Biochar is similar to charcoal from a wood fire, but not exactly the same. It is made by burning plant material in conditions with low oxygen. It is sometimes added by farmers and gardeners to their soils.

Biochar can bind to pesticides in soil. The effect of biochar on pesticide residues in soil varies. Some pesticides may bind to biochar more strongly than others. The binding potential depends on many things. Biochar may be useful because it could potentially hold onto a pesticide and make it less likely to move down through soil toward shallow groundwater.

Just as there are many types of plants, there are many types of biochar. Many factors affect the structure and how it works in soil. The type of plant material and burning conditions affect the structure of a biochar. This may also affect whether a specific pesticide ingredient would bind to it.

• Research has shown that biochar can bind to certain pesticide ingredients in soils or water. Other research shows that some biochar is less effective at sticking to certain ingredients.
• The best chance of pesticide binding happens when biochar and soil are thoroughly mixed. If dealing with a spill, extra biochar may be needed for the excess pesticide.
• Once an ingredient sticks to a piece of biochar, it is unknown how long it may stay there. It is also unclear whether plant roots can take it up. Over time, the ingredient could move away from the biochar (desorb, unstick) and become mobile again.
• Biochar could affect how long pesticide residues stay in soils. It can alter soil moisture, groups of microbes, and other factors that affect how fast a pesticide degrades. Strongly bound pesticides may also be protected from breakdown by microbes.
• Research about biochar and its use as a remediation tool in soils and water is ongoing.

Additional Resources

• Biochar in Colorado - Colorado State University Extension
• An Introduction to Biochars and Their Uses in Agriculture - University of Florida IFAS Extension
• The Science Behind the Biochar (webinar) - Illinois Sustainable Technology Center
• Biochar Sorption of Pesticides - Illinois Sustainable Technology Center
• Sorption Properties of Greenwaste Biochar for Two Triazine Pesticides - Illinois Sustainable Technology Center
• Biochar Database - University of California, Davis
• Biochar (pyrolysis) Publications - Washington State University

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email us at npic@oregonstate.edu.