Our worms too lazy to go to work

PUBLISHED : Monday, 16 April, 2007, 12:00am
UPDATED : Monday, 16 April, 2007, 12:00am

Thousands of imported earthworms could be used to eat household food waste at housing estates by the end of the year if a pilot scheme conducted at Kadoorie Farm is successful.

About 12,000 red worms from the mainland are being used in the trial, which mirrors a system used at the Sydney Olympic village in 2000 and likely to be used in Beijing next year.

Local worms cannot be used because they are too 'lazy' to work through the waste from top to bottom, the farm's worm expert, Judy Wan Hon-chi, says.

As well as eating the waste, the worms ventilate it with their burrows and provide excrement that can be used as fertiliser.

Dr Wan started a three-month pilot scheme last month to collect trial data for a food waste reduction programme, which is expected to be launched by the end of this year at some of the 18 housing estates that have their own gardening programmes.

The impact of the city's climate on the worms, the type and amount of food waste they prefer and the best way to harvest the excrement are being studied, along with ways to prevent the red worms breeding with local worms.

The worms have been put into three large glass boxes, 65cm long and 90cm high, with soil beds, to eat three to six kilograms of food waste, such as vegetables and fruit peel, from the farm's staff canteen.

According to the Environmental Protection Department, over the past five years about 2,500 tonnes of domestic food waste was dumped in landfills daily, accounting for over 35 per cent of total domestic waste.

While officials plan to employ a composting machine to reduce the volume of commercial food waste, the worms, imported from the mainland and the United States, would be used on domestic waste.

Explaining why Hong Kong worms were not up to the task, Dr Wan said local worms were lazier than imported ones. 'They often stay at the bottom part of the soil and seldom crawl to the surface. It takes longer for them to decompose food waste,' she said, citing results of an experiment conducted in 2005.

The worms remove bacteria and pathogens in the soil by consuming them, and their excrement can be used as fertiliser with no further processing. 'They do not need a break and they consume food at least half of their weight every day,' Dr Wan said.

This means that if a red worm weighs a gram, 5,000 could digest 21/2kg of food waste a day.

Worms became popular among households in North America and Europe five years ago and are being sold at US$20 for 1,000.

Dr Wan said another aim of the scheme, approved by the Agriculture, Fisheries and Conservation Department, was to harvest excrement without contact with worms and their eggs, avoiding their escaping and breeding with local worms.