Adding biochar to compost brings two useful soil materials together. Compost supplies organic matter and nutrients. Biochar adds a porous structure that helps hold water and nutrients when the finished compost is mixed into soil.
The compost pile also helps prepare the biochar for garden use. As the pile breaks down, moisture, nutrients, and microbes move into the biochar’s pores. The finished blend is easy to spread through garden beds, raised beds, and planting areas.
Before You Begin
Gather your usual compost materials, biochar made for soil use, water, and a garden fork or compost turner. Use the application amount listed on the biochar package. Lightly moisten dusty biochar before handling it, and wear the protection recommended on the label.
Build a balanced compost pile
Start with a mix of green materials, such as fresh plant scraps, and brown materials, such as dry leaves or shredded cardboard. Break up large pieces so they can decompose more evenly.
Add biochar in thin layers
Sprinkle biochar across the pile as you add new compost materials. Follow the amount listed on the product label. Thin, even layers are easier to mix than one large pile of dry biochar.
Mix the materials
Turn the pile so the biochar is spread throughout the food scraps, yard waste, and other compost materials. Good mixing places the biochar in contact with the moisture and nutrients released during decomposition.
Maintain air and moisture
Keep the pile about as damp as a wrung-out sponge. Turn it often enough to bring air into the center. Add water when the pile is dry, or add dry brown material when it becomes wet and packed down.
Let the compost finish
Allow the pile to break down until the material is dark, crumbly, and earthy-smelling. Large scraps should no longer be easy to identify. Mix the finished compost and biochar blend into garden soil or use it as directed for your planting project.
Why Add Biochar to Compost?
Biochar’s porous surface gives water, nutrients, and soil microbes places to collect. Adding it during composting lets it become part of the active pile instead of remaining a separate dry material. The finished blend combines the organic matter in compost with the long-lasting structure of biochar.
Biochar can also help manage moisture and odors inside the pile. It does not replace the basic needs of composting, however. The pile still needs a useful mix of green and brown materials, enough moisture, and regular airflow.
Common Compost Problems
- The pile is dry: Add water a little at a time while turning the materials.
- The pile smells rotten: Turn it and mix in dry leaves, shredded cardboard, or another brown material.
- The pile is not changing: Break up large pieces, check the moisture, and add fresh green material if the pile contains mostly dry browns.
- Biochar collects in one area: Break up the pocket and mix it through the surrounding compost.
When the compost is ready, use the blend to add organic matter and biochar throughout the root zone. Follow the needs of the plants and the directions for the garden project where it will be used.
