Collaborative Research: A Novel Biological Valorization of Hydrothermal Liquefaction Wastewater with Marine Protist and its Granulated Phenotype

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Hydrothermal liquefaction (HTL) has been considered as a promising thermal processing approach to biofuel production from a broad range of organic matter, including agricultural waste biomass, municipal solid waste, and algae. A recent U.S. Department of Energy report stated that as much as 5.9 billion gallons of biocrude could be produced each year in the U.S. from the available waste organic matter using HTL technology; this biocrude can be further refined to liquid transportation fuels using processes similar to conventional petroleum refining, replacing those fuels currently produced from non-renewable feedstocks. However, current HTL processes produce a large amount of wastewater containing high concentrations of organic compounds and nutrients; the sustainable disposal of this wastewater is one of the most significant bottlenecks to the scale-up and commercialization of HTL. This research will address concerns from both environmental and energy conversion efficiency perspectives of HTL by recovering organic carbon and nutrients from HTL wastewater. This is a critical step to increasing the net energy yield and enhancing the economic viability and environmental sustainability of HTL processes. In the course of carrying out this project, the researchers will train the next generation of scientists and engineers in biofuel production, biotechnology/bioprocessing, and environmental stewardship, all while educating the public about sustainable biofuel production and the impact of energy consumption on economic, environmental and societal sustainability.The research team of this proposal has recently found that a marine protist Thraustochytrium striatum HB can survive and grow in wastewater produced from HTL processing of municipal solid waste without supplemental nutrients while removing approximately 80% total organic carbon, 100% total nitrogen, and 80% phosphorus. Additionally, the microbes were found to be tolerant of wide pH and salinity ranges (comparable to sea water) in metabolizing organic compounds in HTL wastewater while being able to form cell aggregates under harsh conditions. Therefore, marine protists hold promise to be a new class of superior microorganisms for HTL wastewater treatment and valorization. The overarching goal of this project is to establish a T. striatum HB-facilitated platform for HTL wastewater valorization to enable sustainable HTL for biofuel production. The specific objectives of this research are to: (1) elucidate the correlation between biocrude yield and the HTL wastewater composition; (2) reveal the metabolic adaptation of T. striatum HB to the new wastewater environments to enhance overall energy return and biocrude yield; and (3) explore the formation mechanisms of T. striatum HB biogranules and the resulting performance impact on HTL wastewater valorization since biogranules are more efficient in wastewater valorization compared to dispersed cells. The marine protists could be a new class of promising microorganisms for valorization of other types of high-strength wastewater. The interdisciplinary nature of the proposed research will facilitate the integration of research and educational plans to enhance the education programs of three institutes involved in this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.