Bedoin’s

The quest for impermanence

In the mid-1990s, a certain mail-order computer retailer
announced that it was abandoning Styrofoam (polystyrene) packing
peanuts in its shipments and switching to environmentally friendly
cornstarch peanuts instead. The new filler material, they explained,
was not merely biodegradable, it would dissolve almost instantly in
water. Some of my coworkers and I wondered if that meant you could eat
them too. So, naturally, when our next order arrived from that company,
the first thing we did was to pop the cornstarch peanuts in our mouths.
All right, in retrospect, I suppose that was a bit stupid. It did not
cause any ill effects as far as I can tell, but still…who knows where
that cornstarch has been? So I do not recommend that you try
this yourself. Nevertheless, we’d proven that this new packing material
did, as advertised, dissolve quite readily, and we were all happy that
we’d no longer drown in a sea of Styrofoam.

Remarkably, even though cornstarch packing peanuts are much more
common today, most of the packages I get in the mail are still filled
with Styrofoam. I suppose the charitable view is that I’m watching
recycling in action: no doubt these very pellets have been used
countless times before, and (if I keep with the program) will be used
countless times again. But even if true, that’s somehow unsatisfying. I
really don’t want the burden of storing (or recycling) the filler from
every box I get. I’d like it all to go away—preferably, in some
responsible manner.

Having a Breakdown
Resistance to decomposition is often a virtue; you don’t want, say,
your garbage can to disintegrate in the rain. But for items that are
intended to be used only briefly, this robustness can be a problem.
Hundreds of years from now, empty plastic bottles—not to mention
discarded electronic devices, toys, and everything else—will still be
pretty much intact deep in landfills all over the world. And although
recycling helps considerably, it’s simply not practical or reasonable
to expect that no recyclable goods will ever end up in the trash. So
the next-best thing—and, in many instances, the very best thing—is
plastic that will decompose.

But allow me to digress for a moment. Words like “decompose,”
“disintegrate,” “degrade,” and “biodegrade” do not all mean the same
thing. Suppose you put a piece of plastic in a compost heap and found
no visible trace of it six months later—does that mean it has
biodegraded? And if so, can we safely say we’re talking about an
environmentally safe product? The answer to both questions is “not
necessarily.” Some so-called “biodegradable” plastics, for instance,
are made of a blend of starch derivatives and conventional
petroleum-based polymers. The action of bacteria in warm, moist soil
breaks down the starches in these materials, but leaves countless tiny
particles of plastic that have a mass only slightly less than that of
the original product. And all those parts that don’t break down
continue taking up space without contributing any nutrients to the
soil—in fact, they may actually contribute toxins. So what we’re
looking for in a truly “green” plastic is one that can either decompose
completely via microbial digestion (into such products as water and carbon dioxide), or at the very least, leave only inert substances behind.

Natural Wonders
The thing is, this is generally not in the nature (so to speak) of
synthetic polymers. The interesting solutions, therefore, are largely
to be found in biopolymers,
a class of materials that look, feel, and act like the plastics we all
know and love, but which, owing to their natural sources, can also
serve as food for bacteria. Products made directly from cornstarch,
other starches, or cellulose certainly fit that description. And such
materials, which are used not only for packing peanuts but for things
like fast-food containers, do show a great deal of promise. But if
you’re looking for something bacteria might like to eat, how about the
food they make themselves?

Many different kinds of bacteria (and other organisms, for that
matter) create a substance known as polyhydroxybutyrate, or PHB, that
they store as an energy source in much the same way humans store fat.
PHB, it turns out, is a rather versatile plastic. It can be produced in
quantity quite quickly simply by feeding sugar to the right kinds of
bacteria in what amounts to a fermentation process; it can also be
produced by genetically modified plants (including a type of potato).
Because it is, in fact, a bacterial food product, it’s completely
biodegradable. Another often-mentioned biopolymer is polylactic acid,
or PLA, made from lactic acid—which, in turn, is produced by the
fermentation of cornstarch.

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