1. Introduction
In recent years, companies have increasingly explored strategies to extend products beyond their initial use phase. A notable example is the refurbishment of industrial equipment, such as ABB’s reused robots (Reference Skärin, Rösiö and AndersenSkärin et al., 2022). After their “first life,” these machines are restored and redeployed, cutting material and energy consumption. This approach aligns with circular economy principles and mitigates environmental impacts. Yet, except for a few incentives like emission credits, current frameworks provide no direct reward for designing products with intentional second-life prospects, leaving a key sustainability benefit underrecognized.
Environmental certification and impact assessment methodologies, notably Life Cycle Assessment (LCA), offer credible measures of a product’s footprint. LCA underpins widely recognized certifications like Environmental Product Declarations (EPDs) and the Product Environmental Footprint (PEF), guiding informed decision-making and boosting companies’ reputations. Such assessments are vital for advancing the United Nations Sustainable Development Goals and for facilitating the shift from a linear to a circular economy. Extending a product’s lifecycle—whether by refurbishment, remanufacturing, or repurposing—cuts resource extraction and waste, reducing environmental burdens overall.
However, integrating second-life strategies into LCA-based analyses is challenging. Predicting future uses, maintenance, end-of-life scenarios, or emerging harmful substances is fraught with uncertainty. For complex products composed of numerous parts, these complexities make it nearly impossible to develop reliable life cycle inventories at the early design stage. Current quantitative approaches struggle to handle scenario-based, multi-life designs. As a result, the environmental benefits of second-life strategies often go uncertified or under-communicated, limiting their market uptake. Even more, there is no direct benefit for a company in terms of accredited reduced environmental impact in developing a product with enhanced second life opportunities.
This paper investigates these challenges and outlines the barriers to using LCA in design for more life cycles (e.g. second-life product design), such as accounting different functional units within the same LCA analysis and the need of tracking life-cycle data across in contexts characterized by the variability of second life-scenarios. By identifying gaps and potential solution strategies, it proposes a research agenda for advancing methodologies that more effectively capture the environmental benefits of extended product lifespans. In doing so, it aims to support the creation and certification of truly sustainable solutions that better align with circular economy goals.
The next section summarizes the relevant background, framing the arena of environment-wise approaches and the methods to support and inform design to reduce impacts onto the ecosystem, with a specific focus on LCA and related certifications, given their industrial interest both to improve product appeal (e.g. in B2B contexts) and enable market access wherever there exist bounding environmental laws and regulations. The method, based on examples from the literature, is shortly presented in section 3. The fourth section presents two examples with multiple second-life scenarios, which introduce additional uncertainty and potential variations that the existing LCA standard is not able to cover adequately. Before the conclusion of the paper, the implications of the challenges are discussed in section 5 together with opportunities and possible strategies to tackle them and provide more quantitative support and inform design.
2. Background literature
2.1. Resource use: circular economy and eco-design methods and tools
The wiser use of resources is imperative to minimize the extraction of virgin materials and reduce the waste generated by consumables or products at the end of their lifecycle. Circularity principles promote a shift from the traditional linear economy, where products progress from resource extraction to disposal, toward a circular model. In this framework, resources nearing the end of their lifecycle are redirected into new cycles, either in the same or different applications, fostering a regenerative process. The 9R framework—Refuse, Rethink, Reduce, Reuse, Repair, Refurbish, Remanufacture, Repurpose, Recycle—encapsulates strategies for resource optimization at multiple lifecycle stages (e.g. Kirchherr et al, 2017). These strategies aim to prioritize resource efficiency and minimize environmental impact. Despite the potential of these strategies to reduce demand for new materials and enhance sustainability, their direct correlation with environmental impact remains insufficiently clarified, highlighting a need for further exploration and validation (e.g. Picatoste et al, 2022).
Ecodesign, design for end of life, design for the environment, sustainable design, design for sustainability, are different names that, despite some minor semantic differences, refer to methods and tools sharing a common goal: the reduction of environmental impacts. These methods are nowadays many and very different from each other, so that many reviews have already explored their characteristics (e.g. Rossi et al, 2016; Pigosso et al, 2015; Reference Chiu and ChuChiu and Chu, 2012), and classified them in terms of their primary objectives, the application stages within the design process, the level of decision-making they support, etc. Some tools focus on detailed environmental impact assessments, offering quantitative insights best suited for late-stage design validation, while others are tailored for early-stage ideation, providing qualitative guidance or semi-quantitative approximations to inform strategic decisions. Another dimension of classification considers their functional purpose, such as optimizing specific lifecycle phases (e.g., Design for X approaches (e.g. Reference Boorsma, Balkenende, Bakker, Tsui and PeckBoorsma et al, 2021), where X might be for end-of-life, remanufacturing, etc.) or addressing trade-offs between environmental, economic, and technical criteria (such as TRIZ-based eco-design approaches, e.g. Russo et al, (2014)). Additionally, tools can be grouped by their degree of integration into design workflows, ranging from standalone methods like guidelines and checklists to fully integrated frameworks combining CAD platforms, LCA models, and eco-innovation strategies (e.g. Tao et al, 2018).
