Biochar: Why it is so valuable for your tree

Biochar is a fascinating natural product that improves soil and permanently binds carbon. In this article, you'll learn exactly what biochar is, how it works, and how to use it correctly.

What is biochar?

Biochar is made from plant material such as wood or straw. Unlike conventional combustion, the material is not burned with flames, but rather in a special process called pyrolysis. The unique feature of pyrolysis is the combination of extremely high temperatures (400 to 700 °C) with little to no oxygen. The organic matter chars slowly and evenly. The result is a homogeneous, finely porous, and carbonized material with a very high carbon content and an enormous internal surface area.

In contrast to charcoal, biochar does not serve as a fuel, but as a soil improver and as a long-term carbon store, which also makes it interesting from a climate policy perspective.

What can biochar do?

According to a study by the Swiss research institute Agroscope (2021), biochar has the following effects on the soil:

• promotes root growth
• supports humus formation
• improves the soil structure
• increases water storage capacity
• increases the availability of nutrients
• reduces heavy metal pollution
• stores carbon long-term
  

What is the difference between biochar and fertilizer?

Biochar stores carbon for a very long time. It improves the soil, but does not enrich it substantially with nutrients. Therefore, it is not a substitute for Fertilizerwhich enriches the soil with nutrients.

Ideally, biochar and fertilizer are seen as a combination: While fertilizer, for example, releases phosphorus and nitrogen, biochar can increase the plant availability of these two nutrients in the soil. Trees need nutrients, healthy soil life, and a good soil structure that can absorb and retain nutrients and water.

If biochar is mixed with fertilizer, Terra Preta can be created. We generally recommend Combination of biochar with worm compost.

Are biochar and terra preta the same thing?

Biochar is a component of the famous Terra Preta ("black soil") from the Amazon region. This extremely fertile soil is created by combining biochar with organic material such as kitchen waste, compost, manure, and microorganisms.

While biochar is a structural material on its own, its combination with organic matter creates a living, permanent humus – Terra Preta. You can easily create your own Terra Preta in your garden using biochar and compost. You'll need biochar and, for example, a good worm compost. 

How is biochar used correctly?

We recommend enriching the biochar first and then burying it. Follow these two steps:

1. Place the charcoal in a bucket of liquid fertilizer and let it sit for about 48 hours. When using liquid fertilizer, make sure it's made from organic materials and enriched with microorganisms. Liquid worm compost, for example, is particularly recommended.
2. After 48 hours, you can work the charcoal from the liquid fertilizer into the soil. For new plantings, you can add it directly to the planting hole; for existing trees, work it in superficially. We recommend about 5–20% of the volume of the substrate, and for new plantings, approximately 1–2 scoops per planting hole. You can distribute the liquid fertilizer evenly in the root area of the tree. 

If you don’t have liquid fertilizer, you can also activate the biochar with compost, bokashi or. 

Be sure to follow the instructions included with the product you purchased.

Storing carbon through biochar

And biochar offers another advantage: as a carbon store. Plants absorb CO₂ from the atmosphere during their growth. If the plant material is then converted into biochar through pyrolysis, the carbon stored in it remains stable for centuries.

Instead of escaping back into the atmosphere as CO₂, as happens with decomposition or combustion, the carbon is permanently stored in the soil. This principle is called a carbon sink.

Even if you only add a small amount of biochar to the soil, you are still binding carbon in the soil to a small extent and thereby reducing greenhouse gases.

If you would like to learn more about biochar, we recommend following article from Federal Agricultural Information Center.

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