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Recycling on the microscale has macro advantages

Growing populations and technological advances are driving consumption,using up raw materials,and creating a crisis in waste management.What can we do with the ever-growing volume of obsolete electronics or ‘e-waste’,for example,which will reach 50 million tons by 2021? A large proportion is currently transported to developing countries to be processed,while the rest is stockpiled or sent to landfill,according to researchers Veena Sahajwalla and Rumana Hossain of UNSW Sydney in Australia,who have developed a new approach to recycling.

“Australia’s governments have agreed to ban the exporting of glass,plastic,paper,and rubber tires from January 2021,so we need to start treating these waste items as the ‘renewable resources’,” explain Sahajwalla and Hossain.

E-waste contains potentially valuable sources of precious metals,including rare earth elements (REEs),as well as plastics and refractory oxides,which could be worth up to $65 billion if unlocked.The complex mixtures of materials,however,make recycling difficult.Conventional approaches heat e-waste to very high temperatures for an extended period,which can release toxic substances such as lead into the environment and pose health risks for workers.

Instead,Sahajwalla and her team at UNSW’s Sustainable Materials Research and Technology (SMaRT) Centre have come up with a unique approach,known as ‘microrecycling science’,which promises local recycling of mixed materials on a small scale.More importantly,microrecycling allows the capture of different valuable elements at different stages of the process.

“The concept [is for] microfactories [to] reform waste into value-added materials for re-use and remanufacturing,” say Sahajwalla and Hossain.“This decentralized model merges recycling with manufacturing.”

In the process,e-waste is melted and degraded,with different compounds or materials extracted or removed at different stages.For example,printed circuit boards (PCBs) can be microrecycled in a step-by-step process releasing tin-alloys at 500°C and copper-alloys at 1000°C,without generating toxic by-products.Other problematic waste materials such as glass,textiles,and plastics can be transformed into ceramic tiles for construction or feedstock for 3D printing.Silica,as well as MnO and ZnO nanoparticles,can also be generated from e-waste.The approach has the potential to reduce the amount of waste going to landfill and loss of valuable resources,while creating sustainable products.

“We have an incredible opportunity to solve numerous existential problems at once: we can collectively address waste and recycling issues and lower our carbon footprint,while also enhancing our manufacturing capability,thus creating jobs and new supply chains,” points out Sahajwalla.

The researchers believe that microrecycling could launch a whole new ‘green materials’ movement where waste is used as a renewable resource for manufacturing.The SMaRT Centre is aiming to create compact,modular MICROfactories® which can transform waste into valuable products close to the waste source.

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