Turning Oil into Topsoil


BACTERIAL activity is turning oil-soaked industrial land at Osborne into rich topsoil.

The elaborate composting exercise is one of the largest in the country and replaces the old practice of carting contaminated soil to a landfill. Penrice Soda Products will spend more than $1 million remediating the soil, which was soaked with 100,000 litres of fuel more than 30 years ago. Penrice environment and quality manager Cameron Harker said the soil had been mixed with green waste, heaped in piles and covered in black plastic to stand for 16 weeks to be broken down by bacteria and converted to energy.

"It certainly is one of the largest bio-remediation projects in Australia," Mr Harker said yesterday.

"It is costing us well over $1 million to do this project but at the end of the day, we end up with a beautiful topsoil."

Earth engineering consultants Golder Associates designed the project, which will take most of the year to complete. Golder state manager Adam Kilsby said the six "bio-piles" were each 35m long, 12m wide and 1.8m high. Water and air were being fed in and temperatures were maintained between 50C and 70C. Bacteria in the soil would "feed" on the fuel oil and break down the hydrocarbons. The oil had escaped from a tank 38 years ago, when the property was under different ownership. It leached into the ground and contaminated 2450cu m of soil. Penrice inherited the problem and the expense of cleaning it up.

"We didn't want to just transfer the problem," Mr Kilsby said.

"The last preference is to dispose of it offsite to a landfill."

Mr Kilsby said finding another site for the soil would have been difficult because it had five times the accepted concentration of petroleum hydrocarbons for dumping.

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