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What Is Biochar & How To Use It In The Cannabis Garden?

January 13, 2022

If you're a grower who wants fertile soil for your plants, biochar can help. It’s not a new idea, but it’s growing in popularity. According to agricultural experts, cultivators in Brazil have used this organic matter to develop and maintain soil health for over 2,000 years.

What is biochar? Discover how it can benefit you as a cultivator. We’ll explain the production process and show you how to make it at home. If you prefer to buy biochar, find out which are the best brands on the market. 

Biochar in soil

What is biochar?

‘Biomass charcoal’ or biochar is an organic matter produced by anaerobic (without oxygen) biomass pyrolysis and used to improve soil conditions. Research shows that it can also stabilize carbon levels, reduce the mineral’s solidification, and increase water and nutrient retention and biological activity in the earth.

You can find it in the form of black powder or lumps, which is why it’s known as Terra Preta de Indio, meaning “Indian black earth.” The substance contains 70% carbon and 30% other elements, such as nitrogen, hydrogen, and oxygen.

Not all biochars are the same. The type of organic matter you get depends on the feedstock and temperatures used in the pyrolysis. Producers use agricultural remnants such as wood, crop residues, and manure as biomass. Each feedstock type creates biochars with different nutrient and physical properties that interact distinctly with various soil types.

Use only clean biomass and avoid materials that may contain toxins, such as those taken from polluted areas. Contamination from heavy metals like lead, copper, mercury, zinc, nickel, and arsenic can drastically increase the soil’s pH level during the application. This condition can prevent your plants from absorbing soil minerals.

The other factor that can influence the results of your biochar soil amendment process is heat. A study found that: 

  • When you use it processed at low heat in your soil, you’ll see more immediate results in the first few years.
  • High-temperature organic matter stabilizes carbon levels in the longer term.

Biochar vs. charcoal

It’s common to find literature that describes biochar as charcoal. Although the production method is similar, and both substances are carbon-rich matter, there are several differences.

Here are ways in which biochar vs. charcoal are unique:

  • The former is more porous than the latter.
  • While both are products of pyrolysis and use biomass, wood is the feedstock for making charcoal, while the agricultural residue is for it.
  • People generally use charcoal for heating or cooking, especially barbequing.
  • Biochar is mainly for cultivation use and added to soil to improve its water and nutrient retention.
  • The heat producers apply to make it is approximately 500°C anaerobically, while for charcoal, it’s 1000°C..

What does biochar do for soil?

There are many biochar benefits when it comes to growing cannabis. Researchers propose using this organic matter to enhance soil health and address its growing degradation problem.

Biochar may help improve soil quality by:

  • improving soil structure;
  • increasing nutrient and water retention;
  • promoting microbial activity;
  • reducing acidity;
  • decreasing nitrous oxide emissions;
  • improving porosity;
  • managing nitrogen leaching;
  • boosting electrical conductivity.

You can add it to your compost as it prevents nutrient loss and lowers the release of greenhouse gases. It also speeds up the composting process by increasing microbial activity and reducing ammonia loss and odor.

There are many ways of preparing and applying biochar to the soil. The application depends on your earth’s condition and the biomass used to produce the substance. Evaluate the health of your grow medium and its nutrient content before using it.

We recommend you make biochar fertilizer by mixing it with compost or other organic matter to add nutrients and beneficial organisms to it.


Applications of biochar 

There are many applications of biochar besides soil enhancement, such as:

Biochar in animal farming

Animal farming in Europe uses as much as 90% of the total biochar. When used for the following purposes, there’s reduced odor:

  • Feeding
  • Litter
  • Slurry treatment 

The results are noticeable quicker compared to using it to treat the soil.

When farmers used the substance as a feed supplement, they noticed the following effects:

  • The animals were calmer
  • They ate more
  • Their allergies went away
  • There were fewer occurrences of diarrhea 

Biochar as a soil conditioner

By applying it to poor soil, the substance increases its water retention capacity and aerates it. Raising the soil pH also improves the release of nutrients. 

When mixing the organic matter with compost, you get a biochar fertilizer as effective as store-bought ones that doesn’t negatively affect the environment. It prevents nutrient leaching, which provides plants adequate supply whenever they need it.

Organic chemicals, by-products of biochar production, may stimulate your cannabis plant’s internal immune system, increasing its resistance to pathogens.

Biochar as construction material

This organic matter is an ideal material for building insulation because it has very low heat conductivity. It can also absorb six times as much water as its weight. When you add it to clay or replace sand in lime and cement mortars, you get indoor plasters that:

  • Offer excellent insulation and can maintain room humidity levels at 45–70% during summer and winter.
  • Can absorb odors and toxins, according to an Ithaka Institute study.
  • Can prevent ‘electrosmog’ because it absorbs electromagnetic radiation.

Biochar as a decontaminant

Other biochar uses include:

  • Cleaning contaminated wastewater containing heavy metals.
  • Forming barriers that prevent pesticides from seeping into surface water.
  • Treating water by adsorbing chemicals and improving water aeration.

