Talkin' Crap

Timing is Everything: Reducing Methane Emissions with Manure Management

• Dan Andersen • Season 1 • Episode 13

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In this edition of Talkin’ Crap, Dan Andersen and Jake Willsea discuss how the frequency and timing of manure application can significantly impact methane emissions, with Jake's research showing that adjusting application timing can reduce emissions by up to 50%. They also explore the potential financial benefits of carbon credits. 

Methane Emissions Show Notes

This material is based upon work supported by the United States Department of Agriculture Natural Resources Conservation Service under a federal award number NR233A750004G072. USDA is an equal opportunity provider, employer and lender. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect views of the United States Department of Agriculture Natural Resource Conservation Services. In addition, any reference to specific brands or types of products or services does not constitute or imply an endorsement by the United States Department of Agriculture for those products or services.

Unknown:

Music.

Dan Andersen:

Hello and welcome to Talkin' Crap, a podcast by Iowa State University, Extension and Outreach. This institution is an equal opportunity provider. For the full non discrimination statement or accommodation inquiries, go to www.extension.iastate.edu/diversity/ext. In this podcast, we discuss insights into the science technology and best practices surrounding manure management. Our objectives are to build awareness about the challenges farmers and the broader agricultural industry face around manure and to demonstrate solutions in areas of innovation. Hello and welcome to another episode of Talkin' Crap. I'm your host, Dan Andersen, and I am joined this time by Jake Wilsea. And what we're going to be talking about is manure removal frequency and the impact it has on methane emissions. So one of the things we've been interested in is sort of what's livestock carbon footprint and what are some norm management techniques we can do to help with that, especially in light of the climate smart footprint that USDA and NRCS has been talking about relative to livestock production. So I'm going to let Jake introduce himself. He's a master student here at Iowa State working on a project with the 360 RAINunit, and got interested in methane emissions because of that. So Jake, can you tell us a little bit about yourself, and thanks for being back.

Jake Willsea:

Yeah, thanks for having me back. Dan, like he said, I am Jake Wilsea. I'm a master's student here at Iowa State in agricultural engineering, and my project is mostly related to manure application timing and how it affects both your nitrogen use efficiency and the methane emissions coming from storage.

Dan Andersen:

Perfect. And I think when you first got here, we hadn't talked much about methane emissions related to storing manure, but we decided it might be an important component of that project. Why is that? And what really got you hooked on trying to learn more?

Jake Willsea:

Well, I think methane and manure kind of go hand in hand. Some people use it as a tool to actually produce renewable natural gas through anaerobic digestion. But it's also kind of a negative effect of some of our storage techniques, that we get anaerobically digested carbon in that in those storages, and we're going to be producing methane that's going into the atmosphere. So as a greenhouse gas, we want to try to limit as much methane as we can going into the atmosphere Absolutely.

Dan Andersen:

And I think that's become more relevant and more important in light of some recent policies that we've seen out specifically, Smithfield has pledged to work towards carbon neutrality. JBS, the same. And we see a lot of that happening on the dairy side as well, with Nestle and Daisy all promising to work towards carbon neutrality and livestock production, and manure is an important component of that. So as we think about where to start here, the place I wanted to start is, we got manure, we're going to put it into storage. How do I come up with any guess of how much methane it's going to make? What's the science behind that, and what are we working from?

Jake Willsea:

Well, a good first starting point is really establishing what is the theoretical maximum methane that could be produced. So for that, we do what's called a biochemical methane potential test, or BMP, and you take your different types of manure and you put it into just a little sample into a jar, and basically measure at a controlled temperature how much methane it's going to be producing. And so you can do that for different types of manure. It varies farm to farm, but that gives you a good idea of what is your theoretical maximum that you could be producing.

Dan Andersen:

That's right, and that's been done for a fair number of different manure types, but we see farm to farm variation for things like changes in diet or ration that we might be feeding, or relative animal performance and feed conversion efficiency that they're experiencing on a specific farm. So there is some variability, but the general numbers that people have available at least, probably put you in the right space, right range, until we start feeding vastly different diets than what we've explored before.

Jake Willsea:

Right? But it's definitely a good starting point at least, to get an idea of how much you could be producing.

Dan Andersen:

Absolutely and those tests are pretty standard. People have done them for anaerobic digestion. So there is a nice database built up. The second part of that is, all right, I got this manure. You figured out the maximum. How do I know what it's going to make in my actual storage, my actual conditions? What are the factors that control that?

