Fire investigators believe overheated lithium-ion batteries inside recycled material triggered the multi-million dollar blaze which destroyed Canberra's major recycling plant in Hume on Boxing Day last year.
An investigation by ACT Fire & Rescue found evidence of "multiple batteries of various types" inside the Hume facility's waste compactor.
"The investigation revealed evidence that the presence of multiple batteries of varying types, identified in the remains of the waste compacter, caused a thermal runaway which ignited the fire," City Services Chris Steel said.
"The ACT Fire & Rescue report specifically points the finger at lithium batteries."
Thermal runaway is a phenomenon caused when lithium-ion batteries reach an uncontrolled, self-heating state due to a chemical reaction inside.
During thermal runaway, the energy stored inside the battery cell is released in milliseconds and temperatures rise incredibly quickly. It triggers a chain reaction which can generate temperatures of up to 400 degrees Celsius.
Often when this occurs, the out-gassing of chemicals from inside the battery creates a fire too hot to extinguish conventionally, and can reignite over and over.
There can be multiple reasons for thermal runaway including battery overcharging, internal short circuits, mechanical compression, or exposure to extreme heat or cold. Cheap batteries with poor internal construction, or batteries which are imbedded inside plastic or stuffed toys and dumped in recycling, are common triggers.
The Hume Materials Recovery Centre fire has been the largest lithium-ion-triggered fire that ACT Fire and Rescue has faced to date, and smouldered for hours.
Mr Steel said that this outcome was a timely reminder to the community of the necessity to dispose of batteries properly, and not to put batteries of any kind in household recycling or landfill bins.
"We're asking the community to please remember: 'Don't bin your batteries'," he said.
"There are a number of free battery drop-off options in the ACT and NSW as part of the battery product stewardship scheme, B-cycle and at resource management centres."
There are fines of up to $800 associated with incorrectly and illegally disposing of all batteries.
The ACT government is a partner with B-cycle, the national battery product stewardship scheme launched in January 2022.
B-cycle allows household batteries, and easily removable batteries including those used in power tools and cameras, to be dropped off at a range of locations, including Bunnings stores, in the ACT and NSW.
The scheme is run by the Battery Stewardship Council and authorised by the Australian Competition and Consumer Commission.
Other types of batteries, such as e-scooter and e-bike batteries, can be dropped off for free at the hazardous waste area at the Mitchell or Mugga Lane resource management centres.
Since the fire at the Materials Recovery Facility in Hume, the ACT government has been transporting the region's recycling to three facilities in Western Sydney and one in Victoria.
Around 229 tonnes per day is being transported, which is an average of nine trucks per day.
"The stockpile of recycling material following the fire has now been entirely cleared from Mugga Resource Management Centre, with 6550 tonnes recovered and only 60 tonnes of spoil being sent to landfill," Mr Steel said.
"Given the recycling plant was almost completely destroyed by the fire, this recovery rate is an excellent outcome and I want to thank staff for their work to ensure materials in Canberra's yellow bins continue to be recycled."
To date it has cost the government $1.4 million to transport the material interstate.
The government is continuing to liaise with its insurers, the ACT Insurance Authority, in relation to the recovery of most of these additional costs.
A copy of ACT Fire & Rescue's report into the recycling facility fire is located at cityservices.act.gov.au.
