabling the desired disposal of compostable plastic packaging.

Methods: Mixed methods were employed: an online experiment and a survey. UK citizens (n = 1,008) completed a task, sorting packaging labelled with various disposal instructions into one of three bins (general waste, food waste, and recycling). They also selected a preferred compostable disposal instruction logo and provided reasons for their preference.

Results: Items lacking disposal instructions followed intuitive disposal practices: items with a common practice of being compostable were most frequently disposed of into food waste; items with a common practice of being recycled were most frequently disposed of into recycling; and items with a common practice of being disposed of with general waste were most frequently disposed of with general waste. “Do not recycle” was effective at diverting compostable plastic packaging to general waste. The label “compost with food waste” had the highest rate of correct disposal in the food waste bin when compared to the control group and to the “compost” disposal instruction. “Compost with food waste”, however, was not statistically different from “put with food waste” or “recycle with food waste”; all three led to statistically similar disposal rates in the food waste bin. Qualitative findings showed that participants preferred clarity and directness in the disposal instructions logo denoting compostability.

Discussion: Findings suggest that citizens struggle to identify compostable plastic packaging from appearance alone. Clear direct disposal instruction wording can help enable the appropriate disposal behaviours. Qualitative findings showed that participants preferred clarity and directness in the disposal instructions logo denoting compostability. The depiction of simple yet unambiguous and instructive symbols was valued and likely to be the better instigators of behaviour change compared with associative symbols. Implications for labelling policy are discussed.

1 Introduction

Compostable plastics are growing in popularity as they promise a solution to the plastic waste crisis, particularly in terms of reducing waste from single-use plastic packaging. The current bioplastics market share is relatively small at <1% of the total 390 million tons of plastics produced globally; however, this figure is continually growing as applications of bioplastics evolve. The global production capacity for biodegradable plastics is set to increase from approximately 2.2 million tonnes in 2022 to approximately 6.3 million tonnes in 2027 (European Bioplastics, 2022a). There are, however, some fundamental problems, particularly in the UK.

These materials have become the “Wild West” of the packaging sector in that they are largely unregulated. There are issues with standards and certification, with limited rules around how they are labelled and marketed; manufacturers and suppliers are, therefore, at liberty to market them as they please. As effective systems for collecting, sorting, and processing compostable plastics are rare in the UK, the most frequent outcome is landfill or incineration, leading to confusion and mistrust of the environmental claims made of compostable plastics (Purkiss et al., 2022).

A further issue is that the terms “bioplastic”, “compostable”, “biobased”, and “biodegradable” are often used interchangeably, making it challenging to make sense of and accumulate the evidence. The terms have distinct meanings and nuanced differences. In the present study, we define these terms in line with European Bioplastic’s definition of bioplastics (European Bioplastics, 2022b) and the definitions of EU of compostable, biobased, and biodegradable plastics (European Commission, Directorate-General for Research and Innovation et al., 2020; European Commission, 2022). “Bioplastic” comprises a family of materials with different properties and applications as summarised in Table 1.

Table 1

Table 1. Table of definitions for bioplastic, biobased, biodegradable, and compostable plastic.

“Biobased” describes the source of the material at the start of the lifecycle of the plastic. Biobased plastics are fully or partially made from biological resources, rather than fossil raw materials. Biobased plastics are not necessarily biodegradable or compostable, terms which refer to how the material degrades at its end of life. The main difference between “biodegradable” and “compostable” in the context of plastic is that biodegradable plastic can take an undetermined time to break down. In contrast, compostable plastic must degrade, within a given timeframe, under specified composting conditions. There are different nationally and internationally accredited certifications assessing the credentials of compostable packaging. For a summary of these, the reader is referred elsewhere (e.g., Allison et al., 2022).

For the scope of this study, we are concerned with “compostable” plastics as “compostable” refers to a specific type of material that needs to be managed through specific routes. It thus allocates a clearer role to citizens as people responsible for sorting and disposing of waste through specific waste management routes, e.g., organic waste collection services.

Compostable plastics could be part of a sustainable UK packaging system; however, this would require UK citizens to adopt the appropriate waste management behaviours that lead to the materials being composted, i.e., putting those in the correct bin for processing (see Figure 1). Incorrect disposal offsets any of the potential environmental benefits of compostable plastic packaging. As compostable plastics are relatively new in terms of an integrated UK waste management strategy, there is little research to inform the design of behaviour change interventions to increase appropriate waste management of these materials. This study aimed to address this gap by investigating how to promote the desired disposal of compostable plastic packaging.

Figure 1

Figure 1. Circular economy of compostable plastics. Source: Allison et al. (2022).

Prior research on behaviour concerning compostable plastic disposal has largely focussed on the confusion surrounding “biobased”, “biodegradable”, and compostable plastics, identifying the need for clear, explicit, and instructive messaging on packaging (Sijtsema et al., 2016; Herbes et al., 2018; Dilkes-Hoffman et al., 2019). Evidence suggests that “biodegradable” is a confusing term as it offers little guidance on how to dispose of items (Allison et al., 2021; Purkiss et al., 2022). Studies in Germany (Taufik et al., 2020) and Netherlands (Ansink et al., 2022) show this confusion leads to incorrect disposal in practice. In the German study, the majority of participants (63%) disposed of this type of packaging in recycling rather than with organic waste, the correct option for that context. Even amongst those who observed the logos and disposal instructions on the packaging, these items were incorrectly disposed of. The reasons provided for their disposal decisions included the messaging being unclear or that they did not believe that plastic water bottles could be compostable. The Dutch study showed that only 35% of participants observed the logos on the packaging meant to communicate information about product biodegradability. Even amongst those who did observe the logos, these materials were usually incorrectly placed in recycling rather than residual waste, the correct option for that context.

While the evidence is clear that citizens struggle to dispose of these items correctly, it is unclear which types of messaging might promote desired disposal. These studies only tested one type of packaging format: plastic water bottles in the German study (Taufik et al., 2020) and plastic cups in the Dutch study (Ansink et al., 2022). The material more commonly used for the production of bottles or containers for beverages is polyethylene terephthalate (PET), and as PET is a recyclable material, the recycling bin would be the right bin (Nisticò, 2020). It is therefore important to conduct further studies testing a variety of packaging formats to minimise the potential confounds of past associations with a particular type of packaging.

