Catalytic hydrothermal liquefaction of water hyacinth

Waste animal fat with hydrothermal liquefaction as a potential route to marine biofuels

Unused animal waste rendered fat is a potential feedstock for marine biofuels. In this work, bio-oil was generated using hydrothermal liquefaction (HTL) of nitrogen-free and low sulfur rendered bovine fat. Maximum bio-oil yield of 28 ± 1.5% and high heating value of 38.5 ± 0.16 MJ·kg‒1 was obtained at 330 °C at 50% animal fat solid load and 20 min retention time. The nitrogen and sulfur content were negligible, making the produced bio-oil useful marine biofuel, taking into account current stringent regulations on NOx and SOx emissions. The economic analysis of the process, where part of the bovine fat waste is converted to the bio-oil and the semi-solid residues can be used to supply the heat demand of the HTL process and alternately generate electricity, showed that our process is likely to generate a positive profit margin on a large scale. We also showed the growing economic importance of electricity in the revenues as commercial production becomes more energy efficient.

Hydrothermal Liquefaction: How the Holistic Approach by Nature Will Help Solve the Environmental Conundrum

Hydrothermal liquefaction (HTL) represents a beacon of scientific innovation, which unlocks nature's alchemical wonders while reshaping the waste-to-energy platform. This transformative technology offers sustainable solutions for converting a variety of waste materials to valuable energy products and chemicals-thus addressing environmental concerns, inefficiencies, and high costs associated with conventional waste-management practices. By operating under high temperature and pressure conditions, HTL efficiently reduces waste volume, mitigates harmful pollutant release, and extracts valuable energy from organic waste materials. This comprehensive review delves into the intricacies of the HTL process and explores its applications. Key process parameters, diverse feedstocks, various reactor designs, and recent advancements in HTL technology are thoroughly discussed. Diverse applications of HTL products are examined, and their economic viability toward integration in the market is assessed. Knowledge gaps and opportunities for further exploration are accordingly identified, with a focus on optimizing and scaling up the HTL process for commercial applications. In conclusion, HTL holds great promise as a sustainable technology for waste management, chemical synthesis, and energy production, thus making a significant contribution to a more sustainable future. Its potential to foster a circular economy and its versatility in producing valuable products underscore its transformative role in shaping a more sustainable world.

Effect of thermal and NaOH pretreatment on water hyacinth to enhance the biogas production

Water hyacinth (WH) is used as the substrate for biogas production due to its high lignocellulosic composition and natural abundance. The present study used thermal and chemical (alkali) pretreatment techniques to enhance biogas production from water hyacinth used as a substrate by anaerobic digestion. Thermal pretreatment was done using an autoclave at 121 °C and 15 lb (2 bar) pressure and alkali pretreatment by NaOH at two concentrations (2% and 5% w/v). The inoculum:substrate ratio for biogas production was 2:1, where cow dung was used as inoculum. Results indicated that the pretreatments increased biomass degradability and improved biogas production. Water hyacinth pretreated with 5% NaOH produced the highest amount of biogas (142.61 L/Kg VS) with a maximum methane content of 64.59%. The present study found that alkali pretreatment can modify the chemical structure and enhance WH hydrolysis, leading to enhanced energy production.

An integrated biorefinery approach for the valorization of water hyacinth towards circular bioeconomy: a review

Water hyacinth (WH) has become a considerable concern for people across the globe due to its environmental and socio-economic hazards. Researchers are still trying to control this aquatic weed effectively without other environmental or economic losses. Research on WH focuses on converting this omnipresent excessive biomass into value-added products. The potential use of WH for phytoremediation and utilizing waste biomass in various industries, including agriculture, pharmaceuticals, and bioenergy, has piqued interest. The use of waste WH biomass as a feedstock for producing bioenergy and value-added chemicals has emerged as an eco-friendly step towards the circular economy concept. Here, we have discussed the extraction of bio-actives and cellulose as primary bioproducts, followed by a detailed discussion on different biomass conversion routes to obtain secondary bioproducts. The suggested multi-objective approach will lead to cost-effective and efficient utilization of waste WH biomass. Additionally, the present review includes a discussion of the SWOT analysis for WH biomass and the scope for future studies. An integrated biorefinery scheme is proposed for the holistic utilization of this feedstock in a cascading manner to promote the sustainable and zero-waste circular bio-economy concept.

