1. Introduction
One of the critical challenges of our era is achieving sustainable growth amidst resource scarcity (United Nations, 2024). In response, the circular economy (CE) aims to reduce energy and resource consumption by fostering circular resource flows through value-retention strategies like reuse, remanufacturing, and recycling. (Ellen MacArthur Foundation, 2013). While conventional remanufacturing holds great potential due to the sustained integrity of product subsystems instead of circulating on material level (Reference Kurilova-Palisaitiene, Sundin and SakaoKurilova-Palisaitiene et al., 2023), practical challenges arise from secondary market dynamics, cannibalization and limited customer acceptance (Reference Arnold, Palomäki, Le Blévennec, Koop and GeerkenArnold et al., 2021) resulting in a adoption rate below its potential (Reference Parker, Riley, Robinson, Symington, Tewson, Jansson, Ramkumar and PeckParker et al., 2015). To address these challenges, the concept of Cross-Generational Remanufacturing (CG-Reman) has been defined as “planned and anticipated industrial process of restoring a used product/system from an older generation to a product/system of the latest generation with original as-new condition and performance [which is] offered on the primary market […]” (Reference Tusch, Jäckle, Albers, Malmqvist, Candi, Saemundsson, Bystrom and IsakssonTusch et al., 2024, p. 6). Our previous work has focused on selecting suitable product categories and identifying the most promising product subsystems (Reference Tusch, Pirc, Jäckle, Düser and AlbersTusch et al., 2025). This paper seeks to expand on the concept through a lifecycle description, derived requirements, and a foundation for methodological support in designing products and systems fit for CG-Reman. The latter is approached via a systematic review of Design-for-X (DfX) guidelines, which we selected and assessed for their suitability as design support for CG-Reman. DfX was selected for its ability to target specific engineering goals early in product development and its applicability and relevance in industrial practice (Reference Meerkamm, Wartzack, Bauer, Krehmer, Stockinger, Walter, Schleich, Rieg, Steinhilper and Alber-LaukantMeerkamm et al., 2018). The paper is organized as follows: Section 2 outlines the research background on (CG-)Remanufacturing and Design-for-X. Section 3 details the research approach. Section 4 presents the results, including a generic CG-Reman lifecycle, derived requirements, and exemplary guidelines. Finally, Section 5 summarizes and discusses the contributions while offering suggestions for future research.
2. Research background
2.1. From remanufacturing to cross-generational remanufacturing
As stated in the introduction, an especially promising R-strategy within the context of CE is given by remanufacturing (hereafter “conventional remanufacturing”), which has potential to retain product value by enabling components to undergo multiple full usage cycles and can outperform other circular strategies (Reference Tolio, Bernard, Colledani, Kara, Seliger, Duflou, Battaia and TakataKurilova-Palisaitiene et al., 2023; Reference Kurilova-Palisaitiene, Sundin and SakaoTolio et al., 2017). In conventional remanufacturing, used products (“cores”) are processed through several phases, which typically consist of disassembly, cleaning, inspection, restoring, reassembly and testing (Ijomah et al., Reference Ijomah, McMahon, Hammond and Newman2007a; Kauffman & Lee, Reference Kauffman and Lee2013; Steinhilper, Reference Steinhilper1998). These steps may vary depending on the specific industry or company (Reference Butzer and SchoetzButzer & Schoetz, 2016). However, conventional remanufacturing is limited by challenges such as product obsolescence, a lack of technological adaptability, and evolving customer requirements (Reference Aziz, Wahab, Ramli and AzhariAziz et al., 2016). The concept of Cross-Generational Remanufacturing (CG-Reman) was developed as one response to these challenges and describes a new strategy that aims to maximize the value retention from conventional remanufacturing by integrating used subsystems into new products for the primary market. This is addressed through a planned and anticipatory process that involves adapting and remanufacturing subsystems to meet the specifications of the latest product generation. The key idea is to provide full customer value without the risk of cannibalization and reduced resource utilization (Reference Tusch, Jäckle, Albers, Malmqvist, Candi, Saemundsson, Bystrom and IsakssonTusch et al., 2024). However, as of today it is crucial to address the operationalization gap of the concept. Hence, the development of design support for practitioners is required.
