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Biochar: Why and How To Use It (For Home Gardeners)

Biochar: Why and How To Use It (For Home Gardeners)

The term biochar is quite uncommon, especially for inexperienced home gardeners. Yet, it’s becoming more popular due to its benefits.

What is biochar used for? Biochar is an organic material that improves plant growth by enhancing soil quality. Adding biochar to your soil will neutralize acidity, improve the soil’s ability to retain nutrients, and increase drainage and aeration. Though results will not be immediate, over time the soil will improve.

Different types of biochar have been deposited in our earth over centuries, and adding it to your home garden will help improve the soil quality with time.

This article will answer all your questions regarding how biochar is made, how to use it, and all its advantages and disadvantages. So, let’s dive in. 

What Is Biochar?

Biochar is a broad term that refers to all the lightweight black residue that remains after the pyrolysis (high heating without oxygen) of organic matter like wood, wood residue, crops, and household waste.

This substance is made of more than 80% carbon and can be stable in soil for thousands of years. 

Black earth found in the Amazon basin is an example of biochar.

The indigenous people of the region tried to improve the soil quality by adding charred or burned organic material, eventually improving the overall quality of the soil. 

How Is Biochar Made?

Biochar occurs when the organic matter is carbonized in an oxygen-free environment at very high temperatures.

As a result, the water, oils, and gases are released, and the waste product or the carbon structure remains, forming the biochar. 

The substance forms pockets where moisture and bacteria are kept, enriching the soil and improving its traits.

Different types of organic matter can be pyrolyzed to produce various types of biochar with different qualities.

Types of Biochar

Biochar types depend on the biomass from which it’s made. This includes various kinds of feedstocks like rice husks, corn straw, hardwood scrap, paper items, animal manure, and household green waste. 

The source of the organic matter of biochar will affect its properties because its action depends on its chemical and physical characteristics.

The following table shows different types of biochar and how they behave. 

Biochar vs. Charcoal

Biochar and charcoal are both made of carbon, but other than that, there are no similarities between the two substances.

Biochar is produced by modern pyrolysis methods at temperatures that can be as high as 1,200 degrees Fahrenheit.

It’s made of different types of biomass feedstock and is mainly used to improve soil quality and provide plants with the needed nutrients. 

Charcoal is made of plant and wood material at much lower temperatures. Therefore, it has a lower porosity than biochar and is mainly used for heating. 

Biochar increases the soil’s carbon content and can also improve animal health when added to feed.

Charcoal is used in cooking and heating applications, and the activated form of charcoal can be used to filter water.

Unfortunately, charcoal contains ash, which actually harms the soil and degrades faster than biochar. As a result, it can’t replace biochar in gardening applications. 

Biochar Benefits

Thousands of years ago, the Amazonians discovered the benefits of biochar when they used to burn and bury their organic and agricultural waste.

Today, using modern science, we can still reap these benefits. Here are some of the benefits of biochar: 

  • It can help with the rejuvenation of depleted soil.
  • It reduces waste by finding a potent way of recycling organic matter. 
  • It acts as a carbon sink because the process of converting biomass to biochar produces less carbon dioxide than the process of burning biomass. 
  • It’s a natural habitat for microorganisms that improve soil quality. 
  • It can absorb heavy metals from soil. 
  • It raises the soil’s pH level to make it less acidic, supporting plant growth in areas where it was previously impossible to grow plants. 
  • It remains in the ground for centuries, reducing greenhouse gas production. 
  • It improves water quality and reduces nutrient leaching. 
  • It retains nutrients from fertilizers, improving plant health in the long run and decreasing the need for adding compost and fertilizers. 

Disadvantages of Biochar

Despite all the benefits of biochar, it has some drawbacks that you need to be aware of if you decide to use it in your garden. 

  • The frequent application of biochar can make the soil too compact, negatively impacting crop yield. 
  • It can limit the activity of earthworms in the soil, and they’re essential for plant health, as they improve nutrient cycling, increase soil aeration, and promote better plant growth. 
  • Although it increases crop production, it absorbs some of the useful nutrients in the soil. As a result, it decreases the nutrients available for the plants. 
  • It can absorb pesticides when applied to the soil, negatively impacting their effect. 
  • Biochar can affect soil’s vulnerability with respect to harsh weather conditions. 

