Sargassum blooms in the Atlantic Ocean – From a burden to an asset

Abstract

Recently there has been a significant increase in the amount and frequency of seaweed blooms of the holopelagic brown macroalgae Sargassum fluitans and natans (hereafter Sargassum) in the Atlantic Ocean. These blooms impose a major burden on residents (e.g. rotting beached Sargassum, unpleasant odor, toxic gases), the local economy of countries with affected coast lines (e.g. impacting tourism and aquaculture, costs for remediation), and have a significant impact on the environment (e.g. beaches and coastal areas) and local marine wildlife. Here we present a Techno-Economic Analysis to demonstrate how this burden can be turned into an economic, social and environmental asset. The suggested process involves sustainable ship-based harvesting of excess biomass (up to 6.3 MT·year−1) and using hydrothermal liquefaction (HTL) and established fuel refining processes to deliver renewable liquid fuels. Sea-based harvesting of Sargassum addresses the primary cost impediment for algae-based renewable fuel production, reducing capital and operating costs by 78% and 66% respectively compared with currently modelled land-based microalgae renewable fuel production processes. The modelled approach charts a path to cost competitive renewable fuels that reduce CO2 emissions while mitigating the economic, social and environmental problems caused by these large Sargassum algae blooms. The financial analysis of the process yielded an Internal Rate of Return (IRR) between 2.4% and 28.1% based on the scenarios analyzed. The process could generate up to 8500 bbl of crude oil per day profitably at US$43 bbl−1 (10% IRR), equivalent to 470 ML of diesel or jet fuel per year as well as biofertilizers and recycled nutrients, employ around 200 direct personnel and create up to 1000 indirect jobs.