Why Biochar is Important & How it Can Be Used in the Landscape

Dr. Chris Fields-Johnson, technical advisor with the Davey Institute, talks about the many uses and benefits of biochar and how it can be used in the landscape. 

In this episode we cover:  

• What is biochar? (0:40)
• What does biochar do to the soil? (1:35)
• What does biochar look like? (3:57)
• How is biochar made? (5:11)
• How would biochar be used in tree plantings? (6:37)
• Is biochar a new product? (8:51)
• How is biochar packaged? (11:25)
• How would a home gardener use it? (12:06)
• Chris' background with biochar (13:43)
• The many positives of biochar (17:59)

To see what biochar looks like and how it can be used, watch our YouTube video, How to Improve Soil Health with Biochar.

To hear Chris talk more about soil care with biochar, watch our YouTube video, Davey SoilCare®: How to Improve Soil Health with Biochar.

To learn about ways Davey Tree is creating and using biochar, read our press release, Davey Makes Strides Towards Greater Sustainability with New Biochar Facility.

To find your local Davey office, check out our find a local office page to search by zip code.  

Connect with Davey Tree on social media:
Twitter: @DaveyTree
Facebook: @DaveyTree
Instagram: @daveytree
YouTube: The Davey Tree Expert Company
LinkedIn: The Davey Tree Expert Company 

Connect with Doug Oster at www.dougoster.com. 

Have topics you'd like us to cover on the podcast? Email us at podcasts@davey.com. We want to hear from you! 

Transcript

Doug Oster: Welcome to the Davey Tree Expert Company's podcast, Talking Trees. I'm your host, Doug Oster. Each week, our expert arborists share advice on seasonal tree care, how to make your trees thrive, arborists' favorite trees, and much, much more. Tune in every Thursday to learn more because here at the Talking Trees podcast, we know trees are the answer. I'm very happy to welcome Dr. Chris Fields-Johnson. He's a technical advisor for the Davey Institute, part of the Davey Tree Expert Company. I have waited for a long time, Chris, to talk about this topic, all about biochar. Welcome to the show.

Chris Fields-Johnson: Thank you, Doug. Wonderful to be on today.

Doug: I've been hearing about biochar for a long time now. Sometimes people will just give me a bag of it. I've talked to arborists and we've skirted around the edges of it. What is biochar? That's the first question.

Chris: Biochar is black gold. If they gave you some freebies, you should hang onto it and make good use of it. Biochar is essentially charcoal that we add to soil to achieve some benefit. Charcoal is just made from biomass, so it's partially combusted with low oxygen so that it does not burn all the way down to ash. You're left with the char or the carbon skeletons of that biomass. That's what charcoal is. Usually, we'd use that for grilling, or heating, or making steel and stuff like that. When we add that to soil deliberately to achieve benefits, we call it biochar.

Doug: In what situation is it used in soil? What does it do?

Chris: It has a lot of interesting benefits. One thing that it's really good at is it's stable. It doesn't decompose. Once it's in the ground, it's going to be there for hundreds or thousands of years, maybe longer. One of the number one purposes would be for carbon sequestration. All that carbon dioxide that was harvested by plants years ago and accumulated in the plant in the form of cellulose and lignin, all that has been stabilized during the carbonization process.

When we put it in the ground where it's protected from fire and decomposition, it's going to last there for a long time. It is a really good method of carbon sequestration. Then once it's in the soil, it has a lot of other side benefits. One property is that it's really hard to compress it, compact it, and cement it together. If you get enough of it into the soil, it's going to give the soil a lot of resilience against compaction. It'll maintain porosity and structure, even if it's heavily trafficked, which is great for the urban and built environments that we work in where soil compaction is just a ubiquitous problem for turf, trees, shrubs, all kinds of plant material.

Another big thing that it does is it is going to retain nutrients. It's going to help with nutrient use efficiency and thereby reduce pollution that would otherwise leach out or run off of soil and pollute waterways particularly. Biochar has lots of ion exchange capacity, lots of surface area that helps nutrients be retained until they're actually used by microbes and plant material. It's going to help with nutrient use efficiency as well.