What Does Biochar Do for Soil?

The application of biochar nourishes the soil in different ways. First, as an additive, biochar can neutralize the soil, making it more suitable for plant growth, even if it’s naturally too acidic.

This means that adding biochar allows you to grow plants where they wouldn’t grow naturally. 

It also improves water and nutrient retention in sandy soils, which are less productive than other types of soil. Biochar enhances soil aeration in clay soil, which can be too compact. 

Effect of Biochar on Plant Growth

Generally speaking, biochar increases soil fertility and improves its quality. As a result, it has a positive impact on plant growth. 

Growing plants in the soil after adding biochar will lead to a better crop yield. Barren soil can support plant growth, and the biochar’s effect can last for years. 

Biochar also reduces the need for water and fertilizer, as it helps retain them in the soil. In addition, it reduces nutrient leach, so the soil will support better plant growth. 

Is Biochar Organic?

Biochar is an organic material with high surface area and porosity.

It’s potent in treating several problems in the soil like increased acidity, poor aeration, and frequent need for fertilizers, and it doesn’t contain any chemicals. 

As a result, biochar is safe to use in organic farming setups. It’s also sustainable and presents an eco-friendly method of getting rid of waste. 

Is Biochar a Fertilizer?

Biochar is a soil amendment that improves soil quality and plant growth because it helps retain water and nutrients. However, it doesn’t add nutrients to the soil, unlike a fertilizer. 

Mixing fertilizers with biochar leads to the best results, as biochar reduces the need for the frequent addition of nutrients. 

Biochar in Farming

By increasing soil fertility, biochar has positive effects on farming. It can increase the size of land available for agriculture by nourishing depleted soil. It also improves the crop yield of low-quality soil. 

Moreover, biochar absorbs heavy metals from the soil. The plants can absorb these heavy metals, and they affect their nutritional value and quality. 

Is Biochar Good for Clay Soil?

Clay soil is made of small particles that tend to stick together and doesn’t contain a lot of nutrients or organic matter because of the tiny spaces between the particles.

Adding biochar to clay soil can help it in different ways. 

Biochar improves the water and nutrient retention in clay soil, so you can grow plants without adding fertilizers too frequently. It can also improve water aeration and drainage. 

How To Make Biochar

Commercially, biochar is produced in big ovens that heat biomass up to very high temperatures. However, as a home gardener, you can follow these steps to prepare biochar at home. 

  • Dig a hole or a trench in your garden or prepare a campfire. 
  • Add some dry wood and dry plant waste like roots, twigs, and weeds to the hole. 
  • Start the fire and watch as the smoke color changes until it turns to gray. 
  • Cover the fire with soil, leaving only a tiny hole to limit the oxygen supply. 
  • Let it smolder until you end up with biochar. 

Activating Biochar

Activating or charging biochar refers to the process of mixing it with the necessary nutrients and microbes to make it beneficial to the soil.

Adding it to the soil without charging it will result in the biochar stealing nutrients from your plants and soil first before it can release them back. 

Biochar is like a sponge that absorbs nutrients, so you can activate it by soaking it into liquid compost at a ratio of 50%.

You can also add sugar to this compost tea to make it more efficient. 

If you don’t want to use compost, you can soak biochar in a liquid seaweed feed. You can also mix biochar at a ratio of 10% to finished compost, but this activation process takes more time. 

How Much Biochar To Add to Soil

One quart of biochar is enough to nourish a square foot of soil. When mixed with compost, you can add biochar at a ratio of 10%, but you can add up to 20% when you combine it with animal manure. 

How To Apply Biochar to Soil

Biochar takes between three to six months to show its effects in the soil, so the best time to apply it would be in autumn and winter before getting ready to plant in spring.

There are several ways to add biochar to the soil. 

  • Hand mixing is an easy way to apply biochar to flower beds and indoor pots by mixing it with the soil using your hands or a rake. 
  • Tilling requires mixing it with the soil using a tiller. 
  • Top-dressing is the process of sprinkling charged biochar on top of the soil and wetting it. It can also be mixed with compost for better results. 

How Long Does Biochar Last in Soil?

Biochar can last in the soil between 1,000 and 10,000 years because of its high stability. 


Adding biochar improves the soil quality and results in better crop yield. It’s a potent way of preserving nutrients in the soil, and its effects last for thousands of years.