The developers of a 36MW waste-to-energy project in Perth have seen the technology prove itself overseas and expect nothing less when it lights up here in 2021.
Is this the year Australia finally got tired of rubbish, or are we caught in a global swell against swill? Supermarkets no longer give away bags, drinking straws are disappearing from bars and manufacturers are promising to cut down on packaging. Any movement against rubbish is good news, but society will always produce mountains of the stuff. One way to reduce the amount of trash sent to landfill is to see it as treasure – which very simply describes the thinking of the waste-to-energy movement.
Compared with clean energy giants wind and solar, waste-to-energy is waiting patiently to prove its potential in Australia. In Perth, however, the wheels are turning. Australia’s first energy-from-waste facility, Avertas Energy, is under construction about 40km south of Perth in an industrial zone in Kwinana. On completion in 2021, owners Macquarie Capital and international funds management company DIF expect it to process 50 tonnes of waste an hour and turn out 36MW of power to the grid. Over a year, that’s 400,000 tonnes of post-recycle waste diverted from landfill in a city that produces 1.8 million tonnes of trash a year.
How it works
Avertas Energy will use moving grate combustion technology already operational in more than 2,000 similar waste-to-energy facilities around the world. The energy-from-waste process is largely self-sufficient, where combustion is initiated inside a furnace using natural gas until a desired temperature is reached and the waste takes over as the only fuel source necessary to sustain combustion. From then on, support fuel in the form of natural gas is used only in the event of a shut-down or operational issue.
The facility will include two independent lines of 130-square-metre ”moving grates” angled at 21 degrees, a design aimed at minimising the combustion of the waste material. Rubbish is pushed in at one end and consumed by flames as it slowly heads downhill. Each grate has four “lanes”, independently controlled for optimal combustion.
There are three main zones within a grate. In the first zone, the primary function is to dry out the waste and initiate the release of volatile gases. The second zone is where the main combustion takes place and the third zone ensures the waste is completely burnt and then cooled. Temperatures inside the boiler where the waste is initially combusted will reach at least 850oC to ensure destruction of furans and dioxins. Temperatures will vary depending on the fuel calorific value and can reach over 1,000oC.
The heat is used to produce steam that drives an air-cooled condensing turbine. Metals are sifted away and ashes are used as construction materials. Gases are treated to remove pollutants that are stored for disposal and re-use. The plant will run 24 hours a day, with individual lines closed for routine maintenance three to four times per year. Operating at capacity, the owners expect about 30.3% gross electrical efficiency.
Contacts for municiple solid waste currently include the City of Kwinana, the Rivers Regional Council, which incorporates the City of Canning with the Cities of Armadale, Gosnells, Mandurah and South Perth, and the shires of Murray and Serpentine Jarrahdale.
The facility will benefit from flexible waste fuel sources as the state government’s waste strategy 2030 is progressively implemented, where food organics, green organics and greater levels of recyclable material are slowly removed from the waste stream.
World of waste
Energy from waste technology has matured and is used around the world and is now widely recognised as being safe and environmentally positive. European experience has demonstrated that waste-to-energy can play a major role in the reduction of landfill, with data from the Confederation of European waste-to-energy plants (CEWEP) showing substantial reduction in landfill over the past 14 years.
On a global scale, the Avertas Energy facility is a medium-sized plant. The planning for the Singapore Integrated Waste Management Facility will likely be the biggest in the world, with eight lines capable of 35 tonnes an hour. The plant is in the procurement phase and will be built in two stages.
Materials that can be recycled are separated so they can be reused, and only non-recyclable material is used in energy from waste production. By using non-recyclable material, Avertas Energy hopes to reduce carbon emissions to the atmosphere that would otherwise come from coal or gas fired power and divert waste from landfill. By not using recyclable materials they can be re-used for other more valuable purposes.
At similar facilities operating overseas the ash by-product is primarily used as a construction aggregate for use directly in roadways and as piping bedding material and for inclusion within other manufactured items such as a concrete additive or in blockmaking. For the Perth project, the objective is to have the ash re-used as a construction material – subject to obtaining regulatory approvals.
Ferrous and non-ferrous metals can be recovered post-combustion and recycled, increasing recycle rates and reducing greenhouse gas emissions through avoidance of new metals production and associated energy consumption.
The international consortium building and operating the facility includes Spanish infrastructure and renewable energy company Acciona, with technology provider Keppel Seghers, and waste management and energy services company Veolia. The project has also attracted funding from the CEFC and ARENA. Avertas Energy is negotiating an offtake agreement but expects to send about 25% of electricity into the South West Interconnected System. The facility will service an area with a radius of about 50km, but there are opportunities to transport waste from locations farther away that may otherwise have to travel to landfill at Bannister or Dardanup, both further south of the city.