Summary Research background Plastic debris in the environment consists primarily of plastic consumer waste. One of its leading causes is the lack of waste collection systems in developing countries. Actions need to be taken to overcome this issue, and Extended Producer Responsibility (EPR) seems to be an effective solution for encountering plastic waste. Indonesia is the second-largest plastic polluter and is, therefore, a location of interest for implementing EPR systems. EPR is a policy approach in which producers become responsible for the whole life cycle of their product. In Europe, this is a standard tool that makes producers (mostly financially) accountable for the end-of-life stage of their product. EPR can also stimulate design-for-environment: optimizing products to become more reusable or recyclable. EPR consists of many instruments that can be implemented in different ways. Still, little research has been done on which instruments can be effectively applied in developing countries like Indonesia. There are no EPR instruments currently used, little waste management infrastructure exists, and most recycling activities are realized through informal waste collectors. These types of local factors are of great importance when implementing waste management policies like EPR. Two gaps were found in previous literature. First, the effects of individual and combinations of EPR instruments on developing waste management systems have not been researched before. Secondly, simulation studies have not analyzed EPR instruments in combination with contextual factors of the country of interest. Therefore, this thesis tries to answer the following research question. “What are the effects of 3 selected Extended Producer Responsibility instruments on the key actors in the plastic waste system of average cities in Indonesia?” Research approach A design-science research approach is combined with an agent-based model to answer this question, consisting of three parts. First, the Knowledge base was established by desk research. Literature was consulted to find the state of the art of the most critical aspects of the study: plastic waste in Indonesia and EPR. Secondly, the Environment is created by integrating semi-structured interviews with literature to find important factors that make the implementation of EPR interventions in the context of Indonesia more realistic. The third part of the design science research is to design the artifact. A conceptual model was made of the plastic waste system in Indonesia. This model was put into the programming language NetLogo, which can capture agent behavior in complex adaptive systems. Findings The plastic system is described as a complex adaptive socio-technical system, and an actor analysis is done to visualize the relations between the different stakeholders involved. Furthermore, more emphasis is laid on the behavior of specific actors in the system. Based on interviews, the lack of awareness of the effects of (im)proper waste management was found to be an essential factor of waste pollution. The involvement of households to separate their waste was often mentioned as a solution to stimulate less pollution. Furthermore, four aspects that need to be considered when implementing EPR-related policies have been formulated: little existing waste management infrastructure, involvement of the informal sector, involvement of hard 7 to recycle plastics, and compliance. Considering these four factors and the (plastic) product’s life-cycle, three EPR instruments have been chosen to implement in the analysis. 1. Mandatory take-back requirements 2. Advanced disposal fees 3. Awareness-raising campaigns These findings contributed to the conceptualization of the agent-based model. When the base case was established, the three interventions were integrated into the model individually and combined. The effects on the collection and recycling rate and the amount collected by waste pickers were analyzed. Model results When the model was run without any interventions, it became visible that the plastic leakage would increase over time if no measures were taken due to the rising plastic production and consumption. Implementing take-back requirements resulted in extra waste collection vehicles that collect recyclables and residues separately. An increase in waste collection and recycling is visible, but it also harmed the informal waste pickers. They seemed to be able to collect fewer recyclables when the take-back requirements were implemented, which can cause significant socio-economic effects. The effects on the recycling and collection rate (and to a lesser extend on the waste picker’s collection) were highest in areas where households have a high density. Implementing advanced disposal fees (ADF) focuses on the upstream phase of a product as it stimulates to redesign products that their end-of-use phase can be recycled better. This results in more recyclables in household waste. The awareness-raising campaigns contribute to the product's use phase and stimulate awareness amongst communities about the causes and effects of plastic pollution. Implementing these campaigns makes people more willing to separate the recyclables from residual waste. This is important to retrieve more recyclable materials from the waste, which otherwise gets polluted with other (mainly organic) waste streams. The campaigns can best be located in areas based on a low separation percentage of households to achieve the highest results. Repeating campaigns can result in a higher separation percentage, but collecting their waste separately is more effective. Municipal collectors that collect and dump the waste in landfills are discouraging households from separating their waste. Combining campaigns with take-back requirements does not result in higher collection rates than take-back requirements individually. However, it does increase the recycling rate due to the higher quality of the separated waste streams. This indicates that sorting at the household level is more effective in saving recyclables than only sorting different waste streams after it is collected. Combining these interventions also changes the location strategy of the extra collection vehicles – they should be placed where the households separate their waste. Combining all three interventions results in a slightly lower collection rate than implementing take-back requirements alone. Furthermore, the combination increases the amount collected by the informal waste workers. This could be because the ADF results in more recyclables available, and the campaigns result in higher quality materials that waste pickers can collect. Combining the take-back requirements with other interventions thus reduces the adverse effect of the take-back requirements on the informal sector. Lastly, when implementing the interventions in a specific 8 order, the highest results are achieved. First, the awareness-raising campaigns should start, then take-back requirements, and finally, the advanced disposal fees. Discussion This research found some insights for implementing EPR systems. First, the three interventions complement each other in the life-cycle phase. This is visible in the results, as the combination affects multiple life cycle stages and result in different effects than interventions individually. Secondly, the order of implementing interventions can influence the outcome of the results. For example, this thesis found that the communication instrument, awareness-raising campaigns, should be implemented before take-back requirements. Also, advanced disposal fees should be implemented after the take-back requirements. Both can improve the recycling rate, and to a lesser degree, the collection rate. The take-back requirements can significantly improve the collection and recycling rate and seem to be the most effective instrument. However, they also collect in areas where waste pickers work, which causes adverse socio-economic effects for them. This trade-off should be realized and possibly avoided to limit interference with many people’s livelihoods. Implementing multiple interventions like the ADF and awareness campaigns can reduce this effect. EPR is a very new concept in Indonesia. Many citizens are not aware of the plastic problem and that the cause of pollution lies in a lack of waste management facilities. Producers, but also consumers, and governmental organizations need to make this a priority to be able to reduce environmental pollution. Even, or maybe primarily, in places with little formal infrastructure, EPR interventions can provide a step towards a better responsibility division for waste management. Modeling comes with limitations like observer bias, and many assumptions need to be made that can influence the results. For example, the model's innovation adoption level is based on a well-known distribution (Rogers, 1995). Adapting this distribution, however, results in changes in the outcomes of the model. Verification of the model and validation of the results have been conducted to optimize the results, but these limitations should be considered. Conclusions The results of this study increase the knowledge on the effects of EPR in developing countries. Furthermore, it can create more social awareness in local and national organizations to tackle environmental and human health issues. Most optimally, they can be used as policy recommendations to improve plastic waste collection and recycling without harming essential stakeholders. Answering the research question, the effects of the three EPR instruments are the following. Take-back requirements increase collection and recycling rates and reduce the collection of informal waste pickers. Advanced disposal fees increase recyclables in household waste, and awareness-raising campaigns increase the behavior of households to start source sorting. Combining the interventions results in different strategies for locating the collection vehicles. Furthermore, the order of implementation can affect the effectiveness of the results and location strategies. This thesis fills two scientific gaps. First, it analyses single and combined EPR instruments. Secondly, it simulates EPR instruments that can integrate multiple perspectives and enables the evaluation of policy interventions and their trade-offs.