smarter composting (skip the gimmicks!) with u.s. composting council’s cary oshins

HAVE YOU MADE room in the compost heap for all that incoming organic material about to be created during your fall cleanup? Compost is today’s topic with Associate Director Cary Oshins of the US Composting Council. And we talked about everything from best how-to practices to improve your results, to all those claims about compostable plastic bags, and also in-home devices promising to make instant compost. (Really?)

Cary Oshins is a life-long backyard composter, besides his day job at the composting industry group that was founded in 1990 to promote compost utilization and recycling of organic materials to benefit its members, society, and the environment.

He lent some of his insights at this key moment in our composting year.

Read along as you listen to the Oct. 11, 2021 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

composting advice, with cary oshins

Margaret Roach: Hi, Cary. How are you—and how’s the compost [laughter]?

Cary Oshins: Heating up, as we say in our business.

Margaret: Cool. No—not cool. So, you’re composting in your backyard in the capital region of New York State. But before we get started with that and some of your insights and tips and advice, I wanted to just know quickly about the US Composting Council. What does it do? It’s kind of an industry group, yes?

Cary: Yes. Just like any industry needs a professional association to support itself and educate itself and advance the industry, we have one. So the US Composting Council has about 800 members, and those members are mostly companies that are engaged in manufacturing compost. Some of them are municipal. Some of them are private. Some of them are non-profits. And they run the gamut from small, community-scale compost, to mega-facilities that bring in literally thousands of tons a day to make compost out of.

Margaret: Wow. At home you’re not doing thousands of tons a day, I know that [laughter]. But you’ve been doing it as long as you’ve been gardening, I think for decades, just like me, yes?

Cary: Oh, absolutely. Since back in the college days, when I moved into a community household, and there was a garden and we learned about, “Oh, you have to make this compost stuff,” and started doing it then.

And I remember my first year collecting all the leaves and making a pile and then going out in the spring after it thawed and digging into it and nothing had happened. Oh my God, I was so upset [laughter]. I said, O.K., there’s more to this than I realized then. And that started me on a lifelong journey. And really, when you do it right and pile up these materials and it gets hot—that’s just a miracle to me, and that has kept me interested in it.

Margaret: Yeah. So do you follow any kind of rules? Because if you read books, garden books, everybody has their advice on this is right, and this is wrong, and this is what goes in and what doesn’t. So what about you? What’s your set of guidelines?

Cary: Yeah, I’m pretty liberal in what goes into my compost pile. I guess I’ve been doing it long enough that it’s pretty hard to mess up if you follow some basic rules. Things like keeping it moist, not too hot, not too dry, don’t overload the food so you don’t get smells and maggots. There’s some to some basic tips I’ve learned over the years that have helped me keep my composting going even over the winter. And yeah, as you mentioned, last year I moved up to the capital district of New York after 12 years in California, so it’s a different environment. I had to relearn some of the things that I learned growing up, up here in the Northeast. But it was successful.

Margaret: So you said, for instance, not putting in too much food, and by that do you mean like kitchen wastes and so forth, which can attract … People worry, they write to me a lot, they say, “Oh, I’m afraid I’m going to get animals, blah, blah, blah.” I just kind of dig a hole [in the compost pile]. I keep a fork or a shovel out by my heap, an old shovel, and I just kind of stick it in and wedge a hole and throw the food stuff underneath a foot or two.

Cary: Yeah, absolutely. My favorite tool is a garden fork. But yes, digging a hole, putting the food scraps from my kitchen into it. And then stirring it up also is really important so you don’t have clumps of the food, but you kind of coat all your new food with the active compost and the worms and the other insects and bugs that are in there. That’s a really important thing also.

I was speaking to a friend of mine this weekend about this podcast, and she said, “I don’t understand this thinking about turning. So how am I supposed to turn my pile?” And she’s right. You read these instructions from Cooperative Extension or whatever, and they say turning your pile can be very beneficial. It’s also a ton of work.

I think the operative term here is mixing more than turning. So you’re not turning the whole pile, but you’re mixing in these fresh ingredients into the active compost. And then yes, topping it with some leaves or some straw, or just some other of that “browns” that we always talk about, putting that on top to capture any odors that might be coming off of it. That’s much simpler than actually just turning your whole pile.

Margaret: Right. And you spoke a minute ago about not putting too much of something in one place, like the food scraps and so forth. And I think that’s really true with any ingredient. You don’t want to put… You just said brown, the things that are carbon-rich, I think, versus green, the things that are nitrogen-rich, I guess. In any case you don’t want to put 10 feet thick of one thing, because it’s not going to make a good chemistry, right?

