Hydrothermal Liquefaction Research Articles

Hydrothermal liquefaction of plastic marine debris from the North Pacific Garbage Patch

Ocean plastic waste poses a growing environmental threat, efforts are now underway to help clean the ocean surface or to prevent plastic streams entering. Repurposing these highly mixed polymers presents a great challenge due to their inherent complexity, intertanglement, and the presence of contaminants. Herein, we process real samples of ocean-floating plastics from the North Pacific Garage Patch through supercritical hydrothermal liquefaction (HTL), targeting their chemical recycling into synthetic crude oil. Investigating key process parameters (temperature, pressure, time, and plastic load), we found that plastic load and temperature are crucial parameters influencing oil yield and that moderate conditions maximized hydrocarbon yield, reaching 90 wt%. Overall, longer residence times and higher temperatures favored aromatic-rich oils. We suggest a reaction pathway to account for hydrogen release from aromatization reactions, influencing paraffin, olefin, and aromatic contents. Supercritical HTL offers an effective, tailored approach for recycling complex plastic mixtures to produce synthetic crude oil.

A critical review on hydrothermal liquefaction screening using Microalgae as a two-way approach to sewage water treatment and biofuel production

<p>Hydrothermal liquefaction (HTL) is involved in concurrently treating both sewage water and generating biofuels. It involves the analysis of various operating parameters, such as pressure, catalyst temperature, and reaction time, to determine the productivity and physiochemical properties of the resulting bio-oil. The critical assessment of over 100 algal strains, compared on the basis of their growth kinetics in different wastewater environments and their HTL-based yields, identified Auxenochlorella pyrenoidosa and Microchaete spirulina strains as the most suitable ones for optimised municipal wastewater treatment. Additionally, other strains like Chlorella sorokiniana, Tetradesmus obliquus, and Desmodesmus abundance are found to be effective for heavy metal remediation in municipal wastewater due to their high biosorption capacities. Furthermore, certain microalgal strains, namely Auxenochlorella pyrenoidosa, Botryococcus braunii, Microchloropsis gaditana, and Microchaete spirulina, were described as promising microalgae in the production of high crude oil yields through the HTL technique. The current review highlights the integrated approach of sustainable and economical HTL techniques using the best microalgal strains as a technologically and environmentally feasible solution selected through a systematic protocol for sewage water treatment and biofuel production.</p>

Algal-based biochar and hydrochar: A holistic and sustainable approach to wastewater treatment

Biochar and hydrochar are carbon-rich solid products of algal and terrestrial biomass obtained through various thermochemical processes, mainly hydrothermal liquefaction, pyrolysis, and hydrothermal carbonization. Both are regarded as economical, potent, and environmentally friendly adsorbents for wastewater remediation. The versatile applicability of biochar and hydrochar, which is due to their enhanced surface physicochemical properties, includes efficient metal biosorption, soil fertility enhancement, and carbon sequestration. Consequently, there has been an increase in research for producing and exploiting biochar and hydrochar from algae. Both micro- and macro-algal biomass have strong potential due to their sustainability footprint and distinct properties. This review focuses on a comprehensive account of the synthesis of algal biochar and hydrochar and use in wastewater treatment to develop innovative solutions for efficient mitigation of several aqueous pollutants and heavy metal ions. The review discusses the various thermochemical production routes, biophysical characterization techniques, and modes of mechanism for wastewater bioremediation. Algal-based biochar and hydrochar are reported to have higher porosity and more diverse functional groups such as amines, hydroxyl, and carboxyl compared to their cellulosic and waste-derived counterparts, demonstrating an increased wastewater remediation efficiency. In addition, presence of inorganic metal including sodium, potassium, magnesium, and phosphorus in algal chars facilitates the formation of mesopores and graphite structures, improving their cation exchange capacity. Moreover, algal chars may exhibit pH buffering capacity, which could help stabilize the pH during wastewater treatment processes. Notably, the low O/C content of algal hydrochars enhances the binding and removal of organic pollutants including toxic dyes and antibiotics. The review highlights the development of modified algal chars to enhance the porosity, surface area, structural integrity, and adsorption capacity enabling a higher bioremediation potential.

