Co-Creating a Framework to Integrate Sustainable Design into Product Development Practice: Case Study at an Engineering Consultancy Firm

: There is a growing recognition of the need to incorporate sustainability considerations early-on in the product development (PD) process (PDP). As part of a case study at an engineering consultancy ﬁrm, this paper identiﬁes considerations that inﬂuence the integration of sustainable design practices into real-world PD practices. This is informed by the ﬁrst author becoming embedded in the ﬁrm as an intern, and closely observing the PD workﬂow across various projects, conducting interviews and group discussions with a wide range of practitioners, and iteratively designing and testing various potential interventions. From the literature and observations, we ﬁnd that designers and engineers often struggle to identify and apply the right sustainable design methods and tools (SDMTs) to tackle the environmental impacts associated with their products. Through a human-centered design process, we co-created a reusable, modular framework of practices that aids the selection of relevant strategies, based on the environmental hotspots, stage of the PD process, and the client’s sustainability priorities. Our prominent ﬁndings highlight the importance of: (a) co-creation in enhancing receptivity and retention, (b) the use of LCA iteratively to inform design decisions throughout PD, and (c) sharing case studies of successful application of the framework to promote sustainable design among employees and clients, alongside several other takeaways. The paper further presents insights related to the framework’s real-world application and impacts in the ﬁrm, based on results of longitudinal engagement with the ﬁrm.


Introduction 1.Motivation and Aims
Sustainable development has become an imperative topic of our time, gaining importance and public awareness since the hallmark Brundtland Report [1].Product innovation is now seen as one strategy to address systemic mega-risks that pose unprecedented challenges to companies and governments, including environmental threats [2], making sustainability an important consideration in product development (PD).Academic researchers and practitioners alike have, therefore, developed numerous sustainable design methods and tools (SDMTs) in recent decades.Early forms of sustainable design [3,4] focused primarily on redesigning individual qualities of products, such as improving an item's recyclability.Recent efforts have expanded in scope to look more broadly at the socio-technical system level of PD [5].However, industry practitioners often fail to utilize SDMTs as whole methods, but rather mix and match parts of different methods opportunistically [6], just as they do with traditional design methods [7,8].The framework created in this study accounts for such ad hoc approaches, as well as other considerations

•
An "activity" is something practitioners physically do (e.g., calculate, draw, etc.); • A "mindset" is something practitioners mentally consider (e.g., a goal, paradigm, etc.); • A "tool" is an object (physical or software) used to perform an activity and/or spur thought along a mindset; • A "method" is an ordered set of activities with accompanying mindsets; • A "strategy" is a mindset (or collection thereof) that may be accompanied by specific activities, or may be considered during normal design activities (e.g., brainstorming, cost estimation, etc.); • A "practice" generically refers to any and all design methods, activities, mindsets, tools, or combinations thereof; • A "practitioner" refers to designers, engineers, managers, or other stakeholders involved in industry product development decision-making and execution.
Further complicating matters, most practitioners lack training in sustainable design [13,14], and, therefore, struggle with both identifying the environmental effects of their products and with selecting the right strategies to improve those impacts.The existence of a vast variety of methods, strategies, and tools makes these choices harder.Additionally, there is growing agreement about the need to incorporate sustainability considerations early on in the PD process [15].The early phases are rife with uncertainties, however, as critical decisions (e.g., about the choice of materials, manufacturing processes, product architecture) have yet to be made [16].
Altogether, these challenges motivate the need for a modular, customizable, easy-touse approach if sustainability considerations are to be realistically integrated.To address this problem, we undertook research in partnership with an engineering consultancy firm.Through our case study, we aimed to (a) more deeply comprehend how sustainable design integration plays out in practice, (b) identify barriers and enablers to the integration, and (c) collaboratively develop a flexible framework that supports the translation of sustainable design practices into a real-world PD setting.Additionally, our human-centered design (HCD) approach to developing this framework placed our partner organization's context and needs at the center of the research.Specifically, the first author was embedded in the firm to observe the intricacies of their PDP.She conducted interviews, focus group sessions, and activities that helped co-create the novel framework.Beyond the framework itself, this paper also contributes insights regarding how this participatory approach can be more widely applied to offer generalizable utility for design researchers and practitioners seeking to implement interventions in other organizational contexts.

Background and Related Work
Prior work indicates that practitioners need support with identifying the right SDMTs for the job [13,14].Ref. [17] identified that multi-step methods are often not applied as tunnels of process, but that practitioners opportunistically skip steps or combine elements from various methods and tools.Since these less disciplined processes are more efficient in time and resources [8], our framework mainly allows for the selection of "strategies", which are constituent activities and mindsets or a combination thereof, rather than whole "methods" [6].The selection of strategies can be informed by the stage of the PD process [18,19], the life cycle stage it addresses [19][20][21], or the need for a quantitative or qualitative approach [11,18,22].We used the Checklist for Sustainable Product Development (CSPD) from [23] as our underlying theoretical framework.The CSPD uses "sustainability impact categories" (referred to as "focus areas" in this paper) based on the Design for Sustainability impact profile [24], the EcoDesign Checklist [25], and the Method for Sustainable Product Development [26].They assert that this organization affords practitioners an additional lever to identify strategies based on sustainability priorities.The CSPD, however, only uses qualitative SDMTs and is tailored to the automotive industry context.
We argue that the use of simplified life-cycle assessment (LCA) offers a lightweight, data-driven approach to select strategies based on the environmental impact hotspots identified, thereby maximizing the benefit [16].LCA is a method to evaluate the environmental impacts of a product throughout its life cycle, encompassing extraction and processing of raw materials, manufacturing, distribution, use, and final disposal [27,28].However, [27] pointed out that LCAs performed early on are impeded by limited knowledge of the product and other uncertainties, despite holding the greatest potential for improvement.This paradox can be tackled through the use of lightweight, simplified LCA tools tailored to the early-stage PD context [16], as well as an iterative application of LCA through the PD process to track the shrinking uncertainty as design decisions are made.
In this paper, we introduce a framework that guides users through the iterative selection and application of appropriate sustainable design strategies based on simplified LCA results, the stage of the PD process, and other specific client priorities.A systematic literature review by [29] on ecodesign implementation identified the organizational context as a critical factor.Ref. [30] highlighted that the "soft side", or the "human side" [31], can make or break ecodesign implementation.A large-scale survey conducted by [32] identified "management" as the biggest challenge to ecodesign implementation, closely followed by "collaboration", "strategy", and finally, "tools" and "knowledge".Similarly, [33,34] highlighted the importance of implementing a green organizational culture to achieve a sustainable competitive advantage.In this project, our human-centered approach combined participatory design [35] and co-creation [36] to help gain deeper insight into the human side through close observation, participation, interviews, and discussions, guiding the iterative design of the framework.Our study confirms that closely involving the users in the design process enhances acceptance of the framework [37].

