Inconsistent definnitions of 'waste' across international organizations create critical data interoperability barriers that undermine effoorts towards global coordination of waste management. Thiis paper examines definnitional fragmentation among EU, OECD, and UNEP frameworks, using EU textile waste management as a case study. Current waste definnitions treat waste as an intrinsic material property analogous to mass or density, thereby failing to capture the contextual nature of the designation of something as waste. In this communication I propose a formal ontological framework based on Basic Formal Ontology (BFO) that reconceptualizes waste as a context-dependent role rather than a material characteristic. Thie framework distinguishes between the inherent dispositions of material entities, their designed functions, and assigned roles within specifinc contexts. Using the BFO framework, we definne waste as a role assumed by a material entity when (a) its designed function is no longer fulfinlled, (b) there exists an intention of disposal, and (c) there is no economically viable alternative realization of the entity's dispositions is realizable within the given context. Thiis approach provides machine-readable, universally applicable classifincation standards that enable standardized exchange of waste management data while accommodating jurisdictional variations. Thie proposed framework offoers a foundation for resolving international classifincation discrepancies and advancing circular economy initiatives through improved data interoperability.
Thie global waste crisis is rapidly escalating, with projections indicating a surge to 3.8 billion tonnes by 2050, from 2.3 billion tonnes in 2023
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Thiis paper argues that a refinned ontological framework for waste classifincation is crucial to overcoming this interoperability challenge. By explicitly definning and relating key concepts such as waste, resource, byproduct, and residue using a formal ontology like the Basic Formal Ontology (BFO) we can create machine-readable, consistent data representations. Thiis will facilitate more effoective data analysis, improved policy development, and ultimately, a more sustainable and circular textile economy within the EU and beyond.
In the European Union only about 25% of the textiles is collected for recycling and the rest primarily end up in landfinlls or incineration facilities [3]. Despite ambitious targets set by the EU’s Circular Economy Action Plan and the requirement for separate textile waste collection by January 2025 [4], textile waste management remains fragmented across member states [5]. Thiis fragmentation stems in part from diffoering collection infrastructures, but a more fundamental problem derives from the inconsistent classifincation, definnition, and data reporting systems used for textile waste [5].
Thie pervasive nature of these definnitional inconsistencies is exemplifined even in officcial data presentations. For instance, the explanatory notes for Textile waste generation across European countries based on Eurostat's ENV_WASGEN dataset [6] explicitly acknowledge fundamental methodological limitations: “As there is no harmonised method for Waste Collection Authority (WCA) across Europe, these numbers should be interpreted cautiously. Thiere are no data available on textiles in mixed municipal waste for Türkiye ... due to a lack of capacity, Ireland and Norway were not able to verify these data ... Italy indicated that its fingure for waste from economic activities is an overestimation as it includes non-textile waste like scraps from leather manufacturing or secondary textile waste” [6]. Thiese caveats reveal that even when atteempting to present standardized European textile waste data, researchers must acknowledge that the underlying classifincation and measurement systems are so inconsistent that direct cross-country comparisons become unreliable.
Thiis data limitation requires cautious interpretation of the aggregated data due to the lack of harmonized waste composition analysis methodologies across countries [5]. Even when countries collect textile waste data, the methods are so diffoerent that direct comparisons become nearly impossible [5]. For instance, how one country definnes and measures textile waste might diffoer substantially from another's approach [5]. Thiis variability could lead to signifincant discrepancies in understanding the true scale and nature of textile waste generation and management. Thiis observation highlights a critical challenge in waste management research: the inherent variability in data collection and analysis methods. Thie acknowledgment of data collection and analysis methodology demonstrates the complex nature of cross-border waste management data management.
Thie European Waste Catalogue (EWC) provides a standardized framework for textile waste classifincation across the European Union.
Table 1 EWC Codes for textile waste
EWC Code Description wastes from finishing containing organic solvents wastes from finishing other than those mentioned in 04 02 14 wastes from the mechanical treatment of waste (for example sorting, crushing, compacting, pelletising) not otherwise specified MUNICIPAL WASTES (HOUSEHOLD WASTE AND SIMILAR COMMERCIAL, INDUSTRIAL AND INSTITUTIONAL WASTES) INCLUDING SEPARATELY
COLLECTED FRACTIONS Note: Codes marked with asterisk (*) indicate hazardous waste
Thie fragmentation of textile-related codes across multiple primary categories – industrial waste (04), packaging and protective materials (15), mechanical treatment waste (19), and municipal waste (20) – creates systematic barriers to comprehensive textile waste tracking and analysis.