An intervention aimed at promoting the correct disposal of compostable plastics within a UK implementation context has been developed but has yet to be evaluated for effectiveness in changing behaviour (Allison et al., 2022). This intervention consists of disposal instruction labels aimed at addressing one of the key barriers to correct disposal—not knowing which bin is the correct one for disposal. Readers are referred to this paper for further detail on the rationale and processes involved in the design of these disposal instruction labels. The disposal instructions are illustrated in this paper in section 2.3.1.1 Disposal instruction labels. The present study aimed to evaluate the impact of disposal instruction labels on the disposal of a range of different compostable plastic packaging formats.

At the time of this study in 2023, the UK Government was consulting on new mandatory labelling for packaging as part of the Extended Producer Responsibility Scheme reforms (DEFRA, 2020). Mandatory labelling aims to provide citizens with clear, binary instructions on what can and cannot be recycled: “recycle” or “do not recycle” (DEFRA, 2020). As compostable plastics are not deemed “recyclable” (as they are not designed to be mechanically recycled but to break down in specific composting conditions), the current plan is to label these, from 2024 onwards with “do not recycle” so they are disposed of with general waste (DEFRA, 2022). Most compostable plastic materials (e.g., PLA used in food packaging) would not degrade outside of an industrial compost facility as they have different material properties and requirements for processing compared to traditional fossil-based recyclable plastics (e.g., PET commonly used in single-use plastic water bottles) (Ruggero et al., 2019; Purkiss et al., 2022; Plastic Pollution Coalition, 2023). This binary mandatory labelling policy is significant because, from 2024 onwards, the UK government also aims to roll out nationwide food waste collection services. There are concerns that food waste collection services may become overwhelmed with large volumes of compostable plastic packaging waste that are not currently able to be processed by the majority of UK waste processing facilities. While there is an understanding amongst government and industry that collecting and processing these materials via food waste is likely to be the desired end-point (WRAP, 2021), this is an anticipated future scenario once other aspects of the compostable plastics system improve (see Figure 1).

Mandating the use of “do not recycle” to direct compostable plastics to general waste raises questions about behaviour change. To enable correct practices, it is necessary to gather information about what UK citizens are currently doing with compostable plastics without government-mandated disposal instruction labels. This would form a baseline for evaluating the impact of the disposal instruction “do not recycle”. As “recycle”/“do not recycle” is a binary messaging system that was designed for a two-bin scenario (recycling and general waste), it is empirically unknown how effective “do not recycle” will be once there are three mainstream options for the disposal of waste (recycling, general waste, and food waste). It is unclear how obvious the general waste bin will be as the disposal option for compostable plastics.

To prepare for an ideal future scenario where compostable plastics are disposed of with food waste (so they can be composted), the UK industry and government are discussing the potential implementation of a new disposal instruction logo indicating “compostability”. However, the UK government have been clear that this would only be used to label compostable plastics in the instance that there is a strong, evidence-based case for this scenario. For example, this will require sound evidence that there is adequate infrastructure in place to appropriately manage compostable plastics and evidence that compostable plastics provide ecological or agricultural benefits to soils or digestate when properly broken down (DEFRA, 2022). Therefore, there is also a need to understand which types of logos and disposal instructions might be most effective to denote the disposal of compostable waste with food waste to support policy decision-making in this area. To this end, the current study has four research questions:

1. In a three-bin scenario (food waste, general waste, and recycling), which bin do citizens put various types of compostable plastic packaging in when there is no disposal instruction?

2. In a three-bin scenario (food waste, general waste, and recycling), is “do not recycle” an effective disposal instruction for getting citizens to dispose of compostable plastic waste with general waste?

3. In a three-bin scenario (food waste, general waste, and recycling), which disposal instruction (“compost”, “compost with food waste”, “put with food waste”, and “recycle with food waste”) is most effective at getting citizens to put compostable plastic packaging with food waste?

4. Which potential alternative disposal instruction logos do citizens prefer for compostable packaging and why?

2 Materials and methods

All materials for this study including raw data and analysis code are available openly via Open Science Framework (OSF).¹

2.1 Participants

Study participants were members of the UK public (n = 1,008). They had to be over 18, normally resident in the UK for the last 12 months, and have sufficient English to complete the study. Participants were recruited via Prolific.co (n.d.) and advertising the study through email to the mailing list of The Big Compost Experiment (2020) citizen science project. Participants recruited via Prolific were compensated for their time at a rate of £10.23/h. Prolific ensures a representative sample in terms of gender, age, and ethnicity for UK participants. Participants recruited via the Big Compost Experiment took part voluntarily.

2.2 Design

This study had a mixed-methods design. It consisted of an experiment and a questionnaire.

The experiment had a mixed 6×11 factorial experimental design. There were two independent variables. One was between participants: disposal instruction, on six levels (control, do not recycle, compost, recycle with food waste, compost with food waste, and put with food waste). Disposal instruction was operationalised as the wording on the disposal instruction label presented to participants. Participants were randomly allocated to either one of the six disposal instruction conditions, one of which included a control condition consisting of no disposal instruction.

The other independent variable was within participants: packaging format, on 11 levels (sachet, bag, clamshell, container, plastic cup, food sticker, hot drink cup, coffee packaging, sandwich packaging, tea packaging, and ready meal tray). The packaging format was operationalised as the type of compostable plastic packaging the disposal instruction labels was tested on.

The study had one binary dependent variable: disposal behaviour (correct vs. incorrect) which was operationalised as whether or not participants disposed of the packaging in the desired bin during a given trial. To complete a trial correctly, all items had to be disposed of in the right bin. In the case of multi-material packaging, all parts had to be disposed of correctly; e.g., in the case of the tea package consisting of a box and compostable teabag, the participant had to sort the box correctly (i.e., in the recycling bin) and the teabag correctly (i.e., in the food waste bin or general waste bin depending on the analysis scenario) to get a correct score for that trial.

The questionnaire consisted of an online cross-sectional survey of close-ended and open-ended questions.

2.3 Materials

2.3.1 Experimental stimuli

2.3.1.1 Disposal instruction labels

The rationale for the disposal instructions labels has been justified in a previous publication (Allison et al., 2022). The final version of the wording and logo used in the disposal instruction labels is depicted in Figure 2.

Figure 2

Figure 2. Disposal instruction labels used for compostable plastic packaging.

2.3.1.2 Compostable packaging formats

The disposal instruction labels were superimposed onto images taken of 11 compostable plastic packaging formats (see Table 2). The authors recognise that different aspects of packaging labelling and communication design (words, logos, pictures, colour, and material choice) have varying influences on citizen behaviour and that disposal instruction labels are one aspect of a larger complex system of communication (WRAP, 2021). These items were selected as they are available in high street shops in the UK, marketed as compostable, and made from compostable materials (e.g., PLA, PBAT, and corn starch).