Data-Collection Procedures
The development of our framework aims to support a structured yet flexible datadriven approach to sustainable design decision-making.Specifically, it guides the iterative selection of sustainable design strategies in the PD process using results from LCAs, along with client priorities.Key contributions of this paper include:

•
The iterative, human-centered, and collaborative co-creation process of a sustainable design framework tailored to employees' needs and the PD context; • A set of qualitative considerations, identified through extensive user research, which influence the adoption of sustainable design; • A co-created, modular framework of practices that satisfies these considerations and aids the systematic integration of sustainable design into PD workflows;

•
Insights and feedback related to the framework's deployment in practice, obtained through our longitudinal engagement.
We devised the following research questions (RQs) to guide our observation, interviews, and co-creation of the sustainable design framework with our case study partner: With these RQs in mind, Section 2 presents our methods to engage with our case study PD firm.Section 3 discusses insights from interviews, focus groups, and other captured data, with findings organized by emergent themes around incorporating sustainable design into PD.Section 4 discusses how these insights were collaboratively translated into a modular sustainable design framework, and revisits how this work answers our guiding RQs.We conclude with how the firm continues to employ the framework, and we outline future research opportunities.

Participants and Study Context
The industry partner selected for this case study was Synapse Product Development Inc. (referred to hereafter as "Synapse"), an engineering/design consultancy specializing in consumer electronics applications.We chose this firm for several reasons.First, the literature suggests that PD consultancies often lag manufacturing firms in terms of sustainability expertise [38,39] and, therefore, face a greater unmet need to integrate sustainability into their practice.Second, as an engineering consultancy, Synapse employees were comfortable working with both qualitative and quantitative methods, which enabled a variety of mixed methodologies to be considered during the co-creation process.Third, Synapse employees were very receptive to our research, owing to a growing interest in sustainable products among their clients, representative of a larger trend in the industry.In addition, Synapse and its clients struggled to identify the right SDMTs for their application, deliberating between numerous alternatives published in literature.Finally, Synapse had some familiarity but no deep expertise in sustainability, making it a representative case of how the introduction and integration of a sustainable design framework unfolds in real practice.This combination of factors made it an excellent case study for our research into how to effectively integrate SDMTs into PD practice.
Synapse has close to 150 employees in these main divisions: mechanical engineering, electrical engineering, firmware engineering, new product introduction (NPI), project management and a senior leadership team constituting the heads of all divisions.Project teams typically consist of 8-25 employees spanning across divisions.Project timelines range from six months to two years, based on the scope.Some clients require Synapse's support throughout the PD process, while others require them to contribute to just a specific stage of PD.
The first author worked with Synapse as a mechanical engineering intern for a period of four months and participated in the day-to-day PD workflow of the company.This enhanced the iterative design and testing of the sustainable design framework before arriving at the final version presented in this paper.Participants were recruited through cold emails sent to all employees at the firm in addition to direct referrals.In total, the researcher interacted with 25 employees spanning various divisions of the company, who volunteered to participate.Ten of them (3 female, 7 male), with work experience ranging from 4-21 years, were particularly active in contributing insights.Table A1 in Appendix A provides their full characteristics and anonymized identifiers.

Data-Collection Procedures
The first author worked alongside these participants to observe and understand their day-to-day PD workflow and what the integration of sustainability considerations meant for their practice.This was the central theme for most early interviews and group discussions, with insights gained from speaking largely to R1 and R2.Later sessions involved presenting variations of the framework to gather feedback and iteratively make refinements.By being embedded in the firm as an intern, the researcher established a rapport and trust with her colleagues so they could comfortably share both positive and negative feedback.

Interviews and Focus Groups
A total of 17 group discussions and four one-to-one semi-structured interviews with Synapse employees were conducted by the first author.Each session lasted an average of 45 min.Audio was recorded for transcription and analysis.In group discussions where recording was not possible, the first author made detailed notes including quotes of participants' comments.
Interviews explored questions about what incorporating sustainability within Synapse's PD practice meant to the employees in their different roles and divisions.P1 (firmware engineer), P2 (electrical engineer), P3 (NPI), and P5 (project manager) participated in 1:1 interviews.The 1:1 format allowed a deeper dive into what individuals valued or did not value about various aspects of the framework.
Group discussions involved presenting participants with versions of the framework and lists of relevant strategies identified from various methods and tools, seeking to gain their feedback.Discussions centered around specific aspects of the framework structure, what strategies from different SDMTs employees valued and why, and how the framework could be designed to be readily incorporated into the Synapse workflow.The first author moderated the discussions by asking questions and taking notes.Group sessions allowed the participants to exchange ideas and build on each other's arguments, highlighting instances of agreement and disagreement.Participants P4 and P6-P10 attended several discussions and actively contributed insights.Their roles spanned senior leadership, strategy consultancy, and engineering.

