Modeling the Production of Microalgal Biomass in Large Water Resource Recovery Facilities and Its Processing into Various Commodity Bioproducts

Abstract

Algae are capable of sequestering nutrients such as nitrates and phosphates from wastewater in the presence of sunlight and carbon dioxide (CO2) to build up their body mass and help combat climate change. In the current study, we carried out different case studies to estimate the volume of algal biomass that could be produced annually using the rotating algal biofilm (RAB) method in three large-scale water resource recovery facilities (WRRFs) in Texas: Fort Worth, Dallas, and Houston. We calculated the total amount of lipids, carbohydrates, and proteins that could be fractionated from the algal biomass while using the hydrothermal flash hydrolysis process, followed by converting these biomolecules into commodity products via reported methods and yields. In the first case study, we estimated the amount of biogas and electricity produced in anaerobic digesters when the algal biomass and sludge generated in large-scale WRRFs are co-digested. Using this approach, electricity generation in a large-scale WRRF could be increased by 23% and CO2 emissions could be further reduced when using biogas combustion exhaust gases as a carbon source for the RAB system. In the second case study, it was estimated that 988 MT mixed alcohol or 1144 MT non-isocyanate polyurethane could be produced annually from the protein fraction in the WRRF in Fort Worth, Texas. In the third case study, it was estimated that 702 MT bio-succinic acid or 520 MT bioethanol could be produced annually using the carbohydrate fraction. In the fourth case study, it was estimated that 1040 MT biodiesel or 528 MT biocrude could be produced annually using the lipid fraction. Producing renewable commodity fuels and chemicals using the algal biomass generated in a WRRF will help to displace fossil fuel-derived products, generate new jobs, and benefit the environment.