Astec Australia’s mobile screen plant is giving plasterboard waste new life and reducing a reliance on landfill.
Home improvements and renovations boomed during the COVID-19 pandemic as lockdowns forced people to stay at home.
According to Australian Bureau of Statistics figures, during the 12 months to October 2021 renovations approvals totalled $11.82 billion nationally.
Hand-in-hand with the building frenzy was an increase in construction and demolition waste. While resource recovery rates for C&D materials is increasing, there is still millions of tonnes of waste dumped in landfills.
Plasterboard is usually a harmless material but when placed with biodegradable waste in airless, moist landfill sites it can create hydrogen sulphide. Latest engineering, such as Astec Australia’s GT205MF Tracked Mobile Screen Plant, means plasterboard waste is almost 100 per cent recyclable.
“Plasterboard is a very good quality resource that was previously going to waste,” says Adam Gordon, Astec Business Line Manger – Materials Solutions. “It is high-grade gypsum sandwiched between two layers of cardboard. We need to better use it instead of burying it in landfill.”
The key ingredient in plasterboard is gypsum, a sulphate mineral mixed with water and pressed between two lining sheets, usually cardboard, before being dried out to create a solid board. Once recycled, the gypsum can be reused as an agricultural soil improver, or as an ingredient in the production of cement. The cardboard can also be broken down and added into wood mulch. Any small gypsum particles left over help the compost process.
The plasterboard first needs to be shredded. Adam says most grinders on the market will be able to shred plasterboard effectively, the final solution is “having the right screen” to separate the materials.
He says the GT205MF Mobile Screen Plant produces three products – oversized which will be re-shredded, cardboard, and a minus 2-millimetre gypsum. The GT205MF is ideal to recycle plasterboard because it can screen the smaller, more difficult pieces.
“Traditionally, a standard screen has one motion, which may be okay for bigger material, but once you start getting down to one or two millimetres you will struggle,” Adam says. “Astec has added isolation frames with hydraulic exciters so you can introduce an additional vibration. We can get lighter particles to be accurately sized more efficiently.
“A traditional screen has one set vibration, one RPM and one combined motion – it tends to be overloaded at the feed-point, perfect in the middle and not enough feed in the bottom section causing this material to bounce and being very difficult to size efficiently.
“With the multi-frequency screen you can set up each screen section to match the material load directly above it. It’s like having six screens in one. It’s all about efficiency, the more tonnes you can do, the more efficient you are, the more economical you become.”
Adam says the GT205MF Mobile Screen Plant can process up to 110 tonnes an hour of plasterboard, creating high-grade gypsum for reuse.
“With gypsum, the whiter it is the higher the purity. It’s very high-grade from plasterboard and is a valuable resource that should be reused. You can bulk it into stockpiles and sell it on to farmers or other purposes.”
The GT205MF has 9 square metres of screen area on the top deck and 8.1 square metres on the bottom deck. The top deck has side tensioned screen cloths, hydraulic angle adjustment and adjustable amplitude and nominal 850 RPM. The bottom deck has end tensioned screen cloths and up to 4200 RPM on each exciter which are individually adjustable.
The plant is a tracked unit, easily transported to various sites, increasing the economics by processing material at various locations.
Adam says recycling plasterboard could be one solution to the mounting clean-up facing New South Wales and Queensland communities following devastating floods earlier this year.
Piles of rubbish lining streets include plasterboard ripped from the walls of flood damaged homes and businesses. Some industry experts say up to a year’s worth of waste needs to be cleared as a result of the floods. With regional landfills under pressure there are concerns about where the waste will end up.
Adam says recycling the plasterboard could help ease the pressure and provide opportunities to reuse a valuable resource that is currently going to waste.
“Initially we need to get rid of the waste on the nature strip to help the environment and the mental health of residents,” he says.
“Plasterboard can be stored so it can be separated and processed later, and the resources recovered for reuse.”