Elisabeth Theodoropoulos
Sabrina Kirschke
Wiebke Walleck
Bodo Philipp- 1Institute of Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany
- 2Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
- 3Center for Interdisciplinary Sustainability Research (ZIN), University of Münster, Münster, Germany
Citizen science (CS) is becoming increasingly important in exploring the disintegration of plastics in the environment and has positive implications for both science and society. However, it is rarely used in microbiological research and especially in exploring the biodegradation of bioplastics. In this proof-of-concept study, a CS approach is applied to investigate the disintegration of bioplastics in home composts in Germany with the aim of (i) searching for microorganisms with the potential to degrade the bioplastic polylactic acid (PLA) and (ii) exploring attitudes and behavior of the participating citizens in this area and how these may be affected by the citizen science project. Our assumption is that domestic composts are so diverse that bacteria capable of degrading PLA under non-industrial conditions may have (already) evolved in respective composts. Over a period of 3 months, 45 citizens carried out a complex scientific experiment on the degradation of PLA in their household composts, which were distributed throughout Germany. These experiments were accompanied by a pre- and post-survey to analyze the impact of the CS project on the participating citizens. Based on the citizens’ observation that the positive control (paper) was degraded in all cases, we demonstrate that a complex biodegradation experiment performed by citizens is feasible. However, the experiment did not lead to the isolation of PLA-degrading microorganisms. The pre-and post-tests of this short-term intervention on attitudes and behavior hardly reveal any effects in the areas of waste management, consumption and bioplastics.
1 Introduction
Plastics are part of our everyday lives, including specific uses such as packaging or carryout bags. At the same time, the production, use and disposal of plastic lead to problems such as littering, finite fossil resources, and increasing greenhouse gas emissions (Beier, 2009; Amobonye et al., 2021; World Wide Fund For Nature, 2022). Although attempts have been made to regulate the use and disposal of plastics, it is difficult to reach binding agreements (Cortat Simonetti Goncalves and Gerbert Faure, 2018; UNEP, 2022; United Nations (UN), 2024). Problem awareness is often lacking, and thus additional data on plastic in the environment may support reaching such a policy agreement to address plastic pollution in the environment (UNEP, 2021; van Emmerik et al., 2023).
Due to the close positive and negative connection of plastic to our everyday life, citizen science (CS) is increasingly common in the field of plastic monitoring (UNEP, 2021). Examples are the monitoring of plastic of potentially highly polluted environmental resources such as freshwater (e.g., Kiessling et al., 2019; van Emmerik et al., 2020; Cook et al., 2021; Liro et al., 2023) and marine waters (Walther et al., 2024). These studies have revealed benefits for plastic researchers, specifically an increase in high quality data on plastics both in temporal and spatial dimensions (Kiessling et al., 2019; van Emmerik et al., 2020; Cook et al., 2021; Liro et al., 2023; Walther et al., 2024). An example is the monitoring of plastic in rivers using apps such as CrowdWater (van Emmerik et al., 2020) or the RIMMEL-project (González-Fernández and Hanke, 2017). Studies have further analyzed effects on the involved citizens including changes in attitudes and behavior related to plastics in the environment (e.g., Kruse et al., 2020; Capdevila et al., 2020; Popa et al., 2022).
But while there is increasing evidence on the positive application of CS in the field of plastic monitoring and their effects, there is little evidence on the application of CS in the field of biodegradable plastics, and the search for microorganisms capable of degrading polylactic acid (PLA). PLA is produced from renewable raw materials and is considered biodegradable, under industrial composting conditions, in particular. While a recent study in the UK suggests that CS can be applied in the field of composting (Purkiss et al., 2022), there is little evidence on (i) the identification of potential new microorganisms capable of decomposing bioplastics under home composting conditions, and (ii) the corresponding impact on the attitudes and behavior of the participating citizens.
This lack of research is problematic for several reasons. First, there is an increasing interest in bioplastics that are produced from renewable resources (bio-based) and that can be degraded by biological systems (biodegradable). Second, PLA is increasingly being applied in various fields, in particular for (short-life) packaging and as fiber for technical textiles, but also in the fields of agriculture and medicine (DeStefano et al., 2020; Europeanbioplastics, 2023; Khouri et al., 2024). Thirdly, the degradability of PLA has been demonstrated based on European standard EN 13432 (Fraunhofer UMSICHT, 2023; Kreutzbruck et al., 2021), which covers industrial composting conditions and does not apply to other uses, such as in agriculture (Musioł et al., 2016). There appears to be a lack of evidence of effective degradation of PLA applied in these sectors, which has led environmental organizations and waste management companies to criticize the use of PLA (e.g., United Nations, 2024; Naturschutzbund Deutschland, 2023; Münster, 2023; Deutsche Umwelthilfe, 2023).
In this context, the wide diversity of citizens’ individual compost piles could serve as ideal space for the search for potential new microorganisms capable of degrading PLA under home composting conditions. Given the general biodegradability of PLA, it appears plausible that evolutionary processes can lead to PLA-degrading microorganisms. In particular, the variety of home composts and their individual treatment increase the likelihood that PLA-degrading microorganisms might have evolved somewhere. A potential scenario would be that the accidental introduction of PLA into home compost for longer periods may have supported such an evolutionary process. Therefore, CS could be employed to enlarge the variable parameters for classical microbial enrichment cultures (Madigan et al., 2012). For some synthetic chemicals such as the plastic PET, the sweetener acesulfame, or the buffering compound TRIS, evolutionary processes leading to their biodegradation have already been described (Joho et al., 2022; Bonatelli et al., 2023; Holert et al., 2024). Given the fact that PLA is a homo-polyester of lactate, a very abundant natural compound, which can be degraded by many environmental bacteria, and that numerous bacteria produce esterases (Sayali et al., 2013), the probability for the evolution of a PLA-degrading microorganism appears high.
However, it should be noted that using citizen science to investigate the disintegrate of plastics in the environment – such as their biodegradability – raises sensitive methodological challenges. Due to the decentralized and uncontrolled nature of home composting, such studies cannot meet the standards or rigor of material science. The results should therefore be regarded as indicative rather than definitive, not generalizable, and not equivalent to those obtained under standardized laboratory or industrial composting conditions.
Furthermore, it is important to clarify preliminarily that not all biodegradable plastic products are compatible with home composting. Home composting typically operates at lower and more variable temperatures, with less controlled aeration and microbial activity, compared to the high-temperature, highly controlled conditions of industrial composting facilities. Therefore, even if materials are certified as compostable under EN 13432, they may not degrade effectively in home composting systems unless the evolutionary processes described above might have occurred.
Against this background, the goal of this research is to develop and test a concept for a CS project to search for microorganisms that may be able to degrade PLA in home composts. This includes two sub-goals: First, we aim to search for potential new decomposers of the bioplastic PLA in household compost. Second, we aim to explore the effects of this short-term CS project in the field of plastic monitoring on the participating citizens. Accordingly, this study attempts to answer the following research questions: Can potential new decomposing microorganisms for the bioplastic PLA be found in one or more of the participants’ home composts? Has there been an educational effect of the Citizen Science activity, including a change in attitudes and behaviors towards bioplastics and general environmental aspects of citizens participating in this study?