Project Documentation
As part of our investigation into Synapse's PD practice, the first author obtained access to documentation on past and current projects to better understand the company's PDP conventions and project workflows.She looked specifically at project timelines, milestones, frequency of client interactions, distribution of roles and responsibilities, and decisionmaking processes that altogether helped guide the creation of the framework for RQ3.

Participatory Development of the Sustainable Design Framework
We took an HCD approach to co-create a framework putting users' needs first and paid particular attention to making our framework useful and usable.We arrived at the final framework by closely observing the PD workflow across various projects, conducting interviews and group discussions with a wide range of practitioners, and iteratively designing and testing various potential interventions.User participation not only helps provide a deep insight into their needs but also enhances the acceptance of the outcome [37], which we observed over the course of our longitudinal engagement following the initial study.The participatory, collaborative, and iterative process is depicted in Figure 1.

Ongoing Engagement with the Company Post-Internship
We continued to engage closely with our partner company following the conclusion of the first author's internship.Specifically, through a total of 55 weekly follow-up Zoom sessions, amounting to 28 h of discussions over an additional year, we gathered feedback from teams that adopted the framework to learn how it could be further improved and made notes of key insights.During this longitudinal phase, we learned how the framework had since been applied to varying extents in four different projects, the most recent of which stemmed from a client reading a white paper that Synapse published about the framework [40].

Ongoing Engagement with the Company Post-Internship
We continued to engage closely with our partner company following the conclusion of the first author's internship.Specifically, through a total of 55 weekly follow-up Zoom sessions, amounting to 28 h of discussions over an additional year, we gathered feedback from teams that adopted the framework to learn how it could be further improved and made notes of key insights.During this longitudinal phase, we learned how the framework had since been applied to varying extents in four different projects, the most recent of which stemmed from a client reading a white paper that Synapse published about the framework [40].

Qualitative Data Analysis
Interview transcripts and group discussion notes were qualitatively coded to identify patterns and extract insights [41].The emergent themes describe key considerations we sought to address in the co-creation process.Table 1 in the Results section summarizes these high-level themes, together with sub-themes that reflect specific considerations.Access to internal and external resources for learning Making internally generated resources accessible and easy to use Improving the visualization and communication of LCA results Supporting the internal decision-making on trade-offs against cost, performance, etc.

RQ4: Long-term impacts
Applying the framework in practice Measure: Using LCA to identify hotspots Identify: Identifying relevant strategies in the repository Apply: Applying the identified strategies to improve the environmental performance of products

Results
Thematic analysis of the qualitative data collected led us to identify various themes and sub-themes critical to answering the research questions surrounding: (i) what drives receptivity toward incorporating SDMTs at a company, (ii) what SDMTs employees at this company valued and why, (iii) insights gained from participatory co-creation of the framework, and (iv) long-term impacts.Sections 3.1-3.4unpack the insights from the themes and sub-themes, organized by the research questions they address.

RQ1 (Receptivity): What Factors Drive Receptivity to Incorporating SDMTs into PD Practice?
The first research question concerns factors that facilitate or hinder the firm's receptivity to incorporating SDMTs into its PD workflow.The following subsections describe three key themes that emerged as indicators of receptivity: (1) organizational culture, (2) relationship with the client, and (3) the need to appeal to employees from different disciplines differently.We use participant quotes to contextualize our observations, demonstrating how our framework is grounded in participant inputs.This section helps provide a rich picture of the soft side of sustainable design implementation.

Integrating Sustainability into the Company Culture
During our interviews, Synapse employees emphasized the need to integrate sustainability not just into their PD workflow but also into their organizational culture.P8 indicated that discussions within teams and clients needed to include sustainability indicators alongside the cost and engineering performance, to emphasize "sustainability and social impact as something that [Synapse] is integrating into our DNA".This sentiment around responsible innovation was echoed by several other participants, including P1 who expressed a desire for Synapse to "focus on social and ethical considerations" in addition to environmental ones.
We started by trying to define what sustainable design meant for Synapse, both to eliminate ambiguity and build ownership and commitment.After brainstorming with the senior leadership and coming up with several versions, and getting feedback from other employees, we landed on: "sustainable design at Synapse focuses on maximizing environmental, social, and economic benefits over a system's life cycle, while minimizing associated social and environmental costs".Once there was agreement across the board on this, several questions arose, including: "Who owns the sustainability aspects of the project?", "How do we define the metrics for success?","When do we know we are done?", and "Can we track sustainability metrics the way we track cost?" Participants felt that the project managers (PMs) should track sustainability tasks and metrics as they track engineering tasks and metrics.PMs were found to be a key stakeholder in sustainability integration because they form the interface between the client and the engineers, translating client needs into project requirements.Despite Synapse's dedication to incorporating sustainability into its PDP, the firm is somewhat limited as a consultancy, given it can only make recommendations that must ultimately be approved by its clients.However, P6 expressed optimism that "as more companies commit to sustainability targets, this will start to be the norm and not the exception", a sentiment core to the continued incorporation of the framework in practice.