Phenol Liquefaction of Waste Sawdust Pretreated by Sodium Hydroxide: Optimization of Parameters Using Response Surface Methodology

In this study, a two-step method was used to realize the liquefaction of waste sawdust under atmospheric pressure, and to achieve a high liquefaction rate. Specifically, waste sawdust was pretreated with NaOH, followed by liquefaction using phenol. The relative optimum condition for alkali-heat pretreatment was a 1:1 mass ratio of NaOH to sawdust at 140 °C. The reaction parameters including the mass ratio of phenol to pretreated sawdust, liquefaction temperature, and liquefaction time were optimized by response surface methodology. The optimal conditions for phenol liquefaction of pretreated sawdust were a 4.21 mass ratio of phenol to sawdust, a liquefaction temperature of 173.58 °C, and a liquefaction time of 2.24 h, resulting in corresponding liquefied residues of 6.35%. The liquefaction rate reached 93.65%. Finally, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) were used to analyze untreated waste sawdust, pretreated sawdust, liquefied residues, and liquefied liquid. SEM results showed that the alkali-heat pretreatment and liquefaction reactions destroyed the intact, dense, and homogeneous sample structures. FT-IR results showed that liquefied residues contain aromatic compounds with different substituents, including mainly lignin and its derivatives, while the liquefied liquid contains a large number of aromatic phenolic compounds. XRD showed that alkali-heat pretreatment and phenol liquefaction destroyed most of the crystalline regions, greatly reduced the crystallinity and changed the crystal type of cellulose in the sawdust.

A polymeric Brønsted acid ionic liquid mediated liquefaction of municipal solid waste

The rapid industrialization and population explosion continuously generate massive amounts of municipal waste. Several conventional processes are in practice for the treatment of municipal waste, but the requirement of stringent operating conditions, incomplete conversion, longer processing time and emission of toxic gases, etc., are the major associated barriers. Thus, there is an urgent requirement for a sustainable, environmentally feasible process that can process waste into energy and fuel products. In the present manuscript, polyethylenimine functionalized polymeric Bronsted acid ionic liquid (PolyE-IL) catalysts have been explored for the Catalytic Thermo Liquefaction (CTL) of organic biodegradable municipal solid waste (MSW). A series of PolyE-IL catalysts with variable counter ions were examined for CTL of MSW. Of all the tested PolyE-IL catalysts, the integration of [PEI]⁺[HSO₄]^- gave excellent MSW conversion (>85%) and yield (>80%) of liquefied products (CTL-Oil) under non-stringent reaction conditions and without any formation char and gases. The influence of reaction conditions such as catalyst concentration, reaction temperature, time, slurry concentration, and type of feedstock of conversion and yield are studied. The column adsorption and membrane separation process was integrated to facilitate the catalyst and CTL-Oil separation. A series of commercially available hydrophobic resins were tested to separate catalyst and CTL-Oil. ICT005 showed the highest adsorption efficiency of all tested resins with 35.46 mg/mL of binding capacity and K_d of 0.02159. The physicochemical properties of CTL-Oil were studied in detail by using various analytical tools, which exhibited that CTL-Oil comprises a mixture of small and large molecular weight organic compounds and has a calorific value of 4000 kcal/kg; hence it could be used for further energy and fuel applications. Thus, the reported CTL process can be beneficial to resolve both environmental and fossil fuel dependency issues simultaneously by converting MSW into CTL-Oil.

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.

Progress in thermochemical conversion of aquatic weeds in shellfish aquaculture for biofuel generation: Technical and economic perspectives

Rapid growth of aquatic weeds in treatment pond poses undesirable challenge to shellfish aquaculture, requiring the farmers to dispose these weeds on a regular basis. This article reviews the potential and application of various aquatic weeds for generation of biofuels using recent thermochemical technologies (torrefaction, hydrothermal carbonization/liquefaction, pyrolysis, gasification). The influence of key operational parameters for optimising the aquatic weed conversion efficiency was discussed, including the advantages, drawbacks and techno-economic aspects of the thermochemical technologies, and their viability for large-scale application. Via extensive study in small and large scale operation, and the economic benefits derived, pyrolysis is identified as a promising thermochemical technology for aquatic weed conversion. The perspectives, challenges and future directions in thermochemical conversion of aquatic weeds to biofuels were also reviewed. This review provides useful information to promote circular economy by integrating shellfish aquaculture with thermochemical biorefinery of aquatic weeds rather than disposing them in landfills.

