LA County fire official says Apollo Fire erupted after mulch spontaneously combusted

A Los Angeles County fire official said Monday that the cause of the Apollo Fire in the Antelope Valley — which torched 800 acres and destroyed at least one home — was mulch that spontaneously combusted.

Deputy Chief Albert Yanagisawa confirmed the cause to LAist, adding that the department has responded to about 70 mulch-related fires since September 2023.

“Community members have been ringing the bell about the dangers of the trash mulch to no avail,” said Susan Allison during a meeting that stretched for more than two hours at the Grace Chapel Neenach Church in Lancaster on Saturday.

Representatives from L.A. County departments, including fire, public health, regional planning, and a staff member from L.A. County Supervisor Kathryn Barger’s office, stood in front of a room of dozens of angry residents who shared their questions, concerns and stories about how piles of mulch mixed with trash have long littered the desert landscape around them.

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The property where the Apollo fire started, as captured by satellite, on January 25, 2023, shows large piles of mulch.

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How mulch fires start

Firefighters acknowledged the issue, saying that as organic matter breaks down, it heats up, particularly in the middle of the piles, which can lead to spontaneous combustion.

“We understand and agree that it is a significant problem affecting your community," said L.A. County Battalion Chief Kevin DeJong at the meeting.

When the piles burst into flames they become difficult for firefighters to put out, DeJong explained, as water often fails to penetrate deep enough to extinguish the source of the blaze.

“When they're on fire, they need to cook down,” DeJong said. “To bring mechanized equipment into them, you're going to totally destroy the mechanized equipment due to the heat.”

Fire still visible

Satellite imagery from January 2023 reviewed by LAist shows large piles of green waste dumped on the property where the Apollo Fire started.

When LAist visited the site of the fire on Saturday, smoke and flames were seen rising from the mulch material nearly two weeks after the fire had been contained.