This study evaluates the environmental impacts of land-based seaweed cultivation systems in Oregon, USA, using a cradle-to-gate Life Cycle Assessment (LCA). Two facilities, producing Devaleraea mollis (Pacific Dulse), were assessed, with focus on their potential as a sustainable protein source. CML-IA baseline (version 3.09, 2016) together with ReCiPe 2016 Midpoint Hierarchist (version 1.08) for two indicators were used as Life Cycle Impact Assessment (LCIA) methods. The analysis highlights the air pump's energy use and infrastructure (HDPE tanks, PVC pipes) as major contributors to environmental impacts with more than 15% and 10%, respectively, in several impact categories. In terms of protein content, this seaweed performs comparably to other plant and animal-based proteins, with similar average global warming potential (34.5–86.4 kg CO2e per kg protein) but significantly lower land and water use impacts. The results suggest improvements in system design, including optimising productivity, reducing aeration energy, and utilizing agricultural or aquaculture waste as nutrients to minimize the need for artificial fertilisers. Additionally, replacing PVC with polyethylene in the piping could reduce environmental burdens. Comparison with sea-based seaweed farming indicates that land-based systems have higher environmental impacts due to energy use and infrastructure demands. However, land-based cultivation provides more controlled conditions, reducing stressors like variable nutrient levels and storms, potentially making it a more reliable system in specific contexts. • First cradle-to-gate LCA of land-based cultivation of Devaleraea mollis • Aeration energy and PVC/HDPE infrastructure dominate environmental impacts. • Land-based systems use less land and water than animal-based proteins. • D. mollis shows comparable climate impact to other proteins even at small scale. • Optimised scaling could deliver a low-carbon, resource-efficient protein source.