Biochar: Why it is so valuable for your tree

Table of Contents

• What is biochar?
• What can biochar do?
• What is the difference between biochar and fertilizer?
• Are biochar and terra preta the same thing?
• How is biochar used correctly?
• Storing carbon through biochar
• Tree bath worm compost

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

Unlike barbecue charcoal, biochar is not used as fuel, but as a soil improver and long-term carbon sink. This also makes it interesting from a climate policy perspective.

What can biochar do?

According to Study by the Swiss research institute Agroscope (2021) biochar can have the following effects on the soil:

• promotes root growth
• supports humus formation
• improves the soil structure
• increases water storage capacity
• It can bind nutrients and thus reduce their leaching.
• 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 substantially enrich it with nutrients. Therefore, it is not a substitute for fertilizer, which specifically supplies the soil with nutrients.

Ideally, biochar and fertilizer should be viewed as a combination: While fertilizer releases phosphorus and nitrogen, for example, biochar can help retain these nutrients in the soil and reduce their leaching. Trees need nutrients, healthy soil life, and a good soil structure that can absorb and store water and nutrients.

We generally recommend the Combination of biochar with worm compost.

Are biochar and terra preta the same thing?

Biochar is a component of the famous Terra Perta (“Black earth”) from the Amazon region. This extremely fertile soil was created through the long-term combination of 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, stable humus – Terra Preta. In your garden, you can use biochar and compost to create your own nutrient-rich soil. All you need is biochar and, for example, a good worm compost.

How is biochar used correctly?

We recommend enriching biochar before application and only then working it into the soil. Follow these steps:

• Place the charcoal in a bucket of organic liquid fertilizer and let it soak for about 48 hours. Make sure the fertilizer is enriched with microorganisms – for example, liquid worm compost.
• After 48 hours, you can work the charcoal into the soil. For new plantings, you can add it directly to the planting hole; for existing trees, work it superficially into the area around the base of the tree.
• We recommend a substrate volume of approximately 5–15%, and for new plantings, approximately 1–2 shovels per planting hole.
• You can also distribute the liquid fertilizer evenly around the root area.

If you don't have liquid fertilizer available, you can also activate the biochar with compost, bokashi, or another organic fertilizer.

Always refer to the instructions for the respective product.

Storing carbon through biochar

Plants absorb CO₂ from the atmosphere as they grow. If the plant material is subsequently converted into biochar through pyrolysis, the carbon stored within 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 small amounts of biochar: To a small extent, you bind carbon in the soil and thus contribute to the reduction of greenhouse gases.

Tree bath worm compost

If you want to use biochar effectively, you should enrich it with microorganisms and nutrients before applying it. Worm compost is particularly well-suited for this. It introduces living soil organisms and plant-available nutrients that colonize the biochar and remain available there long-term.

At Baumbad you will find high-quality Worm compost, specifically tailored to the needs of urban and garden trees.