What is biochar?

Biochar is charcoal made with slow pyrolysis at 600 to 900°F (350 to 500°C) for use as a soil amendment. It can mean charcoal made for other uses as well, such as biofiltration, detoxification, and additives in asphalt and concrete.

What’s different about it?

Biochar has a vast surface area—about 300 square meters per gram—and it doesn't break down for hundreds of years or more. The carbon in it does not to the atmosphere, which helps to slow climate change.

What do you make it from?

What does it do in the soil?

Is there a downside to it?

How do you "charge" it?

Is all biochar the same?

Where can I get it?

Biochar can be made from any sort of biomass. Ideally you'd choose an excess of something, such as forest thinnings to reduce wildfire intensity.

Biochar retains nutrients and water, provides habitat for microorganisms, and sequesters carbon. It gradually increases soil carbon by promoting aggregation. As a result, it supercharges soil fertility.

Not really. Biochar does need to be "charged" with nutrients before amending soil with it, or else it depletes the soil for about one season. Soil that's already healthy might not appear to benefit from it. It's only as sustainable as the harvest of the biomass from which you make it.

Add biochar to your compost pile. Fast charging can be done with compost tea, worm castings, or urine, but it still takes a few days.

No. It varies according to combustion temperature, "residence time" (how long it was that hot), and what species it's made from. Quality can vary widely. Testing is available.

Biochar can be made by you from branches, wood, bamboo, or really any form of biomass. All it takes is burning the biomass until the flames go out and then extinguishing it completely. It can be made in a pile burn or in a kiln made specially for biochar. Or you can buy it from a manufacturer.