Please note that online plant orders are currently unavailable. Learn more.

Please note that online plant orders are currently unavailable. Learn more.

Biochar Explained

There’s been a lot of talk about Biochar, but what is it? How is it made? And what does it do?

Biochar is a relatively new (or really old) organic amendment for soil. The discovery that lead to the production of Biochar for use in horticulture and agriculture was based on the finding of Black Carbon as a major soil component in some unusually productive ancient soils in the Amazon called Terra Preta. Biochar helps to mimic these ancient soils and is created by burning plant material using pyrolysis (burning from the top down with a limited oxygen supply). The resulting material is very different to the products created by burning wood in an open fire, due to the limited oxygen used during this process (even though Biochar can be found naturally occurring in soils where there has been previous forest fires).

Pyrolysis produces a charcoal that maintains the plants cell structure and integrity, creating a highly porous, carbon-rich material, that not only acts as a sponge for water and nutrients, but also a catalyst to promote healthy soils. 

Now, burning something to make a soil amendment sounds bad for the environment, and it can be, but it all depends on the material used to create Biochar, and it has been seen as a way of closing the loop on agriculture production by converting 100% botanical waste, like nut shells, rice husks and other botanical biproducts that would otherwise be sent to landfill (consuming valuable space, and creating gases such as methane) into this beneficial agricultural supplement.

The benefits

The Biochar has a honeycomb like structure that helps to trap moisture and nutrients in the soil and creates a hospitable environment for microbes. This highly porous form of charcoal also improves soil structure (in both clay and sandy soils) and the water holding capacity of soils and potting mixes.

“Biochar is capable of holding 4 times its volume in water,” says Trevor Barrows from Charman Biochar. “It is this ability to hold moisture and trap it in the soil and potting mix which means that you can use much less water, and get much better plant growth.”

The honeycomb structure also allows microbes to live and breed in the protective cells, using this as a base while feeding on decomposing material. This increased microbial activity helps to make more nutrients available to the plant, and improve overall soil structure. The honeycomb cells trap nutrients near the plant roots, along with moisture, leading to improved plant growth.

According to Dr Mae-Wan Ho, the soil’s depth of Terra Preta in the Amazon can reach 2 metres in some areas, and can regenerate itself at the rate of about 1 cm a year! The addition of Biochar to normal garden soils hopes to replicate this phenomenon. This may or may not be possible, but at worst, botanical waste is being turned in to something that helps to safely return organic residues to our earth while improving water conservation, plant growth and soil health, instead of contributing to landfill and greenhouse gas emissions.


Biochar is easy to apply in new and established garden.

New: incorporate into soils at planting.

Established: spread one litre per square meter and lightly rake before applying mulch.

Potting mix: incorporate into potting mix prior to planting.

Compost heaps: add as an alternative layer in your compost heap. 


You can get Biochar from us here.


4.7 million Australian households are growing their own food

Our new Seed Manager was planting seeds as a child – that’s over 20 years of experience

Australia, where bird song began

Tim Sansom discusses Tim Low's new book

Bees and Colony Collapse

Jim Sansom tells us why the collapse of bee colonies is a huge threat to our food supplies

Bees Under Threat

Clive Blazey explains the largest ideas presented by bee keeper and BBC presenter Bill Turnbull

Biodiversity in the garden

The benefits of encouraging a diverse ecosystem in your garden

Bringing carbon down to earth

Clive Blazey talks about sequestering carbon.

Creating the world we want, rather than fighting the world we reject

David Holmgren recalls his first meeting with Bill Mollison

Diggers explains how we make our own soil

Diggers explains how we make our own soil

Five Plants That Could Save The World

Tim Entwisle tells us how plants may provide the solutions to pollution and resource shortages

Fungi and Soil Creation

Botanic Gardens Director Stephen Forbes explains the role of fungi in creating soil

Gardening in a changing climate

Diggers former head gardener, Simon Rickard, shares the lessons learnt after a decade gardening in increasingly fluctuating conditions.

Gardening is the key to reducing Waste

Marcelle Swanson explains how to move away from plastics and improve our health

Giant Miscanthus

Tim Sansom explains how Giant Miscanthus can build organic carbon in backyards

Inspired by Diggers - 20 years ago!

Tim Sansom takes a tour of Joost Bakker’s Future Food System house

Manuka honey: is it a food or a medicine?

Penny Blazey reviews the history of this renowned honey

Monsanto's glyphosate

Graeme Sait assesses the ‘SAFE’ glyphosate spin to increase chemical usage

Organic gardening – growing your own fertility

Sharing a gardener’s perspective on building fertility the organic way.

Organic gardening not just for food

Bill Bampton talks about creating garden beauty without petrochemicals

Q&A - How Carbon Creates Soils

World organic expert Dr. Christine Jones talks about the life-giving link between carbon and healthy topsoil

Reduce waste this holiday season

Join Erin Rhoads, the Rogue Ginger and waste-free advocate for some tips on waste reduction this festive season.

Save Water By Growing Your Own

Clive Blazey explains how you can save water by growing your own food at home

The Cape - Growing food in the heart of this sustainable community

Tim Sansom discovers a housing development making a real difference.

The difference between animal manures

Not all manures are equal, some are actually better than others.

The Future of Food

English author Colin Tudge explains how corporates and government threaten gardening and horticulture

The Soil Food Web

Hugh Hunkin explains how our lives depend on microscopic creatures

There Are No Jobs On A Dead Planet

An edited transcript from Kumi Naidoo's 2014 TED talk "Contagious courage, a billion individual acts"

Trees Are Vital For Cooling Our Cities

Bill Bampton explains why tree planting needs to start on a massive scale

Trees for Shade

Clive Blazey explains why shade canopy is vital in tree selections

Watering tips for gardens

Here are Diggers top tips to help Aussie Gardeners reduce their water consumption.

Why climate change threatens our biological systems

Clive Blazey reports on Tim Flannery's lecture on behalf of the Climate Commission

Why Diggers annual trials are so important

Our new Seed Manager explains the trial process at Diggers

Why do we import food?

Asks food writer Cherry Ripe

Why the collapse of bees is so serious

Fiona Chambers explains what Diggers members can do to help

Without trees we cannot inhabit the Earth

Bill Mollison's legacy foretells our climate crisis
Back To Top
Member Exclusives
2022 Gardening Diary and Calendar Combo
2022 Gardening Diary and Calendar Combo
2022 Gardening Diary & Calendar Combo The complete garden combo for 2022! The beautifully illustrated Diggers Club Diary features a week to a page, seeds to sow each month, blank pages for seasonal observations, and handy pockets for your seed packets and plant labels, while The Diggers Calendar showcases stunning garden photography to inspire y...
Member $35.00
Checking stock, please wait..
18 SEED PACKETS: The gift that keeps on giving for a year. This collection will guarantee 12 months of heirloom veges. The recipient will receive seeds for each season ensuring a supply of heirloom vegetables. The pack contains a total of 18 packets of vegetables seeds (Beetroot, Bean, Broccoli, Carrot, Cauliflower, Lettuce, Onion, Pea, Silverbe...
Member $59.95
Checking stock, please wait..
2 year membership + Garden Calendar and 2 Seed Packets
2 year membership + Garden Calendar and 2 Seed Packets
Membership: MNE2CA2
Join the club and receive an exclusive gift, valued at $30. A stunning calendar featuring key dates, a guide to which seeds to sow each month and plenty of space to add your own events. Plus two free packets of some popular seeds – Tomato 'Black Cherry' and Lettuce Heirloom Mix.
Member $79.00
Non-Member $79.00
Checking stock, please wait..