Green Engineering Principle #1

Inherent Rather Than Circumstantial

Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.

Contributed by Dr. David Constable, Director, ACS Green Chemistry Institute®

All chemicals have properties that help us to characterize and differentiate them from each other. Chemists and chemical engineers are most familiar with properties like boiling point, melting points, freezing points, vapor pressure, water solubility, and so forth. Chemical engineers are also more familiar with properties like flammability, explosivity, compressibility, viscosity, and other properties that affect heat and mass transfer, etc. Most chemists and chemical engineers are less familiar with properties related to toxicity to environmental organisms and humans, and this is one of the things this principle has in view.

The second thing this principle has in view is a systems perspective; i.e., the ability to do mass and energy balances around a unit operation, a chemical process, a facility, or an even larger, more comprehensive and complex system like an industrial park or petrochemical complex. Fundamental to a mass and energy balance is the ability to map inputs and outputs to and from a system or around any boundary you may wish to define.

A third thing this principle assumes is the importance of design and the key role designers. Bill McDonough in his book “Cradle to Cradle” says that design is a signal of intent. I have always felt that this is a great summation of the importance design; it’s absolutely critical to have the best intention. This principle is asking designers of manufacturing processes or products to actively intend that the materials and energy used to make a product have the lowest adverse impact possible.

In the case of materials, designers need to select chemicals or materials made from or with chemicals whose properties will not cause harm to the environment or to people throughout their life cycle. In the case of energy, most designers capitulate to what is readily available – electricity and steam – both of which owe their production primarily to fossil fuels. However, not all energy is created equal in terms of its toxicity profile and its overall efficiency (conversion through transmission through use), even if one is constrained to fossil fuels. Moreover, with the right choice of chemicals and materials, a designer can control how much energy is required and the form of that energy; e.g., heating, cooling, light, microwave, pressure, etc. So please don’t capitulate. Energy matters in terms of putting toxics into the environment as much as, or is some cases, more than the choice of chemicals.

Green engineering demands—even in just this first principle—that you pay attention to a larger set of specifications or design constraints than you otherwise might. If all you intend to do is make something new and bring it to market as quickly as possible, this can at first seem overwhelming. But this is the task at hand if we want to live in sustainable world.

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