Harnessed waste heat from cremations, sewage sludge could soon power our homes
By Bianca Hall in The Age
Cremating bodies is an energy-intensive process: the sheer amount of energy required to cremate an individual body can generate more than 250kW in wasted heat.
But what if we could harness that excess heat, and use it to create a renewable energy that could power our homes and businesses?
An Australian start-up has completed a series of successful trials of what the team behind it says is a commercially viable electricity engine that runs on waste heat – including a successful “proof of concept” trial at a Victorian crematorium.
“Cremations are an exothermic process in that they actually give off more energy than they soak up,” said Capricorn Power chief executive Geoff Andrews.
Crematoriums can use 600kW in energy to power a cremation, with 250kW of that power considered “excess” and disappearing up flues as waste heat.
After the crematorium trial, Capricorn Power – a small start-up based in Victoria – successfully tested an updated prototype engine over 400 days on a purpose-built natural gas burner, to establish its commercial viability.
In time, Andrews said, the engines could be used to heat biological waste such as sewage “sludge”, nutshells, and biowaste from piggeries and abattoirs to more than 400 degrees, and transform it into low-emissions energy.
“There’s plenty of waste material around; enough that we can actually be stringent or fussy about not taking a resource that could have a high-value use,” he said.
The prototype Barton Engine fits inside a shipping container and, its proponents say, could be attached to businesses to take biowaste and transform it into portable energy supplies that power the business producing the waste.
“The advantage of having an engine that can be efficient and small is that you can put the generator where it’s required and where electricity is being used,” Andrews said.
As the Albanese government’s legally binding 2030 emissions reductions targets inch closer, the independent Climate Change Authority has increased pressure on the government and every sector of the economy to reduce emissions.
The authority, led by former NSW treasurer Matt Kean, on Thursday outlined its recommendations on how the six highest emissions-producing parts of the economy should reach net zero by 2050.
It found managing Australia’s waste – particularly organic material in landfill, which produces methane that accounts for about 75 per cent of emissions from the waste sector – would be crucial in limiting the dangerous release of greenhouse gasses.
Emissions from sewage systems, biological (including medical) waste, and thermal waste treatments from incinerators comprise another 20 per cent of emissions from waste, the report said.
“A mix of technologies for the processing of organic waste will be required, and these are likely to consist of composting, anaerobic digestion and combustion of waste to generate energy,” the report found.
The Victorian government has thrown its support behind waste-to-energy projects, and announced in July it would contribute $8 million to 24 projects, which it says could boost the state’s renewable energy capacity by 6.82 megawatts, which is enough to power 3410 homes with renewable energy.
Yarra Valley Water in April announced a new $48 million Lilydale facility would start accepting commercial food waste from as early as 2025, using “digesters” rather than a gasifier or incinerator process, to break down the food and create biogas.
The NSW government has banned the development of thermal energy from waste facilities across greater Sydney, with limited exceptions. Waste to energy projects are instead limited to four precincts: around Parkes, the Richmond Valley, the Southern Goulburn and West Lithgow.
Capricorn Power, which has a patent pending on its Barton Engine, co-funded the pilot project with the Advanced Manufacturing Growth Centre, and hopes to secure investment to push its engines into the market.
Waste -to-energy (Municipal Solid Waste)
How waste-to-energy plants work
Waste-to-energy plants burn municipal solid waste (MSW), often called garbage or trash, to produce steam in a boiler, and the steam is used to power an electric generator turbine.
MSW is a mixture of energy-rich materials such as paper, plastics, yard waste, and products made from wood. For every 100 pounds of MSW in the United States, about 85 pounds can be burned as fuel to generate electricity. Waste-to-energy plants reduce 2,000 pounds of garbage to ash that weighs between 300 pounds and 600 pounds, and they reduce the volume of waste by about 87%.
The most common waste-to-energy system in the United States is the mass-burn system. In this system, unprocessed MSW is burned in a large incinerator with a boiler and a generator to produce electricity. A less common type of system processes MSW to remove noncombustible materials to produce refuse-derived fuel (RDF).
Generating electricity in a mass-burn waste-to-energy plant is a seven-step process:
- Waste is dumped from garbage trucks into a large pit.
- A giant claw on a crane grabs waste and dumps it into a combustion chamber.
- The waste (fuel) is burned, releasing heat.
- The heat turns water into steam in a boiler.
- The high-pressure steam turns the blades of a turbine generator to produce electricity.
- An air-pollution control system removes pollutants from the combustion gas before it is released through a smoke stack.
- Ash is collected from the boiler and the air-pollution control system.
Last updated: December 21, 2023.
Burning rubbish to create energy could end landfills. But some worry where Australia’s new path is leading
Some conservationists believe the ‘incineration industry’ is trying to gain a foothold in Australia and say the trend will end up damaging the environment
in the Guardian
Australia’s first major waste-to-energy power plant has begun accepting rubbish, marking the start of a contentious nationwide shift towards burning household refuse to generate electricity.