To address these questions, we present a proof-of-concept study of a CS approach to search for potential new microbial degraders of bioplastics under home composting conditions. The study mainly took place in the Münster region in Germany and involved 45 citizens with 50 compost heaps, taking part in a 12 week-long experiment between April and July in 2023. The CS project was accompanied by a pre- and post-test questionnaire to explore the effects of this short-term intervention on attitudes and behavior towards bioplastics and related aspects such as waste management and consumption. In sum, this interdisciplinary approach including natural and social science analysis should reveal if such a CS approach is feasible and how it may be adapted in the future.
2 CS study design and methods
The section describes the citizen-based study design to monitor the degradation of bioplastics in home composts as well as the specific methodology used to conduct this study, including the scientific, experimental research methods for the search for potential new microbial degraders of bioplastics, and the social science, non-experimental research methods.
2.1 CS study design
2.1.1 Project context and aims
The research was carried out within the CS project KompoBioPlast@Home (Universität Münster, 2023) - a project that focused both on the search for potential new microbial degraders of bioplastics (especially PLA) in home composts and on the impact of CS activities on the participating citizens. The main goal of the project was that participating citizens incubate PLA samples in their compost and, thus, contribute to research into microorganisms that can degrade bioplastics. The project was, thus, based on a contributory understanding of citizens as ‘the collection and analysis of data relating to the natural world by members of the general public’ (Oxford English Dictionary, 2014). In addition to pure science-oriented CS projects, KompoBioPlast@Home, however, also aimed at understanding potential effects of the CS activities on the participating citizens with regard to attitudes and behavior related to the topics of composting and connected fields.
2.1.2 Study site and participant recruitment
The actual study took place in Germany, with a total of 50 compost heaps in 17 different study sites (see Figure 1). While study sites were distributed across Germany, there was a bias towards Western Germany and the city of Münster in particular. This goes back to the location of the project lead at the University of Münster and respective recruitment strategies.
Figure 1. Map showing the distribution of participants and respective study sites across Germany.
In order to recruit participants, a self-generating sample was drawn by means of random selection. This means that advertisements for the project were published, and the participants were able to take part in the survey out of their own interest, but on the condition that they owned a compost heap.
The project was mainly advertised using a flyer via various media (see flyer in Supplementary Material S1; in German only). First, university channels of the University of Münster were used, such as the Research Transfer Office (Arbeitsstelle Forschungstransfer or AFO), the Centre for Interdisciplinary Sustainability Research (Zentrum für Interdisziplinäre Nachhaltigkeitsforschung or ZIN), Communications and Public Relations Office, and the participatory research project of Münster university “Ask Sophie!” (“Frag Sophie!”). These multipliers placed the project on their websites, disseminated it via their social media channels, posted it at 41 locations within the university with the help of a poster distributor and also disseminated it within the university via digital steles. Second, specific locations and groups were contacted where compost heap owners were expected: The flyer was sent to 18 allotment garden chairmen in Münster, with a request for distribution, and posted in 10 organic supermarkets in Münster. In addition, the project was presented at the Compost Festival 2022 in Münster (Kompost Festival, 2022). People interested in the project were able to sign up to a mailing list and were then informed and invited when the project started. Although the project was mainly advertised in Münster, word of mouth also helped to acquire participants from outside Münsterland.
As a result of the recruitment strategy, a total of 50 sample batches were distributed. However, as some participants took several batches with them because they have several composts, there were 45 participants at the start of the project.
2.1.3 Study period and process
Using the CS approach, a total of 50 sample batches of bioplastic and their respective positive and negative controls were incubated for 12 weeks (from the beginning of April to the end of June 2023) in the various compost heaps distributed throughout Germany. After the introductory event (31 March 2023) and the start of the project in early April 2023, the 45 participating citizens (compost owners) were able to monitor the potential degradation of PLA in their home composts over a period of 12 weeks. After 4, 8, and 12 weeks, the participants checked the samples for degradation that had taken place. Participants were reminded of the three deadlines by email, and the summarized results of these interim checks were sent to the participants and published on the project website. The samples that returned after 12 weeks were then analyzed for polymer degradation in the laboratory. At a final event on 11 August 2023, the collected results were presented to the participants, and there was an opportunity for exchange and discussion.
A quantitative online survey in a pre-post-test design was conducted among the participants of the CS project to investigate the influence of participation on attitudes and behavior on the topics of waste systems, consumer behavior, and bioplastics, in particular. An approximately 4-week period from 28 March 2023 to 23 April 2023 was selected as the period for the pre-test survey. The post-test survey took place during the summer holidays from 22 June 2023 to 28 July 2023 and was therefore approximately 1 week longer than the pre-test.
2.2 Scientific, experimental research methods
2.2.1 Sample preparation
In total, each participant received a batch of five samples. Two of these consisted of PLA, one of which was a thinner PLA polymer (mulch film) and the other a thicker PLA polymer (lid of a sushi box). The mulch film sample is advertised as “dissolves independently in the soil”. These samples were used as “baits” to gather microorganisms potentially able to decompose PLA. Natural cellulose polymers in the form of uncoated wood-free (UWF) paper and a synthetic polymer film, which was claimed to be home compostable, served as positive controls. Cellulose is biodegradable (Béguin and Aubert, 1994). High density polyethylene polymers (HDPE) served as a negative control. Polyethylene can only be degraded very slowly, if at all (Chamas et al., 2020). The respective samples were clamped in slide frames (Supplier: reflecta GmbH), which were all attached to each other (see Figure 2). The setup was tested in a 3-month preliminary trial (December 2022 - March 2023) in five different composts.
Figure 2. Sample batch that each participant received at the start of the project. Papier: uncoated wood-free (UWF) paper positive control; K+: positive control: polymer film; PLA1: PLA mulch film; PLA2: PLA sushi box; K-: negative control: HDPE.
UWF Paper, as a positive control, is highly permissive due to its rapid disintegration when wet, which may overestimate biodegradation. The procurement of a synthetic but biodegradable positive control was challenging. Despite several attempts to contact manufacturers with biodegradable plastic products in their range, cooperation was ultimately not possible. This was because some manufacturers had not responded or had decided not to cooperate. As a result, a film was purchased that was advertised as certified for home composting without any further information about the certification. As the procurement of the material proved to be difficult and therefore took longer, the degradability could not be verified in the pretest of the experiment. HDPE, as a negative control, is extremely resistant to biodegradation, but minor abiotic changes or biofilm formation can occur without true degradation. For PLA, degradation rates may vary with thickness, crystallinity, and environmental conditions; thin films degrade faster than thick items, and results may not be transferable to all PLA products (Mat Yasin et al., 2022). Further information about the material is provided in the Appendix (see Supplementary Material S2).
