Comparison of biocrude oil production from self-settling and non-settling microalgae biomass produced in the Qatari desert environment

Abstract

The present study investigated the growth, harvesting, biocrude conversion, and recycling of the HTL aqueous phase for one self-settling (i.e., Chlorocystis sp.) and another non-settling (i.e., Picochlorum sp.) marine microalgae. Both the strains were grown simultaneously in 2 identical 25,000-L raceway ponds in the Qatari desert. The cell size of Picochlorum sp. was small (2-3 µm), and its biomass was harvested using a centrifuge. Cells of Chlorocystis sp. (6-9 µm) formed flocs that settled spontaneously in a sedimentation chamber. Harvested biomass of these two strains was then converted to biocrude oil, using a 500-mL Parr reactor. The biocrude yield of Picochlorum sp. and Chlorocystis sp. was 39.6 ± 1.15% and 34.8 ± 1.65%, respectively. The energy content of the biocrude oil was 32.78 and 33.38 MJ/kg for Chlorocystis sp. and Picochlorum sp., respectively. Both the strains were capable of efficiently utilizing more than 95% nitrogen of the HTL aqueous phase. Although lower biocrude yield was obtained from Chlorocystis sp., compared to Picochlorum sp., harvesting of Chlorocystis sp. would require much lower energy compared to Picochlorum sp. Therefore, a self-settling microalgae (e.g., Chlorocystis sp.) could potentially be a better candidate, over non-settling microalgae, for producing biofuel feedstock.

Biolubricant Synthesis by Additization and Chemical Modification from Lipid-Rich Brackish Coelastrella sp. Using a Biorefinery Approach

“…were extensively grown in the Qatari desert environment. 51,52 The biomass densities found in outdoor 25000 L raceway ponds (Figure 1c,d) for all three strains were lower than those found in 1 L indoor PBRs. Among the three strains selected for outdoor cultivation, Coelastrella sp.…”

The Potential of Marine Microalgae for the Production of Food, Feed, and Fuel (3F)

“…Hydrothermal liquefaction (HTL) is a promising technology that can convert a variety of biomass, including microalgae, into biocrude oil in the presence of heat and pressure where the moisture in the biomass act as a solvent [173,174]. Under optimized conditions, the HTL process could recover more than 80% of the calorific value of the microalgal biomass feedstock [175].…”

Energy recovery and nutrients recycling from municipal sewage sludge

“…In a recent study, it was shown that Picochlorum sp. could efficiently utilize the nutrients in the aqueous phase-derived from the HTL of its biomass (Das et al, 2019b). Although the concentrations of nitrogen in both these cultures were the same, the aqueous phase liquid had dissolved organics; therefore, Picochlorum sp.…”

“…Although the toxic wastewater could be treated using microalgae, the produced biomass could have some estrogenic effect and hence should not be used for human and animal consumption (Correa-Reyes et al, 2007;López-Pacheco et al, 2019b). Nonetheless, the produced microalgal biomass, by using APL nutrients, could be used as biofuel feedstock (Das et al, 2019b), biofertilizer (Das et al, 2018b), and feedstock for many other renewable chemicals (Foley et al, 2011).…”

“…The addition of APL in microalgal growth media could not only treat the APL, but also allow the recycling of N, P, and other trace metals in a single process; this could enhance the environmental sustainability of the sludge management and promote a circular economy. Although microalgae were used to recover the nutrients from the microalgae biomass-derived APL (Das et al, 2019b(Das et al, , 2020, there is a need to study the feasibility of growing microalgae using MSSderived APL. For comprehensive management of MSS, detailed characterization of biochar would be required so that an appropriate application of biochar could be proposed.…”