At least 10 developments are under way across the country, sparking concern from some conservationists who argue the trend will be environmentally damaging and at odds with plans to develop a circular economy.
Local councils have started sending truckloads of garbage to Kwinana EnergyRecovery facility, south of Perth, as the country’s first commercial-scale project heads towards full-scale operation.
The Kwinana plant is designed to burn up to 460,000 tonnes of non-recyclable waste annually – about a quarter of the amount Perth sends to landfill.
Another 300,000-tonne-a-year generator is under construction just down the road at East Rockingham. Four licences to build major waste-to-energy facilities have been issued in Victoria and there are proposals in New South Wales, Queensland and South Australia. Combined, the projects in development would have the capacity to incinerate 2m tonnes of waste a year – a quarter of what Australian households throw away.
Waste-to-energy has experienced a surge of interest in Australia as landfills near capacity. Proponents say it could mean an end to landfill, and that air pollution and ash can be managed under existing environmental regulations.
But not everyone is convinced. The environmental group Zero Waste Australia calls the approach “the most polluting and expensive way to generate energy and manage waste” and has raised concerns about the environmental and health consequences.
Jane Bremmer, the group’s campaign coordinator, says the number of waste-to-energy proposals is “gobsmacking”, and a sign the “incineration industry” is trying to gain a foothold in Australia as it was being pushed out of Europe, where some plants are being decommissioned.
Better than landfill?
The City of Gosnells, a council with 130,000 residents south-east of Perth, is among 10 local governments sending waste to Kwinana to be burnt.
The city’s mayor, Terresa Lynes, says the change comes after a decade of planning, and a long-term contract with the facility shields ratepayers from increasing and unpredictable landfill levies.
“This is the end of landfill for the City of Gosnells,” she says, with power produced an added benefit. The council is focusing on recycling and green waste too, she says, emphasising waste-to-energy is only “part of the solution”.
In recent years, circular economy and waste policies in Western Australia, Victoria, NSW, Queensland, South Australia and Tasmania have preferred waste to energy over landfill for disposing of non-recyclable waste. However, the practice is prohibited in the ACT.
Jennifer Macklin, a circular economy researcher with the Monash Sustainable Development Institute, says the underlying principle of a circular economy is to keep materials circulating at their highest value for as long as possible, for example through repair and reuse.
The waste-to-energy process – which typically involves burning non-recyclable waste in large furnaces at high temperatures to generate electricity or heat – is the “lowest value way of circulating” because the value in the materials is lost, she says.
Using the energy “definitely offered a small benefit over landfill”, Macklin says, but poses a risk to higher-value reuse and recycling efforts.
She says evidence from other countries indicates recycling rates can plateau after the introduction of waste-to-energy plants, partly because once the infrastructure is built “you’re locked in feeding it”.
The arrival of waste to energy can also dampen motivation and participation in reuse and recycling at the household, organisation and even government level, she says.
The NSW chief scientist, Prof Hugh Durrant-Whyte, provided independent advice on the technology to the NSW government in 2020. He said waste to energy was well established in Europe, but as some countries improved their waste reduction, sorting, reuse and recycling efforts, some facilities were being decommissioned. “They’re shutting them down, not because of air emissions but because they no longer have the waste to actually burn.”
Across Europe, there are about 500 waste-to-energy plants, but circular economy efforts have led some countries to reduce their reliance on the technology. Denmark, for example, plans to reduce waste incineration capacity by 30% between 2020 and 2030.
Is power from plastic renewable?
Gayle Sloan, CEO of the Waste Management and Resource Recovery Association, says waste combustion is better for the climate than creating methane in landfills. “We shouldn’t be throwing things in the ground. If we can’t recover it, we should be using it for energy,” she says.
Government policies support the approach as an option for residual waste – the materials left over after recyclable, green and food wastes have been removed. In many states, that’s the “red bin” waste, containing soft plastics, nappies and synthetic textiles.
In Australia, energy produced by burning plastics is not renewable even though projects promote their power as clean and green.
Acciona, owner of the Kwinana facility, says converting waste into energy “addresses both the waste crisis and the need for clean, reliable power in WA”.
The WA facilities – Kwinana and East Rockingham – both received funding from the Australian Renewable Energy Agency (Arena).
An Arena spokesperson says while the projects demonstrated lower emissions compared to landfill, not all waste-to-energy facilities were “renewable”, and the agency did not intend to support any new funding applications. “Arena’s investment priorities do not align with investing in further projects incinerating waste for energy.”
Durrant-Whyte says: “I would hesitate to call it renewable energy. But is it better than digging a hole and putting it in the ground? Yes.”
Bremmer says contrary to industry claims, waste-to-energy doesn’t divert waste from landfill. Combustion converts the material into smaller volumes of toxic waste ash, which is then disposed of as hazardous waste.
A better solution would be to shift away from a focus on disposal and move towards a more sustainable, zero waste model, she says.
“The industry is really being pitched as being part of a circular economy, but it’s a linear process.” Those materials are lost forever, Bremmer says. “You can’t get that back and reuse or recycle it. It’s gone.”
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