It’s a shame to waste anything, especially when so much energy is embedded in the stuff we send to landfill. Craig Eyes previews an innovative residual waste gasification-to-energy project he’s working on in Victoria.

To introduce new technology and make any large project work successfully in Australia is not for the faint-hearted. Many factors have to be analysed and all the technical, commercial, location, community and environmental aspects must align to achieve a positive outcome.

Many eyebrows are raised by consultants when gasification is mentioned as it is not as common as other types of thermal waste-to-energy technologies.

However, gasification has been around for more than 100 years and is commonly utilised in large-scale industrial and chemical plants that operate on a range of feedstock including household, hazardous and medical waste. 

The development team at Recovered Energy Australia (REA) was introduced to a proven waste gasification-to-energy technology while working on a bioenergy project in 2015. More than 30 plants are operating throughout Asia and the Middle East, with another plant nearing completion in Indonesia. The oldest plant has been in operation for more than 15 years.

As populations grow and increased amounts of waste are generated, the constraints of limited landfill space have pushed governments to search for new solutions for waste that are consistent with the principles of the circular economy. Waste-to-energy can be part of the overall solution, where the energy embedded in waste is recovered and inert materials such as metals can be recycled.

Don’t call it rubbish

A waste gasification-to-energy project REA is proposing for Laverton North, Victoria, will take the household rubbish from the residual waste bin after it has been separated at the source – it does not aim to undermine good recycling practises.

The REA plant will process 600 tonnes per day of non-recyclable residual household waste that would normally be disposed to landfill. No pre-treatment is required before feeding the waste into the two-stage continuous gasification plant.

The technology includes six 100-tonne-per-day vertical and rotating gasifiers in three lines, with a secondary oxidation or “syngas” chamber. The waste does not burn in the gasifier as the air is controlled. The modular and scalable design builds in redundancy and will allow flexibility for future projects to be built in regional Australia at a smaller scale, with gasifiers from 20 to 150 tonnes a day.

A vertical gasifier at the plant is expected to operate at 850oC.

There are many benefits in the design of the vertical gasifier, which operates at 850oC – there is no requirement for auxiliary fuel such as natural gas, and waste is evenly mixed and heated as the chamber rotates. When air is added in the secondary chamber the syngas ignites and the temperature reaches between 1,100-1,200oC for two seconds. This is sufficient to maintain almost complete combustion of all organic residuals in the syngas.

The heat produced is recovered in the boiler for production of 15MW of baseload electricity in the steam turbines for distribution into the local grid. As more than 50% of the waste is organic material this translates into that portion of the electricity generating renewable energy which is eligible to create large-scale generation certificates (LGCs). There is also potential to supply heat/steam to nearby industrial factories to further increase the thermal efficiency of the plant.  

There is continuous online monitoring and flue gas emissions are at the lower end of the level which is permitted under the strict European Union directive. The flue gas treatment and clean up equipment is commonly installed in many industrial operations worldwide and includes an acid gas scrubber, activated carbon injection and bag house filter. By controlling the atmosphere in the gasifier there is less nitrogen and oxygen available, which significantly reduces the opportunity for the formation of NOx, SOx, CO2 and fine particulates.

About 15% of inert materials that end up in rubbish bins – such as bricks, ceramics, glass and metals – are recovered from the gasifier and this material is suitable to be recycled for road base or in an asphalt plant. The fly ash from the bag house is stabilised and only 3,600 tonnes sent to an appropriately licenced landfill each year, or 98% diversion from landfill.      

The Laverton North site is in a heavy industrial zone with the nearest residents over 1.7km away. The area is recognised by the Victorian government as a “waste and resource recovery hub”. A planning permit was approved in March 2019 and pending the approval of EPA Victoria REA expects a two-year construction period with commissioning in early 2022.

REA has engaged with many community groups with overall support shown for a better solution to landfill, which emits odours and leachate and requires long term post closure management along with the associated costs and the increasing landfill levy. The relatively small-scale gasification plant will divert 200,000 tonnes per annum of waste away from landfill. A health impact assessment of the gasification plant highlights no risk to health from emissions, odours, noise or water.

The technology includes six 100-tonne-per-day vertical and rotating gasifiers in three lines, with a secondary oxidation or “syngas” chamber.

What’s the fuss?

Many local government councils concerned about a “climate emergency” support zero waste to landfill may have set themselves renewable energy targets. This increased focus on the environment is positive news for the planet and waste-to-energy. Greenhouse gas emissions are substantially lowered by changing from landfill to waste-to-energy. Compared with landfill, the Laverton North plant will reduce CO2 emissions by 62%. This highlights that waste-to-energy is the preferred alternative disposal option in a carbon constrained environment.

As a local solution to a local waste problem, the gasification plant will handle the waste from about four nearby councils and reduce trucking distances. Importantly for ratepayers, the waste processing fee is comparable to landfill costs and becomes an attractive financial proposition for councils seeking a better environmental solution for disposing of residual household waste. 

The gasification technology can process a range of feedstocks, including low calorific value waste. This means the plant is capable of processing food and green waste where councils have not implemented food organics and garden organics into their waste collection and so keeping with three bins rather than adding a fourth bin into the system.

REA is investigating further development opportunities across Australia and overseas for this proven and innovative technology to provide important solutions for two big global problems: waste disposal and energy generation.

Craig Eyes is director of Recovered Energy Australia. He has over 20 years’ international expertise in the energy industry, including both private and government senior business development roles.