Discussion of the Principles

5.3.2.1 Systems Thinking. The optimal design of a product or process will be one in which the design considers the unit as a system, which in turn is part of a larger system. What is a system? A system is a collection of objects that receive inputs from the external environment and/or from other objects of the system, and transforms the inputs to outputs (Olson, 2005). The system consists of the object being analyzed, plus any inputs and outputs; thus, it is imperative to identify system boundaries in order to define the system. A system can be large or small, and it can be part of a larger system. Systems analysis describes the potential interactions that an engineer can evaluate in designing a process or product to minimize its impact on the environment. In addition, a systems analysis allows the engineer to gain a complete understanding of the interactions of the process or product with the environment. The first step in a systems analysis is to define the goals and objectives (Olson, 2005), always keeping in mind that the product must perform the function for which it is designed. The systems engineer completes an iterative process, beginning with what is already known, creating a diagram for study, communicating and verifying the information, expanding the information based on targeted objectives, solving the problem, and then determining if the solution is adequate. Systems analysis is the only method that allows the engineer to holistically design a product to meet a set of design criteria that can include both function and sustainability.

5.3.2.2 Systems and Ecosystems. Regardless of the process or product that is being designed, it is important to consider that the unit will be part of the larger ecosystem. Thus, sustainable engineering challenges the designer to include the interactions of the unit with the ecosystem as a key design parameter. What is an ecosystem? The Natural Resources Board of Canada defines an ecosystem as "a dynamic set of living organisms (plants, animals and microorganisms) all interacting among themselves and with the environment in which they live (soil, climate, water and light)" (http://www.cfl.scf.rncan.gc.ca/ecosys/def_eco_e.htm). Thus we see that all living creatures are part of the ecosystem, as are all parts of the Earth. The ecosystem includes elements of the carbon cycle, the water cycle, the natural progression of plant and animal life in a region, and numerous other activities that can be defined through the science of ecology. Humans, and human activity, are also part of the ecosystem. What distinguishes an ecosystem from a natural ecosystem? The European Environment Agency defines a natural ecosystem as "an ecosystem where human impact has been of no greater influence than that of any other native species, and has not affected the ecosystem's structure since the industrial revolution" (http://glossary.eea.eu.int/EEAGlossary/N/natural_ecosystem). Thus, the goal of the engineer who designs for sustainability should be to maintain the influence of the system being designed to that which is no greater than any other component of the ecosystem. This challenge requires that we define an engineered system within the ecosystem, and design our engineered system to have minimal flows of energy and materials across its boundaries.

5.3.2.3 Life Cycle Thinking. The impacts that a product or process might have on the surrounding ecosystem vary throughout the life of that particular product. Life-cycle analysis requires an evaluation of the interactions during the manufacture of the material, the use of the unit, and eventually the disposal of that object. It includes all of the energy and material interactions between the engineered system and the ecosystem. As a natural consequence, it is essential to define the boundaries of the engineered system. Although it is often possible to identify the interactions between the engineered system and the ecosystem, aggregation of the impacts throughout the lifecycle are often difficult, and require complex analysis tools. One approach is the concept of the ecological footprint (Wackernagel and Rees, 1993), which attempts to describe the ecological impacts of a community based on the land area that would be required to maintain the current lifestyle within that community. This type of metric provides an overall measure of the consumption of a particular community, and presents it in a fashion that is easily translated by the general public. Another technique, based on exergy analysis, uses a thermodynamic measure to analyze and improve the efficiency of chemical and thermal processes, and aims to couple interactions between the system and ecosystem through rigorous calculations (Hau and Bakshi, 2004). The U.S. EPA, through its Waste Reduction Algorithm (WAR), evaluates chemical interactions and defines a term known as potential environmental impact to evaluate the interactions between the system and the ecosystem (Young et al., 2000) and including the impacts of energy utilization by the system. Regardless of the method used by the designing engineer, the goal of reducing the impact of the engineered system throughout its entire lifecycle, not just during the manufacture of the product, is an important component of sustainable engineering.

