UQ plant scientists are testing novel reuses for green waste from cities for horticulture.
Brisbane city generates more than 250,000 tonnes of green waste per year – which will end up in landfill if not currently recycled.

Biochar is a carbon-rich soil amendment that promises carbon offsets with accompanying farm and ecosystem benefits. It is manufactured by pyrolysis whereby organic material is thermally decomposed under oxygen limitation and co-production of bio-oils and syngas is possible.

UQ researchers are combining field, pot and laboratory based experiments to understand how biochar products made from waste (alone and in combination with compost) affect plant growth and why they promote or harm plants. Biochars were manufactured by three pyrolysis technologies from one common green waste source, allowing comparative analysis of plant performance and economic and environmental aspects.
To understand mechanisms behind effects on different plant species, UQ scientists have teamed up with University of Western Australia natural products chemists to identify potential plant promoting and harming chemicals in the biochars.

Co-generation of compost and biochar is possible - the study has revealed that leafy materials from green waste are best suited to compost, while woody materials to biochar production.
PARTNERS: Horticulture Australia Limited, Brisbane City Council, University of Western Australia, NSW DPI (one collaborative long-term field trial).

FUNDING: The city green waste project has been funded by Horticulture Australia Limited and Brisbane City Council. Brisbane City Council funds were from the Lord Mayor's Suburban Initiative Fund. Funding by Horticulture Australia Limited used voluntary contributions from Brisbane City Council and matched funds from the Australian Government. Collaborative work between UQ and The University of Western Australia (UWA) has been funded by a UQ Early Career Researcher Grant, with in-kind support from UWA.

Contact: Dr Jitka Kochanek (j.kochanek@uq.edu.au)

Photo (top right): Long-term field trials monitor plant performance and carbon longevity for the project duration. Here Dr Jitka Kochanek inspects a winter lettuce crop at the UQ Gatton field research station where three different biochars, a compost and a compost and biochar combination are being tested.

Photo (below): The study combines field, pot-based and laboratory experiments to understand how biochar and compost products made from recycled green waste affect plant growth for horticultural crops and why they promote or harm plants. This photo shows a glasshouse experiment using lettuce, selected for its sensitivity to plant promoting and harming compounds.

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