Introduction
As Australian gardeners, we’re all feeling the effects of a changing climate, hotter summers, heavier downpours, and longer dry spells. Building resilient, living soils is one of the most powerful ways we can adapt.
One tool gaining attention from both scientists and gardeners is biochar, a form of charcoal made from organic material that can transform the way soils hold water, nutrients and carbon.
What is biochar?
Biochar is created when plant or organic matter (like woodchips, crop residues, or garden waste) is heated in a low-oxygen environment, a process known as pyrolysis.
Unlike ordinary charcoal, biochar is intended for soil. Its tiny pores and high surface area act like a sponge, improving soil structure and creating homes for beneficial microbes.
When added to soil, quality biochar can:
● Increase water-holding capacity and reduce watering frequency
● Improve nutrient retention and reduce leaching
● Support soil life and root development
● Store stable carbon for hundreds of years
Biochar Builds Drought-Resilient Soils
In sandy or degraded soils, biochar acts like a miniature water tank, absorbing and slowly releasing moisture back to plant roots. Trials in NSW and QLD have shown that biochar-amended soils can hold 20–30% more plant-available water, while improving aeration in heavier clays. When mixed with compost or organic fertilisers, it enhances microbial activity and keeps nutrients cycling even under heat or moisture stress.
Turning Waste into a Climate Solution
Every tonne of organic matter that decomposes or burns releases CO₂ back into the air.
By instead carbonising that waste into biochar and returning it to soil, gardeners create a carbon-negative cycle, locking carbon away while enriching their garden beds.
Biochar production can be scaled from home-made “Kon-Tiki” kilns or small pyrolysis units through to community composting hubs. Using local residues such as prunings, sawdust, or nutshells keeps carbon in the region and reduces landfill methane.
How to Use Biochar in Your Garden
- Charge it first: Mix biochar with compost, worm castings or liquid fertiliser for 1–2 weeks before applying. This allows the pores to absorb nutrients and microbes.
- Blend, don’t bury: Mix 5–10% biochar by volume into soil or potting mixes (roughly one part in ten).
- Plant normally: Water in well and mulch as usual. You may notice improved soil moisture and plant health over the following months.
Think long-term: Biochar doesn’t disappear, it keeps improving soil year after year.
Biochar and Climate-Positive Gardening
By using biochar, gardeners can:
- / Sequester up to 3 tonnes of CO₂-equivalent per tonne of char applied
- / Reduce fertiliser and water use
- / Improve soil biodiversity
- / Support circular economies by transforming local waste into long-lived carbon stores
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In this way, biochar isn’t just good for your garden, it’s good for the planet.
Choosing Sustainable Biochar
Look for:
- / Australian-made biochar produced under clean, low-emission conditions
- / Analysis that meets the ANZ Biochar Industry Group’s Code of Practice
- / Clear feedstock disclosure (e.g. forestry residues, crop wastes)
- / Moderate pH (6–9) and low ash (<20%) for general horticultural use
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Article by Don Coyne – Founder, Byron Biochar