2.2.2 Sample incubation in compost
The samples were placed in protective mesh bags (manufacturer: Anlaufs-Fruchtschutz24). The mesh density of about 500 µm is able to protect the samples from coarse, solid material in the compost, such as branches, but bacteria and other microorganisms with their characteristic sizes of 1–100 µm can still pass through the mesh and reach the samples. Nevertheless, an impact on biodegradation rate cannot be ruled out. The samples were then buried in the compost heap at a depth of around 50 cm. The instructions for incubating the samples in the compost heap were given to the participants in a manual (see manual in Supplementary Material S3; in German only).
The participants then filled out a start protocol, which they used to provide information about their compost heap (e.g., size, type of composting, composted material; see start protocol in Supplementary Material S4). The information can be used to characterize the compost heap. If the PLA sample is degraded in this compost, the data are relevant to derive appropriate degradation conditions. The protocol consisted of only 11 questions, some of which could be answered very briefly. This was so as not to overwhelm the participants with too many questions at the beginning. The start protocol was made available via the SoSciSurvey survey tool.
After 4, 8, and 12 weeks, the samples were taken out of the compost and photographed by the participants. Using a test protocol, the participants were asked for current information about their compost (see test protocol in Supplementary Material S5). Further, they had to sort the samples according to decomposition if this had taken place. Rank one meant that the sample had degraded the best by then. If no signs of possible degradation were visible in several samples, these samples were not to be assigned a rank. After four and 8 weeks, the samples were immediately incubated in the compost again, as described at the beginning. After 12 weeks, the trial period ended, and the participants were asked to send the samples to the Institute of Molecular Microbiology and Biotechnology for further analysis.
2.2.3 Sample analysis
Recovered samples were first checked for degradation under a stereomicroscope SMZ745T (Nikon). Samples with holes were sub-cultivated on agar plates filled with a solid cultivation medium (medium B; Jagmann et al., 2010; see material in Supplementary Material S2) containing a piece of the respective polymer as carbon food source. The agar plates were sealed with a laboratory cling-film to retain moisture, incubated at 37 °C and regularly checked for microbial growth and the formation of holes in the polymer.
As one sample showed interesting microbial growth on the plate after 4 weeks, these microorganisms were further sub-cultivated with PLA as a food source. This was done with the aim of isolating colonies that could feed on PLA and then identifying the microorganisms. For sub-cultivation, some material from the microorganisms was transferred to another agar plate with medium B and a fresh piece of PLA mulch film (sample PLA1) using an inoculation loop under sterile conditions. The PLA mulch film was previously scored crosswise in the center to increase the contact surface for the microorganisms. The transferred material of the microorganisms was spread over the scored area on the new film and on the edge of the new film. This new plate was also incubated at 37 °C.
2.3 Social science, non-experimental research methods
2.3.1 Survey goal and design
The main aim of the social science part was to investigate whether and, if so, to what extent the participants’ attitudes and behavior changed during the course of the CS project. We also investigated whether there were differences in attitudes and behavior among the participants in relation to gender and age. In addition, the survey addressed knowledge levels of participants in the pre- and post-test. The respective results are, however, excluded from this research due to low comparability.
To address the main questions, both a pre- and a post-test survey was designed and circulated across all participants in the CS project. The pre-/post-test design is a standard approach to understand the effect of interventions (such as a CS project) on the respective participants.
Survey categories were based on literature in the field of CS and the thematic area of the research (Phillips et al., 2012; Stepenuck and Green, 2015; Phillips et al., 2018; Schäfer et al., 2020; Rambonnet et al., 2023). The survey was then discussed and revised within the team of authors. In addition, the survey was pre-tested by both natural and social scientists to account for the most different types of disciplinary backgrounds. This pre-test was implemented using the online platform SoSciSurvey, and respected feedback was integrated in the final version accordingly.
The survey included three parts. Part 1 included demographic data of the participants (e.g., age, gender). This served the analysis of the relationships between demographic information and the results on attitudes and behavior.
Part 2 of the survey asked about the participants’ attitudes and behavior towards the waste system, consumption, and bioplastics, in particular. Participants were able to rate closed statements on these topics using a four-point numerical scale indicating low to high agreement (1: strongly disagree, 2: somewhat disagree, 3: somewhat agree, 4: strongly agree). In addition, the option “no response” was available for each statement. These two sub-areas did not differ in the pre- and post-version of the questionnaire in order to be able to detect potential changes in attitudes and behavior in these two moments in time.
Part 3 consisted of closed knowledge questions on the same topics. Pre-formulated sentences were presented as answer options (single choice questions). Just as for part 2, there was the option of not giving a response for each question. Once the questions were answered by the participants, the questions were resolved to provide direct feedback to the participants, adding a playful element to the survey. This section differed in the pre- and post-version in order to rule out any unwanted influence, specifically by learning the correct answer in the pre-version. Therefore, no direct comparability of the results from the pre- and post-test is given.
The survey included questions and statements which in the following are referred to as items. In addition, the survey provided short information texts in order to introduce the topic when required. Thus, explicit prior knowledge on the part of the participants was not necessary. The information texts also served to ensure a standardized understanding of terminology. The complete questionnaire (pre- and post-test) can be found in Supplementary Material S6.
2.3.2 Survey circulation and response rate
The web-based survey tool SoSciSurvey was used to create the questionnaire and collect the data. All 45 participants were asked to complete both the pre- and the post-test survey. While pre-/post-testing is an acknowledged approach, it also comes with potential risks such as a low response rate at the stage of post-testing. To this end, the actual survey included playful elements (see knowledge questions), and participation was incentivized by a lottery during survey calculation to attract as many participants as possible to complete the questionnaires of the accompanying study.
As a result, 37 out of 45 participants answered the pre-test survey (response rate = 82,2%) and 21 out of 45 participants answered the post-test (response rate = 46,7%). Thus, a total of n = 20 participants completed both the pre- and post-test questionnaires, and their data were used for the analysis, as this ensured comparability of the results of both surveys.
2.3.3 Data analysis
The analysis of survey data was carried out using Excel (Microsoft® Excel® für Microsoft 365 MSO (Version 2411 Build 16.0.18227.20082) 64 Bit) and the statistical software R (version 4.3.1. Ink.). The analysis included basic descriptive statistics as well as correlation analysis, depending on the research question.
All data were analyzed on the basis of basic descriptive statistics. For the data on the attitude and behavior items (part 2), the percentage distribution of the answers, as well as the median, the lower and the upper quartiles for pre- and post-tests were calculated (see results in Supplementary Material S7). For the data on the knowledge items (part 3), the percentages of correct answers were calculated for the pre- and post-test (see results in Supplementary Material S8).
In order to determine whether participation in the project had an influence on attitudes and behavior of the participants, the Mann-Whitney U-test was performed (see results in Supplementary Material S9). We tested here whether there was a significant difference between the results of the pre-test and those of the post-test. A result was rated as significant if the p-value was less than the significance level of 0.05. In addition, boxplots are shown for those items where the difference between the medians of the pre-test and the post-test is ≥1.
