How To Make Biochar In A Pit
, by Andrew Sun, 3 min reading time
Making biochar in a pit is a traditional and simple method using minimal equipment. During the burning process the bio-waste materials are completely exposed to air in an open fire environment, so it can produce biochar very quickly. The most time-consuming work is digging a proper pit. Here is a basic guide on how to make biochar using a pit method.
Materials Needed For Making Biochar In A Pit
- Big steel shovel, for digging
- Dry bio-waste, such as grass, corn cobs, wood chips, branches and leaves
- Water and water can
- Lighter or matches
- Biochar storage container
- Safety equipment like heat resistant gloves
Step 1: Digging the Pit
1. Find an open aired space, away from possible fire hazards where it's safe to burn and easy to dig a pit.
2. Use the shovel to dig a pit about 1 meter (3 feet) in diameter and 0.5 to 1 meter (1.5 to 3 feet) deep. The size can be adjusted based on the amount of biomass you have.
3. A cone-shaped pit (wider at the top and narrower at the bottom) is often recommended as it helps in managing the burning process more efficiently.
Step 2: Preparing the Biomass
1. Collect dry organic waste material such as grass, corn cobs, corn husks, wood scraps, branches, leaves, or agricultural waste.
2. Cut or break the big pieces into smaller pieces. This helps in ensuring the pit can hold as much biomass as possible as well as ensure all the biomass have a more uniform burn.
3. Make sure the easiest burning material like dry grass and thin branches are on the top, this helps start the burning process easily.
Step 3: Starting the Fire
1. Light the material from the top. This method, known as a top-lit updraft (TLUD), allows the fire to burn downwards, reducing the amount of smoke produced.
2. Make sure the fire burns evenly through out the entire. Adjust the fire, until all the corners start burning evenly.
Step 4: Managing the Burn
1. Keep an eye on the fire. The goal is to have a slow, smoldering burn rather than a fast, hot fire. This ensures the biomass enters proper pyrolysis in turn forming biochar rather than turning to ash.
2. You can control the burn rate by adding or removing material or by covering parts of the pit with metal sheets or soil to reduce oxygen flow.
Step 5: Quenching the Fire
1. Once the smoke thins out and the flames are lessening, it’s time to extinguish the fire. This stops the burning process and prevents the biochar from turning to ash.
2. Carefully douse the fire with water. Be prepared for a lot of hot steam, ensure you’re protected from the heat and steam.
3. Make sure the fire is extinguished completely.
Step 6: Harvesting the Biochar
1. Allow the biochar to cool down before handling.
2. Store the biochar in a dry place until you’re ready to use it.
Tips
1. The process may require some trial and error to perfect, based on your specific conditions and materials. Due to the fact that the pit is not a closed space but rather an open aired environment, the heat during the burning process cannot be controlled at optimal biochar production temperature, causing regulations in biochar production.
2. Always prioritize safety, especially when dealing with fire.
Making biochar in a pit is a straightforward way to recycle organic waste into a valuable soil amendment while sequestering carbon. However, it’s important to conduct this process responsibly and safely to minimize any potential risks.
