Life cycle assessment (LCA) is a holistic methodology that identifies the impacts of a production system on the environment. The results of an LCA are used to identify which processes can be improved to minimize impacts and optimize production. LCA is composed of four phases: (1) goal and scope definition, (2) life cycle inventory analysis, (3) life cycle impact assessment, and (4) interpretation. The goal and scope define the purpose of the analysis; describe the system and its function, establish a functional unit to collect data and present results, set the system boundaries, and explain the assumptions made and data quality requirements. Life cycle inventory analysis is the collection, processing and organization of data. Life cycle impact assessment associates the results from the inventory phase to one or multiple impacts on environment or human health. The interpretation evaluates the outcome of each phase of the analysis. In this phase the practitioner decides whether it is necessary to amend other phases, e.g., collection of more data or adjustments of goal of the analysis. In the interpretation, the practitioner draws conclusions, exposes the limitations, and provides recommendations to the readers. The quality of LCA of seaweed production and conversion is based on data availability and detail level. Performing an LCA at the initial stage of seaweed production in Europe is an advantage: the recommended design improvements can be implemented without significant economic investments. The quality of LCA will keep improving with the increase of scientific publications, data sharing, and public reports.