Machine learning and experiments on hydrothermal liquefaction of sewage sludge: Insight into migration and transformation mechanisms of phosphorus

Sewage sludge (SS), as a phosphorus (P)-rich wet biomass, can generate a large number of P-containing high-value by-products after converted to biofuel by hydrothermal liquefaction (HTL). However, the potential mechanisms of migration and transformation of phosphorus in this process are unclear due to the complexity of SS composition and HTL processes. In this work, Gradient Boosting Regression (GBR) algorithm was employed in machine learning (ML) models to investigate the impacts of input features on the phosphorus content and forms during HTL. Machine learning models showed good performance with an average training R2 > 0.95 and an average testing R2 > 0.85. Further, representative HTL conditions including temperature (270–350 °C) and residence time (20–60 min) were selected for experiment validation of studied mechanisms. The results indicated that with temperature and time increasing, phosphorus recovery (R_P) increased from 86.85 % to 92.65 % and the relative content of apatite inorganic phosphorus in hydrochar (APRC_HC) increased from 33.67 % to 39.06 %. The relative content of inorganic phosphorus in hydrochar (IPRC_HC) stabilized at 98 % at above 270 °C. 85 % of phosphorus in SS migrated to hydrochar after HTL, and most of P was in the form of IP. Ca3(PO4)2 and Ca4P6O19 were detected by X-ray diffraction (XRD). This information can provide significant theoretical support for phosphorus resource recovery in hydrochar derived from HTL of SS.

Ammonia recovery via stripping from hydrothermal liquefaction aqueous from sludge for anaerobic co-digestion pretreatment

Hydrothermal liquefaction (HTL) is a thermo-chemical method of processing wastewater solids that could be preferential over anaerobic digestion (AD) because it produces a greatly reduced volume of solids. Instead, the effluent can be separated into biocrude refined into fuel, hydrochar a carbon-rich solid and HTL aqueous waste. Unfortunately, HTL aqueous is high in ammonia, phenolics, and nitrogen heterocyclic compounds that can inhibit AD if used for treatment. Ammonia stripping was tested for pretreatment of HTL aqueous from dewatered mixed sludge at 350 °C, 15 min and recovering ammonia. Seven stripping reactor conditions were run, and the best results were seen at 85 °C, a pH of 9.3 and 500 mL/min air flow rate. This case achieved ammonia and total phenolic compounds removal of 79.5 ± 0.1 and 32 ± 1 %, respectively, in 4 h. The ammonia stripping was coupled with acid adsorption to produce an ammonium sulphate salt with fertilizer value. The ideal ammonia stripping conditions produced a salt with a purity of 98.0 ± 0.05 % and represented an ammonia recovery of 73.9 ± 0.04 %. Semi-continuous flow bench-scale thermophilic anaerobic co-digestion of HTL aqueous with municipal sludge found that 12 % of influent chemical oxygen demand (COD) can come from HTL aqueous without inhibition if pretreated with ammonia stripping, while the digester fed with a similar COD from non-pretreated HTL aqueous showed inhibition. Under mesophilic conditions, semi-continuous flow anaerobic co-digestion was successful for non-pretreated and pretreated HTL aqueous even with 24 % and 22 % of influent COD provided by HTL aqueous, respectively.