2.2. Quantitative approaches for environmental product certification
Quantitative methods are essential for systematically estimating product emissions and providing reliable data for declarations or certifications accessible to third parties. Among these, the Life Cycle Assessment (LCA) forms the backbone of advanced methodologies such as Environmental Product Declarations (EPD) and Product Environmental Footprints (PEF). These approaches rely on standardized frameworks to ensure robust and comparable assessments of environmental impacts. Recognized as some of the most established and credible tools for quantifying product-related emissions, these methods are particularly well-suited for linking emission reductions to potential benefits, such as financial incentives or regulatory credits, making them invaluable in an industrial context (e.g. Reference Corona, Shen, Reike, Carreón and WorrellCorona et al, 2019).
Figure 1. Common approaches to allocate impacts and credits in LCA between first and next cycles, based on reviewed literature (schematic simplification) (from Reference Corona, Shen, Reike, Carreón and WorrellCorona et al., 2019)
Life Cycle Assessment (LCA), as defined by ISO 14040:2006+A1:2020 and ISO 14044:2006+A2:2020, provides a systematic method for quantifying the environmental impacts associated with a product’s entire lifecycle, often referred to as a cradle-to-grave perspective. It consists of four iterative phases: Goal and Scope, Life Cycle Inventory, Life Cycle Impact Assessment, Interpretation. The Goal and Scope phase determines the purpose of the assessment, the product system boundaries (e.g., cradle-to-grave, cradle-to-gate), and the functional unit, which quantifies the product’s performance and ensures comparability for impact (e.g.one square meter of insulation material with a thermal resistance of R=2 m2·K/W over 50 years” for building insulation). Life Cycle Inventory (LCI) consists of modelling the inputs and outputs flows of energy and material within the system boundaries. The collection of quantitative data about input and output flows, such as emissions to air, water, and soil, and waste production. are essential to estimate the potential environmental impacts in the third phase: Life Cycle Impact Assessment (LCIA). This stage leverages a model to translate LCI data into potential environmental impacts using impact categories, such as climate change (e.g., CO2 equivalents) and resource depletion. Finally, Interpretation aims to identify significant impacts, verify consistency with the goal and scope, the robustness of the results and propose actionable insights for improvement.
LCA incorporates allocation and cut-off criteria, two critical concepts to ensure consistent and meaningful system boundary definitions and impact allocations across multiple products or processes.
Allocation is the preferred approach when a process generates multiple outputs (e.g., dairy production yielding milk and butter), the environmental burdens must be distributed, e.g. by means of mass properties (mass allocation) or by the market value of each output (economic allocation). Instead of distributing burdens, another approach foresees the expansion of the system boundaries, which often results into the substitution of the target for the study and a change for the functional unit. Still related to system boundaries, cut-off criteria define what data or processes are included or excluded from the system (e.g. exclude what is contributing less than 1% to the total impact).
Environmental Product Declarations (EPD), contrarily to LCA, are meant at providing a clear output about the environmental performance (whether it is about consumptions or emissions) of a product, which is understandable to its target audience. The ISO 14020 series provides a comprehensive framework (Figure 2) for product environmental declarations, divided into three types: Type I (Eco-labels, ISO 14024), which are voluntary, third-party verified programs awarding labels to products meeting predefined environmental criteria; Type II (Self-declared Environmental Claims, ISO 14021), which allow manufacturers to make environmental claims directly, without external verification; and Type III (Environmental Product Declarations, ISO 14025), which are detailed, third-party verified reports based on LCA results. These declarations are guided by Product Category Rules (PCRs), defined under ISO/TS 14027, which standardize methodologies for conducting LCAs within specific product categories. The framework, indeed, integrates additional standards, such as ISO 14040 and ISO 14044 for LCA methodology, ensuring consistency and reliability in quantifying environmental impacts.
