Human generated waste revealed as composition of black balls found on Sydney's eastern beaches

First reports emerged in mid October 2024 of numerous black spheres appearing on the sand at Coogee beach in Sydney’s east with preliminary testing by Randwick Council consistent with tar balls made up of oil and debris.

Similar sightings were soon reported at nearby Bondi, Bronte, Tamarama and Maroubra beaches, prompting immediate closures and cleanup efforts. Authorities initially feared these could be toxic ‘tar balls’, leading to health advisories and public warnings.

The mysterious black balls that washed up on Sydney's beaches in mid-October were likely lumps of "fatberg" containing traces of human faeces, methamphetamine and PFAS, according to a new detailed analysis of their composition.

A multi-disciplinary team of scientists have made significant progress in understanding the origins of the mysterious black balls. and while the exact origins of the waste remain uncertain, their composition is more disgusting than first thought.

UNSW Science – partnering with UNSW’s Mark Wainwright Analytical Centre (MWAC), DCCEEW Environmental Forensics, the NSW Environment Protection Authority (EPA), and Randwick Council – have run a series of analytical tests, to try and unravel this unusual marine mystery.

The investigation used a combination of standard and advanced chemical analytical techniques to reveal the composition and potential sources of the material.

Associate Professor Jon Beves, from the School of Chemistry, who led the investigation noted “at UNSW Science, we have been investigating the balls that appeared on Coogee Beach. Our analyses show that the material is not natural and cannot be attributed solely to an oil spill. It is most consistent with human generated waste.”

The analyses revealed the presence of alkanes typical of diesel fuel, fatty acids and other compounds commonly found in used cooking oils and soap. Additionally, perfluoroalkyl substances (the forever chemicals known as PFAS), steroidal compounds, antihypertensive medications, pesticides, and veterinary drugs were detected, consistent with contamination from sewage and industrial runoff.

Markers of human faecal waste, such as epicoprostanol and recreational drug residues like THC (from marijuana) and methamphetamine, were also identified – consistent with contributions from domestic sources.

The presence of fats, oils, and high calcium levels in the black balls suggests they could potentially be related to fat, oil, and grease (FOG) blobs commonly formed in sewage systems.

Implications and next steps
The exact origin of the washed up balls remains uncertain, but the results emphasise the need for continued monitoring and vigilance to identify similar incidents, especially at smaller scales where they may go unnoticed.

Professor William Alexander Donald, an analytical chemist involved in the research shared “this was a significant analytical challenge, with highly complex mixtures containing hundreds to thousands of components. We had a lot of fun analysing these mystery blobs, using deductive reasoning to trace the likely source to human waste.

“Carbon-14 dating suggested they weren’t purely from an oil spill, as the material was mostly modern carbon, loaded with fats, oils, and greasy molecules. Detecting markers of human fecal waste – like coprostanol – alongside recreational drugs like THC and industrial PFAS ‘forever chemicals’ pointed us to sewage and other sources of urban effluent as the most consistent origins.”

Sydney Water have reported that there are no known issues with Sydney Water plants, so the origin of the balls remains unsolved.

The team has also been alerted to unconfirmed reports of smaller, similar balls washing up over the past two years, and further investigations could reveal whether these have related compositions or not.

The research was led by UNSW researchers, including Associate Professor Jon Beves, A/Prof. Tim Barrows, Dr Martin Bucknall, Professor William Alexander Donald, Dr Albert Fahrenbach, Dr Sarah Hancock, Dr Christopher Hansen, Ms. Lisa Hua, Dr Martina Lessio, Dr Chris Marjo, Associate Professor Vinh Nguyen, Dr Martin Peeks, Dr Aditya Rawal, Dr Chowdhury Sarowar, Professor Timothy Schmidt, Dr Jake Violi, Dr Helen Wang and Chronos Radiocarbon Laboratory.

Image. Crushed debris of the beach balls that washed up on Sydney beaches. Credit: UNSW Chemistry