Turning Digestate from Anaerobic Digestion into Local Compost—An Alternative to Out-of-Province Waste Disposal in Bolzano

In South Tyrol, organic waste such as food scraps is treated through anaerobic digestion, producing digestate—a semi-solid by-product. Until now, this material has been sent outside the province for disposal, resulting in high transport costs, increased emissions, and a missed opportunity to valorise the material locally.

This pilot aims to test a more sustainable solution: co-composting digestate with green waste (e.g. grass clippings and urban greenery) at a facility located just a few kilometres from the anaerobic digester. The goal is to process this material close to its source, reduce environmental externalities and support a circular economy model, replacing the present model by a new one.

The composting described will be carried out indoors—unlike the current open-air systems in the province—enabling better process control and odour management. Both natural and forced aeration systems will be tested and all emissions will be filtered.

Additionally, the pilot will explore the feasibility of co-composting the digestate with other local residues such as fruit-processing waste, pomace, or diatomaceous earth—currently disposed of externally. This will help identify sustainable solutions for multiple organic waste streams.

The pilot will concern regular sampling and laboratory analyses to ensure compost quality and to define a replicable composting protocol.

Main objectives:

- Introducing local treatment of digestate in the province through co-composting

- Developing a compost quality protocol for future regulations

- Enabling a sustainable, scalable solution for organic waste in the province

- Mainstreaming into the Waste Management Plan for the Province of Bolzano the new model resulting from the testing to normalise it.