Temperature effect on hydrothermal liquefaction of Nannochloropsis gaditana and Chlorella sp.

Abstract

Temperature effect on hydrothermal liquefaction (HTL) of Nannochloropsis gaditana and Chlorella sp. was investigated with 10% biomass loading at HTL temperatures of 180-330 o C, and reaction time of 30 minutes. Maximum yields of 47.5% for Nannochloropsis sp. and 32.5 % biocrude oil yields for Chlorella sp. were obtained at 300 o C. The higher heating values of biocrude oils produced in this work ranged between 34 and 39 MJ/kg. 79% of energy in the Nannochloropsis sp. was recovered at 300 o C and 62% of energy recovery from Chlorella sp. was achieved at 200 o C. Valuable nutrients (NH 3-N and PO 4 3-) produced during the HTL process were quantified from the aqueous phase for both strains of biomass. The aqueous phase samples obtained at all temperatures were also analyzed for amino acids and carbohydrates. The suitable temperatures for extraction of lipids, amino acids and carbohydrates have been identified. Sequential HTL experiments conducted have shown the prospect of recovering nutrients and other valuable byproducts along with biocrude oil. The experimental results and analysis indicate that sustainable biofuel production requires the development of strain based strategies for the hydrothermal liquefaction process.

Pilot-Scale Continuous-Flow Hydrothermal Liquefaction of Filamentous Fungi

“…6 Increased lipid content is desirable since biocrude production has been demonstrated to come primarily from lipids, followed by proteins, and then carbohydrates. 8,27,38 Compared to other fungal species used in HTL studies, R. oligosporus contained a significantly higher lipid content than yeast Saccharomyces cerevisiae (2.7%), 30 and less than the oleaginous yeast Cryptococcus curvatus (32.8%). 32 Relative to other feedstocks used in continuous-flow HTL systems, the lipid content of R. oligosporus was comparable to that of microalgae, 12 specifically, Chlorella (25%) 8 and Nannochloropsis (28%).…”

Continuous Hydrothermal Liquefaction for Biofuel and Biocrude Production from Microalgal Feedstock

“…It is apparent that some solid product holding‐up occurs inside the continuous reactor system, especially in the cooler piping downstream of the heat recovery and the pressure let‐down stages , . Reddy et al have found an average HHV for solid residue (biochar) of 19.21 – 12.54 MJ kg −1 and 19.82 – 12.05 MJ kg −1 for Nannochloropsis gaditana and Chlorella sp., respectively. However, general observations have shown small amounts of solid residues after HTL, normally less than 10 % .…”

“…Reddy et al have found an average HHV for solid residue (biochar) of 19.21 – 12.54 MJ kg −1 and 19.82 – 12.05 MJ kg −1 for Nannochloropsis gaditana and Chlorella sp., respectively. However, general observations have shown small amounts of solid residues after HTL, normally less than 10 % . The biochar contains high amounts of the crude protein.…”

“…Moreover, biocrude upgrading for drop-in fuel production as well as the reduction of Figure 1. (a) Conceptual and (b) pictorial framework for conversion of microalgae biomass to the bio-energy; adapted from [11,22,24,33,[43][44][45][46][47].…”

“…(a) Conceptual and (b) pictorial framework for conversion of microalgae biomass to the bio‐energy; adapted from , , , , .…”