Thiis categorical dispersal hinders several interoperability problems. First, aggregating total textile waste data requires querying disparate database sections, as there is no unifined textile waste category that encompasses all material floows. Second, the classifincation system exhibits inconsistent granularity levels, with industrial textile waste (04 02) offoering detailed subcategorization including specifinc codes for composite materials, finnishing processes, and finber types, while municipal textile streams are broadly categorized as simply “clothes” (20 01 10) or “textiles” (20 01 11) without further specifincation.
Furthermore, the EWC’s mixed classifincation approach – combining source-based categories (industrial versus municipal origin) with material-based distinctions (processed versus unprocessed finbers) – introduces ambiguity in waste stream assignment. A textile item may transition through multiple EWC codes during its waste lifecycle, but the system provides no mechanism for tracking these transitions or maintaining material floow continuity. Thiis structural limitation becomes particularly problematic when atteempting to implement circular economy monitoring or trace material pathways for Extended Producer Responsibility1 schemes, as the classifincation system cannot adequately capture the dynamic nature of textile waste processing and recovery operations. 1 Thie Extended Producer Responsibility requires producers to take responsibility for their products' entire lifecycle, including post-consumer waste management, generating funding for recycling infrastructure and data to support environmental targets.
Thie challenge goes further when examining textile export procedures [7], where the Combined Nomenclature (CN) system – the EU’s standardized product classifincation framework for trade declarations – intersects with waste management regulations. Thie CN framework categorizes exported used textiles through two principal codes: 6309 for worn clothing and textiles, and 6310 for textile rags and scraps in both sorted and unsorted forms. While the theoretical distinction appears straightforward – 6309 encompassing materials suitable for second-hand markets versus 6310 covering items destined for industrial applications or deemed unsuitable for direct reuse – the practical implementation reveals signifincant classifincation ambiguities.
A critical gap emerges from the absence of a dedicated CN code for textile waste exports, despite textiles being explicitly listed on the EWC. Thie authorities must evaluate whether exported textiles constitute waste materials, typically correlating with CN classifincations where 6309 items are rarely designated as waste while 6310 materials face potential waste classi fincation. However, the reality of export practices ofteen involves large volumes of unsorted textile shipments containing diverse categories – household linens, industrial textiles, technical fabrics, clothing accessories, and mixed fiber compositions – that likely span both CN classifications, undermining the classification system's precision and creating uncertainty about the true nature of exported materials. Thie challenge emerges when a single export shipment might be classifined as CN 6310 for trade purposes, yet contain materials that would be categorized across multiple EWC codes (20 01 10 for clothes, 20 01 11 for textiles, 04 02 21 for unprocessed finbers) if they remained within the EU waste management system. Thie inability to reconcile these parallel classifincation systems means that textile materials effoectively “disappear” from waste tracking systems upon export, making it impossible to accurately assess whether the EU is meeting its circular economy targets or merely displacing its textile waste problem to other regions.
Thie neighbour-check2 study [5] highlights the signifincant challenges posed by the current fragmented and inconsistent approaches to textile waste management across Europe. Thie study reveals a lack of clarity concerning the scope of the revised Waste Framework Directive [4], which does not definne what is to be included under ‘textiles’ in the requirement for separate collection by 1st January 2025. Specifincally, it is unclear which categories of textile products are included and whether the separate collection extends beyond household textiles to encompass industrial and commercial sources.
Table 2 Adapted from Towards 2025 - Separate Collection and Treatment of Textiles in Six EU Countries (Miljøstyrelsen, 2020).
Denmark
Finland
Sweden
France
Netherlands
Germany
bring-banks where the collector clearly communicates that it ONLY receives clean, undamaged and reusable textiles. 2 A neighbour check is a comparative analysis where countries examine similar nations' regulations and practices to identify needed adjustments in domestic law or implementation [5].
Kerbside collection and bring-banks where the collector communicates that all types of textiles may be delivered.
where the collector clearly communicates that it ONLY receives clean, undamaged and reusable textiles.