Relationships with Clients and Stakeholders
Building on this theme, our interviews further explored where sustainability fits in the client-consultant negotiations, and how client buy-in can prove to be critical for integration.
Interviews identified the delicacy of communicating the value of sustainable design to clients.P5, a PM who is often the interface between a PD team and the client, said, "they come to consultancies like Synapse because they need engineering support . . . it is easy for [Synapse] to sell them on the immediate value of engineering services but might not be easy to sell on the value of going through this [sustainable design] exercise".This was especially true for clients who had not set sustainability targets.Furthermore, adopting sustainable design practices inevitably adds time, which can be seen as a drawback by clients because they are paying for consulting services by the hour.P5 indicated that clients were typically looking for the "best bang for their buck", and sustainability may not always be their priority.Thus, to accelerate adoption, participants perceived value in minimizing the time spent on sustainable design.
P5 described client satisfaction as the "delta between what they get and what they expect".These insights emphasize the importance of predictably delivering on expectations to build a strong long-term relationship with the client.We identified the need for transparency and accuracy with estimating the time and other resources required, leading us to label strategies as "low", "medium", or "high" effort.Such estimation could eliminate process uncertainties, both for clients and employees, potentially improving receptivity.Identifying low-versus high-effort strategies also helps trade-off the operational cost-benefit.P5 reminded us that Synapse deals with a "wide range of clients, and some really care about [sustainability], while others have it way down low on their priority list".He said it was important to get the fundamental message across "without getting stuck in the weeds".P7 added that "sustainability was previously perceived as being at the expense of profitability, but recent models have shown that actually, sustainable business models are better in many cases".Case studies can be an effective way to convey the value of considering sustainability in PD practice, an approach currently employed by Synapse's New Product Introduction (NPI) team to promote design-for-manufacturability, as described further in Section 3.1.3.This highlights how finding ways to better communicate the value of sustainable design, such as with the use of case studies, leads to receptivity and long-term integration of strategies.
We also recognized the importance of understanding the factors motivating a client's receptivity to sustainability and, therefore, the SDMTs they value, in doing so addressing the tools valued in conjunction with integration.P9, a strategy consultant, explained that "a client's sustainability needs are often either regulation-driven or market-driven" and that she was seeing "FMCG [fast-moving consumer goods] companies in the EU focusing on minimizing plastic use, driven by stricter regulations".Organizing sustainable design strategies/methods in the Synapse repository according to the UNEP Design for Sustainability Guide's focus areas (listed in Section 3.2.2) provides Synapse employees a structured format to explore where the biggest environmental benefits lie and help clients set or modify their sustainability priorities.It also allows their clients to market their product as having specific benefits over their competitors.The focus areas support constructive engagement with the client on environmental impacts in vocabulary familiar to them, potentially enabling buy-in.
We recommended that these conversations start in the early project-scoping stages, followed by periodic check-ins where sustainability performance is reviewed alongside other engineering performance indicators.P7 agreed that it was important to "get clients involved as early as possible, because that's when we can have the biggest impact".This approach enables Synapse to help clients set appropriate high-level sustainability goals, set relevant objectives for the project, and track key performance indicators over the course of the PD process.

Discipline-Specific Insights
Conversations with a diverse range of participants showed that their receptivity and perspectives on sustainability were uniquely shaped by their roles and disciplines at Synapse.For instance, project managers (PMs) at Synapse have the most interaction with the clients, while also managing the project scoping, timelines, and workflow.P5, who was a PM, agreed that it was his job to identify the "areas to focus on throughout the product design process" largely through periodic conversations with the client.He expressed that it was also his purview to "minimize the overhead time that it takes to do [LCA] in terms of using lightweight tools".He was keen on optimizing the sustainable product design process, asking, "How do we have the biggest impact with the least time and resources?"As discussed further in Section 3.2.2, this led us to prioritize the use of simplified (lightweight) LCA tools for periodic assessments, enhancing their integration in both the short and long terms.
The NPI engineer (P3) oversaw the firm's design-for-manufacturability efforts and could empathize with the difficulty in communicating the value of incorporating sustainability early in the PDP.He said, "NPI engineers work hard to convince clients of the value of including a manufacturing engineer on the team early on".To overcome this, he said they often point to case studies where a prototype was deemed "not manufacturable" too late in the process, adding tremendous costs that could have been avoided.To improve both receptivity and long-term adoption, we also recommended compiling such case studies to demonstrate more tangibly to clients the value of sustainable design.
P1, a firmware engineer, did not think that incorporating sustainable design would affect his workflow much, as he saw it as "mechanical, electrical, and NPI heavy".He added that their division was typically "not involved in the early product design decisions".Interestingly, he pointed out that they already followed practices that could be considered sustainable, such as "maximizing battery life, reducing power consumption, seeking tier-1 chip manufacturers, and future-proofing by using technology that might not become obsolete in the near future".He clarified that such strategies were motivated by economic and engineering considerations.This helped us recognize how professionals can appreciate and adopt sustainable practices for their economic and engineering performance benefits.

RQ2 (Tools Valued): What do Practitioners Value in Existing Sustainable Design Methods and Tools (SDMTs)?
The second research question addresses which SDMTs the employees at Synapse valued or did not value, and why.The following subsections describe how this led to: (1) the compilation of a list of SDMTs valuable to Synapse's context, and (2) how these SDMTs were organized into a larger, repeatable framework to support their selection and application.

Compiling Relevant Strategies
This involved compiling a list of sustainable design strategies that were individual activities, mindsets, or a combination thereof, to form strategies, from existing SDMTs in the literature.This approach was based on the idea that "multi-step methods are often not applied as tunnels of process in practice" [9].Synapse employees confirmed that they often used parts of methods as opposed to applying whole methods as prescribed.
Table 2 depicts the methods and tools considered and/or selected to be included in our compiled list of strategies.We ensured that they addressed all three pillars of sustainability (environmental, social, and economic), and they spanned a diverse range of methods (qualitative, semi-quantitative, and quantitative, as well as product-level and system-level).Decisions to include a certain strategy in the final list were made through discussions on what strategies were found to be valuable or not valuable, and why, as specified in the table.We discussed the individual activities/mindsets within each of the methods described in Table 2 with participants P4, P6, and P10, and narrowed down the list to the final version presented in Section 3.3.1.Several strategies were eliminated based on repetition/overlap with those in other methods listed prior.Furthermore, many strategies were not valued because they were not within Synapse's typical scope of influence on a project, as expressed by P10: "Synapse typically has the biggest impact on material selection and product design; packaging/distribution are rarely something we can influence".Such perceptions around scope of influence heavily impacted what strategies participants valued.

