An economic analysis of bioethanol production from the marine macroalga Ulva (Chlorophyta)

Abstract

We performed a cost-benefit analysis for bioethanol production using biomass of Ulva rigida, a marine macroalga (seaweed), co-cultured with fish in an intensive offshore aquaculture unit. This is the first report for such analysis that takes into consideration offshore seaweed cultivation and uses a recently developed, novel and simplified ethanol production technology that is devoid of costly pre-treatments imposed to the seaweed biomass. By simultaneously producing ethanol with valuable Dried Distillers Grains with Solubles (DDGS) by-products such as animal feed, the economic viability of this system is plausible over a production range of 77–240 dry tons of seaweed per day. As such, applying the model to suggested future scenarios for the Israeli Mediterranean shorelines, which limits aquaculture to ca. 600 ha, results in unprofitability. Further, sensitivity analyses place profitability as mainly dependent on DDGS prices and on the daily growth rate (biomass yield) of the macroalga. These two are key factors to achieve profitability at the 600-ha scenario.

Feasibility study of Ulva sp. (Chlorophyta) intensive cultivation in a coastal area of the Eastern Mediterranean Sea

“…was chosen as the model species as it is very common on the shores of Israel and displayed high biomass productivity in extensive cultivation offshore in Israeli waters . Furthermore, the production of proteins and starch, and biomass fermentation to acetone, ethanol, butanol, and polyhydroxyalkanoates from several Ulva species has already been demonstrated …”

Growth, protein and carbohydrate contents in Ulva rigida and Gracilaria bursa-pastoris integrated with an offshore fish farm

“…Relocating seaweeds from high nutrient concentrations to low nutrient concentrations could further enhance the carbohydrate content of the subjected seaweeds. In this regard and while relocation of seaweed biomass may be technically challenging or cost-ineffective on large scales (see Korzen et al 2015), exposures back to low nutrient levels enhanced significantly the seaweed carbohydrate content. There is also an additional environmental benefit and ecosystem service of high value to be evaluated when integrating algal and finfish cultures.…”

Applications of Ulva Biomass and Strategies to Improve Its Yield and Composition: A Perspective for Ulva Aquaculture

“…dried biomass contained 16 to 22% of its dried biomass as TRS (total Reducing Sugars), and TRS showed a conversion rate of 30% to ethanol upon fermentation. The feasibility of producing Ulva feedstock in outdoor land-based cultivation for bioethanol production has been investigated and economic analyses have been conducted [ 96 , 97 , 98 , 99 ]. A long-term research program has shown that outdoor ponds of 1000 m 2 can produce 10 tons of Ulva biomass (DW) per year which can generate about 730 L of ethanol [ 96 , 98 ].…”