In order to analyze relationships between gender and the individual items on attitudes and behavior, the Mann-Whitney U-test was performed for all female (60%) and male (35%) results of both the pre- and the post-test (one of the 20 participants did identify as non-binary). We tested here whether there was a significant difference between the results of the female and of the male participants. A result was categorized as significant if the p-value was less than the significance level of 0.05 (see results in Supplementary Material S10).
In order to examine relationships between age and the individual items on attitudes and behavior, the rank correlation according to Spearman was calculated for all results of both the pre-test and the post-test. A result was categorized as significant if the p-value was less than the significance level of 0.05 (see results in Supplementary Material S11).
3 Results
3.1 Results of the scientific experiment on the degradation of PLA
In order to search for potential new microbial degraders of bioplastics in home compost, a total of 50 sample batches were distributed to participants in the CS project. In addition to the two PLA samples (PLA1: thin, black mulch film; PLA2: thick, transparent sushi box), these batches each contained two positive controls (paper: cellulose polymers; K+: synthetic polymer film claimed as being home compostable) and one negative control (K-: HDPE film). A total of 28 sample batches were sent back to our institute at the University of Münster at the end of the 12-week composting period.
The UWF paper positive control (cellulose polymers) was degraded in the composts of all participants (see Figure 3). The bitten appearance of the degraded papers indicated that its disintegration was not caused by wetting only and rather resembled degradation of cellulose filters by bacterial pure cultures (Gao et al., 2020).
Figure 3. Representative images of the degradation of the uncoated wood-free (UWF) paper (German: Papier) positive control over time: Weeks 0–12.
In contrast, the synthetic polymer film claimed to be home compostable did not degrade. Four of the recovered samples initially looked promising, so they were subject to sub-culturing of potential degrading microorganisms. However, no further interesting microbial growth or degradation could be detected there.
As expected, the HDPE negative control also showed no degradation. Two of the samples recovered were subject to sub-culturing due to signs of degradation (small holes in the material). However, no degradation could be detected in the further course.
Five of the recovered PLA1 samples and one of the recovered PLA2 samples looked promising as small holes could be detected in the PLA material. Therefore, these samples were subject to sub-culturing of potential PLA-degrading microorganisms on solid media in petri dishes. Of these, the PLA1 sample from sample batch no. 30 showed interesting microbial growth after 4 weeks of incubation on the agar plate. At one point where holes appeared on the film, cloud-like microbial growth could be recognized above the holes, hinting to bacterial colonies or a fungus (see Figure 4). After a next sub-cultivation step microbial growth but no new holes could be detected on the new plate. In the other PLA samples that were transferred to agar plates, however, no signs of degradation could be detected.
Figure 4. PLA1 sample of sample batch no. 30 after 4 weeks on the agar plate shows colonies of microorganisms on the sample and underlying holes in the film (mulch film, manufacturer: Folien Lücke GmbH).
Microscopic analysis of the microorganisms of the PLA1 sample from batch no. 30 suggested that the colonies were formed by myxobacteria as indicated by the morphology of the respective fruiting bodies, vegetative cells and spores (Shimkets et al., 2006). However, as attempts to transfer this PLA-degrading activity failed, a further identification of the organism with genetic methods was not pursued.
3.2 Results of the social science survey
3.2.1 Demographic data
The majority of participants were born between 1959 and 1998 (80%) and are female (60%) (see Figure 5).
Figure 5. Distribution of the demographic data of the participants: Age and gender (f: female, m: male, d: diverse).
3.2.2 Pre- and post-test descriptive results
3.2.2.1 Attitudes towards waste system
The majority of respondents considered it important that comprehensive advice is offered, for example, by the regional waste management company, on how to dispose of their waste in an environmentally friendly manner (see E 1.1: pre-test median: 3, post-test median: 4). The respondents were also rather satisfied with the reliability of their regional waste management company (see E 1.2: pre-test median: 3, post-test median: 3). The majority in the pre-test and all participants in the post-test did not think that waste avoidance is superfluous because modern recycling plants could effectively recycle raw materials (see E 1.3: pre-test median: 1, post-test median: 1).
3.2.2.2 Behavior related to waste system
The majority of participants stated that they consistently separate waste (see V 1.1: pre-test median: 3.5, post-test median: 4). All participants also stated that they always dispose of hazardous waste and recyclables properly (see V 1.2: pre-test median: 4, post-test median: 4). Almost the majority tended not to pick up litter lying around on the street and dispose of it in the nearest rubbish bin (see V 1.3: pre-test median: 2, post-test median: 2).
3.2.2.3 Attitudes towards consumption
The majority of participants believed that they, as citizens, can make a significant contribution to environmental protection through their purchasing and consumption behavior (see E 2.1: pre-test median: 4, post-test median: 4). All participants also believed that retailers and industry must ensure that there is less packaging waste (see E 2.2: pre-test median: 4, post-test median: 4). The participants also stated that they would be more inclined to pay higher individual prices for products if they were less harmful to the environment (see E 2.3: pre-test median: 3.5, post-test median: 3).
3.2.2.4 Behavior related to consumption
The majority in the pre-test and half of the participants in the post-test stated that they do not tend to buy clothing via online shipping (see V 2.1: pre-test median: 2, post-test median: 2.5). Almost the majority stated that they also do not tend to buy clothes second-hand (see V 2.2: pre-test median: 2, post-test median: 2). The majority of participants stated that they do not tend to buy pre-packaged fruit and vegetables (see V 2.3: pre-test median: 2, post-test median: 2). The majority also tended to try to avoid waste through conscious consumer behavior (see V 2.4: pre-test median: 3, post-test median: 3).
3.2.2.5 Attitudes towards bioplastics
The majority of participants in the pre-test and the majority in the post-test considered bioplastics to be more ethically acceptable than conventional plastics (see E 3.1: pre-test median: 4, post-test median: 3). Similarly, respondents assessed bioplastics in private households as being useful (see E 3.2: pre-test median: 3.5, post-test median: 3.5). The majority of respondents stated that they are more willing to pay more money for bioplastics (see E 3.3: pre-test median: 3, post-test median: 3).
3.2.2.6 Behavior related to bioplastics
The majority of participants did not tend to look at the packaging information of products to find out whether they are made from bioplastics (see V 3.1: pre-test median: 2, post-test median: 2). However, the majority said that they are more likely to choose a product made from bioplastics if it has the same quality and durability as a product made from conventional plastic (see V 3.2: pre-test median: 3, post-test median: 3). The vast majority stated that they do not actively look for products made from bioplastics (see V 3.3: pre-test median: 1, post-test median: 2).
3.2.3 Gender and age specific results
With regard to attitude, no significant difference was found in the pre- and post-test data in relation to gender and age.
