Brandon Gilroye...: There's also a huge greenhouse gas mitigation. So if we think about the dairy manure that we anaerobically digest, all of that methane that would have been admitted to the atmosphere is now not going there. Graeme Li: You're listening to The Why & How Podcast, produced by the Ontario Agricultural College of the University of Guelph, where we look to answer big questions in agriculture, [00:00:30] food, and the environment through casual conversations rooted in research. Hey Jordan, how's it going? Jordan Terpstra: Hey Graeme, I'm doing pretty good today. How about you? Graeme Li: Good. I have a question for you. Do you like kimchi? Jordan Terpstra: I do like kimchi. That seems a little random. Why are you asking me that? Graeme Li: Because we got a whole episode on anaerobic digest, which is how kimchi is made. Jordan Terpstra: Very cool. So who was it that you were talking to about anaerobic digestion? Graeme Li: Yeah, I was talking to Brandon Gilroyed, who's [00:01:00] an associate professor in the School of Environmental Sciences based out of the University of Guelph's Ridgetown Campus. His research is interdisciplinary in focus, so he does a bunch of things, mostly in agriculture, the environment, and renewable energy. But one of his main areas of research is anaerobic digestion, which is what we talked about. Jordan Terpstra: Very cool. Yeah, and so for this episode, Graeme did go solo. So the episode is just you and Brandon. I was unable to join, but I'm looking forward to hearing it on my own [00:01:30] time. And then also just an FYI for our listeners. This is going to be our last episode for a little while. So Graeme and I have done a great job, I think, or kudos to Graeme for being an awesome host for this most recent batch of episodes, but the winter semester is coming to an end, and we'll be transitioning into summer soon. And so we're hoping we'll have a new student host for the summer, and we'll hopefully have a few new batches of episodes coming out soon. But for now this will be the last one. And we'll keep you updated on that. Graeme Li: Yep. [00:02:00] I got to go plant some trees and then return to Guelph in the fall. Jordan Terpstra: Very cool. Well, good luck with a tree planting. And it's been a pleasure recording these episodes with you Graeme, and I look forward to doing it more soon. Graeme Li: Yeah. Made the best out of a global pandemic. Let's jump into the pertinent episode. Brandon, how's it going? Brandon Gilroye...: I'm good. Thank you. Graeme Li: Let's start with the basics. What is anaerobic digestion? Brandon Gilroye...: And so anaerobic digestion is a biological process where we harness the [00:02:30] ability of microbes to break down organic matter, and ultimately they're producing biogas, which is a mixture of methane and carbon dioxide. Graeme Li: So we see that on a small scale, like a brewing beer, for example, right? Brandon Gilroye...: So there's some similarities. I guess the best analogy to it is sort of how a cow's stomach works, so how a cow's rumen works. So a cow eats something, and then they have a bunch of microbes in their rumen [00:03:00] that break it down into energy in forms that they can use and into methane and other gases. Graeme Li: And there's other types of fermentation too. Brandon Gilroye...: Sure. Graeme Li: Like I make kimchi, for example. Brandon Gilroye...: Sure. So there's all kinds of fermentation processes. Anaerobic digestion is, fermentation is part of it. For most other fermentation processes, we're not focused on the gas production. Well, that's not entirely [00:03:30] true. When we're making bread, for example, we want yeast to ferment. Sugar and the carbon dioxide makes the bread rise. When we brew beer, it's also a fermentation process, or wine. So there's a lot of similarities in those processes. But for anaerobic digestion, we're mainly focused on the gas that's produced at the end, so the last step in the process. Graeme Li: And so what is a typical product that you might use in an anaerobic digester? Brandon Gilroye...: Yeah. So [00:04:00] digesters can be fed a whole range of things. So they have to be organic, so organic carbon source, but usual things would be things like livestock manure, food waste, food processing waste, brewery waste. So all those things have carbon, nitrogen, other various nutrients in them, and they can all potentially be used for anaerobic digestion. Graeme Li: And what [00:04:30] does one of these anaerobic digesters look like typically? Brandon Gilroye...: Yeah, so there's a lot of different configurations and styles, but at heart, the one that we have in Ridgetown is a big a tank that's partially buried underground partially above ground, has an inflatable dome on top. And so it looks like a tank with a big round dome on top. And all that's doing is keeping oxygen out. And it's sort of like a little incubator that [00:05:00] we're kind of creating the best conditions for the microbes to do the process. And so it looks like, in our system, there's a single tank. There can be more than one tank. There can be different