Moreover, PCRs define the requirements for EPDs of products within the same category, ensuring consistency and comparability. They specify functional units, system boundaries, allocation rules, and environmental impact categories relevant to the product group. However, PCRs often vary between countries, creating potential disparities in results and interpretations depending on the regional context.
The Product Environmental Footprint (PEF) is the reference, harmonized approach chosen by European Commission for product environmental certification (Commission Recommendation (EU) 2021/2279). It addresses the abovementioned inconsistencies of PCRs by introducing Product Environmental Footprint Category Rules (PEFCRs). These provide stricter, standardized guidance within product categories, ensuring comparability of results and promote uniformity across different EU member states mitigating the regional variability which characterizes the implementations of EPDs. Moreover, the strictness of PEF compared to EPD is also made evident by the guidance provided for allocation and cut-off. Allocation procedures prioritize methods such as system expansion or substitution to avoid mass/energy-based allocation when possible, despite this is in any case preferred over economic allocation. For what concerns the cut-off criteria, PEF emphasizes comprehensive data inclusion, generally discouraging their use.
PCRs, however, are not available for every product category and the wide variety of possible second-life scenarios to be figured out when designing the original product (first life), make these certification-oriented method challenging to use and make them provide meaningful data to inform and steer design.
Figure 2. Structure of the ISO 14020 family of standards
3. Methodological approach
The proposed method involves identifying and arranging meaningful, literature-based examples of products that can embody multiple, second-life strategies, guided by the 9R framework of the circular economy. By exploring a diverse set of realistic second-life scenarios—some more suitable and better established than others—this approach reveals the inherent complexities in applying LCA-based approaches to inform design decisions for extended product lifecycles. The products selected are chosen for their potential to illustrate clearly defined second-life configurations, as well as for their partial integration into existing circular value chains (electric batteries and tyres). Through these curated examples, the method highlights which stages of LCA would benefit from additional guidelines or increased methodological flexibility, enabling more holistic environmental assessments that consider multiple, interconnected lifecycles.
4. Exemplary scenarios
This section highlights, through examples, how the current means to account for LCA credits for the first life of products are effective in taking into account second life scenarios, hence recognizing any design choice that enables environmentally more sustainable second life options.
In turn, significant differences emerge in design scenarios where the second life is known or can be easily controlled by the manufacturer of the product in the first life, against scenarios where the second life is outside the direct control of the manufacturer (Figure 3). In the latter scenarios, current LCA accounting systems hinder the account for environmental credits in the decision-making phase of product development. Therefore, the manufacturer of the product in first life does not have any incentive to consider more sustainable second life scenarios simply because they are not accountable.
Figure 3. LCA-based emission credits estimation challenges of 2nd life products during their 1st life
The following sections describe the two situations with two examples, one related to automotive batteries and one related to automotive tyres.
4.1. Accounting for LCA in controlled second life scenarios: an automotive battery case
This case considers Electric Vehicle (EV) batteries (Figure 4). Due to the performance degradation of EV batteries at the end of their lives (Reference Picatoste, Justel and MendozaPicatoste et al., 2022), the possibility of resigning them within the same application (still as an EV batteries) is often not possible (Scenario 1). Often, the only way to avoid the disposal of EV batteries in landfill (Scenario 2) is to recycle the batteries material, or to repurpose them in less demanding applications, such as a domestic power wall (Scenario 3).
The scenarios for both recycling and repurposing could be many, but to be able to account for the LCA during the first life (as an EV battery) and to claim LCA credits in a credible and trustworthy manner the possible scenarios are still within the established business envelope of the company (i.e., the company manufacturing and selling the repurposed power wall is still the same or directly connected to the company manufacturing the EV). This is because how to analyse the circularity benefits through LCA and how environmental savings relate to different CE strategies remain unclear (Reference Picatoste, Justel and MendozaPicatoste et al., 2022). In fact, there is a wide range of LCA approaches to study the environmental performance of electric vehicle batteries with different functional units (FU), system boundaries, and battery lifetime assumptions.
Figure 4. Accounting for LCA in controlled second life scenarios: an automotive battery case
Table 1. Functional Units, System Boundaries & Lifespan assumptions (automotive battery case)
However, as far as the manufacturer of the EV battery has control on the conditions that lead to scenario 1 and 3, there is the possibility to account for the fraction of components being repurposed, with appropriate decisions for the Functional Units. These require the LCA analyst to expand the system boundaries (e.g. addressing the issue via system expansion as stated in ISO 14040/14044) while introducing additional assumptions to normalize the duration of the technology in order to work around the limitations due to different lifespan (e.g. Reference Husmann, Beylot, Perdu, Pinochet, Cerdas and HerrmannHusmann et al, 2024).
