By Brian Zweifel, DNR Forest Products Specialist
What is Biochar?
Biochar is basically just charcoal with a special mission, to be used in the soil. The U.S. Biochar Initiative (USBI) defines it as “carbonized biomass obtained from sustainable sources and sequestered in soils to sustainably enhance their agricultural and environmental value under present and future management.”

Microscopic structure of biochar. / Photo Credit: U.K. Biochar Research Centre
Biomass, such as unmerchantable wood waste, is transformed into this carbon-rich material in a low oxygen environment, cooking most non-carbon materials out of it and leaving the material’s basic structure intact. This carbon skeleton is what gives biochar many of its desirable properties.
The former vessels and pores in the plant material are now able to adsorb nutrients and water before they can move below the rooting zone. This helps reduce nutrient leaching into groundwater and plant water stress by keeping them available in the rooting zone. This structure also has a high cation exchange capacity, making biochar very effective at binding pollutants like mercury and other heavy metals found in urban/industrial areas.
An added benefit of using biochar in degraded soils is that it is great at providing protected spaces for beneficial soil microbes. Fungal hyphae and bacteria readily colonize biochar particles, which provides protection from adverse conditions and helps improve soil health. Another very promising attribute of biochar is that it is a very stable and long-lived form of soil carbon. Studies in the Amazon Basin have found evidence of charcoal (biochar) used by indigenous groups to improve the heavily leached soils that date back several hundred to thousands of years ago. The discovery of this “terra preta,” or literally “black soil” in Portuguese, was the spark that started researchers looking into the long-lived nature of biochar, its ability to improve soil health, and the possibility of using it to sequester carbon in soils for centuries. A wide variety of scientific trials are underway across the globe, including right here in Wisconsin. Continue reading “Wisconsin DNR Begins State Nursery Biochar Trial” →