Then microbes also like to use it as habitat, all that porosity and surface area. Think of it as like a condominium or apartment complex for microbes, fungi, bacteria. They're going to take up shop and use all that surface area and do all the good things that they do, protecting plants from pathogens, releasing mineral nutrition from soils, making it available to plants. All those benefits of microbes will be amplified.

Doug: What does it look like? Are we talking about big chunks of like charcoal or is like powdered charcoal? Yes, give me an example.

Chris: Biochars that we use in the landscape are generally going to be smaller in particle size than lump charcoal. Although chemically it's similar to a lump charcoal where you have big chunks or chips of wood that you might use in your grill to flavor your meat or your portobello mushrooms or whatever you're grilling up, this is going to be a smaller material. It's going to be ground down and run through some sieves or screens to get it down to a smaller size. That's going to help it to mix better with the soil and be easier to apply.

Then it comes in different size classes. Stuff that's really powdery and small, you can even mix with water, suspend it in water with agitation and inject it into the soil with water under pressure. Then larger stuff you would mix in by hand or with air tools. Then the really larger chip size stuff, we can use for making vertical mulch holes and French drains because it really promotes drainage and aeration to greater depths.

Doug: Is there a special way that it's made? Is it just burning wood or does it have to go through some special process?

Chris: Yes, biochar goes through a special process that we call pyrolysis. That's partial combustion. At some point during combustion, you have to cut off the oxygen supply. Otherwise, the biomass is going to burn down until it's just ash. If you have a wood stove, for instance, if you just let that burn all the way, you're going to end up with ashes that you have to eventually clean out and get your stove going again with new wood.

Imagine damping the wood stove down after it stops flaming. You've got that first stage of combustion where there's lots of bright flame. Well, that's all the volatile components in the wood that are evaporating from the wood as it heats. They're igniting in the air when they're exposed to oxygen. That's what you see as flame. Then you move to the secondary stage of combustion in a wood stove, or a fireplace, or a campfire outside where just the coals are burning. There's no more open flame because all the volatile component has been burned off. Now you just have glowing coals and they'll burn without producing flame or smoke.

The idea is that if you can shut off combustion in that secondary phase, you'll retain all of the charcoal. If we refine that down and apply it to the ground, that's a good biochar.

Doug: Give me some examples. Let's start with tree planting. How typically biochar would be used in a planting situation?

Chris: We would look for situations that have low organic matter and high levels of soil compaction, where if you were to just stick a tree and without any kind of site preparation, it would have a lower chance of survival. Even if it survived, it would probably perform poorly. It would be stressed out, susceptible to all manner of disorders, diseases, pests because of that stress condition. We're going to look for trees that are going to be growing in those kinds of environments, low organic matter, high levels of compaction, poor soil structure. That's a great target to apply biochar to the soil because it's going to build up porosity and structure and alleviate a lot of those compaction issues.

It is a stable form of organic matter, but because of that, it doesn't decompose readily. That means microbes can't really use it as a source of carbon or energy. When we apply it for site prep, we're always going to put it down with compost. We're going to put the two down together. We've got the stable carbon is coming from the biochar. The labile or mobile usable carbon is coming from the compost. The compost will break down. Microbes can use it as a carbon and an energy source. Then the compost also releases nutrients, nitrogen, phosphorus, potassium as it breaks down, which will feed the microbes, and in turn, feed the plants.

That's a typical scenario for site prep is that we would find an area with high compaction, low organic matter, we would mix in lots of biochar and compost with that soil that's coming out of the ground on the site, and prepare a good planting soil in situ as it lies on the site. Then you could plant your trees into that. Maybe you treat the whole site. Maybe you treat the immediate area around where the trees are going to be planted, but that's how that would work.

Doug: Is biochar something new or it's something you've known about for a long time?

Chris: I've been aware of and working with biochar since about 2008. For me, it's a little bit old hat, but going back much further than that, this is a technology that goes back to traditional land management of indigenous peoples going back thousands, maybe tens of thousands of years. Some of the original biochar research stemmed out of archaeological finds in the Amazon basin, the terra preta soils, the dark earth soils of the Amazon basin.