Table 2

Table 2. Table showing the images of the packaging formats used in trials.

2.3.1.3 Distractor packaging formats

Distractor stimuli were also used and consisted of images taken of common general waste and dry recycling items, e.g., juice cartons and chocolate wrappers (see Table 2). The disposal instruction labels that were superimposed onto the distractor items consisted of the disposal instruction “recycle” for recyclable items and “do not recycle” for general waste items, with the same OPRL Recycle Now logo, as this is the current UK system for labelling this type of waste, at the time of this study (OPRL, n.d). In the control condition, the distractor waste items had no disposal instruction label.

2.3.2 Questionnaire

2.3.2.1 Hypothetical disposal instruction logo for compostable waste

Introduced in a previous publication (Allison et al., 2022), Appendix A in OSF² details the set of 15 hypothetical disposal instruction logos that were developed in collaboration with a designer at the UCL Plastic Waste Innovation Hub (DP) and industry, policy, and academic stakeholders. They were developed using associative graphic imagery commonly used in UK waste disposal infrastructure and communications, such as an image of a “leaf”, “seedling”, “apple core”, “chasing arrows recycling symbol”, and WRAP’s “chasing heart” logo.

Participants were asked to select their preferred logo, provide a reason for their preference (“Please provide a reason for your answer”), and provide their thoughts on a potentially better disposal instruction logo for compostable packaging waste (“If you think there could be a better disposal instruction label for compostable packaging than the ones we have shown you, could you please share your thoughts with us?”).

2.3.2.2 Britain talks climate toolkit

The Britain Talks Climate citizen engagement toolkit’s “Golden Questions” were used to collect psychological demographics (Wang et al., 2020). Based on how participants respond to the toolkit’s 16 questions, the tool “segments” respondents into one of seven possible “psychological” groups (see Appendix B in OSF: https://osf.io/9p4kx).

2.4 Procedure

Ethical approval for the study was received from UCL (project ID: CEHP/2020/579, data protection: Z6364106/2022/03/63). The study was built on Gorilla (Anwyl-Irvine et al., 2020) and piloted with a sample of university staff and students before data collection for usability and accessibility. Participants accessed the study via an online web link, which took approximately 10 min to complete. Informed consent was obtained before any data collection. Data collection occurred between the 14th and 28th of November 2022.

Participants completed 16 trials in total. Each trial consisted of sorting stimuli into one of three bins: food waste, recycling, or general waste (if the packaging had multiple parts, each part had to be sorted separately). An example is shown in Figure 3. Eleven trials consisted of sorting compostable packaging formats. Five trials consisted of sorting distractor packaging formats. The order of trials was counterbalanced to minimise order effects (Krosnick and Alwin, 1987). Participants subsequently completed a survey answering questions about their demographics and logo preferences.

Figure 3

Figure 3. Example trials from the “compost” disposal instruction condition. The image on the left depicts an example of what participants saw when sorting an item of mono-material packaging, whereas the image on the right depicts an example of what participants saw when sorting an item of multi-material packaging.

2.5 Data analysis

Data were prepared for analysis in Microsoft Excel and analysed using Microsoft Excel and RStudio (RStudio Team, 2020).

To answer Research Question 1, all compostable plastic packaging components were analysed in isolation and not as part of a wider packaging format, e.g., just the teabag, not the box. Frequencies were used to summarise findings. Inferential statistics were run to answer Research Question 2 and Research Question 3. The data analytic approaches for these two research questions are detailed in the subsequent sections. To answer Research Question 4, percentages were used to summarise logo preferences. Thematic analyses (Braun and Clarke, 2006) were conducted on open-ended responses exploring reasons for preference and ideas for a better logo.

2.5.1 Building the models for research question 2 and research question 3

R Packages “lme4” (Bates et al., 2009) and “lmertest” (Kuznetsova et al., 2015) were used for the main tests and “emmeans” (Lenth et al., 2019) for follow-up tests. Two separate generalised linear mixed-effects models were run to see whether disposal instructions predicted correct disposal. To account for the repeated-measures methodology (all participants disposed of each packaging format), a by-participant random intercept was added. The same control group was used for the analyses concerning Research Question 2 and Research Question 3. In the former, the control group results were based on the data coded as the general waste bin being the correct bin. In the latter, the control group results were based on the data coded as the food waste bin being the correct bin.

2.5.1.1 Control variables

To assess for any control variables, the relationship between the socioeconomic (i.e., age, gender, income, and education), psychological (i.e., ideological orientation), and behavioural (i.e., home-composting and food waste recycling status) demographic variables and the dependent variable (i.e., correct disposal) was explored via two different approaches: (a) separate generalised linear mixed-effects models per variable and (b) one generalised linear mixed-effects model with all control variables included. The control variables were introduced as predictors of correct disposal, with a by-participant random intercept, following the structure of the main models. Variables found to be significant at p < 0.05 across both approaches were entered into the main models. If the main models failed to converge, the control variables were removed on the basis that it is not necessarily the “maximal”, but a more parsimonious model, with a random effects structure, that may be most suitable for describing the data in factorial experiments with repeated-measures aspects (Matuschek et al., 2017; Seedorff et al., 2019). Details of the control variable analyses can be found in Appendix C in OSF.³

2.5.2 In a three-bin scenario, is “do not recycle” an effective disposal instruction for getting citizens to dispose of compostable plastic waste with general waste? (Research question 2)

The first independent variable in the model was the disposal instruction, operationalised as either the control or the “do not recycle” disposal instruction. The second independent variable was the packaging format. An interaction term was included to assess whether the effectiveness of “do not recycle” as a disposal instruction varied according to packaging format. The dependent variable was binary (correct vs. incorrect disposal). Correct disposal was operationalised as the disposal of compostable plastic packaging items with general waste. Incorrect disposal was operationalised as disposal with food waste or recycling. The final model (Conditional R² = 57.5%) had the following structure:⁴

$\begin{array}{l}\mathrm{disposal}~\mathrm{experimental}:{\mathrm{group}}^{\ast }\mathrm{packaging}:\mathrm{format}\\ +\left(1|\mathrm{participant}:\mathrm{id}\right)\end{array}$

2.5.3 In a three-bin scenario, which disposal instruction is most effective at getting citizens to put compostable plastic packaging with food waste? (Research question 3)