With regard to behavior, significant differences were found in the pre- and post-test data in relation to age. For the subject area of bioplastics, the analysis revealed a medium correlation for the results of the pre-test: Younger participants were more likely to choose the bioplastic product if it has the same quality and durability as a conventional plastic product than older participants (see V 3.2: correlation coefficient: 0.49, p-value: 0.03). For the area of consumption, the analysis showed one high correlation for the results of the post-test: Younger participants were more likely to buy clothes online than older participants (see V 2.1: correlation coefficient: 0.54, p-value: 0.01). For the same subject area, one medium correlation was determined for the results of the post-test: Younger participants were more likely to buy clothes second-hand than older participants (see V 2.2: correlation coefficient: 0.49, p-value: 0.03).
3.2.4 Change in relation to the waste system, consumption and bioplastics
Pre- and post-test data concerning the attitude and the behavior of the participants were generally very similar. The Mann-Whitney U-test further revealed that no significant difference was found for any of the items between the results of the pre- and post-test. This suggests that participants’ attitudes and behavior towards the waste system, consumption and bioplastics were not influenced by their participation in the CS project, or at least not to a significantly measurable extent.
Although the results are very similar, three interesting changes will be addressed in more detail, two in attitudes and one in behavior. The following boxplots show items for which the difference between the medians of the pre-test and post-test is ≥1.
First, there is a tendency that participants were more interested in comprehensive advice, e.g., from the regional waste disposal company, on the environmentally friendly disposal of their waste after the end of the experiment than before the experiment (see E 1.1 in Figure 6).
Figure 6. Boxplot of E 1.1: “It is important to me that I am offered comprehensive advice, for example, by the regional waste management company, on how to dispose of my waste in an environmentally friendly way.” The boxplot shows the distribution of the data of the pre (blue)- and post (grey)-test results of the online survey among the participants of the Citizen Science project (n = 20) on the attitude questions about the waste system (1 = does not apply, 4 = applies, 0 = no answer).
Also, there is a slightly more critical attitude towards bioplastics among the respondents, but this is not significant. At the end of the experiment, the participants still saw bioplastics as more morally acceptable than conventional plastics, but they were slightly less convinced of bioplastics than before the experiment (see E 3.1 in Figure 7).
Figure 7. Boxplot of E 3.1: “Bioplastics are more morally acceptable than conventional plastics.” The boxplot shows the distribution of the data of the pre (blue)- and post (grey)-test results of the online survey among the participants of the Citizen Science project (n = 20) on the attitude questions on bioplastics (1 = does not apply, 4 = applies, 0 = no answer).
Before and after the experiment, the majority of participants did not actively search for products made from bioplastics. However, there was a tendency for participants to be slightly more interested in actively searching for products made from bioplastics after the end of the experiment (see V 3.3 in Figure 8).
Figure 8. Boxplot of V 3.3: “I actively search for products made from bioplastics.” The boxplot shows the distribution of the data of the pre (blue)- and post (grey)-test results of the online survey among the participants of the Citizen Science project (n = 20) on the behavioral questions on bioplastics (1 = does not apply, 4 = applies, 0 = no answer).
4 Discussion
4.1 Contribution to research state of the art
The CS project successfully demonstrated the feasibility of involving citizens in the search for potential new microbial degraders of bioplastics, a complex and socially relevant issue aligned with Sustainable Development Goal 14 (Vereinte Nationen, 2022). The participants, in fact, delivered high quality data as evidenced by the protocols and samples returned by the citizens. For example, the positive UWF paper controls were degraded/composted as expected for all participants. Thus, the KompoBioPlast@Home project underscores the value of CS in undertaking advanced scientific experiments in the field of plastics.
This study further aimed (i) to identify potential new microorganisms capable of decomposing the bioplastic PLA in household compost, and (ii) to evaluate the effects of this short-term CS on the participating citizens.
In terms of the first goal, the broad participation and the diverse compost heap setups increased the likelihood of identifying microorganisms capable of degrading PLA. Nevertheless, the results show that biological degradation under non-industrial composting conditions is rather unlikely, at least within the analyzed period of 3 months. This result is in agreement with current literature on PLA-degradation (Shalem et al., 2024). Nevertheless, one sample (PLA1) showed the formation of holes in the PLA1 film with interesting cloud-like microbial growth above it when analyzed further in the laboratory. This indicates a degradation of the film by microorganisms. A final identification of the microorganisms was not successful, but we obtained clear indications that they belonged to the myxobacteria that are known for their potential to degrade natural polymers such as cellulose and chitin (Shimkets et al., 2006). Generally, myxobacteria are also known to produce various hydrolytic enzymes for esters such as lipases (Moraleda-Muñoz and Shimkets, 2007). It, thus, appears plausible that they might be candidates for evolving enzymes for degrading the polyester PLA. For a clear identification of the microorganisms a 16S rDNA sequencing could be done in follow up studies of this research. However, since the degradation process was no longer observed during sub-cultivation, the isolate had presumably either lost this ability or other supporting bacteria from the original compost had been lost. As UWF paper as a positive control was completely degraded in all cases as expected, it appears unlikely that the participants incubated their samples in an incorrect manner that would not allow composting processes. The fact that no biodegradation of polyethylene, which served as negative control, was observed is in line with the current perception that such hydrocarbon polymers are not biodegradable (Jendrossek, 2024) and that the incubation method was suitable to prevent mechanical damage of the plastic samples by wooden contents (e.g., branches) within the compost. While the PLA sushi packaging was only marketed as “fully biodegradable” it was therefore not expected to decompose at the lower temperatures typical of home composting. The results for the PLA mulch film - advertised as “dissolving independently in the soil” - and the polymer film labelled as “home compostable” raise, however, questions to which extent such product descriptions and the norm DIN EN 134232 can be applied to home composting conditions. At the same time, caution is required to avoid over-interpreting CS results as equivalent to accredited laboratory or industrial composting tests. It is therefore important to emphasise that, while the results of this study point to real-world experiences in home composting, they do not provide definitive evidence of the performance of certified compostable plastics under standardized conditions.
In terms of the second goal, the study suggests that citizens that are willing to participate in such a citizen science study generally have environment-friendly attitudes and behavior. The pre-/post-test survey further suggests that short-term CS activities in the field of composting only have limited effects on the participating citizens. This is not entirely unexpected, as the CS literature indicates that significant educational or behavioral change often requires longer-term engagement (Price and Lee, 2013). However, also short-term CS studies report positive effects on citizen outcomes, therefore testing the effects of short projects seems valuable as well (Kirschke et al., 2023). It is also known that negative results in research are rarely published, thus previous studies on CS projects could give a distorted impression, to the extent that changes in attitudes and behavior occur more or less frequently in the studies than is actually the case (Peter et al., 2019; Ganzevoort and van den Born, 2021). Limited effects of short-term interventions could also go back to the actual citizens involved in the study. As the participants already had a compost and showed their interest in respective topics through their voluntary participation in this project, they may have been better informed about waste systems, consumption, and bioplastics than the average population at the start of the experiment, with respective effects on their attitudes and behavior. Also, evidence of change is difficult to quantify. It can therefore not be ruled out that individual participants with already high levels of knowledge and environment-positive attitudes and behavior may have experienced a change in their attitude or behavior which however does not show in a different rating on a 1-4 scale. The results should therefore be reflected upon and predominantly considered in the context of the group surveyed.
