Waste Tyres

16 May 2017
tyres

THE PROBLEM

  • Waste tyres - Worldwide, over 1.2 billion used tyres are thrown away annually and at least four billion or so have accumulated in landfills and stockpiles. Such vast volumes of waste tyres not only pose a risk to human health and the environment but represent a significant waste of a potentially valuable carbon-rich resource. In landfills, waste tyres are not readily biodegradable and risk leaching toxic chemicals into the surrounding environment and stockpiled tyres pose a serious fire risk, as tyre fires are long burning and emit hazardous fumes. Although waste tyres are a complex and technically challenging waste stream, their composition and its high calorific value – a typical tyre has a carbon content of ~ 81.2 wt% [i]and a hydrogen content of ~ 7.2% - means they are of considerable interest for resource recovery. Yet, despite considerable research and numerous technological developments, there are few ideal processes for the cost-effective recycling of waste tyres, and recycling rates are low.

THE SOLUTION

  • What we making, some examples: ‘green steel’, silicon carbide (SiC) nanofibre/particle composites (with e-waste glass), activated carbon, carbon black. SiC/Si3N4 nanocomposites

What is ‘green steel’? 

Professor Veena Sahajwalla’s breakthrough ‘green steelmaking’ process leverages high temperature reactions in electric arc furnace steelmaking to transform waste tyres and plastics into high quality steel. By focusing on the evolution of carbon properties at high-temperature conditions, Prof. Sahajwalla completely overturned how the properties of carbon-bearing materials are understood, and bridged the gap between both pure and applied research and research and industrial application. ‘Green steelmaking’ simultaneously absorbs one of the world’s most problematic wastes and improves furnace efficiency, thereby reducing costs and power usage while delivering meaningful environmental gains. The commercialisation of the process, in Australia and overseas, has demonstrated the multiple benefits of going beyond conventional recycling processes by considering the composition and behaviour of waste streams at their molecular level. Professor Sahajwalla has subsequently opened up numerous new pathways for the transformation of complex and problematic waste streams into practical, commercially viable ‘green materials’ for production. She is currently pursuing highly original research to develop an atomic, molecular and micro-level understanding of various waste streams -- and is investigating the behaviour of those wastes at high temperatures – with promising results. This paradigm shift in the science of waste reprocessing overcomes the limitations of traditional recycling processes that rely on the costly, technically challenging separation of materials into single streams for reprocessing back into their original form, often with a loss of quality and integrity.


 

[i] Yeshui Zhang, Paul T. Williams, Carbon nanotubes and hydrogen production from the pyrolysis catalysis and or catalytic-steam reforming of waste tyres, Journal of Analytic and Applied Pyrolysis, 122 (2016), 490-501, pg 490