By Sam Bennett, Gardens of Fire
This is the second article in our series on biochar. The previous blog post titled Biochar… a win/win/win opportunity? focused on its benefits for tree farmers. Carl Struck discussed the background, potential, and necessity of biochar, particularly as a waste recycling solution that creates a valuable long-term soil amendment. He also outlined accessible, low-tech methods for getting started with biochar production. But once you’ve made your first batch, what’s next? Should it be used raw, or does it need to be “activated”—charged or fertilized—before application?
Today, we will discuss what to do with biochar after production and why activation is a crucial step in the process. Biochar is easy to make, but a gardener or farmer will still need to get it ready for soil application. Luckily, with a good strategy in place, that charging process can take biochar from average to awesome.
The Science Behind Charging Biochar
Why is charging biochar so important? Uncharged or “raw” biochar, composed primarily of recalcitrant carbon, acts like a dry, rigid sponge: it can hold water and it can also absorb dissolved nutrients. In the soil, both water and nutrients are essential for plant and microbial health. If you apply raw biochar, it will initially absorb any excess moisture and free-floating nutrients that are in the surrounding soil, potentially depleting plants of what they need and setting back our growth goals.
To prevent this, we first saturate biochar with both water and nutrients—using a compost tea, for example—before introducing it into the soil. Once properly primed, biochar becomes a slow-release reservoir of nutrients rather than a nutrient sink that competes with plants.
When and How to Charge Biochar?
For immediate or same-season use, charging biochar is recommended for best results. If your goal is to enhance plant growth or soil fertility quickly, biochar should be charged or fertilized before application in the field. However, if you’re regenerating fallow land that won’t be in production for at least two years, applying raw biochar can still be beneficial.
The International Biochar Initiative suggests a charging period of 1–3 weeks. One of the simplest ways to do this is by mixing biochar into a finished or active compost pile and allowing it to sit. A well-maintained compost pile—properly watered and periodically turned—can shorten this timeframe. If you’re new to biochar, consider extending the charging period by an extra week to ensure optimal results.
Alternative Methods for Livestock Farmers
For farmers with livestock, there are additional ways to charge biochar while maximizing its benefits. Adding raw biochar to deep mulch composting systems or livestock bedding—such as in chicken coops—can help reduce odors, create healthier living conditions for animals, and enhance biochar’s nutrient profile. This approach passively infuses biochar with natural fertilizers, making it a valuable and cost-effective amendment for soil health.
Biochar production: quenching to stop the burning process. Photo by Isabelle Jenniches BY-NC 4.0
A Pro Tip from Albert Bates
Biochar researcher and author Albert Bates recommends a highly effective method for charging biochar: using compost tea during the quenching phase immediately after production. The key to this technique is timing. While water should be used initially to reduce extreme heat, introducing compost tea directly after quenching ensures that the biochar’s internal pores are filled with beneficial microbes and nutrients. Since raw biochar’s microscopic chambers act like vacuums after production, they readily absorb whatever they come into contact with first. Using compost tea at this critical moment maximizes biochar’s ability to retain and gradually release nutrients while shortening the charging phase.
However, if you miss this window, don’t worry—biochar can still be charged through traditional composting methods, it will just take a little longer. Choose the approach that best fits your workflow, production schedule and budget.
Biochar Under the Microscope: Take a look at these long tubular chambers. Notice the size variation of the small and large ones. These long passageways are all soft before pyrolysis, and through heat and pressure (and lack of oxygen), they stiffen and harden. This creates an almost endless maze of passageways for microbes and nutrients to be safely stored in.
Photo credit: Brownsort, UK Biochar Research Centre
Spreading Knowledge and Hands-On Learning
As biochar gains popularity, it’s essential to bridge the gap between theory and practical application. Many farmers and gardeners may struggle to translate new information into actionable steps—that’s why community knowledge-sharing spaces are vital.
To support this, we’re hosting a field day in conjunction with the Permaculture Picnic at Tico Time Resort in Aztec, New Mexico. At the event, participants can engage in hands-on learning about biochar and how to charge it. We’ll cover beginner and farm-scale biochar production methods in a collaborative setting. You’ll be amazed at how much biochar we can produce! After spreading blended biochar in the Permaculture Picnic garden we’ll share Tico Time blended biochar (mixed with compost) with participants. Come join us as we explore these techniques together!
Jeff Hood
Thanks for this. I’ve been experimenting with different charging methods. And wondering if you have tried soaking raw biochar in urine? Using has most of the nutrients plants need and seems like it should absorb quickly in the charcoal. Any thoughts?
Kelpie Wilson
Urine is the best thing you could soak biochar in. So many benefits. Just do it!