top of page
  • Jere Folgert

What is Biochar? Does it Grow Better Garlic?

Updated: Dec 18, 2021

Have you heard of biochar? Does it have the potential to grow bigger, better garlic?


What is Biochar?

Biochar is defined as a carbon-rich product obtained when biomass, such as wood, manure, or leaves, is heated at relatively low temperatures (<700°C) in a closed container with little or no available air. This heating process is termed pyrolysis Biochar is a stable solid, rich in carbon, and can endure in soil for thousands of years. Independently, biochar can increase soil fertility of acidic soils (low pH soils), increase agricultural productivity, and provide protection against some foliar and soil-borne diseases. (source: )

Just to be clear, biochar is NOT ash. Ash is not typically a desirable soil amendment—it is just too salty. Ash is the result of typical open burning or oxidative (meaning oxygen-rich) thermal decomposition of biomass. In an oxidative process, almost all the carbon volatilizes as carbon dioxide, leaving behind primarily mineral components of the biomass rich in potassium and other salts.

Biochar technology shows promise in improving soil quality, as well as reducing waste and producing energy as a byproduct. This “newly found” organic fertilizer is a safe, effective soil amendment with a plethora of benefits from increasing water retention and soil microbes to reducing greenhouse gas emissions. Biochar is short for “biomass charcoal.” Biochar, a specialized type of charcoal where it's structure is extremely porous. This porous surface is what gives biochar its numerous benefits in the garden, as it creates sites to hold nutrients and moisture, and habitat for microorganisms.

Biochar is produced by thermal decomposition of organic material (biomass such as wood, manure or leaves) under a limited supply of oxygen (O2), and temperatures typically between 300°C and 700°C under oxygen-deprived conditions, a process known as “pyrolysis. This process mirrors the production of charcoal, which is perhaps the most ancient industrial technology developed by humankind. Biochar's primary application is use as a soil amendment with the intention to improve soil functions and to reduce emissions from biomass that would otherwise naturally degrade to greenhouse gases.” This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security, and increase soil biodiversity, and discourage deforestation. The process creates a fine-grained, highly porous charcoal that helps soils retain nutrients and water. The interest in biochar stems from the fact that this pyrolysis residue may have myriad uses as a soil amendment to, among other things, sequester stable carbon in soil, provide water and nutrient adsorption capacity to soils, and even suppress soil-borne plant pathogens. Many research projects around the world have been, and are underway to explore its potential benefits and limitations.

Biochar is found in soils around the world as a result of vegetation fires and historic soil management practices. Intensive study of biochar-rich dark earth in the Amazon (terra preta), has led to a wider appreciation of biochar’s unique properties as a soil enhancer.

What Does Biochar Look Like?

In terms of physical attributes, biochar is black, highly porous, lightweight, fine-grained and has a large surface area. Approximately 70 percent of its composition is carbon. The remaining percentage consists of nitrogen, hydrogen and oxygen among other elements. Biochar’s chemical composition varies depending on the feedstocks used to make it and methods used to heat it.

How is Biochar Made?

Materials, such as wood chips, leaf litter or dead plants, are burned in a container with very little oxygen. As this mass burns, they release little to no contaminating fumes. This "burning process" is called pyrolysis. During pyrolysis organic materials, During the pyrolysis process, the organic material is converted into biochar, a stable form of carbon that can’t easily escape into the atmosphere. Biochar is an efficient way of converting carbon into a stable form and is cleaner than other forms of charcoal.

What are the Physical Attributes of Biochar?

In terms of physical attributes, biochar is black, highly porous, lightweight, fine-grained and has a large surface area. Approximately 70 percent of its composition is carbon. The remaining percentage consists of nitrogen, hydrogen and oxygen among other elements. Biochar’s chemical composition varies depending on the feedstocks used to make it and methods used to heat it.

What is the History of Biochar?

