As bioenergy becomes a more central part of wastewater and resource recovery planning, the question of how to manage digestate has become increasingly important. Digestate, the byproduct of anaerobic digestion, represents both a challenge and an opportunity for water utilities.
While widely used in agricultural settings overseas, its application in Australia remains limited due to a lack of local data, uncertainty about its performance under local soil conditions and limited awareness among farmers. Yarra Valley Water’s ReWaste Digestate Research project aims to address these gaps through a technically rigorous study of digestate’s impacts on soil health, drought resilience and crop performance.
Yarra Valley Water sought $25,000 toward a $50,000 research program, making the Challenge funding a key enabler in moving the work into laboratory trials.
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Why is digestate research needed in Victoria?
Digestate is already recognised globally for its nutrient value, but Australian soils, climate conditions and farming practices differ significantly from those in Europe and North America. Many Victorian farmers remain hesitant to adopt digestate because of limited evidence on its agronomic performance, microbiological composition, and long-term soil impacts. For utilities, the uncertainty creates a barrier to investment in anaerobic digestion, as the commercial value of digestate remains unresolved.
The ReWaste facility at Wollert produces digestate suitable for testing under controlled conditions. By partnering with Griffith University, Yarra Valley Water is establishing a baseline dataset tailored to Victorian soils and regional crop types. This research provides a foundation for future broadacre trials and supports the development of a Victorian digestate market that could strengthen both the water and agricultural sectors.
What will the digestate research investigate?
The study focuses on several core technical parameters. One is the effect on soil microbiology, including microbial diversity, functional groups and microbial respiration. These factors influence soil structure, nutrient cycling and the ability to retain moisture during dry periods. Laboratory pot trials will compare digestate-treated soils with soils treated using conventional fertilisers, tracking changes across multiple growth cycles.
A second component is DNA-based microbiological characterisation, which will identify the microbial communities present in both pasteurised and unpasteurised digestate. This is important for understanding how digestate interacts with agricultural soils and whether specific treatments influence the resilience of the soil microbiome.
The third area focuses on crop response. Early indicators from international research suggest that digestate can increase root biomass, stimulate root elongation and improve plant health, all of which contribute to drought resilience. The study will quantify these effects under Australian conditions, using crops aligned with agricultural partners already engaged in early-stage commercial discussions.
What outcomes could this research deliver?
If the trials confirm improvements in soil carbon, water retention and crop yield, digestate could become a valuable soil amendment for Victorian agriculture. This would have direct implications for regional drought resilience, especially in dryland farming systems, where soil structure and moisture-holding capacity are critical. A successful proof of concept would also help utilities justify investment in anaerobic digestion by providing a clear pathway for digestate reuse.
More broadly, the study supports Victoria’s circular economy objectives. Digestate offers a way to return organic matter to soils, reduce reliance on synthetic fertilisers and create new economic opportunities between water utilities and the agricultural sector.
What happens next?
Following laboratory trials, Yarra Valley Water intends to progress to commercial-scale field trials with regional partners. The findings will be made available to utilities and the broader bioenergy sector, supporting shared learning and wider adoption.
Digestate research remains a critical step toward establishing a viable circular bioenergy economy in Australia. By generating the evidence needed for farmers and investors, Yarra Valley Water is helping position digestate as a practical, soil-improving resource rather than a residual byproduct.