Integrating sustainability into design of alternatives for CFCs

Current engineering design methods do not take the concept of 'sustainability' into consideration. In light of increasingly clear signs of unsustainability on a world scale, such as global warming, it is, however, necessary that process and product development include the concept of sustainability. This paper describes a new general method that operationalises the concept of sustainability into engineering design methods for selecting a sustainable process or product. The method modifies and extends principles of Life Cycle Assessment (LCA) to evaluate the long-term effects of the production, use, and disposal of possible alternatives. In addition to global warming, the comparison of the different alternatives is based on themes including ozone depletion, nutrification, acidification, and photo-chemical smog formation. New themes developed include safety and household toxicity. The method also explicitly considers the important social concept of 'equity', the 'ultimate environmental fate' of substances, and the precautionary principle as criteria to assess sustainability. The developed method is applied to six possible alternatives to CFC-refrigerants for household refrigerators: iso-butane, formaldehyde, dimethylether, HFC, chloromethane, and ammonia. The new method shows that iso-butane is the best refrigerant, but only sustainable if the electricity production itself is sustainable.