Hydrothermal Liquefaction Biocrude Research Articles

Understanding the Miscibility and Co-feeding Potential of Hydrothermal Liquefaction Biocrude in Refinery Streams: Role of Hydrodeoxygenation

Understanding the Miscibility and Co-feeding Potential of Hydrothermal Liquefaction Biocrude in Refinery Streams: Role of Hydrodeoxygenation

Upgrading of hydrothermal liquefaction biocrudes from mono- and co-liquefaction of cow manure and wheat straw through hydrotreating and distillation

Liquid hydrocarbons from agricultural wet wastes can serve as a strategy to greatly reduce CO2 emissions. This study presents the upgrading via catalytic hydrotreatment of hydrothermal liquefaction (HTL) biocrudes derived from cow manure, wheat straw and their combined liquefaction (co-HTL). Four different temperatures were tested (340, 360, 380 and 400 °C) at constant hydrogen and biocrude flowrate. The co-HTL biocrude contained more recalcitrant nitrogen-containing molecules towards hydrotreatment, which caused decreased hydrogen consumption and overall lower quality of upgraded products. Generally, upgraded products were obtained with >80 wt% carbon yields based on biocrude input. Products of hydrotreatment at 400 °C were distilled into four cuts. Increased hydrotreatment temperature improved physicochemical properties of upgraded products, leading to generally higher yields of gasoline and kerosene through significant cracking of bottom residues. Bottom residues derived from single feedstock HTL biocrudes were totally miscible with fossil-derived vacuum gas oil at room temperature, while the co-HTL derived one required increased temperature for total solubility. We show that the co-HTL approach leads to a higher production of the diesel and bottom residue fractions. Overall, single feedstock HTL resulted in a carbon yield from biomass to upgraded oils of 34 and 38 % respectively for wheat straw and cow manure, while the co-HTL approach increased this value to 43 %. The combination of agribusiness waste for HTL processing is shown here to be an attractive solution for wet waste processing and carbon recovery towards advanced biofuels.

Understanding the Upgrading of Sewage Sludge-Derived Hydrothermal Liquefaction Biocrude via Advanced Characterization.

Hydrothermal liquefaction (HTL) can thermochemically transform sewage sludge into a biocrude with high energy content, high chemical complexity, and high O and N content. The development of an efficient upgrading process for such complex feedstocks necessitates detailed knowledge of the molecular composition and the specific heteroatom-containing compounds to understand and optimize the hydrotreating reactions. In this study, we present the upgrading of sewage sludge-derived HTL biocrude via a two-stage hydrotreatment process and perform advanced chemical characterization of the feedstock, intermediate, and final upgraded products with gas chromatography–mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR–MS). We show that hydrotreatment significantly improves the quality of the oil, primarily succeeding in cracking the heavy molecules and removing the sulfur- and oxygen-containing components. FTICR–MS analysis shows that the HTL biocrude has a high concentration of fatty acid amides that readily lose their oxygen and nitrogen during hydrotreating and are converted into saturated hydrocarbons, whereas the aromatic OxNy compounds are converted into N1 and N2 classes, which are more resistant to hydrotreating. We also demonstrate that the upgraded HTL oil can be successfully blended with intermediate refinery streams, such as vacuum gas oil (VGO), for further co-processing to in-spec fuels in conventional processes. This provides an alternative route to introduce renewable carbon in existing fossil-based refineries.

Biofuel potential of liquid products from protein- and lipid-rich biomass hydrothermal liquefaction

Hydrothermal liquefaction (HTL) of oleaginous microorganisms is an economical method with which to transform all compounds of wet biomass into competitive biofuels without the need for pretreatments such as feedstock drying and lipid extraction. In the present work, liquefaction of microalgae or yeasts in subcritical water is investigated in a self-built HTL system. Fractional yield distribution of the end-products and characterization of biocrudes from algae HTL are studied by considering the effects of the reaction temperature and residence time. The identified compounds in the biocrudes are compared to those in yeast-derived HTL biocrudes and the reaction scheme is reported. The present work reveals that no significant quality change of algae-derived HTL biocrudes is observed in a moderate temperature range thus the N-containing compounds vary complicatedly at different residence times. Compared to the pyrolysis biocrudes of algae and yeast, the collected HTL biocrudes do not perform the advantage, in terms of biofuel potential of a high portion of N-containing compounds, especially heterocyclic compounds. It should be noted that the low protein content in the feedstocks cannot definitely be proven to have led to the reduced heterocyclic compounds in HTL biocrudes. If lipids had been present, this would have enhanced the formation of N-containing heterocyclic compounds. Instead, amino acid degradation was accelerated by the high level of carbohydrates, forming amides. This paper presents a promising effort to develop an efficient route to transform oleaginous microorganisms into biofuels.

