The tetrahedron of sustainability design - a 3D framework for the integral and interdisciplinary development of circular economy oriented products

Traditional product design follows three main directions that had to be thought and planned in an integrated way: Desirability, feasibility, and viability. Aspects from user research, technology development and business models must be weighed against each other and to be optimized as holistic concept. For future product design those three dimensions seems to be not sufficient any more as the sustainable impact from products regarding their production, usage and end of life, becomes an important factor in development processes. The so-called circular economy, that describes the goal of a most efficient use of resources and products in closed loops, brings with it totally new requirements for products and their development. Already the traditional innovation design should have been understood as a joint task of market researchers, engineers, business planers and designers, but the arising challenge of the development objectively sustainable products needs that interdisciplinary thinking even more. New frameworks, tools and method that allow the interdisciplinary exchange in an effective way to enable the creation of joint visions and concepts are needed. While the traditional three fields of product design as described by Tim Brown can be showed in two-dimensional frameworks as three overlapping circles, the addition of sustainability as fourth design field needs more complex visualization that brings the different aspects in relation to each other. For solving that task and for creating a new tool as core for interdisciplinary, circular economy oriented design projects, we developed and evaluated a three-dimensional framework – the tetrahedron of sustainability design. The critical aspect of integrating the circular economy as a decision parameter into innovation processes arises through the facts that target conflicts will come up that can not be solved in an easy way as product individual lifetimes must be taken into consideration. Therefore, the main goal of the framework is to motivate discussions of different disciplines and their decisions regarding to the effecting influence on other design fields. It is created as tangible three-dimensional object as anchor point for workshops and individual considerations. The tetrahedron of sustainability designs shows the four fields of future product design as equilateral pyramid with triangular bases, with each design field representing one of the bases. The corners of the pyramid, each closed by three of the design fields, are defined as four main levers of sustainable product concepts. At the top of the pyramid, the central value proposition that can be described as a set of abstract value elements that should be fulfilled by the product, must be thought by reflecting the customers (desirability), the business model (viability) as well as the sustainability effects (integrity). While those first three design fields open up the space of conceptualization, the field at the basement of the pyramid represents the technological realization (feasibility) of the products. It is enclosed by the following corners: The R-Strategies define how circular economy effect should be created, e.g. by recycling, reusing of parts or rethinking of the product functions. Beneath the technical realization. This corner is additionally affected by the understanding of the customer and the sustainability effects. The next corner, the life cycle consideration, describes how a product is produced, used, maintained and how its end of life can be shaped. As well as the technical realization, the design fields of the business model and the sustainability effects are relevant to that corner. The last corner is defined as the degree of servitization what is based on the understanding of innovations as solution-oriented product-service-systems. While the physical parts are described by the technical realization, the business model and the customer wishes affect what product aspects can be realized as additional value-added service or by innovative ownership-models. As last part of the framework six edges have been defined, each located between two design fields and two corners. Those six edges are formulated as concrete decision points and hints for the design process. Starting from the value proposition corner, every three edges of the space of conceptualization lead to one of the tree corners that surround the basement of realization and are influencing the determination of the abstract product concept. Against that, the three edges of the base of realization are formulated as guiding principles for the physical product design. The whole framework, its elements and the way of usage will be explained an defined more in detail in the paper. Furthermore, the framework will be shown and evaluated on an exemplary design project. As example the concrete design project of an electric scooter for young urban generations will be introduced and reflected regarding of the aspects of the framework.