Tag Archives: ecology

Plastics that bend the category of plastics

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It sounds about as likely as a “healthy cigarette.”  I’m talking about “compostable plastic.”  I mean, the one thing we’ve all known for sure about plastics is, they’re bad for the environment, because they don’t bio-degrade.  Right?

Now comes this new generation of plastics that does biodegrade, and some of them even can go into a compost pile.

I’ve seen the product labels for a couple years, but I didn’t really take it seriously.  Someone told me, they’re made out of corn.  Yeah, corn and what else?

Compostable cups, fork, and other containers with the Cedar Grove seal.

It turns out, those corn-based plastics do in fact degrade into compost, according to the local experts at Cedar Grove Composting.  That’s the company that takes the yard waste from a million or so customers in King and Snohomish counties.  In the Seattle area, Cedar Grove has defined the category of composting, taking our leaves, branches, and clippings and selling it all back to us as bags of compost.  They also take all of our table scraps, from residences and many businesses.

Cedar Grove runs its own tests — by simply putting a so-called degradable plastic item into the compost pile, and checking to see if it turns into dirt.  “If it degrades and disappears then we approve it,” says vice president Jerry Bartlett.  Companies pay hundreds of dollars to get their products tested.

More than 400 plastic cups, forks, plates, and other items passed the test and do in fact turn to dirt.  Bartlett tells me they leave no visible residue, although no chemical testing is done at the end of the cycle.  On the other hand, 75% of the so-called “biodegradable” plastics submitted for testing do NOT turn into dirt. These are banned from the compost pile.

How does it work?  Through heat, mostly.  These industrial-scale compost piles get up to 170F degrees.  (If you put one of those compostable spoons in a bowl of hot chowder by the way, don’t leave it sitting in too long — the heat will start melting it.)

Apparently, many other new plastics are still made of traditional petro-chemical plastic, with additives that speed up the decomposition.  What might normally take 1,000 years, now takes 20 years.  But, Treehugger reports there are concerns that these actually may do more harm than good, by leaving tiny residual particles of plastic that then can enter the ecosystem.

So, if it says “compostable,” it’s probably made from corn or another plant-starch.

My story on KPLU has a few more details and links.

Microbes on the beach

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More on microbes. This time, it’s the effort to understand the vast number of species that live all over our environment. Most of these (like 95%) can’t be grown in the laboratory, so they haven’t been studied much. For the past decade there’s been a rush to use new DNA sequencing technologies to identify and learn about these bacteria. That’s how we became aware of how little we know.

One effort along these lines is happening in my backyard, or not far from it. A group at the University of Washington is sampling mud from Lake Washington. They’re developing ways to pinpoint species that live there, focusing on bacteria that subsist on methane and related compounds. If you’re interested, you can read a summary from the press release, or visit the lab’s website.

Spicy microbes

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Ecology is full of surprises. And often those surprises have to do with microbes. I’ll write more about microbes in the coming months. I was lucky this week to be able to write about chili peppers and the strange ecology that allowed them to evolve spiciness.

Short version: Josh Tewksbury at the University of Washington, and a team of researchers, found that the spicy substance inside peppers acts as a defense against a fungus. That fungus destroys the seeds inside the peppers. (It turns them black and generally very gross looking.) In climate zones where the fungus grows more readily, the peppers evolved to be spicier. Specifically, they produce more capsaicin. The same chili species in drier zones is not spicy at all.

But what makes it not just interesting, but fascinating, is the three-way relationship between the chili plant, the fungus and a tiny insect. Without all three, the world would be full of bland food.

The insects, as Tewksbury describes them, have mouths shaped like drill bits. They drill into the chili fruit and into the seeds, and eat the nutritious inside of the seeds. They can do a lot of damage, but they don’t destroy all the seeds. However, the holes they drill allow the fungus to get inside the waxy fruit surface and seed surface. By secreting a spicy substance around the seeds, the plant keeps the fungus at bay, just enough to keep the fruit and seeds looking healthy.

As long as the chili peppers look tasty, birds will eat them, as birds are not sensitive to spiciness. And birds are the main distributors of chili pepper seeds.

If you take any of the creatures out of the system, you don’t get spicy habaneros or jalapenos or any of the other peppers we know and love. In fact, all spicy peppers, along with sweet peppers, evolved in the dry forests of Bolivia, Argentina and Paraguay. People bred many varieties from just a few core species. They spread around the world, including to India and Thailand, only post-Columbus.

Wow.