Jake Willsea:

Well, there's a few different factors. First is the actual availability of the oxygen that's in the storage. A lot of the time you'll have pretty low oxygen levels, and that's really why the pathway of methane emissions is favorable. But if you do introduce oxygen into that environment, then you get CO2 that's produced instead of methane. So that's one of the major factors. A lot of people will actually aerate their manure to force that methane to drop and the CO2 to increase, but a lot of the time it's just kind of, you know, forced to be that methane production. But that's one of the first drivers of methane production.

Dan Andersen:

All right. So the first thing is figure out if we're going to be aerobic or anaerobic conditions. Most manure storage, liquid manure storages, are going to be in those anaerobic conditions. So if we move towards solid it gets a little bit easier. Or we really have to do sophisticated things like aeration techniques to force air into it. Or really think about what's the surface area of this manure storage? How shallow do I have to keep it so that oxygen transfer from wind or diffusion can help me out? But generally, for liquid manure, we're stuck in that aerobic condition unless we're doing a really designed aeration system.

Jake Willsea:

Yep, the anaerobic condition.

Dan Andersen:

The anaerobic, thank you. And then what are the other things? So we're in this anaerobic condition. How good am I going to be at converting it into methane, or how bad am I going to be if it's something I want to eliminate? What? What controls that?

Jake Willsea:

So a lot of that is based on the inoculum, or the starting bacteria and microbes that you have in your storage. So in the case of a lot of lagoons, you're going to have this layer of sludge even after you empty your storage, and that really has this thriving, high level of microbes in there that will continue to break down that carbon. Now, if you're starting with an empty storage, or you're pumping out of a deep pit, and you have it almost completely empty, you're not going to have as good of an inoculum. So with that, you're probably going to have more of a lag time of where you would start producing that methane. But if you go into a lagoon where you have the sludge and that inoculum already started, you're really kick starting the process. So you'll have a bit of a boost at the beginning of your methane production.

Dan Andersen:

Beautiful. So, and I've done some work on this, really, and it's kind of interesting when we talk about that biochemical methane potential test. One of the things people were doing when they were trying to develop it is trying to figure out inoculum to substrate ratio. So how much manure Should I add to inoculum? Right? And they did exactly what you saw as in the end result, if I'm willing to wait long enough, we get to the same point, but by using more inoculum relative to substrate or manure, we can make that happen more quickly or slowly. So I think that's a big part of it, and definitely makes a difference. And you pointed out that lagoons hold on to more of that bacteria. They have the sludge you have to maintain some working volume in there, so they just have more of that bacteria to start with. We did some feeding trials west of town here in the swine nutrition farm, and one of the things that's interesting there is we always start with a clean manure tank. And and I do a lot of field work, and we think clean, well, I pumped up my deep pit, there's somewhere between six and 18 inches of manure left in. I got it empty and clean. And in this case, they're stainless steel tanks. We can tip them over, wash them out, scrub them out. They're perfectly clean. And one of the things we see there is the rate of methane production from that manure is much lower in that situation than it is in the field, and it's got to do with that inoculum ratio. So that one really makes a big difference as we think about different types of storages. But within a storage it it probably is based on our management, and it'll always be about the same from year to year. So anaerobic conditions, inoculum, what else is sort of controlling what we we make?

Jake Willsea:

So I'd say the two main driving factors that I like to look at are the temperature, because that really drives the microbial activity and the actual amount of manure that's in that storage. So the temperature, as you get into an increasing temperature, the microbial activity will increase exponentially. So just like you put food in a refrigerator, as opposed to on the counter, so that it doesn't break down quite as fast. It's the same for manure and a hot versus a cold temperature.

Dan Andersen:

And a good rule of thumb is, for every 20 degrees or so Fahrenheit, we increase in temperature, microbial activity would would double. So the rate we're breaking it down or making methane doubles with that temperature curve.

Jake Willsea:

Yep, and it can be kind of a challenge to control that temperature, if you don't do any, if you have no changes, no strategies to affect that. But if we did look into some ways to to strategically empty our manure storage so that we can control when that temperature peaks, that could be a good way to prevent or limit your methane emissions.

Dan Andersen:

So, what do you mean by that, like, how we're going to get the temperatures we get. What time should manure storages be a little colder, warmer, and how should we be conceptualizing that?

