Principles of Green Engineering

Prevention instead of treatment It is better to prevent waste than to treat or clean up waste after it is formed. Waste involves a resource that is not used. Any material that is not used, even if it is inherently innocuous, needs to be recovered and recycled. Recovery requires additional processing steps, the use of additional materials, and the consumption of increased energy resources. If the material cannot be recovered, it must be disposed of in some way, and thus it creates a burden on the environment. From a business standpoint, the company pays once for the material it does not need, and then a second time to dispose of the waste. Clearly, reducing the amount of waste enhances the process, both environmentally and economically. 

Output-pulled versus input-pushed Products, processes, and systems should be output-pulled rather than input-pushed through the use of energy and materials. This approach is based on Le Chatelier s principle, which states that when a stress is applied to a system at equilibrium, the system readjusts to relieve or offset the applied stress. Stress is defined as temperature, pressure, or concentration gradient. It is possible to increase the productivity of a process by overwhelming the feed with a specific reactant. That leads to incredible excess of the reactant in the product stream, which requires separation, recovery, and recycle. On the other hand, if you can remove a product from the process stream as it is produced, then the reaction will drive to greater quantities of product, without any need for use of excess reactants. 

Conserve complexity Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition. Highly complex materials can be broken down into simple molecules, which can then be used in the production of different complex materials. However, this is often more energy and material intensive than using the natural complexity of the existing material. In a similar way, complex end products that can be reused are easier to recycle than those that need to be broken down into individual subcomponents. 

Minimize material diversity Material diversity in multicomponent products should be minimized to promote disassembly and value retention. Earlier principles discuss the desire for materials to be recovered and recycled. Minimizing the number of unique substances included within any product simplifies the product and makes recovery easier. A single material such as a polymer with tailoring backbones specifically engineered to accomplish desired properties is easier to recycle and reuse than multicomponent materials. 

Renewable rather than depleting Material and energy inputs should be from renewable resources to the maximum extent possible. Clearly, material and energy resources that are consumed at a rate that exceeds the ability of the natural environment to replenish that resource will eventually be fully depleted and not available for future use. Thus, processes and products should be designed to consume raw materials only at the rate at which they can be replenished. Because materials can be recycled, net consumption is the important parameter to be considered. In other words, aluminum that is obtained from recycled material does not deplete the raw material in the ground and thus may be considered renewable if there is sufficient recycled aluminum to fully meet the process needs. 

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Professional Practice (e.g., ASCE Policy Statement 418 The Role of the Civil Engineer in Sustainable Development The 12 principles of Green Engineering ). 

Anastas, P.T. and Zimmerman, J.B. (2003) Design through the 12 principles of green engineering. Environmental Science and Technology, 37 (5), 94A-101A. 

Anastas, P.Y. and J.B. Zimmerman, Design Through the 12 Principles of Green Engineering,... 

Anastas PT, Zimmerman JB (2003) Through the 12 principles of green engineering. Environ Sci Technol 37 95A-101A... 

P. T. Anastas, J. C. Warner, Green Chemistry Theory and Practice, Oxford University Press, New York, 1998. In 2008 the 24 Principles of Green Engineering and Green Chemistry have been revised see S. Tang, R. Bourne, R. Smith and M. Poliakoff, Green Chem., 2008, 10, 268. 

Tab. 10-3 Draft principles of Green Engineering" (adapted from [10.4])...

Zimmerman JB, Anastas PT. Peer reviewed design through the 12 principles of GREEN engineering. Environ Sci Technol 2003 37(5) 95A—lOlA. 

A reference point for evolving these concepts into practice in the design phase are the Twelve Principles of Green Engineering, developed by Anastas and Zimmerman. The principles encompass ... 

Tang SY, Bourne RA et al (2008) The 24 principles of green engineering and green chemistry improvements productively. Green Chem 10 276-277... 

Green engineering can be defined as a process to develop products, processes, or systems with minimal environmental impacts. The full product life cycle is developed when evaluating the environmental sustainability of the product, process, or system. The 12 principles of green engineering are as follows (McDonough, Braungart, Anastas, and Zimmerman 2003) ... 

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