Not waste
As the textile waste case study has demonstrated, diffoerent definnitions lead to signifincant data inconsistencies that undermine effoective waste management and policy coordination. For this reason, I will examine how ‘waste’ has been definned by major international organizations. Each governing body – the EU, OECD, and UNEP – provides distinct definnitions that are inflouenced by varying priorities, creating the definnitional fragmentation exemplifined in our remarks above Table 3 Definnitions of Waste
Institution
Definition
Weaknesses
EU [8] OECD [9] UNEP [10]
Any substance, material or object which the Subjective interpretation based on the holder discards or intends or is required to intentions or obligations of the holder discard. (e.g. materials abandoned without
intent may fall outside the definition).
Materials that are not prime products (i.e., May exclude waste with noneconomic products produced for the market) for implications. which the generator has no further use for production, transformation, or consumption, and for which he wants to dispose.
Substances or objects that are disposed of, Introduces inconsistencies due to intended to be disposed of, or required to varying national regulations, leading to be disposed of by the provisions of national different classifications of waste across law. countries.
Definning waste through the act of discarding raises two fundamental questions about value. Does the object itself lose inherent value through the act of discarding [9]? Or is the perceived loss of value merely a function of its context, a temporary state that can be reversed through re-use or re-purposing? Thiese questions highlight two distinct perspectives: a contextual view, which emphasizes the situational and subjective nature of value, and a material view, which focuses on the intrinsic properties of the object and its potential for future use regardless of its current context. Thie phrase ‘Waste isn't waste until we waste it’ captures an essential truth: waste is not an intrinsic property of materials but rather a context-dependent designation. Waste is a dynamic concept shaped by context, purpose, and perceived value. While ofteen viewed as an endpoint, waste can be a temporal stage, a resource waiting to be recontextualized. Thie thriving second-hand clothing market and the practice of recycling demonstrate this transformative potential. Even on a global scale, the value of waste value is flouid, as seen in Sweden’s import of waste for energy production, generating both revenue and a reduction in fossil fuel dependence.
Current definnitions of waste fail to capture its dynamic and context-dependent nature. Thie resultant static view hinders effoective waste management, overlooking the potential for reuse, recycling, and recontextualization. By recognizing waste as a flouid designation, capable of transformation through processes like recycling, we can unlock new opportunities for sustainability.
Thie United Nations Environment Programme and International Solid Waste Association's 2024 report explicitly recognizes this challenge:
Definnitions are a cornerstone in the development of legislation at all levels. ... Definnitions of waste and diffoerent types of waste, as well as how these definnitions are applied, vary internationally, including within regions or countries. Thiis may be due to diffoerent interpretations of terminology, lack of standardised categories, diffoerences in legal, regulatory, and policy frameworks, and major conceptual and methodological challenges concerning the observation and measurement of waste [9].
Given the fundamental role that definnitions play in developing policies and achieving international cooperation and standardization, particularly in collaborative domains like waste management, we believe it is essential to adopt an ontological approach that begins with establishing clear definnitional foundations. Thie current lack of standardized waste definnitions hinders effoective global cooperation, demonstrating the need to return to finrst principles. By grounding our approach in the Basic Formal Ontology (BFO) as a foundational framework, the next section will explore how we can build robust and universally applicable definnitions of waste from the ground up, providing the conceptual clarity necessary for international interoperability.
BFO (Basic Formal Ontology) is a top-level ontology, and it's designed to provide a foundational framework for representing knowledge across various scientifinc domains. Unlike domain-specifinc ontologies that focus on a particular area (e.g., medical ontology, biological ontology), a top-level ontology aims to establish a common set of fundamental categories and relationships that can be used to integrate data from diverse sources [11]. Thiis integration is crucial for facilitating interoperability and knowledge sharing across diffoerent scientifinc disciplines. BFO achieves this by providing a structured vocabulary and a set of formal axioms that definne the relationships between diffoerent types of entities.
