Recycling Oyster Shells
When you next sit down to enjoy some oysters for dinner, you can rest assured the shells won’t just end up lost in the rubbish.
Instead, there’s every chance they could be used as part of oyster restoration in Moreton Bay. In a bid to do their bit to help, the Rotary Club of Redcliffe Sunrise is also on board, assisting in the collection of oyster shells and transporting them to the nearest transfer station. You might be thinking why on Earth do they need to do this? Surprisingly, oysters aren’t as plentiful as they used to be in Moreton Bay and shellfish restoration is one step towards boosting population numbers once more.
“...oyster shells are not the same as FOGO (Food Organic and Garden Organic) as they do not decompose.”
So what is oyster restoration all about? The OzFish Central Moreton Bay Chapter is working on a goal to restore 100 hectares of shellfish reef in Moreton Bay over the next 10 years and beyond. The idea behind it all is an attempt to see the bay return to its former glory. Research has shown that used shells (which are collected from seafood businesses and restaurants) encourage live oysters to return and re-establish themselves naturally.
Rotary Club of Redcliffe Sunrise vice president and ESRAG (Environmental Sustainability Rotary Action Group) Moreton Bay ambassador Colin Scobie coordinates shell collection and assists in obtaining funding for future research to restore the bay.
“OzFish initially kicked off the idea to collect oyster shells about five years ago to restore fish habitat in the Moreton Bay,” Colin says. “Rotary head about the initiative two years ago at a Pumicestone Passage event organised by Healthy Land and Water during a Sunshine Coast world environment month and it went from there.”
So, how does it all work? It seems there is a bit involved in the process and you can’t just throw shells straight into the bay. Due to current legislation, used sterilised oyster shells can’t be placed into Moreton Bay as it is classified as a conservation Marine Park and restoration is not permitted. All research is carried out in the Port of Brisbane area by OzFish in collaboration with several universities of south east Queensland.
“Rotary club members are interconnected on a roster to collect used oyster shells from local restaurants and shucking houses and take the shells to the local waste transfer station,” Colin says of his part in the project.
“You see, oyster shells are not the same as FOGO (Food Organic and Garden Organic) as they do not decompose.
“Once 10 wheelie bins (which is approximately one tonne) are full of shells, they are taken to the OzFish Shellfish Recycling facility at the Port of Brisbane for processing. After being left out in the natural environment for 12 months, they are classified as bio secure and suitable for reuse for restoration.”
The question is how did the bay get to the point where restoration was needed?
“The problem is due to colonial over harvesting as a source of protein and the use of burnt oyster shells to make lime for the making of cement to build the Brisbane CBD, there are now not enough oysters to filter the Moreton Bay,” Colin says. “Oysters are therefore functionally extinct and need a hand to be restored to its previous pre-colonial day status.
“Without a hand up the bay will continue to deteriorating without these filter feeders. A little fun fact, oysters filter up to 180L of water per day.”
Given the lengthy time between collection and being placed back into the water, how does it all take place. It doesn’t involve anyone throwing or placing oyster shells in a scattered pattern in the water. Instead it involves a specially made basket, designed to go underwater. OzFish decided to take advantage of oysters’ natural tendency to grow together in clumps and created a Robust Oyster Basket, affectionately known as a ROB. These make it easy to transfer the used shell to the restoration site and also ensure volunteers can have the opportunity to help deploy the reefs without any heavy machinery.
A ROB is made from degradable steel mesh which is filled with the recycled oyster shells. The mesh takes about two years to degrade giving the oysters and other shellfish time to clump together before completely rusting out, leaving only a solid structure of oyster shells and living shellfish. Every oyster shell that is recycled and placed back into a suitable reef restoration site will provide a home for up to 10 baby oysters, some even more.
What can you do out in the community to play your part in oyster restoration?
“Get your local community involved and support "Save the Bay" for the 2032 Olympics, just like the local restaurants are,” Colin says.
To find out more about the OzFish shellfish reef restoration project, visit https://ozfish.org.au/projects/moreton-bay-shellfish-reef-restoration/