Waste-derived fertilisers under a biological risk lens

Sustainable fertilisers are nutrient products intended to reduce reliance on finite resources and environmental burdens while maintaining agronomic function. This review examines waste-derived fertilisers - manure, compost, digestate, biosolids, struvite and biochar - whose sustainability depends on treatment performance, contaminant control and life-cycle context. A targeted narrative synthesis of 2015–2025 literature informed a biological risk framework and three case scenarios. Scenario 1 transcribes organism-specific annual probabilities from a published farm-to-fork lettuce model; Scenarios 2 and 3 are qualitative stress tests. For raw-manure lettuce, published annual probabilities were 7.03 × 10 − 4 for Cryptosporidium , 2.27 × 10 − 4 for pathogenic Escherichia coli , 5.43 × 10 − 5 for Listeria and 1.79 × 10 − 1 for Mycobacterium avium , using an animal-derived dose-response function for the latter. Pasteurised digestate reduced the corresponding modelled probabilities to ≤ 1.42 × 10 − 10 . No numerical probability is assigned to the carrot scenario because missing route-specific exposure data preclude application of the published Ascaris dose-response model. No absolute AMR probability is estimated because validated dose-response functions for environmental ARG acquisition are unavailable. Validated treatment, curing, monitoring and multi-barrier controls can reduce biological hazards, but performance must be verified for each matrix, process and use. Key gaps concern viruses, helminths, ARG transfer, long-term field outcomes and the burdens of energy- or reagent-intensive treatments.