Soil Building 201: Biochar

[This post was originally written for and appeared on the blog for the Garden Tower Project.]

While we are on the topic of putting the gardens to bed and building soil and dreaming of rich gardens in 2017, let’s look into biochar.

What is it?

Biochar is a valuable soil amendment, first and foremost. According to the International Biochar Initiative, “This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security, and increase soil biodiversity, and discourage deforestation. The process creates a fine-grained, highly porous charcoal that helps soils retain nutrients and water.” (1)


Simply, it is a charcoal made at low temperature that is often then inoculated with beneficial bacteria and soil organisms that inhabit the very porous and expansive surface areas. Because nutrients, beneficial soil organisms and water are all held by the biochar and slowly released, soils are greatly improved—and maintain their fertility over a long period of time. These were first found as terra preta in the Amazon, where they worked miracles holding fertility in tropical soils. Biochar is useful when incorporated into temperate soils as well.

Image: By K.salo.85 (Own work) [CC BY-SA 3.0 (], via Wikimedia Commons from Wikimedia Commons

Biochar is now used agriculturally, not just to build fertility in the soil, but for animal feed and health as well—as biochar isable to capture and purge harmful bacteria in the digestive systems of many domesticated farm animals. As a feed additive, it is very useful. A 2012 report stated that 90% of European biochar was used in livestock farming. (2) We can find activated charcoal on the shelves of health food stores to deal with digestive issues. Feeding biochar to livestock is right in line with this practice.

Secondly, biochar can help to address climate change by storing stable carbon in the soil for a perhaps hundreds of years. While there are many ways to build carbon in the soil and remove it from the atmosphere (rotational grazing, for example), biochar may be an important aspect of addressing climate change and providing terrestrial system benefits simultaneously.

What can it do for you? 

  1. Incorporate it into your garden soils
  2. Consider it as a feed additive if you have livestock
  3. Learn or encourage others to make it and provide it as a product in the community. Note that anytime you introduce bacteria and new components into an ecosystem, you should be knowledgeable about what it is you are incorporating and how to observe the space to note impact.

Another cautionary note:

When thinking about biochar as a solution to carbon dioxide in the atmosphere, it might be tempting to think that cutting down trees and creating biochar is the solution. After reviewing the situation, we know that we need our large trees and established forests to do what they do best—and provide the many ecosystem services they already provide (as well as inspire and move us to connection). What we need now are new forests and new ways of working with agroforestry in those new forests and grasslands to produce with biochar. Fortunately, this is something many excellent people are researching.