Fast hydrothermal co-liquefaction of high-ash sludge and Chlorella for biocrude production

Fast hydrothermal liquefaction (HTL) shows great potential for producing biocrude. This research examined the influences of mixing ratios of sludge and Chlorella during both isothermal (300 °C, 1800 s) and fast (500 °C, 20 s) co-HTL. Adding Chlorella could efficiently retard repolymerization reaction and increase the biocrude production. The highest co-liquefaction effect was achieved from a sludge to Chlorella ratio of 2:6 by fast HTL, producing a biocrude yield of 29.65 wt%, closely approaching the calculated yield of 29.39 wt% and demonstrating an additive effect. However, for the high ash content of sludge, all isothermal and other fast HTL conditions presented an antagonistic effect on biocrude production. Meanwhile, co-liquefaction also exhibited a slight antagonistic effect on the heating value and energy recovery of biocrude, with experimental values reaching 32.73 MJ·kg−1 and 52.74 %, respectively. FT-IR and maturity analyses indicated that compared to isothermal co-HTL, fast co-HTL biocrude was more favorable for the conversion into gasoline/diesel due to its lower paleo-temperature. GC–MS analysis identified amides (isothermal co-HTL) and nitrogen heterocycles (fast co-HTL) as the dominant components, suggesting that the holding time significantly influenced the competition of Maillard and amidation reactions. Besides biocrude, the major composition of aqueous phase products (APs) was also nitrogen heterocycles. Notably, fast co-HTL induced a substantial decrease in COD, NH3-N, and TN contents of APs, reducing the discharge challenge of the by-products.

Adsorption enhanced biological treatment of hydrothermal liquefaction aqueous phase derived from municipal sludge

Hydrothermal liquefaction (HTL) is a promising method for municipal sludge valorization through waste minimization and biofuel production. The process wastewater, HTL aqueous, presents a significant challenge for scale-up due to recalcitrant compounds. In this study, granular activated carbon (GAC) was used to remove potential inhibitors from HTL aqueous through adsorption to enhance aerobic and anaerobic biological treatment. GAC removed up to 61 % chemical oxygen demand (COD), 50 % biochemical oxygen demand (BOD) and potential inhibitors, such as total phenolic compounds (87 %) and N-heterocycles (90 % of pyridines) at 100 g/L. Conversely, most volatile fatty acids remained in HTL aqueous. Subsequently, mesophilic and thermophilic specific methane potential increased by up to 97 % and 83 %, respectively. BOD increased by up to 50 %, which enhanced BOD/COD ratio from 81 % to 93 % before and after adsorption. This study established the groundwork for HTL aqueous adsorption, described mechanism for pollutant removal, and provided insights for biological treatment.

Co-hydrothermal liquefaction of waste biomass: Comparison of various feedstocks and process optimization

Hydrothermal liquefaction (HTL) is a promising method for converting biomass into biocrude, utilizing moderate temperatures (250–350 °C) and high pressures (10–25 MPa) near the solvent's critical point, typically water. This study assesses various waste biomass feedstocks under identical HTL conditions (T = 280 °C, P = 12 MPa, time = 30 min). Mustard meal exhibited the highest biocrude yield (38 wt%), followed by canola meal (27 wt%), attributed to their high lipid contents. Co-HTL using different ratios of mustard and canola meals showed that a 1:3 ratio produced biocrude with the lowest heteroatom content. Optimization of temperature (260–340 °C), reaction time (0–45 min), and solvent-to-biomass ratio (3–9) revealed that biocrude with minimal oxygen content and significant yield was achieved at 320 °C, 30 mins, and a 5:1 water-to-biomass ratio. The physicochemical properties of biocrude and bio residues were evaluated for potential applications.

A Nature-Inspired Design for Sequestering Polycyclic Aromatic Hydrocarbons in Asphalt-Surfaced Areas

