Plant gasifies to slash biosolid waste

The Australian Renewable Energy Agency (ARENA) has pledged $6.2 million in funding for the development of the Loganholme Wastewater Treatment Plant Gasification Facility at Loganholme, Queensland. The $17.28 million project — claimed to be the first time that gasification has been incorporated into a wastewater treatment plant in Australia — will lead to a 90% reduction in the volume of sewage sludge (biosolids) waste disposal at the plant.

The facility — Logan City Council’s (LCC's) largest wastewater treatment plant — serves 300,000 people and produces approximately 34,000 tonnes of biosolids each year. Biosolids are currently dewatered via an energy-intensive mechanical drying and treatment process before being transferred for land application.

The plant upgrade will include installation of a gasifier, which will create gaseous fuel from the biosolids that have been dewatered, dried and treated at high temperatures. The material produced is a biochar containing carbon, phosphorus and potassium that could be used as an environmentally friendly soil conditioner. LCC intends to market this biochar once the facility becomes operational.

The gasifier will reduce greenhouse gas emissions from the plant and the gas produced during the process will be utilised within the system as part of the biosolid drying process. An onsite solar power system will also help the facility move close to energy neutrality.

ARENA CEO Darren Miller said the project will offer significant opportunities to be replicated by other councils.

“Logan City Council’s demonstration project is expected to deliver a commercial business case for the gasification of biosolids for similarly sized wastewater treatment plants across Australia. The key knowledge learned from this installation will be significant given the first-of-kind deployment.

“This innovative process will reduce energy costs, emissions and significantly reduce the volume of waste from the sewage treatment process,” he said.

Acting Road and Water Infrastructure Director Daryl Ross said LCC was committed to finding a more viable and sustainable management solution that also lessened the environmental impact.

“At present, six truckloads of biosolids are taken 300 km to Darling Downs for land application each day. That costs $1.8 million annually and accounts for 30% of the operating costs of the plant,” he said. “Costs are increasing due to rising electricity prices, increasing population and tightening of government regulations on carbon reduction and managing persistent organic pollutants in soils.”

Proof-of-concept trials will be completed in February 2020 and construction is set to begin in July 2020, with the facility fully operational by July 2021.