The confusing terminology of “upcycling”

Technical Summary: The Confusing Terminology of "Upcycling"

Problem Statement
The term "upcycling" has emerged as a prevalent buzzword in both general society and academic literature, with usage surging since 2014 to exceed 1,000 papers annually by 2025. Despite its popularity, the terminology suffers from significant ambiguity. While general definitions (e.g., Oxford English Dictionary, Wikipedia) emphasize creating items of "greater quality or value," academic applications vary widely across disciplines. In fields like food science, an established definition exists, whereas in chemistry, materials science, and construction, the term is used inconsistently. This lack of a unified definition creates confusion, with many processes labeled as "upcycling" potentially being better described by traditional terms such as recycling, upgrading, regeneration, or repurposing. The study addresses the need to clarify these distinctions and propose a rigorous academic definition.

Methodology
The authors conducted a comprehensive trend analysis and qualitative review of academic literature:

1. Trend Analysis: A survey of papers containing "upcycl*" in the title, abstract, or keywords was performed to track publication volume from 1995 to 2025. Papers were manually categorized into six domains: (1) Chemistry/Plastics/Polymers, (2) Food/Agriculture/Bio, (3) Metals/Inorganic Materials, (4) Construction, (5) Batteries, and (6) Others.
2. Review Article Analysis: The authors extracted 190 review articles published in 2024 and 2025. These were manually categorized and scrutinized to determine the frequency and nature of explicit definitions of "upcycling" within each field.
3. Comparative Definition Review: The study analyzed how specific fields (particularly chemistry, food, metals, and batteries) define the term, comparing these against general dictionary definitions and existing frameworks like the Upcycled Food Association's criteria.

Key Results

• Publication Trends: The number of papers containing "upcycling" grew exponentially after 2014. The "Chemistry, plastics, polymers" category is the most dominant, followed by "Food, agriculture, bio" and "Metals, inorganic materials." The "Batteries" category showed rapid recent growth, surpassing "Construction" in 2025.
• Definition Prevalence: Explicit definitions of upcycling are found in only a minority of review articles overall.
  • High Prevalence: In "Chemistry, plastics, polymers" (56 of 104 articles) and "Batteries" (7 of 10 articles), definitions were frequently mentioned.
  • Low Prevalence: In "Food/Agriculture/Bio," "Metals," and "Construction," definitions were rarely included (10–20% or less), often because the term is either assumed known or used loosely.
• Disciplinary Variations:
  • Chemistry/Polymers: Definitions often focus on creating "high-value materials" and "open-loop" systems (creating different materials from the original). However, there is no consensus on how to measure "value," and some articles equate upcycling with chemical recycling or monomerization, while others include fuel production.
  • Food: Relies on an established definition requiring the material to be waste/by-product, converted into human food, via a process that increases value and involves innovation.
  • Metals/Construction: The term is often used synonymously with "upgrading" (removing impurities) or "repurposing" (using waste for construction without creating new materials), which the authors argue may be mislabeled.
  • Batteries: Definitions vary between "direct upcycling" (restoring performance) and "repurposing" (using spent batteries as chemical resources). Some authors distinguish direct regeneration from upcycling unless structural modifications occur.

Proposed Definition
Based on the review, the authors propose the following academic definition:

"Upcycling is a process that uses waste or by-products to create a quantity and quality of high-value materials that are distinct from the original materials through innovative methods."

This definition requires four simultaneous elements:

1. Input: Use of waste, by-products, or similar materials.
2. Output: Creation of high-value materials (considering both quantity/yield and quality/purity).
3. Distinctness: The resulting materials must be distinct from the original substances (distinguishing it from closed-loop primary recycling).
4. Methodology: The process must employ innovative methods.

Significance and Claims
The paper claims that the current loose application of "upcycling" dilutes the concept and causes terminological confusion. By proposing a strict definition, the authors aim to:

• Distinguish upcycling from traditional recycling (closed-loop), downcycling, upgrading, and repurposing.
• Clarify that processes merely returning materials to their original form (e.g., monomerization for the same plastic) or converting waste solely to fuel (thermal recovery) do not constitute upcycling under this definition.
• Encourage the academic community to use precise terminology. The authors suggest that if a process fits the definition of traditional recycling, upgrading, or repurposing, those specific terms should be used instead of "upcycling" to maintain conceptual clarity and scientific rigor.

The study concludes that while the definition is heavily influenced by trends in chemistry and polymer research, it is applicable across the reviewed academic fields, including food science, to ensure a shared understanding of the term's scope and limitations.