Horticultural Charcoal

Horticultural charcoal is a great soil amendment that can also be referred to as biochar.  Charcoal is commonly used as a fuel due to the oils and volatile organics found in the carbon structure of the coal.  “Horticultural charcoal” is different because it is not specifically used as a fuel, but as a soil amendment.  It’s a common practice to interchange charcoal and biochar, but not all charcoal is good for the soil.  Charcoal mined from the ground is very different than char that is produced from a plant.  Biochar is a biomass that has been converted to a carbon-based material that is added to soil to boost fertility. In West Africa and the Amazon rainforest, biochar has a history of use in indigenous farming, where the amazing effects are still seen today. 

Recent studies show that this ancient farming method still has the ability to improve crop production while also reducing atmospheric carbon dioxide. Additionally, biochar has a wide range of advantages for the soil in your yard or garden.

What is Biochar?

Biochar is a soil conditioner that helps sustain and replenish the growing environment for plants and other organisms.

The word “biochar” comes from the conversion of biomass to char.  Its main ingredient is carbon, which is also the key component that helps preserve a wide range of other vital elements necessary for life.

European immigrants in South America gave it the name “Terra preta de Indio,” which is still a fairly common Portuguese word for biochar. 

How does Biochar improve soil?

While producing char from plants and other biomass may seem like an odd strategy to increase crop output, pre-Columbian farmers in South America proved the theory more than 2,000 years ago when they applied biochar to the barren soils of the Amazon rainforest to transform it into fertile soil.

Even today, the biochar-improved soils from so long ago are still productive and have up to 35% of their organic carbon. These biochar-enriched soils store more water and nutrients while also making the water and nutrients more accessible to plants, according to studies conducted over the last ten years.

It is possible to make the biochar itself, which is used to enhance soil quality, from either agricultural or wood byproducts. The secret is to heat the substance to a high temperature in an atmosphere devoid of oxygen.  This process is called pyrolysis.

To do this, native farmers in pre-Columbian South America buried these materials in pits, set them ablaze, and left them to burn for days. Today, however, thousands of DIY tutorials on YouTube demonstrate how to manufacture biochar in a matter of hours using items like steel drums.

There is a growing interest in the production of biochar for a variety of reasons, including its ability to increase soil fertility. Some people are motivated to produce it by the desire to lower atmospheric carbon dioxide. This is due to the fact that biochar has the ability to store approximately 50% of the carbon that would otherwise be released into the atmosphere from wood chips, corn stalks, and other biomass for thousands of years.

Due to their low fertility, deforested soils in the Amazon are often only productive for a relatively short period of time. As a result, farmers must continually relocate to new locations and clear more Amazonian forest, which leads to escalating deforestation.

Because of the high concentration of porous carbon, microbial life, and organic matter, biochar “terra preta” soil is less susceptible to nutrient loss caused by severe rains and floods than unimproved Amazon soil. 

What are the key benefits of “Horticultural Charcoal”?

1.     pH modification

Biochar increases the pH of acidic soils largely due to its alkaline nature. As a result, nutrients and mineral fertilizers are more readily available and more effectively used. Research is being done to determine how Biochar affects the pH of alkaline soils.

2.     Increase in soil Cation Exchange Capacity (CEC)

Biochar is slightly negatively charged and has a high surface area to volume ratio. This improves soil fertility and Cation Exchange Capacity (CEC) by retaining positively charged cations in the soil. This leads to an increase in nutrient retention and a decrease in leaching of nutrients from the soil. The use of biochar can mean the difference between subsistence farming and productive farming in the hot, humid tropics, where organic matter decomposes quickly, and sandy soils are easily drained by heavy rain.

3.     Biochar enriches the soil with nutrients

This is dependent on the methods employed to create it and the nutrients included in the “feedstock” materials. Biochar should be analyzed for its nutrient content before use because it is quite variable and Biochar applications typically take up a lot of space. It’s important to understand the macro- and micro-nutrients in biochar prior to adding it to the soil.