Wet organic waste treatment via hydrothermal processing: A critical review

There are several recent reviews published in the literature on hydrothermal carbonization, liquefaction and supercritical water gasification of lignocellulosic biomass and algae. The potential of hydrochar, bio-oil or synthesis gas production and applications have also been reviewed individually. The comprehensive review on the hydrothermal treatment of wet wastes (such as municipal solid waste, food waste, sewage sludge, algae) covering carbonization, liquefaction and supercritical water gasification, however, is missing in the literature which formed the basis of the current review paper. The current paper critically reviews the literature around the full spectrum of hydrothermal treatment for wet wastes and establishes a good comparison of the different hydrothermal treatment options for managing wet waste streams. Also, the role of catalysts as well as synthesis of catalysts using hydrothermal treatment of biomass has been critically reviewed. For the first time, efforts have also been made to summarize findings on modelling works as well as techno-economic assessments in the area of hydrothermal treatments of wet wastes. The study concludes with key findings, knowledge gaps and future recommendations to improve the productivity of hydrothermal treatment of wet wastes, helping improve the commercial viability and environmental sustainability.

The study of hydrothermal liquefaction of corn straw with Nano ferrite + inorganic base catalyst system at low temperature

Hydrothermal liquefaction of corn straw with different catalytic systems and temperatures were investigated in this study. Results showed dual catalytic system can effectively promote the degradation of corn straw at low temperature. With increase of temperature, aqueous phase increased and straw residue decreased for all catalytic systems. The heavy bio-oil yield increased with the increasing of temperature for single catalytic system, while the trend was opposite for dual catalytic system. In single catalytic system, ZnFe₂O₄ was more suitable for preparation of heavy bio-oil, and the maximum yield reached 34.02 wt% at 180 °C. The proportion of monophenyl compounds in heavy bio-oil for dual catalytic system reached the maximum of 84% at 220 °C with ZnFe₂O₄. At 180 °C, the contents of Benzofuran,2,3-dihydro and 2-Methoxy-4-vinylphenol reached the maximum of 31.42% and 17.64% in CoFe₂O₄ catalyst system, and the maximum yield of Vanillin was 10.82% with ZnFe₂O₄.

State of the Art Research on Sustainable Use of Water Hyacinth: A Bibliometric and Text Mining Analysis

This study aims to present a systematic data-driven bibliometric analysis of the water hyacinth (Eichhornia crassipes) infestation problem around the globe. As many solutions are being proposed in academia for its management, mitigation, and utilization, it requires investigation through a systematic scrutinizing lens. In this study, literature records from 1977 to June 2020 concerning research on water hyacinth are taken from Scopus for text analysis. Trends in the publication of different article types, dynamics of publication, clustering, correlation, and co-authoring patterns between different countries are observed. The cluster analysis indicated four clusters viz. (i) ecological works related to species, (ii) pollutant removal process and methods, (iii) utilization of biofuels for biogas production, and (iv) modelling works. It is clear from the networking analysis that most of the publications regarding water hyacinth are from India, followed by China and the United States. Sentiment analysis with the AFINN lexicon showed that the negative sentiment towards the aquatic weed has intensified over time. An exploratory analysis was performed using a bigram network plot, depicting and outlining different important domains of water hyacinth research. Water hyacinth research has passed the pioneering phase and is now at the end of a steady growth phase or at the beginning of an acceleration phase. In this article, an overview is given for the entirety of water hyacinth research, with an indication of future trends and possibilities.

Water hyacinth for energy and environmental applications: A review

This review is focused on the sustainable management of harvested water hyacinth (WH) via thermochemical conversion to carbonaceous materials (CMs), biofuels, and chemicals for energy and environmental applications. One of the major challenges in thermochemical conversion is to guarantee the phytoremediation performance of biochar and the energy conversion efficiency in biowaste-to-energy processes. Thus, a circular sustainable approach is proposed to improve the biochar and energy production. The co-conversion process can enhance the syngas, heat, and energy productions with high-quality products. The produced biochar should be economically feasible and comparable to available commercial carbon products. The removal and control of heavy and transition metals are essential for the safe implementation and management of WH biochar. CMs derived from biochar are of interest in wastewater treatment, air purification, and construction. It is important to control the size, shape, and chemical compositions of the CM particles for higher-value products like catalyst, adsorbent or conductor.