7 biochar benefits

Let’s now explore the many biochar benefits that can help you as a cultivator:

1. Improves soil fertility

Biochar has an innate ability to enhance soil quality. Its effect doubles when mixed with fertilizers.

The substance also prevents nutrient-leaching, which improves mineral availability for the plant’s absorption. This benefit reduces the need for fertilizers to enhance marijuana crop growth.

Using biochar can reduce acidity and revitalize soil badly affected by poor cultivation methods or overuse of fertilizer or pesticides.

2. Promotes microorganism growth

Biochar acts as a breeding ground for beneficial microbes that are essential for your cannabis plant’s growth. These microorganisms make nutrients more bioavailable and easy for your crop to absorb and ward off invasive pathogens.

3. Retains water and nutrients

Due to its large surface area, biochar enhances the soil’s water retention by about 200%. Its negative-charge ions attract positively-charged minerals that are vital for marijuana plant development. These nutrients include sodium (Na), magnesium (Mg), potassium (K), and calcium (Ca).

Biochar for cannabis
Biochar for cannabis

4. Wards off pests

When you add biochar into your cannabis grow area, its charred odor makes it unappealing to pests. It’s an effective insect deterrent.

5. Stores carbon in the soil

One of the many biochar benefits is its ability to minimize carbon dioxide (CO2) in the atmosphere by stabilizing the biomass carbon and storing it. When you add the substance to the soil, it forms a carbon sink which keeps the element in the ground for centuries.

Decomposition of agriculture residue releases massive quantities of CO2 into the atmosphere, causing global warming. Converting the gas into biochar minimizes greenhouse gases emission, which helps the environment. For instance, producing a ton of biochar removes almost 2–3 tons of CO2 from the atmosphere.

6. Decontaminates groundwater

As studies show, biochar’s ability to trap water contaminants in its porous surface is exceptional. This quality makes it potentially effective in cleaning groundwater and reducing water filtration costs.

7. An alternative source of renewable energy

When you produce biochar, you get clean and renewable energy as a byproduct, which is an excellent alternative to burning fossil fuel sources. Replacing non-renewable energy sources can slow down the progress of global warming.

3 disadvantages of biochar

Although the substance has many benefits, there are several disadvantages of biochar to consider. These drawbacks usually occur when the substance is overused or overproduced. Moderation is key.

1. Lower yields

Due to its ability to absorb nutrients and water, excessive use of biochar can deprive the soil of those elements and reduce their availability to your cannabis plant. Lack of hydration and nutrition can adversely affect your crop’s growth and bud production.

2. Source of contaminants

It’s vital to use clean biomass in biochar production. Using contaminated materials will produce biochar with impurities such as heavy metals and toxic compounds. When you add the tainted organic matter to the soil, it can harm your cannabis crops over a long period.

3. Health risks

Besides irritating your eyes and skin due to lengthy exposure, excessive inhalation of biochar ash can cause respiratory problems. Be sure to take precautionary measures when handling the substance.


How much biochar do you add to the soil? 

How much biochar do you add to the soil? It depends on the condition of your soil. If it’s very poor, start with an equal mix of biochar and compost. Experienced users suggest ¼ lbs of the mixture per square foot.

Generally, the rule of thumb is the amount of the substance should be 10% of your cannabis cultivation area. Avoid applying excessive quantities of biochar because of the adverse effects, such as over-retention of water which can deprive your marijuana crop of nutrients.


How is biochar made?

How is biochar made? Make the substance by heating biomass with little or no oxygen present—a process called pyrolysis. Use only organic materials as feedstock as items with contaminants can produce char that’s potentially harmful to your marijuana plants.

The temperatures you use in making biochar will also determine the resulting organic matter type. The variety created by low heat is better for immediate outcomes, while those produced in high temps have a longer-term effect on your soil.


How to make biochar at home?

If you’re interested in how to make it at home, consider these ideas. They don’t require expensive equipment and are simple to execute.

Trench method 

Start by digging a trench in your garden. Some users of this option create a cone-shaped pit with the upper portion wider than the bottom. 

The next step in biochar production is to put some brush in and light it. Add more biomass as the fire rises. Observe the color of the smoke to know the progress. At the earlier stage, you’ll notice white fumes caused by water vapor.

As the sugars and resins burn when making biochar at home, your fire will emit yellow smoke. Wait till it turns grayish-blue, then smother the flames with about an inch of dirt or sand to reduce the oxygen supply. Leave it to smolder until you get chunks of charcoal. Put out the fire.

Barrel method

An alternative biochar production method is to burn wood pieces in metal drums. Many producers use two barrels, one smaller in size, that you insert into the larger container.

Place the material you want to turn into biochar into the inner drum and insert wood around it that you will burn. The heat will convert the matter in the smaller vessel into lumps of carbon. Cover the large barrel to reduce the oxygen supply.


How to activate biochar?