styles, but that's the most common one in Ontario for sure. It's sort of the style that we have. Graeme Li: And so you're looking to harvest the gasses off the fermentation tank, correct? Brandon Gilroye...: Mm-hmm (affirmative). Graeme Li: And what type of gases are you getting off it? Brandon Gilroye...: So it's mostly methane. [00:05:30] In our system, that's around 70% methane, and then most of the other gas that's left is carbon dioxide. And so in our system, we're taking that gas mixture, and we're burning it in a combined heat and power generator. So we're making electricity using that biogas as the fuel to run the engine. Graeme Li: And do you need to separate the gases beforehand or no? Brandon Gilroye...: No. So for our system, we don't. The only thing that we worry about [00:06:00] is hydrogen sulfide concentration, so H2S, and you have concerns around that because it's corrosive. And so if it goes into an engine, it does damage. And so we have a system in place that also uses microbes. So we inject a little bit of air onto a wooden scaffold that's in the roof of the digester, and that encourages growth of bacteria that consume the H2S [00:06:30] before it gets to the engine. But other than that, we burn it as it comes out. And then the exhaust, which is mostly carbon dioxide is vented to the atmosphere. Graeme Li: Do you have to, let's say, seed these anaerobic digestion, digesters, rather, with microbes every time? Brandon Gilroye...: So in our system, we're feeding dairy manure all the time. And dairy manure is naturally [00:07:00] populated with all the sort of microbes that we want to have, particularly methanogenic microbes are the ones that actually make the methane at the end. And so dairy manure is one of the really nice sort of baseline substrates to use. And so, we have that continuously. For other digesters, if they're not on a farm, for example, they would need to do some sort of, in their startup phase, populate the digester with the [00:07:30] right microbes. But once the system is up and running, you don't have to do that continuously. They'll just regenerate themselves there. So as long as you don't have a system crash, you won't have to regenerate, I guess. Graeme Li: Oh, that's pretty cool. What happens with the products after it has undergone fermentation? Brandon Gilroye...: Yeah. So there's, we call it digestate that comes out the other side. So it's a lot of water and then any solids that weren't broken down, and [00:08:00] there's also some soluble things there. In our case, it goes into a big holding tank, and we apply it as fertilizer on agricultural lands, so on the campus farm and with local producers that are sort of close to where our digester is to minimize shipping and transport costs. Graeme Li: Oh, that's great. Brandon Gilroye...: Yeah. So it's fertilizer. There are higher, I guess, alternative uses for some of that material that's more in the [00:08:30] research phase right now, I would say. So the main use right now is just direct application as fertilizer. Graeme Li: So what are researchers looking into to use fertilizer products? Brandon Gilroye...: Yeah, I mean, there's some systems, this isn't so much research, but some systems also separate the solids out of the digestate, especially if they're feeding a lot of lignocellulosic material. You basically [00:09:00] get some straw and things, things like that out at the end. And then you can use that as animal bedding. There's a lot of tech focused on... So one of the drawbacks of our digestate is it's mostly water, and so that really limits how far you can ship it. And so if you're in a urban center, you're quite a distance from farmland. And so there's a lot of interest in, can we concentrate the nutrients out of the digestate so that you have less material [00:09:30] to ship? So that's a big area of investigation. And then there are also some people looking at, instead of just biogas, looking at, so there are intermediaries in the fermentation process called volatile fatty acids. And so these are the things that are eventually converted into methane, but there's a lot of interest in, can we capture these volatile fatty acids during the process? [00:10:00] Because they can be used for a whole bunch of things. So they're basically platform chemicals that we can use to create polymers, uses in cosmetics industry, food industry. So they're building blocks that we can take and make other things with that, right now, we mostly make those things using fossil fuels. So it's an alternative to that. Graeme Li: So during the entire process of [00:10:30] the fermentation in the digester, approximately how long does it take between putting some manure in and taking it out? Brandon Gilroye...: Yeah, so it really depends what you're feeding. So in our system, we call it the retention time, so how long something on average will be in the digester. Our retention time is usually around 30 days. It can even be shorter because we're mostly feeding material that's easy to break down. [00:11:00] So dairy, manure and fat oil and grease are what we're feeding it. And so those are