Technical insights into the production of green fuel from CO2 sequestered algal biomass: A conceptual review on green energy

Algae a promising energy reserve due to its adaptability, cheap source, sustainability and it's growth ability in wastewater with efficient sequestration of industrial carbon dioxide. This review summarizes the pathways available for biofuel production from carbon sequestered algae biomass. In this regard, this review focuses on microalgae and its cultivation in wastewater with CO₂ sequestration. Conversion of carbon sequestered biomass into bio-fuels via thermo-chemical routes and its engine emission properties. Energy perspective of green gaseous biofuels in near future. This review revealed that algae was the pre-dominant CO₂ sequester than terrestrial plants in an eco-friendly and economical way with simultaneous wastewater remediation. Hydrothermal liquefaction of algae biomass was the most preferred mode for biofuel generation than pyrolysis due to high moisture content. The algae based fuels exhibit less greenhouse gases emission and higher energy value. This review helps the researchers, environmentalists and industrialists to evaluate the impact of algae based bio-energy towards green energy and environment.

Research progress and hot spots of hydrothermal liquefaction for bio-oil production based on bibliometric analysis

Hydrothermal liquefaction (HTL) of biomass used HTL reaction under high temperature and pressure to produce bio-oil. This technology is considered as one of the most promising converting technology of biomass to biofuels. This paper summarized current research developments of HTL for bio-oil and analyzed its reaction mechanism and influencing factors based on bibliometric analysis. The results showed that reaction conditions and catalyst have been still global researching focuses about HTL. Compared with homogeneous catalysts, the study of HTL by using heterogeneous catalyst developed more quickly. With promotion of resource recovering, food waste, sludge, and other organic waste can also be used as raw materials for HTL for bio-oil now. The structure of this paper was shown in graphic abstract. Firstly, bibliometric analysis was conducted on hydrothermal liquefaction for bio-oil production. According to the emergency frequency of key words, catalyst, microalgae, reaction conditions, and biomass waste as raw material for hydrothermal liquefaction were determined as four parts of the paper. Finally, we speculated the development trend of hydrothermal liquefaction for bio-oil production.

Effects of reaction conditions on products and elements distribution via hydrothermal liquefaction of duckweed for wastewater treatment

Wastewater treatment by duckweed is a naturally sustainable technology. However, its development is limited due to the lack of a follow-up treatment of duckweed. The duckweed was proposed for the treatment of rural domestic wastewater and agricultural wastewater, and it was further processed to produce bio-oil via hydrothermal liquefaction at various temperatures (250 °C-370 °C) and residence times (15-60 min). The highest bio-oil yield of 35.6 wt% was obtained at 370 °C, 45 min. The higher heating value of bio-oil was 40.85 MJ/kg, and the H/C ratio (1.72-1.98) was similar to that of petroleum (1.84). The gas chromatography-mass spectrometry analysis results revealed that the bio-oil mainly consisted of N-heterocycles, cyclic ketones, esters, amides, long-chain hydrocarbons, phenols, and aromatic intermediates. Valuable compounds (3-pyridinol, 2-pyrrolidinone, and its analogues) of high concentration were identified in the water-soluble organic matter. Compared with other materials, this study produced higher-quality bio-oil and water-soluble organic matter.

Hydrothermal liquefaction of Fe-impregnated water hyacinth for generation of liquid bio-fuels and nano Fe carbon hybrids

In this work, hydrothermal liquefaction experiments of iron impregnated water hyacinth were performed with a motive to enhance bio-oil yields along with generation of nanometal carbon hybrids. Iron nanoparticles were impregnated and its metal loading was determined by ICP-MS. The impact of operating parameters like temperature, biomass to water ratio and reaction time on bio-oil yields was studied. During hydrothermal liquefaction a maximum total bio-oil yield of 38.1% was obtained at 280 °C along with formation of nanometal carbon hybrids. The light oil and heavy oil fractions were characterized by GCMS and NMR for determining the key components. The light oil mainly comprises of alkanes, alcohols and esters whereas heavy oil contains esters, ethers, carboxylic acids and phenols. XRD and XPS of Fe-impregnated water hyacinth and residues confirmed the transition of Fe^+3/+2 to Fe⁰. TEM analysis resulted an average particle size of Fe nanoparticles around 19.6 nm.