Indigenous peoples there were making charcoal by burning up forest debris and household waste and applying that to the ground. That was discovered by archaeologists and soil scientists, and they did some reverse-engineering and they realized that charcoal was one of the primary constituents, one of the primary ingredients of the terra preta soils. A lot of what we're doing today, we're just trying to reverse engineer and replicate what they were doing. Beyond that, dark earth sites have been found in central Germany, in Asia, China, and Japan. They would carbonize rice hulls, mix them with human waste, and use that to renew agricultural soils. Also, the prairie states of the United States and the prairie provinces of Canada. One of the reasons they have such fertile soils is because of the prairie fires that would be lit off by indigenous peoples every autumn or winter. A lot of them were also started by dry lightning strikes, where you get lightning striking during a dry thunderstorm where it doesn't rain. That's a pretty frequent because of prairie fires as well.

When all that dry grass burns, it never quite burns all the way. Instead of burning all the way to ash, there's a lot of carbon residue that's left behind. You can imagine if that happens every year for 10,000 years, you're going to have a lot of charcoal residue building up in the prairie soils. It worked in to depth through the leaching of rainwater and detritivores-- insects and earthworms, things like that, that mix the charcoal and other organic debris down into the soil. A lot of our really rich prairie soils are heavily influenced by charcoal as well.

Yes, so this isn't really anything new. It's an indigenous practice. It's something that happens naturally in some cases. We're largely just trying to re-engineer it, reverse-engineer it, and figure out how we can use this idea today.

Doug: How is it shipped? In big bags or pallets? How does a big company like Davey get it?

Chris: Several different ways. It can be shipped in bulk. You can just put it into a large dump truck or a dump trailer or a walking floor trailer, so it can be shipped in bulk. More frequently, it'll be shipped in cubic yard or two cubic yard super sacks or cubic foot-sized bags. The same bags you'd get compost and mulch in at the hardware store or the garden center. Those are the most frequent ways that it would be transported.

Doug: I have a bag of it, again, that someone gave me maybe three years ago. I don't really know what to do with it. From what you're saying, this is something that I'm not going to have to worry about it expiring or anything. This is something that's going to stay as biochar for a long time. For a home gardener like me, how would I use it?

Chris: Yes, you're right. If it's just biochar in the bag, that's extremely stable. You can leave it in the bag for years or decades back in your garage or your shed and take it out years later and use it. It'll probably be [unintelligible 00:12:41] the same as when you put it in there. Now, if it's mixed with compost or some other ingredients that do decompose, then it will change over time, the whole contents of the bag, but pure biochar is very stable.

How would you use it in your garden? Just like we do with site prep for trees, focus on areas that have compaction problems or low organic matter. You would blend it into the soil with compost. A typical recommendation would be trying to get 5% to 10% biochar by volume in your soil. Then at least that much compost as well, 5% to 10% compost by volume. If you can apply both of those in those amounts, you should be able to turn your soil into something that functions like a really nice topsoil. It'll be good for the growth of vegetables or wildflowers or trees and shrubs, whatever you're trying to plant.

Doug: Oh, this is exciting. I can finally use that bag of biochar somebody gave me now that I've been schooled on it. Tell me a little bit about your background and how you made your way to Davey.

Chris: I started at Virginia Tech in the forestry department. My undergraduate degree is in traditional forestry, and I began reading about and doing biochar practices during my undergraduate years at Virginia Tech. I stayed on at Virginia Tech for graduate school in crop and soil environmental sciences. I worked for a few years on my master's in the field of land reclamation, reforesting mine sites in the Southern Appalachians that had been mined for coal. This is like mountaintop removal mining, contour mining, strip mining, things like that. How do you get native forests to regrow on sites like that? Those are the problems I worked with for my master's.

In the background, I was still learning about and practicing biochar techniques on my own. I turned that into a PhD project, again at Virginia Tech, working specifically with biochar, starting with land reclamation, looking at if biochar can help tree seedlings establish and mine soil. Mine soil really isn't soil. It's just rock fragments that have been blown up when they're removing the overburden to get at the coal. It's a fresh material. It benefits a lot from having the biochar added in there, as I found, improving its water holding capacity and performance of plants and that thing.

