165: Become a Microbe Farmer: Make Compost

Composting is taking diverse organic material and making a habitat for the microbes that will process the material. Jean Bonhotal, Director of Cornell Waste Management Institute in the Department of Soils and Crop Sciences explains that there are three necessary ingredients to make a great compost. First, the pile should start with carbon-like woodchips to help move air through. Second, add in wet waste like food or pomace. And third, top the pile with carbon.

The most important factor in making compost is temperature. In fact, you do not need to turn piles. The organisms that break down compost generate temperatures that are about 90 to 150 degrees Fahrenheit. A great example of this is seen in mortality composting, used for livestock. These piles are created by layering 24 inches of woodchips, followed by the animal, and top with another 24 inches of wood chips. The animal will liquefy and then everything starts to mix as the microbes work. In 12 to 24 hours the pile will reach the desired 130 degrees Fahrenheit.

While compost is not technically a fertilizer it has numerous benefits including imparting nutrients, pest resistance, helping with erosion control, and improving water holding capacity because it works like a sponge. Listen in to hear Jean’s best advice on how to create great compost.


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Craig Macmillan  0:00 

My guest today is Jean Bonhotal. She is Director of the Cornell Waste Management Institute. And he's also a Senior Extension Associate in the Integrative Plant Science Soil and Crop Science Section at Cornell University. And we're talking about compost today. Thanks for being here, Jean.


Jean Bonhotal  0:13 

Thank you.


Craig Macmillan  0:14 

I like to start with basics when we're talking about a topic. And sometimes it seems kind of silly, but it oftentimes shapes what we talk about. Let's start with a very basic definition. What exactly is compost.


Unknown Speaker  0:26 

So I'm going to start with a definition before I get into composting, and that is what is organic, what is organic? When I'm using the term organic, this is what it will mean something that was once alive and is now dead, and needs to be managed. That comes with all different types of quality. But we are usually looking for clean feedstocks, that are organic in origin. So we don't want glass and plastic and other materials that really don't break down and have put a lot of plastic into our environment, because they break down into little tiny pieces, and they're still there. So I'll start with that. Composting is basically taking organic material, all different diverse, organic materials, preferably, and making a habitat for microbes, the microbes that are going to process these materials. When we're composting, we can do all of the work mechanically. But it doesn't really work that well because composting is a process. And if we set it up so that we have our carbon and nitrogen ratios, well balanced. And those are browns and greens, wet and dry materials. So those are the things that we need to balance, then we will have a proper habitat for the microbes to work in and they will thrive. The microbes are what make the heat in a compost. When we're composting very small volumes, we don't always have heat. And that's because we don't have the volume that we need for that composting to happen in commercial scale, we generally will have enough volume. So as long as we balance that carbon and nitrogen, we will have a very good compost that will actually work mostly by itself.


Craig Macmillan  2:29 

So you need different kinds of microbes for taking action on different types of materials, whether they be high nitrogen or high carbon or whatever. Where did those bacteria and fungi, where do those come from?


Jean Bonhotal  2:40 

They come from everywhere. They come from us breathing on the medium that we're putting in there they come from the air, their bio aerosolized is what we consider. So these things blow in, and we really don't have to inoculate most composts. The only reason we might need to inoculate a compost is because we've shut it down. Either we've put something in there that's too toxic for the organisms to work with, or we've made it too hot in that pile. The organisms that we're working with are thermophilic organisms, they generate temperatures that are about 90 to 150. And the actual range for thermophilic is more like 130. Those are the temperatures that we really like to reach 130 to 150 is really degrees Fahrenheit is really the temperatures that we want to heat want to reach.


Craig Macmillan  3:42 

And that's because those are the ranges where these particular microbes are the most happy.


Jean Bonhotal  3:46 

Yes, and the microbes are actually generating the heat. It's like putting 55th graders in a room you don't have to heat. They're giving off lots of energy and have to do anything else. They're doing the work and metabolizing all of that material.


We were talking about a range, what if we're not generating enough heat? What kinds of things happen then? Or what can we do to change that?