Comparison of catalytic effect on upgrading bio-oil derived from co-pyrolysis of water hyacinth and scrap tire over multilamellar MFI nanosheets and HZSM-5

Catalytic co-pyrolysis of water hyacinth and scrap tire experiments were performed to evaluate the feasibility of improving the monocyclic aromatic hydrocarbons production. The production of monocyclic aromatic hydrocarbons increased from 5.31% (sole pyrolysis of water hyacinth) to 13.11% (co-pyrolysis with scrap tire). With use of zeolites, the highest production of monocyclic aromatic hydrocarbons can reach up to 69.18%. Comprehensive comparison on catalytic effects of HZSM-5 and multilamellar MFI nanosheets were provided. With the material to multilamellar MFI nanosheets ratios changes from 2:1 to 1:4, the production of monocyclic aromatic hydrocarbons increases significantly from 37.15-69.18%. The average production of monocyclic aromatic hydrocarbons produced by using multilamellar MFI nanosheets were 12.07% higher than that using HZSM-5, indicating the better performance of multilamellar MFI nanosheets in producing monocyclic aromatic hydrocarbons. This work provided a reference for the reuse of water hyacinth and scrap tire over multilamellar MFI nanosheets in energy field.

Review on sustainable production of biochar through hydrothermal liquefaction: Physico-chemical properties and applications

This review examines in detail the production and characteristics of biochar resulting from hydrothermal liquefaction. Specifically, the impact of feedstocks and different process parameters on the properties and yield of biochar by hydrothermal liquefaction has been thoroughly studied. Hydrothermal liquefaction derived biochars, relative to biochars from high-temperature thermochemical processes retain critical functional groups during carbonization and are therefore promising for a wide range of applications. Most of the review's efforts are to study possible hydrothermal liquefaction biochar applications in various fields, including fuel, metal and dye adsorption, pollutant reduction, animal feed, and biogas catalyst. The feasibility of biochar through the hydrothermal liquefaction process has been analysed via life-cycle assessment and energy evaluation. The article concludes with a brief discussion on possible issues and strategies for the sustainable development of hydrothermal liquefaction-based biochar.

Optimization of process parameters for hydrothermal conversion of castor residue

Castor plant (Ricinus communis) is a fast-growing shrub from Euphorbiaceae family. India ranks first in the world for the production of castor seeds. The generation of residue from its leaves and stems is more than 50% of the whole plant. This research work involves the estimation of the optimum condition for the production/value addition by hydrothermal liquefaction of castor residue using factorial design. Temperature (T) and residence time (RT) are the key parameters that affect the bio-oil yield. A 3² full factorial design was employed to understand the affects the bio-oil yield and conversion with key parameters. The key parameter and its interaction effects were analyzed by analysis of variance (ANOVA); F-test and p-values were used to rank the process variable affecting the total bio-oil yield. It was observed that the temperature imparts significant effect on total bio-oil yield. The optimum conditions to obtain maximum total bio-oil yield are T = 300 °C and RT = 60 min. The statistical model was best fitted with high coefficient of determination (R²) of 0.9994 and 0.9473 for total bio-oil yield and conversion respectively.

Synergistic hydrothermal liquefaction of wheat stalk with homogeneous and heterogeneous catalyst at low temperature

The effect of Na₂CO₃, Fe and Na₂CO₃ + Fe during hydrothermal liquefaction (HTL) of wheat stalk with different temperature and reaction time was investigated in this study. The results indicated that Na₂CO₃ + Fe can promote the cracking of wheat stalk compared with Na₂CO₃ or Fe. Meanwhile, higher temperature favored the decomposition of wheat stalk and formation of heavy bio-oil. The highest heavy bio-oil yield was 24.25 wt% and the maximum liquefaction conversion rate was 89.45 wt% in system of Na₂CO₃ + Fe at 270 °C. The analysis results indicated that longer reaction time could promote liquefaction conversion especially for heavy bio-oil with Na₂CO₃ + Fe during the process of HTL. GC-MS, UPLC-MS and FT-IR analysis indicated that the major organic compounds in heavy bio-oil were aromatic compounds, alcohols, ketones, alkanes, and aldehydes, among of them aromatic compounds were the most prevalent.

