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Charcoal for Your Garden? The Basics on Biochar

June 2021.

What is biochar?
The soil amendment now known as biochar was first created by Indigenous peoples of the Amazon basin who used it to convert nutrient-poor tropical soils into fertile soils suitable for agricultural use.

Biochar is a highly porous type of charcoal produced by burning organic material such as wood, manure, or leaves under a limited supply of oxygen and at relatively low temperatures. In other words, biochar is the product of burning biomass under specific conditions. Biochar differs from “regular” charcoal in that it is used for agricultural purposes rather than energy production. Biochar can be used in gardens and landscapes to improve soil productivity.

How does biochar work?stylized image of a tree with various benefits of biochar listed within the tree's branches and roots
Biochar’s pores soak up water and nutrients, making them available for plants to use. Biochar increases aeration by creating space in the soil, lowering soil density and increasing water retention. Biochar can also increase a soil’s cation exchange capacity (CEC) and pH level.

What are the benefits of biochar?
Converting biomass into biochar prevents the biomass from decomposing or being used as fuel, both of which emit carbon dioxide (CO2) and methane directly into the atmosphere. Thus, biochar sequesters the carbon contained within the biomass.

Besides reducing water demand as a result of its retention properties, biochar can also reduce the use of chemical and manure fertilizers, which eventually break down into nitrous oxide (N2O) and methane (CH4), powerful greenhouse gases.

Biochar also has the potential to be used as an environmental remediation tool because it can absorb heavy metals and agricultural chemicals, thereby reducing the possibility for those pollutants to enter surface and groundwaters.

For these reasons, the City of Thousand Oaks uses biochar as a soil amendment in all its plantings.

Why biochar?
While other soil amendments like mulch, compost, and manure can improve soil functions in similar ways, biochar might keep carbon out of the atmosphere for much longer than other amendments that decompose more quickly. The feedstock and methods used to produce the biochar and the conditions of the soil where the biochar is being applied have a significant effect on its lifetime, which can range from 8 to almost 4000 years!

Where can I buy biochar?
Blue Sky Biochar CEO Michael Wittman, has conducted many workshops for the City on using biochar. To learn how to purchase biochar, and ways to build healthy soils, visit his website at:

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