Well back up because that is dependent on size. So we have to have that volume and that and if we look at physics, that volume is three by three by three feet cubed. However, when we're working in cold climates, that is not large enough. So everything will freeze really, we have to have everything so perfect with that three by three by three cube that we're not likely to reach those temperatures. So it's really balancing the carbon and nitrogen the moisture. And because if like in arid climates where everything dries out horribly, we need to make sure there's enough moisture retained in that because these are aerobic organisms that are doing all the work. And we really need to make sure that they have that moisture, or else they can't really work. People think that worms make compost, and to an extent they do, there's vermicompost. And it's a different than thermophilic composting that I'm talking about. But Vermacomposting is done with epigeic worms. It's done in a 24 inch bed. So you're making that compost in kind of a shallow bed so that it won't heat up, because the worms are actually doing all of the work in that system. When worms come into a compost, or thermophilic compost, that's at the end of the process, they can't tolerate the heat in the thermophilic process. But they do like to process those organisms that are in there. So they will go in and actually process some of that material toward the end. And in some ways, you can tell that you have a more finished compost, because worms are actually able to thrive in there.


Craig Macmillan  6:07 

Where did the worms come from?


Jean Bonhotal  6:09 

Generally from the ground, if you're composting in a vessel, you're not going to have worms in there unless you had like warm eggs or something that were already in the medium, and hatched or something like that. So that's where those are coming from. So like indoor facilities generally wouldn't have an earthworm coming in and processing. And the epigeic worms are surface feeders, so they're coming up, they detect that something's up there to eat. And they'll just come to the surface, eat it, pull it down, up and down, you know, they can actually handle above 54 degrees, where a lot of worms dry out and die there. As they get if it gets too hot, and they get too dry.


Craig Macmillan  6:57 

You had mentioned the right mix or blend the right kind of connection of different materials and other recipes that that work for certain practical applications are given certain materials, you want certain ratios, how does that work?


Jean Bonhotal  7:10 

There are recipes out there. But basically, you have to look at everything as carbon and nitrogen. So if you're a vineyard that wants to compost, the pumice, all your all your promise while you're squeezing all that kind of material, then you're gonna have to look at that and figure out whether that's going to work by itself, just that promise. But you do have grape skins, and you have grape seeds in there. So the grape skins and the grape seeds actually can work together to create a good habitat and actually make things work or you have a pH of about four or five in those pressings. That's going to deter worms for a while it is going to deter some other organisms for a while, but things will start to get going. And that's how we tend to do that. If it's really sloppy and wet, it would be better to add a little bit more waste, but another waste, marry it with another waste, whether you have some manure or you know the if there are some animals on site, if you can mix in manure, or some shavings, or I don't usually like to put wood chips in because it makes a coarser compost for a vineyard. And we want generally want to find our compost.


Craig Macmillan  8:30 

Which actually reminds me of something. There were two things that I had learned and that they may not be true when I was coming up and we're talking like 20 years ago. One was that you had to have manure as part of the mix, some kind of a manure there was one and then the second one was forget about using any kind of wood chip vines, anything like that, because they're not going to break down. And that's not going to work. So how is that accurate for either this ideas?


Jean Bonhotal  8:54 

No, we have to use all of our carbon sources. Honestly, we do have to use all different carbon sources in different types of composting. I'll give you an example of facilities that by regulation, they're only allowed to compost leaf and yard waste. So they're not allowed to bring in food unless they have a permit to bring in food waste. So there's a lot of different rules that occur over municipalities. Some municipalities got the idea because they needed more nitrogen, there's a lot of carbon and your dry leaves and your woodchips and your woody waste. And I generally will say if I make a pile of sticks, which is all carbon, so all all different sticks and just put them in a pile. If I go back six months later, what is it going to be?


Craig Macmillan  9:42 

Dried sticks?


Jean Bonhotal  9:43 

A pile of sticks, because I don't have any real nitrogen there is nitrogen in there but I don't have enough in there to make that break down. So I do like to size reduce those chips, the woody waste and that's chipping off or grinding or something like that. And that will make things go better. If you need to compost just leaves, what the municipalities were doing was adding chemical fertilizer to them. Because the chemical fertilizer would bring the nitrogen in, you have to decide do you want to use the chemical nitrogen, the chemical fertilizer, or not in your process, but that will make it work because their carbon and their nitrogen, and we can do that.


Craig Macmillan  10:27 

Do I need to do some analysis on these materials and figure out what I actually have and then make calculations from there.


Jean Bonhotal  10:33 

So the ratios that we want to use are two to three to one. So I have a good picture of a bucket. And it could be any bucket, think of a cottage cheese container up to us eight yard bucket, I want one bucket of wet material, a very wet material. And then three buckets of very dry material. That's how we balance those ratios. But we are really some of it is like It's like making bread, we don't dump all the flour and all the water in at one time, we put in a little bit of time, because we need to balance out what that recipe actually needs. And the same thing happens in composting, the operators get very good at knowing, okay, that's really, really dry material. And that's really, really wet material. And I might even need to make because we can compost liquids, I might need to make a bowl to put that liquid in there or that really wet material in there so that it can stay in the pile. So I can use that moisture, mix it with the woody waste, and allow that to happen.


