Each year, 20 million tonnes of garbage – around 40% of Australia’s total waste – ends up in landfills around the country. Here it produces methane gas, which is 30 times more harmful to the atmosphere than CO2. It risks contaminating surrounding land and water and – of course – takes up a ton of space. Moreover, as landfill has been historically cheap, these sites become the final resting place for materials that could otherwise be recycled. Alex Reilly, a mechanical engineer in our Melbourne office, and a handful of his colleagues in our environment and resources team saw a link while they were discussing another pressing issue - the trade offs in shifting towards renewable energy.
How does Australia balance the need to move to cleaner and more reliable energy solutions over the next ten years? - Alex Reilly
The conversation moved quickly - from pumped hydro to battery storage to some of the waste-to-energy technologies currently reaching maturity in parts of Europe. Recently, landfill levies have begun to rise in Australia to incentivise recycling while also reducing stress on the landfills next to our growing cities.We’re now begin to see the cost of these levies to trickle down to councils, businesses, and families. Could this weight of this added financial strain be enough to tip the scales on how we choose to deal with our waste?
Across Europe, over 80 million tons of waste are diverted from landfill to facilities where its embodied energy is recovered as electricity, heating, and cooling. Not only does this drive down the physical footprint of this waste in a part of the world where space is at a premium. It reduces the carbon footprint associated with generating these utilities through other means as well. Countries like Denmark, Germany, and the Netherlands currently landfill less than 3% of their municipal waste. In comparison, this number is 40% in Australia. To satisfy its energy needs, Sweden is famously a net importer of trash. There are several ways to recover energy from waste: anaerobic digestion, gasification, or pyrolysis. The most common is incineration: burning solids at high temperatures to release their embodied energy as heat. The food scraps, paper, and plastics which makeup the majority of household rubbish burn readily. Non-combustibles, like glass and metal, can be recovered from the ash.
In the most simple version of the process, the heat produced is used to generate steam to power turbines and generate electricity. More complicated combined heat and energy capture schemes employ boilers to store some of this heat as hot water. In trigeneration, an additional stream of cold water is generated via absorption chillers. The result is a three-utility output – electricity, hot water for heating, and cold water which can be used for air conditioning or even refrigeration. To be feasible, a waste-to-energy solution must overcome two main obstacles. First, the waste must be sorted to ensure efficient burning. For this reason, waste-to-energy is best coupled with a robust recycling program. There’s also the cost of transporting the waste to where it’s incinerated. Both challenges, however, can be alleviated if you locate your facility next to where that waste is produced and sorted. The unique challenge of finding land next to waste-producers and energy-consumers makes waste-to-energy solutions particularly applicable to urban renewal projects.
Visible through the window of our Melbourne office, where Alex and his colleagues were conducting their brain storming session, was the perfect site for a case study. Straddling the south-eastern bank of where the Yarra – where the river meets Port Phillip Bay – Fisherman’s Bend is Australia’s largest urban renewal project. The site spans 480 hectares, five precincts, and is shared across two municipalities: the City of Melbourne and the City of Port Phillip. By 2050, the mixed-use community will house 80,000 residents, as well as buildings, leisure centres, and other commercial and industrial facilities. This, combined with the availability of land, is what makes the site particularly appealing.
The beauty of mixed-use is that you have different user types drawing power at different times throughout the day. - Alex Reilly
Your residential user draws a lot of energy at morning and night. An office or mall will draw most of its power throughout the day. ‘To power either type of building on its own can be quite expensive. But on a precinct scale, those demands flatten out. A centralised solution, like district scale trigeneration, becomes a lot more efficient.’
To validate this hypothesis, the team built a thermal model to predict the utility demands of Fisherman’s Bend at the end of the first phase of construction (2037). They then allocated different user types to different parts of the model to determine the different electricity, heating and cooling usage profiles through the day. By weighing these against the waste predicted to be produced on site, they could compare the cost and benefits of this type of integrated solution against what other treatment and utility option where available.
We looked at trigeneration at both the building and the precinct scale to determine what scale something like this makes sense. We ended up going as big as we could go – supplying district heating, cooling, and hot water to the whole of the precinct. - Alex Reilly
The result was a conceptual 600-tonne per annum waste-to-energy facility, capable of providing the district with about 20% of its electricity requirements. Even more attractive, however, were the savings projected from the optimisation of transport and disposal of waste. The team also found precinct-scale trigeneration could bring broader community-level benefits. Traditionally, apartments in Australia are heated and cooled using a reverse cycle split-system which use electricity relatively inefficiently. This can be particularly costly in a city with seasonal temperature swings as dramatic as Melbourne. It often means urban renewal projects have to ‘patch’ buildings with more expensive interventions to achieve good environmental ratings. Rhys Anderson, who leads our Water team in Melbourne, was particularly intrigued by the aggregate social and economic pluses. He sees great potential for centralized heating-and-cooling to help an entire community earn a Green Star rating together at a greatly reduced cost.
Imagine being able to help an entire precinct earn a Green Star rating without building scale intervention. - Rhys Anderson
The team has delivered the findings of the work and shared them with colleagues around the world, including the model developed for the study. Applications of this work have been identified across Australia and the world, with this research providing a valuable launch pad to implementing waste, energy and water solution to the urban development challenge facing many cities. While the sheer scale of the Fisherman’s Bend project does make it a particularly unique, the team have since shown how particular principles of the process can be scaled down and applied across smaller precincts.
True to Alex and the team’s predictions, the economic and political barriers to waste-to-energy are beginning to erode across Australia. Kwinana, Australia’s first waste-to-energy facility, is expected to commence operations by 2021 . A handful of similar facilities have also been proposed around rural Victoria and New South Wales. Alex, Rhys, and the team, hope their research will open the doors so that city dwellers – who represent 89% of the Australian population — can realize the benefits of this type of scheme as well.
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