The production of mineral fertilisers causes several sustainability issues: while the manufacturing of nitrogen fertilisers requires high energy input, phosphorus fertilisers depend on the extraction of phosphate rock from finite deposits (Zhang, Akyol, and Meers 2023). In a circular economy, fertiliser production should thus be shifted towards the valorisation of so far unused biowaste streams from various sources (Chojnacka, Moustakas, and Witek-Krowiak 2020; Zhang, Akyol, and Meers 2023). An increasingly important waste stream originates from fish processing and aquaculture production. In this study, we analyse the environmental impacts of the production and application of bio-based fertilisers (BBFs) produced from fish processing and aquaculture waste and compare them to the production and use of mineral fertiliser.