Asphalts for pavement and roofing are known to emit volatile organic compounds (VOCs), contributing to air pollution, including the formation of ozone and secondary organic aerosols, which further worsen air quality. These emissions become more pronounced with higher sun intensity and higher temperature, accelerating the loss of essential components and the aging of bitumen. Consequently, the durability and functionality of bitumen are compromised. In this study, we investigate the efficacy of nitrogen-carrying functional groups in biochar at retaining VOCs in bitumen and prolonging the service life of asphalt surfaces. Biochar derived by hydrothermal liquefaction of red microalgae, rich in N-functional groups, is compared with low-N biochar obtained through acid-washing. Laboratory tests demonstrate that bitumen modified with high-N biochar exhibits greater resistance to aging after 200 h of ultraviolet radiation exposure compared to bitumen modified with low-N biochar. The values of an aging index based on the crossover modulus and an aging index based on the crossover frequency indicate greater susceptibility to aging in neat bitumen compared to biochar-modified bitumen, and bitumen modified with high-N biochar showed the lowest aging index. Compared to neat bitumen, measurements of carbonyl and sulfoxide as aging indicators showed an improvement of 12.9% for high-N biochar in slowing bitumen aging, while low-N biochar provided only a 3.1% improvement. Dynamic vapor sorption analysis showed 35% less mass loss in bitumen with high-N biochar compared to bitumen with low-N biochar. These improvements can be attributed to the increased retention of VOCs in bitumen facilitated by the N-functional groups in high-N biochar. Modeling with density functional theory shows the mechanisms by which biochar rich in N-functional groups exhibits enhanced adsorption of VOCs. This modeling highlights the importance of biochar's nitrogen functional groups in biochar's electronic structure and molecular structure in retaining VOCs in the bitumen matrix. The study outcomes promote sustainability and resource conservation in the construction industry and align with goals of carbon neutrality.

On application of molecular dynamics simulation for studying the effect of temperature and heating rate on HTL of biomass

Abstract Hydrothermal liquefaction (HTL) of biomass has garnered increasing attention as a promising pathway for converting solid biomass to liquid biofuels and valuable chemical products. HTL involves processing of biomass in water at high-temperature and high-pressure conditions. The heating rate during this process plays a critical role in determining the yield and composition of the liquefied products. To probe the impact of heating rate, we develop a detailed atomistic model biomass by using cellulose as model compound and place it in a simulated HTL reactor. Our Reactive molecular dynamics simulations are capable of capturing the dynamic chemical reactions and structural changes during HTL. The effect of reaction temperature and heating rates on reaction pathways, product distributions, and reaction kinetics is rigorously analyzed. Our findings reveal that the reaction temperature and heating rate significantly influences the extent of cellulose degradation and the composition of bio-oil product.

Optimization of bio-oil production from macroalgae, caulerpa lentillifera via hydrothermal liquefaction

Abstract An environmentally friendly method of producing bio-oil through the hydrothermal liquefaction (HTL) of algae has emerged, providing a path toward renewable energy and reducing greenhouse gas emissions. Algae is currently received a lot of interest as biomass feedstock due to its long growing season in warm climate area, does not require arable land, and relatively rapid growing rate. This study aims to optimize the HTL process of macroalgae (Caulerpa lentillifera) for bio-oil production, focusing on optimizing the bio-oil yield based on three parameters (operating temperature, the loading size of catalyst sodium hydroxide (NaOH), and algae-to-water ratio) using Box Behnken Design (also generally known as Response Surface Methodology). The results showed that an ideal reaction temperature of 277 °C, a 1:10 algae-to-water ratio, and 0.88 wt% catalyst loading led to an optimal experimental bio-oil yield of 11.65 wt%. Sensitivity study also revealed that the temperature is the second most important component, after the algae-to-water ratio. The difference in the catalyst loading showed low impact on the HTL of algae. Slight improvement to the bio-oil yield under the presence of NaOH is mainly due to the alkali environment provided by NaOH. The FTIR spectrum revealed the existence of various functional groups in the bio-oil. In summary, HTL has been effective in turning Caulerpa lentillifera into useful bio-oil. Overall, this study contributes to the growing body of research on algae-based bio-oil production. The results highlighted the potential of HTL as a promising technology for sustainable biofuel production, offering a pathway towards a greener and more energy-efficient future.