2.2. Design-for-X (DfX) and DfX frameworks
To address the complexity originating from multiple and often conflicting targets in product engineering, the idea of Design-for-X (DfX) has been established (Reference Kuo, Huang and ZhangKuo et al., 2001) based on the success of the early concepts of Design for Assembly (Reference Boothroyd and DewhurstBoothroyd & Dewhurst, 1983) and Design for Manufacture (Reference Stoll and DrozdaStoll, 1988). Today, Design-for-X is an umbrella term encompassing a wide range of design principles and methods aimed at helping designers optimize specific aspects of the product lifecycle (Ijomah et al., Reference Ijomah, McMahon, Hammond and Newman2007b; Mesa, Reference Mesa2023). Design-for-X approaches can be clustered along two dimensions: first, by the “X” they aim to optimize for, and second, by the nature of support offered. The “X” can represent either a specific phase of the product lifecycle, such as manufacturing or assembly (Reference van Doorsselaer and Koopmansvan Doorsselaer & Koopmans, 2021), or a desired product attribute (“virtue”), such as safety, quality, or cost (Reference Meerkamm, Wartzack, Bauer, Krehmer, Stockinger, Walter, Schleich, Rieg, Steinhilper and Alber-LaukantMeerkamm et al., 2018). The latter is sometimes referred to as Design-to-X (VDI, 2018). On the other hand, the nature of DfX support (Reference Arnette, Brewer and Choaloften referred to as “tools”, cf. Arnette et al., 2014) is subject to great variety, which can be explained by e.g. the lack of consistent standards for DfX (Reference Becker, Wits, Abramovici and StarkBecker & Wits, 2013). While other forms are existing, most approaches are found on guideline level. However, the application of individual DfX is often challenging, due to the large number of potential solutions (Reference Kuo, Huang and ZhangArnette et al., 2014; Reference Arnette, Brewer and ChoalKuo et al., 2001) as well as often conflicting interdependencies (Reference LindemannLindemann, 2007). One way to address some of the challenges is by combining multiple DfX either on concept or guideline level, which is essential for achieving optimal design solutions and sometimes referred to as “DfX frameworks (Reference Arnette, Brewer and ChoalArnette et al., 2014).
DfX has become the most relevant basis for qualitative tools in eco-design (Reference van Doorsselaer and Koopmansvan Doorsselaer & Koopmans, 2021). Consequently, within the context of circularity and conventional remanufacturing, various examples of DfX frameworks can be found in literature: Arnette et al. (Reference Arnette, Brewer and Choal2014) developed an integrated framework for Design for Sustainability, hierarchically organizing prominent DfX methods based on their interdependencies and aligning them with the three dimensions of sustainability: ecological, economic, and social equity. Charter and Gray (Reference Charter and Gray2008) introduced a Design for Multiple Lifecycles framework by combining various DfX methods, including Design for Cleaning, Product Reliability, Durability, and Remediation. Go et al. (Reference Go, Wahab and Hishamuddin2015) developed a Design for Multiple Lifecycle (MLC) framework by integrating guidelines from different lifecycle stages, such as Design for the Lifecycle, Design for the Environment, Recycling, Reuse, Remanufacturing, Disassembly, Assembly, Maintainability, Upgradability, and End-of-Life. Yang et al. (Reference Yang, Ong, Nee and Nee2015) proposed a Design for Remanufacturing framework by combining guidelines for Reverse Logistics, Disassembly, Sorting and Inspection, Cleaning, Reconditioning, Reassembly, and Testing. Hilton (Reference Hilton2021) developed a similar Design for Remanufacturing framework by clustering guidelines into newly formed DfX categories, such as Design for Integrated Value, Design for Viability, and Design for Active Prevention. Similarly, Pozo Arcos et al. (Reference Pozo Arcos, Balkenende, Bakker, Sundin, Marjanović, Štorga, Škec, Bojčetić and Pavković2018) established a Design for Circular Economy framework by integrating guidelines for Cleaning, Diagnosis, Disassembly, Reassembly, and Storage. While these existing frameworks at the guideline level are promising – and we adopted a similar approach by combining guidelines from selected DfX methods – they lack a specific cross-generational focus, which this study seeks to address.
