Red to Green Talks: The Complexity of Composting

In this very special series, we are sharing excerpts from Season 2 of the excellent Red to Green Podcast created by host and future food enthusiast Marina Schmidt. The show features in-depth conversations about the intersection of the food tech industry and sustainability. Season 2, titled ‘Plastic Alternatives’, is dedicated to the world of food packaging with a focus on exploring alternatives to fossil fuel plastic materials and solutions.

What is the difference between industrial compostability and home compostability?

The below conversation is an excerpt from Red To Green Season 2, Episode 2: Bio-degradable, Compostable, or Recyclable? The Differences and Misconceptions. In this episode, Marina Schmidt, founder of Red to Green Solutions talks to Julia Goldstein the author of the book, Material Value which was a finalist in the 2019 San Francisco writers contest.

Audio transcript by Descript, with edits by Anya Roschke.

Marina: So what about compostable? There is industrial compostability and then there’s home compostability.

Julia: Yes. And it is an important distinction. To be industrially compostable, a material has to break down to fragments of a certain size within a certain time period, generally six months. Although there are some composting facilities that’ll create compost in about eight weeks, it’s also got to be nontoxic.

You can’t have heavy metals in there. There are very strict requirements. You don’t want lead, cadmium, those kinds of toxic things in the compost. But industrial composting facilities, grind everything up so they can take fairly large pieces. For example in mine, where I live, our curbside yard waste takes all kinds of stuff, food waste, compostable packaging, and branches, and leaves. And branches just need to be less than four inches in diameter.

I mean, that’s fairly large, but they can grind them all up. They heat them at a high temperature, they control the water content. They control the temperature and humidity very precisely. And they receive such a large mass of stuff that they can get the mix they need. “To be industrially compostable, a material has to break down to fragments of a certain size within a certain time period, generally six months.”

But, if you compost at home, you don’t have that scale. You probably don’t have a grinding machine that is going to grind up everything into small pieces. So, it’s going to take a lot longer to break down. Now it will break down, but if it’s not going to break down fast enough, you’re not really going to be able to have the compost. And then there’s also the issue of the right amount of green matter and Brown matter, right?

Green [matter] is more like the Apple cores recently fallen: leaves, grass, trimmings. And the Brown is like the Brown leaves. You can even use shredded paper, that kind of thing. And so you’ve got to have the right balance and you have to have the right amount of water in it. So people do home composting, but you can’t just toss in anything and assume you’re going to get good compost.

“To be industrially compostable, a material has to break down to fragments of a certain size within a certain time period, generally six months.”

Julia Goldstein

How does composting work in different places?

Marina: Yeah, and it takes a certain dedication to do compost, to actually also have the space to be able to do it. I’m not sure if you would want to have that inside the house. Actually, if you even find the space to have it inside of an apartment.

I saw a documentary today where it was mentioned San Francisco incentivizes citizens to do industrial composting because they have to pay more for putting things into black bins. Whereas they pay less if they put things into the composting and the blue recycling bin so that I found quite interesting and they seem to have quite a bit of success with actually picking up the trash and creating good compost, which is used on local farms, et cetera. 

How often do you already put plastic, like compostable materials in there?

Julia: I don’t tend to have those except for the bags of course. So, my little three-gallon container, I line with a compostable bag and those are actually made from agricultural materials like corn stalks and things like that. So those are the main source of it. I don’t tend to have a lot of those compostable plastics but I can tell you that a lot of people put stuff that doesn’t belong.

I went to Cedar Grove, which is the name of the company that does our industrial composting. They have a facility where you can go and you can pick up a whole truckload of compost or mulch to use in your garden. I did this and I looked at it. At one point, there was a piece of those stickers that we have on fruit and a little piece of a plastic straw and something that looked like it was one styrofoam and these were all in my compost. So they try to screen out contaminants like that, but obviously, they don’t do it a hundred per cent.

Part of the message is that it’s everybody’s responsibility to put the right stuff in the right place.

“It’s everybody’s responsibility to put the right stuff in the right place.”

Julia Goldstein

Marina: In Germany, as far as I’ve been living in Berlin, I have never had a composting bin here, in terms of it being provided by the landlords. This is shocking because Germany prides itself to be so big on recycling. It would be really interesting to me to look into the future. What if we would replace the recycling facilities with industrial composting facilities and replace all of them let’s say non-compostable plastic with compostable options? How would these two different scenarios measure up?

Julia: Well, I do believe that expanding composting is really a good thing in the United States. I read that only 2% of communities in this country have access to this kind of curbside composting of food waste that we have here in Seattle. Most people don’t have it, but it could certainly be added, but yes, you need to build more composting facilities.

How would this impact recycling?

Julia: I wouldn’t say to just get rid of the recycling facilities, because it’s not going to be easy to just get rid of conventional plastics. And there are also issues in large-scale switching over to bioplastic alternatives because those are made from plants. And the question is, do you have acres and acres of crops that now you’re growing to make plastics?

“Only 2% of communities in this country [the United States] have access to this kind of curbside composting of food waste that we have here in Seattle”

Julia Goldstein

Marina: Hmm.

Julia: Ideally those would say, come from agricultural waste, which to some degree they do, especially if you think about the fiberboard boxes that replace styrofoam, like if you get a takeout meal and it looks kind of like cardboard, but it’s not, it’s a fibre that’s made from say the wheat stocks.

