With the increasing volumes of Sargassum washing up on beaches across the Gulf coast and Caribbean, coastal communities find themselves threatened due to the release of ammonia, hydrogen, and sulfides from the decaying Sargassum. This threatens not just the economic backbone of the communities, such as tourism and aquatic resources, but human health, threatening the respiratory system in particular. This has prompted research into ways to develop an effective method in which to convert Sargassum into a material with valuable properties. In this study, the economic feasibility of producing Sargassum-derived hydrochar was investigated via techno-economic assessment (TEA) for varying operating conditions. Sargassum was converted into hydrochar via hydrothermal carbonization (HTC) at 180, 220, and 260oC for 30 min. The hydrochar was then synthesized via pyrolysis at 600oC for 30 min, under inert conditions. This process utilizes units such as heat exchangers, continuous stirred tanks, filter presses, pumps, dryers, dust collectors, and more. In summary, raw Sargassum undergoes HTC with deionized water at mass ratio of 1:10 at the mentioned temperatures for a residence time of 30 min. Once complete, the produced hydrochar is separated from the process liquid and flue gas using a filter press, where a portion of the process liquid is recycled to the HTC process. The hydrochar is then dried, pyrolyzed then filtered through a dust collector. After filtration, the hydrochar is then collected for distribution. This processes used several assumptions such as complete mixing in the homogenizer and process liquid being a sufficient cooling source were used. A sensitivity analysis was also observed where parameters such as the price of hydrochar and the tipping incomes were varied in order to observe the economic flexibility of the assessment. It was observed that the return on investment, for the base case, was estimated to be $2.36, $2.43, and $2.62 million USD, respectively, with break-even points during years 5, 10, and 4, respectively with the sensitivity analysis showing a decrease in the price of hydrochar prolonging the break-even point by an average of 5 to 6 years.