The first independent variable in the model run was the disposal instruction operationalised as either the control, “recycle with food waste”, “compost”, “compost with food waste”, or “put with food waste” disposal instructions. The second independent variable was the packaging format. Correct disposal was operationalised as the disposal of compostable plastic packaging items with food waste. Incorrect disposal was operationalised as disposal with general waste or recycling. Disposal rates across the different conditions were compared against each other. The control variables home composting status and food waste recycling status were significantly associated with disposal rates and so were included in the final analysis.⁵

An interaction term was initially included to assess whether the effectiveness of the disposal instructions varied according to the packaging format. However, the model did not converge, likely because the interaction term led to the estimation of more than 5×11 parameters. To simplify the model, the random intercept was prioritised over the interaction between the fixed effects in line with guidance (Sonderegger, 2023) and given how much variance the random-effect structure explained (marginal R² = 38%; conditional R² = 62%). The final model had the following structure:

$\begin{array}{l}\mathrm{disposal}~\mathrm{experimental}:\mathrm{group}+\mathrm{packaging}:\mathrm{format}\\ +\mathrm{home}:\mathrm{composting}:\mathrm{status}+\mathrm{food}:\mathrm{recycling}:\mathrm{status}\left(1|\mathrm{participant}:\mathrm{id}\right)\end{array}$

3 Results

3.1 Participant characteristics

Participant characteristics are summarised in Table 3. The majority identified as women (55%) followed by men (43.8%) and with a small percentage as non-binary (0.6%) or preferring not to disclose their gender (0.6%). The mean age of participants was 53.57 (SD = 16.59) with most either educated to undergraduate (37.1%) or master’s level (22%). This indicates an older (ONS, 2022) and more educated (OECD, 2023) sample than UK averages. The majority of survey participants had annual household incomes less than £45,000, aligning with national figures (ONS, 2020).

Table 3

Table 3. Participant characteristics.

The majority of participants were classified as “Progressive activists” (39.5%) and “Established liberals” (21.6%) which is considerably higher than the UK averages of 13 and 12%, respectively (Wang et al., 2020). The third most populous segment was “Civic pragmatists” (16.1%), which is closer to the UK average of 13% (Wang et al., 2020).

About half of the participants (53.67%) indicated that they were being provided with a local food waste collection service. This mirrors UK statistics for household food waste collection services with about half of households offering such services (DEFRA, 2017). Almost all participants recycled dry recyclables (97.62%). About half engaged in home-composting (53.57%), which is likely to be much higher than national averages, and other studies suggest that only about a third of households in England with a garden home-compost (Eades et al., 2020). The question asking the likelihood of engaging with local food waste collection services if provided with free compostable liners was explored in more depth by asking participants to provide a reason for their answer. This supplementary analysis, including directions to the raw data and codebook, can be found in Appendix D in OSF.⁶

3.2 General descriptive statistics

Appendix E in OSF⁷ summarises the percentage of correct disposal of recyclable and general waste items used as distractor stimuli. Appendix F in OSF⁸ depicts the overall count data across all conditions, i.e., the frequency of disposal, into each bin, per disposal instruction for each item of mono-material and multi-material packaging, respectively.

3.3 Which bin do citizens put various types of compostable plastic packaging in when there is no disposal instruction label? (Research question 1)

Appendix G in OSF⁹ summarises the frequencies with which each item of compostable plastic packaging was disposed of in each bin when there was no disposal instruction (i.e., the control condition). The packaging parts that were most likely to go in general waste were as follows: sachet, food sticker, coffee pod, sandwich film, and ready meal film. Packaging parts that were most likely to go in food waste were as follows: bag and teabag. Packaging parts that were most likely to go in recycling were as follows: clamshell, container, plastic cup, hot drink cup, hot drink lid, and ready meal tray.

3.4 Is “do not recycle” an effective disposal instruction for getting citizens to dispose of compostable plastic waste with general waste? (Research question 2)

Appendix H in OSF¹⁰ summarises the rates of correct disposal rate for each packaging format (i.e., the percentage of participants putting that item in general waste vs. food waste or recycling). Results showed that when the label reads “do not recycle”, participants were, overall, 11.15% more likely to correctly dispose of the packaging in the general waste bin (OR = 0.09, 95% CI [0.08, 0.10], p < 0.0001). Post-hoc analyses revealed that this effect was evident for seven packaging formats – all but the sachet, the food sticker, the sandwich, and the tea (see Table 4).

Table 4

Table 4. Post-hoc comparisons for correct disposal of each packaging format in the general waste bin between the control and “do not recycle” conditions.

In a three-bin scenario, “do not recycle”, overall, significantly increased participants’ disposal of compostable plastic packaging with general waste when compared with controls with no disposal instruction. However, this effect was coming from certain packaging formats: the sachet, bag, clamshell, container, cup, hot drink container, coffee, sandwich, and ready meal. It was not coming from the tea, sachet, sandwich, or food sticker packaging formats for which the difference in disposal rate was not statistically significant.

3.5 Which disposal instruction is most effective at getting citizens to put compostable plastic packaging with food waste? (Research question 3)

Appendix I in OSF¹¹ summarises the rates of correct disposal for each packaging format (i.e., percentage of participants putting that item in food waste vs. general waste or recycling). Across all conditions, the two packaging formats with the highest rate of correct disposal in the food waste bin were the tea and bag packaging formats. Food waste recycling status was not significantly associated with disposal rates in the food waste bin (OR = 0.16, 95% CI [0.12, 1.28], p = 0.20); however, home-composting status was (OR = −0.30, 95% CI [−0.42, −0.18], p = 0.01). The odds of correctly disposing of food waste were higher amongst those who did not engage in home composting.

Results showed that, in a three-bin scenario, “compost with food waste” had the highest rate of correct disposal in the food waste bin when compared to the control group with no disposal instruction. However, it was not statistically different from “put with food waste” or “recycle with food waste”. All three disposal instructions led to statistically similar disposal rates in the food waste bin. “Compost with food waste”, “put with food waste”, and “recycle with food waste” were all significantly better at promoting the disposal of compostable plastic packaging in the food waste bin when compared with “compost”. These results can be seen in Table 5.

Table 5

Table 5. Comparisons of correct disposal between disposal instruction labels designed to denote disposal of compostable plastic packaging with food waste.