Foundation for the Framework Structure
We now created a framework structure to allow users to select the right sustainable design strategy for the job iteratively through a project (Figure 2).Our framework starts with an early-stage "Innovate" step that encourages users to explore and brainstorm interventions at the system-level.As the product/system idea is solidified, users are encouraged to perform a quick, simplified LCA to identify hotspots by the life-cycle stage, allowing users to target the sources of biggest impact.Users perform the steps "measure impacts", "identify hotspots", and "apply relevant strategies" iteratively throughout the PD process.Incrementally, the uncertainties associated with performing LCA early on shrink over time.The existing Synapse PDP follows a stage-gate process with the following stages: (1) Discover, (2) Define, (3) Develop, (4) Evolve, (5) Realize, and (6) Support.We observed that while there was an emphasis on iteration between phases, there was also a fast-paced progression through the phases to meet tight timelines.The value of iteratively applying the process and tracking indicators over time was articulated well by P8: "Most of these strategies need to be implemented in a periodic fashion.Materials/processes may change later, and we would still need to review if, for instance, they are conflict minerals or health risks posed."Overall, the iterative nature of our framework's sustainable design process goes hand-in-hand with an iterative PD process, thereby enhancing the integration of the activities.P5 and P6 suggested tracking and visualizing sustainability KPIs alongside cost and other engineering KPIs: "can we track environmental impacts in the same way that cost is tracked as design is refined?"P6 further suggested "tracking the narrowing of uncertainty in LCA BOM input".Participants wished to periodically track KPIs during the PD process, including when negotiating tradeoffs with clients.

RQ3 (Co-Creation): How does Co-Creating a Framework with Employees Enable Long-Term Integration?
In this section, we discuss the advantages of collaboratively creating the framework with our industry partners.The development of the framework underwent several iterations based on periodic feedback obtained through observation, interviews, and discussions to align it effectively with the firm's fast-paced, iterative PD workflow, as summarized in Figure 3: Sections 3.3.1 and 3.3.2highlight key insights regarding the usability of the framework identified through the co-creation process: (1) better aiding the selection of strategies, and (2) including early-stage system-level innovation.These considerations emerged from the collaborative design of the framework, as will be outlined.The value of iteratively applying the process and tracking indicators over time was articulated well by P8: "Most of these strategies need to be implemented in a periodic fashion.Materials/processes may change later, and we would still need to review if, for instance, they are conflict minerals or health risks posed."Overall, the iterative nature of our framework's sustainable design process goes hand-in-hand with an iterative PD process, thereby enhancing the integration of the activities.P5 and P6 suggested tracking and visualizing sustainability KPIs alongside cost and other engineering KPIs: "can we track environmental impacts in the same way that cost is tracked as design is refined?"P6 further suggested "tracking the narrowing of uncertainty in LCA BOM input".Participants wished to periodically track KPIs during the PD process, including when negotiating tradeoffs with clients.

RQ3 (Co-Creation): How does Co-Creating a Framework with Employees Enable Long-Term Integration?
In this section, we discuss the advantages of collaboratively creating the framework with our industry partners.The development of the framework underwent several iterations based on periodic feedback obtained through observation, interviews, and discussions to align it effectively with the firm's fast-paced, iterative PD workflow, as summarized in Figure 3:

Organizing Strategies by Life-Cycle Stage, PD Phase, and Focus Areas to Aid Selection
A critical insight from the participant observation was that users were looking for a structured decision support framework to help with selecting the right strategies.Our cocreation focused on what levers we could provide to enable easy, logical, and reproducible decision-making.This led to discussing how to organize and tag the final list of compiled strategies selected from existing SDMTs.This list is not exhaustive and is expected to grow as the framework is used.Nonetheless, we ensured that the strategies addressed the nine sustainability focus areas similar to those used by [23], including: (1) resource efficiency, (2) resource consumption, (3) selection of low-impact materials, (4) optimizing end-of-life, (5) lowering negative environmental impacts from waste, (6) transportation and logistics, (7) health and safety, (8) social and ethical considerations, and (9) economic efficiency and profitability; these were based mainly on the UNEP Design for Sustainability impact profile [24].We found that these focus areas could be correlated to the triple bottom line: the environmental, social, and economic pillars of sustainability, as illustrated in Figure 3. Table A2 in Appendix A includes the grouping of strategies by these focus areas.
Sorting the strategies by the sustainability focus areas allowed users to narrow down relevant strategies based on the client's priorities.This approach during co-creation helped us ensure that the compiled strategies addressed environmental, economic, and social aspects-a priority for Synapse employees, as discussed in Section 3.2.1.The strategies were then organized by the life-cycle stages (materials and manufacturing, distribution, use, and end-of-life) to which they best applies, allowing users to select strategies based on the life-cycle stages that contributed to the most environmental impacts (based on LCA results).We further linked strategies to the PD phases where they apply.For example, the strategy "avoid conflict minerals" best applies to the materials and manufacturing stage of the product's life cycle, in the "discover" and "define" phases of the PD process.Figure 4 details the correlation of the strategies to the life-cycle stages, PD phases, and the triple bottom line.Offering multiple levers to simplify the identification of relevant strategies was found to be valued both empirically and in the literature, to enhance the integration.Figure 5 is the final list of strategies found to be valuable from the SDMTs (2) including early-stage system-level innovation.These considerations emerged from the collaborative design of the framework, as will be outlined.

