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Microalgae are a promising biofuels feedstock, theoretically yielding concentrations of triacylglycerides (TAGs) per unit area that are far higher than traditional feedstocks due to their rapid growth. Dunaliella is particularly advantageous as a feedstock because it is currently commercially mass cultured, thrives in salt water, and has no cell wall. Fourteen strains of Dunaliella have been investigated for growth rates and lipid production in mass culture and tested for enhanced lipid production under a range of environmental stressors including salinity, pH, nitrogen and phosphorus limitation, and light regime. The nuclear genome has been sequenced for four of these strains, with the objective of increasing carbon flux through genetic engineering. Electroflocculation followed by osmotic membrane rupturing may be a very energy and cost efficient means of harvesting the lipid bodies from Dunaliella. A technically feasible and scalable thermo-catalytic process to convert the lipids into replacements for liquid transportation fuels has been developed. The lipids were converted into long-chain alkanes through continuous thermal hydrolysis followed by fed-batch thermo-catalytic decarboxylation. These alkanes can be reformed into renewable diesel via conventional catalytic hydrocarbon isomerization reactions to improve cold flow properties, if desired. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 916-925, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The liquid-phase deoxygenation of stearic, oleic, and linoleic acids employing a 5wt% Pd/C catalyst was investigated using on-line quadrupole mass spectrometry (QMS). Catalytic deoxygenation of stearic acid (SA) under He occurs primarily via decarboxylation; the liquid products are n-heptadecane and heptadecenes. On-line QMS revealed concomitant CO2 and H2 evolution which can explain the greater than expected heptadecene yields at low to intermediate conversions. After essentially complete SA conversion, hydrogenation of heptadecenes via hydrogen transfer from the dodecane solvent results in 98% n-heptadecane yield. The initial rate of SA decarboxylation under 10% H2 is lower than under He; however, by avoiding the formation of unsaturated products the reaction requires much less time to reach completion. The SA decarboxylation rate under 10% H2 is 6-fold slower in heptadecane than in dodecane. This apparent solvent effect is explained by the lower vapor pressure of heptadecane resulting in greater H2 inhibition of the decarboxylation reaction. Our results demonstrate that the unsaturated C18 free fatty acids, oleic and linoleic, must be hydrogenated to SA before decarboxylation can proceed at a significant rate. Oleic acid (OA) deoxygenation under He occurs very slowly and primarily via decarbonylation. In contrast, OA deoxygenation under 10% H2 occurs facilely via hydrogenation to SA followed by decarboxylation. Since hydrogenation is complete during heating to reaction temperature, the decarboxylation kinetics and product yields are not affected by the initial unsaturation of the reactant. [Copyright &y& Elsevier]