3.6 Which potential alternative disposal instruction logos do citizens prefer for compostable packaging and why? (Research question 4)

Logo preferences are shown in Appendix J in OSF.¹² Thematic findings for the top two logos are summarised in this paper, i.e., Logo 15 (49.8%) and Logo 5 (24.58%). The full detailed thematic analyses for the top five logos (>5% preference) are openly available via OSF.¹³

Participants selected their preferred logo on the basis that it was the clearest to understand. However, there was variation between logos in terms of why it was perceived this way (see Table 6). Logo 15 was valued for its inclusion of a range of organic waste materials, instructive imagery, and avoidance of associative symbols. Logo 5 was valued for its use of associative symbols, which were deemed intuitive and logical. Nonetheless, across both logos, participants felt that a logo alone would be insufficient as a disposal instruction strategy and emphasised the importance of written disposal instructions to reduce any potential confusion. Participants’ ideas for a better logo can be found in Appendix K in OSF.¹⁴

Table 6

Table 6. Thematic analysis on reasons for logo preferences.

4 Discussion

We discuss the results according to each research question followed by the implications of the study findings for policy and practice. Study strengths, limitations, and avenues for future research are then considered.

4.1 Which bin do citizens put various types of compostable plastic packaging in when there is no disposal instruction? (Research question 1)

Results show that with no disposal instruction label, the correct disposal of these items is not obvious from their appearance. Items that “look” like dry recyclable waste were put in the recycling bin (i.e., similar appearance to traditional dry recyclable plastics like PET), those that “look” like general waste were put in general waste (i.e., similar appearance to non-recyclable plastic like and semi-flexible or plastic-coated materials), and those that have a familiar status as being compostable went in food waste (i.e., the bag and teabag).

These findings align with Ansink et al. (2022) and Taufik et al. (2020) where citizens incorrectly disposed of compostable plastic cups and water bottles into the recycling bin, even those labelled with messaging designed to communicate disposal instructions. The authors speculated that these patterns are likely to be due to a habitual association between these packaging formats and the recycling bin—it is difficult to “snap” citizens out of their default waste management patterns. In the present study, the teabag and compostable shopping bags may have been less likely to trigger an automatic response with the recycling bin as they do not “look” like traditionally recyclable waste, unlike the plastic water bottles and cups in the Ansink et al. (2022) and Taufik et al. (2020) studies. It is also likely that the UK public’s familiarity with the compostability of teabags and the particular brand of shopping bag used in this study led to them being more likely to put them in food waste.

4.2 Is “do not recycle” an effective disposal instruction for getting citizens to dispose of compostable plastic waste with general waste? (Research question 2)

The label “do not recycle”, overall, significantly increased the rate of correct disposal of general waste. However, post-hoc analyses revealed that this effect was coming from the bag, clamshell, container, cup, hot drink container (cup and lid), coffee (box and pod), and ready meal (sleeve, tray, and film), not the tea (teabag and box), sandwich (box and film), and sachet or food sticker. The significant effect of “do not recycle” appears to be mostly due to packaging that “looks” like dry recyclate being re-directed to general waste. As the packaging that “looks” like general waste already had high disposal rates with general waste in the control, “do not recycle” only increased that figure from what was already quite high to even higher. In the case of the sachet, sandwich, and food sticker, the increase was not high enough to reach statistical significance as disposal rates into general waste were already very high in the comparison group. It is impossible that “ceiling effects” were occurring. This is when the scores of research participants are clustered near the best possible score (i.e., the “ceiling”; in this case, 100% correct disposal) and so the measure (the disposal instruction) loses value.

The post-hoc analyses showed that “do not recycle” did not significantly increase the rate of correct disposal for the tea (teabag and box). While the correct disposal of compostable shopping bags did increase significantly, the rate was still low in comparison with the other packaging formats; correct disposal was only increased to 50%. An explanation for this could be that for items that “look” recyclable or like general waste, the food waste bin was not a plausible option. It is likely less intuitive to dispose of something that does not “look” organic with food waste than to dispose of something that “looks” recyclable or organic with general waste. For items that have entered the mainstream UK public consciousness as being compostable (e.g., teabags and compostable shopping bags), “do not recycle” may not indicate a clear enough disposal instruction in a three-bin system and so disposal decisions are being split between the food waste bin (because that is the intuitive option) and general waste bin (because that is what this instruction has been used to denote in the past).

These findings suggest that “do not recycle” may be effective for diverting some types of waste when there are three bins to choose from but not for waste items that have an association with compostability. For items associated with compostability, “do not recycle” may not provide the clear and direct instruction that seems to be a running theme in terms of what citizens desire in a disposal instruction label. An avenue for future research could be to investigate whether a direct positive command, e.g., “dispose of with general waste”, would perform better at increasing rates of compostable plastic packaging with general waste.

4.3 Which disposal instruction is most effective at getting citizens to put compostable plastic packaging with food waste? (Research question 3)

To promote the disposal of food waste, “compost with food waste” had the highest rate of correct disposal in the food waste bin when compared to no disposal instruction. However, there was no difference between the three types of disposal instruction. This suggests that explicitly mentioning “food waste” is important as “compost” alone was not as effective as “compost with food waste”, “put with food waste”, or “recycle with food waste”.

These findings support and extend prior research. There is a growing body of evidence showing citizens’ desire for clear, specific, and directive disposal instructions to enable the correct waste management behaviours (Langley et al., 2011; WRAP, 2021). This study provides supporting experimental evidence; clear, directive disposal instructions are not only desired by citizens but also promote the disposal of compostable plastics in the instructed manner.

Engagement in home composting was, overall, associated with reduced rates of correct disposal of packaging with food waste. A possible explanation for this is that many of the home composters may have been participants of the Big Compost Experiment citizen science project as the mailing list of this project was used to recruit participants. A key finding from this citizen science project was that much of the compostable plastic packaging on the UK market does not break down efficiently in most home composts (Purkiss et al., 2022). A possible reason is that compostable materials require specific, controlled conditions to biodegrade effectively, which can be difficult to maintain given the variability of home composting methods and conditions (e.g., Arrigoni et al., 2018). It is therefore plausible that home-composting participants disposed of these types of packaging in the general waste bin instead of the food waste bin as they did not trust the disposal instructions. As home composting is a niche practice in the UK (Eades et al., 2020), the impact of this on the wider population in terms of a broader waste management strategy is likely to be minimal.

4.4 Which potential alternative disposal instruction logos do citizens prefer for compostable packaging and why? (Research question 4)

The logo that participants had the strongest preference for a simple, direct, comprehensive, and explicit in denoting disposal in the food waste bin. The second preference was for a logo based on adaptations of the more established “chasing arrows” recycling logo. Some thought that an instructive logo was easier to understand, whereas others thought that a logo they associated with recycling was easier to understand.