Jake Willsea:

Well, right now, a lot of people like to apply their manure in the fall, and by doing that, you have the most manure in your storage during the hottest time of the year. So you have July, August, September temperatures are usually the peak temperatures in the year, and you'll have your fullest storage if you're going to be applying in November.

Dan Andersen:

Okay, so really, you're saying trying to avoid being as full as we could be during those peak temperature months is one strategy to help with that methane production, just because it won't be sitting there when we're going to have the most accurate active microbial community.

Jake Willsea:

Exactly, or you could go to a different strategy of emptying more frequently, so that you're not quite as full during those hot months. So you could maybe apply twice or three times a year, and then, no matter what, you're staying at a low level in your in your pit, and you can limit your methane production that way.

Dan Andersen:

Okay, so two different approaches. One is to try and manage it so that we're as empty as possible during those more months. And the other one is just to limit how long it's sitting there altogether so it doesn't have as much time to get conversion. And I think one way to think about that is, when we think about typical conversion efficiencies, maybe of a deep pit storage, we might think we're converting somewhere around 15 to 20% of the potential methane production into actual production if we apply once a year. If we're out in a lagoon because of that better inoculum ratio that you mentioned, we might be more in that 60, 65% conversion. And if you go to a designed anaerobic digester, we're hopefully hitting that 75, 80% conversion sort of platform. So since all those storages are a little different to start with, each one of these practices manages a little bit different when we think about, sort of, some work that you've been doing. I wanted to talk a little bit about you looked at some strategies. Can you walk us through sort of you mentioned we're either going to focus on trying to control temperature, when the manure storage is full, or application frequency. So let's start with just changing timing of application. I think you looked at three different strategies of when we might apply manure and how that relates to what methane emissions could look like.

Jake Willsea:

Yep. So I looked at three different seasons that you could apply your manure. So I looked at a fall, a spring, and then a side dress, so that would be applying like around June 1, or right during the growing season of corn. The spring application, I modeled as April 15, and then the fall application, which is kind of our baseline, was November 1.

Dan Andersen:

Okay, so with your baseline case, that fall application once a year, pretty typical of what we're doing most at most facilities in Iowa, sort of, what did you see for methane emissions from the manure?

Jake Willsea:

So we we saw about half a metric ton of CO2 equivalents per pig space per year. So that's that's a typical guideline to go off of, and something that our model showed the same.

Dan Andersen:

Okay. And then, as you looked at those other strategies, for instance, moving to spring, so that we were emptiest in the fall when it was warm, how did that impact? Maybe where our methane emissions ended up.

Jake Willsea:

So shifting to a spring just about cut it in half. So we had about a 50% reduction in our methane production just from changing the time when that manure gets the fullest the manure storage.

Dan Andersen:

And you and I have talked about this quite a bit, and a lot of that's predicated on what temperature you think the manure in the storage is going to be. And that's one area that we don't have a lot of data, unfortunately, in manure temperatures of a deep pit. It's something that people have studied a little bit more frequently, not a lot, but a little bit more frequently in out of barn manure storages.

Jake Willsea:

Yeah, that's that is one of the challenges, especially just getting into the barn and putting a probe down into that manure, it can be a challenge to get permission to do that, and just to have enough boots on the ground.

Dan Andersen:

Especially if you want to go site to site, it's really got to be something that you can deploy and hopefully come back a year later and pick up, or maybe six months later and pick up. Well, manure is a rough place to store things for very long, sometimes on some of those electrical components, but really important for that methane production, and definitely a place that we want to work to improve the model. And I'm on a part of a project right now with Iowa Pork was kind enough to help support where we're going to try and get some better temperature numbers, especially from a deep pit. But okay, so changing season, making sure that basically, the manure storage was only half full going into fall rather than completely full during those warm up months, you got about a 50% reduction. What did side dress do? Going to a side dress instead? Much change or about the same?

Jake Willsea:

Side dress looked very similar. So side dress was again, about a 50% reduction from the fall levels. And that makes sense, because the spring and the side dress applications were about a month and a half apart, so really not much time to make a difference. And especially with the temperature being relatively similar during those times, it didn't make a huge impact.

Dan Andersen:

If we start pushing that side dress back further and further in the growing season, probably makes a bigger difference, as we see some of those warmer weather conditions.

Jake Willsea:

Yeah, if we start to heat up, it like if we were applying in the middle of the summer and that was our time, we might have had a bit of a peak before that application, because we started to heat up while that manure was the full.

Dan Andersen:

Great.

Jake Willsea:

storage was full.