Diesel blends produced via emulsification of hydrothermal liquefaction biocrude from food waste

Hydrothermal liquefaction (HTL) is a promising method for producing biocrude oil from wet biowaste. However, the complex composition of the HTL biocrude has several undesirable qualities, including high viscosity, total acid number (TAN), oxygen and nitrogen heteroatom content, and lesser higher heating value (HHV) in comparison to petroleum fuels. This study investigated the production of diesel blends and their fuel quality by emulsification of HTL biocrude with the aid of a block copolymer surfactant through centrifugation and ultrasonification. Four emulsion treatment variables were considered: biocrude fraction, surfactant fraction, retention time, and RPM (rotations per minute) for centrifuge or temperature for ultrasonic. Emulsification produced fuel blends with better HHV, viscosity, and TAN in comparison to HTL biocrude oil, and high solubility levels were achieved with surfactant addition and increased retention time. Maximum biocrude solubilities of 65.43 and 75.67 wt% were obtained for centrifugation and ultrasonification, respectively. Meanwhile, the highest HHV of centrifuge and ultrasonic emulsions was 45.39 and 45.73 MJ/kg, respectively. Emulsification led to viscosities as low as 5.91 and 6.06 mm2/s for centrifuge and ultrasonic samples, respectively. The TAN of emulsions were much lower than the biocrude: 14.18–41.31 and 16.22–50.31 mg KOH/g for centrifugation and ultrasonification, respectively. Thermogravimetric analysis, elemental analysis, combustion characteristics, and thermal properties gave further insight into the fuel quality of the emulsions and any deviations from the predicted HHV, viscosity, and TAN fuel properties, as well as comparison to ASTM specifications for biodiesel blends. The results show that emulsification of HTL biocrude could be an efficient and economical pathway for producing renewable diesel blends.

Co-Solvent Assisted Hydrothermal Liquefaction of Algal Biomass and Biocrude Upgrading

This study reports the hydrothermal liquefaction (HTL) of microalgae Spirulina platenesis in the presence of alcohol or formic acid co-solvents. HTL runs are performed in a 1.8-L batch reactor at 300 °C using an alcohol (methanol and ethanol) or formic acid co-solvent. Consequently, hydrodeoxygenation (HDO) of resultant algal biocrude is performed at 350 °C for 2 h under high hydrogen pressure (~725 psi) using the Ru/C catalyst. The HTL results are compared with the control HTL run performed in water only. The results of the study show that the addition of co-solvents leads to a 30–63% increased biocrude yield over the control HTL run. Formic acid results in a 59.0% yield of biocrude, the highest amongst all co-solvents tested. Resultant biocrudes from formic acid-assisted and ethanol-assisted HTL runs have 21.6% and 3.8–11.0% higher energy content, respectively, than that of the control run. However, that of the methanol-assisted HTL results in biocrude with 4.2–9.0% lower energy density. Viscosity of biocrude from methanol- or ethanol-assisted HTL is higher than the control HTL but formic acid-assisted HTL results in a less viscous biocrude product. In addition, the HDO study leads to a 40.6% yield of upgraded oil, which is characterized by a higher net energy content and lower O/C and N/C ratios when compared to the initial HTL biocrude.

