Veolia Group’s Mechanical Biological Treatment facility is helping Sydney councils achieve the New South Wales Government’s diversion target of 70 per cent by 2021.
Approximately 240 kilometres from Sydney, NSW, lies the town of Tarago.
For two decades, Tarago was home to the adjoining Woodlawn Mine site. Men in high-vis jackets nestled deep within the Woodlawn open pit spent countless hours drilling for zinc, copper and lead until its closure in 1998.
Since 2004, global environmental services company, Veolia, has been working tirelessly to rehabilitate the site.
Veolia spent 10 years planning the international company’s new Mechanical Biological Treatment (MBT) facility, which became fully operational in July of this year. The $100 million investment required extensive planning approvals, community consultation and council collaboration. It now allows Veolia to compost a significant amount of Sydney’s waste for the mine site remediation.
But within this remediation project lies a greater environmental goal – to help the councils of Sydney meet their targets to divert 70 per cent of waste away from landfill by 2021.
Veolia’s NSW Group General Manager, Ben Sullivan, worked with company stakeholders to get the state-of-the-art infrastructure off the ground.
Ben explains that Veolia received planning approval for the Woodlawn MBT in 2007. But it took some years to get the tender right. In 2012, Veolia submitted its proposal to the Southern Sydney Regional Organisation of Councils. The plan was to take more than 100,000 tonnes per annum of the council’s waste, helping them meet their diversion targets.
The company submitted its design and solution for the MBT, and was awarded the contract by eight of the eleven SSROC councils (now six councils due to amalgamations) in 2013. The updated contract included plans for a second waste transfer station, before being separated and sent to the MBT facility. It also expanded the facility to receive waste from an additional consortium of five councils – the Northern Sydney Regional Organisation of Councils. This would allow the MBT to process around 144,000 tonnes per annum.
“Between 2007-12 it took an extensive amount of time to refine and really commercialise the solution. In parallel, the Environmental Protection Authority (EPA) and government targets were being modified around increasing the diversion rates, and the landfill levy was starting to increase,” Ben explains.
“So with these changes in mind, the Sydney councils started to look forward to find a solution to its putrescible waste. We have a fairly established kerbside system in Sydney, but it was the red bin that was going to landfill. Approximately 50 per cent of the red bin is food, and the rest is plastics and other material,” he says.
Ben says that by processing and separating the materials at the MBT, residents were able to keep their current recycling habits in place. He estimates Veolia is now responsible for processing 25 per cent of the putrescible waste in Sydney, which equates to about 750,000 tonnes per year. The new MBT will process 144,000 tonnes of the current volume and will divert approximately 50 to 55 per cent of the tonnes away from landfill, using the organic fraction as mine site rehabilitation adjacent to the Woodlawn Eco-precinct.
“This technology has formed the infrastructure part of Veolia’s environmental solutions for the past 30 years in Europe. We were able to leverage and transfer our knowledge and experience to the Australian operations, which had a similar mass balance in the waste stream,” Ben says.
The procurement process included the importation of four large rotating drums, of about 4.6m in diameter, which degrade the materials and prepare them for separation.
“The mining industry would be quite familiar with these drums but in the waste industry, it’s quite unique.”
Ben explains that Veolia transports the waste to the two waste transfer stations (located in Clyde and Banksmeadow, respectively) where they are stockpiled and compacted into a shipping container at a rate of 31.5 tonnes per container. From there, it is taken to Veolia’s Woodlawn Eco-precinct by rail, located 30 km south of Goulburn and 240 km southwest of Sydney.
“Moving waste by rail is quite unique, it keeps trucks off the road and the trains include about 55 carriages. Two trains a day leave Sydney to our Woodlawn facility.
“We then truck the last seven km from a purpose-built train site we constructed in a town called Crisps Creek up to the site,” he says.
Once the waste reaches Woodlawn, it is loaded into a pit where the first screening is undertaken and any items are removed that cannot be processed. A crane grapple then loads the rotating drums.
“This step is the first opportunity to spot anything that shouldn’t be there, such as a mattress or a tyre that won’t be able to be processed. The crane actually removes that equipment and that goes back to landfill,” he says.
Waste is then combined with air and water in the large rotating bio-drums to commence degradation and prepare for separation. Four drums, of about 4.6m in diameter, each process one tonne of waste at a time, which breaks down the waste over three to four days. It then undergoes anaerobic digestion within the drum, which breaks it down under heat before being placed into a series of conveyors and trommels to filter out any inorganic materials for recycling and recovery, including metals, plastic or paper.
Organic materials, which includes food and garden waste, is stockpiled in 45 rows in a 1.1 hectare shed for fermentation and maturation, preparing the compost for use in remediation on the old mine site.
“The materials sit there for four to five weeks and we pump air through that stockpile at around 70°C. This continues to accelerate that breakdown and degradation of the food and we make sure the heat and the moisture content is the right temperature.
“After four to five weeks through a front end loader, we then take that product outside onto a maturation pad, where it will again sit there for another 12 weeks. That produces a compost type product which is used within an adjacent company for the mine remediation.”
Residual waste, which includes ash and other non-recyclables, heads to a bioreactor. The bioreactor enables Veolia to rapidly stabilise waste by accelerating the waste decomposition process, while maximising landfill gas recovery, which extracts methane gas to convert the waste into energy and heat. The energy is then used to power more than 30,000 homes. He says non-ferrous metals are separated and sold on for recycling.
“We’ve effectively put in a series of gas wells and pipes as we lay the waste. When the waste breaks down in the bioreactor it produces methane and we extract that methane to power a total of 24 generators on site. Generally speaking, every tonne of biodegradable waste deposited will yield approximately 1.33MW of power.”
While the bioreactor has been generating energy for years, Ben says the company has bigger plans to expand its residual waste recovery and shred it into refuse derived fuel.
“We’re currently in discussions with Southern Sydney Regional Organisation of Councils and Northern Sydney Regional Organisation of Councils for an energy from waste project.
“We’ve got the concept design complete and we’re just working on the business case commercials on that.”
He says at present, the facility is diverting 50 to 55 per cent of its waste from landfill. If Veolia is able to recycle the residuals, Ben hopes this would increase the diversion rate by an additional 20 per cent.
As Stage 1 is complete, the team will be looking to complete Stage 2. The concept will see an additional four drums constructed, with the capacity to process 244,000 tonnes of waste, subject to additional contracts to be awarded to Veolia.
Read the full story on page 34 on Issue 14.