Authorities are carrying out "daily odour surveys" at Farmborough Heights and Kembla Grange after residents made more than 80 complaints about a persistent stink.
Multiple residents have told the Mercury the stench is so bad it impacts their daily life, forcing them to close their windows and cancel outdoor walks and barbecues.
While a joint probe by city council and the Environmental Protection Authority is yet to pinpoint the cause of the smell, some residents believe Wollongong council's recently introduced FOGO program - where tonnes of green household waste are dumped and processed at the nearby Soilco plant - is at least in part to blame.
A spokeswoman for the EPA said the authority had received 80 complaints from residents since November 9 and had sent inspectors to the area.
"The EPA is undertaking daily odour surveys and meeting with nearby EPA-licensed premises to discuss the issue," she said.
"The EPA has been conducting inspections in the Kembla Grange area to try and determine the source, which have been reported in different locations with variable odour characteristics.
"The EPA is also reviewing all odour reports to look for relevant patterns or trends in community impacts and is speaking to licensed businesses in the area about potential additional measures that may help reduce odour impacts on the neighbouring community."
Some residents told the Mercury the smell seemed worse in the morning, or when it was wet, or when the wind blew in a certain direction.
They described the smell as "like rotting vegetation" or "like walking into a chook pen when it's really, really wet".
"It's like something's really, really dead," one resident said. "You get it every morning when you open your window."
Wollongong City Council's Food Organics and Garden Organics service, introduced November 16, has been credited with diverting massive quantities of greenhouse gas-emitting food scraps from landfill and into the Soilco plant off West Dapto Road. The material is chopped into small pieces then spends 10 days inside heat and air-controlled storage bunkers, then is moved to a composting facility to "mature outdoors" for several weeks, before it is sent to retailers and wholesalers in the form of bagged compost.
A spokeswoman for Wollongong City Council said council had provided residents with a roll of compositible liners for household FOGO bins, to help combat the smell of rotting food waste breaking down.
The spokeswoman said the city's waste facilities were regulated by the EPA and were required to manage odour. The city also received complaints about the stench, she said, via its customer service line.
"At present, we're unsure what is causing the odour," she said, adding council was working with the EPA.
"Any business regulated by the EPA must ensure they have adequate controls and management practices to prevent offensive odours from impacting surrounding neighbours. In cases where these controls are not adequate or fail, the business must identify a solution and address the generation of odour. The EPA can require those changes to be made if needed."
Soilco was contacted for comment.