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Biochar: Everything Old is New Again

“I hate to even suggest this... But I think we wanna consolidate these two brush piles.” My poor coworkers. They've joined me for a day of wintry savanna restoration work at the Motor Mill Historic Site. Slowly but surely, we've been reclaiming the hillside on the south unit for several years, and one of the last big hurdles (on this section, anyway) involves dropping and bucking a few very large cedar trees. And big cedars are almost as bad to deal with on the ground as they are actively growing – at least to our feeble human arms. Especially when you have to move them twice because I'm being picky. Cedar trees stymie a savanna restoration by sucking tremendous amounts of water from the soil – some estimates say a large cedar can drink more than 30 gallons per day with adequate soil moisture – while likewise hoarding sunlight from above. The branches of these open-grown cedars, some 30 feet tall or more, adorn the trunk all the way down to ground level, and spread some 15 feet across.

Cedars marked for deletion from the Motor Mill south savanna

Having recently seeded the area with native grasses and wildflowers, these cedars need to go in order to create the optimum sunlight and soil moisture conditions. Stacked into towering brush piles, these cedars will create fantastic habitat for all manner of birds, rodents, and rabbits seeking shelter from the harshest of winter weather. But getting the trees into piles is no small feat. It's physically challenging, and strategically locating the piles so that we're not just turning one modest shade structure into several smaller but denser ones has it's own logistical challenges too. As a result, I can't help but feel wasteful, or even destructive. I recognize the wildlife habitat value of the piles, and the need to create this “waste” in the name of more oak trees and wildflowers for the future of this stand. In short, I recognize the value of the work and the need for more of it. But as a conservationist, I can't shake the parallel thought that there must be a better use for all of this wood, even if it's not suitable for traditional wood products like lumber or even firewood. Having generated quite a few brush piles in the last few years – or scattering “coarse woody debris," as it's technically called – my curiosity got the better of me and I started googling, as one does, for solutions. Pretty soon I'd fallen down the rabbit hole of “alternative forest products,” a catch-all term for materials like cross-laminated timber, wood chips, pine straw, and biochar.


The last one really caught my attention. Biochar is one of those things that, like Roman concrete or Damascus steel, played a huge role in the ancient world but somehow became lost to the collective consciousness. Indeed, the archaeological record suggests humans have used biochar for thousands of years to improve the agricultural capacity of their local soils. Thick layers of biochar-enriched "terra preta" separate the good soils in the Amazon from the less-fertile "terra mulata" nearby, and the preponderance of pottery shards and animal bones suggest the terra preta has human origins.

Comparison of enriched vs nonenriched soils in the Amazon

But unlike Damascus steel and Roman concrete, we never actually stopped making biochar. We just forgot how to use it. In fact, we make it pretty much anytime we have a campfire. Biochar essentially comes from organic material that's been burned (“pyrolized,” actually), but not turned completely to ash thanks to a lack of oxygen and carefully-timed extinguishing. Those black pieces of used-to-be-a-log from the interior of your campfire left over after you extinguished it?

Who knew it'd be good for something? Most indigenous cultures, apparently.

That's biochar, and it has some remarkable physical and chemical properties. First and foremost, it has tremendous porosity, AKA lots of little tiny holes. Those holes give it much more surface area. That surface area, in turn, makes it behave a little like a sponge, holding water, sometimes as much as 3-5 times it's weight. Chemically, it has a distinct capacity to attract and adsorb nutrients and minerals. Adsorption differs from absorption, and the difference matters here. Absorption refers to chemically incorporating atoms or molecules, while ADsorption means merely bonding them to a surface. Adsorbing nutrients, in the case of biochar, means they basically just cling to the char, keeping it available for absorption by any microbes, fungi, or roots who may find their way onto that same surface.

Microbial filaments colonizing biochar

Incorporated into soil or placed in water, biochar adsorbs nutrients like nitrogen and phosphorous that would otherwise pass through with the groundwater. Fungi and microbes – the foundations of soil health – then can make more use of the nutritious material, metabolizing it and converting it to richly organic top soil. It also intercepts heavy metals. If you've kept up so far, kudos, and you might be thinking what I'm thinking. We have a major invasive species problem in our woodlands, and a distinct need for more active forest management (which generates lots of coarse woody debris) to restore savannas and promote oak regeneration, as I've outlined in this blog a number of times. The trouble is, many land stewards don't have the time or money to carry out this active management unless it gives them something in return - like increased timber or wildlife value.

Woodland understory dominated by invasive honeysuckle shrubs

Meanwhile, our waterways have well-documented issues. Nitrates and phosphorous from fertilizer runoff, sedimentation from excess rainfall, and heavy metals from industrial activities all present hazards to everything in the water, from the tiniest invertebrates to recreating humans.

