Live Radio Talk on Bioplastics


How sustainable are bioplastics? Can they save the oceans from marine litter? I investigated the issue from the supermarket to the plastic producer, and summed up my research in this live-talk for German radio:

Presenter
Who would not like to contribute to a healthy environment? Wouldn’t it be nice if you left the supermarket feeling you’ve done good by packing your groceries into a plastic bag that says “100 percent compostable”? This is what the [German] supermarkets ALDI and REWE advertise on their plastic bags made from bioplastics. But critics such as the [German environmental NGO] Deutsche Umwelthilfe call it “consumer deception.” The regional court in Cologne has ruled in favor of the manufacturers. Journalist Anja Krieger has looked into the issue. I am now connected to her in the studio in Berlin. Good morning, Anja.

Anja Krieger
Hello Manuel.

Presenter
Do I have to feel guilty now when I grab a compostable plastic bag at the supermarket checkout – or not, because they’re supposed to be biodegradable?

Anja Krieger
Well, whether they are biodegradable or not depends on how you interpret the term “compostable.” Someone who buys a plastic bag like that might think: Great, I can just throw it away, into the environment, and it instantly disintegrates! But it’s not that simple. There is the “seedling” printed on the bag, an eco-label that claims [the product to be] “compostable.” That doesn’t mean it decomposes easily in a natural environment, but only under very special conditions. These conditions can be met in industrial composting facilities, but occur very rarely in nature: namely, a fairly high temperature, a certain humidity, and microbes that can metabolize the plastic. As stated in a European DIN norm, the bioplastics then need to break down within twelve weeks to at least 90 percent water, biomass, and carbon dioxide.

Presenter
I have a compost heap at home. What happens if I throw the bag in there? Or let’s say I’m at sea, and after a little picnic, my plastic bag accidentally is swept into the ocean. Will it be gone after a while?

Anja Krieger
Yes, at some point certainly, but it will degrade much more slowly. If we’re talking about the ocean, which is a relatively cool environment, then it is usually quite difficult for plastic there [to disintegrate]. It doesn’t make a big difference at first whether it’s conventional plastics or bioplastics. The [bioplastic] bag is as much of a threat to marine life as normal plastic: they could eat it, become entangled, choke on it, and so on. The bioplastic bag would probably not survive as long as a conventional bag, but it would survive quite a while. In the long run, the biodegradable bag does have the advantage that it can disintegrate completely without leaving a residue, whereas conventional plastic disintegrates into smaller and smaller pieces down to the size of micro plastic.

Presenter
And this plastic will continue to exist in the environment. Now the critics at the [German NGO] Umwelthilfe are calling into question the producers’ claims that their bioplastic bags can be disposed of in industrial composting plants.

Anja Krieger
Yes, that’s true. The Umwelthilfe carried out a survey among eighty German composting plant companies. It turns out that the bio-bags are seen as an extraneous material there, and need to be sorted out. There are several reasons: on the one hand, the DIN standard is not sufficient for the compost companies. They produce their compost in faster cycles, so the microorganisms are not quick enough and cannot keep up with their workflow. Also, residues that remain in the soil, such as scraps of the bags, can get the producers into trouble when they want to get their seal of approval to sell the compost. The Umwelthilfe also objects that the cornstarch – from which these bags are made – comes from genetically modified plants. But this is more of an ethical issue. The cornstarch is fermented and chemically processed, so the genetically modified DNA is practically nonexistent in the material.

Presenter
Leaving that aside, does this mean I can throw the bags into the compostable bin, theoretically, but in practice they are fished out and then, I suppose, burned in the incinerator?

Anja Krieger
Exactly. If the Umwelthilfe survey is empirically accurate, then that’s the case.

Presenter
Doesn’t it make more sense then to throw the bags directly into the yellow bin [the German recycling bin for the “dual system” for particular packaging materials], along with the packaging with the green dot label? Then they could at least be recycled together with the other plastic.

