The Issue

A by-product of wastewater treatment processes is biosolids that consist of treated and partially treated sewage sludge. Biosolids have traditionally been transported to regional areas for agricultural use as they are rich in nutrients that can improve soil conditions. However, increasing disposal costs and stricter environmental regulations regarding the use of biosolids has made this disposal management technique less attractive for authorities. 

This was the case at the Loganholme Wastewater Treatment Plant (WWTP) where six trucks were making 300km-long round trips to transport biosolids to the Darling Downs region each day. This was costing Logan City Council and its community about $1.8 million per year.

Our Solution

To address this issue, we collaborated with delivery partners Logan Water, WSP, Cardno now Stantec, and Pyrocal, to design and construct Australia’s first biosolids gasification facility at the Loganholme WWTP. 

The facility processes sewage sludge by dewatering it in a centrifuge, drying it in a paddle dryer, and treating it with high temperature in a low oxygen gasifier. This process produces biogas with recovered energy from the biogas used to power the drying and heating processes.

The gasification facility is energy neutral, with 70% of the energy in biosolids recovered and reused, and the remaining energy requirements met by a 1,000kW onsite solar array. The gasification facility produces a biochar that contains nitrogen, phosphorous, and potassium.

The Benefits

Biosolids gasification benefits water utility providers, customers, and communities by:

  • Recovering energy from waste
  • Reducing energy consumption
  • Removing carbon and binding heavy metals which reduces carbon emissions
  • Destroying persistent organic pollutants and micro and nano-plastics
  • Complying with environmental regulations
  • Reducing WWTP operating costs
  • Reducing community impacts associated with traditional biosolid disposal transportation
  • Producing environmentally friendly biochar for agricultural and household gardening use.
Cost

The $28 million Loganholme Biosolids Gasification Facility was commissioned in April 2022. It was jointly funded by Logan City Council and a $6.2 million grant contribution from the Australian Renewable Energy Agency (ARENA).

Industry application

This innovative biosolids gasification solution can be used by water utilities to transform wastewater by-products into biochar, an environmentally friendly material that can be beneficially reused for agricultural and gardening purposes. The technology also has applications in other industries. For example, biochar can be added to some building materials, such as bricks and concrete, to improve their strength characteristics.

Read our Case Studies here

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