Biochar filters capturing pollutants from a stream

So what if there was a way to tackle both problems at once, and maybe one more? Did I mention biochar also has the potential to draw down atmospheric carbon? See, when plants get cut down, all the CO2 they've gathered over their life gets released, either slowly as they decay on the ground or quickly when the pile gets burned. But when converted to biochar, the carbon is stabilized and once buried, decays very slowly, as demonstrated by the 2,000 year-old biochar soils of the Amazon. It seems almost miraculous, like something from classical antiquity, using fire to balance the other three elements – wind, water, and earth. It seems almost too good to true. How can there not be a thriving, multi-billion dollar market devoted to restoring forests so that the byproduct can be converted to a valuable water-filtering and soil-improving material? That's, of course, because it is too good to be true. Despite the fact that biochar can be created from any number of readily-available organic waste, from corn stover to cow manure or even algae, efforts to “industrialize” the process have proved elusive. Creating the pyrolysis equipment is very much a niche market. Building a container that can super-heat the material without oxygen, siphon off the gasses, and pump out the char is a feat of engineering and finance. Moreover, It costs a lot of money to transport the materials to an industrial pyrolysis plant, treat the biochar with the requisite minerals to “charge” it so that it can provide the chemical profile to improve soils, and then transport the bulky material back a place where it's needed. Further value can be realized in industrial settings by capturing the gasses and condensing them to biofuels, and using the heat to power and warm buildings, but even then, making "waste" profitable is a tricky circle to square.

Cornell University pyrolysis setup

But what if it didn't have to be industrialized? What if it didn't take millions of dollars worth of equipment and a complex retrofit of a building? What if we could make it in our own backyards? Indeed, the process is simple enough. Build a fire in an enclosed pit or any number of cheaply-constructed kilns with open-source designs so oxygen can't get in from the sides, and keep a “flame cap” on top so oxygen can't get in there either. Gradually add material to the surface, and the flaming top heats – but doesn't ignite – the material below. Extinguish once the pit is full, and voila, backyard biochar. Mixed with some compost to “charge” it with minerals or even just leave it in the soil to age naturally, and you have an organically rich, water-holding, soil-stabilizing, carbon-sequestering material.

Simple, "flame cap" biochar production integrated into an Oregon wildfire fuels reduction project

Maybe this is the key. If we're to harness the considerable potential of biochar, maybe it has to be an extremely localized process - at least to start with. After all, the ecological context matters. The type of feedstock material, the temperature of the pyrolysis, and the site of installation can all affect what biochar does and how effectively it does it. But preliminary research suggests it can do wonders with depleted, sandy, or compacted soils in the Midwest, providing boosts in plant vigor and crop yield, and increasingly, innovative conservationists have begun to experiment with water quality applications, from wastewater treatment to manure neutralization.

Dramatic example of biochar's potential effect on plant growth.

Is it a silver bullet for all of Iowa's ecological woes? No, of course not. There's no such thing. The problems we've got have complex causes, and will require complex, multi-disciplinary solutions. A thousand cuts require a thousand band aids. But every tool we can possibly add – especially a Swiss Army Knife like biochar – is worth investigating. Maybe it's time for us to start with a few experiments in our own gardens.

We're all taught the basics of conservation in a simple phrase - reduce, reuse, recycle. With a little proof-of-concept, maybe we can extend that mantra to include our yard waste as well.

Looking Back

It's a new year! So far, the CCCB is off to a great start.

We acquired grant funding for a few major habitat projects in the coming year. With these funds, we'll be able to restore native prairie at a long-neglected field of smooth brome adjacent to the disc golf course and archery lane. Fish habitat projects are slated for this summer at Osborne Park as well as the Joy Springs trout stream. Stay tuned next month for a deeper dive into those projects and hopefully one more in the hopper!

On the outreach front, January saw naturalists back in the classrooms, and classrooms back in the nature center. Elkader Central students came out for their annual winter field trip centered around the classic novel "Hatchet." Students learned survival skills, winter track ID, built their own survival shelters in the woods (hey, there's another use for woody debris) and went for a hike to test out their newly-minted tracking skills.

Leaving the biting winds of the great outdoors behind, naturalist Abbey Harkrader hosted 8 people at the Osborne Nature Center to create beautiful resin jewelry using UV light to cure the material. She's got a knack for combining art and nature, and all were thankful for the opportunity to learn a new craft that brings a little color to the dreary winter days.

The snowfall also gave us a great opportunity to groom our trails for cross country skiing, and the deep fluffy stuff is just perfect for snowshoeing! Shoes are available for rental at Osborne, just give us a call and we'll get you exploring.

Looking Forward

February... so short, and yet with Iowa weather, so long. Oh well, we'll make the most of it!

First up will be the Building Better Birders workshop series. The session on February 10th at 6:00 PM at the Osborne Nature Center will focus on owls and raptors, hosted with Kelly McKay of the Bio-Eco Research and Monitoring Center. Sink your talons into this one if you want to know who's stalking mice from the powerline in your neighborhood.

On February 19th, at 6:00 PM at the Osborne Nature Center Abbey will again put her artistic and pedagogical skills on display with a nature-inspired painting workshop. Class size is limited to 8 people, so call soon to register and secure a spot!

On February 27th, at 1:00 PM, Snowfest returns to the Osborne Pond! Come on out and take a crack at snowshoeing and ice fishing. The lodge will have a campfire going to warm you up, and hopefully the fish will be biting, tiny though they might still be in the newly-renovated pond.

Last but certainly not least, it's Motor Motor Time! This year's event will feature the addition of a 10K course utilizing the recently-completed Motor Mill trail, so if you want to be a part of the grand opening, check out this link for more info and registration.

As always, keep an eye on our facebook for future events and enjoy the winter weather while it lasts!


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Clayton County Conservation is now accepting applications for 2024 seasonal positions. Visit our Employment/Attracting Success page for info! 

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