You’ve probably heard of biochar, and thought it sounded like a good thing. But you may not have realized how easy it is to convert burn piles to biochar production with a couple of simple changes. Your biochar burn will give off much less smoke and ash, and leave you with an excellent soil amendment. And it will sequester about ten percent of the carbon your burn pile releases. Want to try it?
How to Make Biochar in Your Burn Pile
First, get your burn permit, same as for any burn pile, and observe all the rules: burn on a burn day with shovel and water handy.- Build your pile using dry and uniformly sized material; burn big wood separately from brush.
- Two changes are then required: light the pile at the top, and put it out when it switches from flame to smolder. You’re probably thinking, “Light at the top – how can that be right?” It’s completely counterintuitive, but you’ll see that it works. What’s happening is as the initial flames begin to heat the wood nearby, volatile gases arise and are consumed in flames. The fire will sink and spread through the pile, burning through the volatile gases. It won’t burn the residual charcoal as long as flames are consuming all the available oxygen.
The tipping point comes when the flames die down and the pile begins to smolder, at which time you drown it with water.- Continued burning will turn the coals to ash. If you’re working out in the woods without access to water, break up and spread the pile so the embers lose their heat, taking care that it’s all out before you leave.
- Once it’s dry, you can process it for garden use. The most effective particle size is 1/4” or less. Material that’s completely cooked will break up easily. Some might have to be held over for reburning in the next fire. Mashing with a stout limb in a bucket works great. You can make a sifting frame with 1/4” hardware cloth and scrap lumber.
TIP: Wear a mask. Biochar dust is an irritant to the lungs; you want to avoid breathing it. An N95 mask gives good protection, and so does keeping the char a little damp. All the nutrients have been gassed off biochar, so it’s inert and very stable. It can last for hundreds or thousands of years—remember how carbon-14 is used to date ancient campfires? It will continue to sequester the carbon it contains the whole time. - Now you have finished char. For best results in the garden, you’ll want to pre-charge it with nutrients. Otherwise it will draw nutrients out of the soil to reach a balance. Simply adding it into your compost pile is the easiest way. A faster approach is soaking it in manure tea or compost tea. If you’re not a gardener, you can just leave it in the woods after your fire is out, and call it good. It will gradually be integrated into the soil, just like charcoal from a wildfire.