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The purpose of this study is to demonstrate feasibility of an integrated wastewater algae-to-biocrude process that can sustainably cultivate algal biomass for biofuel production. This process used pilot-scale algal cultivation ponds fed with municipal wastewater as the nutrient source. The open ponds were self-inoculated from the wastewater source, resulting in a mixed-culture microalgal community with distinct differences compared to laboratory-maintained and fertilized monocultures: 29.0% dry weight (dw) ash, 48.9% ash-free dry weight (afdw) carbon, 37.5% afdw oxygen, and 14.0% afdw lipid. The harvested algae was processed using hydrothermal liquefaction at 350 °C (autogenous pressures up to 2000 psig) for 1 h using 3 g of freeze-dried algae and 50 mL of water. The yield of biocrude was 44.5 ± 4.7% afdw, with an elemental weight percent composition of 78.7% carbon, 10.1% hydrogen, 4.4% nitrogen, and 5.5% oxygen and an energy content of 39 MJ/kg. Hydrothermal processing also resulted in the formation of 18.4 ± 4.6% afdw aqueous co-products (ACPs) and 45.0 ± 5.9% dw solid biochar. The ACPs contained 4550 ± 460 mg L −1 organic carbon, 1640 ± 250 mg L −1 total nitrogen, and 3.5 mg L −1 total phosphorus. The solid biochar product contained >20% dw carbon with an energy density between 8 and 10 MJ kg −1 . This study is the first hydrothermal liquefaction paper of wastewater-derived microalgae. The municipal wastewater matrix and resultant mixed-culture biomass significantly influenced liquefaction product distribution, yielding a higher proportion of biochar, which may be a valuable co-product. This paper explores the potential for wastewater-fed algal systems integrated with hydrothermal liquefaction, which together overcome challenges identified by the 2012 National Research Council's report on algal biofuel sustainability.

Microalgae, with their high lipid content, are a promising feedstock for renewable fuels. Traditionally, human and environmentally toxic solvents have been used to extract these lipids, diminishing the sustainability of this process. Herein, pulsed electric field technology was utilized as a process intensification strategy to enhance lipid extraction from Ankistrodesmus falcatus wet biomass using the green solvent, ethyl acetate. The extraction efficiency for ethyl acetate without PEF was lower (83-88%) than chloroform. In addition, the ethyl acetate exhibited a 2-h induction period, while the chloroform showed no time dependence. Utilizing PEF technology resulted in 90% of the cells being lysed and a significant enhancement in the rate of lipid recovery using ethyl acetate. The increase in lipid recovery was due to the presence of the electric field and not due to temperature effects. The PEF technology uses less energy than other PEF systems reported in the literature.