4.2. Accounting for LCA in uncontrolled second life scenarios: an automotive tyre case
In most cases, second life scenarios of a product fall outside the business control of first life manufacturers. The challenge can be exemplified by looking at the case of automotive tyres (Figure 5).
Waste tyres still undergo a variety of different scenarios such as tyre-derived fuel, rubber for insulation, structural applications for civil engineering, playground surfaces, landfills and many others (Ross D., 2020). As highlighted in Reference Campbell-Johnston, Friant, Thapa, Lakerveld and VermeulenCampbell-Johnston et al. (2020), it is necessary to create the conditions for extended producer responsibility (EPR) which imply multi-stakeholder governance, effective monitoring means and regulations that promote circular business models. However, most of the circularity scenarios require resource-intensive treatment and post treatment processes to enable high-quality material recycling. On the contrary, the use of tyres for revetment, as discussed in Reference Collins, Jensen, Mallinson, Smith, Mudge, Russel, Limbachiyya, Paine, Dhir, Limbachiyya and PaineCollins et al. (2001) and in Reference Simm and WallisSimm and Wallis (2004), does not involve significant reprocessing of exhaust tyres, but raises concerns in terms of environmental impact and related hazards.
Overall, to avoid ending up in landfill or to be incinerated, tyres could be remanufactured by replacing the tread on used tires. This technique is performed on the casings of worn tires after they have undergone inspection and necessary repairs. Approximately 90% of the original tire material is retained during retreading, making it a cost-effective alternative, with material expenses being around 20% of those required to produce a new tire. From an LCA perspective, it is rather straightforward for the tyre manufacturer to account for the credits of the tyre in second life (since the product maintain its function and application. The same cannot be said for other potential second life scenarios for the tyre (Reference Simm and WallisSimm & Wallis, 2004) such as a tyre revetment, a reef structure under water, or boat fenders (Figure 5 in the bottom).
Figure 5. Accounting for LCA in uncontrolled second life scenarios: an automotive tyre case
From an LCA perspective, it becomes challenging for the tyre manufacturer to account for the LCA in these new second life scenarios, as the functional unit and the business boundaries of these scenarios are outside the direct control of the manufacturer. Table 2 highlights the differences between FUs for the first life of automotive tyres and the possible second life depicted by scenario 5: repurposed to build levees for shoreline protection (whose FU is the same used in an LCA study with non-tyre solutions).
Table 2. Functional Units, System boundaries and Lifetime assumptions (automotive tyre case)
Table 2 presents just one example among the three scenarios of Figure 5 the tyre manufacturer cannot control, but this is sufficient to show the difficulty of calculating the “fraction” of LCA credits to consider in the first life of the tyre. Moreover, the expansion of system boundaries might be daunting for even the most willing LCA analyst to build multiple Life Cycle Inventories based on potential transformation processes whose sources of primary data are impossible to find. Similarly said for the very different lifespans the scenarios cover. While the accounting for emission credits may seem a business administration challenge, it has profound implications for “design for” strategies. Tyres are now designed for their first life, and eventually to make the remanufacturing process easier. It could be that the optimal design for a tyre considering scenarios 4, 5 and 6 is substantially different than the optimal tyre design in the first life, e.g. by embedding solutions to simplify material extraction, to prevent toxic substance release in scenarios 4 and 5 etc.
5. Discussion
While some of the challenges presented have implications for policy making and business administration, they impact the design activities as well. These can be summarized as:
1. The change of functional unit when moving radically the application type in second life makes it challenging to compare the LCA of different scenarios during the design of the product in first life. Valid alternatives could be disregarded simply because of the inability to compare and claim LCA credits in favour of a design that enables a better use in second life.
2. Even if the functional unit stays the same, it is difficult to get reliable data for making an LCA analysis that accounts for many relevant second life product strategies. This is partly because of data sharing issues among different stakeholders, but also because it may be difficult to separate the LCA contribution of a single component in a much bigger system.
3. The feasibility of second life product strategies depends on external factors (regulations, demand from customers) that may not be known during the design of the product during first life. These strategies may be “unlocked” in the future. This makes it difficult to make a design that is resilient to the change of second life product strategies.
