Yeast lees are a major winery by-product and contain nutrients and other useful compounds that are often lost when the material is disposed of. Recovering some of this value could reduce the volume of a winery waste stream while creating a useful input for winemaking.
The Yeast Lees Recycling project is investigating an enzyme-based process that breaks down spent yeast cells post-ferment and releases nitrogen into a form that can potentially be reused during successive fermentations. The longer-term aim is to develop a practical circular process in which wineries can recover value from their own yeast lees, reducing waste and potentially replacing some or all purchased fermentation nutrients.
Progress to date
The project has demonstrated that winery yeast lees can be enzymatically processed to release yeast-assimilable nitrogen. Bench-scale work established the key processing steps, including, depending on the enzyme used, pH adjustment, heating, maintaining the lees in suspension and allowing sufficient time for digestion.
Recycled lees have also been used in pilot winemaking trials. Under the conditions tested, the recycled material provided a viable source of fermentation nutrients and performed comparably to commercial organic nutrient products, with sensory assessment of the finished wines supporting further investigation of the approach.
Initial economic modelling has also shown that the process has the potential to be cost competitive with purchased organic nutrients. The strongest opportunity is likely to be where recycled lees can replace some organic nutrient supplementation; additional nitrogen sources may still be required for juices with very low nitrogen levels.
The remaining challenge is translating this into a simple and reliable winery process. Engagement with wineries has highlighted practical considerations including heating and processing requirements, labour, storage and stability of the recycled material, food safety and regulatory requirements, and how the process would fit around vintage operations.
What’s next?
The next stage will move the process into winery-scale trials, treating approximately 1–5 kL of yeast lees and using the resulting material in commercial-scale winemaking.
This will allow the project to assess whether the process can be operated consistently under normal winery conditions and whether recycled lees can be stored, handled and used without adding unacceptable complexity to winery operations. Further winemaking and sensory trials will build evidence across different wines and operating conditions.
The project will also refine the economics of the process, investigate regulatory, food safety and traceability requirements, and work with wineries and suppliers to understand what equipment, inputs and support would be needed for broader implementation.
Resources
Further information and resources will be added as the project progresses, including relevant project documents and research outcomes.