Hydraulics drive a new benchmark for waste management

In 1998 the seven local Perth councils comprising the Southern Metropolitan Regional Council (SMRC) sent 87% of all domestic waste to landfill. By 2006, this number has been reduced to 30%, due to a new state-of-the-art waste management facility - and 16 Hagglunds hydraulic drives.

The SMRC waste management facility consists of three separate plants - an in-vessel composting facility for the green bin, a materials recovery facility for the recycling bin and a processing facility for green waste.

Stuart McAll, CEO of the SMRC, travelled the world to find the best available technology for the plant. "I found the in-vessel composting facility in Atlanta, USA," he recalls. "The key advantage of this technology is that it doesn't rely heavily on people changing behaviour. It turns about two thirds of the waste that people put in the green bin into compost".

The in-vessel composting facility is claimed to be the second largest of its kind in the world and it consists of two drums, each 78 m long and 4.6 m in diameter. The waste comes on one end and the drums' revolving movement moves it to the other end in about 24 hours - by which time it is converted into compost. Each drum is driven by eight hydraulic drives from Hagglunds.

"When we met the SMRC for the first time," Brendan O'Brien of Hagglunds recalls, "all minds were pretty much set on a traditional girth gear solution with electromechanical motors. But the solution we presented was far superior in key areas such as construction cost, energy efficiency, reliability and durability."

The hydraulic drive solution has no need for gearboxes, couplings, clutches, etc. It is much simpler than the electromechanical solution and in this case superior in key areas such as construction cost, energy efficiency, reliability and durability. Without full face contact, traditional girth gears wear and tear relatively quickly. The friction wheel solution chosen by the SMRC is estimated to last 194 years.

The hydraulic drives are also a major contributor to the energy savings obtained. The plant is using 40% less energy than estimated.

The facility now has a waste recovery rate of 70%, produces almost 80,000 tonnes of compost and landfill is being reduced by more than 100,000 tonnes per year. Preliminary testing with the compost has seen farmers increase their yield by 40%.

"Obviously, we are proud and happy that we have been able to reduce landfill by more than 100,000 tonnes per year. But within the next 20 years we are hoping to get rid of landfill altogether. This would be possible with a combination of better waste management and more environmentally friendly manufacturing technology," concludes Stuart McAll.