Dan Andersen:

Then the other strategy that you mentioned was just sort of applying more often. So you started with the fall application and said, What would happen if we did fall and spring?

Jake Willsea:

Yep, so we looked at a fall and spring application, a fall side dress, spring side dress, and then a three-way split between fall, spring and side dress. And really what we saw there was again for the fall, spring, split application, we saw again, about a 50% maybe a little more significant than 50% reduction. In terms of fall side dress, we saw again, a little bit of an increase from that fall to spring, just because, again, you're emptying right before it gets the hottest. But our most important, the best results that we could find were the most frequent applications, so the fall, spring and side dress by limiting the amount of manure that you're stored, storing across the entire year. That's really the best way that you can limit your methane emissions.

Dan Andersen:

I grew up on a small little dairy farm, and we put manure on every day, and that really is a condition where you probably don't have much for methane emissions. There's very little storage time. There's not time to build that bacteria inoculum. But it also meant we were out there putting manure on every day in the winter, no matter what weather conditions were like, probably not the best for water quality. So when you start saying, like, yeah, we know this could be a strategy, but there's some limitations to it, especially in northern states, where we might have those snowy winters, frozen ground, and probably shouldn't be doing manure application if we can all avoid it.

Jake Willsea:

Yeah, and there's challenges with water quality there, and also just being able to use that for actual crop production. Here, we're using it for a cash crop of corn, but in those cases, if you're doing a daily application, it'll probably be a sacrificial hay field or something like that.

Dan Andersen:

Absolutely, that's exactly what we had to do, is have a sacrificial hay field for the summer. Now, since you're looking at cash crops, I think that's one of the unique parts of why you were looking at this. You're thinking about a 360 RAIN. And could you just inform us a little bit about that and how it might allow or facilitate this side dress application, cash crop situation?

Jake Willsea:

Yep. So the 360 RAIN is an autonomous irrigation system, and that's made by 360 Yield Center. And the real advantage with this is its ability to go out into the fields during any corn growth phase. So you could go irrigate and apply manure for the entire growing season if you wanted to. It also can apply out of season. So it's another tool for these farmers to use to apply their manure more frequently and keep that storage empty through the summer.

Dan Andersen:

And especially you've talked to me before about this. There's a risk to trying to go to spring application. There's a risk to trying to go to side dress application, and just a tool like that, where we have that high clearance can go over growing corn, mitigate some of that risk to hopefully find good soil conditions and make sure that we can actually achieve that application when otherwise it might get a little lot scary or difficult,

Jake Willsea:

Definitely. And as long as you can get some nitrogen on at the at planting, then you can go in and supplement that later as side dress during the growing season.

Dan Andersen:

Alright, so you had these two approaches, and I'm gonna ask you sort of confidence level in each right? So we said one, we could just try and change the season of when we were putting our manure on, how confident do you feel about your model results there, relative to maybe going to this twice a year? Which one are you more certain on think is a better management practice and just in terms of understanding and making sure we really get that reduction?

Jake Willsea:

I would say the sure bet is multiple applications will definitely cut down on your methane emissions. Now seasonally, you could expect that it would be the same case. Our temperature model, or our temperature aspect of this model is probably has the most uncertainty. Just because of our we weren't able to go out and get real data, so we had to work on on modeling this temperature and especially in a deep pit system where you have fresh manure incoming constantly.

Dan Andersen:

A heated barn above it, right?

Jake Willsea:

There's so many factors that it's a real challenge to model. So if we can get some improved temperature data through, through the research that you're continuing, I think it could be a real improvement to this model.

Dan Andersen:

Yeah, absolutely. And I think the temperature model you were using is sort of based on an out of barn manure storage is what they recommend. And I think if you take some of that and start looking at a dairy farm, different student, Luke Soko, has done some work for me on this of what happens if we apply once a year or twice a year at a dairy farm, sort of at that six months interval, rather than a year of storage, he saw about a 33% reduction in that out of barn storage. So relatively similar using a different model and a different situation use case where we were in the lagoon, so all of a sudden the lagoon says, well, our reduction doesn't look quite as good. And as we think about maybe total carbon reduction, or total reduction in methane, it still might be higher than what you saw in this deep pit case, mostly because it had higher methane to start with.

Jake Willsea:

Yep, exactly.