really carbon-rich substrates that break down fast. If you're feeding something like energy grasses, that retention time, instead of being 30 days, might have to be 60 days or 90 days, or there are even some systems running 120 days. And so that's really slow. It's effective, [00:11:30] but then it becomes a question of economics, and if you can't process material fast enough, can you make the business model work? So that's the other component of it. But technically speaking, we're running in that 20 to 30-day retention time is common for our system. Graeme Li: And does anything happen to the products that you put in, other than anaerobic [00:12:00] digestion from the microbes, like in a mechanical sense? Or is it stirred around? Does anyone need to get in there, all in the poo? Brandon Gilroye...: In our system, there are a couple of things. So the material that we take from off the farm has to be pasteurized before it goes in. And so it comes into a holding tank, and then we pasteurize it at 70 degrees for one hour, and then it goes into the system. The system itself is mixed. So it's a continuously [00:12:30] stirred tank system. And so there are three, basically big impellers inside the system that turn on periodically to make sure that it's always mixing. And so in our system, our solid content is very low. So our system is usually 97% water, and so it mixes very easily. Graeme Li: Nice. And so you're researching cow manure, correct? Brandon Gilroye...: That's part of it. Yeah. Graeme Li: And what, in particular, are you looking at? Brandon Gilroye...: [00:13:00] On the research side of things, we look more at other substrates, so not the conventional things. So we've done a lot of work looking at other biomass sources, so some of the biomass crops that are not broadly adopted yet, looking at how well they degrade, how much methane we can get from them. We also have done quite a bit of research looking at pretreatment technologies. [00:13:30] So I mentioned with energy grasses, you have to have this really long retention time, and that can basically make the business case hard to hold together. And so there's a lot of interest in pretreatment technologies that will partially break down those materials before they go on the digester to speed up the process. So we've looked at biological things there, so things like enzymatic pretreatments, other microbial [00:14:00] pretreatments, thermal pretreatment, chemical pretreatment, so anything that can sort of break up or loosen the lignocellulosic structure will help speed up the anaerobic digestion process. Graeme Li: So what are some examples of these energy grasses? Brandon Gilroye...: So energy grasses can be things like Miscanthus. We've looked at Arundo donax, which looks a bit like bamboo, so it's a very tall perennial [00:14:30] grass, switchgrass, cup plant, so plants that are things that are grown in Ontario. A lot of the biomass crops don't have a really good end market yet, and so anaerobic digestion potentially could be one thing to sort of help on that side as well. Graeme Li: I'm in agriculture, and I've only ever heard of switchgrass from that list. Brandon Gilroye...: Yeah. Yeah. I mean, they're not commonly grown, right? Especially [00:15:00] we're located down in Southwest Ontario, which is a really high value farmland, so farmers are growing corn, soybeans, wheat, the sort of usual. But there's a whole range of reasons that some of those crops might make sense in marginal lands or lands that are under-utilized right now or things that aren't suitable for food production that could be used for bioenergy production. Graeme Li: [00:15:30] And we've touched on lignocellulosic digestion briefly a couple of times now. Could you delve into what that is exactly? Brandon Gilroye...: Yeah. So lignocellulose is talking about the structure of the plant material that's going in. So any sort of plant-based biomass has lignocellulose. And so that is what gives plants their structure. [00:16:00] And so if you think of something like wood from a tree, there's a lot of lignin in that material, and lignin is sort of what holds it all together. In anaerobic conditions, lignin doesn't get broken down, so there aren't any microbes that we have in the anaerobic digester that can do anything with lignin. And so if it's in there sort of like glue, holding everything else together, the microbes can't break down [00:16:30] the material so that they're limited in what they can do. So that lignocellulose is really talking about three things broadly combined, so cellulose, which is just a polymer of glucose. Microbes can break that down really well and convert it into biogas. So we want them to have access to that. There's also hemicellulose, which is, again, a polymer of sugar. So it's just a chain of different sugars and microbes can utilize that and make biogas from it. [00:17:00] And then there's the lignin portion, which they can't do anything with. So there's interest in lignin as a, that also can be a product used for making things like biocrude, so biological crude oil. But that's sort of a different