BFO provides a robust framework for definning and relating key concepts that are essential for understanding waste classifincation. As a top-level ontology, BFO establishes fundamental categories and relationships that can be applied across domains. For building a definnition for waste in BFO terms, we believe it is important to examine three core concepts. First, we must consider Independent Continuants, which are material entities that exist independently and persist through time while potentially undergoing changes in their properties and relationships. Second, we need to understand the concept of Role, which represents a realizable entity that exists because there is some single bearer that is in some special physical, social, or institutional set of circumstances in which this bearer does not have to be and which is not such that, if it ceases to exist, then the physical make-up of the bearer is thereby changed. Thiird, we should examine Disposition, which is a realizable entity such that if it ceases to exist, then its bearer is physically changed, and whose realization occurs when and because its bearer is in some special physical circumstances, and this realization occurs in virtue of the bearer's physical make-up. Finally, we must also consider Function, which is a disposition that exists in virtue of the bearer's physical make-up and this physical make-up is something the bearer possesses because it came into being either through evolution (in case of natural biological entities) or through intentional design (in the case of artifacts), in order to realize processes of a certain sort.
To illustrate how these BFO concepts apply to waste classifincation, consider an aluminum can. Thie can itself is an independent continuant, the material entity that persists through its lifecycle. It can possess several dispositions inherent to its material properties: the disposition to conduct electricity, to be malleable, and to resist corrosion due to its aluminum composition. Thiese dispositions remain constant regardless of the can’s current use or status.
Thie can’s function, i.e, to contain beverages, derives from its intentional design and manufacture. Thiis function represents the purpose for which the can was created and refloects the specifinc physical design features (cylindrical shape, sealed construction, pop-top mechanism) that enable it to fulfinll this intended purpose.
However, the can’s role is context-dependent and can change throughout its lifecycle. Initially, it may have the role of “beverage container” when finlled with beverage and sold. From there, when discarded by the consumer, it might transition to the role of “waste”. Alternatively, it could assume the role of “recyclable material” when placed in recycling systems, or even “raw material” when processed back into aluminum stock.
Figure 1 demonstrates the ontological structure connecting an aluminum can with its realizable properties in waste management contexts. Thie diagram uses two distinct visual categories: orange nodes indicate BFO (Basic Formal Ontology) classes including Material Entity, Process, Disposition, Function, Role, and Realizable Entity, while blue nodes represent domain-specifinc classes and instances.
Thie aluminum can exemplifines a Material Entity that possesses three distinct realizable entities. First, it has an inherent recyclability disposition that becomes actualized during recycling processes. Second, it assumes a waste role when participating in waste management activities. Thiird, it fulfinlls a beverage container function through beverage containment processes. Thiese realizable entities demonstrate how the same physical object can simultaneously embody multiple ontological aspects depending on the processes in which it participates. Thie hierarchical relationship between recycling and waste management processes illustrates how specifinc activities can be components of broader operational frameworks.
Relationship types include: rdf:type (instantiation), rdfs:subClassOf (taxonomic hierarchy), has_disposition/has_role/has_function (property atteribution), realized_in (actualization of potentials), and part_of (mereological relationships). Thiis patteern exemplifines how BFO can be applied to model the multiple simultaneous roles, functions, and dispositions of material entities throughout their lifecycle, providing a formal foundation for circular economy and waste management ontologies.
Building upon the BFO conceptual framework, we can now develop a comprehensive definnition of waste that accounts for its multifaceted and dynamic nature. Thie challenge lies in capturing how the same material entity can transition between diffoerent roles while maintaining its inherent dispositions and original function.
Thie context-dependent nature of waste becomes evident when we consider how perceived value shiftes with technological advancement and economic conditions. Electronic devices once considered waste are now valuable sources of rare earth minerals, while materials treated as waste in regions lacking recycling infrastructure become valuable resources when exported to places where such technologies exist. Thiis variability demonstrates that waste classifincation cannot rely solely on material properties but must incorporate contextual factors.
Using BFO’s role-based framework, we can formalize this contextual nature by recognizing that waste assignment depends on the interplay between a material's inherent dispositions, its designed function, and the prevailing socio-technical context. Thiis approach avoids the definnitional ambiguities present in current international frameworks while maintaining the floexibility necessary to accommodate diverse waste management scenarios.
A material entity (independent continuant) assumes the role of waste within a specifinc spatiotemporal context when: (a) its designed function is no longer fulfinlled, (b) there exists an intention of disposal, and (c) there is no economically viable alternative realization of the entity's dispositions is realizable within the given context.