An overview of the recent trends on the waste valorization techniques for food wastes

A critical and up-to-date review has been conducted on the latest individual valorization technologies aimed at the generation of value-added by-products from food wastes in the form of bio-fuels, bio-materials, value added components and bio-based adsorbents. The aim is to examine the associated advantages and drawbacks of each technique separately along with the assessment of process parameters affecting the efficiency of the generation of the bio-based products. Challenges faced during the processing of the wastes to each of the bio-products have been explained and future scopes stated. Among the many hurdles encountered in the successful and high yield generation of the bio-products is the complexity and variability in the composition of the food wastes along with the high inherent moisture content. Also, individual technologies have their own process configurations and operating parameters which may affect the yield and composition of the desired end product. All these require extensive study of the composition of the food wastes followed by their effective pre-treatments, judicial selection of the technological parameters and finally optimization of not only the process configurations but also in relation to the input food waste material. Attempt has also been made to address the hurdles faced during the implementation of such technologies on an industrial scale.

Enhancing bioethanol production from water hyacinth by new combined pretreatment methods

This study investigated the possibility of enhancing bioethanol production by combined pretreatment methods for water hyacinth. Three different kinds of pretreatment methods, including microbial pretreatment, microbial combined dilute acid pretreatment, and microbial combined dilute alkaline pretreatment, were investigated for water hyacinth degradation. The results showed that microbial combined dilute acid pretreatment is the most effective method, resulting in the highest cellulose content (39.4 ± 2.8%) and reducing sugars production (430.66 mg·g^-1). Scanning Electron Microscopy and Fourier Transform Infrared Spectrometer analysis indicated that the basic tissue of water hyacinth was significantly destroyed. Compared to the other previously reported pretreatment methods for water hyacinth, which did not append additional cellulase and microbes for hydrolysis process, the microbial combined dilute acid pretreatment of our research could achieve the highest reducing sugars. Moreover, the production of bioethanol could achieve 1.40 g·L^-1 after fermentation, which could provide an extremely promising way for utilization of water hyacinth.

Aquatic weeds as the next generation feedstock for sustainable bioenergy production

Increasing oil prices and depletion of existing fossil fuel reserves, combined with the continuous rise in greenhouse gas emissions, have fostered the need to explore and develop new renewable bioenergy feedstocks that do not require arable land and freshwater resources. In this regard, prolific biomass growth of invasive aquatic weeds in wastewater has gained much attention in recent years in utilizing them as a potential feedstock for bioenergy production. Aquatic weeds have an exceptionally higher reproduction rates and are rich in cellulose and hemicellulose with a very low lignin content that makes them an efficient next generation biofuel crop. Considering their potential as an effective phytoremediators, this review presents a model of integrated aquatic biomass production, phytoremediation and bioenergy generation to reduce the land, fresh water and fertilizer usage for sustainable and economical bioenergy.

Liquid fuel generation from algal biomass via a two-step process: effect of feedstocks

BACKGROUND

In this study, a two-step processing method (hydrothermal liquefaction followed by catalytic upgrading) was used to produce upgraded bio-oil. A comprehensive screening analysis of algal species, including four microalgae and four macroalgae, was conducted to bridge the gap between previous accounts of microalgae and macroalgae hydrothermal liquefaction and the upgrading process of the resulting crude bio-oils.

RESULTS

Hydrothermal liquefaction using eight algal biomasses was performed at 350 °C for 1 h. The microalgae always produced a higher crude bio-oil yield than the macroalgae due to their high lipid content, among which Schizochytrium limacinum provided the maximum crude bio-oil yield of 54.42 wt%. For microalgae, higher amounts of N in the biomass resulted in higher amounts of N in the crude bio-oil; however, contrary results were observed for the macroalgae. The crude bio-oils generated from both the microalgae and macroalgae were characterized as having a high viscosity, total acid number, and heteroatom content, and they were influenced by the biochemical compositions of the feedstocks. Next, all eight-crude bio-oils were treated at 400 °C for 2 h with 10 wt% Ru/C using tetralin as the hydrogen donor. The hydrogen source was provided after tetralin was transformed to naphthalene. All the upgraded bio-oils had higher energy densities and significantly lower N, O, and S contents and viscosities than their corresponding crude bio-oils. However, the H/C molar ratio of the upgraded bio-oils decreased due to the absence of external hydrogen relative to the crude bio-oils. The S content of the upgraded bio-oil produced from upgrading the Schizochytrium limacinum crude bio-oil was even close to the 50 ppm requirement of China IV diesel.

