Solid Waste Minimisation in New Zealand: A Multi-Methodological Systems Analysis

Solid waste represents a loss of resources and leads to various forms of human and environmental harm. Despite increasing effort being put into waste management solutions, the volume of waste created around the world continues to increase. Waste is commonly perceived to be created when products or packaging are discarded but end-of-life is inevitable for every material that is produced, so the entire lifecycle of products needs to be considered to reduce the harmful effects of solid waste.

The purpose of this research was therefore identified to enrich the collective understanding of why and how waste is created throughout New Zealand. A particular focus was directed towards helping understand the structures and characteristics of the system that lead to consumption and, subsequently, waste generation. Two main research questions were developed to address this:

1. What are the structures and characteristics of the system that lead to solid waste generation?

2. What are the barriers and opportunities to reduce the amount of solid waste generated?

This research adopted a multi-methodology Systems Thinking approach to address these research questions from multiple qualitative and quantitative perspectives. This approach was used to challenge the traditional view that waste is an end-of-life issue, which required an explicit reconsideration of how the boundaries of the solid waste system are defined. Theory of Constraints (TOC) and System Dynamics (SD) methods were used in an abductive process to help understand the drivers behind solid waste generation, complemented by relevant theories and literature. The TOC analysis revealed that policy implementation suffers from an intention-behaviour gap that appears to have evolved from the disparity between economic and environmental drivers. Since the current reality appears to be dominated by economic drivers, this was developed further into a current reality tree with developed causal relationships providing the foundations for subsequent SD analyses. The quantitative aspects of this research were conducted by adopting a case study approach. The case study examined how single-use plastic packaging materials flow into and through the New Zealand economy to eventually become solid waste. An SD stock and flow model was developed to simulate the flow of materials and lifecycle harm generation based on 11 Life Cycle Assessment impact categories. Additional feedback mechanisms were incorporated to generate an endogenous demand for materials based on the effects of marketing, infrastructure lock-in, price, and perceived environmental performance. The efficacy of existing policies and processes are assessed through various policy scenarios, and the TOC evaporating cloud is reintroduced to generate novel possibilities for future policy development.

Findings suggest that pre-consumer factors that imbed and reinforce the demand for single-use plastic packaging are dominating the observed growth in these material flows. Additionally, the act of recycling may be responsible for a rebound effect that, perversely, increases the demand for single-use plastic packaging, negating many of the potential benefits of recycling practices. These findings build on the existing literature and the waste hierarchy principles that highlight the issues of using waste management practices to reduce the volume and harm from waste. The identification of rebound effects also highlights the limitations of the waste hierarchy's technical and linear nature, which fails to consider the social dynamics of the system it attempts to inform. These findings emphasise the need to reframe waste as the inevitable outcome of material throughput, which needs to be addressed throughout the value chain. This has wide-ranging implications for how we promote and invest in initiatives and provides a new perspective on traditional waste management practices.

This research provides three distinct theoretical contributions: applying a multi-methodological Systems Thinking approach to the field of solid waste, developing a qualitative dynamic hypothesis for solid waste generation, and creating a quantified system dynamics simulation model for the endogenous control of solid waste generation. These theoretical contributions all help address the identified research gap by answering the developed research questions. They also add to the literature of the separate methodologies as the application of TOC to solid waste issues is underexplored, and SD studies primarily focus on waste management and diversion, as opposed to the drivers of waste generation.

This research also provides methodological contributions through the application of a new method, the integration of methods, and the application of methods to a new area. Magic Druids are a new TOC method recently added to the TOC body of knowledge that do not appear to have been reported in an academic context previously. The use of TOC and SD methods have had limited applications together, with only minor overlaps between some of the TOC Thinking Processes and Causal Loop Diagrams. Additionally, TOC has been used to investigate the options for meeting people’s needs while reducing material throughput, which represents an unconventional application of the methodology.

Finally, practical contributions are also made through the developed models that can help inform policy development and where efforts should be focused to achieve the greatest impacts. Several of the current policy options appear to have very low leverage in moving the system outputs, and none are directed at changing the underlying growth paradigm.