SA Water sets sights on compost digestion co-op

SA Water will partner with South Australia’s composting industry to investigate options for a new renewable energy facility that uses anaerobic digestion to extract gas from high strength organic food waste material, before the leftovers are turned into high quality compost and fertiliser products.

Over the next six months, a new working group will bring SA Water together with members of the state’s composting industry to model scenarios for a potential facility within the Bolivar Wastewater Treatment Plant, providing state-wide benefits for all involved.

SA Water General Manager of Customers, Strategy and Innovation Anna Jackson said the project would contribute to the utility’s aim of achieving a zero cost energy future to keep the operating costs of supplying water and removing sewage down.

“Bolivar’s existing anaerobic digesters create and capture enough biogas produced through sewage treatment processes to cover up to 90 per cent of the plant’s energy requirements and introducing a new separate stream for food waste will increase this,” Anna said.

“Running high strength organic food waste material through a new digester will allow maximum value to be extracted from it, with the gas used to reduce our electricity costs and the solids forming composts and fertilisers that support the production of new food crops, before the cycle begins again.”

Anaerobic digesters are large, sealed tanks that heat the solid waste from either organic matter or sewage – known as sludge – in an oxygen-free environment, to promote the natural bacterial metabolic processes that break it down.

“Early trials of co-digestion at our Glenelg Wastewater Treatment Plant, where we added the high strength organic material to the existing sewage digesters, proved an effective way to increase biogas production, however didn’t allow other industries to also extract benefit from the process,” Anna said.

“Independent economic studies have highlighted a joint solution with industry is the best way to get this idea off the ground, and as a result we’ve established an industry-based working group to investigate the feasibility of this project.

“We look forward to working with the state’s composters on achieving positive outcomes for everyone involved, and demonstrating ways to nurture a sustainable, circular economy.”

The co-digestion facility trialled at Glenelg will continue operating for the time being, but SA Water has no plans to expand this to Bolivar.

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