3. Research objective and approach
With this paper, we aim to both further elaborate the previously proposed concept of CG-Reman and lay a foundation for engineering support to design suitable products and subsystems in the form of an initial list of DfX guidelines for CG-Reman, i.e. DfCG-Reman guidelines. To do so, it is necessary to take a lifecycle perspective, in line with existing similar research efforts (Reference Go, Wahab and Hishamuddine.g., Arnette et al., 2014; Reference Arnette, Brewer and ChoalGo et al., 2015). Based on a detailed analysis of the CG-Reman lifecycle we plan to derive requirements for CG-Reman-suitable products, which are then matched with existing DfX guidelines coming from a systematic literature review, cf. Figure 1
Figure 1. Research approach applied in this paper
This was methodologically guided by three research questions (RQs). First, since the CG-Reman lifecycle has not been described yet, a more thorough process description is addressed in our first RQ:
RQ1: How can a generic lifecycle process for CG-Reman be described to facilitate the derivation of design requirements?
To derive a process description, we identified 7 processes for linear phases and 10 remanufacturing process chains from literature, which we used as starting points to merge them to an end-to-end CG-Reman lifecycle process. From a detailed analysis of the identified process steps, we then needed to derive requirements for CG-Reman suitable (sub-)systems, leading to our second RQ:
RQ2: Which requirements for product design can be derived from the CG-Reman lifecycle?
This question was approached by conducting interviews with conventional remanufacturing experts from industry and academia in addition to an explorative literature search and analysis. Lastly, we needed to identify relevant DfX guidelines that might address the identified requirements. For this, we conducted a systematic literature review of the current DfX landscape guided by our third RQ:
RQ3: Which DfX guidelines currently exist and can support the design for CG-Reman?
As mentioned in chapter 2.2, the DfX research landscape in general is extensive, and in some cases provides only vague concepts with little or no depth at all. From 247 initially identified DfX terms gathered from review papers and standard reference works, only 118 yielded at least one actual publication containing the respective DfX name in its title using a script-based Scopus search (cf. Figure 1. From the terms with results, we subsequently did a first prioritization to identify 28 potentially relevant DfX (frameworks), such as Design for MLC, and eliminate those with an ”X“ of no relevance for CG-Reman (e.g., Design for 4D printing). Still, we also included 19 concepts that did not have initial results but seemed potentially relevant into a subsequent detailed combined systematic and explorative literature review. From screening 209 sources, we identified 51 sources that contained a total of 1610 individual guidelines. In a last step, we filtered this longlist for duplicates and relevance, added keywords and aggregated guidelines with similar content where applicable, leaving a remainder of 382 guidelines. These were then used to find matches for the identified requirements in RQ2.
4. Results
4.1. Generic cross-generational remanufacturing lifecycle
Based on a literature review of existing lifecycle descriptions for conventional remanufacturing, 10 sources could be identified and were analysed for their specific differences and common ground (Reference SteinhilperANSI, 2016; Bras, Reference Bras and Kutz2014; Butzer & Schoetz, Reference Butzer and Schoetz2016; DIN, 2023; Go et al., Reference Go, Wahab and Hishamuddin2015; Ijomah et al., Reference Ijomah, McMahon, Hammond and Newman2007b; IRP, 2018; Kauffman & Lee, Reference Kauffman and Lee2013; Parkinson & Thompson, 2003; Steinhilper, Reference Parkinson and Thompson1998). While most of these processes are relatively abstract in their description level, the intention here was to sketch a process with a sufficient level of detail to identify potential opportunities and pitfalls for product design. Hence, a lifecycle view of CG-Reman with five linear phases and seven (CG-)Reman phases was developed and selectively detailed where appropriate, cf. Figure 2. This was further refined by interviews with remanufacturing experts from industry. The key element for the CG-Reman process chain is the leap across generations (depicted by the two shaded rectangles), which is required for the forward-looking approach to circularity. The difference to conventional remanufacturing can also be seen visually in the figure, where a loop would be closed within the original (old) product generation. The process can be and should be targeted to be extended with more generational leaps (in theory indefinitely), albeit the complexity of the process and share of value retention will likely reduce correspondingly.
