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Miracle mushroom clears toxins dirt cheap $160m for Kai Tak cleanup? Fungus could do it for $500,000
8 January 2006
South China Morning Post
A common mushroom served on dinner tables every day can destroy toxins in the heavily contaminated soil of places like the old Kai Tak airport, scientists have proved.
According to Chiu Siu-wai, associate professor at Chinese University, the waste produced by the phoenix oyster mushroom - a popular item in wet markets and supermarkets - can destroy organic contaminants, heavy metals and the pesticide DDT.
Professor Chiu said that if the government used her technique for the Kai Tak airport cleanup, it would have cost $500,000 instead of the $160 million spent so far.
When mushrooms are grown, a large quantity of soil and waste is left after the harvest - only a fifth of the nutrients are used. As a result a lot of enzymes are left over.
"We found that this waste and the leftover enzymes could be used to break down toxins. You only need one portion to every 99 portions of contaminated soil. It can be used on dry land as well as on the mud at the bottom of the ocean," she said.
"You can put the waste on top of the contaminated soil or mix it in if you want to speed things up. The left-over, dried-up spores work their way down and eat the garbage, while the enzymes break down the contaminants."
The process takes about one-third the time of existing techniques and is so cheap that Professor Chiu competed the research and testing without government or private grants.
"Mushroom cultivators pay people $150 to ship each truck of waste to the dump. So if you asked them for it, they would give it to you almost for free."
She has just completed her first large cleanup at an old shipyard in Tsing Yi for Gammon Construction. The soil in the yard facing Rambler Channel was full of organic and heavy-metal contaminants. Andrew Kwan Ming-tak,
senior project manager at Gammon, said: "There were some very stubborn contaminants. We contacted many universities but decided to work with Professor Chiu. We cleaned 150,000 tonnes of soil and it was 100 per cent successful. We are very happy.
"This can save us a lot of time and money in similar future projects. I think the need to clean up contaminated soil and seabed mud will only increase in the future."
The Kai Tak cleanup - to get rid of toxic carcinogenic contaminants caused by decades of pouring aviation fuel, petrol, paint, sump oil, antifreeze and other toxics in the soil - began in March 2000 after the government decided to redevelop the site.
Last November officials said the Kai Tak nullah - heavily polluted by heavy metals and organic contaminants - might have to be reclaimed if a cheap and effective way to clean it up could not be found.
Professor Chiu said: "The technique they have been using involves pumping air, water and nutrients into the soil - a very expensive process - so that the existing organisms can grow and eat the pollutants. But they don't realise that the organisms existing in soil may not be appropriate for the job.
"If they give me samples of the soil at the nullah now, I could do it for free."
The Civil Engineering and Development Department said: "We always welcome clean up proposals from interested parties and are open to consider any technique proven to be suitable, practicable, safe and cost-effective.
"We are conducting bioremediation [by injection of calcium nitrate] to clean the channel bed. We could not rule out reclaiming."
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