The concept of biochar is rooted in an ancient Amazonian practice. The word "biochar" is a late 20th Century English neologism derived from the Greek word βίος, bios, "life" and "char" (product of carbonisation of biomass, as charcoal). Although biochar technology is considered a more recent strategy for carbon sequestration, the practice of adding charred biomass to improve soil quality is not new. This process is modeled after a 2,000-year-old practice in the Amazonian basin, where indigenous people created areas of rich, fertile soils called terra preta (meaning “dark earth”). These ancient fields of biochar are still incredibly fertile. Today’s technology creates a similar product, but using cleaner burning machines. Biochar is touted as a potential solution to greenhouse gas emissions. There are numerous methods to dispose of biomass waste being used today, such as composting, incineration, and slash-and-burn. Of all the many methods of waste disposal, creating biochar is currently considered to be the most environmentally friendly. It is the only method that does not release greenhouse gases into the atmosphere, and the resulting product sequesters atmospheric carbon in the soil for thousands of years. By using biochar in your garden, you are supporting a new technology with the potential to make a huge difference for Mother Earth.

What are Applications of Biochar in Garlic Production?

Biochar can be an important tool to increase food security and cropland diversity in areas with severely depleted soils, scarce organic resources, and inadequate water and chemical fertilizer supplies. Chemically, biochar does not add any nutrients to the soil. Its benefits come primarily from its unique structure. Although it is a source of carbon, it can take thousands of years to break down fully. However, it can improve organic matter content by creating a better soil for organic matter to build up.

Soil degradation is a major concern in agriculture globally. To address this burgeoning problem, researchers suggested applying biochar to degraded soils in order to enhance their quality. Some of the ways that biochar may help improve soil quality include:

  • enhancing soil structure

  • increasing water retention and aggregation

  • decreasing acidity

  • reducing nitrous oxide emissions

  • improving porosity

  • regulating nitrogen leaching

  • improving electrical conductivity

  • improving microbial properties

Biochar also improves water quality and quantity by increasing soil retention of nutrients and agrochemicals for plant and crop utilization. More nutrients stay in the soil. In addition, biochar helps balance pH, it reduces the need for fertilizers, and minerals are delivered to plant roots more easily, and “carbon sequestering” reduces the release of carbon dioxide into the atmosphere. Biochar is also found to be beneficial for composting since it reduces greenhouse gas emissions and prevents the loss of nutrients in the compost material. It also promotes microbial activity, which in turn accelerates the composting process. Plus, it helps reduce the compost’s ammonia losses, bulk density and odor. Biochar attracts and retains water molecules, thus improving the water holding capacity of the soil. It is especially useful in this respect for areas with low rainfall and soils with poor water retention. It decreases nutrient leaching and increases cation exchange capacity (CEC) so nutrients are more available for plant roots to take up. Biochar has a negative charge that binds to nutrients such as calcium, potassium and magnesium. This also results in reduced soil acidity (a higher pH). The nutrient binding means that less fertilizer is needed. Since there’s less run-off of nutrients, it is safer for groundwater and surface water too.

Does Biochar Benefit Soil Biology?

Biochars have the potential to immobilise heavy metals, pesticides, herbicides, and hormones; prevent nitrate leaching and fecal bacteria into waterways; and reduce N2O and CH4 emissions from soils. Perhaps the most striking example of biochar in action is the rich soil known as “terra preta” (black earth) in the Amazon basin, where over a thousand years ago natives burned jungle plants and branches in slow smoldering piles and combined the charcoaled remains with manure to enrich nutrient-deficient clay soil. Unlike compost, biochar does not decompose and its benefits can last hundreds of years. The terra preta remains fertile to this day.

How do I use Biochar to Improve Soil Quality?

