Simple & Effective Method of Biochar Production

Categories: Green

Biochar is charcoal used as a soil amendment. Like most charcoal, biochar is made from biomass via pyrolysis. Biochar is under investigation as an approach to carbon sequestration to produce negative carbon dioxide emissions.

Biochar is a fascinating substance. When properly made and inoculated it can have profound effects on soil health and fertility.

Biochar’s immense surface area and electrical properties make it a particularly valuable amendment for increasing soil tilth, nutrient retention, water retention and cation exchange capacity (CEC). It also boosts populations of beneficial bacteria and fungi in the soil.

Biochar can remain in soil for hundreds or even thousands of years, as evidenced by the terra preta soils in the Amazon Basin. This anthropogenic pyrogenic soil carbon created oases of fertility in the shallow, leaching, infertile soils typical of the region.

Charles C. Mann wrote of terra preta soils in his bestselling book 1491: New Revelations of the Americas Before Columbus:

Amazonian Indians literally created the ground beneath their feet … in the 1990s researchers began studying these unusual regions of terra preta do Índio—rich, fertile “Indian dark earth” that anthropologists believe was made by human beings…

Throughout Amazonia, farmers prize terra preta for its great productivity; some have worked it for years with minimal fertilization. Among them are the owners of the papaya orchard I visited, who have happily grown crops on their terra preta for two decades. More surprising still, the ceramics in the farm’s terra preta indicate that the soil has retained its nutrients for as much as a millennium. On a local level, terra preta is valuable enough for locals to dig it up and sell as potting soil, an activity that, alas, has already destroyed countless artifacts…

Because terra preta is subject to the same punishing conditions as the surrounding bad soils, “its existence is very surprising,” according to Bruno Glaser, a chemist at the Institute of Soil Science and Soil Geography at the University of Bayreuth, Germany. “If you read the textbooks, it shouldn’t be there…”

As a rule, terra preta has more “plant-available” phosphorus, calcium, sulfur, and nitrogen than is common in the rain forest; it also has much more organic matter, better retains moisture and nutrients, and is not rapidly exhausted by agricultural use when managed well. The key to terra preta’s long-term fertility, Glaser says, is charcoal: terra preta contains up to sixty-four times more of it than surrounding red earth. Organic matter “sticks” to charcoal, rather than being washed away or attaching to other, non-available compounds…

“Over time, it partly oxidizes, which keeps providing sites for nutrients to bind to.” But simply mixing charcoal into the ground is not enough to create terra preta. Because charcoal contains few nutrients, Glaser argued, “high-nutrient inputs—excrement and waste such as turtle, fish, and animal bones—are necessary.” Special soil microorganisms are also likely to play a role in its persistent fertility, in the view of Janice Thies, a soil ecologist who is part of a Cornell University team studying terra preta. “There are indications that microbial biomass is higher in terra preta than in other forest soils,” she told me, which raises the possibility that scientists might be able to create a “package” of charcoal, nutrients, and microfauna that could be used to transform bad tropical soil into terra preta. Pg 344-346

Looking around the web for a simple method to produce useful amounts of biochar one can easily get discouraged by the many complicated and intensive methods of production.

After much time spent searching and piecing together information from various sources I learned of a method of biochar production that is simple, effective, cheap, reliable and fun.

This method does not involve any metal kilns, cans, retorts, bricks or concrete. It is the lowest barrier to entry method of biochar production that I know of.

This low tech method simply involves digging a cone-shaped hole in the ground and controlling the burn as you would if you were using a metal cone kiln like the Kon-Tiki.

It’s a great way to have a campfire too, as it is mostly smokeless.

I will explain the details along the way. Let’s get started.

You will need:

  • 2 nails or sharp sticks
  • String – at least 1.5ft
  • Shovel
  • Scrap wood for feedstock – untreated, about wrist diameter and smaller
  • Your preferred fire starter
  • Water source to quench OR metal sheet to smother coals OR just the dirt from the pit
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