Post #9B How to Make Biochar
Blog Description: How to make biochar at home, covering several low-tech, small-scale methods.
Hi there fellow zone 10 and 11 gardeners! If you found yourself here, excited to learn some simple methods for making biochar, but you are still unsure what biochar is exactly, check out my post, What is Biochar?, then come on back!
Or if you’d rather a quick review, read on to get going.
Biochar is a pure form of carbon made from dried and prepared biomass. It is considered an excellent amendment to any garden, especially gardens like ours in subtropical climates.
Biochar offers incredible surface area for beneficial microorganisms to live in, holds water to keep the soil moist, and draws in nutrients that can be slowly released back to your plants’ root systems instead of flushed out into the water table.
There are no large commercial enterprises making this stuff – at least not yet. Making it at home is fairly easy and can be done free of charge, or for a very small investment if you choose a method that requires more than a hole in the ground.
Okay, now that you know what biochar is and why you want to make it for your garden, let’s get to it!
Making Biochar at Home
An at-home biochar system is within reach. You may need to pick up a few easy to find items, or you may simply need to take an inventory of your garage or garden shed to find the right parts. There’s more than one right way to create an at-home system, so we’ll go over a few here.
Before we do, however, we would be remiss if we did not remind you (and ourselves) that we are playing with fire, and there are serious implications. Please be present, be careful, and be prepared.
- Do not leave the burn unattended!
- Have a hose ready nearby
- Prefill buckets of water
- Keep a fire extinguisher on hand
- Have a phone with a charged battery nearby in case you need the fire department!
- Pets should be put away and children should not be nearby
All that being said, if you follow along and pay attention, these are very safe methods with minimal risk.
Your setup can be as simple as digging a conical ditch, about 2 feet in diameter at the surface, then filling it with dry biomass such as twigs and branches. You can also use a large metal drum instead of digging a pit. Or you can purchase a biochar kiln or cone stove online.
No matter what method you use, the end result should be pure biochar IF you can achieve pyrolysis – heating and transforming biomass in the absence of oxygen.
To create an environment needed for pyrolysis, light the entire surface area of the top biomass. The flames will act as a barrier to keep oxygen from getting underneath.
Materials
- Dried and prepared Biomass (about 4 pounds will render 1 pound of biochar as a rule of thumb)
- 44 gallon cone drum or biochar kiln (also called a cone stove) if not using the pit method (see below)
- Metal rake or flat shovel
- Water source and attached hose
- Buckets of water (prefill)
Pit Method
Use this method for dry plant material such as twigs, branches, and split logs. In this method, the flames themselves deprive the biomass of oxygen, producing a smokeless burn.
- Dig a cone shaped pit, about 3 feet in diameter at the surface, coming to a point at about two feet deep.
- Using your smallest twigs, start a fire in the bottom of the pit and slowly add more twigs, followed by branches and logs as the fire grows.
- Allow the layers to burn evenly and produce a white ash before adding more wood each time.
- Once you reach the top of the cone and the top layer is covered in white ash, douse the fire with water.
- The remnants are your biochar.
Drum Method
Use this method for dry leaves and other woody biomass. You can alternately use a trench in this method, follow the same steps.
- Place all material in the drum or trench.
- Light the fire from the top down, so the flames begin and starve oxygen from the top.
- Once all the biomass is charred with a white ash on top, douse the fire with water.
- The remnants are your biochar.
Biochar Kiln
Use this method for any dry biomass materials. Also called a cone stove, these are available for purchase online. This method is not as efficient as the pit method, but you do not have to dig a pit in your yard to do it!
- Follow the same steps above for the drum method.
These are just a few common, modern ways to make biochar. There are so many more ways to do it. The main goal is to char in the absence of oxygen through pyrolysis, that is what makes biochar, well, biochar.
Activating and Using your Biochar
Once you’ve got your finished product, let it cool at least overnight. Now you’ve got a pile of pure carbon, and carbon likes to soak up anything around it.
So, if you add it to your garden beds without charging it, the biochar will draw all the water and nutrients out of your soil. Not good, right?
Instead, activate your biochar by tossing it in a big vat of compost tea and letting it sit for at least 10 days to soak up the water and nutrients that will make it a powerhouse for your soil. Learn how to make compost tea here.
Another method, if you have the time and you are not too anxious to get a bed planted, is to mix aged compost and biochar into existing soil in a bed. Let it sit for a season or two, then it will be pure black gold for your plants.
Let us know if you try making it, and what the results are! We are all here to share knowledge towards a common goal of a greener, healthier planet! What method did you use? One suggested here or did you try something different? Let us know, I love hearing from you!
Until next time,
Mary