Biochar is a word increasingly used in agricultural circles. What is it? What is it used for? What is the hype around this?
Biochar has been used in traditional agricultural practices in the Amazon Basin of South America for more than 2,500 years. Dark, charcoal-rich soil (known as terra preta or black earth) supported productive farms in areas that previously had poor and, in some places, toxic soils.
So, what is Biochar?
Biochar is a black carbon product that helps improve soil fertility and plant growth in your garden. It is a charcoal-like product made by burning organic material (also called biomass) in a controlled process called pyrolysis. Although it looks like ordinary charcoal, biochar is produced using a specific method to reduce contamination and safely store carbon.
In pyrolysis, combustion is reduced by restricting airflow to the organic matter once it is actively burning. Heating the wood with very little air roasts it rather than burns it, preserving the material’s structure to the microscopic level. If you looked through a microscope, you’d see that a fragment of biochar made from wood is porous and consists of empty chambers. Pyrolysis keeps the structure of the wood and does not reduce it to ash!
Biochar is negatively charged and will draw positively charged chemicals or nutrients and lock them in. It is environmentally friendly and an easy way to take a waste stream that would go into a dump site or decompose naturally and sequester it to be beneficial and add something back to the earth.
What are the benefits of Biochar in the garden?
– Enhances soil structure and aeration
– Increases nutrient and water retention and availability for plants
– Supports beneficial soil microorganisms and root development
– Provides a slow-release nitrogen source through urea inoculation
– Sequesters carbon in the soil, contributing to climate change mitigation
Biochar’s immense surface area and complex pore structure are why this product benefits your garden! The long pores provide significant surface area. 1 gram of Biochar has a surface area of about 400m2.
When added to soil, raw biochar acts like a magnet — temporarily drawing surrounding nutrients and water. Raw biochar is like a blank slate and very absorbant, not yet filled with water or nutrients. This can slow down plant and soil productivity for a short period before contributing to improved plant yields. Biochar must be activated (charged/filled with nutrients and microbes) by mixing with nutrient-rich biomass (like worm casting or urea) before it’s added to the soil to avoid this unproductivity period. This activated Biochar provides a slow-release source of essential plant nutrients and supports beneficial soil microorganisms and root development by mixing this with your soil.
How to apply Biochar
When biochar is used as a soil amendment, it should be worked into the plant’s root zone—the part of the soil surrounding a plant’s roots—incorporating it into 15 cm of soil depth if possible. This way, you will fully utilise biochar’s remarkable capability to hold water, retain nutrients, and host beneficial soil biology.
Remember, your garden is only as good as the soil it’s grown in. Biochar is a simple and effective way to bring your garden soil to its full health and growing potential. Not only are you building your
soil – but you are also locking in carbon for hundreds of years.
Yes, you can make biochar at home on a micro scale by digging a trench or hole and putting a mixture of dry wood and dried plant materials such as sweetcorn stalks or perennial weeds and roots into it.
Set fire to the material which will initially give off clouds of white smoke. This is mainly water vapour and not as bad as it looks. The smoke will then turn yellow as the resins in the wood and sugars in leafy material burn followed by grey smoke.
When the smoke turns grey, cover with metal sheet or soil leaving just a small hole for an air supply. This restricts the oxygen flow and the material will become charcoal rather than just ash.
Once it has become charcoal, wet down with a hose to put the fire out and further crack the charcoal creating micro-pores with the thermal shock. Remove the covering and dig out the charcoal.
You will crush the biochar and inoculate your biochar.
This is your working garden companion for September. Print it out, keep it somewhere close, and actually use it. Take it into the garden, tick things off, write down what you're planting and make notes as you go.
By the end of September, I want this checklist to look like it has actually lived in your garden with you.
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Can one create Biochar in any way, shape or form at home?
Hello Kobus!
Yes, you can make biochar at home on a micro scale by digging a trench or hole and putting a mixture of dry wood and dried plant materials such as sweetcorn stalks or perennial weeds and roots into it.
Set fire to the material which will initially give off clouds of white smoke. This is mainly water vapour and not as bad as it looks. The smoke will then turn yellow as the resins in the wood and sugars in leafy material burn followed by grey smoke.
When the smoke turns grey, cover with metal sheet or soil leaving just a small hole for an air supply. This restricts the oxygen flow and the material will become charcoal rather than just ash.
Once it has become charcoal, wet down with a hose to put the fire out and further crack the charcoal creating micro-pores with the thermal shock. Remove the covering and dig out the charcoal.
You will crush the biochar and inoculate your biochar.
Happy Gardening!