In February 2024, The Davey Tree Expert Company fired up its new biochar facility in East Dundee, Illinois. The facility recycles wood waste from its many client properties in the Chicago area and turns it into an environmentally friendly soil additive, biochar.

“Biochar is a carbon-rich, charcoal-like substance that offers many benefits to the soil,” says Jim Zwack, vice president and general manager, Davey Institute. “Incorporation of biochar into the soil can help resist soil compaction, improve infiltration and retention of water, hold nutrients and absorb salts. It also doesn’t decompose, unlike compost, so it will continue to provide benefits for many years.”

Davey, an accredited, 48-year TCIA member company headquartered in Kent, Ohio, joins several other tree care companies across the country in exploring the business of biochar, converting leftover biomass from tree operations into both a beneficial soil additive and a tool for carbon sequestering.

Heading up the operation at Davey is Mike Veney, director of environmental programs at the Davey Institute.

In 2016, Davey started to investigate biochar technology.

“Several companies make biochar from trees damaged from the pine beetle or other forest areas out West, taking the dead trees and cutting that wood and making it into biochar. We thought, if they are doing that, why can’t we do that with our woodchips, and we started to look for that technology,” Veney says.

Pyrolysis rotary-drum technology

Davey decided to jump in and, after doing its research, went on to work with Biomass Energy Techniques Inc. (BET) to incorporate BET’s pyrolysis rotary-drum technology for its process. Instead of using a batch process, producing one batch at a time, this technology enables Davey to produce char continually, without taking the lid off or dumping the kiln.

Workers make sure the drum has the feed stock to keep running, and they must empty the hoppers of biochar, but otherwise don’t have to touch the machine at all, a process that works for Davey, says Veney. Another advantage of BET’s technology is that, once it is going, its fuel is the woodchips themselves. “We use natural gas at start up to get the PRD (pyrolysis rotary-drum) to temperature,” Veney notes.

Making the move to biochar

Why did Davey decide to invest in biochar?

“Wood waste is becoming a big issue in the industry overall,” says Veney. “We generate hundreds of thousands of cubic yards of biomass every year. Depending on where our operations are, they were finding ways to dispose of that wood waste – to be used as compost or to go into landfills. We always thought that wasn’t waste, but a valuable product, something that could be used to help the environment. So it (investing in biochar) was a way to help our operations – take something that was a cost at one time and turn it into a revenue stream.”

The system they went with can produce about 7,500 yards of biochar a year from 30,000 yards of woodchips. For the Chicago area, that is just a drop in the bucket, Veney notes. Chips come in from a chip truck, get dumped and go through a secondary-grind process to create consistently sized woodchips and to remove any trash, rocks or anything else that could damage the machine. The result is a uniform product, with no need for further processing or grinding, according to Veney. “Right now, we use it as is, but we are looking at several different specs for different clients for what they need,” he says.

Secondary benefits

A network of biomass equipment operators provides feedback to one another on a regular basis, Veney notes of this evolving technology, and says there may be additional options for Davey to consider down the line.

“For the first year, we did not want to overcomplicate the build process – we wanted to make it easy as possible for the first one,” he says. “Down the road we can retrofit this first unit. We plan to look into electric- or heat-transfer technology that goes along with this.”

Controlling emissions

The equipment is designed to burn the woodchips in a high-temperature, low-
oxygen environment, so, for the most part, volatile organic compounds (VOCS) and other toxic compounds are burned away in the process, says Veney. Davey has an Air Pollution Control Permit from the Illinois Environmental Protection Agency, and will do stack testing to make sure its assumptions are correct. “The emissions level on it is incredibly low,” he says.

Broad uses

Biochar covers a wide range of technology, according to Harry Groot, an environmental consultant for Dovetail Partners who wrote an April 2021 Tree Care Industry Magazine article, “Expanding Knowledge of Biochar and Its Strengthening Markets.” (To view that article, go to tcimag.tcia.org and, under the Resources tab, click Magazine Archive, or, in the digital version, click here.)

The simplest techniques are inexpensive flame-capped kilns that arborists can move easily from one site to another, which result in a significant volume reduction of woody debris, according to Groot. Tree workers can then use the char on site, or move it to another site to be aggregated and sold. The cost ranges from about $1,000 for a flame-capped kiln to millions of dollars for a more complex biochar plant.

Uses and markets

Biochar uses include landscape applications by the company making it itself or selling to markets such as retail landscapers, greenhouse growers, vineyards, orchards and homeowners, according to Groot. Units can produce heat for a secondary use like wood drying of feedstock or firewood or other heat-intensive processes. Or, with more advanced technology, it can produce syngas (a mixture of hydrogen and carbon monoxide that is combustible and can be used as a fuel), wood vinegar (a byproduct that can be used as a soil amendment and for other agricultural applications) and biofuels (such as a fuel similar to charcoal).