Coupling hydrothermal liquefaction and aqueous phase reforming for integrated production of biocrude and renewable H2

AbstractLignin‐rich stream from lignocellulosic ethanol production was converted into biocrude by continuous hydrothermal liquefaction (HTL) while hydrogen was produced by aqueous phase reforming (APR) of the HTL aqueous by‐product. The effects of Na2CO3 and NaOH were investigated both in terms of processability of the feedstock as well as yield and composition of the obtained products. A maximum biocrude yield of 27 wt% was reached in the NaOH‐catalyzed runs. A relevant amount of dissolved phenolics were detected in the co‐produced aqueous phase (AP), and removed by liquid–liquid extraction using butyl acetate or diethyl ether, preserving the APR catalyst stability and reaching an hydrogen yield up to 146 mmol H2 L−1 AP. Preliminary mass balances integrating HTL and APR showed that the hydrogen provided by APR may account for up to 46% of the hydrogen amount theoretically required for upgrading the HTL biocrude, thus significantly improving the process performance and sustainability.

Catalytic deoxygenation of carboxyl compounds in the hydrothermal liquefaction crude bio-oil via in-situ hydrogen supply by CuO-CeO2/[formula omitted]-Al2O3 catalyst

Hydrothermal liquefaction (HTL) has drawn great attention as a potential method to produce bio-oil from biomass waste. However, bio-crude from HTL shows undesired high-oxygen content and needs further deoxygenation upgrading. Herein, stearic acids as a model carboxylic compounds in HTL bio-crude was employed to investigate catalytic deoxygenation performance. Results showed that (CuO)10-CeO2/γ-Al2O3 had the most superior catalytic deoxygenation performance for the stearic acids. The maximum stearic acid conversion rate (96.36%) and total hydrocarbon yield (88.79%) were obtained at 300°C, 12h, ratio of stearic acid to water 1:4. The main catalytic deoxygenation pathways were proposed: carbon monoxide generation (decarbonylation) – in-situ hydrogen generation (water–gas shift) – short-chain fatty acid generation (hydrogenolysis) – n-alkanes generation (decarboxylation, hydrodeoxygenation and hydrogenation). DFT calculation elucidated that CuO-CeO2 reduced the activation energy from 24.8kcalmol−1 (vacuum) to 15.0kcalmol−1 (catalytic). Thus, deoxygenation via CuO-CeO2/γ-Al2O3 would be an effective method for upgrading HTL bio-crude.

Sustainable Aviation Fuel from Hydrothermal Liquefaction of Wet Wastes

Hydrothermal liquefaction (HTL) uses heat and pressure to liquefy the organic matter in biomass/waste feedstocks to produce biocrude. When hydrotreated the biocrude is converted into transportation fuels including sustainable aviation fuel (SAF). Further, by liquifying the organic matter in wet wastes such as sewage sludge, manure, and food waste, HTL can prevent landfilling or other disposal methods such as anerobic digestion, or incineration. A significant roadblock to the development of a new route for SAF is the strict approval process, and the large volumes required (>400 L) for testing. Tier α and β testing can predict some of the properties required for ASTM testing with <400 mL samples. The current study is the first to investigate the potential for utilizing wet-waste HTL biocrude (WWHTLB) as an SAF feedstock. Herein, several WWHTLB samples were produced from food waste, sewage sludge, and fats, oils, and grease, and subsequently hydrotreated and distilled to produce SAF samples. The fuels (both undistilled and distilled samples) were analyzed via elemental and 2D-GC-MS. Herein, we report the Tier α and β analysis of an SAF sample derived originally from a WWHTLB. The results of this work indicate that the upgraded WWHTLB material exhibits key fuel properties, including carbon number distribution, distillation profile, surface tension, density, viscosity, heat of combustion, and flash point, which all fall within the required range for aviation fuel. WWHTLB has therefore been shown to be a promising candidate feedstock for the production of SAF.

The Role of Catalysts in Biomass Hydrothermal Liquefaction and Biocrude Upgrading

Hydrothermal liquefaction (HTL) of biomass is establishing itself as one of the leading technologies for the conversion of virtually any type of biomass feedstock into drop-in biofuels and renewable materials. Several catalysis strategies have been proposed for this process to increase the yields of the product (biocrude) and/or to obtain a product with better properties in light of the final use. A number of different studies are available in the literature nowadays, where different catalysts are utilized within HTL including both homogeneous and heterogeneous approaches. Additionally, catalysis plays a major role in the upgrading of HTL biocrude into final products, in which field significant developments have been observed in recent times. This review has the ambition to summarize the different available information to draw an updated overall picture of catalysis applied to HTL. The different catalysis strategies are reviewed, highlighting the specific effect of each kind of catalyst on the yields and properties of the HTL products, by comparing them with the non-catalyzed case. This allows for drawing quantitative conclusions on the actual effectiveness of each catalyst, in relation to the different biomass processed. Additionally, the pros and cons of each different catalysis approach are discussed critically, identifying new challenges and future directions of research.