5.3.2.4 Use Safe and Benign Materials. Since the 1970s, the U.S. government has developed regulations and guidelines to limit the use of specific materials that have been demonstrated to be harmful to the public, or to society at large. The Montreal Protocol, which curtailed the use of fluorocarbons for refrigeration, is an example wherein groups of governments have identified a hazardous material and restricted its use. While restricting the use of known hazardous materials helps to avoid ecological damage, a proactive approach that seeks to use inherently benign materials ensures long-term environmental propriety. The design of chemicals that are inherently benign is a central concept of green chemistry (Anastas and Warner, 1998), which proposes that chemicals should be designed using the principles of health and environmental sciences so that they contain minimal toxicity for both humans and the ecosystem. Green chemistry seeks to minimize the risk associated with the use of chemicals by eliminating the hazard, reducing the need for extensive risk management or health and safety precautions. The sustainable engineer should seek to utilize chemicals that are as harmless as possible, and consider the potential impact of every material used throughout the lifecycle of the product or process. A chemical that may not be hazardous during the manufacturing stage but is hazardous to the environment during the disposal stage should clearly be avoided.

5.3.2.5 Minimize Depletion of Natural Resources. Although there may be disagreement on the quantity of fossil reserves, there is general agreement that the reserves are limited. Thus, in order to promote sustainable designs, one must focus on the use of nonfossil reserves. Renewable resources should be promoted and used wherever technically and economically possible to replace products and processes that are derived from fossil resources. The use of renewable resources, however, should not occur without a concern for the level of reserves of these materials. In order to be truly sustainable, energy and material inputs must be derived from renewable resources at a rate that does not exceed the regenerative capacity of the ecosystem (Heusseman, 2004). If one consumes renewable resources at a rate that exceeds the regeneration rate, then renewable reserves will decline, and society will once again be faced with the need to identify new stocks of raw materials. For electricity generation, renewable sources can take the form of solar energy production in photovoltaic systems, wind energy, or the conversion of biomass. If one requires liquid fuels, then biomass is the most viable renewable resource, although improvements in crop and conversion technology are required in order for the production of fuels from biomass to become economically viable (Towler et al., 2004). Likewise, biomass is the most viable renewable material for the production of chemicals and plastics. However, manufactured goods that are based on metal components cannot be derived from biomass-derived resources without substantial reengineering, and thus must derive from increased recycling and reuse of already consumed materials. Design techniques that promote materials reuse and recycle, such as design for remanufacturing, in which the form of the product is retained and the product is reused for the same purpose or for a secondary purpose (Bras and McIntosh, 1999), seek to minimize the consumption of new natural resources and maximize the utilization of previously mined materials.

5.3.2.6 Strive to Prevent Waste. A waste is an unusable or unwanted substance or material, or something, such as steam, that escapes without being used. Regardless of the definition, waste is something that is lost without recovering an appropriate value. Whether from an economic or an environmental perspective, waste is a lost opportunity to convert a raw material into a profitable product. Waste prevention returns to one of the original environmental paradigms known as the three Rs: reduce, reuse, recycle (see http://www.epa.gov/epaoswer/osw/index.htm for more information). It is codified in the Pollution Prevention Act of 1990, which states that source reduction is the ultimate goal of environmental protection. Waste reduction in consumer goods can be achieved by decreasing the amount of material that is consumed in packaging; in manufactured goods we can redesign the manufacturing process to use fewer raw materials. Reuse involves using a product many times; for example, use ceramic coffee mugs instead of Styrofoam cups, or converting an abandoned office building into apartments or new retail space. Recycling turns materials that would otherwise be waste into valuable resources, such as the conversion of waste cooking oil into fresh biodiesel fuel. Although waste cannot be completely eliminated, it can be substantially reduced through the development of new technologies that minimize the consumption of unnecessary inputs (either material or energy) and maximize utilization of all raw materials to achieve a desired function (Zimmerman and Anastas, 2005).

5.3.2.7 Employ Good Engineering in the Context of Societal Desires. Sustainable development requires the assimilation of sound scientific knowledge applied with the acceptance and support of the Earth's population. The technical community serves as a catalyst to build the social capital needed to change the social environment from one of waste production and disposal, to that of recognizing the need to reuse and recycle products (Neace, 2003). As individuals, we support regulations and manufacturing techniques that lead to improved environmental performance; however, as a society there is a tendency to adopt the attitude that resolution to a problem will be achieved through the actions of other people. For example, decreasing supplies of fossil energy and increasing evidence of the impact of energy consumption on global climate change has raised public awareness of the need for increased energy conservation. However, individuals still seek to drive large vehicles with poor fuel economy, arguing that their individual choice will have no substantial impact on these global challenges, but failing to recognize that societal behavior is the aggregation of individual choices. On the other hand, social capital is high in formalized groups in which people have the confidence to invest in collective activities, knowing that others will do so too (Pretty, 2003). In the context of sustainable engineering, social capital is needed to induce societal changes. Social capital can be developed when the engineer can pose technically feasible alternatives in the context of community goals, thereby inducing societal change with minimal political and social upheaval. Engagement with the local community is a central element of sustainable engineering. As stated by Engineers without Borders, "We also believe that the non-engineering components of local needs are almost always more complicated than the engineering aspects, and we seek to instill this reality within the engineering students that are an integral part of the entire process" (for more about Engineers without Borders, see http://www.ewb-usa.org/index.htm).