Organizing Strategies by Life-Cycle Stage, PD Phase, and Focus Areas to Aid Selection
A critical insight from the participant observation was that users were looking for a structured decision support framework to help with selecting the right strategies.Our cocreation focused on what levers we could provide to enable easy, logical, and reproducible decision-making.This led to discussing how to organize and tag the final list of compiled strategies selected from existing SDMTs.This list is not exhaustive and is expected to grow as the framework is used.Nonetheless, we ensured that the strategies addressed the nine sustainability focus areas similar to those used by [23], including: (1) resource efficiency, (2) resource consumption, (3) selection of low-impact materials, (4) optimizing end-of-life, (5) lowering negative environmental impacts from waste, (6) transportation and logistics, (7) health and safety, (8) social and ethical considerations, and ( 9) economic efficiency and profitability; these were based mainly on the UNEP Design for Sustainability impact profile [24].We found that these focus areas could be correlated to the triple bottom line: the environmental, social, and economic pillars of sustainability, as illustrated in Figure 3. Table A2 in Appendix A includes the grouping of strategies by these focus areas.
Sorting the strategies by the sustainability focus areas allowed users to narrow down relevant strategies based on the client's priorities.This approach during co-creation helped us ensure that the compiled strategies addressed environmental, economic, and social aspects-a priority for Synapse employees, as discussed in Section 3.2.1.The strategies were then organized by the life-cycle stages (materials and manufacturing, distribution, use, and end-of-life) to which they best applies, allowing users to select strategies based on the life-cycle stages that contributed to the most environmental impacts (based on LCA results).We further linked strategies to the PD phases where they apply.For example, the strategy "avoid conflict minerals" best applies to the materials and manufacturing stage of the product's life cycle, in the "discover" and "define" phases of the PD process.Figure 4 details the correlation of the strategies to the life-cycle stages, PD phases, and the triple bottom line.Offering multiple levers to simplify the identification of relevant strategies was found to be valued both empirically and in the literature, to enhance the integration.Figure 5 is the final list of strategies found to be valuable from the SDMTs introduced to the Synapse employees in Table 2.This list is not exhaustive, and is expected to grow and change as the framework is applied over time.
Sustainability 2022, 14, x FOR PEER REVIEW 14 of 25 introduced to the Synapse employees in Table 2.This list is not exhaustive, and is expected to grow and change as the framework is applied over time.The framework document included additional information for each strategy for reference, based on what kind of information participants found valuable.For instance, P8 suggested including "knowledge gap questions", P5 suggested including the "estimated time to apply a strategy", and others asked for "links to external references".P10 responded to an initial version with, "it is too dry; it could use more images", while P5 asked for "cheat sheets" that would help him quickly glean relevant information.P10 wanted us to include "case studies and real-world examples".Figure 6 is an example of how these content suggestions were incorporated into the document to support the framework's adoption.The content is expected to grow as more teams learn and apply the strategies.

Applying the Overall Framework in PD Practice
Participants described the iterative nature of PD, and the need to periodically discuss decisions and considerations with clients.This led us to use an iterative four-step process that is repeated throughout the PDP.The early stage "Innovate" step involves users initiating discussions about sustainability priorities during early scoping conversations with clients.This helps identify specific sustainability focus areas, offering a lever to narrow down to relevant strategies.If the client does not have pre-existing sustainability priorities, the focus areas offer a structure for discussion.The "Innovate" step recommends the optional use of system-level methods and tools such as: the 12 Leverage Points, System Mapping, and the Circular Design Guide to explore system-level innovation before a product/system idea is pursued.Once a product/system idea is solidified, following concept generation, the framework next scaffolds users to start to "measure" the environmental impacts of concepts using simplified LCA tools.These assessments lead to the next step, which is to "identify" life-cycle stage(s) that contribute to the most environmental impacts.This information helps practitioners select appropriate strategies to "apply" based on the life-cycle stage, sustainability focus areas, and the PDP phase.
For instance, if the user identifies that the materials and manufacturing stage of the product contributes to the most impact, they will narrow down to strategies corresponding to that particular life-cycle stage that also best apply to the PD phase they are in Figure 7 details the overall process flowchart, illustrating the iterative measure-identify-apply steps applied in parallel with the PD process.Measuring impacts provides a quantitative basis for selecting strategies to maximize a product's environmental performance.The inherent uncertainties associated with performing LCA early on shrink over time as the product progresses through the PD process and the inputs to such assessments become more concrete.to apply a strategy", and others asked for "links to external references".P10 responded to an initial version with, "it is too dry; it could use more images", while P5 asked for "cheat sheets" that would help him quickly glean relevant information.P10 wanted us to include "case studies and real-world examples".Figure 6 is an example of how these content suggestions were incorporated into the document to support the framework's adoption.The content is expected to grow as more teams learn and apply the strategies.

Applying the Overall Framework in PD Practice
Participants described the iterative nature of PD, and the need to periodically discuss decisions and considerations with clients.This led us to use an iterative four-step process that is repeated throughout the PDP.The early stage "Innovate" step involves users initiating discussions about sustainability priorities during early scoping conversations with clients.This helps identify specific sustainability focus areas, offering a lever to narrow down to relevant strategies.If the client does not have pre-existing sustainability priorities, the focus areas offer a structure for discussion.The "Innovate" step recommends the optional use of system-level methods and tools such as: the 12 Leverage Points, System Mapping, and the Circular Design Guide to explore system-level innovation before a product/system idea is pursued.Once a product/system idea is solidified, following

RQ3 (Long-Term Impacts)
We continued to engage closely with Synapse following the conclusion of the first author's internship.Through 55 weekly follow-up Zoom sessions amounting to 28 h of discussions over an additional year, we gathered feedback from teams that adopted the framework, to learn how it could be further improved, making notes of key insights.During this longitudinal phase, we learned how the framework has since been applied to varying extents in four different projects, the most recent of which was a result of a client reading a white paper that Synapse published about the framework [40].These projects ranged across industries, including personal care, apparel, and home appliances, and involved the use of LCA to guide the selection of sustainable design strategies.Results showed that the products thus generated were more sustainable.Images from Synapse's marketing material (see Figure 8a-c) demonstrate the project, sustainable design methods applied, and the resulting improvement in environmental impacts.
Other insights gained from the longitudinal interactions with Synapse are summarized below:

•
Personal interest among Synapse employees has been a strong driving force for the integration of sustainable design into their PD process.Leadership support has been an added boost; • Due to the additional time and effort involved, Program Managers and Business Developers feel hesitant to pitch sustainable design to clients upfront for fear of losing the contract; • Limited publicity of Synapse's new sustainable design capabilities leaves many clients unaware of the offering in advance;

