This presentation will reflect on the role of seaweed in food systems within the context of absolute sustainability. Seaweed not only provides nutrient-rich food but also delivers ecosystem services such as carbon and nutrient capture that can support climate mitigation and water quality restoration. Using examples from recent Ulva studies, I will exemplify how choices around system boundaries and accounting methods influence sustainability assessments. The focus will be on the farm-to-fork perspective, with the waste sector kept out of scope in line with conventional food LCAs. Rather than giving final answers, the talk will invite reflection on whether and how to account for emission capture in food LCAs, and how ecosystem service delivery can be integrated into absolute sustainability frameworks. The aim is to encourage discussion on seaweed’s contribution to regenerative and resilient blue food economies.