Resource recovery specialist Repurpose It will use an Australia-first technology to help recycle residual glass from materials recovery facilities for civil construction.
Glass was discovered more than 5000 years ago and it takes one million years to break down naturally.
If businesses recycle it instead, it not only preserves landfill space – but the environmental footprint is significant – saving energy and raw materials. Per tonne, recycled glass conserves more than 1.1 tonnes of raw materials, including sand, limestone and soda ash, and uses 75 per cent less energy – according to a Planet Ark fact sheet.
Glass ready for treatment is categorised as glass cullet – sorted and crushed glass that is appropriate for manufacturing. Glass fines are crushed glass and often unsuitable for use in manufacturing due to the particles being too small, or contaminated with ceramic, stoneware, Pyrex and plastic. They are predominately used in civil construction in the form of a sand replacement in asphalt, concrete, road base and pipe embedment. There is also post-consumer glass, which includes windows and packaging waste.
As Australia’s recycling industry faces a glut of glass at a significantly reduced value, there are inevitably materials left over to be landfilled or stockpiled.
For resource recovery business Repurpose It, targeting the highest order recyclable is a priority, and in an ideal world, help it go straight back into manufacturing.
Repurpose It is in the process of installing Australia’s first construction and demolition waste washing plant, which will treat the residual waste from materials recovery facilities (MRFs) and process it back into materials suitable for civil construction. Based in Melbourne, Repurpose It will wash materials including rail ballast, glass, excavated materials and demolition waste fines.
FROM MRFS TO REPURPOSE IT
Repurpose It’s George Hatzimanolis says that some glass fines are already arriving at its Epping site from MRFs mixed with ceramic, stone and porcelain.
He says the materials are typically less than 20 to 30 millimetres in particular size and carry the risk of contamination if not treated properly.
“One of the more problematic materials is glass fines. The glass out of a MRF from kerbside collection is left with residual contaminants in there, from organics to sugars, and molasses and alcohol and all the other residues from your kerbside bin,” George says.
“Even though you’ve got glass that’s been fractionated to a suitable size for a sand replacement or road base material, there is still a residual amount of organics and contaminants on that that limits its use.”
He adds that this also comes with odour and bacteria issues, and potential leachate if disposed of to landfill.
George says that glass fines are commonly used in road base, but if treated properly, the resource recovery industry can begin to set its sights on higher value materials such as pipe bedding, sand replacements or manufactured asphalt or concrete. This is because odour becomes an issue when the materials come into human contact.
Its one of the reasons Repurpose It has invested in the C&D washing plant, slated to be fully operational in November. The washing plant will take glass fines and scrub them clean through wet processing – a stark contrast to the current dry processing technology used in Australia.
“What we will end up with is a clean glass fines material that is a similar particular size to virgin sand and free of any contaminants, bacteria, odours or organics. This will enable a greater reuse of where that material can go, both from a performance point of view, occupational health and safety and managing our environmental risk,” George says.
“This is really about targeting the residuals – the really problematic waste streams that our MRFs can’t deal with. These are the materials ending up stockpiled.”
He adds that disposal costs to Repurpose It are cheaper than landfill and offer greater economic value to MRFs.
“On top of that, we are offsetting a lot of carbon because our carbon footprint is significantly less than landfill.”
George notes that sand quarries are being pushed further away as a result of the urban sprawl – prompting more demand for sand replacements. For this reason, Repurpose It is aiming to produce replacements comparative to virgin sand, with some limitations depending on the application. The company has established arrangements with Melbourne-based MRFs to remove and process their existing stockpile of glass. Repurpose It has established in-principle agreements to onsell the clean glass sand it will produce to the construction industry. At full capacity, there is an opportunity to wash 200,000 tonnes of glass each year.
The process will involve the material being picked up from the MRF in granulate form, or sand, and then screened for unrecoverable materials. Eddy currents will remove non-ferrous or ferrous metals and contaminants, before moving to wet processing, where glass will be blasted with clean water to remove organic or contaminant fractions.
From there, it will travel through a scrubbing process with forced abrasion. This will follow with a secondary wet screening process. Finally, forced floatation will remove any organics or lighter particles and separate them by density.
George says this will result in a clean glass stream fractionate of roughly up to three millimetres and three to seven millimetres, with the ability to blend it to meet the particular size requirements of its customers.
He says cullet goes through the same process, with the ability to feed in anything less than 150 millimetres.
George says Repurpose It is continuing to work with the Australian Road Research Board, Cement & Concrete Aggregates Australia and VicRoads to modernise their specifications in line with new technologies.
VicRoads’ Technical Note TN107 stipulates the use of recycled materials in road construction, with glass fines able to be added to some granular products, some non-wearing course asphalt mixes and granular filter materials.
It is intended to act as a guide for the use of recycled materials in place of those derived from quarried sources.
George is also working towards securing Green Building Council of Australia Green Star certification.
“The opportunity with these products is to support projects that are striving to achieve an Infrastructure Sustainability Council of Australia rating,” he says.
“We can’t afford to just get rid of glass fines in road base anymore as they offer viable alternatives to higher end products.”