Chapter 8. Whole Product Assessment and Optimisation

After looking at every phase of the life cycle separately, designers and engineers need to combine the considerations from every phase. When doing so, trade-offs emerge between the life cycle phases.

The material selection can be optimised for the sustainable design goals. The design team should look for dominance in options (i.e., win-win situations). This chapter identifies the resulting trade-offs and illustrates how to deal with them.

The decisions or constraints in one phase of the life cycle influence the possibilities in the other phases. Table 8.1 indicates how constraints set in the top row of the table influence the phases in the column on the left. The list is non-exhaustive and should be complemented by the design team.

Note that data gaps are encountered at every phase of the life cycle. One of these data gaps is the lack of (comparable) emissions data throughout the supply chain. Design teams should not neglect data gaps and should not assume there are no sustainability implications. They should strive to fill these in wherever possible, especially for life cycle phases where damage to human health and ecosystems is to be expected based on available benchmarks. The teams should explicitly keep track of unknowns along the way. When an appropriate disclosure is missing, a sensitivity analysis (to see how important an environmental release might be), exposure testing or substitution for safer chemicals is advised.

There can also be significant variation in emissions between manufacturing facilities for the same base polymer material. The theoretical embodiment of the product concept should be put to the test with practical knowledge from specific suppliers who will provide the material and relevant circular processors who will most likely treat the products at their end-of-use. The sustainable design goals, life cycle considerations and trade-offs help guide the discussions with these stakeholders.

In the case of trade-offs, designers and engineers will have to carefully evaluate considerations to favour one over the other. This process is guided by the ranking of the sustainable design goals and the non-negotiable conditions defined in Chapter 3. Transparency throughout this process is important to support credibility and ensure that decisions are traceable.

To illustrate how to deal with trade-offs, the example in Chapter 3, where closing resource loops is prioritised over slowing and narrowing resource loops for prioritising design goals (see Figure 3.1), is used to examine three trade-offs in the case of detergent bottles (Figure 8.1). The ranking example was as follows: 1. Select materials with inherently low risk/hazard; 2a. Use secondary feedstock or biobased feedstock, 2b. Have a commercial ‘afterlife’ (recycling); 3. Generate no waste; 4. Have a commercial ‘afterlife’ (other aspects).

The underlined terms in Figure 8.1 are decisive in the reasoning. The circled trade-offs are the ones that have been prioritised based on the reasoning in the right column. This approach can also be adopted to deal with the trade-offs emerging within the life cycle phases.

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