Thiis definnition captures the essential elements identifined in existing international frameworks while addressing their limitations. Thie reference to “designed function” accommodates the EU's focus on intended use, while “economically viable alternatives” addresses the OECD's marketoriented perspective. Thie contextual constraints acknowledge the UNEP's recognition of varying national implementations without being bound by specifinc legal frameworks. Table 4 BFO Formalization Support for Existing Waste Definnitions
Institution Definition BFO Formalization Approach
EU OECD UNEP
Any substance, material or object which the holder discards or intends or is required to discard.
Materials that are not prime products (i.e., products produced for the market) for which the generator has no further use for production, transformation, or consumption, and for which he wants to dispose.
Substance/material/object: continuant.
Holder: agent role.
Discarding: process.
independent Materials: independent continuants. Prime products are defined by their intended function within market processes.
Generator: agent role. Production, transformation, consumption are formalized as specific relations between agents and materials.
Substances or objects that are disposed of, intended to be disposed of, or required to be disposed of by the provisions of national law.
Substances/objects: independent continuants. Disposal processes are formalized with clear start and end conditions.
Table 4 focuses on how BFO can provide the formal foundation needed to address the limitations identifined in existing institutional definnitions. BFO's structured approach offoers the conceptual tools to transform informal definnitions into precise, machine-readable specifincations while maintaining their core meaning and regulatory intent.
For the EU definnition, we can formalize the subjective aspects of “discarding” and “intention” by explicitly modeling the relationships between holders, materials, and contextual factors. Thie framework can represent the conditions under which abandonment occurs, even without explicit intent, by definning abandonment as a process that results in a change of role assignment.
Thie OECD definnition's focus on economic utility can be formalized through BFO’s disposition and function categories. Materials can be modeled as having economic dispositions that may become inactive or unfeasible within specifinc contexts, leading to waste role assignment. Thiis approach addresses the limitation of excluding non-economic implications by allowing for multiple simultaneous considerations in role assignment.
For the UNEP definnition's reliance on national legal frameworks, BFO provides a foundation for representing legal contexts as spatiotemporal regions with specifinc normative properties. Thiis enables the modeling of jurisdiction-dependent waste classifincations while maintaining a unifined underlying structure that facilitates cross-jurisdictional data integration.
Thie ontological approach thus provides a formal foundation that can accommodate existing definnitional approaches while offoering a path toward standardization and interoperability. By representing the underlying logical structure of waste classifincation, BFO enables the development of mapping tools that can translate between diffoerent definnitional frameworks while preserving semantic consistency.
Thiis paper demonstrated the critical need for a standardized, interoperable approach to waste classifincation, highlighting the signifincant challenges posed by inconsistent definnitions and data reporting across international organizations and within the EU. Thiese finndings establish a foundational case for developing formal ontological frameworks in the waste management domain, where the complexity of material life cycles, the diversity of stakeholder perspectives, and the need for cross-jurisdictional data integration create an environment where ad hoc definnitions and classifincation systems are required for effoective policy implementation and technological solutions.
By proposing a refinned ontological framework based on BFO, this paper addresses the dynamic and context-dependent nature of waste while providing the formal structure necessary for machine-readable classifincations. Thie analysis of textile waste management across European countries clearly demonstrates how definnitional inconsistencies create cascading problems throughout the waste management value chain. Future work will involve: • Developing a comprehensive domain-specifinc ontology for waste management based on the BFO framework, incorporating insights from existing waste management ontologies and technical artifact research; • Creating mapping tools to connect existing classifincation systems to the standardized ontology, facilitating transition from current fragmented approaches; • Testing the framework with real-world textile waste data to validate its practical applicability; • Extending the ontology to diffoerent waste streams; • Collaborating with policy makers and industry stakeholders to ensure the ontological framework addresses practical implementation challenges.
Thie adoption of an ontological approach is not merely a technical solution; it is a crucial step towards achieving the ambitious sustainability goals set by international organizations and individual nations, paving the way for a more efficcient and environmentally responsible future for waste management.
I would like to express my gratitude to Barry Smith for his guidance, revision and constructive talks. I am also deeply appreciative of Katie Johnson, Jisoo Seo, and Brandon Long for their encouragement and assistance during the early months of my PhD journey.
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