Macroalgae Aquaculture for Nutrient Recovery and Bioenergy Production at Wastewater Treatment Plants with Ocean Outfalls
Mentor: Dr. Shane Rogers
Department: Civil and Environmental Engineering
This project, which combines academic and industry expertise, explores farming native macroalgae (kelp) to serve the dual purpose of a nutrient sink in coastal environments impacted by publicly-owned treatment works with ocean outfalls, and as a bioenergy feedstock. Cultivation of kelp in these impacted coastal waters will restore ecosystem services and expand opportunities for the aquaculture industry. Our research will advance understanding of potential lifecycle impacts of this approach versus conventional unit processes engineered for nutrient removal at wastewater treatment plants. Participants in this REU project will have an independent research project that combines experimental and modeling work designed to address one of three objectives including: i) characterization of biomass production rates and nitrogen assimilation by kelp; (ii) determination of the biogas potential of kelp and potential impact on the digestion process via codigestion with wastewater treatment sludge; and (iii) construction of Lifecycle Inventories to optimize kelp farming operations for nutrient removal and biogas production. Some travel for acquisition of samples or for measurements of kelp growth and nutrient assimilation, including from coastal waters, may be required for this study. A revolution in engineering design that expands ecosystems engineering approaches, especially those with low carbon footprint plus energy and extractive potential, is needed to meet the grand challenges associated with equitable water supplies and balancing the nitrogen cycle for future generations. Management of the nitrogen cycle is recognized as a significant national and international problem. It is included as one of fourteen grand challenges presented by the National Academy of Engineering. One strategy that promises to manage nutrients in coastal environments is the cultivation of macroalgae (e.g., seaweed such as kelp) as bioextractants. Macroalgae inhibit phytoplankton growth, require a constant supply of nutrients, and can be readily harvested from the water to serve as nitrogen and carbon sinks. Providing clean and sustainable energy to meet the demands of our growing population is also a leading global problem. According to Sustainable Energy Ireland, up to 447-TJ of energy could be generated from macroalgae in Ireland by 2020, and would be economically favorable if the costs of nutrient supply for macroalgal growth could be reduced. In Japan, it has been estimated that one kelp farm of 41.2 square kilometers could mitigate 65,000 tonnes of carbon dioxide each year and produce 100,000,000 KWh of electricity from methane production if sufficient nutrients could be supplied to support cultivation. Kelp beds are presently used effectively to reduce nutrient impacts of integrated aquaculture operations.