The Blackmans Bay Community Association (BBCA) invited Cristina from 'The New Black Biochar' to help them run a small workshop in Blackmans Bay.
The group made hundreds of litres of biochar from the she oak prunings collected at the community garden.
Biochar is made by layering wood in a kiln and restricting oxygen to the fire so that it burns hot with almost no smoke. 
Before it turns to ash it is completely doused in water, leaving behind useful charcoal or biochar. 
"The charcoal is then 'charged' with nutrients, perhaps from weed tea, worm castings, seaweed or fish fertiliser," said Louisa d'Arville, the president and secretary of the BBCA.
"It can be used to add to your compost, or straight into your garden beds.
"In sandy soil like we have in Blackmans Bay it helps by holding a huge cache of nutrients for your plants that the silica in sandy soil just can't hold onto."
Other applications include using it before it has been charged to feed to livestock and to line rubbish bins. 
"Coming up to winter solstice, people might like to think about how they go about their bonfires, maybe they can get more out of it than a pile of ash at the end," Louisa said.
Making biochar is a way to lock up carbon rather than releasing it into the atmosphere as you would in a normal, backyard bonfire.