Defining Circularity for Plastics

The current, predominantly linear approach to the plastics economy results in inefficient resource use, unnecessary waste and unprecedented pollution. This approach creates multiple social, economic, and environmental problems that characterise the global plastic pollution crisis. Multiple reports set out the case for a transition to a circular plastics economy, in which materials are retained in the economy for as long as possible to minimise waste and pollution. However, the specific approach to delivering operational plastics circularity is often undefined and unclear. Given the urgency of finding a systemic approach to reducing plastic pollution, it is critical to define circularity for plastics. This report therefore aims to identify an evidence-based definition and accompanying set of principles for the circularity of plastics.

The review to find and evaluate definitions and principles of a circular economy and discuss what they mean for plastics was undertaken in four parts. A desk-based review was conducted by searching the academic and practitioner literature using Boolean searches across multiple databases to identify literature that specifically defined circularity and identified principles of a circular economy. Remote structured interviews were conducted with 6 experts and actors in the plastics and circular economy field. The definitions and principles, and interview transcripts were text-coded to identify the core elements and components of each definition and set of principles. The final step was to convene a workshop with the Defra project team to discuss the definitions and principles identified and to consider which, with respect to plastics, should be used throughout the project

A definition for plastics circularity serves as a foundational framework to evaluate whether a specific activity, material, product, or system aligns with the circular economy. This definition functions as a set of criteria or benchmarks that must be met for something to be considered circular. If a material, product or process fails to meet the criteria in the definition, it cannot be classified as circular. In the database, 204 entries for definitions or principles were identified. Of all the entries there were 185 definitions, 59 sets of principles, and 49 entries with both. Of the 49 with both a definition and an accompanying set of principles, none was specific to plastics.

The most frequently identified core elements of definitions of circularity (in general) were removing or reducing waste, keeping resources or materials in use, minimising or preventing pollution, maintaining the value of materials or resources, and product or material design. The most common core elements of the 19 definitions specific to plastics circularity were removing or reducing waste, maintaining the value of materials or resources, keeping resources or materials in use, and minimising or preventing pollution. All interviewees highlighted the need to recirculate products or materials to retain their highest value, while half of all interviewees added that this needs to be for as long as possible. Other core elements of a definition of plastics circularity prevalent in the interviews were prioritising processes according to the zero waste hierarchy, the need to cover the entire life cycle of plastics, and decoupling economic activity from resource use.

Based on the literature review, expert discussions and interviews, the following suite of core elements were identified as essential to a definition for the circularity of plastics:

●Decouples economic activity from resource use or extraction
●Covers the full life cycle of plastics
●Follows the zero waste hierarchy
●Maintains the value of materials by keeping them in use as long as possible
●Removes or reduces waste
●Balances environmental integrity and social sustainability with economic value

Further analysis was undertaken of examples of definitions and a series of potential definitions were developed. While the definition offers a high-level understanding and determines whether or not a material, product or system is circular, a set of principles provides practical guidelines that operationalize the core concept and act as "guard rails," guiding actions and decisions in alignment with the overarching goals of circularity. Of the 60 sets of principles, all were for general materials. Definitions that were original comprised 32, while 28 were based on other definitions, neither of which had any that were plastics specific. Based on the text coding of the literature review and associated count of the principles, the most frequently cited were those of the Ellen MacArthur Foundation, namely: design out waste and pollution; circulate products and materials at highest value; and protect, regenerate or restore nature. The Rs of reuse, recycle, reduce, refill, repair and remanufacture followed next as the most common principles upon which a circular economy is based. Essential principles identified by the interviewees were varied, but the most commonly highlighted principles were the need to minimise waste and pollution, including that associated with greenhouse gas emissions; the need for protection of jobs and/or economic prosperity; and the need to ensure the health, safety and human rights across the entire value chain. The ‘Rs’ which include reuse, recycling, refill, repair, redesign, remanufacture, and others, were excluded since these do not guide decision making, but rather act as vehicles through which circularity can be delivered. Based on the literature review, expert discussions and interviews, the following five principles were identified as essential to guiding decisions on the circularity of plastics.

Any activity in line with plastics circularity must:
●Protect, restore or regenerate nature
●Ensure inclusive outcomes, quality job creation, fair and safe working conditions and that human rights are upheld
●Minimise pollution, including emissions and chemical leakages from plastics production, processing and disposal
●Transition away from the production of virgin materials, in line with the zero waste hierarchy
●Uphold dynamic safeguarding
All of the principles apply and are relevant to every material in the plastics economy. Any decision, policy, activity or process related to plastics should conform to all of these principles. The principles follow no hierarchy, and should all be considered equally. Measurable principles allow for the tracking of progress which fosters a culture of accountability and transparency. As such, a series of possible metrics or measurable targets for each principle is presented.

In adopting a set of definitions and principles for plastics circularity, several limitations were evident. First, definitions and principles in the literature and applied in practice are highly varied. Second, terms such as 'plastics', 'lifecycle', and others related to circular economy are often defined and applied inconsistently across various studies and practices. This inconsistency can lead to misunderstandings and hinder the development of cohesive approaches to circularity. Third, this research was restricted to open access literature, or that which is available behind paywalls to academic institutions, which may not encompass all available or relevant information on the topic. Finally, limiting research to English-language sources excludes a significant body of work in other languages, potentially overlooking valuable insights, case studies, and approaches adopted in non-English speaking regions.