Blending of Hydrothermal Liquefaction Biocrude with Residual Marine Fuel: An Experimental Assessment

As with all transport modes, the maritime sector is undergoing a drastic transition towards net zero, similar to the path in which Aviation is already engaged through global decarbonization programs such as CORSIA for the International Civil Aviation Organization, or the Emission trading Scheme of the European Union). Maritime indeed shares with Aviation a common element: the difficulty of shifting to electric in the short to medium term. Therefore, the use of sustainable fuels represents the main and only relevant option in this timeframe. As sustainable biofuels will be used as blend components in the case of large-scale deployment, it is necessary to investigate the behavior of bio- and fossil-based fuels when mixed in various percentages, in particular for low quality products such as HTL (HydroThermal Liquefaction) and fast pyrolysis oils from lignocellulosic biomass and waste. Biocrude from subcritical hydrothermal liquefaction of undigested sewage sludge, produced at reaction conditions of 350 °C and 200 bar in a continuous HTL pilot scale unit, was manually mixed at 70 °C with residual marine fuel (low-sulphur type F-RMG-380 per ISO 8217) at two different nominal biocrude shares, respectively 10 wt.% and 20 wt.% in the mixture. While the former blend resulted in the technically complete dissolution of biocrude in the fossil component, the latter sample formed biocrude agglomerates and only partial dissolution of the biocrude aliquot in marine fuel could be achieved (calculated between 14–16 wt.%). The blend with 10 wt.% of SS biocrude in the mixture resulted in compliance with limits of total acid number (TAN), inorganics (in particular vanadium, sodium, silicon and aluminum) and sulphur content, while only the ash content was slightly above the limit.

Upgrading of Hydrothermal Liquefaction Biocrudes from Mono- and Co-Liquefaction of Cow Manure and Wheat Straw Through Hydrotreating and Distillation

Upgrading of Hydrothermal Liquefaction Biocrudes from Mono- and Co-Liquefaction of Cow Manure and Wheat Straw Through Hydrotreating and Distillation

Co-processing bio-liquids with vacuum gasoil through hydrocracking

Hydrocracking converts heavy feeds mainly into middle distillate products. Co-processing these bio-feeds with vacuum gas oil is a possible production route for biofuels. Stabilized bio-liquid from fast pyrolysis and hydrothermal liquefaction bio-crude were mixed with vacuum gas oil (10–20 wt%) and hydrocracked over a bifunctional catalyst. The impact of the bio-liquids on conversion and middle distillate selectivity were investigated. The liquid products were analyzed by several methods such as 2-dimensional gas chromatography coupled with simulated distillation to obtain quantitative distribution of monoaromatics, polyaromatics and saturated hydrocarbons. A quantification study of different types of carbons was performed by 13C NMR and showed the evolution of products. The nature of bio-liquid impacts slightly on the conversion and gas production but not on the selectivity of middle distillates and naphtha. This is explained by a decoupled hydrodeoxygenation and hydrocracking process. This also resulted in a high hydrodesulfurization conversion.

A method for HTL biocrude simulation using multi-objective optimisation and fractional distillation

A novel approach for modelling hydrothermal liquefaction (HTL) biocrude is presented, using a combination of fractional distillation data of biocrude and multi-objective optimisation to simulate the biocrude various properties using the non-dominated sorting genetic algorithm (NSGA-II). The complex composition of biocrude has made it challenging to analyse and simulate in process models. Most HTL simulation studies use a simple basis for biocrude using limited GC–MS data, which may not be reliably accurate. Applying multi-objective optimisation reduced the density and TBP curve error by ten times compared to single-objective optimisation. In addition,the results were further improved by combining distillation experimental data into multi-objective optimisation, in contrast with previous studies which used only the biocrude data. Separating complicated HTL biocrude into five fractions and analysing the obtained results increased the number of candidate databank compounds from 72 to 216, which led to a noticeable improvement in the accuracy of the model.