Dan Andersen:

Alright. And that leads us to our next part. I wanted to talk a little bit about carbon credits and monetization of this. And that gets to be a complicated topic. It seems like it should be easy. I'm just going to look up a market and find one. And there's still emerging markets, right? This is very much at its early stages of what we can do, but we do know that there's some pressures, right? We mentioned those meat processing companies earlier, the dairy processing companies are thinking about carbon neutrality. There's also some carbon standards or carbon registries out there who have played in this space. I'll fully admit that most of them have played in the soil carbon space. But when you look up standards, they have some of them are related to manure, not necessarily related to manure removal frequency as of yet, but as I think some papers get published in that area, and some of this temperature work comes out, there's some potential there. But just thinking forward, assuming we can find a carbon market, and certainly some do exist, we know Nestle is working with National Pork Board on some of their carbon programs, and one of the practices they support is manure removal frequency. I think you looked up some spot prices of what carbon markets might be, roughly 30 a ton for CO2, and started doing some math on what that might mean for some of these scenarios. Could you walk us through, sort of what the potential value structure is there?

Jake Willsea:

Yep. So the value we used was $30 per ton of CO2e abated, and in our case again, starting at about half a ton of CO2 per pig space per year, just from manure alone. If we're able to cut that in half by doing a spring application, that would be come out to about $6.50 per pig or per pig space. So that would be annually if you if you go off of acreage. So we base this off of a 4800 head farm, and if we were able to apply manure to all of those acres on that farm, we wanted to look at this on a per acre basis instead of a per pig space basis. And so while it's about 650 per head, it came out to almost $50 per acre, which is pretty significant improvement, just based on paired to your your crop improvement

Dan Andersen:

Absolutely, because if I start thinking $5 corn, which sounds pretty optimistic these days, that's that's 10 bushels worth of corn that I need to figure out how to get out of that acre, or start working in this carbon credit market, and hopefully taking advantage of that so that is real money, and it can help support some of this cost of maybe buying innovative equipment that otherwise might be hard to justify on your farm, or start thinking about the cost of showing up to apply manure twice, and the extra setup costs and time associated with that. So I agree, I think it's an interesting opportunity, maybe not something everyone's ready to jump on board yet, but it's a it's an opportunity, place for us to think about how we might be able to better manage nitrogen and get rid of some of these methane emissions at the same time. So as we think about that, just to wrap up a little bit about what you're doing, how are you putting all those pieces together that nitrogen management part of it, the methane part of it, how do you think about those in your head and the value proposition?

Jake Willsea:

So there is a challenge, because when you're looking at nitrogen timing, you want to get it on as close to the growing season as you can, so that you have the least opportunity for nitrogen loss in the field. But in the in terms of methane, it's not quite the same. You want to apply that evenly throughout the year and keep your storage as empty and possible, as empty as possible. So we need to find some kind of happy medium between those two, which might be split applications between fall and spring. That way you can have that insurance that you had it on in the fall, but then you can still supplement in the spring, or maybe even more split applications than that, if you can get out or if you have the right equipment for it.

Dan Andersen:

Absolutely, and I think that's really where we're at in science, right? We know what some of the answers would be for if we wanted to minimize this, or if we wanted to minimize that, but the truth is, we're trying to handle 30 to 40 different things, pig growth optimization, making sure my storage has enough capacity, now, methane and nitrogen for my corn crop all at the same time. And that's where the complexities come in, and it makes it really interesting to talk about. So I just wanted to say thank you for coming in today. It's always great to talk with you and learn a little bit more about what you have going on. I know we talk frequently, but it's nice to do it with the microphones running, and sort of get a perspective of what you're working on and how you think it applies to Iowa agriculture. And I always learn a little bit when we do that.

Jake Willsea:

Of course. Thanks for having me. I always love talking crap with you.

Dan Andersen:

Thanks Jake, and thanks everyone for listening. Thank you for joining this installment of Talkin' Crap. Be sure to take a look at the show notes on our website for links and materials mentioned in the episode. For more information, or to get in touch, go to our website, www.extension.iastate.edu/immag/. If you found what you heard today useful or it made you think, we hope you subscribe to the show on your podcast app of choice. Signing off from a job that sometimes smells but never stinks. Keep on talking crap. This material is based upon work supported by the US Department of Agriculture, Natural Resources Conservation Service under a federal award number NR 233A750004G072. USDA is an equal opportunity provider, employer and lender. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect views of the US Department of Agriculture, Natural Resource Conservation Services. In addition, any reference to specific brands or types of products or services does not constitute or imply an endorsement by the US Department of Agriculture for those products or services.