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We have demonstrated the feasibility of struvite production coupled with hydrogen generation for nutrient recovery. Electrochemical struvite was precipitated at low pH from a magnesium anode, eliminating the need for chemical additives and their associated costs. A faradaic efficiency (FE) near 30% was achieved while hydrogen was simultaneously produced with a FE near 40%. With the co-generation of two valuable products, costs for the electrochemical process are offset to help increase the feasibility of struvite production. We have also demonstrated control over the final product composition to form either an ammonia or an ammoniafree magnesium phosphate (struvite or newberyite, respectively). High temperatures decompose struvite to newberyite in the final product; however, at intermediate temperatures, competition between migration and convection dictates product composition. Under convection-dominating regimes, struvite is formed while newberyite forms under migration-dominating regimes. Identification of these parameters controlling product composition increases adaptability of the process by enabling customization of N:P ratios to serve a variety of different farming environments. [ABSTRACT FROM AUTHOR]

The cost-effective production of liquid biofuels from microalgae is limited by several factors such as recovery of the lipid fractions as well as nutrients management. Flash hydrolysis, a rapid hydrothermal process, has been successfully applied to fractionate the microalgal biomass into solid biofuels intermediates while recovering a large amount of the nutrients in the aqueous phase (hydrolyzate) in a continuous flow reactor. The aim of the work is to enhance the quality of a high-ash containing marine algae Nannochloropsis gaditana as biofuel feedstock while recycling nutrients directly for algae cultivation. Characterization of products demonstrated an increase in extractable lipids from 33.5 to 65.5 wt % (dry basis) while retaining the same fatty acid methyl ester profile, in addition to diminution of more than 70 wt % of ash compared to raw microalgae. Moreover, the hydrolyzate was directly used to grow a microalga of the same genus. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1494-1502, 2017 [ABSTRACT FROM AUTHOR]

Water under subcriticalconditions in a continuous-flow reactor(flash hydrolysis) has proved to be an efficient and environmentallyfriendly method for hydrolyzing proteins from microalgae biomass ina very short residence time (few seconds). In this study, flash hydrolysisexperiments were conducted at three different temperatures (240, 280,and 320 °C) and three residence times (6, 9, and 12 s) to understandthe kinetics of the hydrolysis of algae proteins to water-solublepeptides and arginine. Laboratory-grown protein-rich Scenedesmussp. with an average composition of 54% proteins, 17% lipids,and 23% carbohydrates was used as the feedstock. After flash hydrolysis,both liquid and solid products were collected, and the contents ofsoluble peptides and arginine in the liquid fraction and of remainingproteinaceous material in the solids were analyzed. For all experimentsabove 240 °C at all residence times, the yield of soluble peptideswas in the range of 57–67% of the algae protein, whereas themaximum arginine yield (81.51%) was achieved at 320 °C and aresidence time of 6 s. The protein solubilization to soluble peptidesfitted second-order reaction kinetics, whereas for arginine, the processwas zeroth-order; the activation energies were calculated to be 43.0and 34.1 kJ/mol, respectively. The results of this study suggest thatflash hydrolysis can be an environmentally benign method for hydrolyzingproteins from microalgae to produce valuable coproducts such as arginineas a free amino acid and water-soluble peptides along with lipid-richsolids (biofuel intermediate) as a feedstock for biofuel production. [ABSTRACT FROM AUTHOR]