Advancing biorefinery technologies through transesterification and hydrothermal liquefaction for biodiesel and bioproducts production

BackgroundThe multicriteria assessment of advancing biorefinery to produce biodiesel (fatty acid methyl ester), glycerol, and torrefied pellets is a strategic approach towards sustainable development. MethodsA successive transesterification process was applied to separate lipids with alcohol, with a 1:7 mass-to-mass ratio in the presence of a heterogeneous catalyst of chitosan/polyvinyl alcohol-sodium hydroxide (CS/PVA-NaOH), to produce biodiesel and glycerol. Moreover, the remaining biomass is extracted to produce torrefied pellets by applying torrefaction through hydrothermal liquefication at 200–300 ℃ temperature. The biorefinery system using 613 kg organic fraction of municipal solid waste (OFMSW) produced 127.3 L of biodiesel, 14.5 kg of glycerol, and 387.5 kg of torrefied pellets. The whole systematic approach revealed two distinct areas with required characterized equipment such as dryer (A = 721.28m2), suspended in tank (V = 751.56m3), reactor (V = 721.56m3), cyclone (A = 743.48 m2), grinder (Q = 1352.31 m3/h), compactor (Q = 1367.31 m3/h), correspondingly. A gate-to-gate life cycle assessment (LCA) was performed for life cycle impact assessment (LCIA) through GaBi by using the ReCiPe 2016 Mid-point (H) and Endpoint (H) approach with a functional unit of 1000 kg municipal solid waste (MSW). Significant findingsThe economic assessment reveals the economic feasibility of the biorefinery project. The annual revenue determined the profitability index, which is $ 1.59 million annually, with a payback period of 1.8 years. The environmental analysis determined an eco-friendly production unit which can save 13.6% of carbon emissions by alternate use of photovoltaic energy. Conclusively, the calculated values and findings prove that biorefinery development using OFMSW is scientifically a win-win situation and notably assists in achieving circular bioeconomy and sustainable development goals (SDGs).

The fate of Volatile Fatty Acids (VFAs) during the thermodynamic transition from hydrothermal carbonization to hydrothermal liquefaction: HtC-to-HtL

The valorization of biomass via hydrothermal treatment, a green and reliable thermochemical process, produces high-value chemicals. This study focuses on the transformation of Volatile Fatty Acids (VFAs) during the transition from Hydrothermal Carbonization (HTC) to Hydrothermal Liquefaction (HTL) and their impact on product quality. Conducted with anaerobically digested sewage sludge, the hydrothermal treatment varied temperatures from 280 °C to 340 °C. The primary objective was to investigate VFA concentrations and their link to hydrochar yield and gaseous by-product composition. A high-performance Parr 4577A hydrothermal reactor facilitated these experiments. For VFA assessment, a Shimadzu Nexis 2030 plasma GC-BID with an HP-FFAP column was utilized for the first time. The study revealed a U-shaped COD concentration curve (peaking at 10,510 mg/l at 340 °C) and an S-shaped Total Phenols profile (highest at 1314 mg/l at 325 °C). Notably, VFA concentrations dipped significantly at 295 °C and 325 °C but were higher at other temperatures, suggesting a complex underlying mechanism. This variability is partially attributed to the reduction in hydrochar mass yield with increasing temperature (46% at 280 °C to 31% at 340 °C) and a surprising spike in CO2 concentration (90% at 310 °C). These findings emphasize the critical role of carboxylation reactions in the HTC-to-HTL transition, enhancing the quality of liquid hydrothermal products.

Renewable diesel blends production from hydrothermal liquefaction of food waste: A novel approach coupling fractional distillation and emulsification

Hydrothermal liquefaction (HTL) is a promising approach for producing biocrude oil from wet biowaste, but the suboptimal properties of HTL biocrude hinder its direct utilization as transportation fuel. This study presents an innovative approach by integrating fractional distillation and emulsification to upgrade HTL biocrude derived from food waste into renewable diesel blends. Fractional distillation is effective in removing metals, heavy fractions, and impurities, thus improving the physicochemical properties of the biocrude. Subsequent emulsification of distillates (10–30 wt%) with diesel, using Atlox 4912 as the surfactant, ensures a homogeneous mixture. The solubility of biocrude in diesel increased from 34.80 wt% to 100 wt% after distillation. Compared to direct HTL biocrude emulsification, distillate emulsion exhibited a 17.22% and 20.89% reduction in oxygen and nitrogen content, respectively, as well as significant improvements in terms of higher heating value, carbon and energy recoveries, and reduction of metal elements. The resulting emulsion demonstrated comparable viscosity, molecular weight, and boiling point distributions to the commercial diesel. Moreover, the oxidation and thermal stability tests revealed superior performance of distillate emulsion, with no observable sedimentation during the storage period. In contrast, direct biocrude emulsion experienced 14.37 wt% of phase separation. The mechanism of emulsion aging was then investigated, providing the basis for obtaining emulsions with preferable yield and quality. The comparative evaluation in this study showed that the integrated approach of fractional distillation and emulsification enhances the feasibility and quality of producing renewable diesel blends from HTL biocrude.

