Logan City Council is on its way to creating an Australian first full scale biosolids (sewage sludge) renewable energy plant at the Loganholme Wastewater Treatment Plant (WWTP). Downer and ELIQUO WATER & ENERGY signed a contract for the design and supply of two large EloDry NT-48 sludge dryers for the project. These low temperature belt dryers will dry the dewatered biosolids prior to the gasification process. The drying and gasification will reduce the volume of produced biosolids significantly and lower the WWTP’s costs for solids disposal.
The Loganholme WWTP services about 300,000 people in Logan City and produces 34,000 tonnes of biosolids per year. Currently the produced biosolids are reused as a soil improver in agriculture about 300 kilometres away from its origin. The transport costs are currently around 30% of the WWTP’s total operating costs. Globally, biosolids management costs are rising due to increasing energy costs and population, tightening of regulations associated with reduction of greenhouse gas emissions and, when biosolids are disposed to land, managing persistent organic pollutants in soils.
The gasification process at Loganholme WWTP will reduce the volume of produced biosolids by 90% and produce a safe and environmentally friendly biochar, which can be used as a sustainable harmless soil conditioner.
In 2019, the Australian Renewable Energy Agency (ARENA) provided a $6.2 million grant to Council to help develop the $26 million new gasification plant at Logan WWTP.
The plant uses the Pyrocal CCT gasification process. The gasifier works by creating gaseous fuel from the biosolids which have been dewatered, dried and treated at high temperatures. The material produced is a biochar containing carbon, phosphorus and potassium. Logan City Council is investigating opportunities to market the biochar once the facility becomes operational. The entire process was trialled and demonstrated successfully in the past year and now Council and its delivery partner Downer are starting construction of the full-scale facility in 2021.
In the setup of the gasification process, the dryer forms a crucial link between the dewatered biosolids and the inlet of the gasifier. By drying the dewatered biosolids with recovered thermal energy from the gasification process, the system will work on a 70% energy autonomous basis. The remaining 30% of required energy is sourced from an onsite solar power system (being constructed).
According to Matt Thomson, Operations Manager at Downer, “The EloDry® low temperature sludge dryers were selected based on their high energy efficiency and proven performance with other systems that also includes thermal heat recovery. By working with ELIQUO we have secured both dedicated knowledge about heat recovery and delivery of a proven drying concept.”
The project will be implemented by ELIQUO WATER & ENERGY BV from the Netherlands. The Australian market shows a strong receptiveness to proven innovative solutions from Europe and now allow the export of ELIQUO’s knowledge and experience to this project.
After finalisation of the design, the dryers will be produced in the German factory of ELIQUO and will be ready for shipment in June 2021. After their arrival in Brisbane, the dryers will be transported to site for their installation. Start-up and commissioning of the project is foreseen by the end of 2021.