5.3.2.8 Look for New and Innovative Alternatives. Sustainable development will require the reform of existing institutions and policies, combined with the introduction of new, clean technologies. However, new technologies are often complex and require long lead times for commercialization. As a result, successful implementation will depend on the creativity and ingenuity of the scientific and engineering community (Coles and Peters, 2003). Opportunities for the development of sustainable technologies are only limited by the imagination of the designers. New developments in biotechnology are providing opportunities to grow crops in marginal regions, and to convert ever larger portions of these crops into useful materials. Nanotechnology is creating new electronic devices that are smaller and more energy efficient. History provides excellent examples of how new engineered products have created completely new paradigms that can enhance sustainability. For example, twenty years ago the cellular telephone was first being developed; today, this technology can provide digital communications from anywhere on the globe using commercial satellite systems. From the standpoint of sustainable technologies, the application of photovoltaic systems in remote regions is bringing electricity to remote communities that are far removed from grid access. The Coalition to Access Technology and Networking (CATNet) recycles older computer technologies to bring Internet access to urban and disadvantaged communities at public access points, making connectivity possible to all individuals, regardless of economic and regional conditions (see http://uac.utoledo.edu/metronet/catnet/ Default.htm). Several of these examples illustrate that we can deliver services without the need to consume new products. This concept is embedded as a central element in the design of product service systems, in which a company works with a client to identify the service that is required, as opposed to the product that will perform the service. Thus, instead of purchasing carpeting from a vendor for an equipment show, it is now possible to rent carpet tiles that can be returned to the vendor at the conclusion of the show (Manzini and Vezzoli, 2003).

5.3.2.9 Engage Communities and Stakeholders. In order to design a product for use in a community, it is critical to understand the needs of the community. Engaging stakeholders is an effective way to clarify and prioritize a community's needs, which promotes sustainability by explicitly including the goal of human welfare in design (Heine and Willard, 2005). The community stakeholders help to identify their acceptance of a particular technology and their willingness to operate within a constrained ecosystem. Stakeholders will identify concerns and issues in a project that can be clarified before planning decisions are made. In this way, proponents can address stakeholder concerns and goals, minimizing costs and maximizing social benefits, and producing a better overall proposal (Bender and Simonovic, 1995). Stakeholder involvement is an important management tool in developing an engineered product that can find a market niche with the public at large, but is also an essential business component during interactions with supply chain partners. Consider, for example, the product service systems concept, described above. In a product-based market, each stakeholder optimizes the manufacture of their own product. Unfortunately, this scenario often fails to optimize the delivery of the service, resulting in waste and excess costs. However, by engaging all of the stakeholders throughout the lifecycle of the delivered service, the entire process can become optimized, creating the most efficient mechanism for delivering the desired outcome. Thus, we see that stakeholder involvement in the design stage can create a more sustainable engineering solution.

5.3.3 Concluding Comments

According to the Engineering Council of South Africa, engineering design is the creative, iterative, and often open-ended process of conceiving and developing components, systems, and processes. A designer works under constraints, taking into account economic, health and safety, social and environmental factors, codes of practice, and applicable laws (http://www.ee.wits.ac.za/^ecsa/gen/g-04.htm# Engineering_Design). The Principles of Sustainable Engineering provide a paradigm in which engineers can design products and services to meet societal needs with minimal impact on the global ecosystem. The principles cannot be taken as independent elements, but rather should be considered as a philosophy for the development of a sustainable society. The principles are not prescriptive. They do not provide engineers with a definitive methodology for deriving a sustainable design. Rather, they provide engineers with overarching concepts that can be used along with traditional design principles to develop new products and services to be applied for the growth and development of human society, while simultaneously minimizing the impact of these designs on the global ecosystem.

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