Lismore City Council says dry and windy conditions may have caused the fire at the Lismore Recycling and Recovery Centre on Sunday.

A post on the council Facebook page this morning said the green waste may have dried out after being exposed to “low humidity, strong winds and gusty conditions for an extended period of time” leading to spontaneous combustion.

The council is still assessing the damage caused to the Materials Recycling Facility by the fire.

“Council collects around 1600 tonnes of organic material per month from the Northern Rivers region,” the post said.

“Council has an aeration system that automatically releases oxygen into the compost piles. These are turned once every three weeks to ensure even distribution of heat throughout the piles.

“This process is undertaken in accordance with Australian Standards AS4454 – Compost, Soil Conditioners and Mulches and under the Environmental Guidelines: Composting and Related Organics Processing Facilities.

“The nature of composting organic materials is that it’s a heat-generating decomposition process – this is what breaks down the organic materials into compost.

“To produce compost it is necessary to maintain temperatures above 55 degrees for a minimum of 15 consecutive days to eliminate pathogens. It is not uncommon at times for temperatures to reach 80 degrees Celsius or above.

“Council has a sprinkler system and a permanent water truck on site which are used to keep the piles moist. Steam from the compost piles is often visible.

“The pile that we believe caught alight was exposed to low humidity, strong winds and gusty conditions for an extended period of time, which is believed to have led to moisture loss within the upper levels of the compost piles, causing spontaneous combustion of matter.

“Council believes this created embers which passed to other compost piles and eventually to stockpiles of plastic and paper.

“NSW Fire & Rescue is on site and is managing the process to agitate the compost stockpiles and saturate them with water to extinguish the smouldering.”

Public safety warnings about smoke being produced by the smouldering compost piles are still in place.

There are also some delays to waste collections (especially green bins) but residents should still put bins out as normal.

The Lismore Recycling & Recovery Centre in Wyrallah Road, East Lismore, will remain closed until the fire in the compost piles is extinguished and damage to the Materials Recovery Facility is assessed.