Cary: Right. Although the other trick and challenge was this idea of 3-to-1 ratio [my friend mentioned], and three parts browns or high carbon materials to one part green or high nitrogen. And those ratios are true when you’re starting a pile or if you’re building a batch. But most of us don’t build batches of compost. Most of us are kind of doing this process of always adding a little bit of one, adding some more of something else. And so those ratios are hard to make sense of.

And then I said, don’t worry about it. As long as you’re have more of the bulky material to the food, and as long as you’re mixing it in, that’s really what’s important. And don’t worry so much about the ratios. Unless if you want to have a hot compost and do a batch, yes, those ratios are important. But for the vast majority of us that are not doing that, that are just adding our kitchen scraps to our pile day-to-day or week-to-week, the ratio is less important than thinking about having not those big clumps. I think that’s a good way to put it.

Margaret: Right. Our kitchen scraps, and of course our garden wastes, which are about to be prolific in my case—my pile is so big. It’s like 40 feet long and 8 or 10 feet wide and high [above]. It’s this ridiculous thing. And I mean, I don’t know where I would ever use all the finished compost I have over there, but whatever.

Do you compost sort of hot—you were speaking a little bit about hot, and what is hot and what does that mean? Or is yours kind of a passive pile that takes its own long, good time to get done?

Cary: Yes. Hot is important for the members of our organization that are making commercial compost and selling it to people, because the heat provides assurance that any pathogens were in there were killed, that weed seeds were killed, that things that could be toxic to plants are broken down.

But at a slower, more passive pace … Mine’s not completely passive, but it’s probably more passive than active. And so I get temperature rise. I have a thermometer because I’m in the business, so I can measure my compost temperatures and I see that when I add a charge of food waste, the temperature goes up maybe 15 or 20 degrees above ambient, but then it drops back down. It doesn’t stay hot. And my pile is certainly isn’t reaching what you read about as thermophilic temperatures. My piles are not in the one-twenties or thirties or forties or fifties or sixties, the way commercial facilities are.

But on the other hand, even last in the middle of winter, when it was well below freezing outside, the core of my pile never froze. It stayed active enough over the winter to keep breaking down. And really for me, the important thing is that I can keep adding the food scraps.

So even after a year, more than a year of living in this house, I have not filled up my compost bin yet. In fact, it’s only halfway full, despite adding every food scrap that I’ve made over the last year.

Margaret: I could bring you a few truckloads. I could bring you 70 or 80 truckloads.

Cary: I take pails, I don’t take trucks.

Margaret: Oh, O.K. All right. I’ve got to get my scale correct. O.K.

Cary: That’s right.

Margaret: So do you put in … There’s always these no-no lists like no bones, no plants with diseases, nothing with seeds, weed seeds. What about you? Do you have rules about that?

Cary: My rule is, don’t worry about it. Because I’m not putting in … I don’t put in a whole chicken carcass, but I don’t worry about a few chicken bones getting in. I certainly don’t worry about proteins like leftover … People, they talk about fats and greases. And again, I’ve got a pretty big pile. It’s 4 feet across. It’s a cone. So I can add those things and I bury them, and it’s not rat proof, but it’s pretty animal proof, like raccoons couldn’t get into it, or larger things can’t get in there. So I am fairly liberal about that. I know some of my cooperative extension friends would not like to hear this. [Above, the covered wire bin that Cary Oshins puts his food scraps into.]

And I also don’t worry about plants with diseases. I figured those diseases, if the plants got a disease, they didn’t get it from my compost pile. And those materials are going to be in my compost pile probably for a year before I get onto sifting it out and screening it out, so they’re not going to survive that environment.

Same thing with weeds. The weeds that are in the garden didn’t come from my compost. They came from someplace else. And so I don’t think I’m contributing to the spread of weeds through my pile.

Margaret: Right. The only thing I noticed is that … Because I compost sort of mostly passively, or around the same temperatures probably as yours, and not with a lot of turning and so forth, and it takes a year or whatever for this stuff to finish. And what I find is that certain really tenacious weeds that I have in the garden that sow a lot of seeds around, if I take that compost and put it in a vegetable bed or top dress it somewhere else in the garden, those weeds seeds will come up and I have to be aware of that.

And I have to either, before I use that compost, I could put like an old, I have a plastic shower curtain, and I put that over that and kind of solarize. Do you know what I mean? I kind of [crosstalk 00:12:05] weed seeds off on the part I’m going to use, or I just have to be aware and say to myself, hey, you know there’s going to be some weed seeds in here, Margaret, so when you put that on that bed, put a couple inches of good mulch on top of it too so that you’re not really encouraging everything to sprout at the same time. Do you know what I mean? I just have to be aware.