•
It is yet to become a default part of every single project, with most managers waiting for clients to request sustainable design services first; • Synapse leadership believes that positive marketing stories, resulting in greater client enthusiasm, are the external stimulus necessary to make sustainable design a habit.They are encouraged by having had four sustainable-design-focused projects over the past two years and are hopeful that the numbers will rise.
mental impacts of concepts using simplified LCA tools.These assessments lead to the next step, which is to "identify" life-cycle stage(s) that contribute to the most environmental impacts.This information helps practitioners select appropriate strategies to "apply" based on the life-cycle stage, sustainability focus areas, and the PDP phase.
For instance, if the user identifies that the materials and manufacturing stage of the product contributes to the most impact, they will narrow down to strategies corresponding to that particular life-cycle stage that also best apply to the PD phase they are in.Figure 7 details the overall process flowchart, illustrating the iterative measure-identify-apply steps applied in parallel with the PD process.Measuring impacts provides a quantitative basis for selecting strategies to maximize a product's environmental performance.The inherent uncertainties associated with performing LCA early on shrink over time as the product progresses through the PD process and the inputs to such assessments become more concrete.It is yet to become a default part of every single project, with most managers waiting for clients to request sustainable design services first; • Synapse leadership believes that positive marketing stories, resulting in greater client enthusiasm, are the external stimulus necessary to make sustainable design a habit.They are encouraged by having had four sustainable-design-focused projects over the past two years and are hopeful that the numbers will rise.

Discussion
We have so far described the evolution of the sustainable design framework, with its components co-created in close consultation with our case study partners, and the ways it has been applied in practice, along with instances of its application with real clients over the past year.We conclude now by synthesizing how these findings address our research questions.

Synthesizing Insights around Our Research Questions
As denoted throughout the Results section, the insights discovered through interviews and discussions helped answer our research questions and informed the sustainable design framework.We synthesize our findings by outlining how they relate to each research question in Table 3.

Discussion
We have so far described the evolution of the sustainable design framework, with its components co-created in close consultation with our case study partners, and the ways it has been applied in practice, along with instances of its application with real clients over the past year.We conclude now by synthesizing how these findings address our research questions.

Synthesizing Insights around Our Research Questions
As denoted throughout the Results section, the insights discovered through interviews and discussions helped answer our research questions and informed the sustainable design framework.We synthesize our findings by outlining how they relate to each research question in Table 3. Helped identify SDMTs most relevant to the company's context Helped align the framework with the dynamic and iterative nature of PD Helped gather insights from employees from various divisions and backgrounds Helped participants build ownership of and want to champion the framework they created (RQ4) Long-term impacts: How does the framework support continued consideration of sustainability in the company's PD practice over time, or if it fails to do so, why?
Communicating the value of sustainable design both internally and externally Helping clients identify their sustainability priorities Publishing case studies on how the framework helped enable the sustainable design transition Our first research question aimed to understand attitudes toward integrating new sustainable practices in the first place, RQ1: What factors drive the company's receptivity to incorporating new SDMTs into their practice?Synapse employees were very open to our research and willingly took part in user interviews and discussions.They were keen for a new framework that would allow them to systematically consider sustainability in their practice.Several participants expressed a personal interest in and passion for sustainability.There was also a recognition among employees and the leadership that a majority of their consumer electronics products ended up in landfills.We saw this company-wide inclination toward sustainability align with a growing interest among their clients to develop more sustainable products and services.
Next, we investigated perceived benefits and costs of extant sustainability practices, RQ2: What do professionals value in existing SDMTs?We found that professionals often used elements from different methods and tools, based on the problem at hand as well as the time and resource constraints faced during the PDP.Given the wide variety of existing SDMTs, they needed this support to be systematic yet adaptable in identifying the right strategy for the job throughout this process.Employees also expressed the desire to focus not just on the environmental aspects but also on the social and economic aspects of sustainability.
We were especially interested in exploring the advantages of collaboratively creating the framework with our industry partners, RQ3: How does the process of co-creating a customized sustainable design framework better support its integration into the company's PD practice?Facilitated by the first author embedded in the company as an intern, co-creation allowed us to gain a deep understanding of the partner's PD process, collaboratively prototype versions of the framework, and gather detailed feedback on it through interviews and group discussions.This participatory approach improved our participants' agency, buy-in, and the ultimate efficacy of the solutions produced.Our experience indicates that co-creation helped promote the continued application of the framework in practice following the completion of the study.
Finally, we sought to assess the framework's longitudinal impacts on PD practice, RQ4: How does the framework help to maintain the consideration of sustainability as part of the company's PD practice over time, or if it fails to do so, why?To address this question, we continued to communicate with the company for a year after the framework was developed, learning how it had been applied on projects and the refinements made since.For example, their work on a recent project led them to expand on the early stage Innovate section by including additional worksheets.The company found employing the framework to be beneficial; P6 said the framework supported a "streamlined integration of sustainable design into their PD process".P4 concurred that the structured framework helped them save time.
We expect the following aspects of the framework to remain generalizable across different PD contexts in other industries:

•
The use of LCA early on and periodically through the PD process to inform the selection of specific strategies to apply;

•
The set of SDMTs reviewed to help identify the strategies relevant to the industry context.This set spanned qualitative to quantitative, as well as product-level to system-level SDMTs;

•
The use of life-cycle stages and sustainability focus areas as levers for users to narrow down to the most relevant strategies; • Using the iterative co-creation process described in Figure 1 to help tailor the set of relevant strategies to the company and industry context.
Overall, the framework is expected to grow and change as it is applied to more projects.A broader motivation, as pointed out by participants, is for sustainable design integration to be the norm and not the exception.Synapse, therefore, has published and widely shared white papers on this framework through panel discussion events and platforms such as LinkedIn, to: (a) encourage other companies in different industries to try the approach and test its generalizability, and (b) attract more clients keen on developing more sustainable products and services.