Algal biomass based bio-refineries: Concurrent pre-treatment strategies and perspectives for sustainable feedstock

The quest for viable and scalable biofuel sources has been at the forefront of scientific innovation for the past three decades. Due to its rich chemical constituents, microalgal biomass has emerged as a pivotal sustainable and scalable feedstock for biorefineries. This comprehensive review critically analyzes the different types of microalgae feedstock, concurrent extraction technologies, bio-pre-treatment procedures, and the key chemical and physical parameters influencing lipid formation and algal biofuel production. We propose a novel approach of photo-initiated culturing of algal biomass using photobioreactors (PBRs) to address the limitations of concurrent space and time-related constraints. The innovative photo bio-refinery strategy presented herein aims to enhance sustainability factors while minimizing emissions, catering to the needs of futuristic non-electric vehicles. A comparative quality analysis of microalgae-derived biofuel against conventional fossil fuels and other biofuels is conducted, considering chemical, environmental, economic, and social perspectives. Furthermore, we elucidate the efficacy of bio-pre-treatment strategies such as dehydration, hydrothermal liquefaction, pyrolysis, and gasification in optimizing biofuel production. The proposed photo biorefineries exhibit the potential to yield a diverse range of value-added products, including biodiesel, biogases, bio-fertilizers, bio-pesticides, bio-alcohols, dyes, proteins, carotenoids, and drug vitals. This review provides a comprehensive framework for the development of sustainable and efficient microalgae-based biorefineries, paving the way for a greener and more economically viable future in the biofuel industry.

Automated machine learning-aided prediction and interpretation of gaseous by-products from the hydrothermal liquefaction of biomass

Hydrothermal liquefaction (HTL) is a thermochemical conversion technology that produces bio-oil from wet biomass without drying. However, by-product gases will inevitably be produced, and their formation is unclear. Therefore, an automated machine learning (AutoML) approach, automatically training without human intervention, was used to aid in predicting gaseous production and interpreting the formation mechanisms of four gases (CO2, CH4, CO, and H2). Specifically, four accurate optimal single-target models based on AutoML were developed with elemental compositions and HTL conditions as inputs for four gases. Herein, the gradient boosting machine (GBM) performed excellently with train R2 ≥ 0.99 and test R2 ≥ 0.80. Then, the screened GBM algorithm-based ML multi-target models (maximum average test R2 = 0.89 and RMSE = 0.39) were built to predict four gases simultaneously. Results indicated that biomass carbon, solid content, pressure, and biomass hydrogen were the top four factors for gas production from HTL of biomass. This study proposed an AutoML-aided prediction and interpretation framework, which could provide new insight for rapid prediction and revelation of gaseous compositions from the HTL process.