Let’s learn how to activate biochar. When the substance is made, it doesn’t contain any beneficial microorganisms, organic matter, or nutrients. 

Before applying it to your soil, you must activate or charge it with high levels of essential compounds, such as nitrogen (N) and phosphorus (P). This process is vital to enable microbes to form and develop in the biochar for quick results. 

There’s limited scientific research on which method is suitable with different soil conditions, but these are the four ways to activate biochar:

Mix with nutrient-rich matter

Before you apply it to your soil, you should charge it by mixing it with organic fertilizer, garden compost, worm castings, and water. You can also add urine or aged animal manure. 

This process allows the substance to soak up the nutrients and microorganisms from these materials and not from the ground you add it to. If biochar does the latter, it can reduce instead of improve soil fertility.

The most common ratio is 50% biochar to 50% compost and other materials. After mixing, let it rest for about ten days to give the substance sufficient time to absorb the nutrients and microbes before applying it.

Apply it into a compost pile

Add biochar to an active compost pile. Using this charging process, it takes longer for the microbial activity to happen. Depending on climate conditions and the quality of the composting materials, it can take weeks or months.

Make sure that the compost compounds don’t contain insecticides, fungicides, antibiotics, or harmful pathogens. You don’t want to risk transferring these contaminants to your soil.

Add biochar to farm animal habitats

Spread pure biochar in chicken coops and barns so that it can mix naturally with animal waste. The process length depends on the size of the area and the number of animals in the enclosure.

Ensure that the animals are free of antibiotics and other pharmaceuticals that can contaminate the end product.

Incorporating with commercial fertilizers

Another way to make activated biochar is by mixing it with commercially-available fertilizers. Most products contain the proper ratio and amount of nutrients and microbes, so you get an optimum blend to use in your soil. 

It’s best to use organic or natural fertilizers rather than synthetic ones.


5 best biochar brands

Although DIY biochar works, it may not be something everyone wants to do. The next best option would be to buy the substance. To ensure you get quality products, choose to buy only from reputable manufacturers.

Here are our 5 best biochar brands to help you in your selection:

Green Texan Organic Farms Biochar Soil Amendment

Green Texan Organic Farms’ biochar is specially made to improve soil structure and drainage. It’s available in chunks, fine powder, or bulk form.

What makes the product unique is the mix of EM-1® (Effective Microorganisms®) microbial inoculants. The world-renowned additive, developed in Japan, has natural microorganisms, such as yeast, lactic acid bacteria, and photosynthetic bacteria that enhance soil health.

Using this biochar offers lower risks of respiratory problems because it’s certified low-dust. You can buy a 2.5-gallon pack for around $18.

Wakefield Premium Biochar Soil Conditioner

This Premium Biochar Soil Conditioner is one of the highest quality biochars on the market. It’s made through a fast pyrolysis process, using biomass that’s 100% soft pine wood, which guarantees that it’s contaminant-free.

Wakefield’s satisfied customers tout the product’s effectiveness in increasing yields and removing odors in their cannabis grow room. If you want 1mm to 2mm fine granules of biochar, you can get a 7.5-gallon Premium Biochar Soil Conditioner box for just over $40.

California’s Greenest Low-Dust Biochar Box

Another biochar that’s organic comes from California’s Greenest. As the name suggests, the product contains low-dust char. The Organic Materials Review Institute (OMRI) certifies that it’s 100% organic because the pyrolyzing process uses naturally and sustainably grown recycled wood and tree trimmings.

California’s Greenest also guarantees that the biomass materials are free from pollutants. Users claim that enriching soil with this biochar produces healthier, pest-resistant cannabis plants. A 7.5-gallon box sells for less than $40.

Organic Mechanics Garden Center Biochar Blend

Organic Mechanics boasts that their biochar is organic because they use natural materials, such as compost, kelp, and worm castings in the pyrolyzing process. These substances combine to create a product rich in essential nutrients, including phosphorus, calcium, and azomite, which help nourish marijuana plants.

Using this biochar results in robust, disease-resistant, and fast-growing plants. Get this biochar blend at around $45 per 20 gallons.

Soil Reef Gardeners Blend

This Gardeners Blend product is a mixture of 50% biochar and high-quality organic compost, kelp meal, and worm castings. The production process uses wood waste and forest residue to make this char.

As it’s an all-natural product that provides your cannabis crops with essential growth nutrients, you don’t have to add fertilizers to your soil. 7.5 gallons of the Gardeners Blend biochar costs under $50.

Biomass charcoal
Biomass charcoal

Biochar - the key to better cannabis growth

If you want healthier marijuana plants and abundant yields, improve your soil health with activated biochar. Its effects last a long time if you apply this organic matter properly. Remember that excessive use can lead to detrimental results.

You can make biochar at home or buy it, so there’s no reason not to use it. You’re also saving the environment. Check out more articles for hacks on improving your grow medium. If you’ve found this information useful, please share it with your social media channels.

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.

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