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5 Five Steps to Eco Design // STEP 2: IMPRECISE DATA CAN GUIDE GOOD DECISIONS Engineers and designers who are used to the precision with which physical properties are measured can be disconcerted by the imprecision of eco data where values are, at best, known to within 10%. However, it is important to realize that this does not prevent good decision making, especially when the environmental impact of a particular life phase dominates. For example, when selecting materials, the difference in values of embodied energy or CO 2 footprint can often be a factor of 1,000 or more, so the imprecision still allows firm distinctions to be drawn (Figure 3). When the material phase differences are small, other factors such as the recycled content of the material, its durability (and thus lifetime), and the ability to recover and recycle scrap at end of life are more significant in making the selection. STEP 3: CONSIDER THE ENTIRE PRODUCT SYSTEM Environmental performance is often significantly affected by how the user interacts with a product, how it is maintained, the operating environment, and whether it is the correct product for the user's needs. A useful tool for this is the Environmental Impact Assessment, which helps engineers consider the environmental impact of all phases of a product's life during design: material, manufacture, transport, use, and disposal (Figure 4). This encourages designers to invest the greatest effort in improving the environmental sustainability of the phases that carry the highest demand for energy or generate the most CO 2 . Doing this in the early stages of design will yield the maximum return on investment. A good example is the impact on these five variables (material, manufacture, transport, in use, and disposal) in the shift towards electrification. CO 2 impact over the lifetime for a typical internal combustion engine (ICE) vehicle is heavily skewed to the in-use phase, whereas for an electric vehicle, this impact has shifted to the materials being used, thus becoming a key element for designers. STEP 4: MATERIALS & PROCESS DECISIONS ARE CRITICAL Material and process decisions play a very important role in determining the environmental impacts of a product across the life cycle: • Extraction and processing of raw materials carries significant environmental impact. • Materials choice determines feasible manufacturing processes and associated energy and material efficiency. • Material mass can greatly influence energy consumption and CO 2 emissions in transport and use phases. • The substances used in materials and their recyclability/reusability characteristics determine toxicity, restricted substance impacts, and the impact of a product at the end of its life. Some key strategies for minimizing environmental impact of each life stage are shown in Figure 4. Many relate directly to materials characteristics. One critical point is that you cannot base "eco materials selection" simply on the "eco properties" of the constituent materials, such as embodied CO 2 , recycled content, or toxicity. You must assess these properties in combination with mechanical, physical, thermal, and electrical properties. For example, when reducing CO 2 emissions, it may be better to make a vehicle body out of a lightweight material such as a carbon fiber composite, even if this raises the CO 2 emissions associated with the material production and manufacturing phases. The lower mass is likely to lead to a large reduction of in-use phase CO 2 emissions, which yields overall improvement. Figure 3: Firm conclusions can be drawn about the environmental impact of a material, even with imprecise data. Figure 4: Environmental impact can be assessed for each life stage of a product. Materials and process selection play an important role in determining environmental impacts and can be used in many eco design strategies (Step 4).

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