Seaweed as a third-generation biofuel feedstock can provide fuels and chemicals to offset climate change caused by fossil fuel usage and support a cleaner and thriving sea and ocean environment. However, despite several advantages, there are significant challenges to deploying commercial-scale seaweed-based biorefineries, including low-cost and large-scale seaweed cultivation, and lowering the capital and production costs of seaweed conversion to biofuels. Additionally, many conversion platforms can be used to produce biofuels from seaweed. Thus, it is still unclear which technology is economically competitive and, most importantly, the major bottle necks in the large-scale deployment of seaweed biorefineries remain to be identified. Therefore, a detailed study was conducted to (1) analyze the global state of the seaweed industry, (2) identify platforms for seaweed-based biofuels and bioenergy production on bench-scale investigations, (3) provide a basis for future large-scale techno economic feasibility studies on seaweed conversion to biofuels and bioenergy, (4) conduct a comparative analysis of biofuels and bioenergy production platforms using seaweed, and (5) identify the major bottlenecks in developing commercial-scale seaweed biorefineries. A comprehensive techno-economic analysis was conducted using six conversion platforms, including sugar, methane, volatile fatty acid, pyrolytic oil, syngas, and hydro thermal liquefaction oil. Based on the current market trends, the results indicated that mixed alcohols production using a volatile fatty acid platform is economically competitive, with the minimum ethanol selling price of 0.28–0.33 $/L, which is 7.8%–21.2% lower than the average wholesale price (0.36 $/L) of ethanol in 2020. In contrast, all other platforms were found to be economically unfeasible.