Biobased fertilisers from fishery side-streams: an environmentally friendly alternative to mineral fertilisers?

Summary

The replacement of mineral fertilisers by biobased fertilisers (BBFs) produced from organic waste streams is promoted by the European Union to reduce political dependencies and nutrient excess. Life cycle assessment (LCA) studies have so far been mainly conducted on BBFs produced from municipal biowaste, sewage sludge and animal manures, primarily considering their production phase. This LCA study compares for the first time environmental impacts of three BBFs produced from fishery side-streams against those of mineral fertilisers assessing both BBF production (per kg N) and application (per kg broccoli), assuming burden-free side-streams. Compared to mineral fertilisers, two BBFs (one from fish sludge, the other from fish frames and heads) had a 3-62% (per kg N) and 11% (per kg broccoli) lower global warming potential and a 1-12% (per kg N) and 7-13% (per kg broccoli) lower mineral resources use. However, the third BBF from fish viscera showed overall higher impacts than the mineral fertiliser highlighting the importance of optimising the production of BBFs and their agronomic performance. Levers for optimisation include establishing the BBF production close to the location of the side-stream, implementing energy-efficient drying technologies and appropriate BBF application techniques. Methodological challenges such as modelling field emissions of BBFs and lacking harmonization of LCA methodology for the assessment of BBFs are discussed. By considering both production and application of BBFs, this study shows that BBFs from fishery side-streams can provide environmental benefits when used as a substitute for mineral fertilisers and identifies optimisation potential along the life cycle.