Craig Macmillan  11:42 

This is beginning to get kind of intimidating. I was kind of hoping that I just would throw a bunch of stuff in a pile and walk away and come back and magically I now have compost.  Yeah, how do I figure this out, I guess we're gonna get my education?


Jean Bonhotal  11:58 

So one of the ways we do small scale composting is we layer the materials in so we'll have a bin and we'll put carbon down at the bottom, make sure we have a good carbon layer because that's going to act as an air plenum on the bottom. So simple, just woodchips a pallet, something that's going to allow air to come in, then we'll put nitrogen or put in our wet waste, our food waste, our pumice, those materials, we're going to put carbon on top of that. So we never should be able to see what we're composting, it should always look like a pile of comp of compost. But I will talk a little bit about mortality composting and how we do that, because it really tells us how the whole thing is supposed to work. And what we do is we put down 24 inches of woodchips, then I'll put a cow in. And then I'll put 24 inches of woodchips over top of that, what happens in that is the cow starts to liquefy. And then it starts to mix with all of the material, all the all the microbes are starting to work. And everything starts mixing together in a very slow motion in 12 to 24 hours, I should have 130 degrees Fahrenheit in that pile. If I don't, then I've built it wrong. But generally even with we're composting right now with frozen animals, and we're able because of the size of our piles, we're able to do that, that heats up. So whatever the pile is, or the windrow is that heats up, and then the heat rises, and it actually convex around that that medium. So the organisms are getting all that and we don't have to do any turning. We don't have to turn at all. So we don't always turn and if I do that layering like I was talking about in a bin, if we layer it in a bin, then we will be able to do that and walk away and just let the rain and snow fall on it through the season. It'll be slower, but it will compost.


Craig Macmillan  14:11 

So again, I had been under the impression that you always have to you have a regular schedule, you have to turn it to aerate it. And you also have to monitor the moisture. No you do not.


Jean Bonhotal  14:19 

No. No. The only real tool that we use is temperature. We monitor temperatures in piles, we can tell everything that's going on in that pile is that making sure that it's working well or we need to add more water or we need to whatever we can tell that by temperature.


Craig Macmillan  14:39 

If the temperature is getting too high. What do you do?


Jean Bonhotal  14:41 

I do compost in arid places where our temperatures can get really high because our piles are too big. Okay, and then we really have to be careful because we can have spontaneous combustion. And our large ones I worked with some facilities in Idaho that around the Boise area, and they were in danger of combusting. And as they were like, what do we do? Well, if we add a lot of air real fast, we're going to be in trouble. If we add a lot of water real fast, we're going to be in trouble. So what we do is we, we will break those piles carefully, break those piles down, just deconstruct those, lay them in sheet, and then just make sure that they've cooled off, then we can build a pile again, but it can be a problem in hot and arid climates. And it can happen anywhere there are different manures like poultry manure will burn more easily than other manure because of the ammonia contents. Because of the just the nature of that material.


Craig Macmillan  15:45 

What kind of temperatures are we talking about?


Jean Bonhotal  15:47 

When we're getting over 170? I get nervous, especially if it's really hot, ambient temperature. We have to be careful about that.


Craig Macmillan  15:56 

Excellent. Okay, that's useful. That's that we can keep that we can track that ourselves. Now, before we run out of time. We have time I just want to get to this topic, because I think there's a lot here. Now, oftentimes, compost is treated like a fertilizer, you say, oh, there's nutrients here. And we're doing it for that reason. But compost will do a lot of other things for you in terms of your soil.


Jean Bonhotal  16:18 

Yes, and compost is not technically a fertilizer. So if I have a finished compost, it's not a fertilizer and doesn't follow the fertilizer rules. So there are rules that govern fertilizers and rules that cover compost, and so we have to be careful about that. So it does impart nutrients to our soil compost does impart nutrients to our soil, it helps with erosion control, it helps with water holding capacity, because compost acts like a sponge, and it will pull that moisture into the soil. And then the plants are able to use that when things get droughty. So we really want to use a lot of compost, if in my dreams, I would like to have three inches of compost spread on the whole terrestrial earth. Because I think we need it, it's the only way we can create or recreate our sustainable soils, our soils are very much bankrupt, we might put nutrients back on those soils, but we don't put the organic matter back on the soils, were able to take more of the corn crop. So less gets tilled in, and less of that organic matter is there so we don't have sustainable soils because of that. And compost can help us create and generate sustainable soils so that we don't have to do that. We don't have to constantly add fertilizer.


