Technical and Economic Evaluation of Macroalgae Cultivation for Fuel Production (Draft)

Abstract

The potential of macroalgae as sources of renewable liquid and gaseous fuels is evaluated. A series of options for production of macroalgae feedstock is considered. These options include nearshore (for Macrocystis), floating adjacent and nonadjacent (for Sargassum), plus bay/estuarine and land-based options (for Gracilaria and Ulvo), The production option with the lowest feedstock costs is the adjacent strategy for Sargassum, with a cost of $48/dry ash-free metric ton (DAFMT) based on currently sustainable yields, and a potentially achievable cost of $24!DAFMT, based on improved yields. The estuarine option produced costs for Gracilaria and/or Ulva close to those of Sargassum: $54!DAFMT currently, with $27!DAFMT achievable with improved yields. The landbased system cannot produce macroalgae feedstock below $131/DAFMT, even with much higher yields than the nearshore systems. Because of their high carbohydrate content, the fuel products for which macroalgae are most suitable are methane and ethanol. Fuel product costs were compared with projected fuel costs in the year 1995. At currently sustainable yields, Sargassum, Gracilaria, and Ulvo could be competitive sources of methane; with yield improvements, Macrocystis could as well. For the production of ethanol, only Macrocystis and Gracilaria offer competitive production potential, and then only if improved yields can be achieved.