Biocrude Oil Production by Integrating Microalgae Polyculture and Wastewater Treatment: Novel Proposal on the Use of Deep Water-Depth Polyculture of Mixotrophic Microalgae

Microalgae have attracted significant attention worldwide as one of the most promising feedstock fossil fuel alternatives. However, there are a few challenges for algal fuels to compete with fossil fuels that need to be addressed. Therefore, this study reviews the R&D status of microalgae-based polyculture and biocrude oil production, along with wastewater treatment. Mixotrophic algae are free to some extent from light restrictions using organic matter and have the ability to grow well even in deep water-depth cultivation. It is proposed that integrating the mixotrophic microalgae polyculture and wastewater treatment process is the most promising and harmonizing means to simultaneously increase capacities of microalgae biomass production and wastewater treatment with a low land footprint and high robustness to perturbations. A large amount of mixotrophic algae biomass is harvested, concentrated, and dewatered by combining highly efficient sedimentation through flocculation and energy efficient filtration, which reduce the carbon footprint for algae fuel production and coincide with the subsequent hydrothermal liquefaction (HTL) conversion. HTL products are obtained with a relatively low carbon footprint and separated into biocrude oil, solid, aqueous, and gas fractions. Algae biomass feedstock-based HTL conversion has a high biocrude oil yield and quality available for existing oil refineries; it also has a bioavailability of the recycled nitrogen and phosphorus from the aqueous phase of algae community HTL. The HTL biocrude oil represents higher sustainability than conventional liquid fuels and other biofuels for the combination of greenhouse gas (GHG) and energy return on investment (EROI). Deep water-depth polyculture of mixotrophic microalgae using sewage has a high potential to produce sustainable biocrude oil within the land area of existing sewage treatment plants in Japan to fulfill imported crude oil.

Production of upgraded biocrude from hydrothermal liquefaction using clays as in situ catalysts

Hydrothermal liquefaction (HTL) is a thermochemical process that converts biomass into biocrude. HTL suffers from low yields of water-insoluble biocrude with high oxygen contents and low heating values. Inexpensive clay minerals including montmorillonite, dolomite, kaolinite and sand were used to upgrade HTL biocrude as in situ acid-base catalysts. Batch tests were performed using starch with 5 wt% clay minerals at 300 °C for 1 h. Bio-oil was fractionated into water-soluble and water-insoluble parts to explore potential catalytic mechanisms by analyzing the fractional distribution, elemental composition and chemical composition. Higher carbon recoveries in the bio-oil fraction (approaching 60%) occurred with clay-catalyzed HTL. Energy recovery of both bio-oil fractions increased by approximately 22% for all clays. A base-catalyzed pathway inhibits char formation from catalytic HTL, with dolomite approaching a char yield as low as 3%. Chromatographic analysis of heavy and light oils from both fractions showed that dolomite and montmorillonite play a catalytic effect via base and acid pathways on upgrading biocrude. Clay-catalyzed HTL modified the boiling point distributions by producing more 100–300 °C middle temperature distillates. Overall, catalytic HTL with clay minerals enhanced the heating value and energy recovery of bio-oils.

Extended Catalyst Lifetime Testing for HTL Biocrude Hydrotreating to Produce Fuel Blendstocks from Wet Wastes

This paper reports on the catalyst stability of the hydrotreatment of HTL (Hydrothermal Liquefaction) biocrudes to produce finished liquid transportation fuel blendstocks. We report the stable hydrotreating of HTL biocrude derived from sewage sludge and food waste over industrially relevant hydrotreating CoMo and NiMo catalysts at relevant catalyst activities. The use of wet-waste-derived HTL biocrudes derived from both food waste and sewage sludge in the hydrotreater campaign strengthens the case that HTL biocrudes derived from a variety of wet-waste feedstocks can be upgraded without significant catalyst instability over industrially relevant hydrotreater time-periods. Stable hydrotreating performance was obtained with each feedstock. The overall yield was approximately 85% with all HTL biocrudes. Over 1500 h of steady-state operation, minimal deactivation was observed. These results indicate that a hydrotreatment process to upgrade can be stable for industrially relevant times, a critical roadblock to derisking commercialization. The upgraded product produces a diesel-rich (∼70% in the 150–350 °C range) fuel blendstock, with high cetane due to the high fraction of alkanes. Further, we report the impact of process levers on hydrotreating performance on a fully broken-in catalyst (following 1500 h of steady-state operation). The long-term catalyst stability presented here is an important demonstration to derisk HTL commercialization.

