Chapter 15 Materials and the Environment Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Design for the Environment Design for Sustainability Environmental Design Design for the Environment Effort to adjust our present design methods to correct known, measurable, environmental degradation; time scale of this thinking is 10 years or so Design for Sustainability Adaptation to a lifestyle that meets present needs without compromising the needs of future generations; time scale is measured in decades or centuries Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

The Material Life-Cycle Figure 15.1 Ore and feedstock are mined and processed to yield a material. These are manufactured into a product that is used and, at the end of its life, discarded and recycled. Energy and materials are consumed in each phase, generating waste heat and solid, liquid, and gaseous emissions. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Figure 15.2 The influences on consumption of materials and energy. It is essential to see eco-design as a systems problem, not solved by simply choosing “good” and avoiding “bad” materials but rather by matching the material to the system requirements. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Table 15. 1 suggests a matrix of product use patterns Table 15.1 suggests a matrix of product use patterns. The load factor is an approximate indicator of the intensity of use. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Figure 15.3 Approximate values for the energy consumed at different life-cycle phases: material production, manufacture, transportation, and use. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Material Production: Energy and Emissions Most of the energy consumed over the life-cycle of a product is derived from fossil fuels. Material production is generally associated with undesirable outputs such as toxic wastes and particulates. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

End of life options: landfill, combustion, recycling, refurbishment, upgrading, and reuse. Figure 15.4 Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Eco-Design Figure 15.5 Rational design for the environment starts with an analysis of the phase of life to be targeted. This decision then guides the method of selection to minimize the impact of the phase on the environment. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Material Charts for Eco-Design Figure 15.7 Embodied energy per unit mass of materials Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Embodied energy per unit volume of material Figure 15.8 Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

The best materials to minimize embodied energy of a beam of specified stiffness and length have the following material index: Figure 15.9 Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Similarly, strength-limited designs aimed toward minimizing embodied energy should use: Figure 15.10 Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Eco-Selection of Material for Drink Container Figure 15.6 Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

From the data in Table 15.5, the dominant phase is material production. Summing the two energies for each material and multiplying by the container mass per liter of capacity indicates that steel carries the lowest energy penalty. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Crash Barriers For static barrier, the objective Figure 15.11 For static barrier, the objective is to minimize embodied energy For a car bumper, the objective Is to minimize mass Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Figure 15.12 Material choice for the static barrier. Cast irons, carbon steels, low steel alloys, and wood are the best choices. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby

Figure 15.13 For the mobile barrier, CFRP and light alloys offer the best performance. Materials Selection in Mechanical Design, 4th Edition, © 2010 Michael Ashby