Biochar for forest industry and oak regeneration in the southern Appalachians
In November 2024, a small group of researchers, fire management experts, technicians, and foresters gathered around a CharBoss with Michael Parker, a trainer from AirBurners. The CharBoss burns wood – typically woody debris – and creates biochar.
From left to right, Tara Keyser, Philip Whiting, and Jack Purcell stand in front of a heap of newly cooked biochar.
“Biochar is carbon, it’s a wood product, and it has many potential uses,” says USDA Forest Service researcher Tara Keyser. Biochar is a type of charcoal that is used as a soil amendment.
This particular machine belongs to the Forest Service. The Southern Region and the Washington Office of the Forest Service acquired funding for it, and the Southern Research Station is exploring its potential – especially after the Pactiv Evergreen paper mill in Canton, NC closed in 2023.
Without the mill, smaller midstory trees once designated for harvest as pulpwood now have no market and will stay in the forest. Removing smaller midstory trees is a common management goal. Across the eastern U.S., most forests are mature and closed canopy, while open forests and young forests have become rare.
“The closure of this mill is affecting forests, the ability to manage forests, and the forest industry across western North Carolina and parts of Tennessee, Virginia, and Georgia,” says Keyser.
The CharBoss can consume up to two tons of branches, small trunks, and other woody feedstock every hour. About 20-30 percent of that wood will become biochar.
Next up, Keyser and her team – which includes Brandy Benz, Antigone Burke, Jack Purcell, Phillip Whiting, and others – will cook 10,000 pounds of biochar for a restoration study. The Southern Region is an important contributor to the work, providing people, expertise, and, potentially, heavy equipment for loading wood into the CharBoss.
“The National Forests in North Carolina is a key partner and provided funding for the forest soil amendment part of the larger study,” says Keyser. “These studies would not be happening without their leadership and technical staff.”
In collaboration with Jodi Forrester of North Carolina State University, the team will apply biochar to plots on a young forest where the researchers are studying oak regeneration. Oaks are currently the backbone of many forests – they are the biggest and most dominant trees present. However, the next generation of trees rising up to replace them is not oak but is often maple or tulip poplar. Regenerating oaks across large areas has proven very challenging, although there are resources for landowners.
“Poplar and maple are nitrogen hogs and lovers,” says Keyser. “Locking up some of that nitrogen with biochar could tilt conditions to favor the oaks and hickories.”
Antigone Burke and Brandy Benz are removing the fresh biochar from the machine and cooling it. The biochar will eventually be used in a study on ecological restoration.
Biochar can play many roles in the soil, and the type of wood used to make biochar affects its properties. Two projects funded by the Bipartisan Infrastructure Law projects are designed to show which properties of biochars affect its ability to absorb heavy metals. This laboratory work will be conducted by Tom Elder and his colleagues at Auburn University. That team is measuring the physical and chemical properties of different biochars, such as their pH, surface area, the size and distribution of pores, and amounts of carbon, hydrogen, oxygen, and nitrogen in the biochar.
For the current biochar production effort, the machine will stay at Suncrest Mulch in Waynesville, North Carolina. John Fletcher owns this mulch operation. He operated it as a chip mill until after the paper mill closed in 2023, when he converted it to a mulch operation. He hopes to offer biochar to his customers.
For now, Keyser and her team will be busy making biochar and conducting ecological research. The hope is that biochar can store carbon, provide a market for small woody materials, and help keep forests healthy for future generations.
The CharBoss was developed by the company AirBurners through a Cooperative Research and Development Agreement with the USDA Forest Service.
For more information, email Tara Keyser at tara.keyser@usda.gov