process, I guess. It's something that could be coupled with anaerobic digestion, but I'm not an expert in that area. Graeme Li: Oh, okay. Brandon Gilroye...: But when it comes to [00:17:30] breaking down the lignocellulose, that's the big bottleneck is just the structural rigidity of the material, which makes sense. If a tree falls down in the forest it doesn't degrade and disappear overnight, right? It takes a long time for it to break down. It's meant to be resistant. It's meant to persist. And so if we're thinking about an anaerobic digester where we need a retention time, that's measured in weeks or months [00:18:00] at most, we have to provide some sort of help to get that to break down in the timeframe that is practical for us. Graeme Li: And I remember hearing a while back that, I'm not sure if it was lignocellulosics digestion or just cellulosic, that for ethanol production was supposed to become a big thing, but it never really did. Could you touch on that? Brandon Gilroye...: Yeah. So, I mean, the challenge for ethanol production is that [00:18:30] you're making ethanol with yeast. And so yeast are really good at fermenting sugar that's freely available, but yeast are not designed to, they don't have enzymes to degrade cellulose or lignocellulose. And so even though that a lot of that material is sugar, if it was all chopped up into little pieces, they can't get access to it because they don't have the enzymes. And so for [00:19:00] ethanol producers, sort of the holy grail is to have yeast that, either yeast that can do those jobs, so genetically engineer the yeast so that it can chop up and use those more complex substrates, or to have upstream processes where you enzymatically treat the material to chop it up into sugars that they can ferment, and then they could go ahead and do [00:19:30] it. So there are, I mean, there are commercially-scaled lignocellulosic plants. It's not a question of, can you make it work? It's a question of, can you make it work economically? So there are processes that we can do. We know we can turn wood into ethanol, but it has to be economically competitive, and it just isn't yet. Graeme Li: And so that's a lot [00:20:00] of what your work focuses on, making that proof of concept and making sure that it can be done economically. Brandon Gilroye...: Yeah, I mean, the advantage that we have, I guess, in that we run a digester is that we're pretty able, we're quickly able to sort out what are sort of nice academic ideas and what are... Some of those ideas might not be feasible in a five-year horizon or a 10-year horizon. And so we try and focus on things that [00:20:30] could be doable right away. And because we're running a system and trying to make a business of it, we have a pretty good grasp on, if we do this, yeah it works, but how do you make money doing it or break even doing it? And so that's a big challenge. It's probably one of the biggest drivers of sort of challenges [00:21:00] to adoption of the technology is the market conditions and the business model. It's not so much the technology side. The technology's there. It's getting the right incentives in place for it to take off. Graeme Li: Yeah. Do you have any idea how many digesters there are approximately on farms in Canada or in Ontario? Brandon Gilroye...: Yeah. I mean, in Ontario, it's 35 or 40. [00:21:30] In Canada, it's a bit more, 50, 50 or 60, if you contrast that to like Germany where they have 13,000 digesters. Graeme Li: Wow. Brandon Gilroye...: So Canada and the United States has not seen big uptick so far. Certainly compared to Western Europe, we lag a lot in adoption. And that's, I mean, basically all [00:22:00] down to the funding models and the incentives. Graeme Li: Hmm. Like in Germany, where there are subsidies and whatnot or? Brandon Gilroye...: Yeah. So, we shouldn't say that there haven't been subsidies in Canada, but we haven't been as aggressive or consistent with them. And so in Germany, certainly they've had generous subsidies in place for a long time to establish the industry. They also have, [00:22:30] the energy pressures in Europe are different than the energy pressures in Canada, which is a major oil and gas producer and exporter. And the same for the United States, so that's also part of it. I think there's a societal acceptance of renewable energy and anaerobic digestion in Europe that we're not there yet in North America, partly because of education, partly because of economics. Graeme Li: [00:23:00] Because it really does seem like our a win-win-win kind of situation where you're getting quality fertilizer coming out, you're getting renewable energy. Brandon Gilroye...: Yeah. Graeme Li: But I suppose that cost at the start, you just need to overcome that? Brandon Gilroye...: Yeah. Well, and there's also huge greenhouse gas mitigation. So if we think about the dairy manure that we anaerobically digest, all of that methane that would have been admitted to the atmospheres is now not [00:23:30] going there, right? So that methane is now being captured and burned for electricity. So we're offsetting fossil fuel electrical