A COMPARATIVE CO2 LIFE CYCLE ANALYSIS OF THREE NUTRIENT SOURCES FOR A NOVEL OFFSHORE MACROALGAE FARM IN HAWAI’I

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2022-12
Authors
Chambers, Trevor
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Hopkins, Kevin
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Tropical Conservation Biology & Environmental Science
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Large-scale offshore seaweed cultivation systems using novel technologies have the potential to sequester large amounts of CO2, potentially decreasing ocean acidification, while producing biomass that could be converted into fuel. However, low nutrient concentrations in offshore sea surface water (SSW), such as those seen surrounding Hawai’i Island, are a primary constraint to seaweed growth. Nutrient enhancement through the upwelling of deep-sea water (DSW) and artificial fertilization (AF) could provide the additional nutrients required to increase seaweed growth rates, but it is unknown if these novel systems are sustainable. Therefore, the objective of this study was to model the growth of three seaweed species: Ulva lactuca, Gracilaria parvispora, and Halymenia hawaiiana, to determine the potential CO2 sequestration capacity. Deterministic models were used to estimate the CO2 emissions of the various nutrient sources and CO2 sequestration potential of the three species, using 4 different Specific Growth Rates (SGRs), on the hypothetical 1000 hectare offshore farm. Regardless of SGR and species, SSW had the lowest net CO2 impact over a 10-year lifespan (sequestration ranged from 234,658 – 923,011 MT of CO2); DSW showed the greatest net CO2 impact (sequestration ranged from 234,323 – 1,720,416 MT of CO2), and the AF system was almost the same as DSW (sequestration ranged from 226,617 to 1,712,709 MT of CO2). Although all systems sequestered more CO2 than they produced, questions regarding economic viability of each nutrient source must be answered by future research
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Agriculture engineering, Environmental science, Macroecology, CO2, Farming, Hawai'i, Life Cycle Analysis (LCA), Seaweed
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68 pages
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