What is it and how is it made?
What is Biochar?
Biochar is a special form of plant-based charcoal. It is produced when plant remains such as wood, straw or other biomass are burnt at very high temperatures -but almost without oxygen. We call this process pyrolysis.
And how is biochar produced?
We heat biomass (e.g. wood waste, straw, nutshells) in a closed container.Hardly any oxygen is allowed in, so the material does not burn completely, but simply carbonises.The end result is a black, porous charcoal: biochar.
What can biochar be made from?
From wood, branches, straw, nutshells, leaves, crop residues or even manure.Important: The raw material should not contain any toxic substances such as paint, varnish or chemicals.
Why do we need biochar?
1. Improve the soil and strengthen plants Biochar acts like a sponge: it can store water and nutrients and slowly releases them to the plants. This is especially helpful in dry or nutrient-poor soils. The many small pores provide a habitat for beneficial soil bacteria and fungi that keep plants healthy.
2. Biochar can balance the pH value of acid soils and improve growth.
3. Climate protection by storing carbon. Plants absorb CO₂ from the air as they grow. If the plant leftovers are turned into biochar and put into the soil, the carbon remains locked up in there for many years or even centuries. This helpsto slow down climate change because less CO₂ is released back into the atmosphere.
4. Less fertilisers and more respect for the environment. As biochar stores nutrients, less artificial fertilisers are needed. It prevents such fertilisers from entering the groundwater and polluting rivers. Biochar can even filter harmful substances from the soil or water.
How much can Biochar absorb?
Biochar can store between 2 and 22 times its own weight in water. Depending on its structure, 1 kilogram of biochar can absorb between 0.8 and 2.3 litres of water.
In addition to water, biochar also stores nutrients such as nitrogen, phosphorus and potassium.
A visual explanation:
Imagine biochar as a huge underground hotel: in every room (pore), water and nutrients can “stay overnight.” When plants are thirsty or hungry, they take what they need from these rooms. This keeps the soil moist and fertile for longer, even gric doesn’t rain for a while.
What is biochar used for?
Water storage: Keeps water in the soil, helps plants during in dry conditions.
Nutrient storage: Ensures that plants are better supplied with nutrientsfor a longer period of time.
Soil improvement: Makes the soil looser, airier and promotes root growth.
Climate protection: Binds carbon and helps to remove CO₂ from the atmosphere.Waste recycling: Makes good use of plant residues instead of burning them or letting them rot.
Pollutant filter: Can bind pollutants in soil or water.Livestock farming and water purification: Also used as an additive in livestock farming and to purify water.
How can you make biochar yourself?
There are simple methods, such as burning biomass in pits or in special metal containers (e.g. Kon-Tiki kiln, Big Box Kiln).
For larger quantities, there are special kilns or large metal boxes that can be filled with a tractor shovel.
Blueprints for these systems are available free of charge on the Internet (e.g. ‘Big Box Biochar Kiln’)
Summary
Biochar is plant-based charcoal that is produced from plant waste by heating it without oxygen. It makes the soil more fertile, stores water and nutrients, protects the climate because it binds CO₂, and helps to protect the environment. Biochar is therefore becoming very important again in agriculture and environmental protection.
Author: Francesco del Orbe