production. We're offsetting greenhouse gas emissions from the dairy itself. If we're taking organic waste that normally would go to a landfill, you're offsetting emissions there as well. So there's a huge number of environmental [00:24:00] benefits, but none of those things are, there's no cost attached to those benefits right now. So we don't have a carbon credit system, for example, in Canada yet. And so if you're a dairy producer or any kind of livestock producer, having a digester has immediate environmental benefits, but you're not being economically incentivized in any way to do that. Graeme Li: With exception [00:24:30] of the small amount of, or the amount of electricity being produced, eh? Brandon Gilroye...: Right. And so, I mean, in Ontario, the model was subsidized electrical rates, and so that's what made the business model work. So digesters running in Ontario now work on a combination of their feed-in tariff contracts that they had with the province, so to produce and sell electricity, and [00:25:00] they accept tipping fees for taking off-farm waste. So it's like a processing fee for that. And that's the business model. And that model doesn't exist anymore because we don't have feed-in tariff electrical contracts anymore. Those have been phased out with the change in government from liberal to conservative. So there's a lot of interest in adopting the [00:25:30] technology, but right now you can't sell the electricity. And so there's no real incentive to look there. There's a big push to, so we talked about making biogas, which is a mix of methane and CO2. And then we can burn that and make electricity, but we can also do what's called upgrading the biogas. And so there we're stripping out [00:26:00] the CO2 and any other impurities to get methane that is on par with natural gas. And so once it's on par with natural gas, we call it renewable natural gas, and it can be used any way that we use natural gas. So there's a lot of interest now in looking at, okay, can we put in anaerobic digesters, have them upgrade the gas? And then the gas goes into the existing natural gas grid, [00:26:30] and then it can be distributed anywhere in North America basically. Or it could be put into liquid form and used that way. So there's a lot of interest in that. And again, it will come down to what is the pricing being offered by the gas utility companies for renewable natural gas? Graeme Li: And just out of interest, what does one of these anaerobic digesters cost? Brandon Gilroye...: Yeah, [00:27:00] I mean, it's a huge range depending on, I mean, every site is different, and the sizing is different. So there's one on-farm system in Ontario that's quite small. I don't know the exact price, but at minimum I would say you're in the sort of 4 or $500,000, and most systems are multimillion-dollar systems. So it's [00:27:30] very easy to spend $5 million on a small on-farm system, which is an enormous capital investment, right? Unless you're a very big farm, it's a lot to bite off. And so that's a big challenge. Graeme Li: Yeah. That's a big chunk of change. Brandon Gilroye...: Yeah. Yeah. So there's a lot of interest in what do the market conditions have to be to make a smaller farm, like make it attractive for smaller farms? [00:28:00] And so we are doing some work, looking at that and trying to figure out, how could you make this work for a dairy that has 50 cows? Because if it only works for dairies that have a thousand cows, well, that's fine in the United States, but that's not the Canadian model for dairy production. Graeme Li: And are these anaerobic digesters producing a hydrogen? Because these days in the news, we do see a lot of talk about green hydrogen [00:28:30] production for cars and new fuel types. Brandon Gilroye...: Yeah. So digesters, the way they're set up, don't produce hydrogen. So the goal was to have all the hydrogen be consumed and converted to methane. So they produce hydrogen, but it's only as an intermediate product. There is interest. There's been a lot of research on producing green hydrogen through fermentation. So all of our fermentation is done in a single tank, but if you split [00:29:00] it into two systems, so one system that works on a very short retention time, you can get hydrogen production in that system that you could take off and use. That's not really economical. So far at least, it hasn't worked. But one of the interesting things where hydrogen could sync in well, I think, with anaerobic digestion is there's this idea of it's called power-to-gas. And so the idea here is that you're taking [00:29:30] wind energy or Solar energy and using it to electrolyze water, so split water into hydrogen and oxygen. And the hydrogen that is produced, I mean, you could store it and use it as required. But hydrogen has some challenges with storing and transportation, and it's really explosive. And so an alternative use to that is actually to convert it to methane. And so you can do that by running the hydrogen back through an anaerobic [00:30:00] digester. There are microbes in there that will take it and make it into methane. But