According to the Tasmanian Salmonid Growers Association, the state’s farmed salmon industry is worth almost $550 million a year and employs thousands of locals both directly and indirectly. As a result, it is providing significant economic benefits to the island state.
The region’s booming aquaculture industry creates annually thousands of tonnes of plastic waste from salmon pens, which Tasmania-based recycler Envorinex identified could be used in manufacturing infrastructure products if recycled.
Envorinex Managing Director Jenny Brown purchased the company (formerly known as SVP Industries) in 2009, and has since investigated different ways to collect, recycle and manufacture products from waste plastic sourced from Tasmania’s myriad industry sectors, including aquaculture.
The firm has been recycling plastics from its facility in Tasmania’s northeast since 2009. In 2015, it installed its first complete recycling line to process the high density polyethylene plastics (HDPE) used in salmon pens and feed pipes.
The new system allows Envorinex to process the waste pens and feed pipes, which are collected from salmon farms across the state, brought back to the factory and stored onsite until it is ready to be processed and recycled.
“We’ve had a contract with salmon farmer Tassal for quite some time, and we’re about to enter into another contract with them in a couple of months, which will focus on recycling fishing nets using a similar process,” says Ms. Brown.
“The pens also have stanchions, which are upright mouldings that sit around the salmon pen – that’s also made from HDPE,” she adds. HDPE is also used in oyster baskets and fishing floats.
At Envorinex’s facility, the HDPE is first shredded, then the material is granulated and extruded. Finally, it is pelletised and sold or used in the firm’s manufacturing process.
One product Envorinex is manufacturing at its Tasmanian facility using the pellets is a grid – the EnvoHexGrid – for permeable paving.
Ms. Brown says only the stanchions and fishing buoys from the salmon farms can be recycled and remanufactured into the grid product because they are moulding grade.
The EnvoHexGrid is sold to agents who then supply the materials to councils, gardeners and landscapers across the country as a replacement for concrete or asphalt.
Ms. Brown explains that the grid product is used for permeable paving for beach access points, gardens, lawns and even golf clubs.
A permeable grid can be installed rather than pouring a concrete slab or pavement, for instance. The gaps in the grid are filled with materials such as fine gravel, resulting in an economical and practical paving solution and reducing stormwater runoff.
“The great thing is that in 50 years’ time you can pull it back up and recycle it again,” says Ms. Brown.
While recycling and manufacturing the EnvoHexGrid only accounts for roughly 15 per cent of Envorinex’s business, it still involves a significant amount of physical recycled material, given that Ms. Brown estimates the company recycles roughly 2000 tonnes of HDPE annually.
“[HDPE] is a valuable resource to us – there’s no reason why it can’t be reused,” says Ms. Brown. “Previously, all of this material was going to landfill and it’s a huge volume of material. It’s not really the weight that’s the issue, it’s the size. Some of these pipes are up to 800 millimetres in diameter, so they’re large volumes that we’re processing through the factory.”
Envorinex also recycles polyethylene pipes used for water irrigation lines and mining sites, some of which is used to make delineator baseplates used on council roads.
While Ms. Brown agrees that turning end-of-life salmon pens into infrastructure components such as permeable grids seems quite the “Tasmanian thing to do”, she says similar practice is employed elsewhere around the globe and Australia is slowly catching up to the rest of the world in this space.
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