Study of Biocrudes Obtained via Hydrothermal Liquefaction (HTL) of Wild Alga Consortium under Different Conditions

Microalga-based fuels are promising solutions for replacing fossil fuels. This feedstock presents several advantages such as fast growth in a harsh environment and an ability to trap gases emitted from industries, thus reducing global warming effects. An efficient way to convert harvested microalgae into biofuels is hydrothermal liquefaction (HTL), which yields an intermediate product called biocrude. In this study, the elemental and molecular compositions of 15 different HTL biocrudes were determined by means of different techniques. Wild algae were cultivated in an industrial environment with plant emissions as a carbon source in fresh or seawater. It was notably observed that the culture medium had an influence on the biochemical composition and mineral matter content of algae. Thus, seawater algae were characterized by larger amounts of carbohydrates and mineral matter than freshwater ones, which also affected the oil yields and the light and heavy fractions of biocrudes.

Biocrude Production via Non-Catalytic Supercritical Hydrothermal Liquefaction of Fucus vesiculosus Seaweed Processing Residues

The potential of using cold water brown macroalgae Fucus vesiculosus for biocrude production via non-catalytic supercritical hydrothermal liquefaction (HTL) was studied. Demineralization, residue neutralization, and high value-added product (alginate and fucoidan) extraction processes were carried out before using the biomass for HTL biocrude production. Acid leaching was carried out using three demineralization agents: distilled water, dilute citric acid solution, and the diluted acidic aqueous by-product from a continuous HTL pilot facility. Alginate was extracted via H2SO4 and NaCO3 bathing, and fucoidan was extracted using CaCl2. Experimental data show that none of the leaching agents was greatly efficient in removing inorganics, with citric acid leaching with extensive neutralization reaching the highest ash removal efficiency of 47%. The produced 6 sets of biocrudes were characterized by elemental and thermogravimetric analyses. Short (10-min retention) HTL and the extent of leaching residue neutralization were also investigated. Highest biocrude yields were recorded when liquefying non-neutralized citric acid leaching, alginate, and fucoidan extraction residues. On the other hand, thermochemical conversions of short retention time HTL, full neutralization extent, and baseline (dried raw macroalgae) biomass performed worse. Specifically, the highest biocrude yield of 28.2 ± 2.5 wt.% on dry ash-free feedstock basis was recorded when liquefying alginate extraction residues. Moreover, the highest energy recovery of 52.8% was recorded when converting fucoidan extraction residues.

Demineralization of Miscanthus Biocrude Obtained from Catalytic Hydrothermal Liquefaction: Conditioning through Acid Washing

In this contribution, we successfully applied demineralization (i.e., solvent-assisted separation and acid washing) for the removal of carbonaceous solids and inorganics from a biocrude obtained from the catalytic hydrothermal liquefaction (HTL) of Miscanthus. The experimental results of all six employed acids showed that 0.1 M H2SO4 was the most effective and significantly reduced metallic (Fe by 93.9%, <15 µg/g and Mg by 95.6%, 2.1 µg/g) and ash content (by 92.7% to 337 µg/g) from the already filtered biocrude. The utilized demineralizing agents caused a loss of nitrogen and of organic carbon (1% total organic carbon (TOC) and 0.058% total nitrogen (TN) in 0.1 M H2SO4). Gas chromatography-mass spectrometry (GC–MS) results clarified the nature of this loss, showing that 54% of ketones and 39% of alcohols were removed when 0.1 M H2SO4 was employed. Furthermore, FT-IR spectra remained the same before and after acid washing without affecting any functional groups. This work therefore proposes demineralization as a viable route for the removal of high inorganic content from lignocellulosic HTL biocrudes.