Commercializing biochar

Meanwhile, Davey is still in the pilot phase, and has not yet started full production. The company is exploring the best way of selling biochar, such as in bulk to a fertilizer or compost company or bagging it up to sell to other landscape companies or to clients and the general public.

“We don’t know the best market yet,” Veney says. “We are still at the proof and concept stage, we have one kiln now and plan to do two more in the future. And we don’t see why our concept will not prove itself out,” he adds. The vision is that wherever Davey has a density of office locations, it would make economic sense to put one or more of these kilns in to convert woodchips to biochar, he says.

Test run

In February, Veney fired up the unit for the first time to do test runs. He hoped to start production by the end of May. “We’ve been dialing the machine in to try to get it into the operating parameter we are looking for,” he says. “I feel really good about it, but we’re a little behind, so I am anxious to get it up and running in full production.”

Davey is committed to the future of biochar and promoted Veney a year ago to director, environmental programs. His department is responsible for environment and pesticide compliance, pesticide and fertilizer licensing and sustainability. The biochar falls into the sustainability program, essentially trying to find a circular economy for the woodchips.

“It’s one of the ways we are going to deal with woodchips. This technology doesn’t work everywhere. You have to have a substantial supply of woodchips coming in all the time to keep the machine fed, and not every area is going to have that. There are more things for us to discover on how best to use woodchips,” says Veney.

Bartlett research on biochar

Bartlett Tree Experts, an accredited, 49-year TCIA member company headquartered in Stamford, Connecticut, was one of the early adoptors of biochar. Though scientists had researched biochar for uses in agriculture, they had not studied results for tree care, which is where Bartlett took up the lead, according to Kelby Fite, Ph.D., vice president and director of research at the Bartlett Tree Research Laboratories.

“We first heard of biochar when our director of research at the time, Dr. Bruce Fraedrich, heard an informational piece about it on NPR,” says Fite. “This was around 2009, and we jumped into research immediately.”

Scientists from Bartlett, including Fite, undertook several research projects on residential and commercial properties to gauge the benefits of biochar, and have been testing its use on a variety of greenhouse and field sites ever since.

“After researching it for a couple of years, we began using it commercially on clients’ properties. During this time, one of our research staff, Dr. Drew Zwart, was investigating the affects biochar can have on plant physiology and disease resistance. His groundbreaking work showed that many of the phenomena that occur when biochar is applied to agronomic crops occur in woody plant systems as well.”

Results show more than improvements

Results not only show improvements in soil fertility and water retention, but also a resistance to certain insects and diseases in trees, according to the studies, which the company is continuing to research.

“We apply biochar when soils are low in organic matter,” continues Fite. “This is often accompanied by other characteristics of urban soils, such as compaction. We can incorporate biochar and relieve compaction simultaneously with our “Root Invigoration” program, where we loosen soils with the use of an air tool and then blend compost, biochar and prescription nutrients into the loosened soil. In situations where we cannot use the air tool or it isn’t necessary, we can use a suspension-grade biochar and inject a slurry into the soil, focused in the root zone of the trees and shrubs.”

Bartlett now offers a “premium landscape biochar” that it promotes as good for improving soil quality for healthier trees while also sequestering carbon that would otherwise contribute to elevated levels of greenhouse gases.

Is it a viable income stream?

Dan Mayer of Mayer Tree Service, a 32-year TCIA member based in Essex, Massachusetts, is one tree care company owner who has done his own research on biochar. “I experimented with a few biochar devices, from large-scale commercial setups to mad-scientist backyard devices. Getting a consistent finished product was always the most difficult to achieve,” says Mayer.

“It is most often referred to as like making cookies. Without controlling the particle size, species and moisture content of the feedstock, it is hard to achieve an even, well-baked, consistent material. Or basically, a good cookie, if you also can’t control the quality of the ingredients going into the batch.

“If you are doing it as a way to get rid of wood waste by burning it and calling the charred bits you’re left with biochar, well, then you may never have looked at the two under the microscope to realize the goal of a well-baked biochar. You have only made charcoal, but you did get rid of your junk wood, I suppose.”

Resources

For further information about biochar, you can view a technical report authored by Bartlett’s Kelby Fite, Ph.D., available at https://www.bartlett.com/resources/technical-reports/biochar-soil-amendment-frequently-asked-questions.

Tamsin Venn is founding publisher of Atlantic Coastal Kayaker magazine and author of the book “Sea Kayaking Along the New England Coast,” and has been a contributing writer to TCI Magazine since 2011. She lives in Ipswich, Massachusetts.