Harvesting Natural Algal Blooms for Concurrent Biofuel Production and Hypoxia Mitigation: Case Study of the Gulf of Mexico Situation

This study assesses the net energy balance and economic benefits of harvesting environmental algal blooms and conversion of the harvested biomass into biofuels. An engineering model was developed to compare the energy efficiency of different harvesting methods and biofuel conversion techniques. Three different harvesting techniques plankton net trawling, traveling screen, and screw pump filtration are compared in terms of energy consumption and harvesting efficiency. Among the various conditions modeled, the most favorable harvesting condition was produced by a 750 kW fishing boat with a plankton trawling net for harvesting algae biomass at 0.5 m/s harvest speed and harvesting from the surface to 0.5 m depth in the ocean. When harvesting a highly eutrophic area (40 mg-chl/m3) under these conditions, we estimate plankton net trawling operation can collect 100 kg of dry algal biomass with 1 GJ of harvesting energetic consumption. Overall, the energetic analysis revealed that the entire harvesting and conversion process can achieve an energy “break-even point” if the chlorophyll concentration is above 55 mg/m3. We use the Gulf of Mexico hypoxic area as our case study site. Plankton net harvesting technology can harvest 23,313 metric tons in 3 month in the cost of 81,380,937. This result also suggests that vertical focusing technology can offset 98% of harvesting fuel consumption.