Biodigester converts waste to compost at University of Sydney

ACT organics facility

A cutting-edge biodigester has been installed at the University of Sydney, for odour- and methane-free processing of organic waste into compost for use on campus.

With the support of a grant from the New South Wales Government, the HotRot biodigester – also known as Chester the Digester – will allow the University to manage organic waste on campus for the first time.

The biodigester weighs 2500 kilograms and can break down up to 500 kilograms of waste every day, transforming products such as coffee grounds, teabags, food waste and street sweepings into compost to be used on campus.

James Griffin, NSW Environment and Heritage Minister said every tonne of food waste diverted from landfill is equivalent to saving one and a half tonnes of carbon dioxide.

“The NSW Government contributed more than $375,000 towards Chester the Digester through our Waste Less, Recycle More program to help reduce landfill and turn waste into a useful resource,” Griffin said.

“Initiatives like this one are a vital part of our target to halve the amount of organic waste sent to landfill by 2030 through the Waste and Sustainable Materials Strategy 2041.”

Professor Mark Scott, University Vice-Chancellor and Principal said the biodigester was an important step to help the university reach its sustainability targets.

“Our staff and students identified waste and our contribution to landfill as the top area where they wanted to see the university take action on sustainability, which informed the waste reduction and management targets set out in our Sustainability Strategy.

“This project and future applications will enable us to meet our ambitious waste and recycling targets, including zero waste to landfill by 2030, 80 per cent organics recovery and food waste to compost, and single-use plastic free campuses by 2025.”

How it works

The university’s biodigester will break down food waste, coffee grounds, tea bags, animal bedding, street sweepings and compostable coffee cups and plates.

The waste, collected from select cafes, as well as staff and student sites, will be fed into the rotating machinery, transformed into compost, then used by the Central Operations Open Spaces Team, eliminating the need to transport organic waste off campus for processing.

The biodigester has already begun processing food waste and can operate 24/7. Once operating at capacity it will process up to 500 kilograms daily.

Grounds staff will collect waste from the new green-lid organic waste bins installed in the Law Library Lounge and Charles Perkins Centre, as well as from staff offices, research facilities and cafes across campus.

Organic waste collection points will be listed as an amenity on the Camperdown/Darlington campus map. Once the volume of waste disposal has been determined at each collection point, additional sites may be added.

Teaching and research

Professor Ali Abbas, who directs the Waste Transformation Research Hub in the Faculty of Engineering, where he is Acting Head of School of Chemical and Biomolecular Engineering, said the Faculty will work to optimise the digester process operation so the university can embed circular economy principles more closely in planning and management of materials on campus.

Circular economy is a systemic shift in the way we deal with material resources, products and waste. It is based on principles of designing out waste, and keeping materials in use.

“This biodigester serves to fast-track the implementation of circular economy on campus, with its organic compost products used to rebuild soil health and grow food, and therefore regenerate nature. It is personally exciting to see our campus beginning to deal with our own waste, locally, creating organic composts that can safely re-enter the natural systems and restore it rather than be sent to landfill.”

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