---
title: Biochar in a terrarium | Glass Jar Garden
description: Biochar: Crushed charcoal that traps impurities and gives helpful microbes a home. In the jar it has holds water 37.5 % by volume, pore space 77.5 % by...
url: https://glassjar.garden/guide/soils/biochar/
---

Soils and layers

# Biochar

Crushed charcoal that traps impurities and gives helpful microbes a home.

## What the simulation uses

- Holds water: 37.5 % by volume (Water it keeps after draining; the rest runs down to the drainage.)

- Pore space: 77.5 % by volume (Room for air and water between grains; low means roots suffocate when wet.)

- Weight: 275 g/L (How heavy a litre is.)

- pH: 7 to 9 pH (How acid it keeps the soil.)

- Mould risk: none (How much fresh food it gives white mould; high-risk soils fuzz over in the first weeks.)

- Nutrients: low (Plant food it brings.)

- Presses down to: 97 % of its loose depth (How far pressing can pack it, keeping its weight.)

## Description
Crushed charcoal that traps impurities and gives helpful microbes a home. It never breaks down and raises pH slightly. Use it as a filter layer or mixed into soil.

Also called charcoal fines.

Estimated, where sources were thin: values estimated from hobby and horticultural references; not measured.

[Grow it in a jar](https://glassjar.garden/?guide=soils/biochar)

[Bagged potting soil](https://glassjar.garden/guide/soils/potting-soil/) · [Black sand](https://glassjar.garden/guide/soils/black-sand/) · [All soils and layers](https://glassjar.garden/guide/soils/)