Student plants fine idea on mussel waste

By CATHERINE LOFT

An Auckland science student is researching ways to recycle mussel waste by using the shell in concrete and the tissue in fertiliser.

Claire Barnaby says mussel farming is becoming one of New Zealand's largest export industries, but little is done about the waste.

Research by the Auckland University of Technology masters student shows that mussel processing plants dump the shells and tissue in paddocks where they are left to decay.

Her thesis findings on using the waste in concrete and in organic fertilisers were presented at the joint conference of the New Zealand Marine Sciences Society and the Australasian Society for Psychology and Aquatic Botany this month.

Andrew Jeffs, principal scientist at the National Institute of Water and Atmospheric Research (Niwa), supports her project.

"The mussel industry's code of practice is to reduce waste," Mr Jeffs said.

"Claire's research could be beneficial for Niwa if she can come up with some good practical ways to dispose of this biological natural waste."

Last year 25,000 tonnes of mussels worth $185 million were exported. New Zealand may benefit economically, but not environmentally, according to AUT scientists.

Miss Barnaby said it was hard to quantify how much waste was dumped each year, but it was getting out of control, especially in Marlborough and the Coromandel.

"Mussel waste depends on sea variation, times of harvest, location and treatment," she said. "Mussel waste cannot just be thrown into the paddock forever. There will come a time when something needs to be done and my research will hopefully help provide solutions."

Her experiments with concrete - adding crushed shells to the cement mix - have not been very successful to date. "You wouldn't want to drive your BMW on it yet," she said.

But Miss Barnaby is persevering with her experiments to find the right mix.

Dr Andrea Alfaro, Miss Barnaby's supervisor and a marine ecology lecturer, says the concrete could be used as insulation for walls.

Miss Barnaby cannot test the idea at AUT but would be keen to develop it if offered other facilities.

The nitrogen phosphate in mussel tissue is good for making fertiliser. Miss Barnaby plans to use the fertiliser on tomato plants.

Thirty plants will be fed a general nutrient and another 30 will receive a mixture of rotten mussel tissue mixed with sawdust and water. She will monitor the growth of the plants, noting the major differences.

Westpac Mussels in Henderson crushes its mussel shells and spreads them on driveways at a local orchard.

Jo Ujeur, a general administrator at its factory, said people in West Auckland were keen to use mussel shells in landscaping.

"They look good when they are dry because they have a white, picturesque finish," he said.

There were some complaints about smell during the summer, but it quickly disappeared.

Miss Barnaby said that was a good, practical solution, but it did not make money.

* Catherine Loft is a journalism student at Auckland University of Technology.