Cost Analysis of Aquatic Biomass Systems

A cost analysis of aquatic biomass systems was conducted to provide the U.S. Department of ENergy with engineering cost information on which to base decisions in the area of planning and executing research and development programs dealing with aquatic biomass as an alternative energy resource. Calculations show that several hundred 100 square mile aquatic biomass farms, the size selected by DOE staff for this analysis, would be needed to provide meaningful supplies of energy. It should be noted that sustems which require wasts (sewage, power plant, CO2) as a carbon source, natural harbors or lakes, and natural upwelling sites may not have application to the present study simply because they are very small compared to the large needs projected by DOE.

With this background, specific engineering analyses were conducted on two original design concepts for 100 square mile aquatic biomass system; outstanding experts in all aspects of this project were called upon to participate and provide information in projecting the costs for harvested aquatic biomass for these systems. 

It was found that the projections of cost for harvested open-ocean biomass, utilizing optimistic assumptions of scientific and engineering design parameters, appear to be above any practical costs to be considered for energy. One of the major limitations is due to the need to provide upwelled sub-surface water containing needed nutrients, for which pumping energy is required. It is shown that for lower yields of biomass, the energy in ocean waves may marginally provide energy to pump suitable amounts of upwelled water for nutrient supplu; however, costs of harvested biomass growth at increasingly higher yields, so much nutrient containing water is required that environmental wabe energy is insufficient and fuel or electric power is required for pumping; thus, with high yields, obtaining a net there are very substantial environmental and legal aspects of aquatic biomass farming in general that appear especially ponderous for an open-ocoean system. 

It is concluded from this analysis that large scale land-based aquatic biomass farms may merit development, but perhaps within a much narrower range than heretofore investigated. For example, land-based aquatic biomass systems based on biomass which require a carbon source other than carbon dioxide from the air appear to have higher costs than may be acceptable as an energy resource. Sewage slude appears to have limited availability as a carbon source for many energy farms and the utilization of CO2 from power plant stack gases requires duct work and distribution system which are prohibitively costly.