There are trade-offs, right? If you just, suddenly, on a large scale, make a shift, it’s not necessarily going to go as smoothly. And just thinking that as long as you’ve got compostable plastics, all is well. They don’t contribute to the nutrient value of the compost. If you put in food scraps and leaves and branches, those have value. Those have nutrients that help make the compost healthy for growing plants and vegetables. But taking a compostable plastic fork and putting it in there. Yes. If they chop it all up, it will degrade and it’ll degrade into pretty much carbon dioxide.

That’s not really helping the compost. And so some cities here don’t take those, like in Portland, Oregon, they don’t accept those kinds of plastics into the compost.

Is the way forward a question of priorities?

Marina: But, I mean, that’s also a question of priorities and that scenario, getting good compost and getting good soil seems to be the priority. But then if an industrial facility has the priority of replacing plastics as good as possible and therefore composting the alternative products, even though the soil may not be as good, that could still be a good option.

Julia: Yes. And I think, especially in places where you’ve got food service too, a lot of people and well, someday we’ll have large outdoor events again, like music festivals or sporting events. And there, if all the food comes in compostable packaging, then it can all be dumped into one bin at the end and taken for composting because of the idea that, oh, then people have to separate out.

And if it’s recyclable, then it is contaminated with food, which is a mess for the recycling system for those kinds of things. I think providing all the food in compostable containers and with compostable serving ware is a great solution.

“I think providing all the food in compostable containers and with compostable serving ware is a great solution.”

Julia Goldstein

Marina: Yeah, but it seems to me like plastics is definitely not the way forward. and therefore there needs to be some good alternative solution. And as you described in your book, plastics are not such a novel technology they’ve been created in the forties, fifties, and so on mostly. So, there could be such an opportunity to have new innovations, which are actually now cutting edge, replacing something that we’ve been using for many, many decades.

A take on the way forward

Marina: So what is the path that you see forward towards a more sustainable food packaging solution?

Julia: I think there’s a mix of things. Sometimes the best packaging is no packaging at all. For example, if you buy a bunch of bananas in the store, do you need to put them in a plastic bag? They’re already in their own packaging, the banana peel, but plastics do have a benefit in keeping things fresh. For example, carrots, if you just put them by themselves in the fridge, they quickly become all limp, they don’t even last a week, but if you put them in a plastic bag, they will last.

I think there are probably many opportunities for businesses throughout that supply chain to minimize the amount of packaging and some of it is necessary to protect the food. Right? You’ve got this trade-off: if you don’t package things at all, you’re going to have a food waste problem because the food is going to arrive in a condition that it’s damaged or spoiled.

But there are opportunities like these plastics that are based on proteins from shrimp shells. One example is also milk-based proteins. Those can be made into a stretchable film. And I think using that for say wrapping cheese would be fantastic. A film based on milk protein that then just will dissolve in water almost. That could be really good, but you have to explain to people how to use it.

Marina: Hmm, what would happen with that? Milk-based protein film once you’re done with it, would that go into the compost.

Julia: Absolutely.

Marina: But wouldn’t that be filtered out in, I don’t know where it was, San Diego? No. Where do the plastics or plastic looking materials get filtered out?

Julia: In Portland, Oregon, they don’t want to accept those. But what they’re talking about is stuff made from PLA. Polylactic acid, which is a type of bio-based plastic, meaning it’s made from plants often corn, wheat, sugar cane, but it looks like a conventional plastic and it will technically biodegrade. But not easily. That is the specific type of bioplastic or compostable plastic that Portland says we don’t want. But something like this film, based on a milk protein, should be absolutely compostable. And I would think it should be accepted everywhere but it’s not in common use yet.

Marina: That’s very interesting. Good that we clarified this because PLA, at least in my head, is just one way of having a compostable plastic alternative. But then you have all of the other variations that are being developed right now. Various companies working on waste-based solutions, but also we may have, I have some other companies that use other feedstocks. So it’s really good to know Portland has not said, well, anything that looks like plastic or anything that is called industrially composted we are not allowing, but they’re just not allowing PLA specifically.

“Sometimes the best packaging is no packaging at all.”

Julia Goldstein

More on PLA

Marina: What is your opinion on PLA?

Julia: I think it’s useful. In some cases, like I was talking about, especially for take out food and you can just take the whole thing when you’re done with it, whatever scraps are left and then put it in the compost, but for an everyday solution, I don’t know. I see it being a problem. And part of the problem is labelling because I don’t want to have to take out my reading glasses to figure out whether my cup is made of PLA or something else.

“Part of the problem is labelling because I don’t want to have to take out my reading glasses to figure out whether my cup is made of PLA or something else.”

Julia Goldstein

And is it compostable? Is it recyclable? I think labelling is going to be an important part, you need to make it very clear to people and there’s a natural food market in my neighbourhood. They have some new compostable packaging that is very clearly labelled it’s PLA and it says, compostable packaging do not recycle. It’s large and obvious enough that someone would see that and know, but a lot of people think they can just put it in the recycling. It’s a plastic cup, but it will contaminate the recycling.


The Red to Green Podcast is available on iTunesSpotify, and all popular podcast apps by typing in “Red to Green” in the search bar. Listen to this episode of Red to Green here.

Want more? Check out the whole Red To Green Talks series here.

Lead image courtesy of Nareeta Martin (Unsplash).

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