To tackle these three design challenges, we recommend possible directions for investigation. Challenge 1 calls for extension methods for considering multiple function units for products in second life. These challenges have been already discussed for multi-functional products in their first life (e.g., Reference Reap, Roman and DuncanReap et al., 2008) and are now increasingly recognized for the second life. Some interesting learnings could be made by looking at other sectors where the difficulty of comparing different second life strategies. For example, the space sector is investigating possible strategies for human settlements in other planets, with the difficulty of comparing different scenarios and assessing the trade-offs between initial investment costs and the operational longevity of systems, guiding cost-effective and energy-efficient designs. For these reasons, research is investigating the opportunity to use the concept of lifetime embodied energy as a metric designed to quantify the total energy invested in a system over its entire lifecycle (Reference Lordos, Hoffman, de Weck, Badescu, Zacny and Bar-CohenLordos et al., 2023).
Challenge 2 calls for improved ways to share data across products and companies to make more reliable LCA analysis. While some upcoming legislations such as the digital product passport DPP) by providing detailed, standardized, and traceable data on a product’s entire lifecycle (Lövdah et al., 2023). However, to use DPP data during the design phases with multiple scenarios may arise complexity, because DPPs provide static or aggregated information about the product’s lifecycle, which may not account for dynamic and diverse usage scenarios, such as different operational environments or maintenance strategies, that significantly impact LCA outcomes. Here, there could be opportunities to integrate the benefit of a DPP with the ones of Product Lifecycle Management (PLM) systems. PLM data offers insights into product variations, design revisions, and evolving operational contexts that are critical for scenario-specific LCAs. Additionally, adaptability for future use cases is a challenge, as DPPs may struggle to incorporate predictive data or adapt to evolving practices and technologies, whereas PLM systems excel in managing updates and version control (Reference Tao, Li and YuTao et al., 2018).
Challenge 3 calls for methods to keep the design space of the product in its first life as open as possible to account the up taking of second life product strategies (since these may be highly uncertain). Here, some interesting learnings can be made by looking into development approaches that aim at exploring multiple design options simultaneously and systematically narrowing them down based on feasibility, performance, and constraints. Examples of these approaches are Set Based Concurrent Engineering (SBCE; Reference Sobek, D., Ward and K.Sobek et al., 1999; Reference Kerga, Rossi, Taisch and TerziKerga et al., 2014), in which teams define a broad “set” of potential solutions rather than committing to a single option. These sets include a range of possibilities that meet initial requirements or goals. More analytical approaches are Tradespace Exploration (TE) and Epoch-Era analysis (EEA; Reference Ross and RhodesRoss and Rhodes, 2008) which aim at analysing how a system’s performance evolves over time under changing scenarios. What these methods enable is the identification of flexible designs that, while initially sub-optimal, could perform better if conditions change. Applied to sustainable design and LCA, these approaches could allow to identify design options that are sub-optimal in their first life, but that perform better if extended into more sustainable second lives.
6. Conclusion
This paper highlights the challenges and opportunities in integrating second-life strategies into Life Cycle Assessment (LCA) to support sustainable product design. While LCA and related certifications like Environmental Product Declarations (EPDs) and Product Environmental Footprints (PEFs) are critical tools for advancing circular economy principles, their current frameworks are not well-suited to address the complexities of multi-life product scenarios. Specifically, issues such as functional unit changes, data sharing across stakeholders, and the unpredictability of future second-life strategies hinder the effective integration of these strategies into early design processes. Through the case studies of automotive batteries and tires, we demonstrate how existing LCA methodologies adequately address controlled second-life scenarios are limited for uncontrolled, more dynamic ones. This limitation restricts the incentives for designing products with enhanced second-life prospects and may lead to the underutilization of sustainable design opportunities. To overcome these barriers, we propose three key directions for future research. First, methodologies should be developed to account for multiple functional units in second-life scenarios. Second, the integration of Digital Product Passports (DPPs) with Product Lifecycle Management (PLM) systems could provide a more dynamic and comprehensive data-sharing framework, enabling scenario-specific LCAs during the design phase. Finally, design approaches such as Set-Based Concurrent Engineering (SBCE) and analytical methods like Tradespace Exploration (TE) and Epoch-Era Analysis (EEA) offer promising pathways to explore flexible, multi-scenario design solutions. These methods could enable the identification of initially sub-optimal designs that become more sustainable and effective when extended into second-life applications. By addressing these challenges, the methodologies and strategies discussed in this paper aim to better align product design with circular economy principles, ultimately fostering the creation of more sustainable, resilient, and adaptable products. This research provides a foundation for advancing LCA-based approaches that can more effectively capture the environmental benefits of extended product lifespans, supporting the transition to a circular economy and the achievement of global sustainability goals.
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