What Am I Measuring? The Three Choices of Environmental Assessment

Product sustainability is not only relative, it’s multidimensional. There is no single, universal indicator of sustainability (no, not even carbon). The appropriate impact metrics and dimensions on which products are compared can differ significantly, depending on the purpose of the evaluation. Impact measurement creates the key dashboard for sustainable design, so it’s important to choose an assessment approach that will generate information consistent with its intended use.

 

The appropriate technique for evaluating the environmental impact of a design depends on the answers to the following three questions:

1.      What impacts do you care about? Does toxicity matter? Water use? Only CO2 equivalents?

2.      What is the scope of the assessment? How far up and down the supply chain does it go? How much of the product’s lifecycle should it reflect? What is the unit of analysis for the assessment? Is it for a component, an assembly, a product, a system?

3.     What types of metrics are appropriate for your purposes? What will the assessment information be used for, and by whom? Is rigorous detail necessary, or is a “rough idea” good enough?

 

The following figure lays out these choices graphically, using examples of some of the impacts, scope elements, and metrics that might be used. The sections that follow will explore each of these elements in more depth and give examples of the kinds of assessment techniques appropriate at each level.

 

“This is pretty intense,” thought Priscilla. “I’m going to call up my friend Tom and talk to him about sustainable engineering and my little cup. Maybe Tom has been through this process before.”

 

As luck would have it, Tom was going through an identical exercise with a product of his own. Tom is a tinkerer of tiny toys for tots and toddlers, and now he was toying with the idea of making a greener holiday gift for his wee customers.

 

Here’s the toy that Tom showed Priscilla:

 

Download the model to play along with this example.

 

“It’s a pretty simple toy,” Tom told Priscilla. “The child pushes it around, and at the push of the button, the lights flash and the siren sounds. They can also pull the fireman out of the truck.”

 

“I had to think for a while about the functional unit that I was using for environmental comparisons,” continued Tom. “After all, this toy is clearly more impactful than other toys—say, some simple plastic blocks of similar size. After all, my toy uses a battery. But I’ve noticed that my own kids will play with a toy a lot longer if it does something—like having flashing lights. So I decided that my functional unit was a children’s toy with interactive components, which can be played with on the floor. So my question is:

 

“How can I make a greener children’s toy?

 

“I’m at the stage now where I’m making my three measurement choices,” Tom finished. Perfect, thought Priscilla.

 

 

 

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