Biochar is applied to agricultural soils using a variety of application rates and preparation techniques. The rate of application and preparation of the biochar will largely depend on specific soil conditions as well as on the materials used to make the biochar. It is often recommended to mix biochar with compost or other materials to inoculate it with nutrients and beneficial organisms. The recommended method for applying biochar will vary depending on how healthy or nutrient-depleted your soil is. Before you use biochar in your own garden or farm, you should first consider the state of your soil. For more information on how to apply biochar on different kinds of soils, check the guidelines on International Biochar Initiative and Wakefield Biochar.

What is Charging or Activating Biochar ?

The porous structure of biochar creates the perfect habitat for soil microbes and beneficial fungi to flourish. Although the microorganisms will eventually move into the biochar, you will see an even bigger benefit if you “pre-charge” or “activate” your biochar (this process is also sometimes called inoculating, maturing, culturing, or charging the biochar). This optional step is done prior to incorporating the biochar into your garden, and has the added benefit of preventing excessive nutrient binding (where so many nutrients become bound up with the biochar in the soil that not enough are available to the plants for a short time. Eventually, the biochar will affect a nutrient gain, once the binding evens out). Aim for up to a one-inch layer of biochar, mixed to a depth of at least six inches to get it to the root zone. Keep in mind this is a one-time operation; You only need to add it once, because it will last for a lifetime.

To activate your biochar, the preferred method is to mix it into your compost pile as you build it. You can add as much biochar as you will need for your whole garden, up to a maximum of an equal ratio with the compost. Not only does this improve the effects of the biochar when it is added to your soil, but it also improves the compost process itself – resulting in a shorter composting time, stimulated microbial activity, reduced gaseous emissions, and reduced odor. If you use soiled farm animal bedding in your compost piles, you can “double-charge” biochar by spreading it up to an inch thick in the fresh bedding. By the time it is spent, collected, composted, and ready to spread on your garden soil, it will be well activated. Another effective way to activate biochar is to include it when brewing your own compost tea. Just stir it into the water before adding the other compost tea materials, and brew as per the regular instructions. You can potentially use a shortcut to activate biochar.

If you don’t have the time to activate your biochar by either of these methods, you can choose from a few shortcuts. A week or two ahead of when you will use the biochar, mix it with finished compost, organic fertilizer, worm castings, humates, and/or mycorrhizae. Incorporate biochar with any of these just prior to adding them to the soil. Irrigate, and wait a week or two before planting. If you choose not to activate your biochar, you can instead encourage microbes to “move in” to the biochar’s porous surface by wetting it down before mixing it into the soil. However, even if you don’t do anything to the biochar before incorporating it into your garden, you will still see the benefits of increased water retention, microbial activity, organic matter, nutrient retention, and improved soil structure.

Biochar and Garlic?

Biochar has been shown to have some benefits in the garden and it might be a good amendment for soilless potting mixes, but here is the problem. Should we all be adding biochar to our garlic patch? Maybe not? Biochar is not one product. It can be made from many different input ingredients, in many different ways. The result of each process is a different product with its own special characteristics. There are no standards so you can’t pick up a bag and say, “this is the one that will work best in my soil type”. You are left with buying a bag of something and hoping it works. You have the same issue with buying compost – who knows what is really in the bag? Biochar has the potential to increase fertilizer efficiency, remove pollutants and pesticides, increase soil moisture, increase soil pH, increase soil microbe populations, and increase cation exchange of soil. But there is one big difference between compost and biochar. Unlike biochar, compost decomposes in a few years. A bad batch of compost is a short-term problem. Biochar may not last a thousand years, but it certainly lasts a lifetime. What do you do if you add a bad batch to your soil? Many studies have shown that too much biochar is harmful to plants and soil. You can’t correct this problem without removing the soil. It may be more beneficial in acidic soil where the increase in pH is desirable. It has also been shown useful in reducing compaction in lawns and poorly drained soil. If you want to try it, start small and use some test areas. Keep the amounts small. Document the product you use so you can buy the same product again. Compost seems to offer most of the same benefits without the downside.

256 views0 comments

Recent Posts

See All
bottom of page