4.2 Methodological questions, future research and practice
The proof-of-concept study also faced a number of methodological challenges which may be of relevance for future studies.
First, while the involvement of participants yielded valuable samples and insights, challenges arose, particularly with acquiring a reliable synthetic, biodegradable positive control. The study identified issues relating to the fact that materials purchased and marketed as being home compostable did not degrade as expected. The unclear characterization of the materials used, coupled with the lack of information regarding their actual certification for home compostability, makes it difficult to interpret the results. These results are consistent with those obtained from similar British initiatives on CS, which found that a significant proportion of so-called home compostable plastics did not degrade completely (Purkiss et al., 2022). Overall, these difficulties highlight that citizen science studies must also carefully vet manufacturers’ claims and verify that products truly meet the specification requirements outlined in ISO/EN standards. In the complex and fast-growing biodegradable materials market, such scrutiny is indispensable, as consumers are at high risk of being misled by inaccurate or unsubstantiated information. Furthermore, not all citizens provided information on temperature, so this data could not be included in our study. In addition, it cannot be ruled out that the temporary removal of samples from the piles for examination had a delaying effect on the degradation processes.
Second, and in terms of questionnaire design, further methodological enhancements could reduce bias and obtain more generalized insights: Including a control group could refine the evaluation of changes attributed to participation. A larger number of participants could contribute to a greater significance of the results. Moreover, revising the recruitment mechanisms addressing the sampling strategy could help ensure broader representation beyond those already inclined towards sustainable practices. In addition, extending the duration of the study would allow for a more in-depth investigation of changes in attitudes and behavior. The project also revealed the necessity for better alignment between questionnaire content and project themes. Revising survey items to reflect specific project components more accurately may allow for clearer measurements of participant learning outcomes.
Also, while the CS approach was beneficial to the researcher as high quality data were delivered and as the high number and diversity of the compost heaps increased the probability of identifying a new PLA-degrading microorganism, it is also important to bear in mind that projects without remarkable success (the majority of the samples did not show any clear signs of PLA degradation) may lead to disillusionment among participants if expectations are not managed appropriately from the outset.
In terms of future research, a significant operational lesson involves the challenge of sourcing verifiable biodegradable materials. The lack of response from manufacturers and subsequent findings on the non-degradation of the film advertised as home compostable suggests a pressing need for greater transparency and consistency in product certifications. Developing partnerships with manufacturers willing to collaborate in research could enhance access to rigorously tested materials, fostering more robust and reproducible results. In addition, future experiments should consider additional temperature analysis, in particular. Based on our experience in the current experiment, citizens should be provided with standardized equipment as well as training of temperature measurement procedures.
From a public engagement perspective, it is important to ensure that participants derive value from the experience, beyond their contribution to data collection. Although the slight shift in the project towards more critical perspectives on bioplastics is not statistically significant, it does indicate a possible disappointment if the hoped-for results fail to materialize. To counteract this, transparent and open communication is important so that expectations are as realistic as possible.
Lastly, while negative or neutral results can be discouraging, sharing them is vital for the credibility and transparency of CS. The project’s outcomes underscore the need for publishing comprehensive results, including non-significant or unexpected findings, to avoid skewing perceptions in the field. This ensures that CS is seen not only as a tool for data collection but as an authentic educational and awareness-raising initiative.
5 Conclusion
CS is a growing field in plastics research, yet rather uncommon in the field of microbiological research and in the context of composting. This study has shown that a CS-based approach is not only possible but highly beneficial for answering the scientific research question as the CS approach allowed for implementing experiments in a diversity of context conditions and because citizens provided high quality data. This resulted in new knowledge for the search for potential new decomposers of bioplastics under natural, home composting conditions which would otherwise be difficult to obtain. While these scientific results are promising, the short-term project could not detect significant effects on participants’ attitudes and behavior. The respective social science study instead revealed potentially relevant results including gender- and age-related differences in behavior, as well as non-intended side effects of research activities. Overall, the study has substantiated a known fact in CS research, that communication is key for securing project success. In our case, communication did not only secure the high scientific quality of the data but also helped to recruit and motivate citizens to continue their CS engagement and was judged key to handle side effects of the scientific activities on citizens. Future studies should therefore put special emphasis on communication in this rather complex field of research.
Data availability statement
The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.
Ethics statement
Participation in the citizen science project was completely voluntary. Ethical review and approval were not required for the study on human participants in accordance with local legislation and institutional requirements. The participants were informed by email before the start of the project that an anonymous questionnaire was part of the project. Their active participation was taken as consent.
Author contributions
ET: Conceptualization, Investigation, Methodology, Formal analysis, Data curation, Writing – review and editing, Writing – original draft. SK: Conceptualization, Methodology, Writing – review and editing, Writing – original draft. WW: Conceptualization, Supervision, Writing – review and editing, Writing – original draft. BP: Conceptualization, Project administration, Resources, Supervision, Writing – review and editing, Writing – original draft.
Funding
The author(s) declared that financial support was received for this work and/or its publication. This project was funded by the University of Münster.
Acknowledgements
We would like to thank the citizens involved in the project, because without their interest and work, the project would not have been possible! We would also like to thank Stephan Grote, expert advisor for allotment gardens and employee of NABU - Naturschutzbund Deutschland e. V., who also supported us with the preliminary test of the experiment. Finally, we would like to thank the Research Transfer Centre of the University of Münster, and, in particular, Marc Stallony, for their support.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declared that generative AI was not used in the creation of this manuscript.
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Supplementary material
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fenvs.2025.1676682/full#supplementary-material
References
Amobonye, A., Bhagwat, P., Singh, S., and Pillai, S. (2021). Plastic biodegradation: frontline microbes and their enzymes. Sci. Total Environment 759, 143536. doi:10.1016/j.scitotenv.2020.143536
Béguin, P., and Aubert, J. P. (1994). The biological degradation of cellulose. FEMS Microbiology Reviews 13 (1), 25–58. doi:10.1111/j.1574-6976.1994.tb00033.x
Beier, W. (2009). Biologisch abbaubare kunststoffe/umweltbundesamt. Available online at: https://www.umweltbundesamt.de/sites/default/files/medien/publikation/long/3834.pdf (Accessed January 13, 2025).