Detection of volatile hydroperfluoroalkanes during hydrothermal liquefaction of perfluoroalkyl carboxylic acids at circumneutral pH

Hydrothermal liquefaction (HTL) is a promising technology for converting wet organic waste such as sewage sludge into biocrude oil while simultaneously destroying per- and polyfluoroalkyl substances (PFAS). This study tracked the fate and degradation of six representative PFAS in water to address the effect of perfluoroalkyl chain length on degradation rates and the formation of volatile transformation products at 300–350 °C. While perfluorosulfonic acids were recalcitrant, perfluoroalkyl carboxylic acids (PFCAs) were rapidly and completely decarboxylated to hydroperfluoroalkanes (1 H-perfluoroheptane in the case of perfluorooctanoic acid). The volatile hydroperfluoroalkane was subsequently defluorinated without detectable fluorocarbon intermediates yielding 30–60 % defluorination for ammonium perfluoro(2-methyl-3-oxahexanoate), perfluorobutanoic acid and perfluorooctanoic acid after 2 h at 350 °C. Increasing temperature (especially at 350 °C) and longer perfluoroalkyl chains substantially enhanced the defluorination. This is the first study to report volatile hydroperfluoroalkanes from PFCAs in HTL, raising concern about the potential emission of long-lived greenhouse gasses into the atmosphere, but also opening new avenues for PFAS destruction through HTL.

Hydrothermal liquefaction of swine wastewater-cultivated Chlorella sorokiniana SU-1 biomass for sustainable biofuel production

The environmental impact of fossil fuel consumption has shifted the focus of research toward biomass and bioenergy. Renewable biomass, such as microalgae, has several benefits, including growth in wastewater, sequestration of carbon dioxide, economic feasibility, and environmental friendliness. This study investigated the feasibility of using Chlorella sorokiniana SU-1 biomass cultivated on a swine-amended medium as a renewable feedstock to produce biocrude oil. Microalgal cultivation under optimal conditions of 50 % swine wastewater (SW), inoculum sizes of 1 g/L, CO2 concentration of 2 %, and light intensity of 300 μmol m−2 s−1 obtained a high biomass concentration (6.53 g/L), biochemical production (56.65 % carbohydrate content, 33.5 % protein content, and 4.35 % lipid content) and wastewater treatment performance [92.29 % chemical oxygen demand (COD) removal, 93.7 % total phosphorus (TP) removal, and 95.64 % ammonia removal]. Subsequently, hydrothermal liquefaction (HTL) of the obtained microalgal biomass achieved a 29.45 % biocrude oil yield with a composition of 34.3 % esters, 23.5 % hydrocarbons, 5.14 % aldehydes, 7.54 % furans, and 11.1 % phenolic derivatives, making it a promising choice for biofuel production. Thus, the findings confirmed that C. sorokiniana SU-1 could be effectively utilized for the phycoremediation of SW with simultaneous biomass production as a renewable feedstock for biocrude oil production.

Thermal and Oxidative Stability of Biocrude Oil Derived from the Continuous Hydrothermal Liquefaction of Spirulina

Thermal and Oxidative Stability of Biocrude Oil Derived from the Continuous Hydrothermal Liquefaction of Spirulina

Hydrothermal liquefaction of microalga with and without seawater: Effects of reaction temperature on yield and hydrocarbon species distribution in biocrude

AbstractA halophytic microalga Tetraselmis sp. biomass diluted with deionized water and seawater was converted to biocrude with the hydrothermal liquefaction (HTL) process in a batch reactor at 310, 330, 350, and 370°C, 15 min with %w/w solids. The biocrude yield, carbon, and energy recovery in biocrude and hydrocarbon species distribution from deionized water base HTL (DW HTL) and seawater base HTL (SW HTL) were evaluated. The results revealed that irrespective of reaction medium, the yield in biocrude increased with an increase in temperature, reaching a maximum of 50–56 wt% at 350°C, characterized by a higher heating value of up to 35.6 MJ/kg. The carbon and energy recovery at 350°C were 85% and 89% respectively, for SW HTL, while the DW HTL stream was 10% and 12% lower. Also, the GC MS analysis of biocrude obtained from both streams contains a complex mixture of compounds such as hydrocarbons, phenolics, and large amounts of nitrogenated and oxygenated compounds. The metallic constituents in biocrudes derived from both steams showed no substantial variations. The study showed a marginal increase in biocrude yield and its HHV with a reduction in oxygen and nitrogen contents from the SW HTL stream, suggesting the potential of seawater as a reaction medium.