Cary: Absolutely. And also by adding the compost it’s much easier to weed. So yeah, you do see sprouts come out, but they’re easy to pull out as well. And try not to let them go to seed. That’s the biggest thing.

Margaret: Well, exactly. It would have been better to nip the bud off, literally, from the weeds wanting to set seed. And I’m just saying, sometimes they get ahead of me, certain things get ahead of me.

Cary: Sure. I mean, we do have municipal composting, or at least the township does collect compost, so some things that are really bad I may send to them, because I know their piles are going to get much hotter than mine.

Margaret: Good point.

Cary: So some things I might send that way, but not too much anymore.

Margaret: Yeah. So speaking of sort of how long it takes, how hot it is, etc. etc. I keep seeing on social media—the first time you put a word in social media, if you talk to anyone about compost, then you start getting these ads for things related to compost, of course. And I keep seeing these ads for like instant compost maker machines to have inside my house. And it’s like, what? What gives? Is there any such thing as instant compost?

Cary: No.

Margaret: Yeah. O.K., good. We finished that topic [laughter].

Cary: I, of course, get these also. And in fact, the claims are somewhat unbelievable. And while I would not want to use too-strong language, they do drive us crazy. Because you can’t make compost in 24 hours. Not compost the way we think of as gardeners.

And part of the problem is, is our language is a little insufficient. So to know what do we call this stuff that’s been dried and ground and would add organic matter to your soil if you use it. But we don’t really want to call it compost. It’s not mature. It wouldn’t pass any of the tests that my members use to validate that their compost is mature and stable and doesn’t have any bad aspects to it, or is unlikely to anyways. Those machines wouldn’t be able to meet those tests.

On the other hand, if you’re using them and if money is no object—because the other thing is they are super expensive. As long as you’re taking the product of that material and putting it into a garden … Maybe you want to bury it because it could cause some problems in your soil. I’m a little worried about how that material gets used.

It is keeping material out of landfills. And food in landfills does contribute to global warming. And a lot of the movement, a lot of the pro-compost movement we’ve seen over the last decade really comes from the recognition that food waste in landfills causes methane, a major contributor to greenhouse gases. So keeping that stuff out of landfills is really important. I think that you could probably do it cheaper and easier than these machines, but if that’s what floats your boat and you want to be one of the first people in your city [laughter] to have one of these, I’m not going to say don’t do it. [Below, red wigglers doing the job in Cary’s compost bin.]

Margaret: Right, but it’s not humus.

Cary: It’s not compost. It’s not humus, right.

Margaret: It’s not humus. It’s shredded, dehydrated-

Cary: Organic matter.

Margaret: …last night’s dinner [laughter]. That’s what it is.

Cary: It is. Exactly. And you’re using energy. You’re taking a process … One of the things we love about composting is that it’s self-heating. You pile this stuff up and it gets heated by itself. You don’t have to add energy to it, whereas these machines take electricity. You’re using power to do something that nature would do for you. It would take longer to do it, but what’s your hurry?

Margaret: I say, if you don’t want to have an above-ground big pile and you only have the food waste, dig a hole outside and do a little mini-pit composter. Or find a place for a bin or a tumbler outside and go for it.

Cary: Yeah. I think these are being marketed to people in high rises and condos. I don’t know who it’s being marketed to. I don’t know who’s buying them, actually.

I did see one that I thought was interesting because it was basically in place of your garbage disposal. So it would be put actually under your sink, and instead of a garbage disposal just grinding everything up and sending it to your sewage plant, it grinds it, but then separates it into a material that you then take it out and would be perfect if you’re going to feed it to worms, or you’re going to put it into your compost. But it’s already ground up so it’s small particle size. But actually it would be … I mean, again, there’s a cost involved, now you have the plumber and everything else, but I thought that was kind of a cool way. Like I said, especially if you had worms, because worms would eat this stuff up really quickly.

Margaret: Right. So there’s this other thing that I also see a lot, which is the claims on “plastic” bags, garbage bags, and grocery bags, and bags, especially plastic, and some kinds of food containers too, that say it’s compostable. What about that? Is that true? What do you know about that? What’s the Council think about that?

Cary: Yes. I know too much about that. That area of compostable products has really occupied a lot of my work-life for the last several years. And in fact, we just did a whole conference on it this summer. Because a lot of the information that you get on this comes from the manufacturers of other materials, not from composters.