Anja Krieger
No, that wouldn’t make sense at the moment. The biodegradable materials are not yet part of the dual system in Germany. And this happens to be a financial advantage for the manufacturer: they don’t need to pay the fees. Of the many types of plastic we throw in the yellow bin, only four are sorted out and recycled. The rest is burned. The bioplastic material, for example the PLA from the bags, would not be recycled. One thing would make recycling even more difficult: the bags are not only made from PLA, cornstarch, but also from a fossil-based plastic …

Presenter
… which obviously is not biodegradable?

Anja Krieger
No, this is the fallacy: that these two properties, biodegradable and bio-based, are connected. In fact they are independent. There are bio-based plastics that degrade just as poorly as conventional plastics. Some are even chemically identical. And the reverse is also true: there are fossil-based plastics that are biodegradable according to the DIN standard. This is exactly the kind that is in the bags, mixed with PLA. The problem with recycling is that if the plant-based and fossil-based bioplastics are mixed, you don’t have a homogeneous substance anymore, and then recycling becomes quite difficult.

Presenter
We have a group of visitors in front of the [studio] glass panel. Could you all please nod if you understood all of this, or shake your head if you haven’t. [laughing] So most are shaking their head.

Anja Krieger
[laughs] Yes, it’s complicated.

Presenter
Well, then let’s try a preliminary conclusion: Theoretically, I could throw the bag in the compost bin; in practice, it is burned. In the yellow bin it’s of no use either. So in the end, all that’s left is the residual waste bin. But when I think of bioplastic, I would like to see a plastic that naturally decomposes everywhere. Because the real problem is that a lot of bags don’t end up in any of the recycling bins, but in the countryside, the rivers, and the sea. You can see that abroad especially, in places where the waste system does not work quite like ours.

Anja Krieger
Yes, that was exactly my question to my interviewees: Are you developing something like that, and would that make sense? And surprisingly, all pretty much agreed, whether they came from industry, environmental NGOs, or research and development, that bioplastics cannot solve the problem of [marine] litter. The biodegradable plastics currently available take quite a long time to degrade in natural environments. Another argument is that if we put a lot of energy into a material that dissolves immediately, then we are wasting valuable resources. Littering is only one of the many environmental aspects. If you look at the entire life cycle, it is also about things like, how was the field fertilized that grew the corn for the plastic? What kind of power was used to make the bags, nuclear or wind power? And of course, what happens at the end with the plastic, how can it be disposed of? Composting then oftentimes turns out to be worse than recycling or incineration, where you may at least harness energy.

Presenter
So here we are again in the classic Life Cycle Analysis. Could you perhaps summarize – what is the life cycle of the bioplastic bag?

Anja Krieger
It’s very hard to say. It depends on the details of how it was made, where the bag comes from, what material and mixture were used, how it can be disposed of. There are many different manufacturers, and each bioplastic bag has its own life cycle. For me, the interesting thing that emerged during my research was that the trend in bioplastics research has actually moved away from compostability; it’s now more about longevity. [Researchers] are trying to develop bio-based plastics that last as long and are as recyclable as conventional plastics. [Producing bioplastics] is not about the littering problem anymore, but an attempt to move away from oil – to spare the risks of oil drilling and also to reduce CO2 emissions. And of course there are also financial reasons to move away from oil, which will become more expensive in the long term.

Presenter
So I would say, to reduce waste, I should take a backpack, my cloth bag, or a foldable box when I go shopping – and use it for ten years. How do you do it? Are you going shopping with bioplastic bags or not?

Anja Krieger
I took them with me for quite a while, but now I [have stopped and] bring my cloth bag again.

Presenter
Thank you very much. That was Anja Krieger. More about the topic tonight at 19:30 in [German national public radio] Deutschlandradio Kultur during the broadcast of the radio feature “The promise of bioplastic.” And we have just heard that this promise isn’t quite fulfilled.

Credits + Links
Live Radio Talk on Bioplastics
Broadcast April 4, 2012, live talk on DRadio Wissen, Nature Section
Length: 9:31 minutes
Report: Anja Krieger
MP3 (German)
Blogpost with link to the half-hour feature on the topic on my website (German)

Schreibe einen Kommentar

Deine E-Mail-Adresse wird nicht veröffentlicht. Erforderliche Felder sind markiert *