Bonatelli, M. L., Rohwerder, T., Popp, D., Liu, Y., Akay, C., Schultz, C., et al. (2023). Recently evolved combination of unique sulfatase and amidase genes enables bacterial degradation of the wastewater micropollutant acesulfame worldwide. Front. Microbiol. 14, 1223838. doi:10.3389/fmicb.2023.1223838
Capdevila, A. S. L., Kokimova, A., Ray, S. S., Avellán, T., Kim, J., and Kirschke, S. (2020). Success factors for citizen science projects in water quality monitoring. Sci. Total Environ. 728, 137843. doi:10.1016/j.scitotenv.2020.137843
Chamas, A., Moon, H., Zheng, J., Qiu, Y., Tabassum, T., Jang, J. H., et al. (2020). Degradation rates of plastics in the environment. ACS Sustain. Chem. and Eng. J. 8 (9), 3494–3511. doi:10.1021/acssuschemeng.9b06635
Cook, S., Abolfathi, S., and Gilbert, N. I. (2021). Goals and approaches in the use of citizen science for exploring plastic pollution in freshwater ecosystems: a review. Freshw. Sci. 40 (4), 567–579. doi:10.1086/717227
Cortat Simonetti Goncalves, L., and Gerbert Faure, M. (2018). International law instruments to address the plastic soup. William and Mary Environ. Law Policy Rev. 43, 871. doi:10.2139/ssrn.3405968
DeStefano, V., Khan, S., and Tabada, A. (2020). Applications of PLA in modern medicine. Eng. Regen. 1, 76–87. doi:10.1016/j.engreg.2020.08.002
Deutsche Umwelthilfe, e. V. (2023). Bioplastik bleibt plastik. Available online at: https://www.duh.de/bioplastik/ (Accessed September 20, 2023).
Europeanbioplastics. (2023). Bioplastics market development update 2023. Available online at: https://www.european-bioplastics.org/market/ (Accessed September 8, 2023).
Fraunhofer UMSICHT (2023). Zertifizierung kompostierbarer kunststoffe. Available online at: https://www.umsicht.fraunhofer.de/de/ueber-fraunhofer-umsicht/nachhaltigkeit/nationale-informationsstelle-nachhaltige-kunststoffe/zertifizierung/kompostierbare-kunststoffe.html (Accessed September 8, 2023).
Ganzevoort, W., and van den Born, R. J. G. (2021). Counting bees: learning outcomes from participation in the Dutch national bee survey. Sustainability 13 (9), 4703. doi:10.3390/su13094703
Gao, L., Guan, Z., Gao, P., Zhang, W., Qi, Q., and Lu, X. (2020). Cytophaga hutchinsonii gldN, encoding a core component of the type IX secretion system, is essential for ion assimilation, cellulose degradation, and cell motility. Appl. Environ. Microbiol. 86 (11), e00242–e00320. doi:10.1128/AEM.00242-20
González-Fernández, D., and Hanke, G. (2017). Toward a harmonized approach for monitoring of riverine floating macro litter inputs to the marine environment. Front. Mar. Sci. 4, 86. doi:10.3389/fmars.2017.00086
Holert, J., Borker, A., Nübel, L. L., Daniel, R., Poehlein, A., and Philipp, B. (2024). Bacteria use a catabolic patchwork pathway of apparently recent origin for degradation of the synthetic buffer compound TRIS. ISME J. 18 (1), wrad023. doi:10.1093/ismejo/wrad023
Jagmann, N., Brachvogel, H. P., and Philipp, B. (2010). Parasitic growth of Pseudomonas aeruginosa in co-culture with the chitinolytic bacterium Aeromonas hydrophila. Environ. Microbiol. 12 (6), 1787–1802. doi:10.1111/j.1462-2920.2010.02271.x
Jendrossek, D. (2024). Polyethylene and related hydrocarbon polymers (“plastics”) are not biodegradable. New Biotechnol. 83, 231–238. doi:10.1016/j.nbt.2024.08.503
Joho, Y., Vongsouthi, V., Spence, M. A., Ton, J., Gomez, C., Tan, L. L., et al. (2022). Ancestral sequence reconstruction identifies structural changes underlying the evolution of Ideonella sakaiensis PETase and variants with improved stability and activity. Biochemistry 17 (2), 437–450. doi:10.1021/acs.biochem.2c00323
Khouri, N. G., Bahú, J. O., Blanco-Llamero, C., Severino, P., Concha, V. O. C., and Souto, E. B. (2024). Polylactic acid (PLA): properties, synthesis, and biomedical applications – a review of the literature. J. Mol. Struct. 1309, 138243. doi:10.1016/j.molstruc.2024.138243
Kiessling, T., Knickmeier, K., Kruse, K., Brennecke, D., Nauendorf, A., and Thiel, M. (2019). Plastic pirates sample litter at rivers in Germany – riverside litter and litter sources estimated by schoolchildren. Environ. Pollut. 245, 545–557. doi:10.1016/j.envpol.2018.11.025
Kirschke, S., Bennett, C., Ghazani, A. B., Kirschke, D., Lee, Y., Loghmani Khouzani, S. T., et al. (2023). Design impacts of citizen science. A comparative analysis of water monitoring projects. Front. Environ. Sci. 11, 11–2023. doi:10.3389/fenvs.2023.1186238
Kompost Festival (2022). Das Kompost Festival - die lebendige Kunst der Transformation 16. - 25. Juni 2022, Münster. Available online at: https://kompost.zone/festival-2022/ (Accessed January 13, 2025).
Kreutzbruck, M., Resch, J., Kabasci, S., Ivleva, N. P., Philipp, B., Jongsma, R., et al. (2021). Plastik in der Umwelt. Sachstandspapier zur Bioabbaubarkeit Kunstst. Available online at: https://bmbf-plastik.de/sites/default/files/2021-11/211123_QST7_Sachstandpapier%20Bioabbaubarkeit_Kunststoffe_final.pdf (Accessed September 8, 2023).
Kruse, K., Kiessling, T., Knickmeier, K., Thiel, M., and Parchmann, I. (2020). “Can participation in a citizen science project empower schoolchildren to believe in their ability to act on environmental problems?,” in Advances in chemistry education series, 225–240. doi:10.1039/9781788016087-00225
Liro, M., Zielonka, A., Hajdukiewicz, H., Mikuś, P., Haska, W., Kieniewicz, M., et al. (2023). Litter selfie: a citizen science guide for photorecording macroplastic deposition along Mountain rivers using a smartphone. Water 15 (17), 3116. doi:10.3390/w15173116
Madigan, M., Martinko, J., Stahl, D., and Clark, D. (2012). Brock: biology of microorganisms. 13th ed. Harlow, England: Pearson Education.
Mat Yasin, N., Akkermans, S., and Van Impe, J. F. M. (2022). Enhancing the biodegradation of (bio)plastic through pretreatments: a critical review. Waste Manag. 1 (150), 1–12. doi:10.1016/j.wasman.2022.06.004
Moraleda-Muñoz, A., and Shimkets, L. J. (2007). Lipolytic enzymes in Myxococcus xanthus. J. Bacteriol. 189 (8), 3072–3080. doi:10.1128/jb.01772-06
Münster, U. (2023). KompoBioPlastHome? - citizen-science-projekt zum Abbau vom Bioplastik im Heimkompost. Available online at: https://www.uni-muenster.de/Biologie.IMMB.Philipp/forschung/KompoBioPlastHome.html (Accessed January 13, 2025).
