Charcoal - Intro to Charcoal - Japan - ARI
by the Asian Rural Institute
page developed by Rina Tanaka, ARI Volunteer
submitted June 2021
Charcoal
for soil improvement
https://gyazo.com/8812553cc868fff5b267c98c9c8c6a44
Rice husk charcoal
What is charcoal?
Charcoal is made by burning plant materials (such as wood, bamboo, or rice husk) with a limited amount of oxygen so that the materials will mostly turn into carbon instead of CO2 (carbon dioxide). Charcoal is light and has many small pores (holes) which plays an important role in improving soil. (Note: charcoal is very similar to biochar, and the two terms are often used interchangeably.)
https://gyazo.com/bd2b957699b2d5a08711be03d20994ed
The porous structure of charcoal
Why do we use charcoal?
Charcoal is especially effective for soil improvement. Let's compare charcoal with ideal soil. https://gyazo.com/ef3029e78f8e918af8048b560653afcd
We can see that charcoal shares many characteristics with ideal soil. One notable difference between them is that charcoal is alkaline, while ideal soil is neutral.
Now, let's take a closer look at how charcoal can improve the soil.
Holds water well & maintains good drainage and aeration (Improvement of soil's physical quality)
Some amount of water stays in the small pores while the excess water passes through the big pores. This helps maintain an appropriate moisture level around the plant roots. The pores also provide space for air.
Provides living space for microorganisms (Improvement of soil's biological quality)
The pores in charcoal serve as comfortable compartments for microorganisms to live in, which helps promote biological activity in the soil. Note that charcoal alone does not provide complete food for soil organisms. Organisms feed on organic matter, using carbon (C) to produce energy and nitrogen (N) to build their bodies. Although charcoal is mostly made up of carbon, it does not have much nitrogen. A mixture of charcoal and organic matter rich in carbon and nitrogen can support the lives of organisms.
Neutralizes acidic soil (Improvement of soil's chemical quality)
Most plants grow well in neutral soil (pH of about 7). If the soil is acidic, charcoal can improve its soil quality since it is alkaline (pH 8-9). However, if the soil is already alkaline, charcoal might not be the best material for soil improvement.
Supplies minerals to the plants and holds nutrients (Improvement of soil's chemical quality)
Charcoal contains a lot of minerals such as water-soluble phosphorus (P), potassium (K), and calcium (Ca). Since its surface tends to be negatively charged, it also binds well with nutrients, which are mostly positively charged.
Is free from diseases, insects, and weed seeds
In the process of using fire to make charcoal, we can kill the pests living on the materials, so we do not have to worry about bringing pests to the field.
Absorbs heat from the sun
Because of its black color, charcoal can absorb sunlight efficiently and raise the temperature of the soil.
https://gyazo.com/66315c4315d5f31d89ccedc95bc74074
How do we use charcoal?
As an ingredient for bokashi
Charcoal provides living space for microorganisms that play an important role in the fermentation process of bokashi. As an ingredient for nursery soil
At ARI, we mix equal amounts of leaf compost, red soil, and rice husk charcoal to make nursery soil for the seedlings.
When transplanting seedlings
When transplanting a seedling from a nursery pot/bed to a field, we often put rice husk charcoal under the roots of the seedling along with bokashi and compost. For more details, please read the "How to use bokashi" section (bottom of the page) on this page. For livestock
Effective for preventing and treating diarrhea (Mix a handful of charcoal into feed)
Because of its pores, charcoal can absorb toxins and harmful microorganisms in an animal's digestive system before being excreted.
Absorbs bad smells, especially the smell of ammonia (Mix into the floor or the bedding)
Prevents coccidium among chickens (Mix into the floor or the bedding)
Coccidium is a type of parasite that can make chickens sick, particularly young chicks. Since it flourishes in wet places, charcoal can control them by removing moisture from the environment.
How do we make charcoal?
At ARI, we mostly use two types of charcoal: wood charcoal and rice husk charcoal. Although there are slight differences in their characteristics as you can see in the chart below, the main difference between them is the materials.
https://gyazo.com/b061be57cd95fbb347c5b38506c380f1
Comparison between wood charcoal and rice husk charcoal
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