The proliferation of sargassum has emerged as a pressing global ecological challenge, with far-reaching impacts on marine ecosystems, public health, and coastal economies. While Europe has so far been largely insulated, climate change and associated factors—rising sea temperatures, shifts in oceanic currents, and increased nutrient loading—heighten the risk of sargassum blooms in European marine ecosystems. Regions like the Mediterranean, the Baltic Sea, and Northern European freshwater systems are increasingly vulnerable, threatening sectors such as fisheries, agriculture, and tourism, which collectively contribute over €1.3 trillion annually to the EU economy. In the Caribbean, Cuba illustrates the devastating consequences of sargassum inundations, with annual blooms exceeding 24 million tonnes. These have inflicted severe economic damage on tourism, fisheries, and public health. European-owned hotels and tourism operators in the Caribbean report annual losses of €120 million, compounded by clean-up costs of €30,000 per kilometer of coastline and ecosystem degradation affecting fisheries and biodiversity. Hydrogen sulfide emissions further exacerbate public health risks, underscoring the urgency for innovative and proactive solutions. SARGEX is a transformative project designed to address these challenges by providing scalable, sustainable, and circular solutions for marine biomass valorization. The project integrates modular processing plants equipped with biodigesters for zero-waste transformation of sargassum into valuable outputs, including bioinputs, biochar, and biogas. These bioinputs, capable of replacing up to 30% of synthetic agrochemicals, are projected to increase agricultural yields by 30%. Additionally, biogas generation (20 m³ per tonne) and biochar production contribute to renewable energy goals and soil enhancement, aligning with the EU’s Green Deal, Circular Economy Action Plan, and Biodiversity Strategy 2030.