Figure 2. Overview of generic cross-generational remanufacturing lifecycle
The CG-Reman process consists of linear phases Material Extraction, Manufacture, Distribution, Use and End-of-Use (in this case not End-of-Life) in green, and the remanufacturing phases Core Collection, initial System Diagnosis, Disassembly, Cleaning and Subsystem Inspection in blue, which was synthesized from the literature quoted above. The process continues with the CG-Reprocessing phase, which crucially includes the CG-Adaption step (CG-phases in purple). Here, if required, the respective subsystem is altered to ensure compatibility for the new product generation after or while being functionally restored. Ideally, this stage can be omitted by an entirely communal subsystem design, however in reality, some functions, interfaces or joining mechanisms might require (planned) adaptions. Lastly, in the CG-Integration phase the restored and adapted subsystems are integrated with the linear assembly of primary market products. The pull-process of linear production complementing the circular process cannot be avoided due to two main reasons: First, for subsystems with no CG-Reman potential (planned change), and second, for subsystems where circular supply is smaller than the market demand of the new product. Even with constant market demand, some returned subsystems in bad condition (e.g., when the residual core value is smaller than the effort for restoration) will be aborted during the process and need to be processed through other R-strategies (e.g., Recycling). Due to the in-line integration of circular and linear production, it becomes obvious that the process is only feasible for the original manufacturer of the product and not for third-party entities. After finishing the assembly and respective final testing, products will experience another usage cycle in the new product generation.
Along the process the product is kept in its integrity until the Disassembly stage, before then being continued on subsystem level (red arrows). The disassembly needs to be conducted in cascading fashion, i.e. it should always be tried to salvage the entire subsystem before deciding to further disassemble. The re-assembly to a product of the new generation is part of the CG-Integration phase. Here, components that belonged to the same product in the old generation are not (necessarily) part of the same product in the new generation. Tracking the individual history of these instance-specific products is crucial, as subsystems with varying usage cycles must still meet primary market quality standards.
To the authors’ belief, this process requires anticipation and CG planning during the initial generation’s development, including deliberate selection of subsystems for CG-Reman (and potential exclusion, e.g. due to critical new functions of future product generations) as well as tracing and mitigating potentially conflicting future variations to these subsystems. Hence, the entirety of challenges that may arise during this extended lifecycle already needs to be considered in product engineering.
4.2. Requirements for cross-generational remanufacturing
The realization from Chapter 4.1 asked for specific requirements that need to be fulfilled during product engineering. To derive these, the lifecycle description was analysed step by step for resulting requirements for the product’s design. This meant, that general characteristics (e.g., “needs to be disassembled”) rather than optimization thereof (e.g., “efficient disassembly process”) were targeted. This process was supported by interviews with remanufacturing experts from the automotive industry (4 in-depth interviews) and academia (11 phase-specific interviews). Table 1 shows all identified requirements with their relevant lifecycle phases in chronological lifecycle order. Existing literature that stated similar requirements or notions for conventional remanufacturing were checked to ensure relevance and are added for reference, where applicable. We deliberately considered the entire process, even though a major part of the derived requirements (A-J) unsurprisingly has strong intersections with conventional remanufacturing. However, for the cross-generational case, the challenge is not only more complex through new requirements (K-M), but also the fulfilment of the conventional remanufacturing requirements becomes more complicated with potentially new guidelines to address these challenges.
Table 1. Overview of derived CG-Reman requirements in chronological lifecycle order
As an example, from the step of a potentially necessary CG-Adaption within CG-Reprocess phase, the requirement K can be derived. This is necessary, because in addition to pure functional restoration, the cross-generational approach requires either equal design of the respective subsystems in the two generations or the consideration of a possible adaption, which could also involve additional machining. Adjacent notions from the field of upgrading were used to refine the requirement (Reference Xing, Belusko, Luong and Abharye.g., Xing et al., 2007), even though coming from a different focus. While these requirements were deliberately kept solution-agnostic, they were used as an orientation for the subsequent DfX-guideline literature review.
4.3. DfX guidelines for cross-generational remanufacturing
Based on the identified requirements, existing DfX guidelines that might be able to support these were sought. With the systematic literature review described in Chapter 3, a condensed list of 382 aggregated guidelines could be derived. These guidelines were then manually matched to keywords as well as the respective process phases and the defined requirements A-M (cf. Chapter 4.2), resulting in 12 guideline packages. These were structured hierarchically, i.e. guidelines that would support or detail another guideline in the package were subordinated. Given the amount of guideline packages and guidelines, only excerpts of two examples of guideline packages A (addressing robustness) and K (existing guidelines addressing the need for cross-generational compatibility or adaption) can be presented here (truncations indicated by ”…“). The full set of guidelines can be obtained from the authors upon request.
