WOLLERT LANDFILL IS CLOSED TO THE GENERAL PUBLIC UNTIL FURTHER NOTICE, DUE TO GOVERNMENT COVID LOCKDOWN
Situated in Melbourne’s northern fringe, Hanson’s Wollert Renewable Energy Landfill has provided households and commercial, industrial and demolition businesses with a facility to safely dispose waste since 2000. The Wollert facility is an excellent demonstration of Hanson’s commitment to developing innovative solutions that exceed the landfill best practice standards expected by the regulatory agencies, the Victorian Government and the community.
The Wollert Renewable Energy Landfill site is a repurposed former quarry, where tonnes of waste are deposited into cells that are then capped at the end of their landfill life. These caps are built using a ‘regulation’ layer of quarry scalps, processed clay (GCL), a linear low-density polyethylene (LLDPE), membrane, a layer of cushion geotextile, and an additional one-metre bed of quarry scalps as a growing medium.
Wollert landfill had found an innovative way to improve its environmental impact and service to the community. In 2016 it converted the capped portion of the site into a solar farm by installing more than 380 solar panels. This solar farm has the ability to generate up to 100 KW per annum. The solar powered installation operates independently, off the grid; exporting all the power it produces.
This green power production is further boasted by the onsite green power station that produces electricity from the landfill gas (methane) emitted from the decomposing waste. This electricity is then fed into the grid, providing enough energy to power to more than 5000 homes.
Since landfill sites are typically unstable and difficult to build on, once decommissioned they are often transformed into parks or other types of green space. Some of the best examples provide new habitats for native species.
At the Wollert Renewable Energy Landfill site, Hanson found a way to establish native habitat and improve biodiversity outcomes early. In 2010, with approval from the EPA, the site trialled a ‘phytocap’ (an evapotranspiration cap).
Hanson’s Land and Mineral Reserves Manager Daniel Fyfe says, "Establishing a phytocap is an innovative opportunity to develop a habitat for native flora and fauna utilising local indigenous species and meet the EPA requirements for capping and closure of landfill cells."
This initiative utilises deep beds of locally sourced soils, planted with suitable indigenous grasses, bushes and trees. The deep soil layer acts as a sponge for rainfall in winter. The plants transpire the moisture back to atmosphere during the summer months and preventing rainfall penetrating into the waste mass and the production of leachate.
The trial was successful; hundreds of trees, bushes and native grasses are now very well established, and the phytocap has been colonised by flocks of birds, insects and other fauna, including healthy mobs of eastern grey kangaroos.
Read more about Hanson’s other ‘green’ initiatives here:
Hanson Trials Recycled Glass in Concrete
Sustainability in a Sunburnt Country
Wollert Landifill is operated as a renewable energy landfill with leachate recirculated back into the waste. This has resulted in a significant volume of methane gas being generated and then recycled as an alternative source of energy.
In fact, 1.4 million cubic metres of methane is captured at the landfill each month.
This represents approximately 85 percent of the total methane gas generated at Wollert and which is used to produce 55 million kilowatt hours of electricity each year, or enough energy to power 10,000 homes.
A Carbon Footprint study undertaken at the landfill indicates Wollert has a better greenhouse gas performance than many high-technology disposal systems proposed for Victoria. For more information, read our Comparative Greenhouse Gas Life Cycle Assessment.
Progressive rehabilitation at the Wollert Renewable Energy Landfill is very important to not only provide a long-term stable land form but to also minimise the off-site impacts of the waste.
The landfill is constructed in Cells that hold about 500,000 tonnes of waste and take 18 months to fill. Once a cell is complete, the landfill gas collection system is installed before any permanenet capping is in place. This allows Hanson to start collecting the methane as it begins to be generated and minimises odours off-site. The uncapping cell is used to spray leachate on during the warmer months and this helps to break down the waste.
Every two years, the completed cells are capped with a composite layer of clay and plastic to completely seal the waste. This prevents further leachate generation and allows the native vegetation to be planted and restore the site.
In time parts of the rehabilitated landfill may be open to the public for passive recreation. Then the benefits of the new indigenous plantings will be shared by the community and native animals and birds.
A lining system that uses a combination of two-millimetre thick High Density Polyethylene and one-metre thick compacted clay is used through Wollert's landfill area.
Through this, Wollert has been able to successfully provide long-term protection and quality assurance for the local groundwater supply.
As part of Wollert Landfill's Environmental Management System, water quality is also regularly tested on-site to monitor and report quality levels.
Wollert has a comprehensive approach to ensuring all asbestos is handled at the highest environmental standard.
This includes photographing eighty-five percent of all commercial asbestos loads to carefully monitor the delivery process. These photographs are also passed back to the customer if the waste is not properly wrapped and habitual offenders are banned from the site.
Wollert only accepts commercial asbestos materials that arrive with EPA Transport Certificates, wrapped twice in plastic, within strict weight restrictions and in a Ro-Ro bin so they can be slid on an angle into the landfill, rather than being dropped onto the ground.
In areas of the tip where asbestos is being received or handled, air-quality is monitored twice a year. To date, has asbestos fibres have never been more than 1/10th of the Occupational Health and Safety limits.
Asbestos is buried the day it arrives on-site and with the GPS coordinates of each asbestos load tracked, Wollert therefore has an ongoing record of exactly where asbestos is located within the landfill.
Hanson has started investigating the recovery of high heating value materials, such as plastics, from waste. This would involve sorting and separating some of the incoming waste streams in an automated plant. The sorted materials would be cleaned and baled and sent to a cement kiln in Tasmania.
Plastics, cardboard and timber are essentially interspersed in the landfill and the removal would not affect the production of renewable electricity at the site, but would provide a new source of energy recovered from the waste.
Hanson has been working with F-Cubed to develop a way of distilling leachate using Carocell solar panels. This produces a brine for reinjection into the landfill and an ammonia rich distillate which can be used to irrigate the grass growing on the cap. Because it is solar powered it has a very low energy footprint.
The project won an Innovation Award at the 2013 WMAA Landfill Conference and it is planned to build a larger scape prototype to prove the concept.