What is biochar? Several questions have come my way in the past few weeks about biochar. How is it used in the garden and landscape? What is biochar? Where do you get biochar? Can you make biochar? I decided it was time to take a deeper look at biochar for myself.
What is it?
Basically, biochar is charcoal. Technically, biochar is carbon, the same thing as the common charcoal you burn in your grill. The commonality ends there. True biochar is produced using very specific processes called pyrolysis to reduce biomass (things like wood chips, green material, etc.) while reducing both eternal and internal contamination. True pyrolysis produces a form of carbon called biochar, which has some interesting characteristics.
Biochar is characterized by its highly porous, lightweight, and fine-grained texture. It is composed of approximately 70% carbon. The balance of its composition is nitrogen, hydrogen, and oxygen. The rations of the elements are highly dependent on the biomass used to make the biochar and the processes used to create it.
One of the characteristics that interest gardeners and farmers most is the highly structured porosity of biochar. The carbon forms lattice-like structures, creating billions of microscopic pores within the structure of the biochar mass. When biochar is incorporated into the soil, these lattice structures provide a labyrinth of channels for water infiltration and retention and massive surfaces for the organisms of the soil biome to grow.
Estimates are that a one cubic inch block of biochar unfolded to expose its complete surface area would cover a football field.
The other characteristic of biochar that creates a stir among climatologists is the ability of biochar to sequester carbon and store it for long periods. Many researchers believe that carbon in the form of biochar, introduced into the soil, can sequester or store that carbon for decades if not hundreds of years. While research is still ongoing, there are indications that using biochar has significant potential to address rising CO2 levels in the atmosphere.
As a soil amendment, biochar offers many possibilities. One of the most intriguing is the use of biochar to remediate damaged soil, especially soil that has long histories of chemical pesticide, herbicide, and fertilizer exposure. Carbon is well known for its ability to attract and hold on to a wide number of potentially toxic elements and compounds. This makes biochar useful in remediating soil contaminated by years of exposure to synthetic chemical treatments.
As mentioned earlier, biochar’s structure creates space that allows water infiltration and bacteria growth in the soil. The addition of biochar to your soul can dramatically affect water infiltration rates.
One downside is the tendency of biochar to raise the pH of the soil to which it is added. In acidic soils, those with low pH may not be a problem. However, if your soil is already high in pH, care should be taken in adding biochar.
Biochar can be used effectively to improve soil quality by:
- Enhancing soil structure
- Increased water retention
- Increased soil aggregation
- Decreasing acidity
- Improving porosity
- Improving microbial properties.
Using Biochar in your Landscape
In a small garden or urban landscape application, biochar is best mixed with other materials such as compost. The rates of application will depend in large part on the current condition of your soil. There are some excellent resources on the internet with guidelines for using biochar. They can be found at the International Biochar Initiative and Wakefield Biochar.
The Environmental Aspect
From an environmental aspect, biochar is attractive as a partial solution to a variety of global problems. The process of making biochar has the potential to sequester millions of tons of carbon annually. When used in landscape, gardening, and farming applications, this carbon can be held in the soil for years.
The production of biochar also produces clean and renewable energy as a byproduct. The gasses produced during the pyrolysis process can be collected and burned, reducing the need for the input of additional fossil fuels in the process.
Groundwater also benefits from biochar in the soil. Water percolating through the soil with high concentrations of biochar reaches a higher quality in the aquifers due to the carbon action scrubbing pollutants from the water as it infiltrates downward.
The Darker Side
There are potential drawbacks. One of the greatest is the possibility of bringing contaminants into your soil. Contamination can occur if the biomass used to produce the biochar was heavily contaminated. Such things as heavy metals and VOCs can remain in the biochar after the pyrolysis proves.
Soil pH can be adversely affected if your soil is normally alkaline, with a high pH< adding biochar may drive the pH even higher and into ranges that plants cannot tolerate.
Quality control can also be an issue. As of the writing of this article, there are no universal standards or quality controls on the manufacture and sale of biochar. A lack of standards often makes it hard to be sure of what you are getting, its origins, and it’s content.
Some research has concluded that biochar can, under particular circumstances, inhibit seed germination and may reduce crop yields where the sorption of water by the biochar reduces the availability of moisture. This reduction in moisture can also inhibit the transfer of soluble nutrients.
Spreading biochar on a large scale can create health hazards due to the dust created by the process.
Research is still ongoing, but real-life experiences have proved dramatic changes in soil health and fertility. We are not making any recommendations on the use of biochar in landscapes and gardens. We encourage you to do your research and make your own decisions.
For more information about soil building, soil amendments, and soil biology, visit our website at West Texas Organic Gardening.
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