Craig Macmillan  17:49 

Now that leads me to a couple of other things. So in terms of application in vineyards, it's very common to band compost right under the vines in the vine round and not in the middle. Some folks are experimenting with full on broadcasting across the whole surface, right and this has worked really well in range land contexts, which is interesting. And then there's a question about whether compost needs to be incorporated into the soil or does it need to be cultivated in what are your feelings about that for you know, a soil that's maybe a clay soil relatively dry.


Jean Bonhotal  18:23 

I'll talk specifically for vineyards on this some vineyards will start their new plants their starts with like some vermiompost. And  vermicompost is a pretty popular product to use when we're putting our starts in. And these are like five year old vines that are just getting planted. And we really want these guys to go. So that will help with nutrients. It will help with soil aggregation, it will just make healthy soil. I have had a poster up before as because it says compost don't treat your soil like dirt. And that's really what we want to do. We want to compost we want to add compost so that we're not just dealing with mineral soils. And I think it's really important for us to be thinking about that way. So the adding a you know, an eight ounce cup of compost vermicompost into the holes is supposed to work very well. And a lot of people in California have actually experimented with that. From what I'm told. What their plant responses are, I haven't followed those. So I don't know. Broadcasting I've seen people more put it in the row middles so that they don't end up with a lot of bull wood in their vines because if they get the nutrients up against the vines at the wrong time, that can be problematic. So sometimes they'll even take immature compost and put that in the row middles. That keeps keeps grass down keeps weeds down, you'll still have some cover there. But then it slowly works its way into the vineyard.


Craig Macmillan  20:06 

When you're referring to row middles you mean under the vine?


Jean Bonhotal  20:09 

I mean, between the, the rows.


Craig Macmillan  20:11 

 Between the vines. Okay.


Jean Bonhotal  20:12 

Yeah, I've seen that done a lot in New York, where people are using it that way. And sometimes we'll use an immature compost because that we call it a killer compost, which we shouldn't, but it kills the area, and it won't encourage the growth in the row middles. And it keeps it a little bit away from the vine for a little while, then by the next season, that's all integrated into that soil system.


Craig Macmillan  20:39 

Fascinating. Fascinating. Now, what do you think about banding underneath the vine?


Jean Bonhotal  20:43 

By banding, you mean just putting it right against the wood?


Craig Macmillan  20:48 

Generally, just underneath the vine, not in the middle, the strategy there, I think is I'm trying to get a higher concentration, if you will, and I want to put it where the vine roots are going to be in. So they're going to be predominantly in the vine row, not not exclusively, but they're gonna be that's where the highest concentration of roots is going to be. So the idea is, hey, if I'm going to put five tons per acre on, let me put it on in a narrow band, like 18 inches, as opposed to, you know, eight feet, you know, in terms of in terms of width, it sounds like you're kind of more interested, if you would kind of recommend, you know, putting it in the middle as opposed to under the vine.


Jean Bonhotal  21:21 

I don't have enough experience with grapes to recommend. So I'm not going to make that recommendation. This is what I'm seeing in the vineyard, the way the growers are choosing to actually experiment and see what is getting the nutrients to the plant at the right time. So what strategy is, is working best. Using the vermicompost in the hole that's been very productive using some of the row middles. I'm not sure about banding I have no experience with that. So I don't want to speak on that. I'm more of the compost production cleaning up the best person. You know, what, when we get the calls, this pile over here, stinks by the neighbor, then I step in and and try to get everything more productive.


Craig Macmillan  22:13 

That makes sense that makes tons of sense. One other application that I do think you can speak to is erosion control. What role can compost have an erosion control.


Jean Bonhotal  22:22 

We do a lot of work with compost, and I'm gonna share with you some posters that will give you simple compost use instructions. We work in agriculture, we work in erosion control, we work in urban garden gardens and farms. So there's all different possibilities with all different compost and every compost, even the compost that aren't the quality that we want for our vineyard. Every compost has a potential use, even if it's just daily covering a landfill, so that we've taken those metals or those that toxicity out of the environment, and at least concentrated it in smaller places so that maybe it can be recovered at some point when we figure that kind of stuff out.