I continued on that thread, did some other projects during my PhD years, worked with blending biochar with municipal biosolids. They're very much complementary. The biochar, for one, reduces the smell of that sewage sludge, which is important to a lot of people, but it also reduces the water content. Sewage sludge, biosolids tends to be fairly wet. The biochars tends to be dry, so it soaks up some of that water, makes it more usable. It has a lot of benefits for the pollution profile of biosolids as well. It's going to help prevent leaching of things like nitrate and orthophosphate. It also helps reduce the emissions of greenhouse gases from manures and biosolids as they decompose. It has lots of co-benefits with those kinds of materials.

Then finally, the last bit of my PhD project was working with controlled burning. I did a series of 10 controlled burns in a loblolly pine plantation. I was searching for the right conditions to maximize the amount of charcoal residue left on the surface. What type of burn, like back burning versus head firing, and what fuel moisture conditions and relative humidity conditions and wind speeds, things like that, would lead to more carbon accumulation on the surface by getting the pine litter, the pine needles that are accumulated on the forest floor, to burn in just the right way, so they left lots of carbon behind instead of burning all the way to ash or not burning at all. I was looking for the right set of conditions to maximize that.

I found that under the right conditions, you could get over a ton per acre of biochar accumulated every time you burn. You could probably burn every three years or so. You have to let the litter accumulate for a few years. Then you could burn again under the right conditions and get another ton of biochar per acre. You could continue that practice for decades or hundreds of years. You could end up with a lot of carbon stored in the soil and a much better topsoil. I worked on that for my PhD. While I was finishing that up, I worked as a plant health care technician. Then eventually, I came on to Davey as a technical advisor, which is what I do now. I brought all the biochar stuff with me.

Since I started at Davey, I've run numerous workshops on the use of biochar for urban soils, for arboriculture, using it with air tools and compost and top dressing and vertical mulching. We've played the liquid injection technology as well. I brought that with me into the company and integrated it into our soil services.

Doug: It seems like such an amazing positive for what you're doing with the biochar. Is there that feeling? I know that this, for you, there's a ton of science in here, but there's got to be some good feeling about these positive aspects of biochar and making it available and teaching people about it.

Chris: Yes, it's been a lot of fun and it has led to a lot of positivity and hope. Because here we have a way to address a lot of the primary concerns with urban soils, while also sequestering large amounts of carbon. We can take what is a waste product for us, like wood chips and wood debris, which would normally be just landfilled or ground up into mulch and then just decompose on the surface. We can take that material, we can turn it into a stable form of carbon and store it in the soil for the long term. Now we can be a major player with combating climate change.

Then beyond that, with all the stuff it does with nutrient retention and nutrient use efficiency, we can also use it as a tool to clean up waterways. We have these perennial issues in places like Lake Erie, the Chesapeake Bay, Lake Okeechobee, where you get the algae blooms and the fish kills and the anoxic waters and all that. Well, if we can use biochar to reduce the amount of nutrient runoff and leaching into waterways, we can begin to solve some of those problems as well.

Yes, so I'm very hopeful about it and very optimistic. I think it's an exciting technology. Again, not something new. It's something that we're reverse-engineering and reinventing, but I think it can make a big difference for us.

Doug: I'm going to leave it right there. That is great stuff, Chris. I am so happy to finally understand biochar and I'm looking forward to using it in my own property. I'm sure lots of other people listening that are going to figure out a way to use it in theirs. Thanks so much for your time and I can't wait to talk again, another interesting topic, I'm sure, soon.

Chris: Thank you, Doug. It's been my pleasure to talk about biochar with you today.

Doug: Tune in every Thursday to the Talking Trees podcast from the Davey Tree Expert Company. I am your host, Doug Oster. Next week, we are going to have some fun as Lou Meyer returns to talk about managing nature. You'll find out what that's all about. Do me a favor, subscribe to the podcast so you'll never miss a show. If you've got an idea for an episode or maybe a comment, send us an email to podcasts@davey.com. That's P-O-D-C-A-S-T-S at D-A-V-E-Y dot com. As always, we like to remind you on the Talking Trees podcast, trees are the answer.

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