So there’s a couple of different things here that I’d like to mention. One is that some of them are really compostable. And you know that because they’re certified, they’ll carry a seal. In this country that seal would be produced by the Biodegradable Products Institute, BPI. There are other organizations in other countries that put this material through … There are standards that says they have to disintegrate within three months and then fully decompose, that is, the microbes can use them as food within six months.

But those are only certified for industrial-scale composting. None of them are certified for home composting in this country. There are some of the organizations that will certify home-compostable, in Europe or in Australia, but not in this country. And that’s because this country they’re taking a more cautious approach and saying, it’s not just more time, it actually has to decompose in your pile.

And the problem is, what is a home composting pile? We have home composters from Arizona that maybe it was too dry and it never gets hot because of that, versus composters in Maine where it’s too cold and too wet. And so how do you make a material that you can certify as being able to break down in this wide variety?

At least at a commercial scale, we know it’s going to be 140 or 150 degrees. It’s going to get turned. It’s going to get managed to some extent. Whereas at a home level, we don’t have any of those assurances. So I think we’re being appropriately cautious in terms of certifying something for home composting.

Now those are things that are certified as compostable. And they should say, certified as compostable at a commercial facility. You may or may not have commercial facilities near you, but that’s what it takes.

If you see something that simply says biodegradable or compostable without insignia, that’s greenwashing. That’s just what that is. And I would not trust that. It’s probably not true, and certainly isn’t certified as true.

So in fact the US economic service that produces this, it’s the Federal Trade Commission, has a series of what they call the green guides that says what kind of environmental claims can someone put on packaging and what can’t they. And they’re about to revisit and renew the green guide. So we’re looking forward to seeing what they can do.

The problem then becomes enforcement. Who’s going to enforce? If one of your listeners sees something and says … In fact, I just got an email from a friend, it says, “I got this container. It says, compostable in commercial facilities. What would happen if I chopped it into little pieces and put it in my own compost pile?”

Margaret: Yeah. I think, no [laughter]. I think, no, let’s not do it. I mean, yes, we could test it, but … I don’t want to run out of time for one really important question that I need to still ask you about. If I’m a person who needs more compost than I can make, which a lot of home gardeners are, what should I be asking if I’m needing to buy compost?

I prefer to buy bulk and skip all the plastic bags, speaking of plastic bags. And I love a composted stable bedding, which has animal waste.

Cary: Horse manure?

Margaret: Yeah. And a lot of good nurseries, garden centers, can tell you, not necessarily the big-box stores, but private garden centers can tell you where there’s a local supplier or whatever.

But let’s say we can’t do that, or we only need a few bags. What do you say, as an expert and someone representing the industry? How the heck do I tell what to buy?

Cary: Well, there are a couple of ways to do it. First thing would be, we do have in our industry a Seal of Testing Assurance. And what that means is that the compost has to meet some basic minimum standards in terms of, was it produced at a facility that meets the environmental standard that’s permitted. It has to be tested. It has to pass pathogen tests, that is, it can’t have pathogens in it.

And has to include instructions for you. So what is this compost good for? Because compost that is good for, say, trees, may not be the same compost that you want in your flower pots. And so we actually designate compost as good for certain uses. Now, that program has started to take off. You might find that Seal of Testing Assurance, or it’s called CCUP, the Consumer Compost Use Program.

But if you can’t do that and you’re looking at bags, you can ask them to open a bag up. Does it look like something you’d want to add to your compost? And so often it’s hard to buy something blind. And so they should be able to allow you, or even have a bag that’s already torn that you can … Does it feel moist, or is it dry? Is it all twiggy, or does it have a fine texture to it?

Does it smell good? Does it smell like something you’d want to add or has it gone sour in the bag? Because that’s a sign that it was maybe too wet or it was bagged too early. So those are some things that anyone, if you have any experience with compost, you can use that to make some basic judgments on the material.

Margaret: Well, Cary Oshins from the US Composting Council and backyard composter, I understand you just put up a brand new garden gate, except it’s not a gate to the garden, it’s a gate to the compost area of your garden. A fancy gate, huh?

Cary: Yes. We built a new deer fence for our new garden [above], which is a no-dig garden. I’m sure you do lots of information about that. But we didn’t have a way to get from the back of the garden out to the compost area, so we built a beautiful new gate that goes out of the garden and into my composting area. [Below, the gate leads to an expanded composting area with a new three-bin system being built of pallets and more.]

Margaret: Perfect.

Cary: Happy to share that with you.

Margaret: Thank you for making the time today. I hope we’ll talk again soon.

Cary: I can’t believe how fast the time flew. It was such a pleasure.

Margaret: Indeed it does. It’s a pleasure for me, too. Thanks, Cary.

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Oct. 11, 2021 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).