European cement kilns burn much more waste, but Geocycle Australia’s dewatering project is cutting edge.

If recovery of the embodied energy of a material is the most sustainable option for some
waste streams, why does Australia’s take-up of EfW projects fall so short? By Garth Lamb.

Members of the Waste Management Association of Australia’s Energy from Waste (EfW) division recently concluded they could no longer “think of any regulatory, policy or arbitrary barrier to sustainable EfW projects”.

There is growing consensus that recovering the embodied energy of the material is the most sustainable disposal option for some waste streams. Despite this, however, there are very few EfW projects in Australia.

What the nation does now have is an innovative pilot being undertaken by Geocycle, the alternative fuels arm of Cement Australia, at its Dandenong, Melbourne facility.

Geocycle has for 25 years collected waste materials such as solvents, greases, paints and various other high viscosity fuels, then blended them for dispatch to cement plants throughout the country, replacing coal for firing kilns.

In July, the company won a $250,000 grant under the Victorian Energy Technology Innovation Strategy to improve this process by extracting water from its alternative fuel products.

It is now piloting a process using a centrifuge and thin film evaporator to separate water from material with a high calorific value, such as solvents. Incoming wastes have water contents of some 35 per cent, but Geocycle will reduce that to about 10 per cent – both increasing the energy value of its products and improving transport efficiencies for their distribution.

“What we’re trying to do is take prescribed industrial waste (PIW) from a wider range, some of which would not be traditionally really suitable for the kiln…because of their sludgy properties and others, which are high water content,” explains Geocycle’s John Worsley.

Despite waste-derived fuels being used extensively to fire European cement kilns, the process Geocycle is pioneering involves a novel combination of existing technologies.

As well as state funding, the company has been awarded some $4 million under the Asia Pacific Partnership on Climate Change to help fund the almost $10 million project, including the dewatering unit and another improvement at the front end of the plant to shred drums of hazardous waste.

Rather than emptied containers (which often contain hazardous waste residues) being sent to a PIW landfill, the 44-gallon drums are now being fed directly into an auger shredder. The metal is then recovered from the blending tank using a series of magnetic conveyors, while the 100mm fragments are washed using water recovered from the dewatering process.

The recycled water will also be used in other process applications, such as for boiler make up water.

With the new systems in place, Geocycle could process 7,000 tonnes of PIW at the site annually, about 10 per cent of Victoria’s total. The company expects to have capital approved for the project to move beyond pilot stage by the end of this year.

More at: www.geocycle.com.au