there are also a couple of commercial systems where they specifically have a microbe of choice, a methanogen of choice that takes oxygen, takes hydrogen, and you're making your methane. So that's a methanation process. And so the advantage of that is [00:30:30] where you're using CO2, so you're capturing that, and it's basically a way to capture wind and solar energy. So the wind doesn't always blow, the sun doesn't always shine, and so you can either have a battery-type system where you're storing the energy as it comes in, or you can do this sort of approach where you're using the electricity that you're making, splitting the water, and that hydrogen that you're producing is now being converted to methane. And that's your [00:31:00] carrier molecule, so that's how you're moving the energy around. The advantage to that going to renewable natural gas is that you can use renewable natural gas in a lot of ways, right? So in Canada, the majority of homes are heated with natural gas, but you can also use it as a transport fuel. And so there's a big push internationally to electrify everything. You hear lots of talk about electric cars. [00:31:30] Tesla's stock is through the roof. So there's a lot of interest in electrification, but Tesla doesn't make tractors. They don't make semi trucks. And so in that heavy transport sector, there's probably going to be a long-term need for liquid biofuels. And so renewable natural gas could be a part of that, could be a big part of it. Yeah, potentially. And so that's, yeah, like hydrogen [00:32:00] is an intermediate in this process, and it also can be a way to link other processes to anaerobic digestion. And so one of the cool things about anaerobic digestion is that it can be sort of like a hub technology that just connects other things that otherwise wouldn't be connected. And that's a very good sort of baseline platform for a bio-refinery. So you put something in, and you get a range of products out at the end, [00:32:30] and it's adaptable to what you need at the time or what's most economically favorable at the time. Graeme Li: That's awesome. So just wrapping up here, are you looking forward to anything in particular with your research? Brandon Gilroye...: That's a tricky question because we're waiting to see what projects will be funded. One of the areas, I guess, that we're starting to look into is, [00:33:00] so there's a big push to move to stop putting organic material into landfills. So we want to get all that stuff out of landfills. And so the only other place for it to go basically is to compost facilities and anaerobic digesters. And so one of the challenges that that material poses is that it's always contaminated with plastics, and some of them are biodegradable and some of them not. And so we don't really have a good handle on what happens [00:33:30] to, for example, compostable plastics in anaerobic digestion systems. And so those materials are designed to break down under industrial composting conditions, which are aerobic, so there's oxygen and higher temperature than we normally run a digester at. So yeah, trying to figure out what happens to those materials, if they go into our digester, or is there something we can do to them upstream of the digester to make them break down? [00:34:00] Or if they're coming out in the digestate, are we putting microplastics onto agricultural land? Is there a ramification for that? So there's a lot of, there's this big idea that's really good, stop putting organic waste into landfills, but we kind of have to figure out how, when it doesn't go to the landfill, where does it go next, and how does it alter how those systems are operated? Or what do we need to do differently? [00:34:30] So that's an area we're starting to work in more, more and more because it is a pressing question. Graeme Li: Yeah. That's an exciting topic of research and fingers crossed for all the good funding to come your way. Brandon Gilroye...: Yeah. It's always interesting to see what gets funded and what doesn't. Yeah. Graeme Li: Yeah. So I'd like to thank you for being with us today and presenting us your research. [00:35:00] Are there any shout-outs you'd like to give? Brandon Gilroye...: Yeah, well, I mean, of course our research team, especially Kim VanOverloop and Lucas McNea, who are our facility operators. They run our digester in Ridgetown. And the big one for us for funding has been OMAFRA. So the OMAFRA, Agri-Food Innovation Alliance has been very good to our program, and Canadian, the Livestock sector has been very good to us, the Egg Farmers of Canada, [00:35:30] Ontario Pork, Beef Cattle Research Council. Graeme Li: Awesome. Well, thank you so much for being here, and thank you everyone for listening. Bye now. Brandon Gilroye...: Thank you. Graeme Li: The Why & How Podcast is published by the Ontario Agricultural College of the University of Guelph. It is produced by Stephanie Craig and Jordan Terpstra. Recorded and edited by Jakub Hyzyk and Kyle Ritchie. The host is me, Graeme Li. If you liked what you heard, be sure to leave us a review and subscribe. Thanks for listening.