Craig Macmillan  23:07 

And the way this is working is that the compost is binding this soil somehow or is it reducing the impact of the raindrops or what's the mechanism.


Jean Bonhotal  23:17 

We do both compost blankets and compost socks and erosion control. So the compost blankets we have blower trucks that can spray compost, it's a big big hose, we spray compost onto a hillside, when we put that blanket down. When the rain comes if the rain comes in, it hits the soil, it hits the soil and it makes mud and that mud starts running down the hill. And that's erosion. When it hits the compost, the compost acts like a sponge. And that sponge will just keep sucking in that moisture. And then slowly release it like a sponge will. And so the plants can use it better and it doesn't create those rivulets and the erosion that other things do.


Craig Macmillan  24:10 

What kinds of rates per acre per square yard or what are we talking about?


Jean Bonhotal  24:15 

For it depends on per crop. When we put a blanket down, we'll put in out about a inch blanket. So that's a visual, and we want to make sure that it's well covered I'd put one or two inches down easily, because that will start incooperating. Remember I told you about those worms? The worms will come up and start processing some of that material. And that'll only be incorporated in the soil in that way. So we don't actually incorporate we will seed put the blanket down and then we might hydro seed on top of that blanket. And that'll create cover some kind of cover crop whether it depends on our goals. We'll put whatever cover crop we might put red clover on our roadside we might put, you know, depends on where we are what we're putting in, but usually a low grow local plant. So we don't want to take you know, a plant from New York and put it in California, it's not going to produce the same way. We want to make sure that we are in the right conditions. We have the right plantings and all that and Soil and Water Conservation Districts which are all over the country. They give you guidance on what should go on to slopes. What should go into row middles, it depends on the plants though, and cooperative extension does a lot of that, what application do we need for what crop. One of the things that we are finding with soil blends and stuff when we're trying to bring in topsoil topsoil has lots of different definitions, a lot of times it's sand. Because we can't get topsoil, it's very difficult, we've used up a lot of our topsoil, and we don't have that rich earth to bring to someplace else to put that topsoil down. So we're working right now on grow tests to look at what percentage of compost should be mixed with the mineral soil, or with close to mineral soil or with the soil existing soil. And one of the things that we're finding is that we can really use in most for most crops, and for soil sustainability to build those soils, we can use about 50% compost in all of those, and we're getting really good results with crops. It does depend whether we're growing cabbages or grapes, or we really need those soils to be more sustainable. If our soils are sustainable, they'll increase the water holding capacity, you know, through the compost application, but they also help with pest resistance. So we'll have more pest resistance, because we have healthy soils, we have more competitors that are actually able to take things out instead of working in a chemical system where okay, the cut worms came in, and the cut worms are really happy to be working in. There's nothing telling them not to. And similarly with powdery mildews and some of the other diseases, we seem to have better results with having a healthy soil. So not just dust that we've added fertilizer to.


Craig Macmillan  27:32 

Sure. And that makes total sense of any there are a lot of folks that are looking at this kind of a holistic plant science, plant physiology approach, which is what you're talking about. And there's a lot of exciting things going on and talking about compost being a part of it is really cool, basically at aout of advice or what one thing would you like people to know as far as their own compost production goes.


Jean Bonhotal  27:58 

If you're producing compost, you're a microbe farmer. And that's what you really need to consider create a habitat that they're going to thrive in, and they'll do all the work for you. And that is my best piece of advice to anybody.


Craig Macmillan  28:14 

That's great. And where can people find out more about you and your work?


Jean Bonhotal  28:17 

I'm with Cornell Waste Management Institute at Cornell University. You can you can google us pretty easily.


Craig Macmillan  28:25 

It's easy to find information about you. Yeah, and about the CWMI. So our guest today was Joan Bonhotal. She is the director of the Cornell Waste Management Institute. And she's also Senior Extension Associate with the Integrative Plant Science Soil and Crop Science section at Cornell University. Lots of great stuff is gonna be in the show notes. Again, we encourage you to look into this topic. It's exciting. There's a lot going on. Wouldn't you agree there's a lot of new science every year on this topic.


Jean Bonhotal  28:51 

There is a lot a lot going on in composting, a lot going on in sustainable soil production and if we have sustainable soils, we will be able to grow healthy food and sustain healthy people. So there's just so much going on with all applications of composting.


Craig Macmillan  29:12 

Very exciting.


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