CONCLUSIONS

Microalgae are better feedstocks than macroalgae for liquid fuel production. Biochemical components have a significant impact on the yield and composition of crude bio-oil. Tetralin does not perform as well as external hydrogen for controlling coke formation. The S content of the upgraded bio-oil can be reduced to 76 ppm for the crude bio-oil produced from Schizochytrium limacinum. Upgraded bio-oils have similar properties to those of naphtha and jet fuel.

The effect of hydrophilic amines on hydrothermal liquefaction of macroalgae residue

Hydrothermal liquefaction (HTL) of macroalgae residue was accomplished with seven kinds of amine catalysts for chemical and bio-oil production. The effect of HTL conditions on product distribution was investigated, and results showed that both temperature and amines concentration have significant effects on conversion of macroalgae residue to liquid products and bio-oil. The effect of different amines on composition of liquid products and bio-oil was also studied. The main ingredient of liquid products were organic acids, and the yield of organic acids declined with the increase of alkyl chain in amines. The yield of bio-oil increased with the addition of alkyl chain for primary amines and tertiary amines, while decreased for secondary amines. Methylamine had the highest yield of liquid products of 79.09wt%, and the highest bio-oil yield of 24.37wt% was obtained in the presence of triethylamine.

Effects of temperature and solvent on hydrothermal liquefaction of Sargassum tenerrimum algae

The influence of various solvents (H2O, CH3OH, and C2H5OH) on product distribution and nature of products during hydrothermal liquefaction of sargassum tenerrimum algae has been examined. Hydrothermal liquefaction was performed using H2O (260, 280 and 300°C) and organic solvents CH3OH and C2H5OH (280°C) for 15min. The use of organic solvents significantly increased the yield of bio-oil. In the case of liquefaction with CH3OH and C2H5OH, the bio-oil yield was 22.8 and 23.8wt.% respectively whereas the bio-oil yield was 16.33wt.% with H2O. GC-MS analysis of the liquid products indicated the presence of various organic compounds including aromatics, nitrogenated and oxygenated compounds and higher selectivity amount of ester compounds were observed in the presence of alcoholic solvents. NMR and FT-IR showed that present of solvents have an effect on the decomposition of sargassum tenerrimum algae.

Pyrolysis of azolla, sargassum tenerrimum and water hyacinth for production of bio-oil

Pyrolysis of azolla, sargassum tenerrimum and water hyacinth were carried out in a fixed-bed reactor at different temperatures in the range of 300-450°C in the presence of nitrogen (inert atmosphere). The objective of this study is to understand the effect of compositional changes of various aquatic biomass samples on product distribution and nature of products during slow pyrolysis. The maximum liquid product yield of azolla, sargassum tenerrimum and water hyacinth (38.5, 43.4 and 24.6wt.% respectively) obtained at 400, 450 and 400°C. Detailed analysis of the bio-oil and bio-char was investigated using 1H NMR, FT-IR, and XRD. The characterization of bio-oil showed a high percentage of aliphatic functional groups and presence of phenolic, ketones and nitrogen-containing group. The characterization results showed that the bio-oil obtained from azolla, sargassum tenerrimum and water hyacinth can be potentially valuable as a fuel and chemicals.

Water hyacinth a potential source for value addition: An overview

Water hyacinth a fresh water aquatic plant is considered as a noxious weed in many parts of the world since it grows very fast and depletes nutrients and oxygen from water bodies adversely affecting the growth of both plants and animals. Hence conversion of this problematic weed to value added chemicals and fuels helps in the self-sustainability especially for developing countries. The present review discusses the various value added products and fuels which can be produced from water hyacinth, the recent research and developmental activities on the bioconversion of water hyacinth for the production of fuels and value added products as well as its possibilities and challenges in commercialization.

Conversion of Undaria pinnatifida residue to glycolic acid with recyclable methylamine in low temperature hydrothermal liquefaction

The conversion of Undaria pinnatifida residue to glycolic acid was carried out using methylamine as catalyst by hydrothermal method at relatively low temperature. GC-MS and HPLC were used to identify the composition of bio-oil and liquid products which provide the knowledge of the chemical reaction pathways of the hydrothermal liquefaction. The main liquid product was organic acid which contained glycolic acid, lactic acid, formic acid and acetic acid. And the major organic acid was glycolic acid with the highest yield of 46.52% or 33.98% of dry biomass. Methylamine promoted the dissolution of cellulose from Undaria pinnatifida residue, and significantly improved the yield of glycolic acid. The mechanism of HTL was investigated and the results show that the carbocation C3 was attacked by methylamine molecule which led to the high yield of glycolic acid. In addition, the recovery of methylamine was studied and the highest recovery rate reached 99.28%.