Musioł, M., Sikorska, W., Adamus, G., Janeczek, H., Richert, J., Malinowski, R., et al. (2016). Forensic engineering of advanced polymeric materials. Part III - biodegradation of thermoformed rigid PLA packaging under industrial composting conditions. Waste Manag. 52, 69–76. doi:10.1016/j.wasman.2016.04.016
Naturschutzbund Deutschland, e. V. (2023). Biologisch abbaubare Kunststoffe in der Landwirtschaft- NABU Forderungen zur Anwendung. Available online at: https://www.nabu.de/umwelt-und-ressourcen/ressourcenschonung/kunststoffe-und-bioplastik/30018.html (Accessed September 20, 2023).
Peter, M., Diekötter, T., and Kremer, K. (2019). Participant outcomes of biodiversity citizen science projects: a systematic literature review. Sustainability 11 (10), 2780. doi:10.3390/su11102780
Phillips, T. B., Bonney, R., and Shirk, J. L. (2012). “What is our impact? Toward a unified framework for evaluating outcomes of citizen science participation,” in Citizen science: public participation in environmental research. doi:10.7591/cornell/9780801449116.003.0006
Phillips, T., Porticella, N., Constas, M., and Bonney, R. (2018). A framework for articulating and measuring individual learning outcomes from participation in citizen science. Citiz. Sci. Theory Pract. 3 (2), 3. doi:10.5334/cstp.126
Popa, C. L., Dontu, S. I., Savastru, D., and Carstea, E. M. (2022). Role of citizen scientists in environmental plastic litter research — a systematic review. Sustainability 14 (20), 13265. doi:10.3390/su142013265
Price, C. A., and Lee, H. S. (2013). Changes in participants' scientific attitudes and epistemological beliefs during an astronomical citizen science project. J. Res. Sci. Teach. 50 (7), 773–801. doi:10.1002/tea.21090
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, 3–2022. doi:10.3389/frsus.2022.942724
Rambonnet, L., Reinders, H., and Land-Zandstra, A. (2023). Citizen science against the plastic soup: background, motivation and expectations of volunteers studying plastic pollution on Dutch riverbanks. Res. All 7 (1). doi:10.14324/RFA.07.1.14
Sayali, K., Sadicha, P., and Surekha, S. (2013). Microbial esterases: an overview. Int. J. Curr. Microbiol. App. Sci. 2, 135–146.
Schäfer, T., Kieslinger, B., and Fabian, C. M. (2020). Citizen-based air quality monitoring: the impact on individual citizen scientists and how to leverage the benefits to affect whole regions. Citiz. Sci. Theory Pract. 5 (1), 6. doi:10.5334/cstp.245
Shalem, A., Yehezkeli, O., and Fishman, A. (2024). Enzymatic degradation of polylactic acid (PLA). Appl. Microbiol. Biotechnol. 108 (1), 413. doi:10.1007/s00253-024-13212-4
Shimkets, L. J., Dworkin, M., and Reichenbach, H. (2006). CHAPTER 3.4.3, the myxobacteria. Prokaryotes 7, 31–115. doi:10.1007/0-387-30747-8_3
Stepenuck, K., and Green, L. T. (2015). Individual- and community-level impacts of volunteer environmental monitoring: a synthesis of peer-reviewed literature. Ecol. Soc. 20 (3), 19. doi:10.5751/ES-07329-200319
Universität Münster (2023). KompoBioPlastHome? - Citizen-Science-Projekt zum Abbau vom Bioplastik im Heimkompost. Available online at: https://www.uni-muenster.de/Biologie.IMMB.Philipp/forschung/KompoBioPlastHome.html (Accessed December 16, 2025).
United Nations (UN) (2024). Plastic pollution treaty negotiations adjourn in Busan, to resume next year. Available online at: https://news.un.org/en/story/2024/12/1157646 (Accessed December 4, 2024).
United Nations Environment Programme (UNEP) (2021). From pollution to solution: a global assessment of marine litter and plastic pollution. Available online at: https://www.unep.org/resources/pollution-solution-global-assessment-marine-litter-and-plastic-pollution (Accessed December 4, 2024).
United Nations Environment Programme (UNEP) (2022). 5/14. End plastic pollution: towards an international legally binding instrument. Resolut. Adopted by U. N. Environ. Assembly Available online at: https://digitallibrary.un.org/record/3999257?ln=en&v=pdf (Accessed January 13, 2025).
Van Emmerik, T., Seibert, J., Strobl, B., Etter, S., Den Oudendammer, T., Rutten, M., et al. (2020). Crowd-based observations of riverine macroplastic pollution. Front. Earth Science 8, 8–2020. doi:10.3389/feart.2020.00298
Van Emmerik, T. H., Kirschke, S., Schreyers, L. J., Nath, S., Schmidt, C., and Wendt-Potthoff, K. (2023). Estimating plastic pollution in rivers through harmonized monitoring strategies. Mar. Pollut. Bull. 196, 115503. doi:10.1016/j.marpolbul.2023.115503
Vereinte Nationen (United Nations, UNO) (2022). Agenda 2030 I 17 Ziele für Nachhaltige Entwicklung. SDG 14 Leben unter Wasser. Available online at: https://www.bmz.de/de/agenda-2030/sdg-14 (Accessed September 26, 2023).
Walther, B. A., Pasolini, F., Korez Lupše, Š., and Bergmann, M. (2024). Microplastic detectives: a citizen-science project reveals large variation in meso-and microplastic pollution along German coastlines. Front. Environ. Sci. 12, 12–2024. doi:10.3389/fenvs.2024.1458565
World Wide Fund For Nature (WWF) (2022). Pressestatement zum Ende der ersten Verhandlungsrunde für ein UN-Abkommen gegen Plastikmüll. Available online at: https://www.wwf.de/2022/dezember/pressestatement-zum-ende-der-ersten-verhandlungsrunde-fuer-ein-un-abkommen-gegen-plastikmuell (Accessed September 19, 2023).
Keywords: biological degradation, bioplastic, citizen science, composting, impact, participation, polylactic acid (PLA)
Citation: Theodoropoulos E, Kirschke S, Walleck W and Philipp B (2026) Citizen science in plastic composting: a practical approach to the search for PLA-degrading microorganisms. Front. Environ. Sci. 13:1676682. doi: 10.3389/fenvs.2025.1676682
Received: 30 July 2025; Accepted: 08 December 2025;
Published: 09 January 2026.
Edited by:
Ahmet Erkan Kideys, Middle East Technical University, TürkiyeReviewed by:
Francesco Degli-Innocenti, Novamont S.p.A. - Chimica Vivente per la Qualità della Vita, ItalyRamani Narayan, Michigan State University, United States
Copyright © 2026 Theodoropoulos, Kirschke, Walleck and Philipp. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Elisabeth Theodoropoulos, ZWxpc2FiZXRodGhlb2Rvcm9wb3Vsb3NAZ29vZ2xlbWFpbC5jb20=