Most logos denoting compostability make use of associative symbols, e.g., the European Bioplastics “seedling” logo. Nonetheless, symbols only have meaning within a context as they are something that represents or stands for something else. In the case of the European Bioplastics seedling logo, the logo represents adherence to compostability standards set by independent certifiers (e.g., TÜV Austria and DEN CERTCO) (European Bioplastics, 2019). In addition, there are highly efficient organic waste collection systems across Europe, including Austria, Slovenia, Belgium, and Germany where the bio-waste capture rate is over 60% (this figure represents the percentage of food waste collected as a percentage of food waste generated) (Brusselaers and Van Der Linden, 2020). Their success can be attributed to infrastructure, including simple-to-use, nationally uniform and reliable waste collection and processing services but also to high citizen engagement, which has been achieved through behaviour change interventions, including effective educational and motivational communications (Favoino and Giavini, 2020). The European Bioplastics seedling logo is therefore emblematic of a collectively understood and agreed upon something else. The more instructive logos were likely preferred in a UK context given the wide-scale citizen confusion about these materials and the wider system failures outlined earlier. In a UK context, there is yet to be a functional and collectively established something else for which an associative symbol could be emblematic of meaningfully.

Another reason for the differences in preferences could be that those who are generally more acquainted with and involved in waste management (e.g., those who home compost, already recycle food waste or who are generally pro-environmentally oriented) are more knowledgeable and so prefer associative recycling logic, whereas less knowledgeable citizens are more likely to prefer a direct and instructive logo. This is difficult to ascertain as the thematic findings were not linked to survey respondents’ home composting status, recycling status, or ideological orientation. Overall, the findings suggest that a more direct and instructive logo is likely the preferable choice if the goal is to maximise general public engagement. This is corroborated by the quantitative results; clear, instructive messaging was most effective for all.

4.5 Implications

The findings have implications for government policies and industry practices around labelling of compostable plastics. To direct items into food waste, explicitly mentioning food waste in a disposal instruction is likely to be effective. To direct items to general waste, “do not recycle” might work for some packaging formats, but it is likely that a clearer, directive disposal instruction; e.g. “dispose of with general waste” may be more effective. Evidence from WRAP (The Waste and Resources Action Programme; a climate action NGO and British charity dedicated to working with businesses, individuals and communities to achieve a circular economy) corroborates this; citizens have a clear preference for labels which are directive, telling them exactly what to do with waste (WRAP, 2021). If a separate compostability logo comes into practice, it will be important for this to be as direct, explicit, and comprehensive as possible. While symbolic and associative logos may be liked, for example, those based on adaptations of the more established “chasing arrows” recycling logo, these types of logos may be more aesthetically pleasing than they are instigators of behaviour change.

The study findings also have wider implications for product and packaging design. The findings from the control group with no disposal instructions show that citizens struggle to identify compostable plastic packaging based on appearance alone. Other studies support that distinguishing these materials from their appearance is challenging (Herbes et al., 2020; Taufik et al., 2020). A recent study by the US-based Composting Consortium and Biodegradable Products Institute (BPI) shows that there was an increase in US citizens’ identification of a range of compostable plastic packaging formats based on varying uses of colour (Composting Consortium, 2023). It may therefore be useful to ensure compostable plastic packaging is as distinct as possible to enable their identification and promote their correct sorting for disposal. This could look like using material textures and colours that are not associated with the look and feel of recyclable waste.

4.6 Strength, limitations, and future research

A strength of this study is the testing of a range of different compostable plastic packaging formats. Prior experiments have relied on testing a single packaging format (e.g., plastic water bottles or plastic cups) (Taufik et al., 2020; Ansink et al., 2022). Testing a wider range of packaging formats minimises the potential confounding effects of participants’ existing behavioural associations with a type of packaging.

The study method presents some issues with ecological validity as it does not accurately simulate the real-world disposal environment, meaning that the effectiveness of the disposal instructions may be overestimated. The stimuli were maximised on screen and participants concentrated on a science experiment. In reality, people often do not look at or notice labels on packaging, as disposal behaviour is shown to be highly habitual and automatic (Taufik et al., 2020; Ansink et al., 2022). Even if the ideal wording and logo for compostable packaging were identified, people need to engage with them in the first instance.

Natural experiments or other types of in-person user experience studies where people physically interact with packaging can overcome some of these limitations and improve confidence in the generalisability of findings. Testing potential interaction effects between other packaging attributes on disposal behaviour can also extend findings as they have been found to influence disposal decisions, e.g., the feel of the materials used for packaging, placement of information on packaging (Nemat et al., 2020), the degree of distortion of packaging (Baxter et al., 2016; Trudel et al., 2016), or the degree to which the packaging is wet or contaminated (Langley et al., 2011).

Future research is required to confirm whether other, clearer disposal instructions might be better for diverting compostable plastic packaging to general waste. Based on the study findings, we speculate that a positive direct command; e.g., “dispose of with general waste” may be a better disposal instruction when compared to the negative command “do not recycle”, especially for more ambiguous packaging formats or those that look organic. The present experimental paradigm could be adapted to investigate this.

5 Conclusion

This study aimed to evaluate disposal instruction labels for their effectiveness in promoting the desired disposal of compostable plastic packaging. With no disposal instructions, citizens disposed of compostable plastic packaging using intuitive logic. For instance, items that “look” compostable were put in food waste, items that “look” recyclable were put in recycling, and items that “look” like general waste were put in general waste. These automatic pathways may nonetheless be disrupted with the appropriate disposal instructions. While “do not recycle” may currently work to divert some types of compostable plastic packaging to general waste, it may not work for all, especially items with a common practice of being compostable, e.g., tea bags. Disposal instructions that explicitly mentioned food waste (e.g., “compost with food waste” vs. “compost”) led to a statistically higher rate of disposal of compostable plastics in the food waste bin. Citizens valued the depiction of simple yet comprehensive, instructive, and explicit symbols in a logo for compostable waste, i.e., an arrow pointing into a bin, avoidance of associative symbols such as variations of the recycling chasing arrows symbol and depiction of a variety of different organic waste items that one can put in a food bin for local collection. Taken together, findings are in line with a substantial body of research showing that citizens have strong preferences for disposal instructions and logos that are clear, directional and explicit. Additional in-person studies and natural experiments in this area can improve the conclusiveness of findings.

Data availability statement

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/supplementary material.