Analysis of utilization technologies for Eichhornia crassipes biomass harvested after restoration of wastewater

Eichhornia crassipes (EC, water hyacinth) has gained attention due to its alarming reproductive capacity, which subsequently leads to serious ecological damage of water in many eutrophic lakes in the world. The traditional mechanical removal methods have disadvantages. They squander this valuable lignocellulosic resource. Meanwhile, there is a bottleneck for the subsequently reasonable and efficient utilization of EC biomass on a large scale after phytoremediation of polluted water using EC. As a result, the exploration of effective EC utilization technologies has become a popular research field. After years of exploration and amelioration, there have been significant breakthroughs in this research area, including the synthesis of excellent EC cellulose-derived materials, innovative bioenergy production, etc. This review organizes the research of the utilization of the EC biomass among several important fields and then analyses the advantages and disadvantages for each pathway. Finally, comprehensive EC utilization technologies are proposed as a reference.

Fast liquefaction of bamboo shoot shell with liquid-phase microplasma assisted technology

In this study, liquid-phase microplasma technology (LPMPT) was employed to facilitate the liquefaction of bamboo shoot shell (BSS) in polyethylene glycol 400 (PEG 400) and ethylene glycol (EG) mixture. Effects of liquefaction conditions such as liquefaction time, catalyst percentage, solvent/BSS mass ratio, PEG/EG volume ratio on liquefaction were investigated experimentally. The results showed that the introduction of LPMPT significantly shortened the liquefaction time to 3min without extra heating. The liquefaction yield reached 96.73% under the optimal conditions. The formation of massive reactive species and instantaneous heat accumulation both contributed to the rapid liquefaction of BSS. Thus, LPMPT could be considered as a simple and efficient method for the assistance of biomass fast liquefaction.

Bio-oil production from eight selected green landscaping wastes through hydrothermal liquefaction

This study investigated the potential of eight types of green landscaping waste as feedstock to produce bio-oil through hydrothermal liquefaction (HTL).

Hydrothermal liquefaction of de-oiled Jatropha curcas cake using Deep Eutectic Solvents (DESs) as catalysts and co-solvents

Biomass liquefaction using ionic liquids (ILs) as catalysts has received appreciable attention, in renewable fuels and chemicals production, recently. However, issues associated with the production cost, long reaction time and use of volatile solvents are undeniably challenging. Thus, Deep Eutectic Solvents (DESs) emerged as promising and potential ILs substitutes. The hydrothermal liquefaction of de-oiled Jatropha curcas cake was catalyzed by four synthesized DESs as catalysts and co-solvents for selective extraction. Proximate and ultimate analyses including ash, moisture and carbon contents of bio-crude produced varied slightly. The higher heating values found ranges from 21.15 ± 0.82 MJ/kg to 24.30 ± 0.98 MJ/kg. The bio-crude yields obtained using ChCl-KOH DES was 43.53 wt% and ChCl-p-TsOH DES was 38.31 wt%. Bio-crude yield using ChCl-FeCl3 DES was 30.80 wt%. It is suggested that, the selectivity of bio-crude could be improved, by using DESs as catalyst and co-solvent in HTL of biomass such as de-oiled J. curcas cake.

Liquefaction of cotton seed in sub-critical water/ethanol with modified medical stone for bio-oil

This study investigated thermal liquefaction of cotton seed in an autoclave. The effects of solvent (ethanol/water, water and ethanol), temperature and some additives on product distribution were investigated. The results showed that using ethanol/water as solvent could get higher total conversion. The highest liquid oil yield (38.4%) was obtained at 300°C, 2MPa and 30min in ethanol/water with Mo/MS (medical stone). The highest hydrogen content in gas also was obtained when adding Mo/MS, and then followed by that when adding Co-Mo/MS. (1)H NMR analysis indicated that the use of additives (except MS) could increase the aliphatic content in liquid oil. (1)H NMR and (13)C NMR showed that the liquefied oil from liquefaction of cotton seed mainly obtained aliphatic compounds, and adding the additives only changed the amount of compounds and did not alter the type of compounds obtained in the oil.