Article

Development of hydrothermal liquefaction and upgrading technologies for lipid-extracted algae conversion to liquid fuels

Pacific Northwest National Laboratory, Richland, WA 99354, USA
Algal Research (Impact Factor: 5.01). 10/2013; 2(4). DOI: 10.1016/j.algal.2013.07.003

ABSTRACT

Bench-scale tests were performed for lipid-extracted microalgae (LEA) conversion to liquid fuels via hydrothermal liquefaction (HTL) and upgrading processes. Process simulation and economic analysis for a large-scale LEA HTL and upgrading system were developed based on the best available experimental results. The system assumed an LEA feed rate of 608 dry metric tons/day and that the feedstock was converted to a crude HTL bio-oil and further upgraded via hydrotreating and hydrocracking to produce liquid fuels, mainly alkanes. Performance and cost results demonstrated that HTL and upgrading is effective for converting LEA to liquid fuels. The liquid fuels annual yield was estimated to be 26.9 million gallon gasoline-equivalent (GGE) and the overall energy efficiency on a higher heating value (HHV) basis was estimated to be 69.5%. The variation range of the minimum fuel selling price (MFSP) was estimated to be $2.07 to $7.11/GGE by combining the effects of selected process factors. Key factors affecting the production cost were identified to be the LEA feedstock cost, final products yields, and the upgrading equipment cost. The impact of plant scale on MFSP was also investigated.

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    • "Moreover, most of these works investigated only part of the whole process [18] [19]. Zhu et al. performed an economic study of the HTL conversion and bio-oil upgrading of lipid-extracted microalgae and found minimum renewable diesel selling price between V0.43 and V1.50/L (V11.2 and V38.5/GJ) [17]. Similarly, Thilakaratne et al. evaluated the catalytic pyrolysis of lipid-extracted microalgae [19]. "
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    ABSTRACT: Renewable diesel productions through HTL (hydrothermal liquefaction) and pyrolysis of Chlamydomonas reinhardtii were compared based on energetic and economic evaluation. The whole biofuel production pathway was simulated, from the microalgae cultivation step to the upgrading of the bio-oil. Alternative dewatering technologies were evaluated to decrease the energy consumption and the bio-diesel cost. Thermochemical models were developed for both HTL and pyrolysis of C. reinhardtii based on experimental results. The pathways using heat exchangers between the inlet and outlet of the HTL reactor were the only scenarios to be net energy producers. The other pathways consumed more energy than they produced. The costs of production of renewable diesel from HTL or pyrolysis were significantly higher than petroleum diesel (average of 70.4 €/GJ). The most expensive step was the microalgae cultivation (nutrients cost and raceway capital cost).
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    • "Further techno-economic and life cycle assessments arrive at similar conclusions, regarding lipid extraction as an energy and capital intensive aspect of algae based biofuel production [15] [16]. Recent developments in hydrothermal liquefaction (HTL) of algae biomass may improve the energy balance of algae generated biofuels when compared with biodiesel production after lipid extraction [17] [18] [19] [20] [21]. With HTL technological advances for whole algal biomass conversion into fuels, selection of lipid-producing algae becomes less critical and biomass productivity becomes the primary selection criterion. "
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    ABSTRACT: Night biomass loss in photosynthetic algae is an essential parameter that is often overlooked when modeling or optimizing biomass productivities. Night respiration acts as a tax on daily biomass gains and has not been well characterized in the context of biomass production for biofuels. We examined the night biomass loss in three algae strains that may have potential for commercial biomass production (Nannochloropsis salina — CCMP1776, Chlorella sorokiniana — DOE1412, and Picochlorum sp. LANL-WT). Biomass losses were monitored by ash free dry weight (AFDWmgL−1) and optical density (OD750) on a thermal-gradient incubator. Specific night biomass loss rates were highly variable (ranging from −0.006 to −0.59day−1), species-specific, and dependent on both culture growth phase prior to the dark period and night pond temperature. In general, the fraction of biomass lost over a 10h dark period, which ranged from ca. 1 to 22% in our experiments, was positively correlated with temperature and declined as the culture transitioned from late exponential to linear to late linear phase. The dynamics of biomass loss should be taken into consideration in algae strain selection, are critical in predictive modeling of biomass production based on geographic location, and can influence the net productivity of photosynthetic cultures used for bio-based fuels or products.
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    • "Valdez et al. (2014) presented a reaction network and kinetic model to describe HTL of any algae species. Some researchers investigated the performance of lipid-extracted algae under hydrothermal conditions and the reaction behavior of residual algae after extracting polysaccharides (Miao et al., 2012; Valdez et al., 2012; Zhu et al., 2013). Biller and Ross (2011) found that the bio-oil yield from a range of model biochemical components at 350 °C followed the trend lipids > proteins > carbohydrates. "
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    ABSTRACT: Crude polysaccharides and proteins extracted from algae were chosen as model materials to investigate the hydrothermal liquefaction (HTL) characteristics and pathways of low-lipid algae. Liquefaction behavior of the two individuals and their binary mixtures with different mass ratios were evaluated under different temperatures. Formation pathways of bio-oil from crude polysaccharides/proteins were proposed. Results showed that polysaccharides had a small contribution to bio-oil (<5%) and approximately 60% distributed in aqueous phase, while proteins played a crucial role on bio-oil formation (maximum 16.29%). Bio-oil from polysaccharides mainly contained cyclic ketones and phenols and from proteins composed of pyrazines, pyrroles and amines. Interaction between polysaccharides and proteins forming polycyclic nitrogenous compounds had a negative effect on bio-oil yield at 220 and 260°C. However, their further decomposition caused increase of bio-oil yield at 300°C. Mixture liquefaction obtained the highest higher heating value (HHV) of bio-oil and energy recovery than polysaccharides/proteins liquefaction at 300°C. Copyright © 2015 Elsevier Ltd. All rights reserved.
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