Limitations and Opportunities for Future Work
Our case study partner reported on the framework in a white paper, to encourage additional companies to adopt and provide experiences with the approaches.They have so far received positive feedback from companies in other industries, suggesting the generalizability to other PD contexts beyond consumer electronics.We believe that the iterative human-centered approach used to co-create the framework with the employees is a key generalizable takeaway for academics and professionals working in sustainability.Yet, an important limitation of the framework is that this specific shortlist of SDMTs compiled for Synapse cannot necessarily be used directly in other industry contexts; instead, it may need case-specific tailoring and co-creation.However, this approach has been shown to help with receptivity and retention.An important next step is to systematically test the utility of the framework on a broader scale.We are, therefore, currently conducting a new study at a company in a different industry to better understand the broader application of the framework, including how it may translate from a consulting firm to a product firm.Further to this, we predominantly applied qualitative methods to deeply engage stakeholders in our Synapse case study, to gather a rich, highly contextualized dataset about their experiences and needs.While these participants spanned a variety of disciplines, roles, and levels of seniority, it was a relatively small-scape sample.This limitation motivates our future work with larger companies and other industries to gather more varied quantitative data and triangulate the insights through mixed methods.

Conclusions
This paper explored how sustainable design practices can be systematically integrated in the PD process at an engineering consultancy firm.The first part of our study involved the first author being embedded into the firm as an intern, to better understand their PD workflow and build trust and rapport with the participants.During this time, she conducted semi-structured interviews and group discussions to gain deeper insight into their processes, and to co-create a modular sustainable design framework that could be flexibly applied to suit the firm's context and needs.The second part of the study involved weekly check-ins for a period of over a year, to follow the company's application and adaptation of the framework to serve four actual PD projects.This longitudinal engagement enabled us to evaluate the effectiveness of the framework in supporting the integration of sustainability considerations in practice, including to gather feedback and implications for how to improve the framework going forward.
In summary, the sustainable design framework presented in this paper provides a structure to enable the effective consideration of sustainability throughout PD.Co-created with practitioners, the framework follows an iterative process of measuring impacts via LCA, identifying hotspots, and applying appropriate strategies (activities and mindsets) from a compiled list of SDMTs that we identified as relevant and valuable to the company context.The framework organizes the list of strategies in terms of the most salient PD phases and life-cycle stages, thereby offering multiple levers for selection.Basing the selection of strategies on the hotspots identified through simplified LCA adds a datadriven perspective.Flexibility is further supported by allowing users to pick one or more strategies from various SDMTs, as opposed to having to apply a single method as a tunnel process.The strategies are also correlated to various sustainability focus areas, to allow users to make choices based on a client's sustainability priorities, additionally creating an opportunity for discussion of priorities if such priorities are yet to be identified.Overall, we look forward to the continued dissemination of our newly contributed framework, co-creation methods, and broader insights to support the translation of sustainable design research into industry practice.

Figure 1 .
Figure 1.The participatory process applied to answer our research questions and co-create the sustainable design framework.

Figure 1 .
Figure 1.The participatory process applied to answer our research questions and co-create the sustainable design framework.

Figure 2 .
Figure 2. The framework's sustainable design stages (red) are applied iteratively, in parallel with the PD process (gray).

Figure 2 .
Figure 2. The framework's sustainable design stages (red) are applied iteratively, in parallel with the PD process (gray).

Figure 3 .
Figure 3. Various iterations of the framework's design.

Figure 3 .
Figure 3. Various iterations of the framework's design.Sections 3.3.1 and 3.3.2highlight key insights regarding the usability of the framework identified through the co-creation process: (1) better aiding the selection of strategies, and(2) including early-stage system-level innovation.These considerations emerged from the collaborative design of the framework, as will be outlined.

Figure 4 .
Figure 4. Connecting the sustainability focus areas to the triple bottom line.This helped us address all three pillars of sustainability.Figure 4. Connecting the sustainability focus areas to the triple bottom line.This helped us address all three pillars of sustainability.

Figure 4 .
Figure 4. Connecting the sustainability focus areas to the triple bottom line.This helped us address all three pillars of sustainability.Figure 4. Connecting the sustainability focus areas to the triple bottom line.This helped us address all three pillars of sustainability.

Figure 4 .
Figure 4. Connecting the sustainability focus areas to the triple bottom line.This helped us address all three pillars of sustainability.

Figure 5 .
Figure 5. Final list of strategies comprising activities/mindsets from existing SDMTs that were found to be relevant and valuable to our participants.

Figure 6 .
Figure 6.Summary page for each strategy provides key information to support its application.

Figure 6 .
Figure 6.Summary page for each strategy provides key information to support its application.

Figure 7 .
Figure 7. Flowchart detailing the process of applying the sustainable design framework.Figure 7. Flowchart detailing the process of applying the sustainable design framework.

Figure 7 .Figure 8 .
Figure 7. Flowchart detailing the process of applying the sustainable design framework.Figure 7. Flowchart detailing the process of applying the sustainable design framework.

Figure 8 .
Figure 8. (a-c) Synapse marketing slides from three projects that applied the sustainable design framework, all of which showed a reduction in environmental impacts.

Table 1 .
Themes and sub-themes that emerged from our qualitative analysis of interviews and focus group discussions.

Table 2 .
SDMTs considered and/or selected to be included in the framework.

Table 3 .
Insights organized by research questions.

Table A2 .
Grouping of sustainable design strategies by the sustainability focus areas they address, along with the triple bottom line.Mitigate health and safety risks of end-of-life strategyxEnsure that failure modes and the associated health and safety risks are identified, mitigated, and communicatedx Identify and communicate health and safety risks to all stakeholders in the distribution networkSocial and ethical considerationsx Inquire about the social and ethical considerations that apply to the client's distribution networkx xIdentify, comply with, and exceed social sustainability standards that apply to the system and supply chainx Design to amplify positive social and behavioral impacts and minimize negative impacts of the product's use