Deep Water Nutrient Supply for an Offshore Ulva sp. Cultivation Project in the Eastern Mediterranean Sea: Experimental S
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Deep Water Nutrient Supply for an Offshore Ulva sp. Cultivation Project in the Eastern Mediterranean Sea: Experimental Simulation and Modeling Meiron Zollmann 1 & Hadar Traugott 2 & Alexander Chemodanov 1 & Alexander Liberzon 2 & Alexander Golberg 1
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Offshore cultivation of marine macroalgae is a potential sustainable resource for fuel, food, and chemicals. Offshore, the high productivity of macroalgae cultivation depends on external nitrogen supply. The current work examines the idea of supplying nitrogen for Ulva sp. cultivation in the oligotrophic Eastern Mediterranean Sea (EMS) by artificial upwelling of nutrient-rich deep seawater (DSW). Growth rates, protein, and starch contents of Ulva sp. were measured for time varying fertilizations with nitrate concentrations corresponding to nutrient concentrations of DSW at increasing depths of the EMS. A maximal relative growth rate of 7.4% was measured for fertilizing ten times per week with 5.8 μM, which corresponds to the artificial upwelling from the depth of 700 m at EMS. Protein and starch contents ranged between 1–6 and 8–15% of dry weight. Finally, yields and energetic costs of DSW pumping were modeled for an example case of 10-ha offshore farm. The model predicts a high productivity but low energetic efficiency, which can be improved by coupling the biomass production with offshore power sources such as ocean thermal energy conversion. Keywords Artificial upwelling . Macroalgae . Biorefinery . Offshore cultivation . Eastern Mediterranean Sea
Introduction Offshore cultivation of marine macroalgae, also known as seaweed, is a potential sustainable resource for fuel, food, and chemicals [1, 2], which can be co-produced in marine biorefineries [3, 4]. This renewable resource combines a wide array of commodity and high value products [3] with the unique ability to utilize free ocean areas, thus minimizing land and fresh water requirements [1, 5]. In addition, it can provide important environmental services such as pollution mitigation, nutrient recycling, and carbon biosequestration [1, 6, 7]. However, offshore macroalgae production and processing technologies are not mature yet [1, 3]. Multiple challenges, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12155-019-10036-3) contains supplementary material, which is available to authorized users. * Alexander Golberg [email protected] 1
Porter School of Environmental and Earth Sciences, Tel Aviv University, Tel Aviv, Israel
2
School of Mechanical Engineering, Tel Aviv University, Tel Aviv, Israel
starting from species choice and controlled cultivation and harvesting solutions [8], through efficient biomass disintegration techniques, to the establishment of cost effective production streams suitable to present global market, are yet to be tackled [3]. Growth rate and chemical composition are key factors for economic production of commodities and other products [7, 9]. For example, in
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