In the latest episode of Standards Impact, we break down the difference between biobased plastic, biodegradable plastic, and compostable plastic.

By JP Ervin

Jan 10, 2024

Plastic has become a hot-button issue in recent years. There is growing awareness of the risk of microplastics, as well as a great deal of excitement about biodegradable, compostable, and biobased plastics. What is the future of plastic – and what is being done to bring these materials into a new era?

For episode six of ASTM International’s podcast Standards Impact, host Dave Walsh is joined by Mark Lavach (Arkema) and Julia Farber (Eastman) to talk about these and other issues. During the conversation, Lavach and Farber drew on their expertise to address key questions related to biodegradable and compostable plastics, discussing ways these new materials could affect the ways the world uses plastic. They also spoke about the value of ASTM and how its members are shaping the future.

Read an excerpt of the conversation below, or listen to the podcast here.

 

Dave Walsh: Let’s talk about biodegradable and compostable plastics. It's almost like the Holy Grail in the consumer's mind. “Oh, I don't have to worry about plastic anymore. It's just going to dissolve into the ground.” I wanted to ask you both – and I can see you smiling. Is there such a thing as a truly biodegradable or compostable plastic? And what are some of the technologies and materials that might make that possible?

Julia Farber: I think the first thing that we need to really clarify is that plastic is a property of a material. This is where it gets interesting and why this particular committee [D20] has such a wide variety of potential topics it could cover. We're talking about something that carries a whole variety of different properties. But essentially, A plastic is just a material that's able to retain its characteristics when it's warmed up and then it's cooled.

This fundamental question: are there really biodegradable or compostable plastics? Yes, there absolutely are. We need to be clear about what we mean when we say something is biodegradable, when it's compostable, and when it's biobased, because there's a lot of confusion about these particular terms. Biodegradability and compostability indicate an attribute that's been designed into a material so that at end of life, it will break down into in a way that is compatible with the ecosystem, in a way that is benign, edible for tiny microorganisms to be digested, and then will completely dissolve and disappear.

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What we want to make sure is that you design a compostable material intended to help ensure that you are not creating additional complexities for certain kinds of waste collection systems. In particular, the food waste system. You want to develop something that's super compatible with the food waste system so that you don't create problems for the composter and you're creating quality soils at the end.

A biodegradable material might be one that you want to design if you know for a fact that the product has an intention to interact with the environment in a way that it sheds microplastics, if you have a textile that sheds, a tire tread that rubs off in use, or a fishing net that's going to interact directly with water. For something that should fall off or something that's really difficult or impossible to collect, it should be compatible with the ecosystem in a way that it will not create some sort of deleterious effect.

There's also a lot of excitement about a home composting system. ASTM is working on a test method right now to do home composting. And we are also working on a test method in conjunction with D34 to do real world degradation scenarios for when something ends up in a landfill and has compostability elements to it, but isn't in a composting situation.

ASTM is trying to reflect real-world human behavior – to dispose of certain kinds of materials and make sure that if that behavior is pursued, this material will not remain in the environment or become a problem for any of the parts of the biosphere it interacts with.

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Mark Lavach: When you look at the media, you see what's going on. You hear about terms like microplastics. Julia mentioned shedding. We don't want these products as they degrade to form microplastics. We want them to become one with the environment.

We are very aware of the effects of these processes. And it's all tied back to the environment. Biodegradable polymers are a very important class. Julia mentioned biobased polymers. If you look at the Ellen MacArthur Foundation, they have a wonderful chart that describes this whole area of bioplastics, of which biodegradable materials are a very important part.

But there are also plastics that will never be designed to biodegrade. You don't want a piece of pipe, for instance, to degrade. You want it to last a long time, but that doesn't say it can't be made from a biobased material. It won't biodegrade, but it will help with, say, depletion of natural resources. It's another important element of this, so you have to look at the entire picture. Biodegradable plastics are very important, especially, and the way to go for short-term duration plastics. Biobased plastics are an alternative for much longer-term duration projects.

Farber: Thank you, Mark, for homing in on that. A lot of people do get them confused. They think if something's biobased, that means it is biodegradable or it is compostable. We want to encourage people to know what they are really looking for.

If you want to talk about end of life, you're looking for a certified compostable plastic, because that means it's been through a test method and it has been demonstrated to meet our standards. ASTM is the global leader on this particular topic. We have the leading test methodology that's out there.

To listen to this and other episodes, visit Standards Impact here.

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