Good Eco-Intentions Sometimes Bring Bad Results

June 2, 2009
If not used properly, what is intended to be a savings to the environment can end up using more polymers and filling landfills.

No doubt it is possible to conceive and implement technological solutions to ecological problems. But full realization of a technology’s green potential demands that designers also focus on user convenience.

Case in point: Those of us old enough to have populated our offices with paper documents encountered a dilemma regarding means for paper attachment — staples and paper clips. Each staple, weighing about 0.03 grams, was used once. While staples continued to hold papers together while in a file drawer, they were never used again. The typical staple was easy to make from steel strip that was roll-formed into a U-shape and then segmented. Using staples required a dedicated machine — one that employed more than a pound of (mostly) steel and involved some complicated manufacturing operations.

Paper clips, on the other hand, could be reused, did not require a machine to function, and were manufactured from steel wire via a relatively simple wirebending process that used low-cost jigs. Weighing about 0.43 grams, simply on a weight basis, a paper clip is equivalent to about 14 staples, so using a paper clip 14 times gives it an environmental impact equivalent to the use of staples.

But staples are much easier to use. Paper clips are inconvenient because they can be put on in only one orientation and users must get them out of a box. So, many people discard paper clips as a nuisance after one use.

In another example, the widespread use of throwaway plastic shopping bags is a current ecological concern. True, some bags are reused, if for nothing more than returning goods to the stores, where clerks promptly discard them. Putting the bags in the trash is much more convenient, so the majority of them (> 90%) end up in landfills where they simply take up space. Bags are also swept up in breezes and caught in roadside trees and bushes or trapped in waterways, presenting not only an eyesore but a danger to wildlife.

Enter the reusable shopping bag. Some are made of cotton cloth, a renewable natural fiber, but most are made of polymer threads woven and stitched into smart-looking bags that can tote the equivalent volume of, say, four throwaway plastic shopping bags. Large reusable bags provide two flat surfaces where companies can print logos and even short ads. And, given the mass-production capabilities of currently underused manufacturing facilities, large numbers of reusable shopping bags could appear in every shopping arena, becoming as commonplace as the throwaway plastic shopping bags they are intended to replace.

A small but growing percentage of shoppers are toting the reusable bags, but old habits are hard to break. It takes a while for shoppers to get used to taking reusable bags with them into the stores. Various legislative bans on the use of plastic throwaway bags may bring more reusable bags into mainstream use.

If we assume that manufacturing and distribution costs are proportional to material content, we can argue simplistically that the ratio of 80 grams of plastic in a reusable bag to 5 grams of plastic in a throwaway bag suggests that the reusable bags should be used at least 16 times before disposal. During their lifetime, reusable bags are subject to many threats to their structural integrity such as overloading, accidental burns, and broken handles. Therefore, the likelihood of 16 uses before retirement is chancy.

The moral of the story: If not used properly, a product intended to help save the environment can end up using more resources than what it replaces.

— Howard A. Kuhn

Kuhn is R&D Director of The Ex One Co. and is responsible for developing and implementing direct digital-manufacturing and tooling technologies. Kuhn is also an Adjunct Professor at the Univ. of Pittsburgh School of Engineering, where he teaches engineering entrepreneurship and is involved in the digital manufacturing of scaffolds for regenerative medicine.

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