As can be seen by the requirements and their corresponding process phases, most of the packages focus on steps also present in conventional remanufacturing and can hence be addressed by existing Design for Remanufacturing. Guideline package A is an example of such element, as robustness during the customer use phase is a common consideration also within existing Design for Remanufacturing frameworks. The guideline package synthesized from literature can be found in Table 2, while it combines both engineering design measures (A1) and influencing customer behavior (A2).
Table 2. (Aggregated) DfX guidelines from literature to address requirement A (Use).
More specific for the case of CG-Reman is guideline package K, which addresses the challenge of ensuring a planned compatibility or adaption possibility, cf. Table 3. This can be achieved either through reusing (focused by guidelines K1, K4) or adaption (K2, K3). Here, most guidelines that could be matched originate from the field of upgrading, which is conceptually different. While upgrading primarily addresses the subsystems that change across generations, here subsystems that remain constant but are still removed from the previous product integrity are addressed. Still, some of the guidelines provide valuable direction for product engineers to address the challenge.
Table 3. (Aggregated) DfX guidelines from literature to address requirement K (CG-Adaption).
While the approach to the identification of suitable guidelines was directed by a lifecycle-based requirements view, their application by product engineers demands a design-oriented perspective. When comparing the identified guidelines, different abstraction levels could be identified and were assigned: system-level guidelines (e.g., modularity) apply across the entire product and all subsystems, whereas subsystem/component-level guidelines (e.g., material requirements, internal disassembly) are specific to individual subsystems. In the core guideline packages shown above these abstraction levels are still mixed. However, given that in CG-Reman not all subsystems are maintained at a high value retention level but some are predesignated for alternative R-strategies (cf. Chapter 4.2), not all guidelines are relevant for all subsystems. Ways to identify subsystems with high CG-Reman potential were presented previously (Tusch et al. Reference Tusch, Pirc, Jäckle, Düser and Albers2025). Hence, we can split the scope of application of the identified guidelines based on the specific subsystem considered, cf. Figure 3.
Figure 3. Scope of application of the developed DfCG-Reman guideline packages
Additionally, supporting guideline packages that enhance the process but are not essential for CG-Reman (e.g., facilitating automated disassembly), were established. General requirements, that might be important for a successful product, such as optimization for efficient linear manufacturing and assembly as well as cost-efficiency further will contribute to a holistic approach and should be closely aligned.
5. Summary, discussion and outlook
This study explores Cross-Generational Remanufacturing, introducing a generic lifecycle (RQ1), high-level design requirements (RQ2), and initial DfCG-Reman guidelines synthesized from existing literature (RQ3). These contributions have been previously unexamined in the literature. Additionally, the proposed CG-Reman lifecycle offers a synthesized and more detailed process depiction of conventional remanufacturing steps, validated by industry experts. Our study moreover confirms prior findings (Reference Arnette, Brewer and Choale.g., Arnette et al., 2014) highlighting the lack of transparency in DfX approaches due to varying interpretations, inconsistent structures, and limited conceptual depth. In general, many of the circularity guidelines remain broad and repetitive, offering little specific advice for design.
The initial DfX guideline packages outlined in this study serve as a foundation for further development, particularly in refining specific guidelines for CG compatibility. However, they only represent an initial step towards a consistent DfX framework, as practical applicability (e.g, through case studies) has not yet been tested and language adjustments for clarity and coherence remain unaddressed. They also do not yet support upstream strategic decisions such as usage cycle lengths and generation time in market that might impact overall success or suitability of CG-Reman for a given product or company. To mitigate the inherent challenges of DfX frameworks, such as potential contradictions between individual DfX, this study established its initial framework at the guideline level, aiming to resolve direct conflicts within selected guideline packages. However, on the macro level (i.e., between guideline packages), this challenge from different and potentially conflicting requirements is still to be addressed. Hence, while providing a solid foundation for further methodological development, relying solely on existing DfX guidelines is likely inadequate. Instead, an integrated and holistic approach is needed, incorporating prioritization mechanisms like scoring, weighting, and relationship charts from the guideline level to aggregated decision-making. An example for such higher-level trade-off would be balancing the potential loss of recyclability at a subsystems’ EoL in favor of enhanced suitability for CG-Reman, i.e. on higher value retention levels. Given the complexity and both intra- and cross-generational interdependencies, a model-based engineering approach appears promising. These challenges will be further tackled as part of the CRC 1574 funded by the German Research Foundation (DFG), to further advance the design of forward-looking and cross-generational circular products.
Acknowledgements
This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – SFB 1574 – 471687386.
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