Biochar is another tool for soil management

Burning wood can create more than smoky summers and cozy winters by the stove. Roasted trees, shrubs and other plants can also be used to amend soils, store carbon and reduce hazardous fuels in forests through a product called biochar. 

This summer, two professors are teaching farmers in Alaska how to make and use biochar and how it might affect soil health. 

Darren McAvoy, an associate professor of extension and a forestry specialist at Utah State University, is in Alaska while on sabbatical. He is an expert at low-tech biochar production methods and invented Big Box biochar kilns, which are large metal boxes constructed to burn waste wood on site. These kilns are designed to preserve the carbon stored in the plants, limit the smoke produced and put little heat into the soil. 

“It is a useful alternative to burning piles when trying to reduce hazardous fuels in the forest,” McAvoy said. 

Carbon preservation is an important aspect of making biochar. Trees are full of carbon that is released into the atmosphere when they burn or rot, contributing to climate warming. By converting trees to biochar, more than a third of the plant’s carbon can be stored in the soil for hundreds of years. 

“Biochar production is perhaps the most accessible way for people to help nature take carbon dioxide out of the atmosphere,” McAvoy said. 

Biochar is also a soil amendment. Although it is not a fertilizer, it can help retain nutrients, water and microbes in the soil because it is carbon-rich and full of nooks and crannies — a handful has the surface area of a football field, McAvoy said. To fill these voids with things that plants need, McAvoy said, people should mix the biochar with compost before applying it to the soil, a process called “charging the char.”

McAvoy is working with Caley Gasch, a research assistant professor of soil science at the University of Alaska Fairbanks Agricultural and Forestry Experiment Station.

McAvoy and Gasch will conduct a series of demonstrations around the state to show individual farmers, small landowners and other interested parties how to make, use and “charge” biochar. They’ll use Ring-of-Fire kilns developed by Wilson Biochar, an Oregon-based company. These kilns are similar to Big Box kilns but are smaller and more portable.

They are planning workshops in Soldotna, Fairbanks, Palmer, Petersburg, Gustavus and Juneau and will host a webinar on Wednesday, July 24, at 6 p.m. Learn more about the webinar on the UAF website. 

McAvoy seeks to raise awareness about biochar and share how to produce it at any scale, from a backyard or small farm to wood piles the size of a house or larger. 

As part of this project, Gasch and McAvoy are studying how Alaska-produced biochar affects Alaska soils. They will apply the biochar to barley plots on the UAF experiment farms in Palmer and Fairbanks and the private Schultz farm in Delta Junction. Plots with no biochar will be compared to plots amended with biochar or compost, or biochar and compost. Gasch’s lab in Palmer will analyze the soil after application and repeat the sampling and analysis next spring. 

By measuring a variety of soil nutrient-, carbon- and water-holding properties, the researchers can evaluate how the soil responds to the biochar. They will share their work with the public at the Matanuska Experiment Farm during the Palmer Research Field Day, a free event on Thursday, Aug. 1, from 9 a.m. to 3 p.m.

The biochar for this project is made from beetle-killed black spruce in Willow, but biochar can be made from almost any available dry wood, called feedstock. 

“The best wood to use is what is available, what you want to get rid of,” McAvoy said. 

The type of feedstock and production method can result in very different biochars. For example, biochar from evergreens will likely have a higher pH than hardwood-sourced biochar.

Because biochar can be so variable, Gasch and McAvoy will send samples to a specialized lab to characterize its nature and better understand how it will interact with the soil they’re applying it to.

ADDITIONAL CONTACT: Laura Weingartner, lgweingartner@alaska.edu, 907-474-6009

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