Ethics statement

The studies involving humans were approved by UCL Psychology and Language Sciences Ethics Committee. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

Author contributions

AA: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. AB: Writing – review & editing, Validation, Software, Investigation, Formal analysis, Data curation. DP: Writing – review & editing, Visualization, Validation, Supervision, Resources, Methodology, Funding acquisition, Data curation, Conceptualization. FL: Writing – review & editing, Supervision, Conceptualization. SM: Writing – review & editing, Supervision, Funding acquisition, Conceptualization. MM: Writing – review & editing, Validation, Supervision, Methodology, Funding acquisition, Conceptualization.

Funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This study was supported by the EPSRC and UKRI, under grants EP/S024883/1 and NE/V010735/1.

Acknowledgments

We thank Éanna Ó hAnrachtaigh for their help with developing a data analysis protocol in the early days of this project. We thank Miles Tufft for their guidance in developing the research questions and experimental design. We thank Jakob Kiessling for their help in coding interview data for the thematic analyses. We thank all past and present members of the UCL Plastic Waste Innovation Hub for their help in contributing to this research.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Footnotes

1. ^ https://osf.io/vj9hy/

2. ^ https://osf.io/xg73u/

3. ^ https://osf.io/vjmne

4. ^The control variable income was initially included in the main model; this was the only control variable significantly associated with disposal rates. However, the main model did not converge when income was included and so was removed.

5. ^Age was also significant so initially included in the model but the model did not converge. As this was the variable with the lowest estimate, it was omitted from the analysis to reduce complexity as per guidance (Seedorff et al., 2019; Matuschek et al., 2021).

6. ^ https://osf.io/jvfyk

7. ^ https://osf.io/5mquj

8. ^ https://osf.io/jm35y

9. ^ https://osf.io/pn7re

10. ^ https://osf.io/j8wm3

11. ^ https://osf.io/vk5a7

12. ^ https://osf.io/px4d3

13. ^ https://osf.io/7xnv6

14. ^ https://osf.io/xczdt

References

Allison, A. L., Lorencatto, F., Michie, S., and Miodownik, M. (2021). Barriers and enablers to buying biodegradable and compostable plastic packaging. Sustainability 13:1463. doi: 10.3390/su13031463

Crossref Full Text | Google Scholar

Allison, A. L., Purkiss, D., Lorencatto, F., Miodownik, M., and Michie, S. (2022). Improving compostable plastic disposal: an application of the behavior change wheel intervention development method. Front. Sustain. 3:92. doi: 10.3389/frsus.2022.968152

Crossref Full Text | Google Scholar

Ansink, E., Wijk, L., and Zuidmeer, F. (2022). No clue about bioplastics. Ecol. Econ. 191:107245. doi: 10.1016/j.ecolecon.2021.107245

Crossref Full Text | Google Scholar

Anwyl-Irvine, A. L., Massonnié, J., Flitton, A., Kirkham, N., and Evershed, J. K. (2020). Gorilla in our midst: an online behavioral experiment builder. Behav. Res. Methods 52, 388–407. doi: 10.3758/s13428-019-01237-x

PubMed Abstract | Crossref Full Text | Google Scholar

Arrigoni, J. P., Paladino, G., Garibaldi, L. A., and Laos, F. (2018). Inside the small-scale composting of kitchen and garden wastes: thermal performance and stratification effect in vertical compost bins. Waste Manag. 76, 284–293. doi: 10.1016/j.wasman.2018.03.010

PubMed Abstract | Crossref Full Text | Google Scholar

Bates, D., Maechler, M., Bolker, B., Walker, S., Christensen, R. H. B., Singmann, H., et al. (2009). “Package ‘lme4’.” Available at: http://lme4.r-forge.r-project.org.

Google Scholar

Baxter, W. , Aurisicchio, M., and Childs, P. R. (2016). "Tear here: The impact of object transformations on proper disposal." In: Proceedings of 20th IAPRI World Conference on Packaging (Vol. 12).

Google Scholar

Braun, V., and Clarke, V. (2006). Using thematic analysis in psychology. Qual. Res. Psychol. 3, 77–101. doi: 10.1191/1478088706qp063oa

Crossref Full Text | Google Scholar

Brusselaers, J., and Van Der Linden, A. (2020). “Bio-waste in Europe—Turning challenges into opportunities.” Available at: https://research.vu.nl/en/publications/bio-waste-in-europe-turning-challenges-into-opportunities

Google Scholar

Composting Consortium (2023). Unpacking labeling and design: U.S : Consumer Perception of Compostable Packaging.

Google Scholar

DEFRA (2017). DEFRA Committee. Oral Evidence: Food Waste in England, HC 429 ; DEFRA: London, UK. Available online: https://publications.parliament.uk/pa/cm201617/cmselect/cmenvfru/429/429.pdf

Google Scholar

DEFRA. (2020). “Environment Bill.” Available at: https://publications.parliament.uk/pa/bills/cbill/58-01/0220/200220.pdf (Accessed January 20, 2020).

Google Scholar

DEFRA (2022). Extended producer responsibility for packaging : DEFRA.

Google Scholar

Dilkes-Hoffman, L., Ashworth, P., Laycock, B., Pratt, S., and Lant, P. (2019). Public attitudes towards bioplastics–knowledge, perception and end-of-life management. Resour. Conserv. Recycl. 151:104479. doi: 10.1016/j.resconrec.2019.104479

Crossref Full Text | Google Scholar

Eades, P., Kusch-Brandt, S., Heaven, S., and Banks, C. J. (2020). Estimating the generation of garden waste in England and the differences between rural and urban areas. Resources 9:8. doi: 10.3390/resources9010008

Crossref Full Text | Google Scholar

European Bioplastics (2019). Guidelines for use of the seedling logo. European Bioplastic. Available at: https://www.tuv-at.be/fileadmin/user_upload/docs/download-documents/GEN/EUBP_Guidelines_Seedling_logo.pdf

Google Scholar

European Bioplastics. (2022a). “Bioplastics market data.” Available at: https://www.european-bioplastics.org/market/ (Accessed February 27, 2023).

Google Scholar

European Bioplastics. (2022b). “What are bioplastics? ” Available at: https://docs.european-bioplastics.org/publications/fs/EuBP_FS_What_are_bioplastics.pdf (Accessed January 6, 2023).

Google Scholar

European Commission. (2022). “Biobased, biodegradable and compostable plastics.” Available at: https://environment.ec.europa.eu/topics/plastics/biobased-biodegradable-and-compostable-plastics_en (Accessed Jan 3, 2023).

