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Weighted Sum Assessment Method

The previous methods are basic heuristics to reduce environmental impact. For comparisons between alternatives, however, such an approach may not provide a clear set of changes to investigate. A more quantitative approach of relative importances may thus be desired. A more-advanced approach is to complete a full life cycle assessment-assess the impact of the material usage and waste generation of each stage in the product life cycle.

Rather than a full life cycle assessment, however, one might instead inventory the parts used in a product and weight them by "average" impact weightings. That is, one might break the product down into quantities of materials in the product by weight. Then one might establish environmental impact of different materials by weight and sum this score. This process approximates the life cycle stages of the product as an "average" typical use for each material.

One such approach was developed in Europe on the initiative of the Ministry of Housing, Spatial Planning and the Environment in the Netherlands, called the Eco-indicator 95 (Goedkoop, Demmers, and Collignon). The Eco-indicator system provides weightings by mass for materials, treatment processes, transport processes, energy generation processes, and disposal scenarios. As shown in Appendix D, Figure D.1, and Figure 15.11, the weightings themselves are based on a valuation of damage to public health and to the ecosystem through contribution to several effects, such as ozone layer depletion, smog, and so forth, as discussed in Section 1. The actual effects considered, and from what impact sources, are shown in Appendix D, Table D.1, and

Figure 15.11.

Because the Eco-indicator was developed in Europe, it is based on average European values (shown in Appendix D, Table D.1, and Figure 15.11) for the processes that describe material production, treatments, transportation, and energy generation. Therefore, the application of the Eco-indicator to non-European regions will not be entirely appropriate.

For example, product factors that increase acid rain are over weighted for many regions in the United States. On the other hand, the tool is reasonable and provides indications of relative environmental friendliness of different design scenarios. Software versions are available.

The Eco-indicator system operates by having the analyst first establish the mass of component materials in the product, their means of production, and the means of disposal. A worksheet to evaluate the product is then used, as shown in Appendix D, Table D.2, and Figure 15.12.

For impact weighting values, the tables in Appendix D, Table D.3, Figure 15.13 are used. Other life cycle data must be estimated to complete the numerical analysis. In particular, how long the product is used, how it is delivered to the consumer, and how it is disposed must all be estimated.


Table 15.8 provides a list of typical product life spans that can be used as a first approximation of the actual useful life for different products (Cheney; Chapman). Delivery can be estimated based on the source, domestic or international. Disposal should simply be approximated as landfill, unless either the material is very hazardous and laws apply to its disposal or the material is very valuable.



Example: Coffee Mill



Understanding the environmental impact of a product and intervening as a design team to mitigate effects is a responsibility that must now be adopted. Legislative and consumer demands will only increase in this area. Some key ideas in the design for the environment include:

  • Assessment must be completed considering the entire product life cycle, from the time material is extracted from the earth until it is returned to the earth.
  • Design-for-the-environment techniques and their associated metrics represent one component of a product's systems model.
  • Basic methods include smart material selection, minimizing energy usage, and increasing recycled content. Numerical scoring is possible.
  • Full life cycle assessments provide quantification of environmental impact.

Date: 2016-03-03; view: 3950

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