4.     Increasing the soil’s ability to hold water

According to studies, adding biochar to soils can significantly improve their ability to retain water and making the water available to roots. This is caused by the biochar’s large surface area and porosity. Increased water-holding capacity in the soil can assist in higher agricultural yields and less irrigation.

5.     Augmentation of soil carbon content

Up to 80% of biochar is a stable carbon. It increases the soil’s carbon content and C:N ratio when added. The pyrolysis process and the feedstock’s carbon content have the biggest impacts on the biochar’s carbon percentage. Beware! Without proper study and planning, adding a lot of carbon to the soil might result in a very high C:N ratio, which has the opposite impact on crop yields, nutrient lockup, and yellowing of the crops.

6.     Increase in soil microbial activity and diversity 

Due to the high porosity of the biochar and its ability to hold both water and nutrients, it protects beneficial soil bacteria and ensures their survival during dry and fallow periods. For some microorganisms, the nutrients held within the biochar pores can also provide a sufficient energy source. Plants benefit from increased microbial activity in a variety of ways, including greater nutrient recycling, decreased leaching, increased nutrient availability, collection of nitrogen from the atmosphere, retention and addition of carbon in the soil, and a decrease in pests and diseases. This reduces the need for synthetic fertilizers and pesticides, with positive effects on the economy and the environment.

7.     Decrease of soil contaminants through bioremediation

Toxins and pesticide residues are broken down by increased microbial activity in the soil. Certain pesticides are “chelated” by biochar, which renders them inactive so that bacteria can consume them.

8.     Improving soil structure

In soil treated with biochar, there is an increase in CEC, microbial, and root activity, which aids in the formation of soil aggregates and a more durable permeable physical structure. This improves water infiltration and storage, which is beneficial for drought mitigation. Improved nitrogen exchange and root growth are facilitated by a porous soil that allows for better gas exchange, including the movement of carbon dioxide out and oxygen and nitrogen in.

9.     Reduction of agricultural pollution

Increased nutrient retention leads to less fertilizer and chemical leakage into groundwater. Pesticides are rendered inactive by increased microbial activity and chelation. Runoff and erosion decrease as the physical structure of the soil is improved. The risk of agricultural pollution is significantly reduced by a general reduction in fertilizer and chemical use.

10.  Carbon sequestration

By converting biomass to biochar, up to 50% of the original carbon can be stored in the soil for hundreds of years in a stable form that is resistant to breakdown; the remaining 50% can be used for energy and food. On the other hand, burning biomass only sequesters 3% of carbon, and biological breakdown only accounts for 20%.

Therefore, agricultural soils have a tremendous potential to sequester carbon, which would benefit the soils. The value of biochar as a source of carbon credits is hotly debated, but there are certain important considerations. Carbon credits are awarded when you remove or prevent greenhouse gases, like carbon dioxide, from being emitted into the atmosphere.  Another way to look at it is that carbon negative systems place more carbon in a stable solid form, like biochar, than carbon being emitted in the atmosphere as greenhouse gases.  A carbon negative system is produced by converting agricultural or wood waste that would otherwise be burned or composted into biochar using pyrolysis. Clear cutting forests specifically to produce biochar is not considered a carbon negative system. Using the waste wood from sustainably harvested trees as the feedstock to create biochar is a carbon negative system.

The Bottom Line about Using BioChar as a Soil Amendment

When it comes to understanding soil health, research shows that biochar is beneficial for numerous environmental concerns, including supporting plant growth (and thereby improving food security in developing nations), lowering soil erosion, lessening the effects of deforestation, and preventing groundwater pollution by improving nutrient retention. A number of soil remediation studies have also shown how using biochar can help rebuild forests and croplands that have been destroyed by human use.

Wakefield BioChar has a wide range of products for use in different environments and for various target results. We recommend utilizing biochar responsibly and sustainably from renewable carbon sources. When introducing biochar, or horticultural charcoal, as a soil amendment, consider both the characteristics of the biochar and the soil.