Google Scholar

European Commission, Directorate-General for Research and Innovation (2020). Biodegradability of plastics in the open environment : Publications Office of the European Union.

Google Scholar

Favoino, E., and Giavini, M. (2020). Bio-waste generation in the EU: current capture levels and future potential. Bio-Based Industries Consortium (BIC).

Google Scholar

Herbes, C., Beuthner, C., and Ramme, I. (2018). Consumer attitudes towards biobased packaging–a cross-cultural comparative study. J. Clean. Prod. 194, 203–218. doi: 10.1016/j.jclepro.2018.05.106

Crossref Full Text | Google Scholar

Herbes, C., Beuthner, C., and Ramme, I. (2020). How green is your packaging—a comparative international study of cues consumers use to recognize environmentally friendly packaging. Int. J. Consum. Stud. 44, 258–271. doi: 10.1111/ijcs.12560

Crossref Full Text | Google Scholar

Krosnick, J. A., and Alwin, D. F. (1987). An evaluation of a cognitive theory of response-order effects in survey measurement. Public Opin. Q. 51, 201–219. doi: 10.1086/269029

Crossref Full Text | Google Scholar

Kuznetsova, A., Brockhoff, P. B., and Christensen, R. H. B. (2015). “Package ‘lmertest’.” R package version 2. 734.

Google Scholar

Langley, J., Turner, N., and Yoxall, A. (2011). Attributes of packaging and influences on waste. Packag. Technol. Sci. 24, 161–175. doi: 10.1002/pts.924

Crossref Full Text | Google Scholar

Lenth, R., Singmann, H., Love, J., Buerkner, P., and Herve, M. (2019). Package “emmeans”.

Google Scholar

Matuschek, H., Kliegl, R., Vasishth, S., Baayen, H., and Bates, D. (2017). Balancing type I error and power in linear mixed models. J. Mem. Lang. 94, 305–315. doi: 10.1016/j.jml.2017.01.001

Crossref Full Text | Google Scholar

Nemat, B., Razzaghi, M., Bolton, K., and Rousta, K. (2020). The potential of food packaging attributes to influence consumers’ decisions to sort waste. Sustainability 12:2234. doi: 10.3390/su12062234

Crossref Full Text | Google Scholar

Nisticò, R. (2020). Polyethylene terephthalate (PET) in the packaging industry. Polym. Test. 90:106707. doi: 10.1016/j.polymertesting.2020.106707

Crossref Full Text | Google Scholar

OECD. (2023). Education at a Glance 2023 : OECD Indicators, OECD Publishing, Paris, doi: 10.1787/e13bef63-en

Crossref Full Text | Google Scholar

Office of National Statistics (2020). Number of UK Households Earning above and below £45,000 Equivalised Annual Gross Income for the Financial Year Ending 2019. Available online: https://www.ons.gov.uk/peoplepopulationandcommunity/personalandhouseholdfinances/incomeandwealth/adhocs/11791numberofukhouseholdsearningaboveandbelow45000equivalisedannualgrossincomeforthefinancialyearending2019

Google Scholar

Office for National Statistics (2022). Population estimates for the UK, England, Wales, Scotland, and Northern Ireland: mid-2022. Retrieved from: https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationestimates/bulletins/annualmidyearpopulationestimates/mid2022 (Accessed 20 May 2024)

Google Scholar

OPRL (n.d ). “How the scheme works.” Available at: https://oprl.org.uk/what-we-do/how-the-scheme-works/ (Accessed July 14, 2023).

Google Scholar

Plastic Pollution Coalition. (2023). Better alternatives 3.0: a case study on bioplastic products and packaging. Available at: https://www.5gyres.org/betteralternatives

Google Scholar

Prolific.co (n.d). Available at: https://prolific.co/.

Google Scholar

Purkiss, D., Allison, A. L., Lorencatto, F., Michie, S., and Miodownik, M. (2022). The big compost experiment: using citizen science to assess the impact and effectiveness of biodegradable and compostable plastics in UK home composting. Front. Sustain. 3:942724. doi: 10.3389/frsus.2022.942724

Crossref Full Text | Google Scholar

RStudio Team (2020). RStudio: integrated development for R : RStudio, PBC.

Google Scholar

Ruggero, F., Gori, R., and Lubello, C. (2019). Methodologies to assess biodegradation of bioplastics during aerobic composting and anaerobic digestion: a review. Waste Manag. Res. 37, 959–975. doi: 10.1177/0734242X19854127

PubMed Abstract | Crossref Full Text | Google Scholar

Seedorff, M., Oleson, J., and McMurray, B. (2019). "Maybe maximal: good enough mixed models optimize power while controlling type I error." Available at: https://osf.io/preprints/psyarxiv/xmhfr

Google Scholar

Sijtsema, S. J., Onwezen, M. C., Reinders, M. J., Dagevos, H., Partanen, A., and Meeusen, M. (2016). Consumer perception of bio-based products—an exploratory study in 5 European countries. NJAS-Wagen. J. Life Sci. 77, 61–69. doi: 10.1016/j.njas.2016.03.007

Crossref Full Text | Google Scholar

Sonderegger, M. (2023). Regression modeling for linguistic data. MA: MIT Press Cambridge.

Google Scholar

Taufik, D., Reinders, M. J., Molenveld, K., and Onwezen, M. C. (2020). The paradox between the environmental appeal of bio-based plastic packaging for consumers and their disposal behaviour. Sci. Total Environ. 705:135820. doi: 10.1016/j.scitotenv.2019.135820

PubMed Abstract | Crossref Full Text | Google Scholar

The Big Compost Experiment. (2020). Available at: www.bigcompostexperiment.org.uk (Accessed November 16, 2020).

Google Scholar

Trudel, R., Argo, J. J., and Meng, M. D. (2016). Trash or recycle? How product distortion leads to categorization error during disposal. Environ. Behav. 48, 966–985. doi: 10.1177/0013916515577635

Crossref Full Text | Google Scholar

Wang, S., Corner, A., and Nicholls, J. (2020). “Britain talks climate: a toolkit for engaging the British public on climate change.” Available at: https://climateoutreach.org/reports/britain-talks-climate/# (Accessed Feb 16, 2020).

Google Scholar

WRAP. (2021). “On-pack labelling and citizen recycling behaviour.” Available at: https://wrap.org.uk/resources/report/pack-labelling-and-citizen-recycling-behaviour#download-file (Accessed April 27, 2023).

Google Scholar